微波辅助萃取/气相色谱-质谱联用分析蔬菜中的有机磷农药

建立了微波辅助萃取（MAE）/气相色谱-质谱联用法（GC-MS）测定蔬菜样品中二嗪磷、水胺硫磷的分析方法，研究了不同溶剂的萃取效率。选择二氯甲烷为萃取溶剂，采用二因素三水平的正交设计实验优化了萃取溶剂体积和萃取时间。方法的线性范围分别为二嗪磷和对硫磷4ng/g-400ng/g，水胺硫磷20ng/g-400ng/g，检出限分别为二嗪磷和对硫磷4ng/g-400ng/g、水胺硫磷20ng/g-400ng/g，检出限分别为二嗪磷0.29ng/g、对硫磷1.70ng/g、水胺硫磷2.30ng/g。测定200.0ng/g和50.0ng/g加标蔬菜样品，回收率为72.2%-102.0%,RSD为1.5%-11.0%。与传统的机械振荡萃取法相比，不仅萃取效率相当，而且还具有省时省溶剂的优点。     

SPE – Microwave‐assisted extraction coupled system for the extraction of pesticides from water samples

SPE is a commonly applied technique for preconcentration of pesticides from water samples. Microwave‐assisted extraction (MAE) technique is the extraction applied for preconcentration of different compounds from solid samples. SPE coupled with MAE is capable of preconcentrating these compounds from water samples too. This investigation was aimed at improving the efficiency of atrazine, alachlor, and α‐cypermethrin pesticide extraction from the spiked water samples applying SPE followed by MAE. In this way, MAE served for elution of pesticides from C₁₈‐extraction disks with solvent heated by microwave energy. Various elution conditions were tested for their effects on the extraction efficiency of the SPE–MAE combined technique. Several parameters, such as elution solvent volume (mL), elution temperature (°C), and duration of elution (min), affect the extraction efficiency of the SPE–MAE coupled system and need to be optimized for the selected pesticides. In order to develop a mathematical model, 15 experiments were performed in the central composite design. The equation was then used to predict recoveries of the pesticides under specific experimental conditions. Optimization of microwave extraction was accomplished using the genetic algorithm approach. Best results were achieved using 20 mL of ethanol at 60°C. Optimal hold time was 5 min and 24 s. The SPE–MAE combination was also compared with the conventional SPE extraction technique with elution of a nonpolar or a moderately polar compound with nonpolar solvents.     

固相萃取法与基质固相分散法在橙子中有机磷农药残留分析中的应用

建立了固相萃取(SPE)-反相高效液相色谱(RP-HPLC)同时测定橙子中痕量辛硫磷、二嗪农有机磷农药残留量的方法。样品经甲醇超声提取、C18固相萃取柱净化后,采用液相色谱柱分离,以乙腈-水(体积比为85∶15)为流动相等度洗脱,于254 nm下紫外检测。结果表明:在0.1～10.0 mg/L和0.4～10.0 mg/L范围内,辛硫磷、二嗪农的质量浓度与峰面积呈良好的线性关系;样品的加标平均回收率为87.3%～102.7%,相对标准偏差(RSD)为0.9%～4.9%。将该分析结果与用基质固相分散法(MSPD)处理样品所得的结果相比较,发现SPE对二嗪农的提取效果较好,而MSPD对辛硫磷的提取效果较好,但两种方法都能较好地净化样品,均能满足残留量的分析要求。     

Continuous microwave-assisted extraction coupled on-line with liquid-liquid extraction: determination of aliphatic hydrocarbons in soil and sediments

This paper describes a new extraction method for the determination of aliphatic hydrocarbons (AHs) in soil and sediment samples, using continuous microwave-assisted extraction (MAE) combined with liquid-liquid extraction, for clean-up purposes. Analytical determinations were carried out by gas chromatography coupled with impact ionization mass spectrometry. The influence of the experimental conditions was tested using an agricultural soil spiked with standards (stored at 4 degrees C for 1 month) as reference soil. Maximum extraction efficiencies (80-90%) were achieved using 0.1-1.0g of sample, 60microl of water and 3ml of n-hexane (extractant) and 5min of extraction time; less than 70% of the most volatile hydrocarbons (C(9)-C(12)) were recovered since many evaporated during the drying step of the sample. MAE was compared with a conventional extraction method such as Soxhlet and a good agreement in the results was obtained (average recovery percentage value of 105% by comparing MAE against Soxhlet). Quality parameters such as linear range (0.5-800microg/g), limits of detection (LODs) (0.1-0.2microg/g) and precision (RSD, 4-6%) were determined using spiked soil samples. This method was successfully applied to the analysis of aliphatic hydrocarbons (C(9)-C(27) including pristane and phytane) in contaminated real samples.     

A multiresidue method for the analysis of pesticide residues in polished rice (Oryza sativa L.) using accelerated solvent extraction and gas chromatography and confirmation by mass spectrometry

An analytical procedure using accelerated solvent extraction and gas chromatography with an electron capture detector has been optimized to simultaneously determine the residue of two insecticides (diazinon and EPN) and one fungicide (isoprothiolane) in polished rice and was confirmed by GC-mass spectrometry. Several parameters, including temperature, pressure, solvent ratio, cell size and cell cycle, were thoroughly investigated to find the optimal extraction conditions. The average recoveries of the three pesticides were between 82.7 and 126.4% at spiking levels of 0.1 and 0.5 ppm. The relative standard deviations were less than 7% for all of the recovery tests. The optimum accelerated solvent extraction operating conditions were 100 degrees C, 1500 atm, acetone-n-hexane (20:80 v/v) as the extraction solvent, two cycles, and a cell size of 33 ml. The total extraction time was approximately 20 min. The optimized procedure has also been applied to the determination of diazinon, isoprothiolane and EPN in real rice samples. In conclusion, accelerated solvent extraction was used for the first time for the analysis of diazinon, isoprothiolane and EPN in polished rice and offers the possibility of a fast and simple process for obtaining a quantitative extraction of the studied pesticides.     

Rapid method for the determination of organochlorine pesticides and PCBs in fish muscle samples by microwave-assisted extraction and analysis of extracts by GC-ECD

A procedure for the multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in fish muscle samples has been developed. The method is based on the microwave-assisted extraction (MAE) of food samples from an acetonitrile-water (95 + 5, v/v) mixture followed by SPE cleanup of the extracts and analysis by GC with an electron capture detector. MAE operational parameters, such as the extraction solvent, temperature, and time, were optimized with respect to the extraction efficiency of the target compounds from food samples with 10-13% fat content. The chosen extraction technique allows reduction of the solvent consumption and extraction time when compared with methods already used. Acetonitrile is a good extraction solvent for low-fat matrixes (2-20% fat content), such as fish samples, because it does not significantly dissolve the highly polar proteins, salts, and sugars commonly found in food and gives high recoveries of a wide polarity range of analytes. For purification, SPE using LC-Florisil was shown to be sufficient for the removal of coextracted substances. Recoveries > 78% with RSD values < 15% were obtained for all compounds under the selected conditions. Method quantification limits were in the 5-10 microg/kg range. The method was applied to the analysis of samples of herring (Clupea harengus) purchased at the local fish market. The method is rapid and reliable for the determination of organochlorine analytes in fish muscle.     

Determination of organophosphorus pesticides in soil by headspace solid-phase microextraction

Headspace solid-phase microextraction (SPME) has been developed for the analysis of common organophosphorus pesticides in soil. Factors such as adsorption-time, sampling temperature and matrix modification by addition of water were carefully considered to optimize the extraction efficiency. This technique could achieve limits of detection of 143 ng/g for Malathion and Parathion, and 28.6 ng/g for Phorate, Diazinon and Disulfoton in humic soil when the extracted sample was analyzed by gas chromatography-flame ionization detector (GC-FID). Lower limits of detection of 28.6 ng/g for Malathion and Parathion, and 14.3 ng/g for Phorate, Diazinon and Disulfoton can be achieved by analyzing the extracted sample with gas chromatography/mass spectrometric detector (GC/MS). As the extraction efficiency was generally better when analyzing sandy soil, the limits of detection are envisaged to be even better for such a matrix. The technique was found to be reliable with good precision of about 6.5% RSD for the sandy soil and about 15% for the humic material. The poorer precision of extraction from the humic material is probably related to the poorer homogeneity of this material. The linearity of extraction was good with linear calibration in the range of 0.143 to 28.6 μg/g. Finally, headspace SPME was compared to aqueous extraction of soil followed by SPME (LE-SPME). The recoveries obtained by headspace SPME were comparable to those from liquid-liquid extraction of soil followed by SPME. However, the analysis of headspace SPME has less background interference. Perhaps, the greatest advantage of this technique is its non-destructive nature so that it is possible to perform further laboratory analysis of the samples after headspace SPME has been carried out. Received: 13 July 1998 / Revised: 10 November 1998 / Accepted: 17 November 1998     

Determination of organophosphorus pesticides in soil by headspace solid-phase microextraction

Headspace solid-phase microextraction (SPME) has been developed for the analysis of common organophosphorus pesticides in soil. Factors such as adsorption-time, sampling temperature and matrix modification by addition of water were carefully considered to optimize the extraction efficiency. This technique could achieve limits of detection of 143 ng/g for Malathion and Parathion, and 28.6 ng/g for Phorate, Diazinon and Disulfoton in humic soil when the extracted sample was analyzed by gas chromatography-flame ionization detector (GC-FID). Lower limits of detection of 28.6 ng/g for Malathion and Parathion, and 14.3 ng/g for Phorate, Diazinon and Disulfoton can be achieved by analyzing the extracted sample with gas chromatography/mass spectrometric detector (GC/MS). As the extraction efficiency was generally better when analyzing sandy soil, the limits of detection are envisaged to be even better for such a matrix. The technique was found to be reliable with good precision of about 6.5% RSD for the sandy soil and about 15% for the humic material. The poorer precision of extraction from the humic material is probably related to the poorer homogeneity of this material. The linearity of extraction was good with linear calibration in the range of 0.143 to 28.6 μg/g. Finally, headspace SPME was compared to aqueous extraction of soil followed by SPME (LE-SPME). The recoveries obtained by headspace SPME were comparable to those from liquid-liquid extraction of soil followed by SPME. However, the analysis of headspace SPME has less background interference. Perhaps, the greatest advantage of this technique is its non-destructive nature so that it is possible to perform further laboratory analysis of the samples after headspace SPME has been carried out.     

Determination of two oxy-pyrimidine metabolites of diazinon in urine by gas chromatography/mass selective detection and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry

An analytical method was developed for the determination in urine of 2 metabolites of diazinon: 6-methyl-2-(1-methylethyl)-4(1H)-pyrimidinone (G-27550) and 2-(1-hydroxy-1-methylethyl)-6-methyl-4(1H)-pyrimidinone (GS-31144). Two of the urine sample preparation procedures presented rely on gas chromatography/mass selective detection (GC/MSD) in the selected ion monitoring mode for determination of G-27550. For fast sample preparation and a limit of quantitation (LOQ) of 1.0 ppb, urine samples were purified by using ENV+ solid-phase extraction (SPE) columns. For analyte confirmation at an LOQ of 0.50 ppb, classical liquid/liquid partitioning was used before further purification in a silica SPE column. An SPE sample preparation procedure and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry (LC/ESI/MS/MS) were used for both G-27550 and GS-31144. The limit of detection was 0.01 ng for G-27550 with GC/MSD, and 0.016 ng when LC/ESI/MS/MS was used for both G-27550 and GS-31144. The LOQ was 0.50 ppb for G-27550 when GC/MSD and the partitioning/SPE sample preparation procedure were used, and 1.0 ppb for the SPE only sample preparation procedure. The LOQ was 1.0 ppb for both analytes when LC/ESI/MS/MS was used.     

Simultaneous liquid chromatographic analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol in human plasma. Comparison of amperometric and coulometric detection

The comparison of two HPLC methods, one with electrochemical detection and the other with coulometric detection, for the simultaneous analysis of catecholamines and 4-hydroxy-3-methoxyphenylethylene glycol (MHPG) in human plasma is presented. The careful pre-treatment of plasma samples is based on an innovative two-step procedure by means of solid-phase extraction (SPE) which uses one single hydrophilic-lipophilic balance cartridge. The extraction yield values found were higher than 85% for epinephrine, norepinephrine and MHPG, and higher than 70% for dopamine. The assays carried out on real plasma samples with the coulometric system gave good results in terms of sensitivity (limits of quantitation: 0.10-0.15 ng ml(-1) for catecholamines, 0.6 ng ml(-1) for MHPG) and selectivity, while interference was sometimes found when using the amperometric system. Precision was also satisfactory, with relative standard deviation values for intermediate precision always lower than 6%. The HPLC method with coulometric detection coupled to a novel SPE procedure is thus suitable for the simultaneous determination of catecholamines and MHPG in plasma of volunteers subjected to experimental stress.     

Importance of control of enzymatic degradation for determination of bisphenol A from fruits and vegetables

The purpose of this study was to develop an analytical method for determination of bisphenol A (BPA) from fruits and vegetables. The present method developed for extraction of BPA from samples was based on solid-phase extraction (SPE) method and solvent extraction. Recovery results in the samples spiked with a 10 ng/ml BPA [no detection (<1 ng/g) to 77%] were lower than those in the samples with a 50 ng/ml BPA (26-96%). The fact that the low recovery results were caused by BPA degradation by enzymes is found. These problems were proved by the pH (pH ≤3) and the heating treatment (at ≥80 °C for 5 min). However, because the heating treatment at temperatures of ≥80 °C for 5 min is more difficult and time-consuming method than the pH control, we suggest that the pH control is useful to prevent BPA degradation. Good recovery results (82-101%) were obtained from all fruit and vegetable samples after pH treatment (pH ≤3). Effective elimination of impurities and a good detection limit (1 ng/g) were obtained with a method involving two SPE cartridges (OASIS HLB and Sep-Pak Florisil cartridge).     

Comparison of microwave-assisted extraction of triazines from soils using water and organic solvents as the extractants

Microwave-assisted extraction (MAE) for the separation of atrazine, simazine and prometryne from synthetic soil samples, using water and some organic solvents as the extractants, was studied in detail. The effects of the soil matrix, the soil moisture and the pH of the aqueous extraction system on the MAE efficiency were also studied. It was found that the three triazines could be efficiently extracted under the conditions of 100% magnetron power output (600 W), the first grade of pressure (from 0.1 MPa to 0.5 MPa), 30 ml solvent and 4 min microwave heating with water or organic solvents, except for prometryne with dichloromethane solvent for 1-4 g sandy loam sample. This interesting result was explained by triazines' solubility in water, their sorption properties in soils and the ability of the solvent to absorb microwave energy. Finally, evaluation of the extraction efficiency, as well as the treatment and determination of MAE extracts, suggested that water, as a cheap, safe and environmentally friendly solvent, can be a good alternative to organic solvents, used as the extractants for MAE of triazines from soils.     

LC–UV determination of atrazine and its principal conversion products in soil after combined microwave-assisted and solid-phase extraction

A multiresidue method developed for the analysis of atrazine and its principal conversion products, deisopropylatrazine (DIA), deethylatrazine (DEA) and hydroxyatrazine (HA), in soil is presented. The method is based on the microwave-assisted extraction (MAE) of soil with aqueous methanol followed by solid-phase extraction (SPE) of the extracts and subsequent analysis by LC–UV with a diode array detector. MAE operational parameters (extraction solvent, extractant volume) were optimized with respect to extraction efficiency of the target compounds from soils with 2.5% organic matter (OM) content. Recoveries above 80% were obtained for all solutes. Soil OM content did not affect analyte recoveries. Recoveries from fresh and aged residues, the latter weathered under cold storage conditions, were not statistically different. Finally, MAE was found to be superior in terms of extraction efficiency, sample throughput, and solvent consumption to conventional flask-shaking extraction.     

Isolation, purification and determination of 4-n-nonylphenol and 4-tert-octylphenol in aqueous and biological samples

The aim of the present study was to attempt to describe the procedure of isolation, purification, enrichment and determination of 4-n-nonylphenol (4-n-NP) and 4-tert-octylphenol (4-t-OP) in water and biological samples (fish tissue). There were five procedures of solid phase extraction (SPE) tested using different sorbents for the isolation of analytes from water samples. Moreover, we isolated these chemicals from biological matrices with the aid of various extraction methods. The purpose of it was to perform an optimisation of ultrasonic bath, accelerated solvent extraction (ASE) and solid phase extraction process of alkylphenols from biological samples, through the choice of selective sorbents (octadecyl, octadecyl end-capped and amine) and search solvents (methylene chloride, methanol, hexane). Reversed-phase HPLC with diode array detection was used for the determination of 4-n-NP and 4-t-OP in water and fish tissue samples. Sensitivity was evaluated by determining the limit of detection (LOD=0.06 and 0.04ng microL(-1)) and limit of quantification (LOQ=0.18 and 0.16ng microL(-1)) of 4-NP and 4-t-OP, respectively. A series of standard solutions for 4-n-NP and 4-t-OP provided the basis for plotting an analytical curve and obtaining a linear dependence in the range of approximately 1-25ng microL(-1). The best efficiencies obtained for 4-n-NP and 4-t-OP in water samples were 76.65% (+/-1.49) and 83.08% (+/-3.73), respectively. In the case of fish tissue, different situation was observed because the obtained values were considerably lower, being 68.32% for 4-t-OP using hexane (program 1) as solvent and 72.35% (program 2) for 4-n-NP using acetonitrile.     

Gas chromatographic/mass spectrometric determination of flumioxazin extracted from soil and water

A method was developed for determining flumioxazin in soil and water. Recovery efficiencies for solid-phase extraction (SPE) of flumioxazin from deionized, well, and surface water were between 72 and 77%. SPE was superior to liquid-liquid extraction, using water-hexane and water-chloroform emulsions, which resulted in retrieval efficiencies of 25 and 22%, respectively. However, liquid-liquid extraction with ethyl acetate improved recovery of total flumioxazin to >64%. Extraction from soil samples by direct solvent/soil extraction methods recovered between 18 and 76% of applied flumioxazin, depending on the solvent combination used. However, the use of accelerated solvent extraction techniques resulted in a 106 +/- 8% recovery of flumioxazin from soil. In analysis by capillary gas chromatography with mass selective detection, flumioxazin had a calculated limit of detection of 9 ng/mL with a retention time of 16.66 min.     

Experimental design for optimization of microwave-assisted extraction of benzodiazepines in human plasma

A simple and fast microwave-assisted-extraction (MAE) method has been evaluated as an alternative to solid-phase extraction (SPE) for the determination of six benzodiazepines widely prescribed in European countries (alprazolam, bromazepam, diazepam, lorazepam, lormetazepam and tetrazepam) in human plasma. For MAE optimization a Doehlert experimental design was used with extraction time, temperature and solvent volume as influential parameters. A desirability function was employed in addition to the simultaneous optimization of the MAE conditions. The analysis of variance showed that the solvent volume had a positive influence on the extraction of all the analytes tested, achieving a statistically significant effect. Also, the extraction time had a statistically significant effect on the extraction of four benzodiazepines. The selected MAE conditions—89 °C, 13 min and 8 mL of chloroform/2-propanol (4:1, v/v)—led to recoveries between 89.8 ± 0.3 and 102.1 ± 5.2% for benzodiazepines using a high performance liquid chromatography method coupled with diode-array detection. The comparison of MAE and SPE shows better results for MAE, with a lower number of steps in handling the sample and greater efficiency. The applicability of MAE was successfully tested in 27 plasma samples from benzodiazepine users.     

Quantification of the xenoestrogens 4-tert.-octylphenol and bisphenol A in water and in fish tissue based on microwave assisted extraction, solid-phase extraction and liquid chromatography-mass spectrometry

Extraction methods were developed for quantification of the xenoestrogens 4-tert.-octylphenol (tOP) and bisphenol A (BPA) in water and in liver and muscle tissue from the rainbow trout (Oncorhynchus mykiss). The extraction of tOP and BPA from tissue samples was carried out using microwave-assisted solvent extraction (MASE) followed by solid-phase extraction (SPE). Water samples were extracted using only SPE. For the quantification of tOP and BPA, liquid chromatography mass spectrometry (LC-MS) equipped with an atmospheric pressure chemical ionisation interface (APCI) was applied. The combined methods for tissue extraction allow the use of small sample amounts of liver or muscle (typically 1 g), low volumes of solvent (20 ml), and short extraction times (25 min). Limits of quantification of tOP in tissue samples were found to be approximately 10 ng/g in muscle and 50 ng/g in liver (both based on 1 g of fresh tissue). The corresponding values for BPA were approximately 50 ng/g in both muscle and liver tissue. In water, the limit of quantification for tOP and BPA was approximately 0.1 microg/l (based on 100 ml sample size).     

Determination of quinolones in water samples by solid-phase extraction and liquid chromatography with fluorimetric detection

A method is reported for the determination, in water samples, of 10 quinolones which are used as veterinary drugs. Analytes are isolated from samples by solid-phase extraction (SPE) and analysed by reversed-phase high-performance liquid chromatography using fluorimetric detection. A solid-phase extraction procedure based on retention on HBL OASIS cartridges and elution with a mixture of acetonitrile-water in basic medium is suitable for pre-concentration of the analytes. Pre-concentration factors up to 250 can be obtained. The quinolones are separated with an octyl silica-based column and mobile phases consisting of aqueous oxalic acid solutions and acetonitrile mixtures. The attained detection limits of the whole process are in the ng l(-1) level when 250 ml of water sample is processed. Recovery rates, from natural water samples spiked at 2060 ng l(-1) level, range from 70 to 100% and common standard deviation are about 6-12%.     

Determination of alachlor, metolachlor, and their acidic metabolites in soils by microwave-assisted extraction (MAE) combined with solid phase extraction (SPE) coupled with GC-MS and HPLC-UV analysis

A well-validated analytical method based on microwave-assisted extraction (MAE) and SPE is presented for the combined analysis of alachlor, alachlor-oxanilic acid (OXA), alachlor-ethanesulfonic acid (ESA), metolachlor, metolachlor-OXA, metolachlor-ESA residues in soils. Extraction of solutes by soil sample was carried out by MAE for 20 min at 100 degrees C in the presence of 50 mL solution (methanol/water 50:50), the extract was subsequently passed through C18 cartidges and fractionated into two fractions, the first with parent compounds (PCs) analyzed with GC-MS and the second one containing the metabolites analyzed with HPLC. For the SPE step, various types of sorbents (Environmental C18, tC18, Supelclean ENVI-carb, and LiChrolut EN) have been used, and their respective advantages and disadvantages are discussed. After the method optimization, average recovery values of all solutes were > 71% in the 50-500 microg/kg fortification range with RSD <10%. The LOQ and LOD were 10-50 and 5-10 microg/kg, respectively. The method was validated with two types of soils (1 and 2.4% organic matter) and in fresh (12 h aging), intermediate (1 wk aging), and aged (1 month aging) spiked samples. Moreover, residue levels determined after field application of alachlor or metolachlor were higher when soils were processed using this method than with a comparison method based on an overnight flask shaking (FS) of soil suspension.     

Determination of flunitrazepam and 7-aminoflunitrazepam in human urine by on-line solid phase extraction liquid chromatography-electrospray-tandem mass spectrometry

A method using an on-line solid phase extraction (SPE) and liquid chromatography with electrospray-tandem mass spectrometry (LC-ES-MS/MS) for the determination of flunitrazepam (FM2) and 7-aminoflunitrazepam (7-aminoFM2) in urine was developed. A mixed mode Oasis HLB SPE cartridge column was utilized for on-line extraction. A reversed phase C₁₈ LC column was employed for LC separation and MS/MS was used for detection. Sample extraction, clean-up and elution were performed automatically and controlled by a six-port valve. Recoveries ranging from 94.8 to 101.3% were measured. For both 7-aminoFM2 and FM2, dual linear ranges were determined from 20 to 200 and 200-2000 ng/ml, respectively. The detection limit for each analyte based on a signal-to-noise ratio of 3 ranged from 1 to 3 ng/ml. The intra-day and inter-day precision showed coefficients of variance (CV) ranging from 4.6 to 8.5 and 2.6-9.2%, respectively. The applicability of this newly developed method was examined by analyzing several urine samples.