Multiresidue analysis of fungicides in soil by sonication-assisted extraction in small columns and gas chromatography

A rapid multiresidue method for the simultaneous determination of 14 fungicides in soil was developed. Fungicides were exacted from soil, placed in small columns, by sonication-assisted extraction with ethyl acetate. The effect of residue residence time and soil moisture content on the fungicide recovery was studied. Residue levels in soil were determined by gas chromatography with electron-capture and nitrogen-phosphorus detection. Residue identities were confirmed by gas chromatography coupled with mass spectrometry, in the selected ion monitoring mode. Recovery studies were carried out at 0.5, 0.1 and 0.05 microg/g fortification levels for each fungicide, and average recoveries obtained for these compounds ranged from 80 to 104% with relative standard deviations between 1 and 8%. The method is linear over the range assayed, 0.5-0.05 microg/g, and the detection limit for the fungicides studied varied from 2 to 10 microg/kg.     

Analysis of salicylate and benzophenone-type UV filters in soils and sediments by simultaneous extraction cleanup and gas chromatography-mass spectrometry

An analytical method for the determination of UV filters in soil and sediment has been developed and validated considering benzophenones (BP) and salicylates as target analytes. Soil and sediment samples were extracted with ethyl acetate-methanol (90:10, v/v) assisted with sonication, performing a simultaneous clean-up step. Quantification of these compounds was carried out by gas chromatography-mass spectrometry (GC-MS) after derivatization of the extracts with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Recoveries from spiked soil samples ranged from 89.8% to 104.4% and they were between 88.4% and 105.3% for spiked sediment samples. The effect of the residence time and soil moisture content on the recovery of these compounds was also studied. The precision, expressed as relative standard deviation, was in all cases below 6.1% and the limits of detection (S/N=3) varied from 0.07 to 0.10 ng g(-1) and from 0.11 to 0.28 ng g(-1) for soils and sediments, respectively. The validated method was applied to the analysis of five benzophenone and two salicylate UV filters in soil and sediment samples collected in different areas of Spain.     

High resolution chemically bonded fused-silica capillary gas chromatography of organochlorine insecticides and related compounds in arable soil samples

Electron capture gas chromatography with three chemically bonded fused-silica capillary columns (CB-FSCs), OV-17, OV-1701, and SE-52, was performed to evaluate peak separability of 28 organochlorine insecticides and related compounds. Relative retention times and relative peak heights to aldrin were measured and calculated. OV-17 CB-FSC showed the best separability among the three CB-FSCs employed and was applied to analysis of extracts from several soil samples with minimum clean-up procedure. The chromatograms obtained demonstrated steady baseline tracings free of interference. Residue data from soil samples were also tabulated.     

Determination of pesticides in soil samples by solid phase extraction disks

Summary A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C₈ disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detection limits are between 5 and 30 ng g^–1 based on 5 g moist soil sample. The method was validated by comparing it with conventional liquid-liquid extraction.     

Analysis of endosulfan isomers and endosulfan sulfate in air and tomato leaves by gas chromatography with electron-capture detection and confirmation by gas chromatography-mass spectrometry

Rapid analytical methods for the determination of endosulfan isomers and endosulfan-sulfate in air and plant samples were developed. The insecticides were trapped from air using a column containing Florisil and extracted with a low volume of ethyl acetate, assisted by sonication. Pesticide residues were determined by gas chromatography with electron-capture detection using a nonpolar capillary column. Residue identities were confirmed by gas chromatography coupled with mass spectrometry. Recoveries of these compounds from air samples were always higher than 78% with an RSD lower than 11% and the detection limits obtained were at least 0.3 ng/l air. Leaf samples were homogenised with ethyl acetate and extracts cleaned-up on an aluminium oxide column. Pesticides were eluted with a hexane-ethyl acetate (80:20, v/v) mixture. Recoveries obtained from plant samples were higher than 78% with an RSD lower than 14% and detection limits in leaves were 0.02 microg/g for each pesticide. These methods were applied to study the volatilisation of endosulfan from tomato leaves under laboratory conditions. A volatilisation rate near 1% of the initial amount of endosulfan per hour was obtained during the first 24 h at room temperature.     

Determination of insecticides in honey by matrix solid-phase dispersion and gas chromatography with nitrogen-phosphorus detection and mass spectrometric confirmation

A multiresidue method was developed for the determination of 12 organophosphorus insecticides (diazinon, parathion methyl, fenitrothion, pirimiphosmethyl, malathion, fenthion, chlorpyrifos, quinalphos, methidathion, ethion, azinphosmethyl, coumaphos), one carbamate (pirimicarb), and one amidine (amitraz) in unifloral and multifloral honeys. The analytical procedure was based on the matrix solid-phase dispersion of honey on a mixture of Florisil and anhydrous sodium sulfate in small glass columns and subsequent extraction with a low volume of hexane-ethyl acetate (90 + 10, v/v), assisted by sonication. The insecticide residues were determined by capillary chromatography with nitrogen-phosphorus detection and confirmed by mass spectrometry. Average recoveries at the 0.05-0.5 microg/g levels were >80% for organophosphorus insecticides and about 60% for the other insecticides, pirimicarb and amitraz, with relative standard deviations <10%. The detection limit for the different insecticides ranged between 6 and 15 microg/kg. The main advantages of the proposed method are that extraction and cleanup are performed in a single step with a low volume of organic solvent. The method is simple, rapid, and less laborious than conventional methods. Several Spanish honeys were analyzed with the proposed method and no residues of the studied insecticides were found.     

Analysis of organophosphorus insecticides in biological samples by selective ion monitoring gas chromatography-mass spectrometry

Gas chromatography with chemical ionization or electron impact mass spectrometry and selected ion monitoring provided a simple and sensitive method for measuring organophosphorus insecticides. Chemical ionization produced higher-mass ions which might increase the selectivity and sensitivity of the assay. The recovery of organophosphates from saline and urine was greater than 75%. The recovery of these compounds from plasma was less than the saline because of the binding of insecticides to plasma protein. Insecticides with lower LD50 values showed lower recovery from plasma than organophosphates with higher LD50 values.     

Analysis of triallate residues in cereals and soil by gas chromatography with ion-trap detection.

Triallate residues in barley seedlings and soil samples were determined by gas chromatography with ion-trap detection. Soil was extracted with methanol on a mechanical shaker, and plants were extracted with acetonitrile in a Sorvall homogenizer. After evaporation of the organic solvents, the residue was dissolved in hexane, and plants extracts were cleaned-up on an alumina column. Gas chromatographic analysis was carried out using a BP-1 fused-silica capillary column with helium as carrier gas. To quantitate residues the total-ion chromatogram was obtained and then the selected-ion monitoring chromatograms were displayed at m/z 86 for triallate and at m/z 154 for the internal standard, methyl-(4-amino-2-chloro)-benzoate. The average recovery through the method from barley and soil samples was always higher than 80%. The limit of detection in the selected-ion mode was 0.01 mg/kg. Barley and soil samples treated with triallate were also analysed. A good agreement was observed between results obtained by this method and by gas chromatography with nitrogen-phosphorus detection.     

Determination of polybrominated diphenyl ethers in soil by ultrasonic assisted extraction and gas chromatography mass spectrometry

An analytical method for the determination of polybrominated diphenyl ethers (PBDEs) in soil was developed. Soil samples were placed in small glass columns and PBDEs extracted from soil, with a low volume of ethyl acetate (5 mL, 2× 15 min), assisted by sonication. PBDEs were determined by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS–SIM) and residues were confirmed by their retention times, selected ions and qualifier–target abundance ratios. Recovery studies were performed at 10, 1, 0.1 and 0.05 μg/kg fortification levels, and the recoveries obtained ranged from 81 to 104% with a relative standard deviation between 1 and 9%. The detection limit of the method varied from 2 to 30 pg/g and the quantification limit ranged from 7 to 100 pg/g for the different PBDEs studied. The developed method was linear over the range assayed, 0.01–10 μg/kg with determination coefficients equal or higher than 0.997. The proposed method was used to determine PBDEs levels in soil samples from different areas of Spain and PBDEs were detected in some samples with values ranging from 1.3 to 5.6 μg/kg.     

Wide-bore glass capillary columns for gas chromatography. Their preparation and application

Summary Methods for the preparation of wide-bore glass capillary columns for gas chromatography are presented. The pretreatment of the columns (etching, carbonization, deactivation and/or surface-coating with porous materials), and the coating of them with polar or apolar phases (preferably by the static method) is described. The performance of the columns prepared is evaluated and a number of applications are given, such as analysis of volatile compounds, pesticides, lipids and GC/MS analysis. In some respects, the wide-bore glass capillaries have advantages over the narrow-bore types. They can be installed very easily in GC-instruments, and permit the analysis of larger samples. A system of collecting separated sub-g fractions in glass capillary traps, which makes direc re-injection from these traps possible, completes the methods presented.     

Determination of aromatic hydrocarbons in petroleum jet fuels by capillary gas chromatography and high-performance liquid chromatography

About a hundred hydrocarbon compounds have been identified as components of petroleum jet fuel by capillary gas chromatography and high-performance liquid chromatography. In gas chromatography stuides, glass capillary columns over 100 m long with polysiloxane OV-101 have been used as the stationary phase. In liquid chromatography, 150-mm-long columns with a separation ability of about 60 000 theoretical plates meter of length have been used to separate partitioned fractions of aromatic hydrocarbons from petroleum jet fuels of various origins.     

Multiresidue determination of pesticides in honey by matrix solid-phase dispersion and gas chromatography with electron-capture detection

A multiresidue method was developed for the determination of 15 pesticides (organochlorines, organophosphorus compounds, pyrethroids, and other acaricides) in various commercial honeys (eucalyptus, lavender, orange, rosemary, and multifloral). The analytical procedure is based on the matrix solid-phase dispersion of honey in a mixture of Florisil and anhydrous sodium sulfate; the mixture is placed in small plastic columns and extracted with hexane-ethyl acetate (90 + 10, v/v). The pesticide residues are determined by capillary gas chromatography with electron-capture detection. Recoveries with the method at concentrations between 0.15 and 1.5 microg/g ranged from 80 to 113%, and relative standard deviations were <10% for all the pesticides studied. The pesticide detection limits were within the range 0.5-5 microg/kg for organochlorines, around 3 microg/kg for the chlorinated organophosphorus pesticides studied, near 15 microg/kg for fluvalinate, and about 3 microg/kg for the other pyrethroids.     

Residue analysis of organophosphorus pesticides in animal matrices by dual column capillary gas chromatography with nitrogen-phosphorus detection

Organophosphorus pesticides (OPPs) were determined in matrices of animal origin by dual column capillary gas chromatography using nitrogen-phosphorus detection (NPD). This method was tested on cow milk and on liver and muscle of wild boar. The isolation of these pesticides was performed by liquid partition followed by cleanup with solid phase cartridge (SPE C18), after extraction from the matrix. The analytes identification was obtained by comparing the retention times in two columns with different polarity. The quantification of each OPP was obtained using parathion-ethyl as internal standard. The method was developed in a UNI EN ISO 9001:2000 certified laboratory. The recovery, investigated by analyzing samples spiked at 5, 10 and 50 ppb, ranged from 59 to 117% in milk, from 60 to 81% in liver and from 68 to 76% in muscle. The limit of quantification (LOQ) and limit of detection (LOD) were, respectively, 5 and 1 ppb for each compound and allowed quantifying the residues below the legal limits.     

Determination of 24 pesticides residues in mineral and peat soils by modified QuEChERS method and gas chromatography

A simple extraction and cleanup procedure has been developed for the analysis of 24 organophosphorus (OP), organochlorine (OC) and pyrethroid (PY) pesticides in mineral and peat soils using modified QuEChERS method. The pesticides were extracted from the soil with acidified acetonitrile. The water was removed from the extract by salting out with sodium chloride and addition of magnesium sulfate. For OP pesticides, the extracts were cleaned up with 0.2 g of primary secondary amine packed in glass Pasteur pipette and determined by gas chromatography with flame photometric detector. For OC and PY pesticides, the extracts were cleaned up with 0.2 g of silica gel packed in a glass Pasteur pipette and determined by gas chromatography with electron capture detector. After the cleanup, the extracts had lower colour intensity and reduced matrix interferences. The recovery of the OP and OC pesticides for mineral and peat soils determined at 0.01–1.0 mg kg^?1 fortification levels ranged from 79.0–120.0% and 82.2–117.6%, respectively. The detection limits for OP and OC pesticides were 0.001–0.01 and 0.002–0.005 mg kg^?1, respectively. The recovery of the PY pesticides ranged from 87.5–111.7% at the detection limits of 0.002–0.010 mg kg^?1. The relative standard deviations for all pesticides studied were below 10.8%. The modified method was simple, fast, and had utilized less reagents than the conventional methods. The method was applied to the determination of the pesticide residues in mineral and peat soil samples collected from the vegetable farms.     

Effect of column material on sorption isotherms obtained by inverse gas chromatography

The dependence of sucrose sorption isotherm data obtained by inverse gas chromatography on column material was studied. Columns made of polyamide glass, copper and stainless steel were used. The results obtained indicate that the interaction between water vapour and the column wall cannot be ignored when products with very low equilibrium moisture content are considered.     

Preparative gas chromatography with glass capillary columns

The present paper describes an automated system for preparative gas chromatography with glass capillary columns, controlled by a microprocessor. The effluent from the capillary column is divided by a pneumatically controlled splitter and any desired split ratio between traps and detector can be obtained. Moreover, a second pneumatic control allows instantaneous change-over to a different split ratio, thus minimizing loss of material during collection. The effluent containing the compounds of interest is passed through a multiple manifold and collected in coiled glass capillary traps. To ensure maximum trapping efficiency even for very small amounts of material, the inner walls of the capillary traps are wetted with a suitable solvent, which gives a quantitative recovery of micro- and nanogram amounts of material. After repetitive sampling, sufficient amounts of material can be obtained for NMR spectroscopy and possibilities exist to enrich trace components with the aid of a double column system. Two examples of such applications are given, employing mixtures of both synthetic and natural origin.     

Determination of pesticide residues in soil by modified matrix solid-phase dispersion and gas chromatography

Modified matrix solid-phase dispersion (MMSPD) and gas chromatography have been developed for quantitative analysis of various classes of pesticides (pirimicarb, metalaxyl, metolachlor, isopropalin and pendimethalin) in soil. MMSPD used Florisil as dispersant and acetone as solvent. Determination was carried out by gas chromatography with nitrogen-phosphorus detection (GC-NPD). The effect of the residence time of pesticides in soil on the recoveries was studied. MMSPD was compared with continuous liquid-solid extraction (LSE). MMSPD had good extraction efficiency and cleanup efficiency and the extract obtained could be directly subjected to GC analysis without further purification. The method gave recoveries ranging from 93% to 100% with relative standard deviations (RSDs) lower than 10%. The limits of detection (LODs) ranged from 0.2 to 2.0 ng g(-1).     

Simple method for the determination of trace levels of pesticides in honeybees using matrix solid-phase dispersion and gas chromatography

A simple multiresidue method for the determination of insecticides in honeybees is described. The developed method is based on the matrix solid-phase dispersion technique. A total number of 12 insecticides (azinfos-methyl, buprofezin, chlorpyriphos, chlorpyriphos-methyl, diazinon, ethion, fenitrothion, fipronil, methidathion, phosalone, pirimicarb, propoxur) used on flowering fields are determined by this method. The method uses Florisil and silica as dispersing agents, alumina and silica as cleanup adsorbents and a low polarity solvent system to elute pesticide residues from the honeybee samples. The insecticides were quantified using capillary gas chromatography with a nitrogen-phosphorus detector. The method has shown good recovery (70-110%) for various levels of spiked samples (0.01-1.0 mg/kg). The relative standard deviations were in the range of 2-8% for all pesticides studied. The limits of detection were in the range of 0.005-0.05 mg/kg. The procedure can be applied for the determination of residues of low-polarity and medium polarity pesticides in honeybee samples.     

Organochlorine residue analysis of commercial milks by capillary gas chromatography

The determination of organochlorine pesticides and polychlorinated biphenyls in milks requires the use of efficient extraction methods. A rapid procedure has been developed, based on extraction of organochlorine residues from milk on to octadecylsilica solid phase extraction cartridges and elution with hexane. The addition of different organic solvents to the milk before solid phase extraction has been studied. The use of methanol to disrupt the fat globules enables almost complete recovery of the residues with minimum extraction of fatty substances. Recovery experiments were performed for eighteen compounds present at ppb levels in whole, two per cent, and skimmed milks. The average recoveries of the compounds from two per cent and skimmed milks were 73–84%; values for whole milk were lower. The residues were determined by gas chromatography using two kinds of capillary column (non-polar and semi-polar) and electron capture detection. The procedure shows low lipid carry over, and extraneous interferences are minimal. The method has been applied to the detection of organochlorine pesticides and nine individual polychlorinated biphenyls in commercial milks. The results obtained demonstrated the presence of very low levels of organochlorine residues in the commercial milks analyzed.     

Purification and quantitative analysis of urinary prostanoids in human and in rat by packed and capillary gas chromatography-negative-ion chemical-ionization mass spectrometry

We describe a method for the quantitative analysis of prostaglandin (PG) E2 and the major urinary metabolites PGI2 and thromboxane (Tx) A2 in human and in rat by combined gas chromatography and negative-ion chemical-ionization mass spectrometry. The procedure is based on the sequential use of small columns with distinct properties combined with a thin-layer chromatography step, for the extraction and the purification of urinary prostaglandins. The compounds are then analysed as their pentafluorobenzyl ester-O-methyloxime-trimethylsilyl ether derivatives, using either packed or capillary columns. Deuterated analogues are used as internal standards. The method was established by using tritiated prostaglandins covering the extremes of polarity in order to optimize the recovery of prostanoids as well as the quality of the chromatograms and spectra. The overall recovery was 24%. Standard curves were obtained by the same procedure and found to be reproducible, with a maximal day-to-day variation of +/- 5%. The relatively simple approach required for the sequential extraction and purification of prostaglandins on small columns of distinct properties, combined with the highly specific and highly sensitive method of detection, places this procedure among the most reliable method for measuring urinary prostanoids in both humans and animals. In addition, the procedure is faster than classical approaches and necessitates smaller amounts of samples and solvents.