Seongsoo Park

Multiresidue Analysis of Pesticides in Agricultural Products by a Liquid Chromatography/Tandem Mass Spectrometry Based Method

A sensitive and specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the determination of 56 residual pesticides from commercial crops. For a validation of the method, the recoveries, linearities, limits of detection (LOD), and limits of quantitation (LOQ) of the 56 pesticides were investigated. The linearities, LOD, and mean recoveries of the pesticides ranged 0.9686–0.9999, 0.00–11.54 μg/kg, and 65–82%, respectively. This method was evaluated by its application to monitor 345 agricultural products collected from 9 provinces in Korea 2011. Fifteen pesticides were detected from 39 samples and 2 or more residual pesticides were found in 7 samples. However, none of the compounds were observed above the corresponding maximum residue level. The results reflect that the detected pesticide residues were in a safe range and that residual pesticides in the agricultural products in Korea were properly controlled.

Validation of a Rapid Quantitative Method for the Residues of Nitrofuran Metabolites in Loach by Accelerated Solvent Extraction and HPLC Triple Quadrupole Mass Spectrometry

A rapid method using HPLC-MS/MS has been developed for quantitative determination of the metabolites of nitrofurans, namely 3-amino-2-oxazolidone (AOZ), 5-morpholinomethyl-3-amino-2-oxazolidinone (AMOZ), 1-ammino-hydantoin (AHD) and semicarbazide (SEM) in loach. The extraction procedure was founded on simultaneous acidic hydrolysis and derivatization using 2-nitrobenzaldehyde (2-NBA) for 1 hour at 50oC, followed by purification with liquid-liquid extraction. Recovery was evaluated by spiking standards into blank samples at three levels (0.5, 1.0 and 2.0 μg/kg), and the mean recovery was 75.1-108.1%. Precision values expressed as the relative standard deviation (%RSD) were ≤ 8.7% and ≤ 8.5% for intra-day and inter-day precision, respectively. Linearity was studied in the range of 0.2-20 μg/Kg for NBAOZ, 0.8-20 μg/Kg for NBAMOZ, 0.2-20 μg/Kg for NBAHD, and 0.120 μg/Kg for NBSEM, and the obtained coefficient correlations (r) were ≥ 0.99 for all compounds. Limits of detection (LODs) for the derivatized nitrofuran metabolites were established at 0.06 μg/Kg for NBAOZ, 0.24 μg/Kg for NBAMOZ, 0.06 μg/Kg for NBAHD, and 0.03 μg/Kg for NBSEM. Limits of quantification (LOQs) were established at 0.2 μg/Kg for NBAOZ, 0.8 μg/Kg for NBAMOZ, 0.2 μg/Kg for NBAHD, and 0.1 μg/Kg for NBSEM. This simplified rapid method for reducing the derivatization and hydrolysis times can be applied to the determination of nitrofuran residues in loach.

Distribution and exposure assessment of indicator PCBs in Food

Seven indicator PCBs (IUPAC nos 28, 52, 101, 118, 138, 153, 180 congeners) concentrations were measured in food samples including cereal (polished rice), meats, eggs, milk and dairy products, and fisheries and products as representation for the general Korean populations during 2006-2007, and was analyzed using isotopic dilution method. Fishes had the highest average level as 39.8 ng/g, 1.4 ng/g for milk and dairy products, and 0.9 ng/g for meats. The hairtail out of fishes was contaminated at the level of 15.4 ng/g, 5.4 ng/g for pacific mackerel and spanish mackerel, and 4.5 ng/g for yellow croaker. The ratio for indicator PCBs in overall food was contributed as follows; 35.8% for PCB-153, 16.2% for PCB-138, 16.1% for PCB-101, 13.4% for PCB-118, 8.8% for PCB-180, 6.9% for PCB-52, and 2.9% for PCB-28. The hexa-CBs including PCB-153 and 138 were more predominated, and the next was penta-CBs including PCB-101 and 118 in food. For estimated daily intake (EDI) in average and 95 th percentile, fishes and products out of overall food were taken to represent over 50%. However, it was estimated that there was no adverse health effect for Korean.