Comparing the VITEK 2 ANC card, species-specific PCR, and MALDI-TOF mass spectrometry methods for identification of lactic acid bacteria.

Lactic acid bacteria (LAB) are not only the most common probiotics in the food and feed industry but are also used as plant probiotics. Therefore, precise identification of LAB at the species level is required. In this study, we compared three different methods, the VITEK 2 ANC card, species-specific PCR, and MALDI-TOF MS, to identify six LAB (Lacticaseibacillus casei, Lacticaseibacillus paracasei, Lacticaseibacillus rhamnosus, Lactiplantibacillus plantarum, Lentilactobacillus buchneri, and Limosilactobacillus fermentum) species previously assigned to the genus Lactobacillus that are used as biofertilizers. Twenty-two strains of six LAB species were analyzed using the VITEK 2 ANC card, species-specific PCR, and MALDI-TOF MS, and identification rates at the species level were 45.5%, 95.5%, and 95.5%, respectively. There were cross-reactions between L. casei and L. parpacasei, and one strain of L. casei could not be identified by these three methods. PCR assays and MALDI-TOF MS were applicable for LAB identification. PRACTICAL APPLICATION: LAB are the most common probiotics in the food and feed industry, so precise identification and classification of LAB at the species level are required. This study aimed at comparing three different methods for the effective identification of six LAB species: biochemical testing using VITEK 2 ANC card, species-specific PCR, and MALDI-TOF MS analysis.

Development of a Gas Chromatography-Flame Ionization Method for the Detection and Quantification of 12 Flavoring Agents in Supplementary Feed.

A flavoring agent is a compound that serves to add flavor with a pleasant scent and is used as a feed additive. Current flavor analysis methods include reflux pretreatment, titration, neutralization titration, and inversion; these are all analytical methods in which deviations and errors between experiments are generated. Titration methods are characterized by difficult selectivity analysis both for mixtures containing two or more types of flavoring agents and also for very low content samples. Current analysis methods are therefore particularly unsuitable for these sample types. Thus, more precise and accurate analysis of flavor agents is needed. This study intends to develop and verify a multi-component simultaneous analysis method that can accurately confirm the guaranteed content of 12 flavor agents of supplementary feeds distributed in the market, the goal being to establish a universally trusted method. Method validation was performed according to the International Conference on Harmonization (ICH) and International Union of Pure and Applied Chemistry (IUPAC) guidelines. Method validation was performed in terms of linearity, sensitivity, selectivity, accuracy, and precision. The limits of detection (LOD) for the instrument employed in these experiments ranged from 0.44-4.77 mg/kg, and the limits of quantification (LOQ) ranged from 1.32-14.31 mg/kg. Average recoveries of the 12 flavoring agents ranged from 75.1-111.4%. Maximum %RSD values for intraday and interday peak area variation are 13.09% and 13.08%, respectively. A novel and simple method for detecting 12 flavoring agents in animal feed supplements using a gas chromatography-flame ionization detector (GC-FID) was developed.

Study on the Identification Methods for Effective Microorganisms in Commercially Available Organic Agriculture Materials.

The identification of microorganisms in closely related groups is challenging. The present work focused on the different molecular methodology for the accurate microbial identification in the five commercially available organic agriculture materials enriched with effective microorganisms. From the tested five organic agricultural materials, a total of seven distinct bacterial colonies (A-1, B-1, C-1, D-1, E-1, E-2, and E-3) were isolated and processed for sequential identification utilizing HiCrome™ Bacillus agar, biochemical tests with API CHB50, 16S rRNA gene analysis, random amplified polymorphic DNA (RAPD), and species-specific PCR analysis. All the isolated microorganisms were Gram-positive rods and spore former belonging to Bacillus group and appeared as a differential characteristic feature on HiCrome™ Bacillus agar. All isolates showed high-percentage similarities with the different members of Bacillus species in biochemical testing and 16S rRNA gene analysis. The collective identification results revealed isolates, A-1, B-1, and C-1, close to B. velezensis. Further RAPD-PCR and species-specific PCR discriminated and provided confirmatory evidence for D-1 as B. thuringiensis and E-1, E-2, and E-3 as B. licheniformis, respectively. In addition, presence of B. thuringiensis was also confirmed by toxin crystal protein staining. In conclusion, the species-specific primers could be used as a rapid and accurate identification tool to discriminate closely related Bacillus species such as B. subtilis, B. licheniformis, and B. thuringiensis.

Simultaneous determination of synthetic food additives in kimchi by liquid chromatography-electrospray tandem mass spectrometry.

A new analytical method was developed for the simultaneous determination of seven food additives (Ponceau 4R, Allura Red AC, Amaranth, 4-hydroxymethyl benzoic acid, ethyl-4-hydroxybenzoate, butyl-4-hydroxybenzoate, and saccharin sodium) in kimchi using high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. The linearity, sensitivity, selectivity, precision, and accuracy of the method were validated. The limit of detection was 0.00004-0.24 µg/mL, and the limit of quantification was 0.00012-0.8 µg/mL. Recoveries ranged from 85.65 to 120.82%. The method was successful and may help to ensure food safety.

An effective methodology for simultaneous quantification of thiophanate-methyl, and its metabolite carbendazim in pear, using LC-MS/MS.

Herein we have developed an optimized analytical method for the simultaneous quantification of a fungicide, thiophanate-methyl, and its metabolite, carbendazim, in pear cultivated under open-field conditions using liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Due to the problem of partitioning associated with using acetonitrile and salts, methanol was used for sample extraction; the extract was then filtered using a vacuum filter, and cleaned-up using C18 QuEChERS bulk sorbent following dispersive solid-phase extraction (d-SPE) procedure. Since a common problem, "matrix effect", associated with the matrix was observed in LC-MS/MS, calibration curves for both thiophanate-methyl and carbendazim were constructed in the matrix using seven different concentration levels. Excellent linearity was observed, with determinant coefficient (R2) ≥ 0.9990. The limits of quantification (LOQs) were ≤0.02 mg/kg, satisfactory in terms of the maximum residue limits. Methods were validated at two fortification concentrations (10 × LOQ and 50 × LOQ); the experiments were repeated three times for each level and the average recoveries were 75.00-84.92%, with the coefficient of variation (CV) being ≤5.78%. The developed analytical method was applied to pear samples previously sprayed with commercial thiophanate-methyl formulation four times on different days during pre-harvest treatment. The parent compound was converted to its metabolites and the total residues degraded continuously until harvest. The data obtained in this study could help set safety guidelines for thiophanate-methyl in pear.

Simple extraction method using syringe filter for detection of ethephon in tomatoes by negative-ion mode liquid chromatography with tandem mass spectrometry.

In this study, a simple, rapid, and sensitive method was developed for the extraction of ethephon from homogenized tomatoes that does not require a cleanup procedure. In a syringe filter, three distinct layers - aqueous, acetonitrile, and n-hexane - are clearly separated after storage at -80 °C for 5-10 min. A Dionex IonPac column was used to separate the analyte before detection using negative-ion mode liquid chromatography with tandem mass spectrometry (LC/MS/MS). The matrix effect of the tested analyte was negligibly small and the matched calibration showed a good linearity over a concentration range of 0.01-1.0 mg/kg with a correlation coefficient (R(2) ) of 0.9998. The recovery at three fortification levels (0.1, 0.5 and 1.0 mg/kg) was between 82.9 and 108.6% with relative standard deviations (RSDs) <5.0%. The limit of quantification (0.03 mg/kg) was lower than the maximum residue limit (3 mg/kg) set by the Ministry of Food and Drug Safety, Republic of Korea. From a field trial, the method developed herein was applied to calculate the decline pattern and predict the pre-harvest residue limits of ethephon in tomatoes. In conclusion, the proposed sample preparation is feasible for the detection of hydrophilic analytes in tomatoes.

Simultaneous multi-determination and transfer of eight pesticide residues from green tea leaves to infusion using gas chromatography.

A method for determining eight pesticide (cyhalothrin, flufenoxuron, fenitrothion, EPN, bifenthrin, difenoconazole, triflumizole, and azoxystrobin) residues in made green tea as well as a tea infusion (under various brewing water temperatures; 60, 80, and 100°C) using gas chromatography (GC) micro-electron capture detector (µECD) was developed and validated. The extraction method adopted the relatively commonly used approach of solid sample hydration, with the green tea hydrated before being extracted through salting out with acetonitrile followed by a cleanup procedure. The analytes were confirmed using GC-coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole. The linearity of the calibration curves yielded determination coefficients (R(2)) >0.995. Recoveries were carried out using blank samples spiked with all analytes at two levels. The results demonstrated that all pesticides were recovered within the range of 77-116% with a relative standard deviation (RSD) ⩽14%. The quantification limits of 0.015-0.03 mg/kg were lower than the maximum residue limits (MRLs) set by the Korea Food and Drug Administration (KFDA) for all analytes (0.05-10mg/kg). The infusion study indicated that cyhalothrin, flufenoxuron, and bifenthrin did not infuse into the tea brew from the made tea. Increases in brewing time resulted in increased transfer of azoxystrobin, fenitrothion, and difenoconazole from the made tea to the brew; however, this was not the case with triflumizole or EPN. We conclude that transfer of pesticides appeared to be dependent on their water solubilities and drinking a cup of tea is recommended to be at a water temperature of 60°C.

Development of a simple extraction and oxidation procedure for the residue analysis of imidacloprid and its metabolites in lettuce using gas chromatography.

Simple extraction and optimised oxidation procedures were developed for the determination of the total residues of imidacloprid and its metabolites (containing the 6-chloropicolyl moiety) in lettuce using a gas chromatography-micro electron capture detector (GC-µECD). Samples were extracted with acetonitrile, and the extract was then evaporated. The remaining residues were dissolved in water and oxidised with potassium permanganate to yield 6-chloronicotinic acid (6-CAN). The acid residues were further dissolved in n-hexane:acetone (8:2, v/v) and then silylated with MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide) to 6-chloronicotinic acid trimethylsilyl ester. Calibration curves were linear over the concentration ranges (0.025-5 µg mL(-1)) with a determination coefficient (r(2)) of 0.991. The limits of detection and quantification were 0.015 and 0.05 mg kg(-1), respectively. Recoveries at two fortification levels ranged between 72.8% and 108.3% with relative standard deviation (RSD) lower than 8%. The method was effective, and sensitive enough to determine the total residues of imidacloprid and its metabolites in field-incurred lettuce samples. The identity of the analyte was confirmed using gas chromatography-tandem mass spectrometry (GC-MS/MS).

A matrix sensitive gas chromatography method for the analysis of pymetrozine in red pepper: application to dissipation pattern and PHRL.

A gas chromatography (GC) method for the analysis of pymetrozine was developed after utilizing matrix enhancement effect of pymetrozine to nitrogen phosphorus detector (NPD). Samples were extracted with acetonitrile and purified through primary secondary amine (PSA) and C18 dispersive sorbent. Matrix-matched calibration curve prepared after spiking standard pymetrozine across the studied range of concentrations (0.003-1.0mg/L) into blank red pepper extract was excellent with a determination coefficients (R(2))=1. Recovery studies were carried out at three concentration levels (0.04, 0.4, and 2.0mg/kg, n=3) and the rates were ranged between 77.2% and 109.1%, with relative standard deviations ranged from 1.3% to 16.4%. The developed method was applied to field samples to characterize the dissipation pattern, half life, and pre-harvest residue limits (PHRL). The dissipation rates of the analyte were ascribed to first-order kinetics with half-life of 2.7 and 2.5days for recommended and double the recommended doses. From the PHRL curve, we could predict that if the residue level of pymetrozine is below the 1.23mg/kg at 10days or 0.71mg/kg at 7days before harvest, then the residues will be below the maximum residue limits (MRL=0.2mg/kg) established by the Korea Food and Drug Administration (KFDA).

Simple multiresidue extraction method for the determination of fungicides and plant growth regulator in bean sprouts using low temperature partitioning and tandem mass spectrometry.

A simple multiresidue analytical method is developed for the simultaneous determination of carbendazim (CB), thiabendazole (TB), and 6-benzyl aminopurine (6-BA) in bean sprouts. The samples were extracted with acetonitrile followed by partitioning at -80°C for 5-10 min. A YMC C(8) column was used to separate the analytes before being qualitatively and quantitatively determined by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) in positive ion mode using multiple reaction monitoring (MRM). The matrix-matched calibration curves showed good linearity in the range 0.01-1.0 mg/kg with correlation coefficients in excess of 0.998. The mean recoveries were in the range of 80.4-96.3% at 0.1 and 0.5 spiked levels, and the relative standard deviations (RSDs) were in the range of 0.5-7.6%. The limits of quantifications (LOQ) were in the range of 0.005-0.01 mg/kg. The method was successfully applied to 90 samples (among which 45 were organic) collected from a commercial bean sprout production house throughout the city. Except for 6-BA, the rest of the analytes had values lower than their LOQs. In sum, carbendazim, thiabendazole, and 6-BA were extracted in a single step, and no steps for clean-up or concentration of the extracts were needed. The current method can be used for sensitive and accurate determination and confirmation of residues in bean sprout samples.

Analysis of kresoxim-methyl and its thermolabile metabolites in Korean plum: An application of pepper leaf matrix as a protectant for GC amenable metabolites.

A new method was developed for kresoxim-methyl (parent compound) and its two thermolabile metabolites, BF 490-2 and BF 490-9, in Korean plum, introducing pepper leaf matrix as a natural analyte protectant for GC-amenable metabolites using a GC-electron capture detector. Samples were extracted with a simple and rapid method using a mixture of ethyl acetate-n-hexane (1:1) and salts, and purified via SPE. Due to the elution gap between parent compound and metabolites in the SPE cartridge and matrix interference, kresoxim-methyl was isolated separately from its metabolites. An optimized amount of pepper leaf matrix (0.25 g/mL) was added to the metabolites prior to each injection. Calibration curves were linear over the concentration ranges with coefficient of determination (r(2)) ≥ 0.999. The method was validated in triplicate at two fortification levels, giving recoveries ranging between 74.3 and 101.4%, and RSDs less than 5%. The LOD and LOQ were 0.015 and 0.05 mg/kg, respectively. The method was successfully applied to real samples where kresoxim-methyl residues were detected in field-incurred plum samples. Residues were confirmed using GC-MS.

Development of QuEChERS-based extraction and liquid chromatography-tandem mass spectrometry method for quantifying flumethasone residues in beef muscle.

A rapid, specific, and sensitive method based on liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM) was developed and validated to quantify flumethasone residues in beef muscle. Methods were compared between the original as well as the EN quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction. Good linearity was achieved at concentration levels of 5-30 µg/kg. Estimated recovery rates at spiking levels of 5 and 10 µg/kg ranged from 72.1 to 84.6%, with relative standard deviations (RSDs)<7%. The results of the inter-day study, which was performed by fortifying beef muscle samples (n=18) on 3 separate days, showed an accuracy of 93.4-94.4%. The precision (expressed as relative standard deviation values) for the inter-day variation at two levels of fortification (10 and 20 µg/kg) was 1.9-5.2%. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.7 and 5 µg/kg, at signal-to-noise ratios (S/Ns) of 3 and 10, respectively. The method was successfully applied to analyze real samples obtained from large markets throughout the Korean Peninsula. The method proved to be sensitive and reliable and, thus, rendered an appropriate means for residue analysis studies.

Determination of spinetoram and its metabolites in amaranth and parsley using QuEChERS-based extraction and liquid chromatography-tandem mass spectrometry.

In this study, a simultaneous method was developed for the determination of spinetoram (XDE-175-J and XDE-175-L) and its demethyl metabolites (N-demethyl-175-J and N-demethyl-175-L) and formyl metabolites (N-formyl-175-J and N-formyl-175-L) in the minor crops; amaranth and parsley. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction. Afterwards, the analytes were quantified and confirmed via liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM). Calibration curves were linear over the calibration ranges for all the analytes tested with r(2)>0.993. Limits of detection and quantitation were 0.01 and 0.03 mg/kg for all the tested analytes in amaranth and parsley, respectively. Recovery values, at spiking levels 0.05 and 0.25 mg/kg, ranged from 71.0% to 115.2% with relative standard deviations <15%, except for N-formyl-175-J in both amaranth and parsley. This method was applied to field-incurred samples and was shown to provide an adequate sensitivity and performance for the simultaneous determination of spinetoram and metabolites. To the best of our knowledge, this is the first time spinetoram and its metabolites were quantified using LC-MS/MS in minor crops.

Development of a new QuEChERS method based on dry ice for the determination of 168 pesticides in paprika using tandem mass spectrometry.

This study describes a new QuEChERS method referred to as the dry ice-partitioning QuEChERS method. This current method can be differentiated from the other QuEChERS methods in the sense that it uses dry ice rather than salts or buffers to extract and partition pesticides in the first extraction step. The dry ice-partitioning QuEChERS method consists of extraction method A (for detection of the acetonitrile layer) and extraction method B (for detection of both acetonitrile and aqueous layers). The extraction efficiency was then compared with the citrate-buffering QuEChERS method by means of recovery. Recovery values of the tested 168 pesticides were above 76%, with relative standard deviations of less than 20%. Certain problematic pesticides, including benfuracarb, carbosulfan, dichlofluanid, probenazole, pymetrozine, tolylfluanid, TFNA, and TFNG evidenced acceptable recoveries via the dry ice-partitioning QuEChERS method compared to the less than 70% recoveries of the citrate-buffering QuEChERS method examined herein. The matrix effect of paprika on the method developed herein was not significant, and matrix-matched calibration was performed well, with an r(2)≥0.99. The dry ice-partitioning QuEChERS method is capable of detecting the aqueous layer as well as the acetonitrile layer; this interesting feature makes it worth in application as an alternative QuEChERS method for the multiresidue analysis of pesticides within a broad polarity range in various matrices.

Determination of spinetoram in leafy vegetable crops using liquid chromatography and confirmation via tandem mass spectrometry.

Spinetoram is a second-generation member of the spinosyn class, all members of which have been shown to be effective in insect control via a novel mode of action. Spinetoram is a mixture of 3'-O-ethyl-5, 6-dihydro spinosyn J (XDE-175-J) and 3'-O-ethyl spinosyn L (XDE-175-L). In order to establish a determination method for the analysis of spinetoram residues in crops, commercial product (5% suspension concentrate spinetoram) was applied to two leafy vegetables (Garland chrysanthemum and Aster scaber) on different spraying schedules. The analytical method used herein was based on a reversed-phase separation on a C(18) column, isocratic elution and UV detection. The analytes were confirmed via tandem mass spectrometry. The method was linear over a concentration range of 0.05-10 ppm with a correlation coefficient in excess of 0.9998. The recoveries of XDE-175-J and XDE-175-L from the two vegetables ranged between 86.04 and 98.87% at spiking levels of 1 and 5 ppm. The relative standard deviations were no more than 7% for all recovery tests conducted herein. The calculated limits of detection and quantification were 0.01 and 0.03 ppm for both XDE-175-J and XDE-175-L. The levels of residues in two vegetables treated under a fixed schedule in the greenhouse were 6.21-0.55 ppm (maximum residue limit (MRL) = 7 ppm). In sum, this method constitutes an easy and reliable technique for the determination of spinetoram in leafy vegetables.

Residual pattern of fenhexamid on pepper fruits grown under greenhouse conditions using HPLC and confirmation via tandem mass spectrometry.

Fenhexamid (25%, SC) was sprayed on pepper fruits grown under greenhouse conditions at the recommended dose rate of 20g/20L water. Fruit samples were collected randomly at 0 (2h after application), 1, 2, 4, 6, 8, 11, and 14days post-application. The samples were extracted with acetonitrile, partitioned with water, passed through a cleanup procedure, and analysed via HPLC. Residues were confirmed via LC-tandem mass spectrometry (LC-MS/MS) in positive-ion electrospray ionisation (ESI+) mode. The rate of disappearance of fenhexamid on pepper fruits was described as first-order kinetics (r(2)=0.992) with a half-life of 4.7-day. Based on the pattern of decline of the fungicide residues in relation to the estimated maximum residue limits (MRL=5mg/kg), a safety pre-harvest interval of 1day is suggested for peppers at the recommended dosage.

Determination of acetamiprid residues in zucchini grown under greenhouse conditions: application to behavioral dynamics.

A simple analytical method was developed for the determination of acetamiprid residues in zucchini and zucchini leaves grown under greenhouse conditions using liquid chromatography. Residues were confirmed via tandem mass spectrometry in positive-ion electrospray ionization mode. The calibration curves were linear with correlation coefficients in excess of 0.999. The limits of detection and limits of quantification were 0.01 and 0.03 µg/g and 0.02 and 0.06 µg/g, for the zucchini and zucchini leaves, respectively. For validation purposes, recoveries studies were carried out at low and high levels, yielding recovery rates ranged from 85.7 to 92.2% in zucchini and from 90.5 to 101.9% in zucchini leaves, with a relative standard deviation of <12%. The results demonstrated that the pattern of acetamiprid dissipation followed pseudo first-order kinetics with a half-life of 1.9 and 2.5 days, respectively. The residues in zucchini leaves were substantially higher than in the zucchini plant itself. No residues were detected at 7 days post-application. The results of this study suggest that acetamiprid is acceptable for application in/on zucchini under the recommended dosage conditions.

Effectiveness of pressurized liquid extraction and solvent extraction for the simultaneous quantification of 14 pesticide residues in green tea using GC.

A simultaneous multiresidue method to determine 14 different pesticides, namely: flufenoxuron, fenitrothion, chlorfluazuron, chlorpyrifos, hexythiazox, methidathion, chlorfenapyr, tebuconazole, EPN, bifenthrin, cyhalothrin, spirodiclofen, difenoconazole, and azoxystrobin in green tea using pressurized liquid extraction (PLE) is described and compared with that of liquid-liquid extraction (LLE). For PLE, the extraction conditions were not optimized. Rather they were selected based upon previous successful investigations published by our laboratory. Analysis was performed by GC with electron capture detector (GC-ECD), and the pesticide identity of the positive samples was confirmed by GC-MS in a selected ion-monitoring (SIM) mode. Calibration curves showed an excellent linearity for concentrations ranging from 0.006 to 36.049 ppm, with r(2) >0.995. Green tea spiked at each of the two fortification levels, yielded average recoveries in the range of 87-112% and 71-109% for PLE and LLE, respectively. Precision values, expressed as RSDs, were below 6% at various spiking levels. With respect to the existing procedures, both methods gave LOQs that were lower than the maximum residue limits (MRLs) established by the Korea Food and Drug Administration (KFDA). Both methods have been successfully applied to the analysis of real samples, and bifenthrin was the only pesticide residue quantified in incurred green tea samples, with concentrations ranging from 0.093 ppm (LLE) to 0.1 ppm (PLE). These concentration levels were relatively low compared to KFDA-MRL (0.3 ppm). According to the validation data and performance characteristics, both methods are appropriate for multiresidue analysis of pesticide residues in green tea. PLE methodology showed superiority in recoveries of some pesticides, acceptable accuracy and precision while minimizing environmental concerns, time, and labor, and can be applied in routine analytical laboratories.

Comparison of different extraction methods for the simultaneous determination of pesticide residues in kiwi fruit using gas chromatography-mass spectrometry.

The methods of simultaneous extraction of iprodione, chlorpyrifos-methyl, EPN and endosulfan (with its metabolites) from kiwi fruit using accelerated solvent extraction (ASE), supercritical fluid extraction (SFE), and liquid-liquid extraction (LLE) were tested and compared in terms of their of limits of detection and quantification, as well as the highest pesticide recoveries with the lowest residues in the final extracts. The analysis was performed using gas chromatography-mass spectrometry in the selected ion monitoring mode. The proposed methods featured good sensitivity, pesticide quantification limits were low enough, and the precision (expressed as relative standard deviations) ranged from 0.56 to 7.17%. The recoveries obtained from ASE, SFE and LLE were 77.5-120, 71.9-109.1 and 75.6-127.1%, respectively. The proposed methods were successfully applied for the monitoring of the selected pesticide residues in kiwi fruit samples collected from Jollanamdo area, Republic of Korea. Iprodione was detected at a level lower than the maximum residue limit (MRL) established by the Korea Food and Drug Administration (5 ppm), while EPN was detected at a level higher than the Korea Food and Drug Administration MRL (0.1 ppm) in the real samples. The proposed sample preparations led to a higher preconcentration of the pesticide fraction, and allowed the sensitive and selective determination of pesticides with varied physicochemical properties in kiwi fruit.

Development of extraction procedures for the determination of imidacloprid: application to residue analysis and dynamics of two formulations in Chinese cabbage.

This study was undertaken to investigate whether an additional column clean-up procedure can affect the accuracy of an analytical method developed for the determination of imidacloprid residues in Chinese cabbage. Thereafter, the residue levels and the degradation rates of imidacloprid were investigated in experimental Chinese cabbage plots after treatment with two different commercial formulations: emulsifiable concentrate (EC) and wettable powder (WP). The analyte was determined using high-performance liquid chromatography-ultraviolet detection (HPLC-UVD) and confirmed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) in the select ion-monitoring mode. The mean recoveries ranged from 75.34 to 98.00% and 96.95 to 100.97%, with relative standard deviations of 0.86-4.14 and 1.22-3.52%, in samples treated with and without additional column clean-up procedures, respectively. The minimum detectable amount of imidacloprid was 4 ng, while the limits of detection and quantitation were 0.2 and 0.5 ppm, respectively. The degradation of pesticide was monitored throughout a period of 13 days under greenhouse conditions. Although the behaviors of the EC and WP formulations appear to be similar, the absolute residue levels obtained with EC and WP treatments differed slightly. When imidacloprid formulations were applied (as foliar treatments) according to the recommended rate, the final residues (13 days post-treatment) in Chinese cabbage were much lower than the maximum residue limit (MRL = 3.5 ppm) established by the Korean Food and Drug Administration. Taken together, our study suggests that the analysis of imidacloprid can be performed without an additional column clean-up procedure, and the decline curve and the residue levels in Chinese cabbage could change if the same active ingredient is used in different formulations.