Inexpensive, effective novel activated carbon fibers for sample cleanup: application to multipesticide residue analysis in food commodities using a QuEChERS method.

Phenolic resin based activated carbon fibers (ACFs) were applied for the first time as a reversed-dispersive solid-phase extraction (r-DSPE) sorbent. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was applied to determine 26 pesticides (organophosphates, organochlorines, synthetic pyrethroids, and herbicides) in different complex matrices, including cauliflower, cucumber, banana, apple, wheat, and black gram. Different physicochemical characterization techniques were used to investigate the engineering and structural properties of the r-DSPE sorbent. All the chromatographic analyses were performed with a gas chromatograph equipped with an electron capture detector. The recoveries of all 26 pesticides were acceptable (70-120%), with relative standard deviations of less than 15%. The limit of detection and the limit of quantification were 1.13-5.48 ng/g and 3.42-16.60 ng/g, respectively. In the original QuEChERS method, primary secondary amine is extensively used as the r-DSPE sorbent in the cleanup process, but it is eightfold more expensive than the ACFs used in this study. Therefore, the modified QuEChERS method using ACFs during the cleanup process is more efficient, cheaper, and more robust to determine pesticides from different types of matrices, including vegetables, grains, and fruits, and ACFs could be used as a cost-effective alternative to primary secondary amine. Graphical Abstract Sample clean-up using PSA and ACF as r-DSPE sorbent in QuEChERS method.

Quick, easy, cheap, effective, rugged, and safe sample preparation approach for pesticide residue analysis using traditional detectors in chromatography: A review.

In pesticide residue analysis, relatively low-sensitivity traditional detectors, such as UV, diode array, electron-capture, flame photometric, and nitrogen-phosphorus detectors, have been used following classical sample preparation (liquid-liquid extraction and open glass column cleanup); however, the extraction method is laborious, time-consuming, and requires large volumes of toxic organic solvents. A quick, easy, cheap, effective, rugged, and safe method was introduced in 2003 and coupled with selective and sensitive mass detectors to overcome the aforementioned drawbacks. Compared to traditional detectors, mass spectrometers are still far more expensive and not available in most modestly equipped laboratories, owing to maintenance and cost-related issues. Even available, traditional detectors are still being used for analysis of residues in agricultural commodities. It is widely known that the quick, easy, cheap, effective, rugged, and safe method is incompatible with conventional detectors owing to matrix complexity and low sensitivity. Therefore, modifications using column/cartridge-based solid-phase extraction instead of dispersive solid-phase extraction for cleanup have been applied in most cases to compensate and enable the adaptation of the extraction method to conventional detectors. In gas chromatography, the matrix enhancement effect of some analytes has been observed, which lowers the limit of detection and, therefore, enables gas chromatography to be compatible with the quick, easy, cheap, effective, rugged, and safe extraction method. For liquid chromatography with a UV detector, a combination of column/cartridge-based solid-phase extraction and dispersive solid-phase extraction was found to reduce the matrix interference and increase the sensitivity. A suitable double-layer column/cartridge-based solid-phase extraction might be the perfect solution, instead of a time-consuming combination of column/cartridge-based solid-phase extraction and dispersive solid-phase extraction. Therefore, replacing dispersive solid-phase extraction with column/cartridge-based solid-phase extraction in the cleanup step can make the quick, easy, cheap, effective, rugged, and safe extraction method compatible with traditional detectors for more sensitive, effective, and green analysis.

Developments toward a low-cost approach for long-term, unattended vapor intrusion monitoring.

There are over 450 000 sites contaminated by chemicals in the US. This large number of contaminated sites and the speed of subsurface migration of chemicals pose considerable risk to nearby residences and commercial buildings. The high costs for monitoring around these sites stem from the labor involved in placing and replacing the passive sorbent vapor samplers and the resultant laboratory analysis. This monitoring produces sparse data sets that do not track temporal changes well. To substantially reduce costs and better track exposures, less costly, unattended systems for monitoring soil gases and vapor intrusion into homes and businesses are desirable to aid in the remediation of contaminated sites. This paper describes progress toward the development of an inexpensive system specifically for monitoring vapor intrusion; the system can operate repeatedly without user intervention with low detection limits (1 × 10(-9), or 1 part-per-billion). Targeted analytes include chlorinated hydrocarbons (dichloroethylene, trichloroethane, trichloroethylene, and perchloroethylene) and benzene. The system consists of a trap-and-purge preconcentrator for vapor collection in conjunction with a compact gas chromatography instrument to separate individual compounds. Chemical detection is accomplished with an array of chemicapacitors and a metal-oxide semiconductor combustibles sensor. Both the preconcentrator and the chromatography column are resistively heated. All components are compatible with ambient air, which serves as the carrier gas for the gas chromatography and detectors.

Cost effective, robust, and reliable coupled separation techniques for the identification and quantification of phospholipids in complex biological matrices: application to insects.

The quantification of phospholipid classes and the determination of their molecular structures are crucial in physiological and medical studies. This paper's target analytes are cell membrane phospholipids, which play an important role in the seasonal acclimation processes of poikilothermic organisms. We introduce a set of simple and cost-effective analytical methods that enable efficient characterization and quantification of particular phospholipid classes and the identification and relative distribution of the individual phospholipid species. The analytical approach involves solid-phase extraction and high-performance thin-layer chromatography, which facilitate the separation of particular lipid classes. The obtained fractions are further transesterified to fatty acid methyl esters and subjected to gas chromatography coupled to flame ionization detection, which enables the determination of the position of double bonds. Phospholipid species separation is achieved by high-performance liquid chromatography with mass spectrometry, which gives information about the headgroup moiety and attached fatty acids. The total content of each phospholipids class is assessed by phosphorus determination by UV spectrophotometry. The simultaneous analysis of phosphorus, fatty acid residues, and phospholipid species provides detailed information about phospholipid composition. Evaluation of these coupled methods was achieved by application to an insect model, Pyrrhocoris apterus. High correlation was observed between fatty acid compositions as determined by gas chromatography and high-performance liquid chromatography analysis.

On-line coupled reversed phase liquid chromatography and gas chromatography: a new sealing design for the TOTAD interface.

Total elimination of the eluent resulting from the pre-separation step is the critical point when coupling LC to GC. As a helium flow is applied during transfer to eliminate the solvent, the interface used for linking the two chromatographic systems must be properly sealed to prevent gas leaks and to achieve an effective evaporation of the eluent. The aim of this work was to improve the performance of the Through Oven Transfer Adsorption Desorption (TOTAD) interface to remove the eluent coming from LC by modifying the way in which the injector sealing system is held in place. As with the original design, the new approach makes it possible to transfer high volumes at a high rate, but the proposed modification also simplifies the experimental work because the displacement risk of the sealing system is reduced. Analyses of an ester mixture by RPLC-GC were performed to confirm the applicability of the system modification. In this work, volumes of up to 5 ml, at flow rates as high as 2 ml/min, were transferred from LC to GC with almost complete solvent removal even when working in reversed phase mode in the LC step.

Air-assisted liquid-liquid microextraction used for the rapid determination of organophosphorus pesticides in juice samples.

A novel and simple air-assisted liquid-liquid microextraction (AALLME) is introduced to analyze the organophosphorus pesticide (OPP) residues in fruit juice samples, using the gas chromatography-flame photometric detection (GC-FPD). In this method, fine extraction solvent drops are rapidly formed and dispersed into the aqueous samples, by using a syringe to withdraw and push-out the mixture of aqueous sample solution and extraction solvent several times. The parameters affecting the extraction efficiency were investigated including the type and volume of the extraction solvent, salt addition, extraction times, and pH. Under optimized conditions, the method showed good linearities with the correlation coefficients (γ) higher than 0.9988, and the sensitivity with the limits of detection (LODs) between 0.02µgL(-1) and 0.6µgL(-1). The method was applied to determine the OPP residues in juice samples and the recoveries were ranged from 79% to 113% with relative standard deviations (RSDs) of 0.4-9.9%. The feasibility of the method in real samples was proved.

Two-dimensional gas chromatographic analysis of ambient light hydrocarbons.

Ambient level hydrocarbons lighter than C6 were analyzed by the Deans switch-modulated comprehensive two-dimensional gas chromatography (GC×GC) method with flame ionization detection (FID). A thermal desorption (TD) device built in-house connects the GC×GC system to pre-concentrate the target compounds at ambient levels prior to GC analysis. Because the conventional orthogonality based on polarity difference for normal GC×GC separation does not provide sufficient retention for the target compounds of extremely high volatility, the orthogonality of non-polar vs. adsorptive force was adopted instead. The system employed a 100% polydimethyl siloxane column serving as the first-dimension column to provide separation based on dispersive interaction, with a short PLOT column serving as the second-dimension column to provide the needed retention based on gas-solid adsorption interactions. The shortest possible length of the PLOT column was tested to minimize the modulation period (PM) and wraparound and, at the same time, to maintain the desired resolution. The tests led to the final optimal parameters of 1.1m for the PLOT column length, 9s for the PM, 0.013 for the modulation duty cycle (DC) and a modulation ratio (MR) of 3.7 with minimal wraparound. Important criteria for quality assurance of precision and linearity are reported. The low cost and ease of construction and operation make the in-house Deans switch TD-GC×GC-FID system practical and useful for the analysis of light hydrocarbons in urban or industrial environments.

Rapid determination of hydrogen peroxide in pulp bleaching effluents by headspace gas chromatography.

A headspace gas chromatographic (HS-GC) method has been developed for the determination of residual hydrogen peroxide in pulp bleaching effluents. The method is based on the reaction of hydrogen peroxide and permanganate in an acidic medium (0.1 mol/L), in which hydrogen peroxide is quantitatively converted to oxygen within 10 min at 60°C in a sealed headspace sample vial. The released oxygen is then determined by GC equipped with a thermal conductivity detector. The method is robust, sensitive, and accurate, with reproducibility characterized by a relative standard deviation of <0.5%, a sensitivity whose limit of quantification (LOQ) is 0.96 µmol, and a demonstrated recovery ranging from 98 to 103%. Further, the method is simple, rapid, and automated.

Rapid analysis of organochlorine and pyrethroid pesticides in tea samples by directly suspended droplet microextraction using a gas chromatography-electron capture detector.

A simple and efficient directly suspended droplet microextraction (DSDME) has been developed to extract and pre-concentrate organochlorine and pyrethrin pesticides from tea samples prior to analysis by a gas chromatography-electron capture detector (GC-ECD). The optimal experimental conditions of DSDME were: 100 µL isooctane exposed for 15 min to 5 mL of the tea aqueous sample stirred at 1100 rpm. For most of the target analytes, the optimal pretreatment of DSDME processes led to no significant interference of tea matrices. The approach was applied to the determination of organochlorine and pyrethroid pesticides in tea samples, with a linearity range of 0.0005-2 µg/mL. The relative recoveries of all the pesticides ranged between 80.0% and 120.8% with relative standard deviations (RSDs) in the range of 0.8-19.9% (n=5). The limits of detections (LODs) ranged between 0.04 and 1 µg/L for all the target pesticides.

A monolithically-integrated µGC chemical sensor system.

Gas chromatography (GC) is used for organic and inorganic gas detection with a range of applications including screening for chemical warfare agents (CWA), breath analysis for diagnostics or law enforcement purposes, and air pollutants/indoor air quality monitoring of homes and commercial buildings. A field-portable, light weight, low power, rapid response, micro-gas chromatography (µGC) system is essential for such applications. We describe the design, fabrication and packaging of µGC on monolithically-integrated Si dies, comprised of a preconcentrator (PC), µGC column, detector and coatings for each of these components. An important feature of our system is that the same mechanical micro resonator design is used for the PC and detector. We demonstrate system performance by detecting four different CWA simulants within 2 min. We present theoretical analyses for cost/power comparisons of monolithic versus hybrid µGC systems. We discuss thermal isolation in monolithic systems to improve overall performance. Our monolithically-integrated µGC, relative to its hybrid cousin, will afford equal or slightly lower cost, a footprint that is 1/2 to 1/3 the size and an improved resolution of 4 to 25%.

Measurement of ethanol in gaseous breath using a miniature gas chromatograph.

We designed and built a novel, miniature gas chromatograph (mGC) to use exhaled breath to estimate blood ethanol concentrations that may offer GC quality sensitivity and specificity, but with portability, reduced size, and decreased cost. We hypothesized that the mGC would accurately estimate the serum ethanol concentration using exhaled breath. Human subjects (n = 8) were dosed with ethanol employing the Widmark criteria, targeting a blood concentration of 0.08 g/dL. Serum and breath samples were collected concurrently over an hour. Ethanol concentrations in serum were measured using a CLIA-approved laboratory. Ethanol concentrations in conventional breath were assayed using a calibrated mGC or Intoxilyzer 400PA. Data were analyzed using Bland-Altman analysis using serum concentrations as a "gold standard". For the mGC, the regression line (correlation coefficient), bias, and 95% limits of agreement were y = 1.013x - 0.009 (r = 0.91), -0.008 g/dL, and -0.031 to 0.016 g/dL, respectively, for 30 specimens. For the Intoxilyzer 400PA, the regression line (correlation coefficient), bias, and 95% limits of agreement were y = 0.599x + 0.008 (r = 0.86), -0.024 g/dL, and -0.049 to 0.002 g/dL, respectively, for 71 specimens with a large magnitude effect. We concluded that the mGC, using exhaled breath, performed well to estimate the serum ethanol concentrations.

Determination of beer aroma compounds using headspace solid-phase microcolumn extraction.

A rapid sampling technique for the analysis of beer aroma compounds is described. The headspace (10 ml) is passed through the microcolumn filled with 5mg of Tenax TA and thermally desorbed in a modified GC inlet (modification is described). Eight compounds (from acetaldehyde to 2-phenylethanol) in four beer samples were analyzed. The correlation coefficients (r(2)), repeatability (RSD) and limits of detection (LOD) were 0.9973-0.9994, 2.1-6.9% and 0.00002-0.13 mg/l, respectively. The methodology can be useful for routine beer sample analysis.

Determination of trihalomethanes in soil matrices by simplified quick, easy, cheap, effective, rugged and safe extraction and fast gas chromatography with electron capture detection.

A method based on QuEChERS extraction is proposed for the determination of trihalomethanes (chloroform, bromodichloromethane, dibromocloromethane and bromoform) in soil samples. The new version of QuEChERS adapted to soil samples consists of liquid extraction with ethyl acetate, the addition of water to moisten the samples, salting-out partitioning of the water with anhydrous MgSO4, and direct injection of the organic extract, obtained after the centrifugation step, into the gas chromatograph. This simplified extraction procedure maintains the advantages of the original method and avoids some steps, making the final procedure simpler, faster, and cheaper, with the consequent reduction in errors associated with sample manipulation. The experimental conditions of the analytical method, based on fast gas chromatography (FGC) and micro-electron capture detection (microECD), were optimized. The column and oven program used allowed fast separation of the compounds in less than 4 min and the total analysis cycle time was as short as 10 min. The existence of a matrix effect was checked and the analytical conditions of the method were studied in a fortified garden soil sample. The highly sensitive and selective detector used afforded to detection limits in the order of ng/kg for the target compounds. To validate the proposed method two certified reference materials (CRMs) were analyzed.

Multi-walled carbon nanotubes as efficient solid-phase extraction materials of organophosphorus pesticides from apple, grape, orange and pineapple fruit juices.

Multi-walled carbon nanotubes (MWCNTs) have been used for the first time as solid-phase extraction (SPE) sorbents for the extraction of eight organophosphorus pesticides (i.e. ethoprophos, diazinon, chlorpyriphos-methyl, fenitrothion, malathion, chlorpyriphos, fenamiphos and buprofezin) from different commercial fruit juices (i.e. apple, grape, orange and pineapple). The developed method, which involves SPE and direct gas chromatography with nitrogen phosphorus detection analysis, is very fast, simple and cheap: only 1:1 dilution with Milli-Q water and pH adjustment to 6.0 of 10 mL of juice is necessary prior to a quick MWCNTs-SPE procedure that used only 40 mg of stationary phase (MWCNTs of 10-15 nm o.d., 2-6 nm i.d. and 0.1-10 microm length). Mean recovery values were above 73% for all the pesticides and fruit juices (between 77 and 101% for apple juice, 75 and 103% for grape juice, 73 and 103% for orange juice and 73 and 93% for pineapple juice) with a relative standard deviation (RSD) lower than 8.5% in all cases. Matrix matched calibration was carried out for each sample matrix since statistical differences between the calibration curves constructed is pure solvent and in the reconstructed juice extracts were found. Limits of detection ranged between 1.85 and 7.32 microg/L (which also represents LODs between 1.85 and 7.34 microg/kg) well below the European Union maximum residue limits for the raw fruits. The proposed method, which is demonstrated to be quick, cheap, accurate and highly selective, was also applied to the analysis of this group of pesticides in several commercial juices in which none of the selected pesticides were found.

Dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection.

A simple dispersive liquid-liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 microL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8+/-0.5 microL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 microL (for GC/ECD) or 2 microL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005-0.05microgL(-1) for GC/ECD and was 0.005-0.047 microgL(-1) for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/ECD and was from 0.02 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/MS.

GC x GC-ECD: a promising method for the determination of dioxins and dioxin-like PCBs in food and feed.

There is a need for cost-efficient alternatives to gas chromatography (GC)-high-resolution mass spectrometry (HRMS) for the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in food and feed. Comprehensive two-dimensional GC-micro electron capture detection (GC x GC-microECD) was tested and all relevant (according to the World Health Organisation, WHO) PCDD/Fs and PCBs could be separated when using a DB-XLB/LC-50 column combination. Validation tests by two laboratories showed that detectability, repeatability, reproducibility and accuracy of GC x GC-microECD are all statistically consistent with GC-HRMS results. A limit of detection of 0.5 pg WHO PCDD/F tetrachlorodibenzo-p-dioxin equivalency concentration per gram of fish oil was established. The reproducibility was less than 10%, which is below the recommended EU value for reference methods (less than 15%). Injections of vegetable oil extracts spiked with PCBs, polychlorinated naphthalenes and diphenyl ethers at concentrations of 200 ng/g showed no significant impact on the dioxin results, confirming in that way the robustness of the method. The use of GC x GC-microECD as a routine method for food and feed analysis is therefore recommended. However, the data evaluation of low dioxin concentrations is still laborious owing to the need for manual integration. This makes the overall analysis costs higher than those of GC-HRMS. Further developments of software are needed (and expected) to reduce the data evaluation time. Combination of the current method with pressurised liquid extraction with in-cell cleanup will result in further reduction of analysis costs.

Headspace single-drop microextraction and GC-ECD determination of chlorpyrifos-ethyl in rat liver.

The present work describes a headspace single-drop microextraction (HS-SDME) method in conjunction with gas chromatography electron capture detection (GC-ECD) for the determination of an organophosphate insecticide, chlorpyrifos-ethyl (CPF), in rat liver. Sample preparation included tissue homogenization with methanol in the presence of anhydrous sodium sulfate in order to isolate CPF from the matrix, followed by dilution with 10 mL of 0.1 M H(2)SO(4) and headspace microextraction to a 2-microL drop of 1-octanol. The main factors affecting extraction efficiency were optimized [temperature 90 degrees C, preheating and extraction times of eight and six minutes, respectively, 2 g of (NH(4))(2)SO(4), stirring rate of 1000 rpm, 200 microL of methanolic extract]. The method allows for the separation and quantitation of residue levels of CPF in the livers of rats exposed orally to that insecticide. Using internal standardization (with chlorpyrifos-methyl used as an internal standard), the linearity of the method was demonstrated in the range 10-2500 ng g(-1) with a correlation coefficient R > 0.996 and a satisfactory level of precision (RSD 3.85%, n = 6). Moreover, the results obtained with the new method do not differ from those obtained with the conventional residue method used in our laboratory. The feasibility of this HS-SDME approach as an equivalent analytical method for the determination of CPF in rat liver that possesses advantages such as low cost, low solvent consumption and high throughput was confirmed.

Targeted multidimensional gas chromatography for the quantitative analysis of suspected allergens in fragrance products.

Two approaches are described and compared for the analysis of suspected allergens (SAs) in fragrance products, which are defined by the Scientific Committee of Cosmetics and Non-Food Products (SCCNFP). The first consists of a comprehensive two-dimensional gas chromatography (GC x GC) experiment using both a "conventional" non-polar/polar column combination and an "inverse" polar/non-polar column set. The second approach uses a targeted multidimensional gas chromatography (MDGC) system employing a Deans type pneumatic switch and a longitudinally modulated cryogenic system (LMCS). It was found that the conventional and inverse column sets complement each other well, providing identification of SAs present. Compounds well retained on the second dimension of one column set were the first to be eluted from the other. In some instances SAs co-eluting with matrix components on the second dimension for a given column set were clearly resolved on the other, although this has the disadvantage of requiring two analytical runs. Targeted MDGC with a non-polar/polar column set, successfully separated all SAs identified within a fragrance product. The instrument is set up in a similar fashion to a GC x GC system though with longer second dimension ((2)D) column, a cryogenic trap at the beginning of the second column, and a pneumatic switch coupling both columns. The data are easier to process than for a GC x GC experiment. The targeted MDGC method has the capacity to deliver far greater efficiency to targeted regions of a primary separation than a GC x GC experiment, whilst still maintaining overall run times similar to those of a conventional one-dimensional (1D) GC experiment. Cryogenic focussing at the beginning of the (2)D column delivers enhanced sensitivity, accurate (2)D retention times and narrow peak widths; these are responsible for an increased resolution obtained from the fast, relatively short (approximately 5 m) (2)D column. The two column set GC x GC analysis provided a quick and effective means to qualitatively determine the presence of six SAs in a commercially available air freshener, however all were not adequately resolved from matrix components. In contrast, quantitation was straightforward using the targeted MDGC method.

Gas chromatographic detection of Mycobacterium tuberculosis complex in pure cultures from respiratory specimens.

It is important to identify mycobacteria to the species level in order to establish their clinical significance and to take the appropriate therapeutical decision. Biochemical tests on primary cultures take time (3-6 weeks) until the report of results; that's why more rapid techniques are needed. We have used gas chromatography with flame-ionisation detection (GC-FID) as an alternative identification method for 53 mycobacterial strains isolated from respiratory specimens. We have extracted fatty acids from whole mycobacterial cells, then derivatized them into methylesters, detectable by GC-FID. All the strains were identified as M. tuberculosis complex (MTC), using the Microbial Identification System (MIS) software. The specificity of the identification by GC-FID of MTC is 100%. In conclusion, pulmonary mycobacteriosis are dominated by MTC; GC-FID is a rapid and accurate method for the identification of MTC.

Determination of organochlorine and organophosphate pesticide residues in fruits, vegetables and sediments.

A method is described for the determination of organochlorine and organophosphate pesticide residues in fruits, vegetables and sediments. The concentrated solvent extract was sealed in a polymeric membrane tube, dialysed in cyclohexane and the solvent replaced with hexane. The organophosphates were analysed on a specific thermionic detector without further clean-up. For the organochlorine pesticides the extract was eluted through 3 g of alumina and analysed on GC/ECD. The clean-up for sediment extract was carried out on a 10 g alumina column with 100 mL hexane containing 5% acetone and the eluate was concentrated to 5 mL. The detection limit for organophosphates on a 40 g sample and a final volume of 10 mL was on the average 0.01 mg/kg. The detection limit for organochlorine pesticides, with the final volume of 25 mL, was 0.005 mg/kg for all pesticides except for p,p'-DDT and endosulfan sulphate, which was 0.01 mg/kg. The detection limit for organochlorine pesticides in sediment, with the final volume of 2 mL, was less than 1 microgram/kg and for organophosphate pesticides less than 10 micrograms/kg when the final volume was made to 0.5 mL. At the detection limits the method produced a very high coefficient of variation for both organochlorine and organophosphate pesticides.