Svetlana Hrouzková

Analysis of pesticide residues by fast gas chromatography in combination with negative chemical ionization mass spectrometry

A combination of fast GC with narrow-bore column and bench top quadrupole mass spectrometer (MS) detector in negative chemical ionization (NCI) mode (with methane as reagent gas) is set up and utilized for the ultratrace analysis of 25 selected pesticides. The observed pesticides, belonging to the endocrine disrupting chemicals (EDCs), were from different chemical classes. A comparative study with electron impact (EI) ionization was also carried out (both techniques in selected ion monitoring (SIM) mode). The programmed temperature vaporizer (PTV) injector in solvent vent mode and narrow-bore column (15mx0.15mm I.D.x0.15microm film of 5% diphenyl 95% dimethylsiloxane stationary phase) were used for effective and fast separation. Heptachlor (HPT) as internal standard (I.S.) was applied for the comparison of results obtained from absolute and normalized peak areas. Non-fatty food matrices were investigated. Fruit (apple - matrix-matched standards; orange, strawberry, plum - real samples) and vegetable (lettuce - real sample) extracts were prepared by a quick and effective QuEChERS sample preparation technique. Very good results were obtained for the characterization of fast GC-NCI-MS method analysing EDCs pesticides. Analyte response was linear from 0.01 to 150microgkg(-1) with the R(2) values in the range from 0.9936 to 1.0000 (calculated from absolute peak areas) and from 0.9956 to 1.0000 (calculated from peak areas normalized to HPT). Instrument limits of detection (LODs) and quantification (LOQs) were found at pgmL(-1) level and for the majority of analytes were up to three orders of magnitude lower for NCI compared to EI mode. In both ionization modes, repeatability of measurements expressed as relative standard deviation (RSDs) was less than 10% which is in very good agreement with the criterion of European Union.

Multifamily determination of pesticide residues in soya-based nutraceutical products by GC/MS–MS

An analytical method based on a modified QuEChERS extraction coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was evaluated for the determination of 177 pesticides in soya-based nutraceutical products. The QuEChERS method was optimised and different extraction solvents and clean-up approaches were tested, obtaining the most efficient conditions with a mixture of sorbents (PSA, C18, GBC and Zr-Sep(+)). Recoveries were evaluated at 10, 50 and 100 μg/kg and ranged between 70% and 120%. Precision was expressed as relative standard deviation (RSD), and it was evaluated for more than 160 pesticides as intra and inter-day precision, with values always below 20% and 25%, respectively. Limits of detection (LODs) ranged from 0.1 to 10 μg/kg, whereas limits of quantification (LOQs) from 0.5 to 20 μg/kg. The applicability of the method was proved by analysing soya-based nutraceuticals. Two pesticides were found in these samples, malathion and pyriproxyfen, at 11.1 and 1.5 μg/kg respectively.

Combination of QuEChERS and DLLME for GC-MS determination of pesticide residues in orange samples

A new method combining QuEChERS (quick, easy, cheap, effective, rugged and safe) and DLLME (dispersive liquid–liquid microextraction) followed by gas chromatography-mass spectrometry with selected ion monitoring (SIM) was developed for the simultaneous determination of 19 pesticides from nine chemical groups exhibiting or suspected to exhibit endocrine-disrupting properties in orange samples. Acetonitrile extract obtained from QuEChERS extraction was used for DLLME as dispersive solvent and carbon tetrachloride as extractive solvent to increase the enrichment factor of the extraction procedure. The effect of several extraction parameters, such as volume extract achieved by the QuEChERS method and subsequently used for DLLME, selection of extractive solvent and its volume, was tested. Under optimum conditions, good linearity, satisfactory recoveries and repeatability were obtained. Limits of quantification (LOQs) achieved (ranging from 0.02 to 47 ng/g) were below the maximum residue limits established by the European Union. The proposed method was applied to the monitoring of pesticide residue levels in oranges commercialised in Portugal.

Liquid Phase Microextraction Techniques as a Sample Preparation Step for Analysis of Pesticide Residues in Food

Many conventional sample preparation methods are tedious, time-consuming, and use high volume of organic solvent. Minimized sample preparation methods, which use significantly smaller volume of organic solvent, represent an alternative to these methods. Three liquid phase microextraction (LPME) techniques: single drop microextraction, dispersive liquid-liquid microextraction, and hollow fiber liquid phase microextraction and a variety of its modifications are reviewed. Advantages and limitations are discussed. Extraction parameters influencing the extraction efficiency are evaluated. Applicability of LPME methods for pesticide residues analysis in various food matrices is overviewed. Determination of low-level pesticide residues was realized predominantly by chromatographic methods utilizing selective detectors. Powerful features of mass spectrometric detection for identification and determination of pesticide residues are pointed out.

Study on pesticide residues in apples, apple-based baby food, and their behaviour during processing using fast GC–MS multiresidue analysis

Food-processing experiments using apples were conducted to obtain more knowledge on the behaviour of pesticides during apple-based baby-food production. The residues were determined in raw material (apples), in intermediate products at different steps of the processing procedure (baby food production) and in final products (apple purée) using a rapid GC–MS method in combination with two different sample-preparation approaches. During 2 years of a monitoring programme, 84 analyses of apple samples and 102 of baby food sample apple purée intermediate and final product samples from baby food production were performed. A pesticide-residue search revealed that residues in fresh apples do not exceed the maximum residue limit for the adult population, but there were some positive findings concerning apples as baby food. The maximal pesticide concentration (fluquinconazole) found in apples was 0.099 mg kg−1. In the processed apple-based baby food the concentration of pesticide residues were mostly below 0.010 mg kg−1.

Analysis of Endocrine Disrupting Pesticides by Capillary GC with Mass Spectrometric Detection

Endocrine disrupting chemicals, among them many pesticides, alter the normal functioning of the endocrine system of both wildlife and humans at very low concentration levels. Therefore, the importance of method development for their analysis in food and the environment is increasing. This also covers contributions in the field of ultra-trace analysis of multicomponent mixtures of organic pollutants in complex matrices. With this fact conventional capillary gas chromatography (CGC) and fast CGC with mass spectrometric detection (MS) has acquired a real importance in the analysis of endocrine disrupting pesticide (EDP) residues. This paper provides an overview of GC methods, including sample preparation steps, for analysis of EDPs in a variety of matrices at ultra-trace concentration levels. Emphasis is put on separation method, mode of MS detection and ionization and obtained limits of detection and quantification. Analysis time is one of the most important aspects that should be considered in the choice of analytical methods for routine analysis. Therefore, the benefits of developed fast GC methods are important.

A comparative study of three modifications of the QuEChERS method for determination of endocrine disrupting pesticide residues in lemon matrices by fast GC-MS

Three modifications of the QuEChERS (quick, easy, cheap, effective, rugged and safe) method for determination of 35 endocrine disrupting pesticides in samples with high acid content such as lemons were studied. Pesticides extraction was performed using the original QuEChERS method, citrate buffered QuEChERS method (EU version) and acetate buffered QuEChERS method (AOAC version). Final extracts were evaluated by fast gas chromatography-mass spectrometry (GC-MS) analysis. Validation experiments for all three methods were performed using a spiked pesticide free lemon matrix and matrix-matched standard solutions. Four concentration levels (1, 20, 50 and 250 μg kg−1) were tested. Recoveries from 70 to 120% with a relative standard deviation <20% were obtained for the majority of pesticides. Linearity was evaluated at a concentration range of 1–250 μg kg−1 for the buffered QuEChERS (AOAC) method with coefficients of determination (R2) higher than 0.9552 and for the original QuEChERS method with R2 higher than 0.9232. The best linearity was obtained for the citrate buffered method with R2 higher than 0.9656. The limit of detection (LOD) of the buffered QuEChERS (AOAC) method ranged between 0.1 and 18.4 μg kg−1, for the citrate buffered QuEChERS method between 0.1 and 23.6 μg kg−1 and for the original QuEChERS method between 0.1 and 14.2 μg kg−1. Results obtained by the three different QuEChERS methods were compared. The citrate buffered method is more suitable for the tested pesticides than the other two QuEChERS methods. Although the QuEChERS method is widely applied, it was shown that in difficult matrices such as lemons, the choice of modifications is analyte/matrix dependent. The three developed and validated methods were applied to the analysis of real citrus samples.

Microextraction in packed syringe: solvent-minimized sample preparation technique

Abstract In recent years, great effort has been made to develop new analytical methods, such as microextraction techniques, that greatly reduce the limitations of conventional methods. Microextraction in packed syringe (MEPS) is a novel miniaturized solid-phase extraction (SPE) technique that works online with gas and liquid chromatography. MEPS is designed in the syringe format, wherein a small amount of the sorbent is packed between the barrel and the needle as a cartridge or inside a syringe as a plug. MEPS is a green sample preparation technique because of the small amount of sorbent used and the small volumes of solvent required. This article gives an overview of the successful approaches proposed concerning MEPS and provides the state of the art for biological, environmental, and food analyses. Selection of factors affecting MEPS performance is discussed. A comparison between MEPS and other techniques such as SPE, solid phase microextraction, and protein precipitation is provided.Graphical abstract

Endocrine disrupting pesticides

Food and environmental samples represent nowadays an enormous challenge to analytical chemists in their efforts to determine residues of pesticides at trace levels, as pesticides can represent a risk for consumer and also safeguard the biodiversity in the environment. The concern has increased as certain pesticides and other synthetic chemicals may act as pseudo hormones which disrupt the normal function of the endocrine system in humans and wildlife (Colborn et al., 1993; Lintelmann et al., 2003). This specific category of pollutants comprises the compounds that may affect the normal hormonal function or possess endocrine-related functions, known as endocrine disrupting chemicals (EDCs) or endocrine disrupters. During the last decades the interest and concern related to endocrine disrupters among scientists, regulators and public has increased. In the last years a great deal of concern has been expressed worldwide over the increasing levels of EDCs found in the environment. This anxiety is caused by the adverse effects of these pollutants on the hormone systems of humans and wildlife even when present at levels under ppb (Jobling, 2004).

Characterization of carbon sorbents for enrichment step in environmental analysis

Abstract The thorough study on physico-chemical properties of carbon sorbents belonging to different groups of sorbents—activated charcoal, molecular sieves—Carbosieve S-III, Carboxen 1000; porous carbons—Carb I, Carb II; graphitized carbon blacks—Carbopack B. Carbotrap, Carbotrap C is presented in this paper. Measurements of the surface area, pore size and volume on the base of adsorption isotherms and pore distribution measurements, measurement of particle size and evaluation of particle shape by microscopy, searching the sorbent morphology by scanning electron microscopy, evaluation of the quality of surface by 1H MAS-and 13C MAS solid-state NMR spectroscopy and elemental analysis were employed as means for the sorbent materials characterisation. Gas-solid chromatography (GSC) has been utilised to determine the specific retention volumes at 20°C, Vg(20°C), and isosteric heat of adsorption, qst, for organic compounds belonging to various groups-n-alkanes, aromatics, halocarbons, oxygenated compounds. On...