Multiresidue analysis of pesticides in soil by supercritical fluid extraction/gas chromatography with electron-capture detection and confirmation by gas chromatography-mass spectrometry

Solid-phase extraction using chloropropyl functionalized sol-gel hybrid sorbent for simultaneous determination of organophosphorus pesticides in selected fruit samples

A new sol-gel hybrid methyltrimethoxysilane-chloropropyltriethoxysilane was prepared as sorbent for solid-phase extraction. The extraction efficiency of the prepared sol-gel hybrid methyltrimethoxysilane-chloropropyltriethoxysilane was assessed by using three selected organophosphorus pesticides, namely, chlorpyrifos, profenofos, and malathion. Gas chromatography-mass spectrometry was used for detection of organophosphorus pesticides. Several vital parameters were optimized to identify the best extraction conditions. Under the optimum extraction conditions, solid-phase extraction-methyltrimethoxysilane-chloropropyltriethoxysilane method showed good linearity range (0.05-1 μg/mL) with coefficient of determination more than 0.995. The limits of detection obtained were in the range of 0.01-0.07 μg/mL and limits of quantification ranging from 0.03 to 0.21 μg/mL. The limits of detection obtained for the developed method were 2.3-6.5× lower than the limits of detection of commercial octadecyl silica sorbent. Real samples analysis was carried out by applying the developed method on red apple and purple grape samples. The developed method exhibited good recoveries (88.33-120.7%) with low relative standard deviations ranging from 1.6 to 3.3% compared to commercial octadecyl silica sorbent, which showed acceptable recoveries (70.3-100.2%) and relative standard deviations (6.3-8.8%). The solid-phase extraction-methyltrimethoxysilane-chloropropyltriethoxysilane method is presented as an alternative extraction method for determination of organophosphorus pesticides.

Distribution of pesticides in agricultural and urban soils of Brazil: a critical review

The extensive use of pesticides leads to soil contamination and is harmful to environmental health. Brazil is considered the world's largest consumer of pesticides; however, there is no published review of the distribution and concentration of pesticides in the Brazilian soils. Thus, the objective of this study was to analyze the occurrence of pesticide residues in Brazilian soils through a systematic review of the data obtained from the official records of government agencies and scientific literature. Further, this review aims to estimate the risk quotient using the data extracted from these studies and compare it with the values from current legislation. The studies on pesticides were selected and screened, out of which 21 scientific articles were included in this review. The studies highlighted that 55 pesticides were detected in the soils in Brazil. Of these, 58% belonged to the chemical class of organochlorines and their concentration ranged from 0.0002-1243.68 mg kg-1. DDT (0.00002-1243.68 mg kg-1), HCH (0.00007-962.00 mg kg-1) and diuron (0.0031-4.16 mg kg-1) contributed to highest pesticide concentrations in soil. Residential soils had higher pesticide concentrations and greater risk factors than the agricultural soils. Moreover, 20% of the studies detected mixtures containing more than 10 types of pesticides. This study concluded that the specific scenarios evaluated by the reviewed studies do not reflect the current pesticide use and contamination in Brazil and there is a need for more information related to pesticide contamination in soils.

Phytoremediation and Bioremediation of Pesticide-Contaminated Soil

Management and destruction of obsolete pesticides and the remediation of pesticide-contaminated soil are significant global issues with importance in agriculture, environmental health and quality of life. Pesticide use and management have a history of problems because of insufficient knowledge of proper planning, storage, and use. This manuscript reviews recent literature with an emphasis on the management of obsolete pesticides and remediation of pesticide-contaminated soil. The rhizosphere of plants is a zone of active remediation. Plants also take up contaminated water and remove pesticides from soil. The beneficial effects of growing plants in pesticide-contaminated soil include pesticide transformation by both plant and microbial enzymes. This review addresses recent advances in the remediation of pesticide-contaminated soil with an emphasis on processes that are simple and can be applied widely in any country.

Electropolymerized MIP with MWCNTs on Stir Bar Using Multivariate Optimization for Tetradifon Detection in Date

BACKGROUND

Multi-walled carbon nanotubes (MWCNT) adjunct to molecularly imprinted polymers (MIP) have advantages of the large surface area of nanoparticles and selectivity of MIPs for selective extraction of tetradifon as a widely used pesticide in date palm.

OBJECTIVES

The main aims were the use of experimental design, electrochemical synthesis and ultra-high performance liquid chromatography (UHPLC) to develop a simple, reliable and precise pesticide residue analysis method as an important aspect of food and drug quality control for the determination of tetradifon in date palms.

METHODS

An MIP in the presence of MWCNT was synthesized by cyclic voltammetric technique on a steel rod to produce a composite of MIP-MWCNTs for stir bar extraction of tetradifon residue in date samples. The experimental design was used to optimize MIPMWCNT composite synthesis through the screening of eight variables. The composite was characterized by scanning electron microscopy (SEM). Tetradifon was determined in extracted samples by UHPLC under optimum conditions.

RESULTS

A very thin film was made by MIP-MWCNT coated on a steel rod which was repeatable and had good adhesion and persistence. The detection limit (LOD) and the quantification limit (LOQ) of the method were measured as 16 and 49 ng/ml, respectively. Average recovery of tetradifon at the two spiked levels was observed to be as low as 86.5% to 90.7% (RSD from 0.79% to 1.04%).

CONCLUSION

The low cost, high selectivity, good reproducibility, acceptable intra and inter day precision and accuracy developed method were successfully applied to determine tetradifon residue in date samples purchased from a local market.

Multipesticide residue levels in UHT and raw milk samples by GC-μECD after QuEChER extraction method

In the present study, milk samples including raw and ultra-high temperature (UHT) processed milk were analyzed for pesticide residue levels, including five pesticides, viz chloripyrifos, endosulfan (α and β), profenofos and bifenthrin by gas chromatography microelectron capture detector (GC-μECD) after extraction by QuEChERS method. Further confirmation of the pesticide residue was done by GC-MS. The pesticide residual level in raw and UHT milk samples (n = 70) was determined in the range of 0.1-30 μg L(-1). All UHT processed milk samples contain pesticide residues within permissible limit set by the World Health Organization (WHO); however, among raw milk samples, chloripyrifos (12 %), α (24 %), and β (14 %) endosulfan were found above the maximum residue limit (MRL). The estimated daily intake (EDI) of these four pesticide residues were also calculated as 1.32, 16.16, 5.30, 10.20, and 9.93 μg kg(-1) body weight for chloripyrifos, endosulfan α, profenofos, endosulfan β, and bifenthrin, respectively. It is concluded that the raw milk samples showed higher prevalence of pesticide residues as compared to UHT processed milk. Graphical abstract Determination of pesticide residues in dairy milk by GC-μECD after QuEChERS extraction method.

Multivariate optimization for extraction of pyrethroids in milk and validation for GC-ECD and CG-MS/MS analysis

A simple and inexpensive method based on solvent extraction followed by low temperature clean-up was applied for determination of seven pyrethroids residues in bovine raw milk using gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) and gas chromatography with electron-capture detector (GC-ECD). Sample extraction procedure was established through the evaluation of seven different extraction protocols, evaluated in terms of analyte recovery and cleanup efficiency. Sample preparation optimization was based on Doehlert design using fifteen runs with three different variables. Response surface methodologies and polynomial analysis were used to define the best extraction conditions. Method validation was carried out based on SANCO guide parameters and assessed by multivariate analysis. Method performance was considered satisfactory since mean recoveries were between 87% and 101% for three distinct concentrations. Accuracy and precision were lower than ±20%, and led to no significant differences (p < 0.05) between results obtained by GC-ECD and GC-MS/MS techniques. The method has been applied to routine analysis for determination of pyrethroid residues in bovine raw milk in the Brazilian National Residue Control Plan since 2013, in which a total of 50 samples were analyzed.

Optimization of supercritical fluid extraction method for detection of fluquinconazole and tetraconazole in soil using gas chromatography and confirmation using GC-MS: application to dissipation kinetics

The aim of this study was to establish an analytical method to detect fluquinconazole and tetraconazole in soil using supercritical fluid extraction (SFE) and gas chromatography (GC). The optimal extraction conditions for SFE were: temperature, 60 °C; pressure, 280 kg/cm(2) ; extraction time, 50 min; and a 10% modifier ratio. The linearity of the calibration curves was good and yielded a determination coefficient (R(2) ) ≥ 0.995. The soil samples were fortified with known quantities of the analytes at three different concentrations (0.01, 0.02 and 0.1 µg/g for fluquinconazole; 0.05, 0.1 and 0.5 µg/g for tetraconazole), and the recoveries ranged between 83.7 and 94.1%. The intra- and inter-day relative standard deviations were 1.3-10.6 and 2.2-11.9% for fluquinconazole and tetraconazole, respectively. The limit of detection and limit of quantitation were 0.002 and 0.01 µg/g for fluquinconazole and 0.01 and 0.05 for tetraconazole, respectively. The method was successfully applied to the analysis of soil residues collected from an onion field. The results show that a combination of SFE and GC can be used as an environmentally friendly technique to detect fungicides in soil.

Pesticide residues in Portuguese strawberries grown in 2009-2010 using integrated pest management and organic farming

Pesticides are among the most widely used chemicals in the world. Because of the widespread use of agricultural chemicals in food production, people are exposed to low levels of pesticide residues through their diets. Scientists do not yet have a total understanding of the health effects of these pesticide residues. This work aims to determine differences in terms of pesticide residue content in Portuguese strawberries grown using different agriculture practices. The Quick, Easy, Cheap, Effective, Rugged, and Safe sample preparation method was conducted and shown to have good performance for multiclass pesticides extraction in strawberries. The screening of 25 pesticides residue was performed by gas chromatography-tandem mass spectrometry. In quantitative validation, acceptable performances were achieved with recoveries of 70-120 and <12 % residual standard deviation for 25 pesticides. Good linearity was obtained for all the target compounds, with highly satisfactory repeatability. The limits of detection were in the range of 0.1-28 μg/kg. The method was applied to analyze strawberry samples from organic and integrated pest management (IPM) practices harvested in 2009-2010. The results showed the presence of fludioxonil, bifenthrin, mepanipyrim, tolylfluanid, cyprodinil, tetraconazole, and malathion when using IPM below the maximum residue levels.

C18 functionalized graphene oxide as a novel coating for solid-phase microextraction

A novel C18 functionalized graphene oxide (GO) coated solid-phase microextraction fiber was prepared by a novel protocol. Based on the strong van der Waals interaction present in GO and abundant oxygenous groups in GO sheets, a simple layer-by-layer self-assembly method was used in the preparation process and then C18 was successfully self-assembled on GO via C-O-Si bonding. Coupled with gas chromatography, extraction performance of the fiber was tested with polycyclic aromatic hydrocarbons (PAHs) as model analytes. The fiber not only exhibited excellent extraction efficiency and selectivity, but also showed many advantages including high rigidity, long service life and well stability toward organic solvent, acidic and alkali solutions, and high temperature. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 7.26 and 17.25%, respectively. The detection limits to the PAHs were less than 0.08 μg L(-1) and the calibration curves were linear in a wide range for all analytes. The as-established Solid-phase microextraction GC method was also successfully used for determination of PAHs in two real water samples.

Mixtures of environmental pollutants: effects on microorganisms and their activities in soils

Soil is the ultimate sink for most contaminants and rarely has only a single contaminant. More than is generally acknowledge, environmental pollutants exist as mixtures (organic-organic, inorganic-inorganic, and organic-inorganic). It is much more difficult to study chemical mixtures than individual chemicals, especially in the complex soil environment. Similarly, understanding the toxicity of a chemical mixture on different microbial species is much more complex, time consuming and expensive, because multiple testing designs are needed for an increased array of variables. Therefore, until now, scientific enquiries worldwide have extensively addressed the effects of only individual pollutants toward nontarget microorganisms. In this review, we emphasize the present status of research on (i) the environmental occurrence of pollutant mixtures; (ii) the interactions between pollutant mixtures and ecologically beneficial microorganisms; and (iii) the impact of such interactions on environmental quality. We also address the limitations of traditional cultivation based methods for monitoring the effects of pollutant mixtures on microorganisms. Long-term monitoring of the effects of pollutant mixtures on microorganisms, particularly in soil and aquatic ecosystems, has received little attention. Microbial communities that can degrade or can degrade or can develop tolerance to, or are inhibited by chemical mixtures greatly contribute to resilience and resistance in soil environments. We also stress in this review the important emerging trend associated with the employment of molecular methods for establishing the effects of pollutant mixtures on microbial communities. There is currently a lack of sufficient cogent toxicological data on chemical mixtures for making informed decision making in risk assessment by regulators. Therefore, not only more toxicology information on mixtures is needed but also there is an urgent need to generate sufficient, suitable, and long-term modeling data that have higher predictability when assessing pollutant mixture effects on microorganisms. Such data would improve risk assessment at contaminated sites and would help devise more effective bioremediation strategies.

An overview of sample preparation and extraction of synthetic pyrethroids from water, sediment and soil

The latest developments in sample preparation and extraction of synthetic pyrethroids from environmental matrices viz., water, sediment and soil were reviewed. Though the synthetic pyrethroids were launched in 1970s, to the best of authors' knowledge there was no review on this subject until date. The present status and recent advances made during the last 10 years in sample preparation including conservation and extraction techniques used in determination of synthetic pyrethroids in water, sediment and soil were discussed. Pre- and post-extraction treatments, sample stability during extraction and its influence upon the whole process of analytical determination were covered. Relative merits and demerits including the green aspects of extraction were evaluated. The current trends and future prospects were also addressed.

Removal of dioxins and dioxin-like PCBs from fish oil by countercurrent supercritical CO2 extraction and activated carbon treatment

It has been known that fish oils are prone to contamination by polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DL-PCBs). In this study, the removal of contaminants from fish oil by countercurrent supercritical CO(2) extraction (CC-SCE) and activated carbon treatment was investigated. Fish oil was treated by CC-SCE at 70 degrees C and 30MPa and with a CO(2)/oil ratio of 72; this resulted in a 93% reduction in the sum of PCDDs, PCDFs and DL-PCBs concentration level by and 85% reduction in toxic equivalency (TEQ). CC-SCE uses 40% less CO(2) and yields 30% more refined oil than semi-batch-type processes. Subsequent treatment by activated carbon reduced the concentration level by 94% and TEQ by 93%. CC-SCE is effective for the removal of DL-PCBs, whereas activated carbon treatment is effective for the removal of PCDD/Fs. These results reveal that the combination of CC-SCE and activated carbon treatment is applicable to the removal of PCDD/Fs and DL-PCBs from fish oil.

Multiresidue analysis of four pesticide residues in water dropwort (Oenanthe javanica)via pressurized liquid extraction, supercritical fluid extraction, and liquid–liquid extraction and gas chromatographic determination

The primary objective of this study was to simultaneously analyze the residues of the most commonly used pesticides, chlorpyrifos-methyl, endosulfan, EPN, and iprodione in the water dropwort, via accelerated solvent extraction (ASE), supercritical fluid extraction (SFE), and conventional solvent extraction (LLE) techniques. Residue levels were determined using GC with electron-capture detection (GC-ECD). The confirmation of pesticide identity was performed by GC-MS in a selected ion-monitoring (SIM) mode. In none of the ASE and SFE techniques were the extraction conditions optimized. Rather, the experimental variables were predicated on the author's experience. The ECD response for all pesticides was linear in the studied range of concentrations of 0.005-5.0 ppm, with correlation coefficients in excess of 0.9991. At each of the two studied fortification levels, the pesticides yielded recoveries in excess of 72% with RSDs between 1 and 19%. The LODs were achieved at a range of levels from 0.001 to 0.063 ppm, depending on the pesticide utilized. The LOQs, which ranged from 0.003 to 0.188 ppm, were lower than the maximum residue limits (MRLs) authorized by the Korean Food and Drug Administration (KFDA). All of the methods were applied successfully to the determination of pesticide residues in the real samples. It could, therefore, be concluded that any of the techniques utilized in this investigation might prove successful, given that the applied extraction conditions are wisely chosen.

Method for determination of acephate, methamidophos, omethoate, dimethoate, ethylenethiourea and propylenethiourea in human urine using high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry

Because of increasing concern about widespread use of insecticides and fungicides, we have developed a highly sensitive analytical method to quantify urine-specific urinary biomarkers of the organophosphorus pesticides acephate, methamidophos, omethoate, dimethoate, and two metabolites from the fungicides alkylenebis-(dithiocarbamate) family: ethylenethiourea and propylenethiourea. The general sample preparation included lyophilization of the urine samples followed by extraction with dichloromethane. The analytical separation was performed by high-performance liquid chromatography (HPLC), and detection by a triple quadrupole mass spectrometer with and atmospheric pressure chemical ionization source in positive ion mode using multiple reaction monitoring and tandem mass spectrometry (MS/MS) analysis. Two different Thermo-Finnigan (San Jose, CA, USA) triple quadrupole mass spectrometers, a TSQ 7,000 and a TSQ Quantum Ultra, were used in these analyses; results are presented comparing the method specifications of these two instruments. Isotopically labeled internal standards were used for three of the analytes. The use of labeled internal standards in combination with HPLC-MS/MS provided a high degree of selectivity and precision. Repeated analysis of urine samples spiked with high, medium and low concentration of the analytes gave relative standard deviations of less than 18%. For all compounds the extraction efficiency ranged between 52% and 63%, relative recoveries were about 100%, and the limits of detection were in the range of 0.001-0.282 ng/ml.

Large volume cold on-column injection for gas chromatography-negative chemical ionization-mass spectrometry analysis of selected pesticides in air samples

A new gas chromatographic method is described for the analysis of fungicides captan, captafol, and folpet from organic extracts of air samples using large volume injection (LVI) via a cold on-column (COC) inlet coupled with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). Although standard split/splitless injection due to high injection port temperatures (>225 degrees C) have been shown to degrade these thermally labile fungicides, COC injection minimizes degradation. Insecticides such as chlorpyrifos and diazinon were also examined to show added selectivity. By using a solvent vapor exit with the COC inlet, injection volumes of 10-100 microL can be made to lower detection levels. GC-NCI-MS was compared to GC-electron impact ionization-mass spectrometry for each pesticide using LVI-COC injections and was found to be 2-80 times more sensitive, depending on the pesticide. Method detection limit (MDL) values with 100 microL injections were 2.5 microg L-1 for captan, folpet, and diazinon, 5.0 microg L-1 captafol, and 1.0 microg L-1 for chlorpyrifos, with the normal working range examined for sample analysis from MDL to 100 microg L-1. Detection of all pesticides except captafol, used only in the United States but not Canada, was demonstrated from air samples taken from Abbotsford, British Columbia, Canada.

Assessment of priority pesticides, degradation products, and pesticide adjuvants in groundwaters and top soils from agricultural areas of the Ebro river basin

Gas chromatography-mass spectrometry (GC/MS) was employed for the determination of 30 widely used pesticides including various transformation products and alkylphenols in water and agricultural soils with the aim of assessing the impact of these compounds in agricultural soils and the underlying aquifer. The extraction, clean-up, and analytical procedures were optimized for both water and soil samples to provide a highly robust method capable of determining target analytes at the ppb-ppt level with high precision. For water samples, different solid-phase extraction cartridges and conditions were optimized; similarly, pressurized liquid extraction conditions were tested to provide interference-free extracts and high sensitivity. Instrumental LODs of 3-4 pg were obtained. The multi-residue extraction procedures were applied to the analysis of groundwaters and agricultural soils from the Ebro river basin (NE Spain). Most ubiquitous herbicides detected were triazines but some acetanilides and organophosphorus pesticides were also found; the pesticide additive tributylphosphate was found in all water samples. Levels varied between 0.57 and 5.37 microg/L in groundwater, whereas nonylphenol was the sole compound detected in soil. Alkylphenols are used as adjuvants in pesticide formulations and are present in sludges employed as soil fertilizers. Occurrence was found to be similar to other environmental studies.

Experimental study on the removal of dioxins and coplanar polychlorinated biphenyls (PCBS) from fish oil

Recently, it has been found that fish oils contain a high proportion of contaminants, namely, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (cPCBs). In this study, the removal of contaminants from fish oil by supercritical CO2 extraction (SCE) and by using adsorbents (0.13 wt % of oil) was investigated. Dioxins and cPCBs were extracted from fish oil by SCE at a temperature of 60 degrees C and a pressure of 28 MPa, and the removal efficiencies for PCDDs and PCDFs were in the range of 15-90% and those for cPCBs were in the range of 70-90%. However, 40% of the oil was extracted simultaneously with contaminants. On the adsorbent treatment, activated carbon showed high efficiency, and the removal efficiencies were >90% for PCDDs and PCDFs, but below 30% for cPCBs. A combination of both of these methods is more effective, and almost 100% of the total toxicity equivalence quantity value could be reduced.

Microwave-assisted extraction through an aqueous medium and simultaneous cleanup by partition on hexane for determining pesticides in agricultural soils by gas chromatography: A critical study

A simple microwave-assisted extraction and partitioning method (MAEP) using water-acetonitrile and n-hexane for desorption and simultaneous partitioning, respectively, together with gas chromatography (GC) was studied to determine representative pesticides (trifluralin, metolachlor, chlorpyriphos and triadimefon) with a broad range of physico-chemical properties in agricultural soils. Three points were considered crucial in this study: instrumental and sample-associated factors affecting extraction of the target compounds were studied through experimental design; the spiking procedure at trace levels was carried out to reproduce the solute-soil sorption taking place in the environment as closely as possible; and results were analyzed taking into account the adsorption behaviour of the compounds on different kinds of soils. The complete analytical procedure proposed consisted of the MAEP of pesticides from 1.0 g of soil with 1 mL of 1:1 water/acetonitrile mixture, and 5 mL of hexane for trapping. The microwave heating program applied was 2 min at 250 W and 10 min at 900 W, and 130 degrees C maximum temperature. After extraction, the hexane layer was evaporated to dryness; the residue was re-dissolved and directly analyzed by gas chromatography electron capture detection (GC-ECD). Clean chromatograms were obtained without any additional cleanup step. Besides the four pesticides used to optimise MAEP, the method was applied to determine an additional group of pesticides (triallate, acetochlor, alachlor, endosulphan I and II, endrin, methoxychlor and tetradifon) in different soils. Most of the compounds studied were recovered in good yields with relative standard deviations (R.S.D.s) below 9% and detection limits ranged from 0.004 to 0.036 microg g(-1). The described method is efficient and fast to determine hydrophobic pesticides at ng g(-1) level in soil with different clay-to-organic matter ratios.

Optimization of supercritical fluid extraction of pesticide residues in soil by means of central composite design and analysis by gas chromatography–tandem mass spectrometry

An environmentally friendly methodology is proposed for the analysis of pesticides in soil samples based on supercritical fluid extraction (SFE) and analysis at high selectivity and sensitivity, by gas chromatography-tandem mass spectrometry (GC-MS-MS). The pesticides investigated are among the most commonly used in intensive horticulture activities comprising organochlorine and organophosphorous insecticides, triazine and acetanilide herbicides, amongst others. An experimental design approach was used for modelling SFE and optimised extraction conditions were derived for the total pesticides extraction or for specific sub-groups of interest. Pesticide residues could be detected in soils in the sub-ppb range (0.1-3.7microgkg(-1)), with quite good precision (4.2-15.7%) and extraction efficiency (80.4-106.5%). The analysis of soil samples from an intensive horticulture area in Póvoa de Varzim, north of Portugal, revealed the presence of persistent pesticides, parent compounds and degradation products among the following: endosulfan, endosulfan sulfate, dieldrin, 4,4'-DDE, 4,4'-DDD, atrazine, alachlor, metolachlor, chlorpyrifos, pendimethalin and lindane. The important features to point out are the easy interpretation of chromatograms and straightforward confirmation of analytes that greatly facilitates the analyst judgement on the contamination of the sample.

Multiresidue analysis of pesticides in soil by gas chromatography with nitrogen-phosphorus detection and gas chromatography mass spectrometry

A rapid multiresidue method for the simultaneous determination of 25 fungicides and insecticides in soil was developed. Soil samples are extracted by sonication with a water-acetonitrile mixture, and the pesticides are partitioned into dichloromethane. Final determination was made by gas chromatography (GC) with nitrogen-phosphorus detection (NPD). Confirmation analysis of pesticides was carried out by GC-MS in the selected ion monitoring (SIM) mode. The identification of compounds was based on retention time and on comparison of the primary and secondary ions. The average recovery by the GC-NPD method obtained for these compounds varied from 68.5% to 112.1% with a relative standard deviation between 1.8% and 6.2%. The GC-NPD method presents good linearity over the range assayed 50-2000 microg/L, and the detection limit for the pesticides studied varied from 0.1 to 10.4 microg/kg. The proposed method was used to determine pesticide levels in soil samples from experimental greenhouse pepper cultivation.

Injectors for capillary gas chromatography and their application to environmental analysis

The application of different injectors in capillary gas chromatography (GC) analysis of semi-volatile organic contaminants in environmental samples prepared in organic solvents is reviewed. The injectors examined include a split/splitless injector in splitless mode (SS), cold on-column (COC), and programmable temperature vaporizer (PTV) and adaptations of these injector designs. Key issues when selecting an injector include properties of the analyte, such as potential for thermal degradation or discrimination of high boiling point compounds within the injector, and the ability of the GC systems to handle large volume injections (LVI) primarily to lower detection limits and allow direct coupling with sample preparation techniques such as at-line or on-line solid phase extraction (SPE). LVI also require consideration of matrix interference issues. This review examines only injector chamber modifications that are feasible with a standard GC configuration, however some modifications to the chromatographic system to extend the range of applicability of gas chromatography analysis for environmental samples are also noted.