Analysis Of Pesticide Residues In Fruits Research Articles

Validation of Analytical Methods Used for Pesticide Residue Detection in Fruits and Vegetables

Injudicious and ever-increasing use of pesticides has made consumers more aware and critical about quality control and quality assurance in fruits and vegetables. Presence of pesticide residues in food commodities is one of the most indispensable parameters in quality control and quality assurance. To meet out the demand of acceptable or no residues in crops, different agencies viz. Codex Alimentarius Commission, European Union, FSSAI etc. have assigned maximum residue limits for different pesticides on different crops. As these residues are present in very small quantities, their extraction and quantification involve the use of very effective and sensitive analytical methods and instruments. Different accreditation bodies have fixed analytical parameters to be met out by the pesticide residue laboratories so as to detect the pesticide residues with high precision and accuracy. Some of these parameters are linearity, accuracy, precision, limit of detection, limit of quantitation, and specificity etc. Validation of analytical methods is one such essential parameter in establishing the analytical quality control for detection of pesticide residues and also an essential component to meet out the requirements of different accreditation bodies. In the present paper, an attempt has been made to make an overview of the validation of analytical methods employed in pesticide residue analysis globally. The present review focuses on methods validated by different workers for residue detection along with each analytical parameter covered for validating the analytical methods. This compilation will be a useful tool to the analysts working on pesticide residue analysis in fruits and vegetables.

Dual-channel chromatography a smart way to improve the analysis efficiency in liquid chromatography coupled to mass spectrometry

Dual-channel chromatography was evaluated for pesticide residue analysis in fruits and vegetables and for unknown compounds detection. A dual-channel system was tested coupled to triple quadrupole and high-resolution mass spectrometry. The first part of the investigation was related to the improvement of the sample throughput with a 100 mm column. The dual-channel system provided the same analytical results as the single-channel system, however, with the throughput higher of about 70% (80 injections vs 137 injections in 24 h). Two types of calibration (in-channel and cross-channel) were checked. In the article, also solvent consumption is discussed. Six proficiency test samples were analysed to assess the quality of the results. Nor false positives neither false negatives were found. Calculated z-scores were typically <1. In the second part, a different approach was investigated. The 100 mm column was replaced by a 150 mm column keeping shorter run times than single channel system and 100 mm. The longer column improved the sensitivity and selectivity what was demonstrated in the target pesticide residue analysis. Additionally, the 150 mm column was compared with the 100 mm column in the analysis of unknown natural matrix compounds by high resolution mass spectrometry. The longer column allowed to detect up to 26% unknown compounds more than the shorter column.

Review of Ionic Liquids in Microextraction Analysis of Pesticide Residues in Fruit and Vegetable Samples

The objective of this work is to provide a critical review of the use of ionic liquids in the microextraction of pesticide residues in fruits and vegetables. It includes an assessment of the advantages and limitations of current applications of ionic liquids in microextraction techniques. The review also aims to illustrate the impact of ionic liquids on the development of novel sorbent materials for analytical applications. The unique physicochemical properties of ionic liquids make them ideal sorbents in separation techniques. Their number of applications in analytical separation has increased considerably over the past 5 years. Therefore, this review focuses on the synthesis, purification, functionalization, and application of ionic liquids for pesticide residue analysis in fruits and vegetables with different sample preparation procedures, covering articles published in the literature since their first application in 2009.

Polyethyleneimine as weak anionic exchanger adsorbent for clean-up in pesticide residue analysis of fruits and vegetables

Pesticide residue analysis in fruits and vegetables is generally performed with the QuEChERS method, when clean-up is mainly achieved with primary secondary amine (PSA) by dispersive solid phase extraction (dSPE). In this work, we present a rapid and efficient method for the clean-up of fruit and vegetable extracts with polyethyleneimine (PEI) as alternative to PSA. Clean-up of QuEChERS extracts with a mixture of branched PEI adsorbed on magnesium sulfate and silica gel was realized in 10 min, when several polar matrix components were clearly reduced. The success of the clean-up for representative matrices was visualized by both high-performance thin-layer chromatography with different detection options and total ion current chromatograms of liquid chromatography–mass spectrometry analyses. Generally, dSPE clean-up with PEI was at least equally effective as dSPE with PSA, but PEI clearly superimposed PSA in terms of adsorption capabilities towards fatty acids. After clean-up of fatty acid mixtures with 150 and 300 mg/L, total fatty acids were reduced by 98% and 99%, respectively, while PSA left two- and three-fold quantities. Additionally, the susceptibility of base-labile pesticides towards PEI as compared to PSA generally was negligible, further supporting the high suitability of PEI for clean-up in pesticide residue analysis. Thus, clean-up with PEI enables a clear reduction of various matrix compounds in fruit and vegetable extracts and provides a rapid, convenient and low-cost alternative to the existing dSPE methods with PSA.

Screening for total ergot alkaloids in rye flour by planar solid phase extraction–fluorescence detection and mass spectrometry

The analysis of ergot alkaloids is generally performed by high-performance liquid chromatography (HPLC) coupled to fluorescence detection (FLD) or mass selective detection. As for monitoring only the sum of ergot alkaloids is relevant, a fast and easy screening method for the determination of the total alkaloid content was developed using planar solid phase extraction (pSPE). Applying pSPE, recently introduced for pesticide residue analysis in fruits and vegetables (Oellig and Schwack, 2011) and tea (Oellig and Schwack, 2012), all ergot alkaloids are concentrated in a target zone followed by detection as the sum. The herein presented method includes an ammonium acetate buffered extraction step, followed by a fast liquid–liquid partitioning pre-cleaning before pSPE is performed on high-performance thin-layer chromatography (HPTLC) amino plates with a single methanol development to separate the ergot alkaloids from the remaining matrix and to collect them in a single zone. For quantitation, the native fluorescence was used after dipping the plate in n-hexane/paraffin solution for fluorescence enhancement. Limits of detection and quantitation of 0.07 and 0.24mg/kg rye, respectively, expressed as ergocristine, were well below the currently applied quality criterion limit for rye. Near-100% recoveries were obtained at relevant spiking levels for different rye flour samples. Hence, the fast pSPE–FLD is an efficient and reliable method to screen for the total ergot alkaloid content in rye and a rapid alternative to the HPLC determination of individual alkaloids and to summing them up. HPTLC–MS additionally enables the identification of the ergot alkaloid composition by a single mass spectrum, when utilized as a fingerprint, offering an easy differentiation of Secale cornutum from different origins.

Large pesticide multiresidue screening method by liquid chromatography-Orbitrap mass spectrometry in full scan mode applied to fruit and vegetables

The present work is focused on evaluating the main operational parameters for multiresidue screening of an Orbitrap mass spectrometer for pesticide residue analysis in fruits and vegetables. Operational parameters such as resolution, software for the automatic detection, mass tolerance and retention time extraction window, along with the analytical performance, were evaluated in an updated UHPLC-Orbitrap-mass spectrometer working in full scan mode. The evaluation was performed using QuEChERS extracts of tomato, pepper, orange and green tea. The extracts were spiked with 170 selected pesticides at four concentration levels (10μg/kg, 50μg/kg, 100μg/kg and 500μg/kg). Extracts were diluted 5 fold before injection. Three different resolution settings (17,500, 35,000 and 70,000) were evaluated at various concentration levels. At 10μg/kg, using a resolution of 17,500 and 5ppm of mass tolerance, the detected pesticide rates were from 91% in tomato, to 83% in green tea. These percentages increased at higher resolution values. A resolution of 70,000 was adequate for such analysis even when a small percentage of false detect at low concentration was obtained. The rates of detected compounds increased and were from 98% in tomato to 88% in green tea. Mass tolerance of 5ppm was the most adequate for screening purposes. The observed false negative detects were mainly a consequence of a lack of compound sensitivity exacerbated by ion suppression effects in the experimental conditions applied. With reporting limits of 10μg/kg, reproducibility improved with resolution levels of 35,000 or higher. Linearity was investigated in the 2–100ng/mL (equivalent to 10–500μg/kg in the sample) range. Particularly good automatic screening effectiveness was obtained using the selected settings in the analysis of real samples where no false negatives detects and 5% of false positives detects were obtained.

Planar solid phase extraction clean-up and microliter-flow injection analysis–time-of-flight mass spectrometry for multi-residue screening of pesticides in food

For multi-residue analysis of pesticides in food, a sufficient clean-up is essential for avoiding matrix effects in liquid and gas chromatography (LC and GC) analysis coupled to mass spectrometry (MS). In the last two years, high-throughput planar solid phase extraction (HTpSPE) was established as a new clean-up concept for pesticide residue analysis in fruits and vegetables (C. Oellig, W. Schwack, 2011) and tea (C. Oellig, W. Schwack, 2012). HTpSPE results in matrix-free extracts almost free of interferences and matrix effects. In this study, a time-of-flight mass spectrometer (TOFMS) was applied to directly analyze HTpSPE extracts for pesticide residues. This HTpSPE–microliter-flow injection analysis (μL-FIA)–TOFMS approach detects all pesticides at once in a single mass spectrum, without a liquid chromatographic separation step. Complete sample information was obtained after the injection of the cleaned extract within a single peak. Recovery studies for seven representative pesticides in four different matrices (apples, red grapes, cucumbers, tomatoes) provided mean recoveries of 86–116% with relative standard deviations of 1.3–10% (n=5) using the mass signal intensities under the entire sample peak. Comparing the mass spectra of sample peaks from spiked extracts and solvent standards indicated the efficiency of HTpSPE clean-up. A pesticide database search detected all spiked pesticides with a low incidence of false-positives. HTpSPE of one sample required a few minutes, and numerous samples could be cleaned in parallel at minimal cost with low sample and solvent consumption. The μL-FIA–TOFMS screening then needed an additional 6min per sample. The novel screening approach was successfully applied to QuEChERS extracts of several real samples, and the pesticides identified by HTpSPE–μL-FIA–TOFMS were identical to the pesticides detected by common target LC–MS/MS analyses. The high degree of concordantly identified pesticides by the new developed HTpSPE–μL-FIA–TOFMS approach and target LC–MS/MS demonstrates the applicability as a routine screening method.

Improved gas chromatography–tandem mass spectrometry determination of pesticide residues making use of atmospheric pressure chemical ionization

The capabilities of a recently launched atmospheric pressure chemical ionization (APCI) source for mass spectrometry (MS) coupled to gas chromatography (GC) have been tested in order to evaluate its potential in pesticide residue analysis in fruits and vegetables. Twenty-five pesticides were selected due to their high fragmentation under electron ionization (EI), making that the molecular ion (M+) is practically absent in their spectra. The fragmentation of these pesticides under APCI conditions was studied, with the result that M+ was not only present but also highly abundant for most compounds, with noticeable differences in the fragmentation patterns in comparison with EI. Moreover, the addition of water as modifier was tested to promote the formation of protonated molecules ([M+H]+). Under these conditions, [M+H]+ became the base peak of the spectrum for the majority of compounds, thus leading to an increase of sensitivity in the subsequent GC–MS/MS method developed using triple quadrupole analyzer (QqQ). Highly satisfactory sensitivity and precision, in terms of repeatability, were reached and linearity was satisfactory in the range 0.01–100ng/mL. The developed methodology was applied to apple, orange, tomato and carrot QuEChERS fortified extracts in order to evaluate the matrix effects. In summary, the soft and reproducible ionization in the APCI source has greatly favored the formation of [M+H]+ oppositely to EI where abundant fragmentation occurs and where the molecular ions have low abundance or are even absent in the mass spectrum. In this way, the use of APCI has facilitated the development of tandem MS methods based on the selection of abundant [M+H]+ as precursor ion.

A Cost-Effective Screening Method for Pesticide Residue Analysis in Fruits, Vegetables, and Cereal Grains

This paper reports the results of studies performed to investigate the potential of applying thin layer chromatography (TLC) detection in combination with selected extraction and cleanup methods, for providing an alternative cost-effective analytical procedure for screening and confirmation of pesticide residues in plant commodities. The extraction was carried out with ethyl acetate and an on-line extraction method applying an acetone-dichloromethane mixture. The extracts were cleaned up with SX-3 gel, an adsorbent mixture of active carbon, magnesia, and diatomaceous earth, and on silica micro cartridges. The Rf values of 118 pesticides were tested in eleven elution systems with UV, and eight biotest methods and chemical detection reagents. Cabbage, green peas, orange, and tomatoes were selected as representative sample matrices for fruits and vegetables, while maize, rice, and wheat represented cereal grains. As an internal quality control measure, marker compounds were applied on each plate to verify the proper elution and detection conditions. The Rf values varied in the different elution systems. The best separation (widest Rf range) was achieved with silica gel (SG)—ethyl acetate (0.05–0.7), SG—benzene, (0.02–0.7) and reverse phase RP-18 F-254S layer with acetone: methanol: water/30:30:30 (v/v) (0.1–0.8). The relative standard deviation of Rf values (CVRf) within laboratory reproducibility was generally less than 20%, except below 0.2 Rf, where the CVRf rapidly increased with decreasing Rf values. The fungi spore inhibition, chloroplast inhibition, and enzyme inhibition were found most suitable for detection of pesticides primarily for confirming their identity or screening for known substances. Their use for determination of pesticide residues in samples of unknown origin is not recommended.

GC/MIP/AED Method for Pesticide Residue Determination in Fruits and Vegetables

This research describes the results of a gas chromatography/microwave induced plasma/atomic emission detection (GC/MIP/AED) method performed on a Hewlett-Packard 5921A system for pesticide residue analysis in fruits and vegetables. A total of 6 experiments were conducted: (1) sensitivity and linearity studies for elements S, P, Cl, and N by analyzing dursban; (2) a study of instrument response to Cl concentration in pesticide molecules; (3) organochlorinated pesticide recoveries; (4) organophosphate pesticide recoveries; (5) carbamate pesticide recoveries; and (6) investigation of metallic pesticides with plictran and vendex as standards. The rank according to sensitivity and linearity was found to be as follows: S-181 greater than P-178 greater than Cl-479 greater than N-174. Instrument response to the concentration of chlorine atoms in the pesticide molecule was linear, with a correlation coefficient of 0.89. Recoveries of organochlorinated pesticides were 91.7-109.3%, with the exception of citrus, whose recovery was affected by coeluting interferences. Organophosphate recoveries were 73.2% or higher, except for the cygon oxygen analog, which degraded in the GC system under all circumstances. Carbamate recoveries were inconsistent quantitatively; however, the information generated from elements N and S were useful for qualitative confirmation of other methods, such as LC postcolumn derivatization analysis. Overall, the GC/MIP/AED method is powerful for qualitative confirmation in pesticide residue analysis. The instrument's capability of acquiring multi-elements (Cl and P) selectively and accurately is an alternative method for organochlorinated and organophosphate pesticide residue analyses. In addition, the GC/MIP/AED system is easy to use, simple to maintain, and its chromatograms can be interpreted by any chromatography analyst without much prior training.