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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. [ABSTRACT FROM AUTHOR]

The search on endocrine disrupting chemicals (EDCs) in non-fatty food was evaluated. A fast, high-throughput, accurate, multiresidue method for the analysis of selected EDC pesticides in fruit and vegetable food samples was developed. The QuEChERS technique was used for sample preparation. Fast GC-MS was performed with a narrow-bore capillary column and a quadrupole benchtop detector with electron ionization (EI) and negative chemical ionization (NCI). A part of the work was devoted to the comparison of NCI versus EI approach concerning the sensitivity of detection and to the study of selectivity enhancement in NCI mode. Matrix-matched standard solutions were utilized for calibration. The methods validation was performed. Fortification studies at 1, 5, 10 and 250 µg kg−1 for 35 pesticides in EI mode and 0.1, 1, 5 and 250 µg kg−1 for 28 pesticides in NCI mode were performed. Average recoveries for each fortification level ranged from 70 to 110% with >80% of recoveries between 90 and 110%. Limits of quantification (LOQs) were established at 5 µg kg−1 for EI and at 1 µg kg−1 for NCI mode, which is lower than the lowest maximum residue level (MRL) value set by the European Commission in fruit and vegetables. The developed and validated fast GC-MS method was successfully applied to the search of EDC pesticides at ultratrace concentration level in real fruit and vegetable samples in Slovakia. Thirty-four samples of 20 different commodities were analyzed. Seven samples contained residues of three or more EDCs pesticides. [ABSTRACT FROM AUTHOR]

An analytical method has been developed and evaluated for the determination of endocrine disrupting chemicals (EDCs)-pesticides in non-fatty food. Twenty-nine analytes of different chemical classes according to EDCs draft list of European Commision were selected. The method is based on fast GC-MS with bench top quadrupole MS detector and electron impact (EI) ionisation (70 eV). For the effective separation programme temperature vaporiser (PTV) injector and narrow-bore column were used. Slightly modified QuEChERS sample preparation technique was applied for the preparation of apple extracts for matrix-matched standards, synthetic sample and real sample extracts. Two internal standards (I.S.)-heptachlor (HPT) and triphenylphosphate (TPP)-were used. The results needed for the method validation were calculated from absolute peak areas and normalised areas to HPT and TPP. The important part of the study is the utilisation of analyte protectants (APs). Three calibrations approaches: matrix-matched standards without/with APs and acetonitrile (MeCN) standards with APs were used. The best results were obtained with matrix-matched standards without APs. The developed and validated analytical method was used for the identification and quantification of EDCs pesticides in real samples (orange, lettuce, strawberry and plum). [ABSTRACT FROM AUTHOR]

In the analysis of pesticide residues by GC including GC-MS, adverse effects caused by matrix co-extractives occurs which results in worse precision and trueness of analytical results. Sample extracts of various commodities (fruit and vegetables), prepared by the QuEChERS method were evaluated by gravimetric analysis to compare co-extracted compounds amount. For comparison of matrix background measurement of acetonitrile (MeCN) extracts in full scan mode and SIM monitoring were performed utilising fast GC-MS with quadrupole analyser and narrow-bore columns. In order to evaluate the trueness of quantitative analysis results utilising different calibration standards experiments with synthetic samples (it is a blank sample extract from selected fruit and vegetables-apples, pear, cucumbers and cauliflowers, with the addition of pesticides at the concentration level of 0.05 ng µL-1 (50 µg kg-1)) were performed in this work. This sample represents a simulated real sample, but with the known concentration to check the various calibration approaches utilising calibration standards that would be used in practice: (1) in organic solvent (MeCN) with addition of analyte protectants (APs), (2) matrix-matched standard, (3) matrix-matched standard with addition of APs. For most of studied pesticides very good match of concentration was obtained utilising matrix matched standards (with/without APs). For the majority of the pesticides under study significant overestimation of concentration was observed in acetonitrile standards with APs in all matrices. Repeatability of measurements expressed as relative standard deviations (RSDs) of determined pesticides concentration in all tested matrices was ≤14%. [ABSTRACT FROM AUTHOR]

Abstract: The study of pesticide residues belonging to endocrine disrupting chemicals (EDCs) (23 analytes of different chemical classes – organochlorines, organophosphates, pyrethroids, dicarboximides, phtalamides, dinitroanilines, pyrazole, triazinone) in apple matrix with conventional capillary GC–NCI-MS (with methane as reagent gas) in comparison to EI ionization is presented. For sample preparation QuEChERS method was applied. The lowest calibration levels (LCLs) for all pesticides were determined in both modes. Calibration in the NCI mode was performed at the concentration levels from 0.1 to 500μgkg−1 (R 2 >0.999) and for EI in the range from 5 to 500μgkg−1 (R 2 >0.99). From LCLs the instrumental limits of detection (LODs) and quantification (LOQs) were calculated. Chemometric study of pesticide signals in two MS modes was performed. Repeatability of all measurements, expressed by the relative standard deviations of absolute peak areas was better than 10% for the majority of compounds. Significantly lower values were obtained for the NCI mode. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

The results of a systematic study on the precision and repeatability of measurements of the headspace solid phase micro-extraction (SPME) with open-cap vials in combination with capillary gas chromatography in comparison with septum-sealed vials are reported. Benzene, toluene, ethylbenzene, and xylene isomers (BTEX) were used as the target analytes in the investigation of spiked water samples at concentration levels of 42.5 μg l−1. The dependence of a sample volume versus peak area showed maximum SPME recovery. The influence of sample volume on the precision and the time of taking the sample on the losses of volatile analytes was examined. [Copyright &y& Elsevier]

Minimal time of operation in gas chromatography (GC) has been a research topic ever since the introduction of GC. Today, revived interest in fast GC is seen to be driven by applications, such as process control and high-throughput analysis, or by the desire to reduce the costs of operation and ownership in routine analysis. Numerous options exist for speeding up GC separations. Which option to select depends strongly on the application under study. The first step should always be to see if it is possible to trade resolution for time. If this approach fails, the concept of “resolution-normalised conditions” comes into play. An overview of options for faster chromatography and a system for classifying chromatograms are brought together to give guidelines for speeding up specific applications. The practical consequences of implementing these options are discussed and the instrumental requirements are outlined. Applications of the various methods for faster GC are given. [Copyright &y& Elsevier]