液液萃取固相萃取固相微萃取的比教
Comparative evaluation of liquid–liquid extraction,solid-phase
extraction and solid-phase microextraction for the gas
chromatography–mass spectrometry determination of multiclass
priority organic contaminants in wastewater
JoséRobles-Molina,Bienvenida Gilbert-López,Juan F.García-Reyes,Antonio Molina-Díaz n
Analytical Chemistry Research Group(FQM-323),Department of Physical and Analytical Chemistry,Campus Las Lagunillas,Edif.B3,University of Jaén,
23071Jaén,Spain
a r t i c l e i n f o
Article history:
Received16July2013
Received in revised form
16September2013
Accepted20September2013
Available online25September2013
Keywords:
Wastewater
Sample treatment
Liquid–liquid extraction
Solid-phase extraction
Solid-phase microextraction
Gas chromatography
Mass spectrometry
Water Framework Directive(WFD)
PAHs
Priority compounds
Pesticides
a b s t r a c t
The European Water Framework Directive(WFD)2000/60/EC establishes guidelines to control the
pollution of surface water by sorting out a list of priority substances that involves a signi?cant risk to or
via the aquatic systems.In this article,the analytical performance of three different sample preparation
methodologies for the GC–MS/MS determination of multiclass organic contaminants—including priority
comprounds from the WFD—in wastewater samples using gas chromatography–mass spectrometry was
evaluated.The methodologies tested were:(a)liquid–liquid extraction(LLE)with n-hexane;(b)solid-
phase extraction(SPE)with C18cartridges and elution with ethyl acetate:dichloromethane(1:1(v/v)),
and(c)headspace solid-phase microextraction(HS-SPME)using two different?bers:polyacrylate
and polydimethylsiloxane/carboxen/divinilbenzene.Identi?cation and con?rmation of the selected
57compounds included in the study(comprising polycyclic aromatic hydrocarbons(PAHs),pesticides
and other contaminants)were accomplished using gas chromatography tandem mass spectrometry(GC–
MS/MS)with a triple quadrupole instrument operated in the multiple reaction monitoring(MRM)mode.
Three MS/MS transitions were selected for unambiguous con?rmation of the target chemicals.The
different advantages and pitfalls of each method were discussed.In the case of both LLE and SPE
procedures,the method was validated at two different concentration levels(15and150ng Là1)
obtaining recovery rates in the range70–120%for most of the target compounds.In terms of analyte
coverage,results with HS-SPME were not satisfactory,since14of the compounds tested were not
properly recovered and the overall performance was worse than the other two methods tested.LLE,SPE
and HS-SPME(using polyacrylate?ber)procedures also showed good linearity and https://www.wendangku.net/doc/47483419.html,ing any
of the three methodologies tested,limits of quantitation obtained for most of the detected compounds
were in the low nanogram per liter range.
&2013Elsevier B.V.All rights reserved.
1.Introduction
WFD[1]includes a list of priority compounds to be monitored in
surface water to whom Environmental Quality Standards(EQS)are set
to control their concentration levels[2].Several analytical methodol-
ogies have been reported in the literature for the analysis of priority
organic contaminants compounds in natural water and wastewater
[3].The developed methods are generally based on gas chromato-
graphy–mass spectrometry(GC–MS)rather than liquid chromatogra-
phy–mass spectrometry(LC–MS),because of the physicochemical
properties particularly due to their low polarity and solubility in
water[4].
Despite current trends in sample handling focus on the devel-
opment of faster,safer,and more environmentally friendly extrac-
tion techniques,both(LLE)and solid-phase extraction(SPE)yet
are useful and widely accepted techniques for the exhaustive
extraction of organic contaminants from water matrices[5].
Traditional liquid–liquid extraction does not ful?ll the current
requirements of green analytical chemistry.However,it allows the
application of the procedure to the raw wastewater sample with-
out?ltration,thus offering the possibility to extract organic
contaminants that tend to accumulate in the suspended solids
[6,7].SPE is an alternative less time-consuming and more envir-
onmentally friendly.Hence,it has been widely used for the
determination of organic pollutants in natural waters[8–13].
Contents lists available at ScienceDirect
journal homepage:https://www.wendangku.net/doc/47483419.html,/locate/talanta
Talanta
0039-9140/$-see front matter&2013Elsevier B.V.All rights reserved.
https://www.wendangku.net/doc/47483419.html,/10.1016/j.talanta.2013.09.040
n Corresponding author.Tel.:t34953212147;fax:t34953212940.
E-mail address:amolina@ujaen.es(A.Molina-Díaz).
Talanta117(2013)382–391
The need to?lter sample prior to loading the sample on the SPE cartridge,makes this technique less suitable for the thorough extraction of contaminants from suspended solids.
As an alternative to these two widely accepted sample treat-ment methodologies,solid-phase microextraction(SPME)is also an established technique for volatile compounds and many applications in environmental analysis have been reported,since it is rapid,easily automated,and solvent-free[14–18].Further advanced microextraction techniques described in the literature for trace analysis of organic contaminants in water[19]include stir-bar sorptive extraction[20–23],single-drop microextraction [24–26],dispersive liquid–liquid microextraction[27,28]and membrane assisted microextraction[29,30].However,most of the studies so far are usually devoted to(surface)water samples. Only a little percentage of the abundant literature deals with complex wastewater samples such as untreated in?uents[31].The inherent complexity of this matrix may originate several problems. For instance,SPME must be accomplished in headspace mode instead of by direct immersion of the SPME?ber.In addition,most of the methods developed are usually focused on a selected class of species rather than comprising a vast array of chemicals with different physicochemical properties,which is the preferred situa-tion,so that all the species that are usually included in by water quality regulations could eventually be covered by a single method. For these demanding analytical tasks,LLE,SPE and HS-SPME are yet well established and reliable sample treatment techniques.Finally, wastewater matrices usually contained insoluble particles that retain part of the targeted contaminants,particularly those apolar species with high K ow values.Depending upon the type of technique used, the analytes retained in the suspended particles may produce underestimation errors on the total amount of contaminants.
In this article,the analytical performance of three established sample preparation methodologies for the GC–MS/MS determina-tion of multiclass organic contaminants in wastewater samples using gsa chromatography–mass spectrometry is evaluated.A total of57multiclass organic pollutants(44pesticides and13PAHs), including priority substances from the WFD were examined.The methodologies tested were:(a)LLE with n-hexane;(b)SPE with C18cartridges and elution with ethyl acetate:dichloromethane(1:1 (v/v)),and(c)HS-SPME using two different?bers:polyacrylate (PA)and polydimethylsiloxane/carboxen/divinilbenzene(PDMS/ CAR/DVB).Identi?cation and con?rmation of the selected57 compounds were accomplished using gas chromatography tan-dem mass spectrometry with a triple quadrupole instrument operated in the multiple reaction monitoring mode.
2.Experimental
2.1.Chemical and reagents
The selected multiclass organic contaminants included in this work are shown in Table1,being most of them regulated by WFD (Directive2000/60/CE).All standards were purchased from Sigma-Aldrich(Steinheim,Germany),except procymidone,which was obtained from Dr.Ehrenstofer(Augsburg,Germany).Ethyl acetate, dichloromethane(DCM)and n-hexane were obtained from Riedel-de-H?en(Seelze,Germany).Anhydrous sodium sulfate and sodium chlorine were from J.T.Baker(Deventer,Netherlands).MeOH HPLC grade was from Merck(Darmstadt,Germany)and sulfuric acid was provided by Panreac(Castellar del Vallès,Espa?a).Individual stock standard solutions of the target compounds were prepared at a concentration level of1000mg Là1.These solutions were stored in a freezer atà201C.The working standard solution of multi-compounds was prepared by appropriate dilution of the stock solutions with n-hexane at a concentration level of10mg Là1.SPME ?bers(85μm PA and50/30μm DVB/CAR/PDMS),20mL glass?at-bottomed vials(22.7mm OD?75mm)as well as magnetic PTFE-silicone seals(3.0mm i.d.)were purchased from Supelco(Madrid, Spain).PTFE-encapsulated magnetic stirring bars(6mm?12mm) and SPE Bond Elut C18cartridges(500mg,6mL)were purchased from Varian Inc.(Walnut Creek,California,USA).
2.2.Sample treatment methodologies evaluated
The sample used for the study corresponds to the ef?uent of an urban wastewater sample treatment plant from the south-east of Spain with appropriate spiked amounts of analytes.
2.2.1.LLE procedure for the isolation and preconcentration of organic pollutants
The tested procedure was adapted from a previous work[32]. Samples without?ltration were acidi?ed with H2SO41M up to pH?3were reached.Then250mg of NaCl were added to an aliquot of200mL of wastewater sample,which was subsequently loaded in a250-mL separatory funnel to undergo a three-step LLE. First,25ml of n-hexane were added and the mixture was vigorously shaken for3min being then the organic phase(upper) separated from the aqueous one.Then,this extraction step was repeated two times more.The three organic phases were com-bined and water traces were removed by adding anhydrous sodium sulfate.The extract was then carefully evaporated up to near dryness using a vacuum rotary evaporator(Büchi Rotavapor R200)equipped with a heating bath(Büchi B-490)operating at 341C and a vacuum controller(Büchi V800).Finally,the residue was redissolved in1mL of n-hexane,obtaining a preconcentration factor of200:1.
2.2.2.SPE procedure
The selected procedure was adapted from Pitarch et al.[33]and consisted of passing200mL of?ltered wastewater sample through the C18SPE cartridge previously conditioned by passing6mL methanol,6mL ethyl acetate:DCM(50:50),6mL methanol and 6mL ultrapure water,avoiding dryness.After loading the sample, cartridges were washed with3mL of ultrapure water.The cartridge was dried by passing air,in vacuum for at least15min, and then the elution was performed by passing5mL of the mixture ethyl acetate:DCM(50:50).The extract collected was evaporated under a gentle nitrogen stream using a Turbo Vap LV from Zymark(Hopkinton,MA),with a water bath temperature of 271C and a N2pressure of5psi.Finally,the residue was redis-solved in1mL of n-hexane,obtaining a preconcentration factor of200:1.
2.2.
3.Automated HS-SPME procedure
The?rst step of the analysis consisted of the introduction of 10mL of un?ltered wastewater sample in a20-mL HS glass vial with a PTFE-encapsulated magnetic stirring bar.Then,1mL of MeOH(10%volume)and1g of NaCl were added and the vial was immediately sealed with a PTFE-silicone septum.It was placed in the CombiPAL heated module for heating with mechanical stirring (600rpm)for50min at801C in order to assess the equilibration between gas-phase and sample.During this incubation time,the PA?ber(85μm thickness)was exposed to the headspace of the vial.After the exposition to the analytes,the?ber was automati-cally inserted in the injection port of the GC–MS system for10min (at a desorption temperature of2601C).During GC–MS/MS analysis,speci?c MRM transitions were recorded for each target compound.
J.Robles-Molina et al./Talanta117(2013)382–391383
Table 1
Optimized MS/MS transitions of the target compounds,including retention time,dwell time and collision energy.t R (min)
Window (min)Compounds
Precursor ion (m /z )Product ion (m /z )Type of transition (Q,q 1,q 2)Dwell time (s)Collision energy (eV)7.0 6.5–9.2
1,3,5-TCB
181.8146.8Q 0.04220181.8108.8q 10.04230181.8110.9q 20.042257.81,2,4-TCB
181.8108.8Q 0.04230181.8146.8q 10.04220181.8110.9q 20.042258.3Hexachlorobutadiene
224.9189.8Q 0.04220224.9154.9q 10.04225224.9152.7q 20.042458.41,2,3-TCB
181.8108.8Q 0.04230181.8146.8q 10.04220181.8110.9q 20.042258.6Isoproturon
161.1146.1Q 0.04210161.1128.0q 10.04220161.191.0q 20.042308.7Chlorlotoluron
167.0132.0Q 0.04210167.077.0q 10.04230167.0104.0q 20.042209.89.2–10.5Diuron
186.9123.9Q 0.16720186.9158.8q 10.16710186.996.8q 20.1673511.910.5–12.2Acenaphthylene 152.0152.1Q 0.10010152.0151.1q 10.1001512.6
12.2–14.0
Pentachlorobenzene
249.8214.8Q 0.10020249.8142.0q 10.10040249.8107.8q 20.1005013.7Fluorene 166.0165.1Q 0.10010166.0166.0q 10.1001014.6
14.0–15.1
Tri ?uralin
306.1264.0Q 0.08310306.1206.0q 10.08315306.1159.8q 20.0832514.7Atrazine desethyl
172.0105.0Q 0.08310187.0172.1q 10.08310172.094.0q 20.0831515.515.1–16.0α-HCH
218.9182.8Q 0.08310218.9146.9q 10.08325218.9108.8q 20.0833515.6Hexachlorobenzene
283.8248.7Q 0.08320283.8141.8q 10.08350283.8178.7q 20.0835016.316.0–17.4Simazine
201.0173.0Q 0.03310201.0186.1q 10.03310201.0138.0q 20.0331516.5Atrazine
215.157.9Q 0.03310215.1200.1q 10.03310215.1138.1q 20.0331516.6Propazine
229.058.0Q 0.03315229.0187.1q 10.03310229.0214.1q 20.0331016.8β-HCH
218.9182.8Q 0.03310218.9144.8q 10.03325218.9108.9q 20.0333516.9γ-HCH
218.9182.8Q 0.03310218.9144.8q 10.03325218.9108.9q 20.0333517.1Terbuthylazine
214.1132.0Q 0.03310214.1136.0q 10.03310214.1119.0q 20.0331017.3Diazinon
304.0179.1Q 0.03315179.0137.0q 10.03315179.0122.0q 20.0332517.717.4–18.2Phenantrene 178.0178.1Q 0.25010178.0152.1q 10.2501517.9Anthracene
178.0178.1Q 0.25010178.0152.1q 10.2501518.6
18.2–19.5δ-HCH
218.9182.8Q 0.16710218.9144.8q 10.16725218.9108.9q 20.1673520.119.5–20.8Alachlor
188.1160.0Q 0.05010188.1131.0q 10.05020188.1132.0q 20.0501520.1Parathion methyl
263.0109.11Q 0.05010263.0127.1q 10.05010263.0
246.0
q 2
0.050
5
J.Robles-Molina et al./Talanta 117(2013)382–391
384
Table1(continued)
t R(min)Window
(min)Compounds Precursor
ion(m/z)
Product
ion(m/z)
Type of transition
(Q,q1,q2)
Dwell
time(s)
Collision energy
(eV)
20.4Heptachlor272.0237.0Q0.05015
272.0272.1q10.0505
272.0143.0q20.05035
20.5Ametryn227.0185.1Q0.05010
227.0212.1q10.05010
227.058.0q20.05010
21.220.8–21.5Terbutryn241.1185.1Q0.16710
241.1170.0q10.16715
241.1111.2q20.16725
21.921.5–22.7Chlorpyrifos ethyl314.0258.0Q0.05615
314.0286.0q10.05610
314.0314.0q20.0565
21.9Aldrin262.8192.7Q0.05630
262.8190.8q10.05635
262.8228.0q20.05620
22.3Parathion ethyl291.0109.0Q0.05610
291.081.0q10.05630
291.0142.0q20.0565
23.122.7–24.5Isodrin262.8192.7Q0.05630
262.8190.8q10.05630
262.8228.0q20.05620
23.3Chlorfenvinphos A323.0267.0Q0.05610
323.0295.0q10.05610
323.0159.0q20.05630
23.7Chlorfenvinphos B323.0267.0Q0.05610
323.0295.0q10.05610
323.0159.0q20.05630
24.1Procymidone283.095.5Q0.05610
283.067.0q10.05620
283.0255.1q20.05610
25.024.5–26.4Pyrene202.1202.0Q0.03710
202.1201.2q10.03710
25.0α-endosulfan338.8160.1Q0.03715
338.8194.9q10.03710
338.8230.9q20.03710
25.94,4′-DDE318.0246.0Q0.03715
318.0248.0q10.03710
318.0283.0q20.03710
26.0Dieldrin262.8192.7Q0.03730
262.8190.8q10.03735
262.8227.9q20.03715
26.1Oxy?uorfen361.0300.0Q0.03710
361.0317.0q10.03710
361.0252.0q20.03715
26.826.4–28.8Endrin262.8192.7Q0.03335
262.8190.8q10.03335
262.8228.0q20.03320
27.2β-endosulfan338.8266.7Q0.03310
338.8160.0q10.03315
338.8230.8q20.03310
27.3Ethion231.0129.0Q0.03325
231.0157.0q10.03315
231.0185.0q20.03310
28.5Endosulfan sulfate386.8252.9Q0.03310
386.8288.9q10.03310
386.8205.7q20.03335
28.64,4′-DDT235.0164.9Q0.03325
235.0200.0q10.03310
235.0199.0q20.03315
30.028.8–30.7Iprodione314.0245.0Q0.06210
314.0271.0q10.06210
314.055.9q20.06220
30.3Benzo(a)anthracene228.0228.0Q0.06210
228.0226.0q10.06225
30.5Chrysene228.0228.0Q0.06210
228.0226.0q10.06225
30.5Metoxychlor227.0169.0Q0.06225
227.0212.1q10.06210
227.0184.0q20.06215
34.730.7–37.5Benzo(b)?uoranthene252.0252.0Q0.25010
252.0250.0q10.25030
34.8Benzo(k)?uoranthene252.0252.0Q0.25010
252.0252.0q10.25030
36.0Benzo(a)pyrene252.0252.0Q0.25010
252.0252.0q10.25030
J.Robles-Molina et al./Talanta117(2013)382–391385
2.3.GC –MS/MS conditions
2.3.1.Gas chromatography
Determination was performed using a CP-3800gas chromato-graph (Varian Inc.Walnut Creek,California,USA)equipped with electronic ?ow control (EFC)and a 1079universal capillary injector that allows programmed temperature injection (a PTV injection port).The gas chromatograph was also equipped with an auto-sampler (CombiPAL autosampler,CTC Analytics)with capacity for 982-mL vials and a robotic arm.The injector temperature was held at 2801C for 2min during injection,then programmed at 401C min à1to 3251C,which was held for 10min.Separations were performed on a Varian FactorFour Capillary Column VF-5ms analytical column (30m ?0.25mm i.d.?0.25m m ?lm thickness).Helium (99.9999%)was used as a carrier gas at a ?ow rate of 1.0mL min à1.The oven temperature was programmed as follows:701C (held 2min);101C min à1to 1801C (5min);6.01C min à1to 2601C;and 41C min à1to 3001C (2min).Sample extracts obtained after LLE or SPE sample treatments were injected (4m L)using a Frit gooseneck liner (Restek,Bellefonte,USA).
2.3.2.Gas chromatography conditions for automated HS-SPME analysis
The gas chromatograph described in Section 2.3.1was also equipped with an autosampler (CombiPAL autosampler,CTC Ana-lytics)with capacity for 3220-mL headspace vials composed of an oven for sample heating/headspace generation and a robotic arm where the headspace syringe was placed.For the ?ber injection a split open deactivated insert liner of 5mm OD ?54mm ?3.4mm ID (Varian Inc.,Walnut Creek,California,USA)was placed inside the GC injection port.The column oven temperature program is described in Section 2.3.1.
2.3.3.Mass spectrometry
The GC was interfaced with a model 300-MS triple quadrupole mass spectrometer (Varian Inc.Walnut Creek,California,USA)operating in an electron ionization mode (EI,70eV).A ?lament current of 50m A and a multiplier voltage of 1300V were used in MS/MS mode.The temperatures of the transfer line,ion source and manifold were set at 2801C,2501C and 401C,respectively.A ?lament multiplier delay of 6.4min was ?xed in order to prevent instrument damages.The mass spectrometer was calibrated as needed with per ?uorotributylamine (PFTBA).For the MS/MS experiments Ar was used as a collision gas and the collision cell pressure was set at 1.80mTorr.Multiple reaction monitoring (MRM)conditions were experimentally developed for each indi-vidual pesticide on the instrument used in this work.Precursor and product ions,collision energies and other parameters used are shown in Table 1.For instrument control,data acquisition and evaluation Varian MS Workstation,version 6.9was used.
2.4.Optimization of MS/MS method
To set the MRM method,precursor ions,product ions,and collision energy were studied for each individual analyte.The most intense transition was used as quanti ?er (Q),while the other transition(s)was used as quali ?er (q)peak(s)for the con ?rmatory analysis.Precursor and product ions,collision energies and other parameters used in the developed GC –MS/MS method are shown in Table 1.Three MRM transitions were used for pesticides,while for PAHs only two transitions were selected due to their dif ?culty to yield useful fragmentation.For atrazine desethyl and diazinon the selected precursor ions for quanti ?er and quali ?er transitions were different.
To con ?rm peak identity in samples,retention time and the Q/q ratio criterion were used,de ?ned as the ratio between the intensity of the quanti ?cation transition (Q)and the con ?rmation transitions (q 1and q 2).Firstly,the theoretical averages Q/q 1and Q/q 2for each compound (only one ration available for PAHs)were calculated as the mean value obtained from the chromatographic analysis of standard solutions.The identity of a peak was con ?rmed by comparison of the experimental ratio in the sample with the theoretical ratio of the reference standard,considering the percen-tage of variability (tolerance)established in the Decision 2002/657/EC [34],based on ion-ratio statistics for the transitions monitored.As an example,Fig.1shows the identi ?cation of hexachlorobenzene in a wastewater sample spiked at a concentration level of 50ng L à1for the different sample treatment methods tested.
3.Results and discussion
3.1.Evaluation of the selected extraction procedures
The three sample treatment methodologies tested were:(a)LLE with n-hexane;(b)SPE with C 18cartridges and elution with ethyl acetate:dichloromethane (1:1(v/v)),and (c)HS-SPME using two different ?bers:PA and (DVB/CAR/PDMS).The comparative study is summarized in Table 2.
3.1.1.Method scope
The main goal of the proposed study was to evaluate which of these three methodologies was more convenient for the large-scale testing of multiclass organic contaminants in wastewater samples.First,it should be noted that wastewater in ?uents are usually composed by two phases:aqueous phase and suspended solids.A relevant aspect to consider in an extraction method is the ability to extract contaminants from both the whole water,not only the dissolved fraction but also the suspended solids fraction.However,most of the analytical methods described in the litera-ture for the analysis of organic contaminants in wastewater rely on the examination of the aqueous phase obtained after sample
Table 1(continued )t R (min)
Window (min)Compounds
Precursor ion (m /z )Product ion (m /z )Type of transition (Q,q 1,q 2)Dwell time (s)Collision energy (eV)38.437.5–39.5
Deltamethrin
252.993.0Q 0.16720252.9174.0q 10.16710252.990.9q 20.1672540.439.5–43.3Indene(1,2,3-cd)pyrene 276.0276.0Q 0.12510276.0274.0q 10.1254040.5Dibenzo(a,h)anthracene 278.0278.0Q 0.12510278.0250.0q 10.1254541.3
Benzo(g,h,i)perylene
276.0276.0Q 0.12510276.0
274.0
q 1
0.125
40
J.Robles-Molina et al./Talanta 117(2013)382–391
386
?ltration,disregarding thus the solid particles retained on the ?lters[35].Depending on the physicochemical properties of the analytes(water solubility,octanol/water partition coef?cient (log K o/w)),each analyte exhibits a speci?c partitioning behavior between the two phases.This fact made clear the relevance of the analysis of both phases in wastewater samples.Otherwise,an important contribution of selected contaminants may be under-estimated.According to the current regulations(EQS)[2],solid suspended particles should be considered since the whole water (dissolvedtsuspended solids bound fraction)must be included in the analyses.
In this sense,while LLE with solvent(hexane)permits the thorough extraction of the entire water sample(including solid suspended material),SPE usually requires a?ltration prior to sample load in order to prevent clogging of cartridge,this fact being particularly important for high preconcentration factors or with complex matrices.Thus,part of the contaminants present in waste-water may be underestimated.In the case of HS-SPME,due to the complexity of the matrix and because of the suspended particulate solids,the method of choice must be HS-SPME instead of direct immersion SPME.This means that the entire un?ltered sample is subjected to analyses.In contrast,the use of HS-SPME probably along with the low volatility and behavior according to Henry's law of selected analytes offers severe drawback in terms of analyte coverage(14of the studied compounds could not be recovered and detected).Given these data,HS-SPME was found as less versatile or at least not suited to cover such a wide variety of chemicals.
From the point of view of analyte coverage,both LLE and SPE are de?nitely more versatile than HS-SPME.Either with the choice of an apolar solvent(such as hexane)or a combination of two solvents to tune the extraction towards more polar compounds are effective and straightforward approaches.On the other hand,SPE with C18and a careful selection of eluting solvents enabled similar recovery rates that LLE,but with the clear advantages of higher automation and lower solvent consumption.The main drawback associated with SPE is the limitation related to solid particles and the need of?ltering the sample,which makes that part of the contaminants present in wastewater may be underestimated.
With regards to HS-SPME method,the choice of?ber was done considering that different chemical classes should be analyzed within a run.Under optimized values for HS-SPME variables (sample volume,heating temperature,incubation time,magnetic stirring rate,desorption time and the addition of modi?ers were studied),higher signals were obtained in most cases using PA?ber. In addition,PAHs and organochlorine pesticides were strongly retained in the DVB/CAR/PDMS?ber,causing carry-over/memory effects,cross-contamination and reducing the lifetime of the?ber. Therefore,PA?ber was selected as optimum for the target analysis of this application.The main advantages of HS-SPME are the low consumption of organic solvents(only1mL of MeOH used as additive in each sample)and the low required volume of sample (10mL instead of200mL for either LLE or SPE).The main disadvantage compared to the other studied methodologies is the limited number of species detected.Fourteen compounds were not conveniently detected:alachlor,ametryn,atrazine,atrazine desethyl,chlorotoluron,deltamethrin,endosulfan sulfate,hepta-chlor,iprodione,isoproturon,parathion methyl,propazine,sima-zine,and terbutryn.In contrast,all target compounds were effectively extracted using either LLE or SPE,and consequently detected by GC–MS/MS.
3.1.2.Extraction ef?ciency:recovery rates
To evaluate the effectiveness of the extraction using the studied LLE and SPE extraction procedures,recovery studies(n?6)were carried out after spiking wastewater samples at two concentration levels,15and150ng Là1.Results are detailed in Table2,showing that both LLE and SPE in general showed similar results.At both concentration levels tested,about60%of the studied analytes
Fig.1.Identi?cation of hexachlorobenzene by GC–MS/MS in a wastewater sample
spiked at a concentration level of50ng Là1(a)after LLE with n-hexane;(b)after
the application of the proposed SPE procedure;and(c)HS-SPME analysis.
J.Robles-Molina et al./Talanta117(2013)382–391387
showed recoveries in the range 70–120%,and over 85%of the studied analytes showed recoveries at least of 50%(see Fig.2).However,if the discussion is focused on the results by chemical class (see Table 3),it is possible to notice that a proper extraction process choice make the difference.
It is clear that SPE is the extraction process of choice for the triazine group,it showed recoveries above 90%for all compounds in both forti ?cation levels.In contrast,four out of seven triazines gave recovery values below 60%when LLE process was applied.The extraction of these compounds is not affected by the ?ltration of the sample,but by the more polar solvents employed in SPE process.Similar behavior showed the phenylurea pesticides,with poor recoveries in all cases when LLE process is used.Regarding PAH compounds,at the lowest forti ?cation level,LLE process presented in all cases better results than SPE.While recoveries values are very similar (slightly better for LLE)when comparing results at the highest forti ?cation level.This behavior suggests that part of the PAHs is bonded to the suspended solid and this fact is of more importance at low concentration levels.Similar conclusion can be achieved for OCP,with better results for LLE at the lowest forti ?cation level for most compounds,with recovery values
below 70%for almost all of them.While slight differences are observed at the highest forti ?cation level among both extraction processes.In the case of OPP good recovery rates (above 70%in most cases)are obtained with both extraction processes.
In the case of HS-SPME,the study was performed at 25ng L à1(n ?3).In this case,mean recoveries ranging between 73%and 119%were obtained for the (43)detected analytes.However,it should be emphasized that in this type of microextraxtion techniques only a fraction of the analytes contained in the sample is recovered.SPME is a non-exhaustive extraction technique unlike SPE or LLE.For this reason,relative recoveries (using spiked-water standards as reference)were used instead for HS-SPME,since absolute recoveries are more appropriately used for exhaustive extraction techniques.
3.1.3.Automation,solvent consumption and waste generation
As included in Table 2,from the point of view of solvent consumption and waste generation,HS-SPME offers clear advan-tages against both SPE and LLE as being the more environmentally friendly approach [36],using only 1mL of MeOH as chemical
Table 2
Comparative study of sample treatment methodologies for the determination of 57organic pollutants by GC –MS/MS.
LLE
SPE HS-SPME (PA ?ber results)Number of measurable compounds 575743Treatment tanalysis time per sample (min)
C 75C 55
C 60a
Suspended particulate matter subject to analysis?
Yes
Not (unless processing un ?ltered wastewater samples)
Yes (although only for relatively volatile species)Solvents,consumed per sample 76mL n-hexane 12mL MeOH;14mL EtAc tDCM (1:1)1mL MeOH LOQs (ng L à1)
0.03–5.100.03–5.000.10–150.00Accuracy (recovery rates)(%)70–11070–120
73–119Precision (RSD %)3–15
1–10in most cases
7–20
Linearity (R 2)
1–500ng L à1(at least 0.999for most compounds)
1–500ng L à1(at least 0.999for most compounds)
5–50ng L à1(at least 0.991for most compounds)
EtAc:ethyl acetate and DCM:dichloromethane.
a
Overlapped mode:injection of sample “n ”ttime incubation of sample “n t1”.
79%
12%
5%4%Liquid-Liquid Extraction (15 ng L -1)
>70 %
50-70 %
30-50 %
<30 %
53%
30%
12%
5%
Liquid-Liquid Extraction (150 ng L -1)
>70 %
50-70 %
30-50 %
<30 %
53%
17%
18%
12%
Solid-Phase Extraction (15 ng L -1)
>70 %
50-70 %
30-50 %
<30 %
63%
14%
18%
5%
Solid-Phase Extraction (150 ng L -1)
>70 %
50-70 %
30-50 %
<30 %
https://www.wendangku.net/doc/47483419.html,parison between recovery studies obtained by LLE and SPE methods at both 15and 150ng/L spiking levels.
J.Robles-Molina et al./Talanta 117(2013)382–391
388
modi?er.The solvent consumption is negligible compared to SPE and especially to LLE.In the two latter techniques,the selected sample volume was200mL.Considering a preconcentration factor of200:1,the?nal volume of the extract is1mL.Working with lower volumes(e.g.0.5mL with100mL of loaded sample)was discarded because some of the matrices obtained were so complex that sometimes emulsions were obtained and a dedicated?ltra-tion of the?nal extracts through membrane?lters was necessary. The use of SPE involves34%reduction in organic solvent consumption compared to LLE,and is less time-consuming than
Table3
Recovery studies of LLE(n?6),SPE(n?6)and HS-SPME(n?3)methods.
Compounds Chem.class b LLE SPE HS-SPME
Forti?cation levels(ng Là1)and RSD(%)Forti?cation levels(ng Là1)and RSD(%)Forti?cation
level(ng Là1)and RSD(%)
15RSD(%)150RSD(%)15RSD(%)150RSD(%)25RSD(%)
Ametryn TrzP47.219.433.511.69013.393 4.9––
Atrazine TrzP74.5 6.153.99.7108 3.91008.2––
Atrazine desethyl TrzP52.11744.419.6950.3117 5.8––
Propazine TrzP120.1382.17.3946101 5.8––
Simazine TrzP––25.215.4––949.9––Terbuthylazine TrzP139 3.888.89.29391038.686.25a 4.32
Terbutryn TrzP104.2 5.189.115.49714.394 5.6––Chlorotoluron PhUP54.97.32017.5987.5120 3.6––
Diuron PhUP5412.617.521.18513.1130 5.183.0614.89 Isoproturon PhUP428.529.813.897 6.9118 2.7––
Deltamethrin PEP––32.122.45014.154 4.8––Chlorfenvinphos A OPP154.38.768.88.499711811.779.7512.26 Chlorfenvinphos B OPP100.1 5.796.69.4986107 2.773.32 2.08 Chloropyrifos ethyl OPP104.616.473.818.17311.3749118.68 6.72
Diazinon OPP112 5.290.510.48912.7889.2123.82 5.38
Ethion OPP74.5 4.866.622.67010778.3100.84 3.09
Parathion ethyl OPP112.4 5.1100.98.41129.8100 2.689.0412.55 Parathion methyl OPP101.7 3.7102.410.17915.397 5.7––
Aldrin OCP102.17.362.117.83714.43014.3102.579.42
4,4′-DDE OCP103.7 6.969.419.236 6.34711.6105.817.8
4,4′-DDT OCP93.99.369.418.548 5.9687.2102.86 6.89
Dieldrin OCP88.88.276.37.1487.970 6.1100.93 4.76
α-Endosulfan OCP175.17.585.68.7––747.298.71 6.94
β-Endosulfan OCP119.88.875.69.989 6.28221.591.357.5
Endosulfan sulfate OCP111.3669.218.21109.896 6.6––
Endrin OCP98.913.781.111.67510828.397.388.83 Heptachlor OCP115 5.767.111.6491537 6.3––
Hexachloro-1,3-butadiene OCP5215.331.61916 6.31814104.07 1.39 Hexachlorobenzene OCP96.5 3.173.912.4409.44013.7107.98 4.55
α-HCH OCP107 5.893 5.27178110.4101.19 1.74
β-HCH OCP164.17.8112.714.8997.41208.199.758.56
γ-HCH OCP133.8 3.793.713908.7919.995.5313.92
δ-HCH OCP94.910.8101.212.380 1.8918.693.25a8.65
Isodrin OCP103.9 5.27312.53811.4398.8101.877.13 Metoxychlor OCP94.2 1.478.917.674789 6.1100.04 5.28 Pentachlorobenzene OCP105.47.172.99.230 1.63610.8106.46 2.08
1,2,3-TCB OCP76.110.952.59.927103316.3102.34 4.34
1,2,4-TCB OCP88.29.945.89.53010.22710.9104.27 3.55
1,3,5-TCB OCP77.38.14315.626 6.42015.5116.29 4.17
Oxy?uorfen NPhEP142.37.490.118111 3.1889.682.358.13
Tri?uralin DnaP102.6 4.682.7157 6.6577.7101.398.38
Iprodione DcDP51.713.956.57.710013.6120 6.1––Procymidone DcDP125.4584.49.1768.593 5.795.62 5.36
Alachlor ChaP136.6 2.792.712.2828969.7––Acenaphtylene PAH102 4.188.2 6.7398.5509.5103.520.18 Anthracene PAH140.7 3.784.37.9637.870 6.1101.07 5.91
Benzo(a)anthracene PAH85.37.462.216.264 6.377 5.5105.1 1.29
Benzo(a)pyrene PAH71.37.457.615.459 6.253 4.1107.23 5.89
Benzo(b)?uoranthene PAH61.67.464.420.4581166 5.593.347.38
Benzo(ghi)perylene PAH132.4 1.652.1 6.85415.149 4.5100.89 6.68
Benzo(k)?uoranthene PAH637.163.714.64514.563 5.398.49 2.3
Chrysene PAH98.9 6.186.513.56010.175 4.6105.310.98
Dibenzo(a,h)anthracene PAH76.8 4.154.511.95018.148 4.197.517.94
Fluorene PAH123.4379.412.84812.8579.1106.070.97
Indene(1,2,3-cd)pyrene PAH75.7 4.85411.663 3.646 2.8105.0718.09 Phenanthrene PAH108.1 5.874.914.170 6.57110.3111.327.19
Pyrene PAH4320.270.913.47311.2758.9104.21 4.89
a Terbuthylazine andδ-HCH were spiked at a concentration level of150ng Là1(n?3),instead of25ng Là1.
b Description of the acronyms:TrzP—Triazines pesticides,PhuP—Phenylureas pesticides,PEP—Pyrethroid ester pesticides,OPP—Organophosphate pesticides, OCP—Organochlorine pesticides,NPhEP—Nitrophenyl ether pesticides,DnaP—Dinitroanilyne pesticides,DnaP—Dinitroaniline pesticides,DcDP—Dichlorophenyl dicarbox-imides pesticides,ChAP—Chloroacetanilide pesticides,and PAH—Polycycli
c aromatic hydrocarbon.
J.Robles-Molina et al./Talanta117(2013)382–391389
both LLE and HS-SPME.Finally,the sensitivity offered by both LLE and SPE is pretty similar (36analytes showed LOQs below 1ng L à1in the case of SPE,while 32analytes showed LOQs below 1ng L à1in the case of LLE).
3.2.Analytical performance of GC –MS/MS methods
The linearity of the calibration curves was studied using matrix-matched standard solutions containing the target compounds at six concentration levels in the range from 1to 500ng L à1.The
response was found to be linear with a regression coef ?cient (R 2)higher than 0.999in the range tested for most of studied organic pollutants when either LLE or SPE procedures were used.In the case of HS-SPME,results were not as satisfactory with calibration curves only linear in the range 5–50ng L à1for most of studied com-pounds,although several analytes were linear up to 150ng L à1,obtaining values of at least 0.991for regression coef ?cients.
Limit of quantitation (LOQ)was estimated as the analyte concentration that produces a peak signal of 10times the back-ground noise from the chromatogram at the lowest calibration level as low as it was possible using the q 2transition.The proposed method showed LOQs in the low ng L à1range,although the results were better for both SPE and LLE when compared with HS-SPME.Results are detailed in Table 4.In terms of sensitivity,LLE is similar to SPE,obtaining LOQs in the range 0.03–5.00ng L à1for both methodologies.However,14compounds were not effec-tively detected by HS-SPME.The main reasons are their low volatility and af ?nity towards the selected SPME ?ber.For the rest of compounds detected,HS-SPME offered LOQs in the range 0.1–25ng L à1,except for terbuthylazine and δ-HCH,which showed LOQ of 150ng L à1.
A precision study was carried out by calculating the relative standard deviation (RSD)from the analysis of six replicates of forti ?ed wastewater at 15and 150ng L à1concentration levels for LLE and SPE.Nevertheless,in HS-SPME,25ng L à1(three repli-cates)was the selected level for HS-SPME because all extractable compounds,except terbuthylazine and δ-HCH,could be measured at this level.No higher concentration was chosen for this method,due to the lack of linearity for most compounds beyond 150ng L à1.Relative standard deviation values were in most cases in the range 3–15%when LLE was used,while using SPE procedure RSD (%)was ranging 1–10%and values between 7and 15%were found when HS-SPME methodology was applied (Table 3).
4.Conclusions
In the present work,three sample treatment methodologies have been evaluated and compared for analysis by GC –MS/MS of organic pollutants included in the list of priority substances of WFD.LLE with n-hexane and SPE using with C 18cartridges and ethyl acetate:dichloromethane (1:1(v/v))as eluent showed recov-eries in the range 70–120%for the majority of the studied compounds.Linearity and precision were evaluated,obtaining satisfactory results for all the three sample treatment methodo-logies tested.The limits of quantitation obtained for most of the target compounds were in the low nanogram per litre range,using any of the three procedures tested.LLE and SPE were revealed as the most sensitive methods,but SPE is less time consuming and more environmentally friendly than LLE in terms of solvent consumption,although species that may be retained in suspended solids would be out of the scope of the method.Nevertheless,it has been demonstrated that depending on the chemical class,the treatment sample process of choice would be either SPE or LLE.
Acknowledgments
The authors acknowledge the funding support from Regional Government of Andalusia (Spain)Junta de Andalucía (Research Group FQM-323)and from the National Spanish Ministerio de Educación y Ciencia (Project CSD2006–00044CONSOLIDER INGE-NIO 2010“TRAGUA project ”entitled Treatment and Reuse of Wastewaters for Sustainable Management).
Table 4
Limits of quantitation for the determination of 57organic pollutants by GC –MS/MS using the three studied sample treatment https://www.wendangku.net/doc/47483419.html,pound
LOQ (ng L à1)LLE
SPE HS-SPME Acenaphtylene 0.20.3 5.0Alachlor 2.7 2.6–Aldrin 0.30.2 5.0Ametryn 2.7 2.7–Anthracene
1.0 1.024.8Atrazine desethyl 1.2 1.4–Atrazine
4.5 2.5–Benzo(a)anthracene 0.70.224.8Benzo(a)pyrene
0.20.424.8Benzo(b)?uoranthene 0.60.324.8Benzo(ghi)perylene 0.40.3 5.0Benzo(k)?uoranthene 0.30.224.8Chlorfenvinfos A 2.2 2.4 2.6Chlorfenvinfos B 3.2 2.714.9Chloropyrifos ethyl 0.90.80.7Chlorotoluron 1.3 2.6–Chrysene 1.60.224.8Deltamethrin 2.8 4.1–Diazinon
0.030.030.1Dibenzo(a,h)anthracene 3.40.5 5.04,4′-DDE 1.10.324.84,4′-DDT 0.60.6 5.0Dieldrin 0.4 5.0 5.0Diuron
0.30.324.8α-Endosulfan 0.999.024.8β-Endosulfan
0.39.924.8Endosulfan sulfate 0.80.2–Endrin 5.0 4.1 5.0Ethion 5.00.6 1.0Fluorene 0.20.2 5.0Heptachlor
0.030.03–Hexachloro-1,3-butadiene 0.30.7 1.0Hexachlorobenzene 0.20.4 5.0α-HCH 0.30.3 1.0β-HCH 0.50.8 5.0γ-HCH 0.40.6 5.0δ-HCH
0.40.6148.5Indene(1,2,3-cd)pyrene 0.40.3 5.0Iprodione 0.2 1.5–Isodrin
2.0 2.724.8Isoproturon 2.2 2.7–Metoxychlor 0.20.6 5.0Oxy ?uorfen 0.40.00.7Parathion ethyl 2.7
3.12
4.8Parathion methyl 2.5 2.5–Pentachlorobenzene 0.030.1
5.0Phenanthrene 0.90.724.8Procymidone 3.00.424.8Propazine 3.2 2.1–Pyrene 0.40.624.8Simazine
5.1 5.1–Terbuthylazine 2.0 1.1148.5Terbutryn 1.4 1.4–1,2,3-TCB 1.7 1.9 5.01,2,4-TCB 2.2 2.7 5.01,3,5,TCB 1.8 2.7 5.0Tri ?uralin
0.2
0.2
0.7
J.Robles-Molina et al./Talanta 117(2013)382–391
390
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J.Robles-Molina et al./Talanta117(2013)382–391391
固相萃取与固相微萃取应用之原理
固相萃取与固相微萃取应用之原理 一固相萃取 固相萃取（Solid Phase Extraction，SPE）是一种基于液-固分离萃取的试样预处理技术，由柱液相色谱技术发展而来。SPE技术自70年代后期问世以来，由于其高效、可靠及耗用溶剂量少等优点，在环境等许多领域得到了快速发展。在国外已逐渐取代传统的液-液萃取而成为样品预处理的可靠而有效的方法。 SPE技术基于液相色谱的原理，可近似看作一个简单的色谱过程。吸附剂作为固定相，而流动相是萃取过程中的水样。当流动相与固定相接触时，其中的某些痕量物质（目标物）就保留在固定相中。这时用少量的选择性溶剂洗脱，即可得到富集和纯化的目标物。固相萃取可分为在线萃取线萃取前者萃取与色谱分析同步完成；而后者萃取与色谱分析分步完成，两者在原理上是一致的。 一般固相萃取的操作步骤包括固相萃取柱（即吸附剂）的选择、柱子预处理、上样、淋洗、洗脱。在实验过程中需要具体考虑的因素如下： 1）吸附剂的选择 a.传统吸附剂 在环境分析中最为常用的反相吸附剂较适用于水样中的非极性到中等极性的有机物的富集和纯化。其中有代表性的键合硅胶C18和键合硅胶C8等。该类吸附剂主要通过目标物的碳氢键同硅胶表面的官能团产生非极性的范德华力或色散力来保留目标物。 正相吸附剂包括硅酸镁、氨基、氰基、双醇基键合硅胶及氧化铝等，主要通过目标物的极性官能团与吸附剂表面的极性官能团的极性相互作用（氢键作用等）来保留溶于非极性介质的极性化合物。由于其特殊的作用原理，在环境分析中常用于与其它类型的吸附柱联用，吸附去除干扰物，实现样品纯化。 离子交换吸附剂则主要包括强阳离子和强阴离子交换树脂，这些树脂的骨架通常为苯乙烯-二乙烯基苯共聚物，主要是通过目标物的带电荷基团与键合硅胶上的带电荷基团相互静电吸引实现吸附的。 b.抗体键合吸附剂（Immunosorbents-IS） 这类新型吸附剂充分利用了生物免疫抗原-抗体之间的高灵敏性和高选择性，尤其适应于水中痕量有机物的富集与分离。其特点为，由于绝大多数有机污染物为低分子量物质，不能在动物体内引发免疫反应，所以需把待定污染物键合到牛血清白蛋白的生物大分子载体上，使其具有免疫抗原活性，再注入纯种动物体内（如兔或羊），产生抗体，经杂交瘤技术制得相应于该有机污染物的单克隆抗体。将抗体键合到反相吸附剂的硅胶表面或聚合物表面（如C18固定相），就制得了抗体键合吸附剂，可用于分离、富集特定污染物。研制开发能专门检测各种优先污染物的单克隆抗体或多克隆抗体已成为SPE技术的前沿研究领域。 抗体键合吸附剂洗脱时一般可采用20%～80%的甲醇-水溶液，该类吸附剂经冷藏保存可多次使用。进行SPE操作时应根据目标物的性质选择适合的吸附剂。表1- 1给除了常用的吸附剂类型及其相关的分离机理、洗脱剂性质和待测组分的性质。 吸附剂的用量与目标物性质（极性、挥发性）及其在水样中的浓度直接相关。通常，增加吸附剂用量可以增加对目标物的保留，可通过绘制吸附曲线确定吸附剂用量。 2）柱子预处理 活化的目的是创造一个与样品溶剂相容的环境并去除柱内所以杂质。通常需要两种溶剂来完成任务，第一个溶剂（初溶剂）用于净化固定相，另一个溶剂（终溶剂）用于建立一个适合的固定相环境使样品分析物得到适当的保留。每一活化溶剂用量约为1～2 mL/100 mg固定相。
顶空固相微萃取-气相色谱-质谱联用
顶空固相微萃取-气相色谱-质谱联用 分析纺织品中挥发性有机物* 蔡积进张卓旻李攻科 中山大学化学与化学工程学院，广东，广州 510275 摘要本文以顶空固相微萃取(Head Space Solid Phase Microextraction,HSSPME)和 气相色谱-质谱(GC/MS)联用技术分析纺织品中的五种常见挥发性有机物（Volatile Organic Compounds,VOCs）：甲苯、4-乙烯基环己烯、苯乙烯、萘和1-苯基环己烯。 优化了顶空体积、平衡时间、萃取时间、萃取温度、搅拌速率、加盐种类和浓度以及GC/MS条件。建立了快速测定纺织品中VOCs的方法，方法对五种待测物质均具有较宽线性范围，分别为0.087～870，3.32～3320，2.28～2280，0.015～150和0.5～500 ng/g；检出限分别为0.005、0.042、0.67、0.008和0.011 ng/g。分析加标实际样品，回收率在80.1～122％之间，RSD在0.8～8.6％之间。方法符合纺织品中痕量VOCs 的快速分析要求。 关键词：固相微萃取；气相色谱-质谱；纺织品；挥发性有机物 生态纺织品标准100(Oeko-Tex Standard 100)[1]是纺织品领域通行的技术标准,严格规定了残留有毒、有害VOCs的释放量。为推动纺织品质量达到出口标准，需建立有效快速的VOCs 检测方法。由于纺织品VOCs的含量很低，常规的预富集浓缩方法很难满足分析需要，达不到相应的灵敏度要求。SPME是八十年代末Pawliszyn等[2]研制开发的一种非溶剂分析萃取技术，具有操作简单、萃取速度快、选择性和适应性好等优点。而HSSPME应用于纺织品中，一方面继承了顶空技术操作简单、不受样品基体干扰的优点；另一方面又能在采样的同时进行浓缩，大大提高了分析灵敏度。国内已有学者用SPME技术对纺织品中残留干洗溶剂（如四氯乙烯和三氯乙烯等）和驱虫剂（如二氯苯和萘等）进行分析[3～5]。本文建立了HSSPME-GC-MS联用分析纺织品中常见VOCs的分析方法，方法灵敏度高，重现性好，适合于纺织品中多种痕量挥发性有机物的分析。 1 实验 1.1 仪器及操作条件 1.1.1 仪器 SPME手动取样装置，100 μm聚二甲基硅氧烷（PDMS），电磁搅拌/加热操作台，搅拌子（3.0 mm×10.0 mm），10、15、40 mL顶端带有孔盖子和聚四氟乙烯隔垫的样品瓶（Supelco 公司）。HP-6890气相色谱仪带质谱检测（MSD-5973）配G1701B.02.05工作站（Hewlett-Packard, USA），所用色谱柱为HP-VOC熔融毛细管柱（60 m×0.32 mm×1.8 μm）。 1.1.2 GC-MS的操作条件 色谱条件：进样口温度为250 ℃，进样口关闭五分钟，不分流进样。采用程序升温，初始 资金项目：国家质检总局科研资助项目（2002IK034）、 中山大学化学院第四届创新化学实验与研究基金（批准号：03002号）。 第一作者：蔡积进（1982年出生），男，中山大学化学与化工学院材料化学专业00级 指导教师:李攻科，E-mail :cesgkl@https://www.wendangku.net/doc/47483419.html,.
顶空固相微萃取_气质联用技术婷
网络出版时间：2014-12-25 09:49 网络出版地址：https://www.wendangku.net/doc/47483419.html,/kcms/detail/44.1620.TS.20141225.0949.002.html 基金项目：国家自然科学基金青年科学基金（31301572）；中国博士后科学基金（2014M552302）；“十二五”国家科技支撑计划（2012BAD29B06）；高等学校博士学科点专项科研基金（优先发展领域）(20113326130001)；中央高校基本科研业务费专项资金资助（DC12010303） 作者简介：李婷婷(1978—)，女，博士，副教授。主要从事水产品贮藏加工及质量安全控制方面的研究。 通讯作者：励建荣(1964—)，男，博士，教授，博导。主要从事水产品贮藏加工及质量安全控制方面的研究。 顶空固相微萃取-气质联用技术结合电子鼻分析4℃冷藏过程中三文鱼片挥发性成分的变化 李婷婷1,2，丁婷3，邹朝阳3，周凯3，赵国华1，励建荣1,3 （1.西南大学食品科学学院，重庆 400715）(2.大连民族学院生命科学学院，辽宁大连116600) (3.渤海大学食品科学研究院，辽宁省食品安全重点实验室，辽宁锦州121013） 摘要：采用顶空固相微萃取-气相色谱质谱联用（HS-SPME-GC-MS）技术，结合电子鼻，对4℃冷藏过程中三文鱼片的挥发性成分进行测定，并探究三文鱼片在4℃冷藏过程中挥发性成分的变化。结果表明，HS-SPME-GC-MS方法共检测出288种挥发性成分，主要为醛类、醇类和烃类（烷烃、烯烃、芳香烃）物质，且在冷藏期间挥发性成分中醛类物质不断减少，而酸类物质有积累的趋势，醇类和芳香族类物质则先呈现增加后降低的趋势。烃类物质在第12 d时有最大峰面积值；酯类物质则在第 6 d以后出现且为增高的趋势；而胺类等其他物质的含量在冷藏期间波动较大。用电子鼻对三文鱼在冷藏期间挥发性物质进行主 成分分析（Principal Component Analysis，PCA）、负荷加载分析（Loadings Analysis，LA）以及线性判别分析（Linear Discriminant Analysis, LDA），所得结果与HS-SPME-GC-MS方法相一致，均表明冷藏三文鱼片在第6 d、12 d及15 d的挥发性成分变化较大，是其新鲜度变化的拐点。 关键词：固相微萃取；气相色谱-质谱联用；电子鼻；三文鱼片；挥发性成分 Changes on Volatile Components for Salmon Slices during Refrigerated Storage by HS-SPME-GC-MS Technology Combined with Electronic Nose LI Ting-ting1,2, DING Ting3, ZOU Zhao-yang3, ZHOU Kai3, ZHAO Guo-hua1, LI Jian-rong1, 3 (1 College of Food Science, Xi Nan University, Chongqing 400715, China) (2 College of Life Science, Dalian Nationality of University, Dalian 116600, China) (3 Food Science Research Institute of Bohai University, Food Safety Key Lab of Liaoning Province, Jinzhou 121013; China) Abstract:The volatile components of salmon slices during 4 ℃storage were determined and analyzed by using the method of headspace solid-phase microextraction and gas chromatography mass spectrometry (HS-SPME/GC-MS) combined with the electronic nose technology. The aim was to explore the changes of volatile components during storage. The results showed that 288 kinds of volatile components determined by the technology of HS-SPME/GC-MS were mainly aldehydes, alcohols and hydrocarbons. Volatile aldehydes of cold storage salmon slices decreased during storage while contents of acids increased. Alcohols and aromatic components reached their peak points and then decreased. The maximum peak area value of hydrocarbons appeared on 12th day. Esters appeared after 6th day and then increased, while the amine and other components fluctuated greatly during cold storage. The volatile components of cold storage salmon slices were also mensurated by electronic nose and analyzed using the methods of PCA analysis, Loadings analysis and LDA analysis. The results obtained by electronic nose were consistent with the results of HS-SPME-GC-MS methods, which showed that great changes of volatile components had taken place on day 6, day 12 and day 15, and they were freshness points of inflection of salmon slices during refrigerated storage. Keywords: SPME; GC-MS; electronic nose; salmon slices; volatile components
样品前处理--固相微萃取技术综述
固相微萃取(SPME)技术综述 2010级分析化学专业杜亚辉 作为一种较新的样品前处理技术，固相微萃取技术(SPME)具有操作简单、快速，集采样、萃取、浓缩和进样于一体等诸多优点，目前已被广泛应用。下面详细阐述了SPME的技术原理、操作流程、影响因素、应用领域和新的进展。 固相微萃取(Solid-phase microextraction,SPME)是一项新型的无溶剂化样品前处理技术。固相微萃取以特定的固体（一般为纤维状萃取材料）作为固相提取器将其浸入样品溶液或顶空提取，然后直接进行GC、HPLC等分析。SPME由Pawliszyn在1989年首次报道，近10年来固相微萃取技术已成功应用于气体，液体及固体样品的前处理[2]。 1.1 固相微萃取技术及原理 固相微萃取法是以固相萃取为基础发展起来的方法，固相微萃取利用了固相萃取吸附的几何效应，其装置结构的超微化决定了它能避开经典固相萃取的许多弱点。固相微萃取技术多在一根纤细的熔融石英纤维表面涂布一层聚合物并将其作为萃取介质(萃取头)，再将萃取头直接浸入样品溶液(直接浸没－固相微萃取方法，简称DI－SPME)或采用顶空－固相微萃取方法(HS－SPME)采样[8]。由于聚合物涂层的种类很多，因而可对样品组分进行选择性富集和采集，固相微萃取的原理是一个基于待测物质在样品及萃取涂层中分配平衡的萃取过程[3]。固相微萃取利用表面未涂渍或涂渍吸附剂的熔融石英纤维或其它纤维材料作为固定相，当涂渍纤维暴露于样品时，根据“相似相溶”原理，水中或溶液中的有机物以及挥发性物质，从试样基质中扩散吸附在萃取纤维上逐渐浓缩富集。萃取时，被测物的分布受其在样品基质和萃取介质中的分配平衡所控制，被萃取量(n)与其他因素的关系可以用下式描述： n=kV f C0V s/（kV f+ V s） 式中：k为被测物在基质和涂层间的分配系数，V f和V s分别为涂层和样品的体积，C0为被测物在样品中的浓度。如果样品体积很大时(VskV f)上式可以简化成： n=kV f C0 萃取的被测物量与样品的体积无关，而与其浓度呈线性关系，因而从分析结果中得到的萃取纤维表面的吸附量，就能算出被萃取物在样品中的含量，可方便地进行定量分析[1]。 1.2 固相微萃取操作条件的选择 萃取头的构成应由萃取组分的分配系数、极性、沸点等参数来确定，在同一个样品中，因萃取头的不同可使其中一个组分得到最佳萃取而使其他组分受到抑制。平衡时间往往由众多因素所决定，如分配系数、物质扩散速度、样品基质等。此外，温度、离子浓度、样品的
固相萃取与固相微萃取
固相萃取与固相微萃取比较 日期：2012-06-26 来源：互联网 【摘要】：固相萃取(Solid Phase Extraction，SPE)是一种基于液-固分离萃取的试样预处理技术，由柱 液相色谱技术发展而来。SPE技术自70年代后期问世以来，由于其高效、可靠及耗用溶剂量少等优点， 在环境等许多领域得到了快速发展。在国外已逐渐取代传统的液-液萃取而成为样品预处理的可靠而有效的 方法。 相关专题 固相萃取(SPE)—用途广泛的样品前处理技术 一固相萃取 固相萃取(Solid Phase Extraction，SPE)是一种基于液-固分离萃取的试样预处理技术，由柱液相色谱技术发展而来。SPE技术自70年代后期问世以来，由于其高效、可靠及耗用溶剂量少等优点，在环境等许多领域得到了快速发展。在国外已逐渐取代传统的液-液萃取 而成为样品预处理的可靠而有效的方法。 SPE技术基于液相色谱的原理，可近似看作一个简单的色谱过程。吸附剂作为固定相，而流动相是萃取过程中的水样。当流动相与固定相接触时，其中的某些痕量物质(目标物)就保留在固定相中。这时用少量的选择性溶剂洗脱，即可得到富集和纯化的目标物。固相萃取可分为在线萃取线萃取前者萃取与色谱分析同步完成;而后者萃取与色谱分析分步完成，两 者在原理上是一致的。 一般固相萃取的操作步骤包括固相萃取柱(即吸附剂)的选择、柱子预处理、上样、淋洗、洗脱。在实验过程中需要具体考虑的因素如下： 1)吸附剂的选择 a.传统吸附剂 在环境分析中最为常用的反相吸附剂较适用于水样中的非极性到中等极性的有机物的 富集和纯化。其中有代表性的键合硅胶C18和键合硅胶C8等。该类吸附剂主要通过目标 物的碳氢键同硅胶表面的官能团产生非极性的范德华力或色散力来保留目标物。 正相吸附剂包括硅酸镁、氨基、氰基、双醇基键合硅胶及氧化铝等，主要通过目标物 的极性官能团与吸附剂表面的极性官能团的极性相互作用(氢键作用等)来保留溶于非极性 介质的极性化合物。由于其特殊的作用原理，在环境分析中常用于与其它类型的吸附柱联用，吸附去除干扰物，实现样品纯化。 离子交换吸附剂则主要包括强阳离子和强阴离子交换树脂，这些树脂的骨架通常为苯 乙烯-二乙烯基苯共聚物，主要是通过目标物的带电荷基团与键合硅胶上的带电荷基团相互 静电吸引实现吸附的。 b.抗体键合吸附剂(Immunosorbents-IS) 这类新型吸附剂充分利用了生物免疫抗原-抗体之间的高灵敏性和高选择性，尤其适应于水中痕量有机物的富集与分离。其特点为，由于绝大多数有机污染物为低分子量物质，不能在动物体内引发免疫反应，所以需把待定污染物键合到牛血清白蛋白的生物大分子载体上，
固相萃取
什么是SPME技术？ 固相微萃取－SPME是一种适用于GC的专利样品制备技术，其基本原理是将含水样品中的分析物直接吸附到一根带有涂层的熔融石英纤维上，然后解吸分析物。（可供应带有这些纤维的注射器）。这种取样技术具有使用便捷的特点，并且无需使用有机溶剂。 SPME纤维可以直接插入液体样品中或者停留在样品上方进行顶空取样。在顶空取样中，SPME纤维相当于“化学泵”，将化合物从液相吸入顶空，然后又吸入纤维中. 美国Supelco公司专利产品－固相微萃取SPME(Solid Phase Micro Extraction)，1994年获美国匹兹堡分析仪器会议R&D100项革新大奖，是一种应现代仪器的要求而产生的样品前处理新技术，几乎克服了以往一些传统样品处理技术的所有缺点，集采样、萃取、浓缩、进样于一体，便于携带，真正实现样品的现场采集和富集，能够与气相、气相-质谱、液相、液相-质谱仪联用，有手动或自动两种操作方式，让更多的分析工作者从重复、烦琐的操作中解脱出来。广泛应用于环保及水质处理、临床药理、公安案件分析、制药、化工、国防等领域。 固相微萃取装置(SPME)︰具有免溶剂、快速、萃取简单、可现场携带采样之仪器。可应用在非常多的领域；如药物分析、食品分析、环境污染分析（VOC、PAH、PCB、有机氯、有机磷杀虫剂）等等。 固相微萃取(SPME)非常小巧,状似一只色谱注射器，由手柄(Holder)和萃取头或纤维头(Fiber)两部分构成。萃取头是一根外套不锈钢细管的1cm长、涂有不同色谱固定相或吸附剂的熔融石英纤维头，纤维头在不锈钢管内可自由伸缩，用于萃取、吸附样品；手柄用于安装或固定萃取头，可永久使用。 无需有机溶剂、简单方便、快速、安全！ 1.SPME萃取头选择原则
顶空固相微萃取_气相色谱_质谱联用技术鉴别潲水油
顶空固相微萃取 气相色谱 质谱联用技术鉴别潲水油 李 红1,2,屠大伟1,李根容1,丁晓雯2,李沿飞 1 (1.重庆市计量质量检测研究院,国家农副加工产品及调味品质量监督检验中心,重庆400020; 2.西南大学食品科学学院,重庆400715) 摘 要:采用顶空固相微萃取与气质联用法分析了潲水油样品中的挥发性成 分,比较了不同萃取头和不同色谱柱对潲水油中挥发性成分的萃取分离效果。 结果表明,65 m PDMS DVB萃取头和D M 5MS色谱柱能萃取出较多潲水油中所 特有的香辛料成分,萃取效果较好。通过大量潲水油和正常食用植物油做对 比,找出了潲水油和正常食用植物油的差别成分:茴香脑、丁香酚及二氢大茴 香脑。 关键词:SPME GC MS;潲水油;鉴别;香辛料 中图分类号:O657.63 文献标识码:A 文章编号:1000 0720(2010)06 061 05 潲水油又叫泔水油、地沟油,是废弃食用油脂的一种。因为潲水油制备简单,成本低廉,一些不法分子为了谋取暴利,暗中将其直接作为食用油或者将其添加到其他食用植物油中销售和使用,给广大人民的生命健康带来巨大的安全隐患[1]。目前,对潲水油及煎炸老油的鉴别检验研究主要集中在以下几方面:常规理化指标检测[2~6]、电导率的检测[7]、胆固醇及脂肪酸组成分析[8]、外来污染物的检测(十二烷基苯磺酸钠、黄曲霉毒素)[9,10]以及致突变性的研究[11]等。另外,还有研究者用静态顶空方法对潲水油挥发性成分进行了GC MS 分析[12,13]。虽然对潲水油的鉴别检验报道的方法众多,但迄今为止还没有一个十分系统、准确高效的方法。 潲水油来源广泛,成分复杂,即使经过反复的处理,很多微量挥发性成分也不能有效去除。目前,未发现有文章对潲水油中微量挥发性成分进行分析。本文建立了一套顶空固相微萃取(SPME) 气质联用法测定潲水油中微量挥发性成分的方法,为潲水油的鉴别提供更加可靠的方法和理论依据。1 实验部分 1.1 仪器、试剂与样品 Trace DSQ GC/MS气质联用仪(Thermo, USA);固相微萃取仪,手动SP ME进样器,15mL 带聚四氟乙烯瓶盖的顶空样品瓶(SUPELCO, USA);85 m PA(聚丙烯)萃取头,100 m PDMS (聚二甲基硅氧烷)萃取头,65 m PDMS DVB(聚二甲基硅氧烷 二乙烯苯)萃取纤维头各一支(SUPELC O,USA)。 潲水油(SSY)样品:1~18来自4家公司的不同批次。正常食用植物油(ZCY)样品:1~8来自不同种类的食用油,购于重庆江北超市。 1.2 实验条件 1.2.1 色谱条件 DM 5MS毛细管色谱柱:50m 0.25mm 0.25 m。进样口温度:250 ,柱温:起始温度50 ,保持3min,以5 /min的速率升至170 ,保持0min,10 /min的速率升至230 ,保持3min,10 /min的速率升至250 ,保持2min。载气为氦气,流量1mL/min,不分流模式。 1.2.2 质谱条件 接口传输线温度:280 ,离 收稿日期:2010 04 10;修订日期:2010 06 20 基金项目:重庆市科技攻关计划(CS T C,2009AB7100)项目资助 作者简介:李 红(1985-),女,硕士研究生;E mail:hongl198596@https://www.wendangku.net/doc/47483419.html,
固相微萃取原理介绍
固相微萃取技术(SPME)及其应用 摘要：固相微萃取（SPME）是一种应现代仪器要求而产生的样品前处理新技术。随着人们对其原理和技术发展的深入理解，新型SPME装置的不断应用和发展，SPME已广泛应用于环保及水质处理、临床医药、公安案件处理、国防等。本文对其原理、萃取条件、联用技术的现状进行了综述。 关键词：固相微萃取; 萃取条件; 联用技术; 应用; 综述 The Solid Phase Micro Extraction (SPME) And It’s Application Abstract: The solid phase micro extraction (SPME) is a new kind of modern instrument method before output sample. Along with people as to it's the princ iple develop deep with the technique into the comprehension, the new SPME e quip continuously applied with the development, SPME already extensive and a pplied handle in the environmental protection and fluid matter, the clinical med icine, public security official's case handle, national defense etc.. Present this te xt as to it's principle, the conditions of extraction, coupling with other analytic al technologies to proceeds the overviewed. Keywords: solid-phase micro extraction; the conditions of extraction; coupling with analytical technologies; application; review 固相微萃取（Solid-Phase Microextraction，简写为SPME）是近年来国际上兴起的一项试样分析前处理新技术。1990年由加拿大Waterloo大学的Arhturhe和Pa wliszyn首创，1993年由美国Supelco公司推出商品化固相微萃取装置，1994年获美国匹兹堡分析仪器会议大奖。 固相萃取是目前最好的试样前处理方法之一，具有简单、费用少、易于自动化等一系列优点。而固相微萃取是在固相萃取基础上发展起来的，保留了其所有的优点，摒弃了其需要柱填充物和使用溶剂进行解吸的弊病，它只要一支类似进样器的固相微萃取装置即可完成全部前处理和进样工作。该装置针头内有一伸缩杆，上连有一根熔融石英纤维，其表面涂有色谱固定相，一般情况下熔融石英纤维隐藏于针头内，需要时可推动进样器推杆使石英纤维从针头内伸出。
固相微萃取
固相微萃取装置(SPME)操作规程SOP 固相微萃取装置(SPME)︰具有免溶剂、快速、萃取简单、可现场携带采样之仪器。可应用在非常多的领域； 如药物分析、食品分析、环境污染分析（VOC、PAH、PCB、有机氯、有机磷杀虫剂）等等。 SPME固相微萃取S.O.P中文操作手册 安装程序 (A) 先将Holder下方黑色保护套管转松拆开，再将不绣钢金属盖转松拆下。 注意:不绣钢金属盖有时会已松离Holder而卡在黑色保护套管，此时请将黑色保护套管再套回Holder转紧后再松开，不绣钢金属盖会回卡在Holder外牙上，再将它拆下，离开Holder。 (B) 将Holder推杆推至下端，此时有黑色圆棒秃出来(内有牙纹) 。 (C) 取出要用之Fiber，以Fiber上头外牙纹和Holder微秃出黑色圆棒内牙纹平顺锁上后，推杆小心拉回最 上端，再将 刚拆下之不绣钢金属盖及黑色保护套管依序小心套上锁紧，即完成装置。 (D) 小心试着将Holder推杆推至中端卡点处卡住，此时Coated Fiber已从保护针头内秃出来，可上下调整 黑色保护套 管及查看Holder上刻度，略估保护针头加上Coated Fiber所伸出的长度，以配合实验所需。 注意: Fiber装好后，此时勿将推杆推至最下端，会压坏Fiber之弹簧。 (E) SPME要插入样品瓶(袋)之隔塞取样或插入GC注射器之隔塞热脱附时，先将保护针头插入隔塞后，再 将推杆推 至中端卡住，秃出Coated Fiber。 (F) SPME从样品瓶(袋)隔塞取样或从GC注射器之隔塞取出时，则先收回Coated Fiber至保护针头，再取 出保护针头。 注意:因保护针头是平头针，所以新的隔塞片先以干净细针插一下以便保护针头较容易插入。GC Injection Liner(Sleeve)请改用SPME用Liner这样Coated Fiber较不会碰断。 (G) 若要从Holder拆下Fiber，先将Holder推杆拉回最上端，让Coated Fiber收回至保护针头内，把Holder 下方黑色保护套 管转松和不绣钢金属盖拆下，再将Holder推杆推至下端，让黑色圆棒秃出来，转松Fiber上头锁牙即可。
固相萃取
固相萃取(Solid Phase Extraction SPE)就是利用固体吸附剂将液体样品中的目标化合物吸附，与样品的基体和干扰化合物分离，然后再用洗脱液洗脱或加热解吸附，达到分离和富集目标化合物的目的。 与液－液萃取相比固相萃取有很多优点：固相萃取不需要大量互不相溶的溶剂，处理过程中不会产生乳化现象，它采用高效﹑高选择性的吸附剂（固定相），能显著减少溶剂的用量，简化样品于处理过程，同时所需费用也有所减少。一般说来固相萃取所需时间为液－液萃取的1/2，费用为液－液萃取的1/5。其缺点是：目标化合物的回收率和精密度要低于液－液萃取。 一．固相萃取的模式及原理 固相萃取实质上是一种液相色谱分离，其主要分离模式也与液相色谱相同，可分为正相（吸附剂极性大于洗脱液极性），反相（吸附剂极性小于洗脱液极性），离子交换和吸附。固相萃取所用的吸附剂也与液相色谱常用的固定相相同，只是在粒度上有所区别。 正相固相萃取所用的吸附剂都是极性的，用来萃取（保留）极性物质。在正相萃取时目标化合物如何保留在吸附剂上，取决于目标化合物的极性官能团与吸附剂表面的极性官能团之间相互作用，其中包括了氢键，π—π键相互作用，偶极－偶极相互作用和偶极－诱导偶极相互作用以及其他的极性－极性作用。正相固相萃取可以从非极性溶剂样品中吸附极性化合物。 反相固相萃取所用的吸附剂通常是非极性的或极性较弱的，所萃取的目标化合物通常是中等极性到非极性化合物。目标化合物与吸附剂间的作用是疏水性相互作用，主要是非极性－非极性相互作用，是范德华力或色散力。 离子交换固相萃取所用的吸附剂是带有电荷的离子交换树脂，所萃取的目标化合物是带有电荷的化合物，目标化合物与吸附剂之间的相互作用是静电吸引力。 固相萃取中吸附剂（固定相）的选择主要是根据目标化合物的性质和样品基体（即样品的溶剂）性质。目标化合物的极性与吸附剂的极性非常相似的时，可以得到目标化合物的最佳保留（最佳吸附）。两者极性越相似，保留越好（即吸附越好），所以要尽量选择与目标化合物极性相似的吸附剂。例如：萃取碳氢化合物（非极性）时，要采用反相固相萃取（此时是
固相微萃取
8．1．4．1 固相微萃取的原理 固相微萃取(solid—phase microextraction，SPME)技术是20世纪90年代初期兴起的 一项样品前处理与富集技术，它最先由加拿大Waterloo大学Pawliszyn教授的研究小组于1989年首次研制成功，属于非溶剂型选择性萃取法，是一种集采样、萃取、浓缩、进样于一体的分析技术。 SPME装置略似进样器，在特制注射器筒内的不锈钢细管顶端分别连接一根穿透针和纤维固定针，针头上连接一根熔融石英纤维，上面涂布一层多聚物固定相，注射器的柱塞控制纤维的进退。当纤维暴露在样品中时，涂层可从液态／气态基质中吸附萃取待测物，经过一段时间后，已富集了待测物的纤维可直接转移到仪器(通常是气相色谱仪，即SPME—GC) 中，通过一定的方式解吸附，然后进行分离分析。典型的SPME装置如图8一12所示。 SPME熔融石英纤维涂布固定相与样品或其顶空充分接触，待测物在两相间分配达到平衡后，两相中待测物浓度关系如下式： N。一KⅥV。C。／(KU+V。) (8—2) 式中，N。为固定相中待测物的分子数；K为两相间待测物的分配系数；V。为固定液体积；U为样品体积；c。为样品中待测物浓度。 因为U》V。，故式(8—2)可简化为： N。=Ku％(8-3) 由式(8-3)可知，固定液吸附待测物分子数与样品中待测物浓度呈线性关系，即样品中待测物浓度越高，SPME吸附萃取的分子数越多。当样品中待测物浓度一定时，萃取分子数主要取决于固定液体积和分配系数。同时，方法的灵敏度和线性范围的大小也取决于这两个参数。固定液厚度越大(即y。越大)，萃取选择性越高(K越大)，则方法的灵敏度越高。 由此可见，选择合适的固定液对于萃取结果是很重要的。
固相微萃取原理及其在化学分析中的应用.
固相微萃取原理及其在化学分析中的应用 陈老师 （哲博化工科技有限公司哲博检测中心，浙大国家大学科技园，杭州310013， Email：zhebocs@https://www.wendangku.net/doc/47483419.html,） 自从1990 年Pawliszyn 等提出了一种新的固相萃取技术———固相微萃取( solid phase microextraction , SPME)以来，SPME已迅速应用在各种化学分析领域。SPME是一种基于气固吸附(吸收) 和液固吸附(吸收) 平衡的富集方法,利用分析物对活性固体表面(熔融石英纤维表面的涂层) 有一定的吸附(吸收) 亲合力而达到被分离富集的目的。自1994 年SPME 装置商品化以来,该技术取得了较快的发展,除了主要与气相色谱(GC) 联用外,还可与高效液相色谱(HPLC) 、毛细管电泳(CE) 以及紫外分光光度(UV) 等多种分离分析技术联用。SPME 已开始应用于分析水、土壤、空气等环境样品,以及血、尿等生物样品和食品、药物等各个方面 一、固相微萃取及气质联用技术的原理和优点 SPME技术是根据有机物与溶剂之间的“相似者相溶”的原则,利用石英纤维表面的色谱固定相或吸附剂对分析组分的吸附作用,将组分从试样基质中萃取出来,并逐渐富集,完成此试样前处理过程1在进样过程中,利用气相色谱进样口的高温将吸附的组分从固定相中解吸下来,由色谱仪进行分析。对于一个单组分的单相体系,当被分析有机物在萃取头与萃取体系之间达到平衡时,分析物与萃取头之间有一分配系数K,该分配系数与分析物在萃取体系中的量有如下关系:
式中:N 为吸附于萃取头上分析物的量; C0 为萃取前分析物在样品中的浓度; K 为分析物在萃取头和样品间的分配系数; Cs 为分析物在萃取后样品中的浓度; Cf 为分析物在萃取头中的浓度; Vf 为萃取头的体积; Vs 为样品的体积。可以看出,体系中的K及Vf 值是影响方法灵敏度的重要因素。由于K Vf n Vs ,所以上式近似为N = K C0 Vf , K值取决于萃取头的固定相类型,而对一特定的萃取头,其体积Vf 是一个定值,故N 与C0 之间成线性关系, C0 可由气相色谱仪测定。上面公式的推导从化学热力学平衡态化学势相等的原理可以得出,但是实际体系往往是多组分共存因此,组分的K值不仅与同一组分不同相内的含量有关,而且与其他组分的含量也有关1实际的数学表达式较为复杂,但由于在所分析样品中的组分的含量一般较低,彼此的作用可以忽略,因此上式仍有一定的代表性,可解释SPME中的各种现象。 二、SPME特点 SPME 装置是在一支长约1 cm 长的熔融石英纤维上涂敷一层厚度为30～100μm 高聚物固定相,如聚甲基硅氧烷或聚丙烯酸酯。纤维与形如注射器装置的不锈钢柱塞相连,收缩在不锈钢针头之中。压柱塞从针头中抵出纤维并与试样溶液或顶空接触,使分析物被吸附(吸收) 而分配到涂敷层内。富集在纤维上的分析物,在气相色谱仪进样口通过热解吸(解脱) 到色谱柱中。在HPLC 的情况下,籍助SPME--HPLC的接口将吸附在纤维上的分析物传送至分析柱。SPME 的特点是集取样、萃取、富集、进样于一身。一般的试样预处理方法只能完成其中的一、二步,而SPME 根据自身的特点,集多步为一体,简化了试样预处理过程。SPME易于操作,是试样与固相涂层直接作用,几乎不消耗溶剂,降低了成本,保护了环境。SPME 的速度取决于分析物分配平衡所需的时间,一般在2～30 min 内即可达到平衡。该技术适用于微量或痕量组分的富集。 三、固相微萃取的萃取条件 SPME固定相的选择1选用何种固定相应综合考虑分析组分在各相中的分配系数、极性与沸点,其基本原则是“相似相溶原理”,可依据所分析物的分子量和极性的不同,选取最合适分析组分的固定相1小分子量或挥发性的化合物通常选
固相微萃取
采用固相微萃取和液相色谱-质谱联用法对果汁中氨基甲酸酯类及苯基脲类农药残留进行分析 摘要：采用一种固相微萃取及液相色谱-单一四极（LC/MS）、液相色谱-四极离子阱质谱的方法对果汁中的氨基甲酸酯类及苯基脲类农药残留进行检测。提取果汁中水基质中农药残留用三种类型的纤维：50-μm 聚乙二醇/类树酯（CW/TPR）、60-μm 聚二硅烷氧/二乙烯基苯（PDMS/DVB）、85-μm 聚丙烯酸酯。综合不同提取条件得出，时间为90分钟，温度为20度，体积1毫升为最佳。萃取后，一种静态模式下的解吸是在SPME/HPLC的特定界面室执行的（先在该界面室填满70%甲醇和30%水）。以果汁两种固定含量（0.2mg/kg-1和0.5mg/kg-1）为例，最佳回收率获得是采用PDMS/DVB和CW/TPR纤维萃取，范围为25%-82%（绿谷隆、敌草隆、乙霉威），相对标准偏差为1%-17%。意大利和西班牙的立法规定果汁中农药定量限为0.005-0.05μgml-1，任何情况下只能等于或小于最大残留限量（MRLs）。质谱分析通过电离雾化源以正离子模式下，在单一四极和QIT质量分析器可以有选择性离子监测和多反应监测两种模式操作分析。提出的这种新方法适应于选定的果汁中农药含量的测定。 前言 对食物中农药残留评估的最重要目的是确保食品质量和防止消费者的可能健康风险。随着农药残留频繁的在柑橘类水果和葡萄中发现，消费者很容易把视角转移到相关的果汁上，然后变成一种消费者健康的风险担忧。 为了在食品复杂的基质中获得一种实用、快速的检测农药残留方法，一些简单的处理办法已发展起来，包括液液萃取[1]、超临界流体萃取[2]、固相萃取[3]和固相微萃取[4]，然而，对于液液萃取和固相萃取，最大的缺点就是要使用大量的溶剂，步骤操作繁琐，在分析物和干扰物很可能被共同萃取之前对萃取物浓缩。固相微萃取，1990年由Arthur和Pawliszyn提出来[5]，是一种使用硅纤维涂在合适的固定相上而可以进行萃取的技术。它形成了一种方便选择的萃取方法，因为它能够把抽样、提取、浓缩、进样变成一个单一的步骤而不需要溶剂。它通常与GC、GC/MS、HPLC、HPLC/MS联用并且检测各种各样的化合物，包括食物中农药、农用化学品、其他污染物[4,6-8]。 如今，液相色谱-质谱法对水果蔬菜中农药分析是最具有权威性的方法之一[9,10]。特别是LC串接了质谱（离子阱或三重四极杆），对水果中农药残留检测变成一种非常灵敏的技术[11]。还有一些方法，固相微萃取技术和质谱的常规色谱分析联用，或者是火焰热分析联用，能够发现和量化水基质中的农药残留。通过SPME/GC/FTD/MS可以检测果汁中的有机磷[12-14]。通过SPME/LC/MS可以检测水和酒中一些氨基甲酸酯类及苯基脲类农药残留[15]。还可以检测水果中的杀菌剂[4]。 现在的工作目的就是为了开发一种新型的分析方法，能够对各种类型的果汁中的氨基甲酸酯类及苯基脲类农药残留进行检测。直到现在SPME/LC/MS和SPME/LC/MS/MS方法还没有被报到过。在这种新方法中，对MS-MS转换分析农药的研究满足欧盟已确定标准的要求[16]。 我们特别调查了两种不同类型的常见农药：（a）氨基甲酸酯类如丁硫克百威、丙硫克百威、克百威、抗蚜威（杀虫剂）、乙霉威（杀真菌剂）；（b）苯基脲类如敌草隆、灭草隆、绿谷隆（除草剂）。 由于这些农药在水中具有很高的溶解度（17），氨基甲酸酯类杀虫剂主要用在农业，而且易分布在如水果、相关衍生物等水性食物中。苯基脲类除草剂使用在棉花、水果、生长谷物的
固相萃取
液相色谱有正相和反相之分。正相色谱和反相色谱还有吸附色谱和极性化学键键合色谱之分。如果采用固定相的极性大于流动相的极性，就称为正相色谱；如果固定相的极性小于流动相的极性，则称为反相色谱。由于极性化合物更容易被极性固定相所保留，所以正相色谱系统一般适用于分离极性化合物，极性小的组分先流出。相反，反相色谱系统一般适用于分离非极性或弱极性化合物，极性大的组分先流出。 在正相色谱中，一般采用极性键合固定相，硅胶表面键合的是极性的有机基团，键合相的名称由键合上去的基团而定。最常用的有氰基（-CN）、氨基（-NH2）、二醇基（DIOL）键合相。流动相一般用比键合相极性小的非极性或弱极性有机溶剂，如烃类溶剂，或其中加入一定量的极性溶剂（如氯仿、醇、乙腈等），以调节流动相的洗脱强度。通常用于分离极性化合物。一般认为正相色谱的分离机制属于分配色谱。组分的分配比K值，随其极性的增加而增大，但随流动相中极性调节剂的极性增大（或浓度增大）而降低。同时，极性键合相的极性越大，组分的保留值越大。该法主要用于分离异构体，极性不同的化合物，特别是用来分离不同类型的化合物。 反相键合相色谱法在反相色谱中，一般采用非极性键合固定相，如硅胶-C18H37（简称ODS或C18）硅胶-苯基等，用强极性的溶剂为流动相，如甲醇/水，乙腈/水，水和无机盐的缓冲液等。目前，对于反相色谱的保留机制还没有一致的看法，大致有两种观点：一种认为属于分配色谱，另一种认为属于吸附色谱。分配色谱的作用机制是假设混合溶剂（水+有机溶剂）中极性弱的有机溶剂吸附于非极性烷基配合基表面，组分分子在流动相中与被非极性烷基配合基所吸附的液相中进行分配。吸附色谱的作用机制是把非极性的烷基键合相，看作是在硅胶表面上覆盖了一层键合的十八烷基的“分子毛”，这种“分子毛”有强的疏水特性。 固相萃取是建立在传统的液液萃取基础上，填料为一般硅胶基键合固定相，基于spe固体填料与样品中的目标化合物产生各种作用力，将目标物与样品基质分离，再用洗脱液洗脱，达到分离和富集目标化合物的目的。固相萃取是一种纯化提取物，改善结果准确度和重现性的快速而经济的技术。 1.固相萃取分类及萃取柱填料选取 根据分离模式不同，固相萃取可分为正相、反相、离子交换、混合机理分离模式。（1）反相固相萃取 填料硅胶表面的亲水硅醇基通过硅烷化学反应，键合非极性烷基或芳香基、聚合物等材料作为反相固定相，被测物的碳氢键与固定相表面官能团产生非极性的范德华力或色散力，使得极性溶剂中的非极性以及弱极性的物质保留在固定相上，达到净化、富集样品的目的。 反相固相萃取萃取柱填料一般有以下几种：C18、C8、C4、CN、Ph。 （2）正相固相萃取