Determination of carbamate pesticides and some urea pesticides after derivatization with acetic anhydride by means of GC-MSD

Summary A simple method for the determination of several thermolabile carbamate and urea pesticides as acetyl derivatives by means of capillary gas chromatography is described. 10 carbamate and 6 urea pesticides yielded thermostable derivatives which can easily be analysed by GC-MSD at the relevant residue levels as demonstrated with food samples. The method was designed to be used in addition to a popular multimethod (S19 — DFG Pesticide Commission).Part of this paper was presented at the Seventh International Congress of Pesticide Chemistry, Hamburg, August 5–10, 1990     

Determination of thermolabile urea pesticides after derivatization with HFBA using GC-ECD and confirmation by means of GC-MSD

Summary The determination of urea pesticides is difficult by means of gas chromatography because they undergo thermal decomposition when applying standardized chromatographic conditions as used in multiresidue analysis. A method is therefore described to make possible the detection of these compounds by gas chromatography after derivatization with HFBA using either electron capture and nitrogen-phosphorus detection or a mass spectrometer as detector.Part of this paper was presented at the Seventh International Congress of Pesticide Chemistry, Hamburg, August 5–10, 1990.     

Identification of ω-oxocarboxylic acids as acetal esters in aerosols using capillary gas chromatography-mass spectrometry

An homologous series of ω,ω-dimethoxycarboxylic acid methyl esters (acetal esters) has been identified in the most polar methyl ester fraction separated from remote aerosol samples by liquid chromatography. These compounds were separated by silica gel column chromatography and their structures determined by capillary gas chromatography (GC) and GC—mass spectrometry with a synthesized standard. The acetal esters are originally present in the samples as ω-oxocarboxylic acids, which are derivatized to acetal esters during treatment with boron trifluoride in methanol. This method enables the determination of ω-oxocarboxylic acids in environmental samples as their acetal esters.     

Decontamination of pesticide packing using ionizing radiation

The Brazilian agriculture activities have consumed about 288,000 tons of pesticides per year conditioned in about 107,000,000 packing with weight of approximately 23,000 tons. The discharge of empty plastic packing of pesticides can be an environmental concern causing problems to human health, animals, and plants if done without inspection and monitoring. The objective of this work is to study the ionizing radiation effect in the main pesticides used in Brazil for plastic packing decontamination. Among the commercial pesticides, chlorpyrifos has significant importance because of its wide distribution and extensive use and persistence. The radiation-induced degradation of chlorpyrifos in liquid samples and in polyethylene pack was studied by gamma radiolysis. Packing of high-density polyethylene (HDPE) three layer coextruded, named COEX, contaminated with chlorpyrifos, were irradiated using both a multipurpose Co-60 gamma irradiator and a gamma source with 5000 Ci total activity Gamma cell type. The chemical analysis of the chlorpyrifos was made using a gas chromatography associated to the Mass Spectrometry—GCMS from Shimadzu Model QP 5000. Gamma radiation was efficient for removing chlorpyrifos from the plastic packing, in all studied cases.     

Kapseldosierung in der Gas-Chromatographie: Präzision und Reproduzierbarkeit

Zusammenfassung Es konnte gezeigt werden, daß das manuelle Kapseldosier-system bei der Aufgabe flüssiger Proben zu sehr genauen und reproduzierbaren Ergebnissen führt. Die erreichbaren Genauigkeiten — charakterisiert durch die Angabe der relativen Standardabweichungen — liegen zwischen etwa 0,1 und 0,3%.

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Capsule injection in gas chromatography: Precision and reproducibility

Summary It is shown that the manual capsule injection system for the introduction of liquid samples can give results of very high precision and reproducibility. The precision values that can be attained — characterized by the relative standard deviation — are between approximately 0.1 and 0.3%.

     

Enorme Unterschiede in der qualitativen und quantitativen Zusammensetzung der Fettsäurefraktion von rohem und gekochtem Gemüse

Summary Potato tubers und vegetables, introduced into the body contain — in dependance if boiled or not — very different amounts of multiple unsaturated fatty acids. In boiled vegetables linoleic and linolenic acid remain unchanged. In contrast, if the vegetable is shred and then analysed, the content of multiple unsaturated fatty acids is lowered for a factor of 2–5. If vegetable is shred, lipoxygenases are liberated, resulting in oxidizing the multiple unsaturated acids. The lipoxygenases are destroyed if vegetable is cooked before shreding. An easy comparison of the effect of lipoxygenases on fatty acid can be made by gas chromatography. The effect is especially strong incruciferae e.g. in cabbage or cauliflower.

     

Determination of organophosphorus pesticides in aqueous samples by on-line membrane disk extraction and capillary gas chromatography

Summary A fast and simple procedure for the analysis of aqueous samples by on-line membrane disk extraction and capillary gas chromatography (GC) is presented. As an example, organophosphorus pesticides are preconcentrated from aqueous samples on three 0.5 mm thick, 4.2 mm diameter extraction disks. The layers are dried by a stream of nitrogen (10–15 min; ambient temperature). Desorption of the analytes is carried out with ethyl acetate which is directly introduced into a retention gap under partially concurrent solvent evaporation conditions, using an early solvent vapour exit. The final analysis is carried out by GC with thermionic detection. The technique is applied to the determination of a series of organophosphorus pesticides in tap water and water from two European rivers. With a sample volume of only 2.5 ml, detection limits of 10–30 ppt are achieved in tap water and of 50–100 ppt in river water.     

Colloid stationary phases containing aerosil

Summary Binary colloid systems, including aerosil and an organic modifier (e.g. polyethylene glycol 400 or squalane) are suggested as stationary phases for gas chromatography. The dependence of solute retention on the composition of the phases is studied and the influence of the sol — gel transition on the retention indicated.     

Detection of organophosphate pesticides in human body fluids by headspace solid-phase microextraction (SPME) and capillary gas chromatography with nitrogen-phosphorus detection

Summary Organosphosphate pesticides have been found extractable by headspace solid-phase microextraction (SPME), and the best conditions of their extraction from human whole blood and urine samples have been investigated. The body fluid samples containing nine pesticides (IBP, methyl parathion, fenitrothion, malathion, fenthion, isoxathion, ethion, EPN and phosalone) were heated at 100°C in a septum-capped vial in the presence of various combinations of acid and salts, and SPME fiber was exposed to the headspace of the vial to allow adsorption of the pesticides before capillary gas chromatography (GC) with nitrogen-phosphorus detection. The heating with distilled water/HCl/(NH₄)₂SO₄/NaCl and with distilled water/HCl gave the best results for urine and whole blood, respectively. Recoveries of the nine pesticides were 0.8–10.6% except for phosalone (0.03%) for whole blood, and 3.8–40.2% for urine. The calibration curves for the pesticides showed linearity in the range of 50–400 ng/0.5 mL for whole blood except for malathion (100–400 ng/0.5 mL whole blood) and 7.5–120 ng/0.5 mL for urine except for phosalone (15–120 ng/0.5 mL urine) with detection limits of 2.2–40 ng/0.5 mL for whole blood and 0.8–12 ng/0.5 mL for urine.     

Determination of 77 Multiclass Pesticides and Their Metabolitesin Capsicum and Tomato Using GC-MS/MS and LC-MS/MS

A quick, sensitive, and reproducible analytical method for the determination of 77 multiclass pesticides and their metabolites in Capsicum and tomato by gas and liquid chromatography tandem mass spectrometry was standardized and validated. The limit of detection of 0.19 to 10.91 and limit of quantification of 0.63 to 36.34 µg·kg⁻¹ for Capsicum and 0.10 to 9.55 µg·kg⁻¹ (LOD) and 0.35 to 33.43 µg·kg⁻¹ (LOQ) for tomato. The method involves extraction of sample with acetonitrile, purification by dispersive solid phase extraction using primary secondary amine and graphitized carbon black. The recoveries of all pesticides were in the range of 75 to 110% with a relative standard deviation of less than 20%. Similarly, the method precision was evaluated interms of repeatability (RSDr) and reproducibility (RSD_wR) by spiking of mixed pesticides standards at 100 µg·kg⁻¹ recorded anRSD of less than 20%. The matrix effect was acceptable and no significant variation was observed in both the matrices except for few pesticides. The estimated measurement uncertainty found acceptable for all the pesticides. This method found suitable for analysis of vegetable samples drawn from market and farm gates.     

Analyse von Organochlorpestizid-und PCB-Rückständen in Fischen mittels Kapillargaschromatographie/Massenspektrometrie

Zusammenfassung Es wird die Analyse neutraler organischer Chlorverbindungen in Fischen beschrieben. Die Methode umfaßt Extraktion, selektive Vortrennung und Bestimmung mittels GC/MS an Glastrennkapillaren. Weiter werden die Ergebnisse einer für oberösterreichische Flüsse typischen Fischprobe vorgestellt und diskutiert: Wie in den meisten Proben dieses Ursprungs findet man — im Vergleich zu einem Gehalt von 6.1 ppm PCB's — relativ wenig Pesticidrückstände. Der Chlorierungsgrad der gefundenen PCB's entspricht etwa dem von Aroclor 1254; die abweichende Isomerenverteilung deutet auf unterschiedliche Persistenz der einzelnen Isomere hin.

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Analysis of organochlorine pesticides and PCB residues in fish by capillary gas chromatography/mass

Summary The analysis of neutral organochlorine compounds in fish is described. The method includes extraction, selective clean-up and GC/MS determination using glass capillary columns. The results of a typical fish sample coming from Upper Austrian rivers are presented. In comparison with the detected concentration of 6.1 ppm PCB's relatively low amounts of pesticide residues were found. The degree of chlorination of these PCB's is similar to that of Aroclor 1254, but the isomeric distribution is quite different, indicating varying persistence of the distinct isomers.

     

Interactions of copper tetra-tert-butylphthalocyanine with nitrogen- and sulfur-containing compounds in solutions

Interactions of ammonia, aliphatic amines, hydrogen sulfide, and sulfur dioxide with copper tetra-tert-butylphthalocyanine (CuPc) in squalane were studied by spectrophotometry and gas liquid chromatography in the CuPc concentration range of 1·10^–3—5·10^–2 mol L^–1. The sorption properties of the CuPc—squalane stationary liquid phases (SLPs) are governed by the physicochemical nature of the CuPc nanoaggregates in solution. The -type nanoaggregates exhibit particularly high activity to hydrogen sulfide; the activities to primary and secondary amines are also high.     

Determination of organochlorine pesticides in animal diet: A comparative study of clean-up procedures

Four clean-up procedures for the determination of 15 organochlorine pesticides in animal diet are studied. These methods imply the use of solid adsorbents such as Silica-gel, Florisil, the use of a combined bed of Silica-gel and Florisil, as well as, HPLC — size exclusion chromatography. The recovery of each compound is considered as acceptable when the value is higher than 80%. The behaviour of each produre with the animal diet sample is studied. A certified reference material of animal diet is used to validate the proposed procedure.     

Synthesen in der Pyridazin-Reihe, 26. Mitt.:

Zusammenfassung Es wird über die Synthese von verschiedenen methylsubstituiertens-Triazolo[4,3—b]pyridazinen berichtet. Außerdem wurdens-Triazolo[4,3—b]pyridazin und seine 7-Methyl- und 6-Chlor-Derivate der homolytischen Methylierung unterworfen, die Reaktionsgemische gaschromatographisch auf einzelne Methyl-s-triazolo[4,3—b]pyridazine aufgetrennt und die Verbindungen identifiziert.

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Syntheses of pyridazines, XXVI: Synthesis and homolytic methylation of s-triazolo[4.3—b]pyridazines

The syntheses of some methyl substituteds-triazolo[4,3—b]-pyridazines are reported.s-Triazolo[4.3—b]pyridazine and its 7-methyl and 6-chloro analogs were submitted to homolytic methylations and the obtained reaction mixtures were separated by gas chromatography into particular components which were then identified.

     

A multiresidue method using ion-trap gas chromatography–tandem mass spectrometry with or without derivatisation with pentafluorobenzylbromide for the analysis of pesticides in the atmosphere

A multiresidue method using gas chromatography coupled to ion-trap tandem mass spectrometry (MS/MS) was developed for the analysis of 27 pesticides, commonly used in Alsace, in atmospheric samples (particle and gas phases). As pesticides are expected to be present at very low concentrations and in a complex matrix, the analytical method used was both highly selective and sensitive. These two properties were obtained by associating chromatography with ion-trap MS/MS. To develop this method, analysis of electron impact in single MS was first conducted to choose the parent ions of the pesticides studied. Among the 27 pesticides analysed, seven of them require a derivatisation step. This was the case of some ureas (chlorotoluron, diuron and isoproturon), phenoxy acids (2,4-dichlorophenoxyacetic acid, 4-chloro-2-methylphenoxyacetic acid and mecoprop) and of bromoxynil. The derivatisation was performed with success with pentafluorobenzylbromide. Then, a MS/MS method was optimised by parameters such as the radio frequency storage level and the collision-induced dissociation excitation voltage. Finally, a last step enabled the development of two calibrating programs based on the quantification of daughter ions for the 20 pesticides analysed directly (run 1) and for the seven pesticides which needed derivatisation (run 2). With this analytical procedure, the detection limits varied between 2.5 and 1,250 pg m^–3 depending on the compounds studied. This method was tested with success for atmospheric samples collected in Strasbourg (France) during intensive pesticide treatment in 2002.     

Separation, detection and occurrence of (C2–C8)-alkyl- and phenyl-alkyl nitrates as trace compounds in clean and polluted air

Nitric acid, HNO₃, and nitrous acid, HNO₂, are forming stable esters with alcohols, the alkyl nitrates and alkyl nitrites. Both groups of compounds are used as fuel additives, explosives and pharmaceuticals. Alkyl nitrates are also formed as complex mixtures during incomplete combustion and the abiotic transformation of alkanes, alkenes and aldehydes in air. Organic nitrates can be assigned to anthropogenic and natural sources alike. Here the synthesis of reference mixtures of alkyl nitrates is described starting with alcohols, alkyl bromides, alkyl iodides or alkanes, respectively, sampling techniques in air analysis, and the separation of alkyl nitrates and alkyl dinitrates by high resolution capillary gas chromatography using various stationary phases and electron capture (HRGC/ECD) as well as mass spectrometric detection (HRGC/MSD). A highly selective detection mode for alkyl nitrates and alkyl di- and trinitrates — in general in the presence of other organic trace compounds — is the single ion monitoring of 46 amu in GC/MS. The separation and occurrence of alkyl- and phenyl-alkyl nitrates in polluted air is reported using capillary gas chromatography with electron capture and ion trap MS detection. The reaction of alkanes with nitric acid at room temperature simulates in a good approximation the pattern of alkyl nitrates formed in air chemistry.     

Coupling techniques in speciation analysis

Summary Direct coupling techniques in speciation analysis lead to reproducible results with lower risks of trace contamination or losses of analytes in a shorter period of time. The direct coupling mode seems to be most promising for liquid chromatographic separation methods — especially gel permeation chromatography — and for some electrophoretic methods — as flow-through and capillary techniques. Promising detection methods are Flame-AAS and ICP-OES but also hydride-generation AAS and chemical reaction detectors in continuous-flow technique.     

Studies on terpenes. II

Summary Fifty esters of monoterpene alcohols — mainly acetates — are investigated by gas chromatography on Apiezon-L and Carbowax 20 M and also by argentation thin-layer chromatography. The relationship between the retention indices, -Ivalues, R_f-values and structure of the esters is discussed.

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Zusammenfassung Fünfzig Ester von Monoterpenalkoholen — hauptsächlich Acetate — wurden mit Hilfe der Gas-Chromatographie auf Apiezon L und Carbowax 20 M sowie der Dünnschicht-Chromatographie auf AgNO₃-haltigen Silicagel-Schichten untersucht. Die Zusammenhänge zwischen den Retentionsindices, I-Werten, R_f-Werten und der Struktur der Ester werden diskutiert.

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Part. I: J. Chromatog. 7, 297 (1962).     

Rapid pesticide analysis,in post-harvest plants used as animal feed,by low-pressure gas chromatography–tandem mass spectrometry

A wide range of pesticides used to control pests in vegetables have been determined in agricultural plant waste from beans, watermelons, and melons grown in greenhouses located in a predominantly agricultural area in Southeast Spain (Almería). Analysis of the pesticides was carried out by low-pressure gas chromatography (LP-GC) with mass spectrometry in tandem (MS–MS) mode, after extraction of the lyophilized samples with dichloromethane. The influence of the sample matrix on the analysis was avoided by use of matrix-matched standards. Linearity, detection limit (LOD), quantitation limit (LOQ), recovery, and precision for each pesticide were calculated. The most frequently encountered pesticides were endosulfan (>73% of the analyzed samples) and buprofezin (>55% of the samples), followed by cypermethrin, pirimifos-methyl, bifentrin, and chlorpyrifos (>30% of the samples). The pesticide found at the highest concentration level was endosulfan (223.33 mg kg^–1) in a watermelon sample.