Liquid chromatographic determination of rotenone in fish, crayfish, mussels, and sediments

An analytical procedure is described for determining residues of rotenone in fish muscle, fish offal, crayfish, freshwater mussels, and bottom sediments. Tissue samples were extracted with ethyl ether and extracts were cleaned up by gel permeation chromatography and silica gel chromatography. Sediment samples were extracted with methanol, acidified, partitioned into hexane, and cleaned up on a silica gel column. Rotenone residues were quantitated by liquid chromatography, using ultraviolet (295 nm) detection. Recoveries from sediment samples fortified with rotenone at 0.3 microgram/g were 80.8%, whereas recoveries from tissue samples fortified with 0.1 microgram/g ranged from 87.7 to 96.8%. Samples fortified with 0.3 microgram/g and stored at -10 degrees C for 6 months before analysis had recoveries ranging from 83.2 to 90.5%. Limits of detection were 0.025 microgram/g for sediments and 0.005 microgram/g for tissue samples.     

Assessment of polycyclic aromatic hydrocarbon content of smoked fish by means of a fast HPLC/HPLC method

Polycyclic aromatic hydrocarbon (PAH) concentrations in smoked food can reach levels hazardous for the human health, especially when the smoking procedure is carried out under uncontrolled conditions. In this work a simple and rapid method for the determination of PAHs in smoked fish samples is described. PAHs were extracted from the insoluble samples (together with fat substances) by homogenization with acidified chloroform. The fat extract was then submitted to a first LC sample preparation step (performed on a large silica column) to isolate PAHs from triglycerides. After reconcentration, the PAH fraction was finally injected into the reverse-phase analytical column. The proposed method, which presents good characteristics of recoveries and repeatability, was also used to analyze PAH content of some smoked trout samples packed under vacuum.     

Gas chromatographic-mass spectrometric determination of six sulfonamide residues in egg and animal tissues

A gas chromatographic-mass spectrometric method using selected ion monitoring mode for simultaneous determination of 6 sulfonamides in egg and edible animal tissues has been developed. Sulfonamides are extracted from a sample with acetonitrile. The extract is passed through a silica cartridge column and concentrated. Diazomethane in ether is added to methylate sulfonamides. After evaporation, the residue is dissolved in methylene chloride and cleaned up by silica gel column chromatography. The methylene chloride eluate containing sulfonamide-methyl derivatives is evaporated to dryness, redissolved in ether and partitioned between 6N hydrochloric acid. The acid phase is made alkaline, extracted with ether, and the ether solution, after concentration, is analyzed by gas chromatography-mass spectrometry in selected ion monitoring mode. Average recoveries from egg and silver salmon fortified at 1 and 0.2 ppm levels with 6 sulfonamides are 99.2 and 84.3%, respectively; coefficients of variation are 7.03 and 11.20%, respectively. Detection limits are 0.01-0.05 ppm.     

Capillary column gas chromatographic determination of dicamba in water, including mass spectrometric confirmation

A sensitive method is described for determining dicamba at low micrograms/L levels in ground waters by capillary column gas chromatography with electron-capture detection (GC-EC); compound identity is confirmed by gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring. Dicamba residue is hydrolyzed in KOH to form the potassium salt. The sample is then extracted with ethyl ether which is discarded. The aqueous phase is acidified to pH less than 1 and extracted twice with ethyl ether. The combined ethyl ether extracts are concentrated, and the residue is methylated using diazomethane to form the corresponding dicamba ester. The derivatized sample is cleaned up on a deactivated silica gel column. The methylated dicamba is separated on an SE-30 capillary column and quantitated by electron-capture or mass spectrometric detection. Average recoveries (X +/- SD) for ground water samples fortified with 0.40 microgram/L of dicamba are 86 +/- 5% by GC-EC and 97 +/- 7% by GC-MS detections. The EDL (estimated detection limit) for this method is 0.1 microgram dicamba/L water (ppb).     

Determination of benzo(a)pyrene in foods

An analytical method was developed for determining benzo(a)pyrene in foods, suitable for routine use. The method consists of 4 cleanup steps: (1) alkali cleavage of sample, (2) preliminary silica gel column chromatography, (3) selective extraction with concentrated sulfuric acid, and (4) further silica gel column chromatography. Recoveries of benzo(a)pyrene added to 50 g (or 10 g) food at levels of 0.4 ppb (or 2 ppb) ranged from 70% for short-necked clam and mackeral to 85% for chicken meat. The sulfuric acid extraction step affords a simple method for isolating benzo(a)pyrene from various kinds of interfering substances which could not be separated by existing methods.     

Liquid chromatographic method for determining the macrolide antibiotic sedecamycin and its major metabolites in swine plasma and tissues

A liquid chromatographic (LC) method was developed to determine sedecamycin, a 17-membered macrolide antibiotic used for treating swine dysentery, and its major metabolites (lankacidin C, lankacidinol A, and lankacidinol) in swine plasma and tissues. Plasma is directly extracted with ethyl acetate and analyzed by liquid chromatography without purification. Tissues are homogenized in a phosphate buffer containing sodium chloride, and then extracted with ethyl acetate. The extracts are subjected to silica gel-Florisil, double-layered column chromatography to remove endogenous interfering substances. The LC determination uses silica gel and ODS-silica as a stationary phase. The detection limits for sedecamycin and its metabolites were less than or equal to 0.05 ppm, and average recoveries and coefficients of variation (0.2-1 ppm range) were greater than 75% and less than 10%, respectively.     

Rapid, semimicro method for determination of polycyclic aromatic hydrocarbons in shellfish by automated gel permeation/liquid chromatography

A simple, rapid, easily automated method is described for the determination of polycyclic aromatic hydrocarbons (PAHs) in shellfish such as American lobster (Homarus americanus) and blue mussel (Mytilus edulis). PAHs are extracted from small amounts (1-8 g) of tissue by saponification in 1N ethanolic potassium hydroxide followed by partitioning into 2,2,4-trimethylpentane. This solution is evaporated just to dryness by rotary evaporation and the residue is dissolved in cyclohexane-dichloromethane (1 + 1) for gel permeation chromatography (GPC) on Bio-Beads SX-3. The GPC procedure is ideal as a screening method in the range 25-18 000 ng PAHs/g tissue. If individual PAH measurements are required, the appropriate GPC fraction is collected and PAHs are separated by reverse phase liquid chromatography (LC) with fluorometric detection. Individual PAHs at concentrations as low as 0.25-10 ng/g can be determined. Recoveries of added fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene were quantitative, with relative standard deviations ranging from 0.0 to 16.9%.     

High-pressure liquid chromatography of benzo(a) pyrene and benzo (ghi) perylene in oil-contaminated shellfish.

A high-pressure liquid chromatographic procedure is described for the determination of benzo(a) pyrene and benzo(ghi) perylene. These polynuclear aromatics are extracted with acetonitrile and partitioned into petroleum ether, the petroleum ether is removed, and the residue is saponified. The compounds are purified and isolated by passing the residue through a silica gel column and a high-pressure liquid chromatographic column, and detected by their ultraviolet absorption. Recoveries of standards through the procedure averaged 104%.     

Investigation of sample treatment steps for the analysis of polycyclic aromatic hydrocarbons in ground coffee

Sample treatment procedures were tested for the determination of polycyclic aromatic hydrocarbons (PAHs) in ground coffee. Pressurized liquid extraction (PLE), under different conditions, was combined with several cleanup methods, namely in situ purification, C18-silica solid-phase extraction (SPE), silica SPE, acid digestion, and alkaline saponification. Soxhlet extraction and direct alkaline saponification were also tested. Best results were obtained using PLE with hexane/acetone 50:50 (v/v) under 150 degrees C. Alkaline saponification followed by cyclohexane extraction and silica SPE was required to eliminate interferent compounds. Finally, 11 PAHs could be quantified in ground coffee with limits of detection in the range of 0.11-0.18 microg kg(-1). Application to ground Arabica coffee lots from Colombia revealed the presence of several PAHs, giving an overall toxicity equivalence in the range of 0.16-0.87 microg kg(-1). PAH identification was performed using both high-performance liquid chromatography-diode array detection and gas chromatography coupled to mass spectrometry.     

High pressure liquid chromatographic determination of polynuclear aromatic hydrocarbons in oysters.

A high pressure liquid chromatographic (HPLC) procedure is described for determining 13 polynuclear aromatic hydrocarbon (PNA) compounds in oysters at the 2 ppb level. These compounds are extracted from shellfish with acetonitrile and partitioned into petroleum ether; the petroleum ether is removed and the residue is saponified. The aromatic compounds are isolated by passing the saponifeid residue through silica gel and further purified and fractionated by muStyragel gel permeation chromatography. The in-ividual PNAs are then quantitatively determined by using a reverse phase HPLC column coupled to fluorescence, spectrophotometric, and 254 nm absorbance detectors in series. Recoveries from spiked samples generally were greater than 80%.     

Polycyclic aromatic hydrocarbon profile analysis of high-protein foods, oils, and fats by gas chromatography.

A method is described for the determination of polycyclic aromatic hydrocarbons (PAHs) with 3-7 rings in (I) meat, poultry, fish, and yeast; and (II) oils and fats. The extraction of PAHs from group I is incomplete, and, therefore, group I samples must be dissolved homogeneously by saponification in 2N methanolic potassium hydroxide. The PAHs are concentrated by liquid-liquid extraction (methanol-water-cyclohexane, N,N - dimethylformamide - water-cyclohexane) and by column chromatography on Sephadex LH 20. The PAHs are separated by high-performance gas-liquid chromatography (GLC) with columns containing 5% OV-101 on Gas-Chrom Q and estimated by integration of the flame ionization detector signals in relation to an internal standard (3,6-dimethylphenanthrene and/or benzo(b)chrysene). The sensitivity is significantly higher than that obtained with ultraviolet spectroscopic methods. The reproducibility and margin of error were tested with meat samples fortified with 11 PAHs and with samples of sunflower oil. The method was further applied to meat, smoked fish, yeast, and unrefined sunflower oil. All samples investigated contained more than 100 PAHs (characterized by mass spectrometry) of which only the main components were determined: phenanthrene, anthracene, fluorene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene + benzo (j)fluoranthene + benzo(k) fluoranthene, benzo(e)pyrene, benzo(a)pyrene, perylene, dibenz(a,j)anthracene, dibenz(a,h)anthracene + indeno(1,2,3,-cd)pyrene, benzo(ghi)perylene, anthanthrene, and coronene. In contrast to other methods, the GLC profile analysis allows the recording of known and unknown PAH peaks simultaneously and also allows a compilation of all PAHs.     

Determination of fluorene in fish, sediment, and plants

Methods and their applications are described for the determination of fluorene in fish, sediment, and plants. Sample extracts are enriched by using 2 or more of the following: gel permeation, silica gel, potassium silicate, sulfuric acid-impregnated silica gel, and activated carbon. Efficiency was improved by applying the adsorbents in combination or as tandem enrichment modules. Analyses by liquid chromatography (LC) with ultraviolet or fluorescence detection (LC/UV or LC/F) yielded limits of detection of 30, 3, and 30 ng/g and average recoveries of 80, 81, and 74% for fish, sediment, and plants, respectively.     

Determination of monocyclic and polycyclic aromatic hydrocarbons in fish tissue

An analytical method is presented in which fish tissue is analyzed for neutral monocyclic and polycyclic aromatic hydrocarbons (AHs) and aromatic sulfur heterocycles (ASHs) by capillary column gas chromatography (CGC) with photoionization detection. The sample enrichment procedure includes saponification with aqueous KOH, acidification of the digestates, and extraction of the aromatic compounds into cyclopentane-dichloromethane. Adsorption chromatography on tandem segments of potassium silicate and silica gel removes 99% of the coextracted lipid. Final enrichment by gel permeation chromatography eliminates residual biogenic material and potentially interfering alkanes. Relatively volatile monoaromatics are included among the analytes by virtue of the efficiency of the complementary enrichment steps, the use of small quantities of only low-boiling solvents, and the selectivity of the detector. Most targeted compounds (AHs ranging in size from C3-alkylbenzenes through benzo[g,h,l]perylene and ASHs within the same size range) can be determined in 5 g (wet weight) samples of fish tissue at concentrations as low as 20 ng/g. Comparisons are made of recoveries of selected AHs under ordinary and gold fluorescent lighting conditions.     

Rapid gas chromatographic method using nitrogen-phosphorus detection for N-nitrosodimethylamine in 2,4-D and MCPA herbicide formulations

A simple and rapid analytical method has been developed for the determination of N-nitrosodimethylamine (NDMA) in amine salts of phenoxy herbicide formulations of 2,4-D and MCPA, plus mixtures of these with mecoprop and dicamba amine salts. Sample preparation consists of direct extraction using pre-packed disposable extraction tubes eluted with dichloromethane followed by cleanup on a disposable silica gel mini-column using ethyl acetate as eluting solvent. Samples are injected on-column for gas chromatography with a Megabore fused silica column; the NDMA is measured by a thermionic specific detector (TSD) that is selective for nitrogen-phosphorus (NP). A detection limit of 0.1 microgram/mL was easily attainable without any concentration step because the solvent volume is minimal. TSD and thermal energy analyzer (TEA) results have been compared and confirmed by gas chromatography/mass spectrometry. Recovery studies were performed as well as a reproducibility study on one of the 2,4-D formulations.     

Effect of a pilot washing system on dicofol levels in orange matrix

An efficient analytical method is described for the analysis of dicofol residues in pulp and orange peel. Samples are mixed with Celite and transferred to chromatographic columns prepacked with silica gel. Dicofol is eluted with ethyl acetate, and the extracts are analyzed by gas chromatography with electron capture detection. Mean recoveries for dicofol at levels of 0.5, 2.0, 5.0, and 10 mg/kg ranged from 87 to 95% with relative standard deviation values between 2.6 and 9.0%. To investigate the effect of a pilot washing system on dicofol residues in oranges, the analytical procedure was applied to samples submitted to different treatments with commercial formulations under field and laboratory conditions. The orange samples with and without washing were analyzed in duplicate, and the results indicated that washing under the described conditions did not allow a complete removal of dicofol residues from orange peel.     

Gas-liquid chromatographic determination of captan and two metabolites in milk and meat

A gas-liquid chromatographic (GLC) method has been developed for the determination of captan (N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide) and 2 metabolites, tetra-hydrophthalimide (THPI) and tetrahydrophthalamic acid (THPMA), in milk and meat. The sample is extracted with ethyl acetate and is cleaned up by acetonitrile partition and silica gel chromatography where captan, THPI, and THPMA are separated. Captan is directly determined by GLC. THPI and THPMA are separately derivatized in an acetone solution of pentafluorobenzyl bromide. The resultant derivatives are purified separately on an Al2O3 column and quantitated by GLC, using an electron capture detector. Recoveries from milk samples fortified at 0.02-10 ppm ranged from 71 to 102%; recoveries from meat samples fortified at 0.04-10 ppm ranged from 75 to 99%.     

Extraction, gas-liquid chromatographic detection, and quantitation of hexachlorophene residues from plant tissues high in lipid content

A method has been developed for the extraction, cleanup, derivatization, detection, and quantitation of hexachlorophene (HCP) residues from 2 types of plant storage tissue high in lipid content. Wet soybean or peanut tissue was homogenized and extracted with ethyl ether and chromatographed on silica gel to remove the neutral lipids. The cleaned up sample was methylated with diazomethane and the dimethoxyhexachlorophene was eluted from a second silical gel column and chromatographed on a 6' glass column packed with 3% OV-1 or 3% SE-30 on Gas-Chrom Q. The instrument detection limit for the 63Ni electron capture detector was less than 0.1 ng for dimethoxyhexachlorophene and about 1 ppb HCP residue in plant issue. Recovery of 10-420 ppb HCP added to tissue averaged 90.9 +/- 5.7%. Interfering substances were removed, column life was increased, peak sharpness was increased, and tailing of the parent compound was decreased by using appropriate column chromatography.     

Rapid quantitation and confirmation of aflatoxins in corn and peanut butter, using a disposable silica gel column, thin layer chromatography, and gas chromatography/mass spectrometry

A simple, rapid, and solvent-efficient method for determining aflatoxins in corn and peanut butter is described. Aflatoxins B1, B2, G1, and G2 were extracted from 50 g sample with 200 mL methanol-water (85 + 15). A portion of the extract was diluted with 10% NaCl solution to a final concentration of 50% methanol, and then defatted with hexane. The aflatoxins were partitioned into chloroform. The chloroform solution was evaporated, and the residue was placed on a 0.5 g disposable silica gel column. The column was washed with 3 mL each of hexane, ethyl ether, and methylene chloride. Aflatoxins were eluted with 6 mL chloroform-acetone (9 + 1). The solvent was removed by evaporation on a steam bath, and the aflatoxins were determined using thin layer chromatography (TLC) with silica gel plates and a chloroform-acetone (9 + 1) developing solvent. Overall average recovery of aflatoxin B1 from corn was 82%, and the limit of determination was 2 ng/g. For mass spectrometric (MS) confirmation, aflatoxin B1 in the extract from 3 g sample (20 ng/g) was purified by TLC and applied by direct on-column injection at 40 degrees C into a 6 m fused silica capillary gas chromatographic column. The column was connected directly to the ion source. After injection, the temperature was rapidly raised to 250 degrees C, and the purified extract was analyzed by negative ion chemical ionization MS.     

Flameless atomic absorption spectrophotometric determination of Vendex, an organic tin miticide, in apples, oranges, and tea leaves.

A method is described for the determination of an organic tin insecticide, Vendex or hexakis(2-methyl-2-phenylpropyl)distannoxane (HMPD). Tin compounds are extracted from the sample homogenate with ethyl ether containing 1% acetic acid. HMPD and its degradation products are separated through a silica gel column, and analyzed by an atomic absorption spectrophotometer coupled with a heated graphite atomizer. By this technique, as little as 5 ng HMPD and its degradation products can be determined with an average recovery of 67-96%.     

Simultaneous determination of neonicotinoid insecticides in agricultural samples by solid-phase extraction cleanup and liquid chromatography equipped with diode-array detection

Effective sample pretreatment procedures based on solid-phase extraction (SPE) for multiresidue determination of seven neonicotinoid insecticides in agricultural products were investigated. After extraction with acetone and concentration, the insecticides in aqueous sample extracts were transferred into organic solvent phases with a Chem Elut SPE cartridge. Finally, the eluate from the cartridge was cleaned up with a SPE cartridge packed with graphitized carbon black and aminopropyl silica gel, which showed a higher cleanup efficiency than the classical silica gel SPE cartridge. Seven insecticides were separated on a reversed-phase C18 column and a gradient system of methanol and phosphate solution based on high-performance liquid chromatography. The established multiresidue determination has been applied to several artificially spiked agricultural samples, with the result that the average recoveries were excellent, with the exception of nitenpyram. The limit of detection of the method ranged from 0.01 to 0.03 mg/kg for the insecticides.