Multiresidue analysis of pesticides in animal feed concentrate.
Explore the source record for details and available documents.
Animal Feed↗
Biomedical subjects
H J Stan
Publications and source records attributed to H J Stan.
Determination of tocopherols, tocopherolquinones and tocopherolhydroquinones by gas chromatography-mass spectrometry and preseparation with lipophilic gel chromatography.
Lipophilic gel chromatography using Sephadex LH-20 helps in separating alpha-, beta- + -gamma, and delta-tocopherol and also in separation of their oxidation products e.g. the tocopherolquinones or other oxidation products. This preseparation can help to overcome analytical problems due to the complexity of synthesis mixtures of tocopherol oxidation procedures as well as in separation of complex physiological matrices. Determination of the preseparated tocopherols, tocopherolquinonesand tocopherolhydroquinones can then be achieved by means of GC-MS measurement of the free substances or their trimethylsilyl derivatives.
Chromatography, Gel↗
Comparative analysis of the biosorption of cadmium, lead, nickel, and zinc by algae.
Thirty strains of algae were examined for their biosorption abilities in the uptake of cadmium, lead, nickel, and zinc from aqueous solution. A wide range of adsorption capacities between the different strains of algae and between the four metals can be observed. The cyanophyceae Lyngbya taylorii exhibited high uptake capacities for the four metals. The algae showed maximum capacities according to the Langmuir Adsorption Model of 1.47 mmol lead, 0.37 mmol cadmium, 0.65 mmol nickel, and 0.49 mmol zinc per gram of dry biomass. The optimum pH for L. taylorii was between pH 3 and 7 for lead, cadmium, and zinc and between pH 4 and 7 for nickel. Studies with the algae indicated a preference for the uptake of lead over cadmium, nickel, and zinc in a four metal solution. The metal binding abilities of L. taylorii could be improved by phosphorylation of the biomass. The modified biosorbent demonstrated maximum capacities of 2.52 mmol cadmium, 3.08 mmol lead, 2.79 mmol nickel, and 2.60 mmol zinc per gram of dry biomass. Investigations with phosphated L. taylorii indicated high capacities for the four metals also at low pH. The selectivity remained quite similar to the unmodified algae.
Absorption↗
Pesticide residue analysis in foodstuffs applying capillary gas chromatography with mass spectrometric detection. State-of-the-art use of modified DFG-multimethod S19 and automated data evaluation.
This paper focuses on recent developments in the author's laboratory and reports on the "ultimate" analysis scheme which has evolved over the last 20 years in our laboratory. This demonstrates the feasibility of screening analyses for pesticide residue identification, mainly by full scan GC-MS, down to the 0.01 ppm concentration level in plant foodstuffs. It is based on a miniaturized DFG S19 extraction applying acetone for extraction followed by liquid-liquid extraction with ethyl acetate-cyclohexane followed by gel permeation chromatography. The final chromatographic determination is carried out with a battery of three parallel operating gas chromatographic systems using effluent splitting to electron-capture and nitrogen-phosphorus detection, one with a SE-54 the other with a OV-17 capillary column and the third one with a SE-54 capillary column and mass selective detection for identification and quantitation. The method is established for monitoring more than 400 pesticides amenable to gas chromatography. These pesticide residues are identified in screening analyses by means of the dedicated mass spectral library PEST.L containing reference mass spectra and retention times of more than 400 active ingredients and also metabolites applying the macro program AuPest (Automated residue analysis on Pesticides) for automated evaluation which runs with Windows based HP ChemStation software. The two gas chromatographic systems with effluent splitting to electron-capture and nitrogen-phosphorus detection are used to check the results obtained with the automated GC-MS screening and also to detect those few pesticides which exhibit better response to electron-capture and nitrogen-phosphorus detection than to mass spectrometry in full scan.
Automation↗
Determination of ethylenethiourea in food commodities by a two-step derivatization method and gas chromatography with electron-capture and nitrogen-phosphorus detection.
Ethylenethiourea (ETU) is a decomposition product from ethylene-bis-dithiocarbamates (EBDCs), the most widely used class of fungicides in the world. ETU has been classified as a possible human carcinogen. The maximum permitted residue level (MRL) in the European Union was set at 0.05 ppm. Gas chromatographic determination of ETU can be achieved only after derivatization. ETU is extracted from food samples and cleaned up by a combination of two-step derivatization and liquid-liquid partitioning. In the first step, ETU is derivatized with benzyl chloride to form S-benzyl ETU, which is then trifluoroacetylated to form the final product, which is amenable to GC. The determination is carried out with capillary gas chromatography using electron-capture (ECD) and nitrogen-phosphorus detection (NPD) as selective detection methods in parallel. The responses of ECD and NPD were found to be of the same order of magnitude. Therefore, the parallel response was found to be a useful criterion for peak identification down to the limit of detection. Reproducibility of the two-step derivatization of ETU to form trifluoroacetylated S-benzyl ETU was found to be satisfactory. The recoveries from apple, pear, tomato and a common baby food, at various concentration levels, were found to be between 82-92%, with a limit of detection of less than 1 ppb. Commercial samples, submitted for routine monitoring of dithiocarbamates (DTC) were also monitored in our laboratory for the presence of ETU. Four of the twenty samples found positive for DTC were also found to be contaminated with ETU in the range of 0.01 to 0.37 ppm. Three of these food samples were found to contain ETU residues above the MRL of 0.05, while those food samples containing DTC residues between 0.2 and 0.8 ppm were all below the MRL of DTC. No relation exists between the DTC residues concentration and the level of ETU. The screening data were further confirmed by electron impact mass spectrometry in selected ion monitoring mode. Chromatograms of ETU residue analyses are presented to demonstrate the extremely sensitive detection method with real food samples.
Benzyl Compounds↗
Pesticide residue analysis in foodstuffs applying capillary gas chromatography with atomic emission detection state-of-the-art use of modified multimethod S19 of the Deutsche forschungsgemeinschaft and automated large-volume injection with programmed-temperature vaporization and solvent venting.
Atomic emission detection (AED) provides high element-specific detection of all compounds amenable to gas chromatography (GC). The heteroatoms nitrogen, chlorine, phosphorus, sulfur, bromine and fluorine, which are important elements in pesticide residue analysis, are of major interest. A main drawback of AED is its lower sensitivity with respect to other selective detection methods used in pesticide residue analysis such as electron-capture and nitrogen-phosphorus detection. This holds true especially for the important nitrogen trace. For this reason, more sensitive detection can be achieved by injection of larger volumes or higher concentrations of sample extracts, because matrix compounds were usually registered only in the carbon, hydrogen and oxygen traces. This paper focuses on recent developments from the authors' laboratory in order to demonstrate the feasibility of screening analyses with the identification of pesticide residues down to the 0.01 ppm concentration level in plant foodstuffs. This has been achieved by means of automated large volume injection with programmed-temperature vaporization and solvent venting as well as careful optimization of make-up and reactant gases with AED. Clean up follows the principle of multimethod S19 of the Deutsche Forschungsgemeinschaft in a reduced procedure. After elimination of lipids and waxes by gel permeation chromatography, extracts from 10 g of the food samples were concentrated to 200 microliters, of which 12.5 microliters were introduced into the GC-AED system. Two analyses were usually performed with the element traces of sulfur, phosphorus, nitrogen and carbon in the first run and chlorine and bromine in the second run. Fluorine and oxygen were not detected in any screening analyses. The method has proved to be of great value especially with "problem foodstuffs". The limits of detection were determined for 385 pesticides and are presented together with their retention data.
Chromatography, Gas↗
Determination of resin acids in pulp mill EOP bleaching process effluent.
Resin acids are tricyclic diterpenoids which are natural constituents of the wood from conifers. They are released from the wood during the manufacture of pulp and paper. These acids are very resistant to chemical degradation and survive the pulping and also the EOP bleaching process (EOP=alkaline extraction, oxygen and peroxide, the chemicals used in the bleaching process). Resin acids were extracted from alkaline medium using liquid-liquid extraction with t-butyl methyl ether and solid phase extraction with RP C18 adsorbent and a highly porous polystyrene-divinylbenzene polymer. After conversion of the acids to their pentafluorobenzyl esters, the extracts were analysed by GC/MS using a 25 m OV17 capillary column. Recovery values for single resin acids were determined by all three extraction methods. The solid phase extraction methods were applied to the analysis of the EOP effluent from a pulp mill bleaching process. 14 different resin acids and one resin acid methyl ester have been identified in the effluent. One of these was an oxo resin acid which might well be a product of the bleaching process.
Journal Article↗
Rapid micro liquid-liquid extraction method for trace analysis of organic contaminants in drinking water.
The applicability and performance of a micro liquid-liquid extraction method for trace analysis of organic compounds in drinking water is reported. Tap water samples of 400 ml are saturated with sodium chloride and extracted once with 500 microliters of toluene. Extracts are analyzed directly without further treatment by gas chromatography using simultaneous electron-capture and nitrogen-phosphorus detection. Recoveries of 82 organic compounds, including organochlorine and organophosphorus insecticides, triazine and acetanilide pesticides, chlorinated anilines and phenols from tap water samples spiked at 50 to 500 ng/l were determined and relative standard deviations were calculated. For 68 compounds the recoveries were higher than 50%. The mean relative standard deviations were calculated. For 68 compounds the recoveries were higher than 50%. The mean relative standard deviations were calculated. For 68 compounds the recoveries were higher than 50%. The mean relative standard deviations at spiking levels of 50, 100 and 500 ng/l were 7.9, 6.6 and 5.2%, respectively. The extraction method proved to be rapid, simple and inexpensive. In most cases compounds were reproducibly detected well below the European Union maximum tolerance level for pesticide residues in drinking water of 100 ng/l.
Chromatography, Gas↗
Screening analysis of pesticide residues in plant foodstuffs by capillary gas chromatography using the DFG multiresidue method S19: a comparison of customary detection by ECD/NPD with the novel atomic emission detector (AED).
Over a period of 7 months nearly 240 plant foodstuffs taken fresh from the market were analysed for pesticide residues using the Deutsche Forschungsgemeinschaft (DFG) multiresidue method (MRM) S19. The analysed foodstuffs were a representative cross-section of different fruits and vegetables offered on sale on the German market. With the slightly modified MRM S19, up to 400 pesticides and metabolites amenable to gas chromatography (GC) can be determined. The screening analysis was performed with the combination GC-electron-capture detector (ECD)/nitrogen-phosphorus detector (NPD) as well as with the combination GC-atomic emission detector (AED) in parallel. Results obtained from both screening systems agree over the whole concentration range observed. With so-called "problem foodstuffs" the combination GC-AED is clearly more suitable. Confirmation of positive results was performed by GC-mass spectrometry (MS) analysis. On account of its higher selectivity and its wide linear dynamic range down to the lowest detectable concentrations, the GC-AED system produces more reliable quantitative results compared to those obtained from the GC-ECD/NPD system.
Chromatography, Gas↗
CAPA--Computer Aided Pesticide Analysis. Computer program for the automated evaluation of chromatographic data for residue analysis of foods.
Pesticide residue analysis in food by means of gas chromatography with columns of different polarity and several selective detectors provides the analyst with a great number of chromatographic data. The introduction of personal computer based chromatographic data systems into research laboratories increased the efficiency of information management and organization; user designed software packages now have direct access to the stored data. The computer program CAPA (Computer Aided Pesticide Analysis) was developed for the interpretation and evaluation of chromatographic results. The program is written in TURBO PASCAL 3.0 and consists of several subprograms. In the main database all pesticides are filed in a multidimensional structure. The various subprograms have access to this catalog of retention and response data. Using the subprogram INTERPRET, which is the core of CAPA, the analyst is provided with all information necessary to interpret a gas chromatogram: identification of calibrated pesticides and estimation of their concentration. Automated screening analyses can be evaluated with the subprogram AUTOINTERPRET, an automated of INTERPRET that uses all relevant information stored in the data base. A report is produced containing the pesticides found in the sample and proposals how to confirm them best with the equipment and methods available. Finally the analyst has to make the decision about the probable presence and quantity of the indicated pesticides and to project the next confirmatory step by using INTERPRET.
Autoanalysis↗
Microcomputer programming in basic for the evaluation of capillary gas chromatography in the analysis of pesticide residues. I. MATRIXCOMP--a program that facilitates the recognition of interfering peaks from the biological matrix.
Chromatograms of pesticide residues in food include peaks produced by pesticides and matrix compounds. Pesticide peaks are recognized by means of relative retention times and response factors; two detectors are used and internal standard methods are applied. Chromatograms of reference samples for all types of food are stored as raw data in a reduced format, together with tables of all chromatographic data for the matrix compounds. MATRIXCOMP provides the analyst with the chromatograms of the actual sample and the reference in parallel on a visual display screen for visual comparison. Simultaneously, the relevant chromatographic data for the sample, the reference and the calibration tables are displayed on a second screen page in a condensed form.
Chromatography, Gas↗
Automated gas chromatographic analysis of pesticide residues in food samples by means of fused-silica capillary columns and data processing.
A conventional gas chromatograph with one system for split and splitless injection and one on-column injection system for fused-silica capillary columns and the two selective nitrogen-phosphorus and electron-capture detectors is applied to pesticide residue analysis in food samples. The gas chromatograph is equipped with a two-channel data processor that can be programmed with BASIC. Additionally an autosampler is used with the splitless injector. This automated injection system is connected to a 25-m methylsilicone fused-silica column which is coupled via an effluent splitter parallel to both detectors and used for screening in routine analysis. Calibration is performed on this column by means of three calibration test mixtures which include three internal standards. All compounds are calibrated on both detectors in parallel and the response calculated as an additional identification parameter. After the analysis of a of food samples together with the calibration mixture a report is plotted, containing all pesticide residues which may be present in the samples and their tentative quantities. The final confirmation is achieved on the second column, coated with methylphenyl-silicone phase, connected to the on-column injector.
Autoanalysis↗
Automated capillary gas chromatographic analysis of pesticide residues in food.
A method for multiresidue pesticide analysis in food is described. After a conventional clean-up, gas chromatographic analysis is performed in a gas chromatograph equipped with two fused-silica capillary columns coated with methylsilicone SP 2100 and methylphenylsilicone OV-17. The effluent from each column is split to electron-capture and nitrogen-phosphorus detectors, which are connected to a dual channel integrator. Therefore, from each gas chromatographic run parallel records of signals from the two detectors are obtained. Calibration of the system is carried out for the SP 2100 column with three test mixtures covering all pesticides. Additionally, four internal standards are included, two responding to the electron-capture detector and the other two to the nitrogen-phosphorus detector. Automated analysis is performed with test mixtures and food samples on the SP 2100 column overnight as a screening procedure. After selection of positive samples a confirmatory test and quantitation are carried out manually applying appropriate test mixtures according to the results of the screening runs.
Chromatography, Gas↗
Investigation, with the Salmonella/microsome test, of psychopharmaceuticals used in meat production.
Azaperone, acepromazine, xylazine and diazepam were tested for mutagenic activity. To screen these veterinary drugs we used the Salmonella/microsome test on 5 histidine-auxotrophic strains, with and without metabolic activation. Azaperone and xylazine were found to be weakly mutagenic.
Acepromazine↗
Investigation of the butyrophenone tranquilizer azaperone and its main metabolites with the Salmonella/microsome test.
In previous experiments, azaperone was found to be weakly mutagenic, after metabolic activation, in the Ames assay. In this study, we subjected metabolites found in rat and swine to the Salmonella/microsome test. 5 histidine-auxotrophic strains were used. The main metabolites could be classified as weakly mutagenic substances.
Animals↗
Mutagenicity studies on veterinary anabolic drugs with the Salmonella/microsome test.
Explore the source record for details and available documents.
Anabolic Agents↗
Determination of residues of anabolic drugs in meat by gas chromatography-mass spectrometry.
The residues in meat of seven estrogenic drugs used in anabolic preparations for animal production were analysed as trimethylsilyl ethers by electron-impact gas chromatography-mass spectrometry following a simple clean-up procedure. The compounds under investigation were: 17 beta-estradiol,l diethylstilbestrol,l hexestrol, dienestrol, stilbestrol, ethynylestradiol and zeranol. The method includes extractive homogenization of 10 g of meat in tetrahydrofuran, followed by liquid-liquid partition between acetonitrile and hexane and finally a chromatographic purification step on a small silica gel column. Gas chromatography was carried out on a 10-m glass capillary column coated with SE-54 using a temperature program from 100 to 250 degrees C. The capillary column was connected to the ion source by an all-glass open-split interface with a scavenger gas-line. Detection of anabolic residues was performed with selected ion monitoring on intensive ions in the mass region above m/e 400, resulting in a detection limit of 1-5 ppb (10(9)). Quantitative determinations were performed using dodecyl gallate as an internal standard applying the signal ratio of the drug and the standard.
Animals↗
Microbiological studies investigation mutagenicity of deep frying fat fractions and some of their components.
In this study, the Salmonella/microsome mutagenicity test according to Ames et al. (Mutation Res. 31:347, 1975) was performed in order to detect possible mutagenicity of oxidized deep frying fat fractions. Furthermore, the mono-, di-, tri- and tetrahydroxyoctadecanoic acids and the hydroperoxide of linoleic acid were investigated as model test substances. The Ames assay was carried out with and without metabolic activation including preincubation and liquid culture procedures as described by Mitchell (Mutation Res. 54:1, 1978). The results show no mutagenic effects for the oxidized fractions of deep frying fats nor for the model test substances. At higher concentrations, however, limited test reliability resulted from direct toxic effects on bacterial growth.
Animals↗