Hyeyoung Kwon

Analysis of pesticide residues in strawberries and soils by GC-MS/MS, LC-MS/MS and two-dimensional GC– time-of-flight MS comparing organic and integrated pest management farming

This study analysed 22 strawberry and soil samples after their collection over the course of 2 years to compare the residue profiles from organic farming with integrated pest management practices in Portugal. For sample preparation, we used the citrate-buffered version of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. We applied three different methods for analysis: (1) 27 pesticides were targeted using LC-MS/MS; (2) 143 were targeted using low pressure GC-tandem mass spectrometry (LP-GC-MS/MS); and (3) more than 600 pesticides were screened in a targeted and untargeted approach using comprehensive, two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOF-MS). Comparison was made of the analyses using the different methods for the shared samples. The results were similar, thereby providing satisfactory confirmation of both similarly positive and negative findings. No pesticides were found in the organic-farmed samples. In samples from integrated pest management practices, nine pesticides were determined and confirmed to be present, ranging from 2 µg kg−1 for fluazifop-p-butyl to 50 µg kg−1 for fenpropathrin. Concentrations of residues in strawberries were less than European maximum residue limits. Graphical Abstract

Analysis of Pesticide residues in brown rice using modified QuEChERS multiresidue method combined with electrospray ionization-liquid chromatography-tandem mass spectrometric detection

An efficient and modified Quick Easy Cheap Effective Rugged and Safe (QuEChERS) method combined with liquid chromatography-electrospray ionization with tandem mass spectrometric detection were evaluated for the analysis of residues of 72 pesticides in brown rice including acidic sulfonylurea herbicides. For extraction of pesticides and clean-up of the extract, 1% formic acid in acetonitrile and dispersive solid phase extraction were used, respectively. Two fortified spikes at 50 and 200 μg L−1 levels were performed for recovery test. Mean recoveries of majority of pesticides at two spike levels ranged from 90 to 110% with standard error (Coefficient of Variation) less than 10%. The limits of detection and quantification ranged from 0.24 to 19.92 μg L−1 and 0.79 to 65.74 μg L−1, respectively. Good linearity of calibration curves were achieved with R2>0.9943 within the observed concentration range (from 20 to 400 μg L−1). The modified method also provided satisfactory results for sulfonylurea herbicides, which could not be determined properly with previously reported methods. This method was applied to determine residues of target pesticides in real samples. A total of 22 pesticides in 31 out of 40 tested samples were observed. The highest concentration was observed for tricyclazole at 1.17 mg L−1. This pesticide found in two brown rice samples exceeded its MRL regulated for rice in Republic of Korea. Except this pesticide, concentrations of all observed pesticides were lower than their MRLs. The results reveal that the method is applicable for routine analysis of residues of target pesticides in brown rice.

Effect of household processing on pesticide residues in field-sprayed tomatoes

Tomatoes sprayed with chlorothalonil, oxadixyl, and thiophanate-methyl in a greenhouse were cooked to juice and puree using washing, blanching, peeling, and boiling. Washing reduced amounts of chlorothalonil, oxadixyl, and thiophanate-methyl pesticide residues by 92, 52, and 84%, respectively. A concentration of 3.66% chlorothalonil remained in peeled tomatoes, 0.32% in juice, with no detection in puree. Oxadixyl remained at a concentration of 40% in peeled tomatoes, 54% in juice, and 77% in puree, and the remaining concentration of thiophanate-methyl was 6.2% in peeled tomatoes, 8.7% in juice, and 16.2% in puree. Non-systemic pesticide residues on tomato surfaces could be largely removed through washing and peeling. Reductions in levels of systemic pesticides in tomato pulp during boiling were dependent on the physico-chemical characteristics of pesticides.

Aqueous Degradation of Imidacloprid and Fenothiocarb using Contact Glow Discharge Electrolysis: Degradation Behavior and Kinetics

Degradation of the pesticides fenothiocarb and imidacloprid in water using contact glow discharge electrolysis (CGDE) achieved rates of 57.8 and 43.2% respectively. Degradation was enhanced using citric or hydrochloric acid to lower the pH to 3.0. Both acids enhanced both the degradation rate and the amount. Fenothiocarb degradation was 77.14% at pH 3 with citric acid, and 100% with HCl. Degradation of imidacloprid at pH 3 was 70.18% with citric acid and 93.02% with HCl. Acidic conditions favor either production of ·OH radicals or enhancement of the degradation of organic compounds by ·OH. Both the degradation rates and amounts for fenothiocarb and imidacloprid were reduced in the presence of methanol due to competition between pesticides and MeOH for ·OH. Degradation of pesticides was not completely inhibited by MeOH. Degradation of both fenothiocarb and imidacloprid using CGDE obeys a first-order rate law with high regression coefficient values (R2>0.99).

Development of Analytical Method for Picoxystrobin in Agricultural Commodities Using GC/ECD and GC/MS

BACKGROUND: This study was conducted to develop analytical method for picoxystrobin in agricultural commodities using GC/ECD and GC/MS. METHODS AND RESULTS: Each steps of analytical method were optimized for determining picoxystrobin residues in various agricultural commodities. The developed methods include acetone extraction, n-hexane/saline water partition and florisil column chromatography for analysis of all samples (apple, potato, green pepper, hulled rice and soybean), and in addition to these steps, solid phase extraction (SPE) was used for analysis of green pepper and n-hexane/acetonitrile partition was used for analysis of hulled rice and soybean. The instrumental conditions were tested for quantitation in GC/ECD and for confirmation in GC/MS. Recovery was in the range of 86~109% with RSD 10.2% and the quantitation limits (LOQ) of method were 0.025 mg/kg in all agricultural commodities. CONCLUSION: The result showed that the developed method can be used to determine picoxystrobin residue in agricultural commodities.

Compensation for matrix effects in GC analysis of pesticides by using cucumber extract

Matrix effects (MEs) can adversely affect quantification in pesticide residue analysis using GC. Analyte protectants (APs) can effectively interact with and mask active sites in the GC system, and are added individually or in combination to sample extracts and calibration solutions to minimize errors related to MEs. Unfortunately, APs cannot sufficiently compensate for MEs in all cases. Plant extracts, containing a broad range of natural compounds with AP properties, can also be used for this purpose. In this study, the applicability of cucumber extract as a natural AP mixture was investigated both alone and in combination with traditional APs. Extracts of two selected difficult matrices (onion and garlic) were prepared according to the citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. ME values of 40 representative GC-amenable pesticides were compared when calibrating against standards in pure solvent and in cucumber extract, with and without the addition of APs. Using a GC system with a contaminated inlet liner, the use of a cucumber-based calibration solution decreased MEs remarkably. The combination of APs with cucumber raw extract further decreased MEs, resulting in more than 85% of the tested pesticides showing ≤ 10% ME in onion and ≤ 20% ME in garlic. These results demonstrate that the preparation of calibration standards based on cucumber extracts (with or without the addition of APs) is a very useful and practical approach to compensate for MEs in pesticide residue analysis using QuEChERS and GC-MS/MS. The use of various internal standards is furthermore critically discussed.

Uptake and Translocation of the Soil Residual Pesticides into the Vegetable Crop

토양 중 잔류농약의 작물에 대한 흡수이행 평가 및 잔류허용기준 초과 가능성을 구명하기 위하여 지난 10여 년간 농경지 토양 중 잔류농약 모니터링 결과 검출빈도와 검출농도가 높은 살충제 endosulfan, chlorfenapyr, chlorpyrifos, ethoprofos와 살균제 isoprothiolane, procymidone, fthalide 등 7종을 선발하고, 이들 농약을 토양에 혼화 처리 후 포트 및 포장에서 토양 중 잔류농도의 변화를 조사하였다. 또한 시험약제가 처리된 토양에 엽채류(배추, 상추, 시금치), 근채류(무, 감자, 당근) 및 과채류(오이, 고추, 가지, 토마토) 채소 등을 재배하여 수확기 토양중 잔류농약의 작물체로의 흡수이행 정도를 조사하였다. 포트에서 양토중 엽채류의 잔류농약 흡수비는 ethoprophos > chlorpyrifos ≥ endosulfan > fthalide 순으로 낮았으며, 사양토에서는 ethoprophos > endosulfan ≥ chlorpyrifos > fthalide 순이었다. 작물별 토양 중 잔류농약 흡수는 대체로 배추 >시금치 >상추 순으로 적었다. 노지 근채류 채소 재배지 토양중 잔류농약의 반감기는 양토에서 chlorfenapyr (13일) 고추 >가지 >토마토 순으로 높았다. 또한, 과채류 채소 재배지 토양에 시험약제들을 20 mg/kg 수준까지 처리하였을 때 수확기 과채류 중 농약은 잔류허용기준 (MRL)의 1/5~1/10 수준이었으나 endosulfan은 과채류에도 흡수·이행이 잘되어 재배조건에 따라 잔류허용기준을 초과할 가능성이 있을 것으로 판단되므로 주의 할 필요가 있다.

Analytical Method for Fenoxasulfone in Agricultural Commodities using High Performance Liquid Chromatography

본 연구에서는 농산물중 fenoxasulfone의 잔류량을 분석하기 위한 분석법을 개발하였다. 농산물에 범용적으로 사용될 분석법을 개발하기 위하여 5가지 대표 농산물(사과, 감자, 고추, 대추, 현미)에 대하여 0.025, 0.25, 1.25 μg/g의 농도 수준으로 회수율 시험을 실시하였다. 시료는 아세톤으로 추출하고 액액분배과정에서 용매별 분배효율을 비교하여 디클로로메탄을 선정하였다. 현미와 대두의 비극성 불순물을 제거하기위해 n-hexane으로 포화된 acetonitrile과 acetonitrile로 포화된 n-hexane이 사용되었다. 추가 정제를 위해 n-hexane/acetone의 조합으로 aminopropyl SPE cartridge 조건을 확립하였다. 기기분석은 HPLC/UVD 240 nm 검출조건에서 acetonitrile과 water을 이동상 조건으로 확립하였다. 개발된 분석법의 검증 결과 회수율은 71.2-89.8%의 범위였으며 상대표준편차(RSD)는 7.2% 이하였다. Fenoxasulfone의 정량한계(LOQ)는 0.025 μg/g이었고 정량곡선의 결정계수(R2)는 1.0000로 양호하였다. 따라서 개발된 분석법은 농산물에서 fenoxasulfone의 잔류량을 분석하기 위한 분석법으로 사용이 가능하리라 판단되었다.본 연구에서는 농산물중 fenoxasulfone의 잔류량을 분석하기 위한 분석법을 개발하였다. 농산물에 범용적으로 사용될 분석법을 개발하기 위하여 5가지 대표 농산물(사과, 감자, 고추, 대추, 현미)에 대하여 0.025, 0.25, 1.25 μg/g의 농도 수준으로 회수율 시험을 실시하였다. 시료는 아세톤으로 추출하고 액액분배과정에서 용매별 분배효율을 비교하여 디클로로메탄을 선정하였다. 현미와 대두의 비극성 불순물을 제거하기위해 n-hexane으로 포화된 acetonitrile과 acetonitrile로 포화된 n-hexane이 사용되었다. 추가 정제를 위해 n-hexane/acetone의 조합으로 aminopropyl SPE cartridge 조건을 확립하였다. 기기분석은 HPLC/UVD 240 nm 검출조건에서 acetonitrile과 water을 이동상 조건으로 확립하였다. 개발된 분석법의 검증 결과 회수율은 71.2-89.8%의 범위였으며 상대표준편차(RSD)는 7.2% 이하였다. Fenoxasulfone의 정량한계(LOQ)는 0.025 μg/g이었고 정량곡선의 결정계수(R2)는 1.0000로 양호하였다. 따라서 개발된 분석법은 농산물에서 fenoxasulfone의 잔류량을 분석하기 위한 분석법으로 사용이 가능하리라 판단되었다.