• Korean Journal of Food Science and Technology
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• v.48 no.5
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• pp.424-429
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• 2016

Globally, obesity has been recognized as a serious health problem. Recently, slimming foods for weight loss and maintenance were found to contain anti-obesity drugs, their analogues, and prohibited ingredients. To avoid inspections by the Government, structurally modified analogs have been continuously synthesized. For rapid determination of adulterated slimming products, we simultaneously analyzed 21 illegal compounds using liquid chromatography (LC) equipped with photo diode array, and LC coupled with tandem mass spectrometry. The validation of the method was performed with regard to selectivity, linearity, limit of detection, limit of quantification, precision, and accuracy. We purchased 128 samples from the Korean market and online sources in the year 2015. In 31 samples, 3 illegal compounds were detected as follows: 9.9-135.3 mg/g of sibutramine, 0.2-17.5 mg/g of yohimbine, and 1.8 mg/g of icariin. This simultaneous detection method might prove to be a simple and rapid analysis for monitoring illegal compounds in slimming foods.

• Journal of Food Hygiene and Safety
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• v.34 no.5
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• pp.431-437
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• 2019

This study was conducted to develop a simultaneous analysis method for ferulic acid, caffeic acid, catechin and taxifolin from Health Functional Food (HFF) Pinus Pinaster bark extract. The simultaneous analytical method for ferulic acid, caffeic acid, catechin and taxifolin is carried out using UPLC-MS/MS. The method validation was performed to determine selectivity, linearity, accuracy, limit of detection (LOD), limit of quantification (LOQ) and precision for ferulic acid, caffeic acid, catechin and taxifolin. LC-MS/MS method was established using an Acquity UPLC BEH $C_{18}$ Column and was applied for these 4 compounds. Product-ion traces, at m/z $194.2{\rightarrow}133$, $180.2{\rightarrow}135$, $290.3{\rightarrow}245$, $304.3{\rightarrow}248$, were used for quantitative analysis of ferulic acid, caffeic acid, catechin and taxifolin, respectively. Excellent linearity ($r^2=0.999$) was observed for ferulic acid, caffeic acid, catechin and taxifolin in the concentration range (50-2500 mg/L). The observed recoveries of these 4 compounds were found to be between 84.9 and 104.9%, while precision was between 1.20 and 4.43% relative standard deviation (% RSD).

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.684-689
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• 2021

In this paper, we develop a cost effective and disposable voltammetric sensing platform involving screen-printed carbon electrode (SPCE) modified with the nanocomposites composed of multi-walled carbon nanotubes, polyelectrolyte, and tyrosinase for bisphenol A. This is known as an endocrine disruptor which is also related to chronic diseases such as obesity, diabetes, cardiovascular and female reproductive diseases, precocious puberty, and infertility. A negatively charged oxidized multi-walled carbon nanotubes (MWCNTs) wrapped with a positively charged polyelectrolyte, e.g., polydiallyldimethylammonium, was first wrapped with a negatively charged tyrosinae layer via electrostatic interaction and assembled onto oxygen plasma treated SPCE. The nanocomposite modified SPCE was then immersed into different concentrations of bisphenol A for a given time where the tyrosinase reacted with OH group in the bisphenol A to produce the product, 4,4'-isopropylidenebis(1,2-benzoquinone). Cyclic and differential pulse voltammetries at the potential of -0.08 V vs. Ag/AgCl was employed and peak current changes responsible to the reduction of 4,4'-isopropylidenebis(1,2-benzoquinone) were measured which linearly increased with respect to the bisphenol A concentration. In addition, the SPCE based sensor showed excellent selectivity toward an interferent agent, bisphenol S, which has a very similar structure. Finally, the sensor was applied to the analysis of bisphenol A present in an environmental sample solution prepared in our laboratory.

• Korean Journal of Environmental Agriculture
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• v.40 no.2
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• pp.108-117
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• 2021

BACKGROUND: Dichlobentiazox is a newly registered pesticide in Korea as a triazole fungicide and requires establishment of an official analysis method for the safety management. Therefore, the aim of this study was to determine the residual analysis method of dichlobentiazox for the five representative agricultural products. METHODS AND RESULTS: Three QuEChERS methods were applied to establish the extraction method, and the EN method was finally selected through the recovery test. In addition, various adsorbent agents were applied to establish the clean-up method. As a result, it was found that the recovery of the tested pesticide was reduced when using the d-SPE method with PSA and GCB, but C₁₈ showed an excellent recovery. Therefore this method was established as the final analysis method. For the analysis, LC-MS/MS was used with consideration of the selectivity and sensitivity of the target pesticide and was operated in MRM mode. The results of the recovery test using the established analysis method and inter laboratory validation showed a valid range of 70-120%, with standard deviation and coefficient of variation of less than 3.0% and 11.6%, respectively. CONCLUSION: Dichlobentiazox could be analyzed with a modified QuEChERS method, and the method determined would be widely available to ensure the safety of residual pesticides in Korea.

• Korean Journal of Environmental Agriculture
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• v.41 no.2
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• pp.82-94
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• 2022

BACKGROUND: Spiropidion and its metabolite are tetramic acid insecticide and require the establishment of an official analysis method for the safety management because they are newly registered in Korea. Therefore, this study was to determine the analysis method of residual spiropidion and its metabolite for the five representative agricultural products. METHODS AND RESULTS: Three QuEChERS methods (original, AOAC, and EN method) were applied to optimize the extraction method, and the EN method was finally selected by comparing the recovery test and matrix effect results. Various adsorbent agents were applied to establish the clean up method. As a result, the recovery of spiropidion was reduced when using the dispersive-SPE method with MgSO₄, primary secondary amine (PSA), graphitized carbon black (GCB) and octadecyl (C₁₈) in soybean. Color interference was minimized by selecting the case including GCB and C18 in addition to MgSO₄. This method was established as the final analysis method. LC-MS/MS was used for the analysis by considering the selectivity and sensitivity of the target pesticide and the analysis was performed in MRM mode. The results of the recovery test using the established analysis method and inter laboratory validation showed a valid range of 79.4-108.4%, with relative standard deviation and coefficient of variation were less than 7.2% and 14.4%, respectively. CONCLUSION(S): Spiropidion and its metabolite could be analyzed with a modified QuEChERS method, and the established method would be widely available to ensure the safety of residual insecticides in Korea.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.258-263
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• 2023

In this study, conductive polymers and the enzyme tyrosinase (Tyr) were deposited on the surface of a screen printed carbon electrode (SPCE), which can be fabricated as a disposable sensor chip, and applied to the detection of bisphenol F (BPF), an endocrine disruptor with proven links to male diseases and thyroid disorders, using electrochemical methods. On the surface of the SPCE working electrode, which was negatively charged by oxygen plasma treatment, a positively charged conductive polymer, poly(diallyldimethyl ammonium chloride) (PDDA), a negatively charged polymer compound, poly(sodium 4-styrenesulfonate) (PSS), and another layer of PDDA were layered by electrostatic attraction in the order of PDDA, PSS, and finally PDDA. Then, a layer of Tyr, which was negatively charged due to pH adjustment to 7.0, was added to create a PDDA-PSS-PDDA-Tyr sensor for BPF. When the electrode sensor is exposed to a BPF solution, which is the substrate and target analyte, 4,4'-methylenebis(cyclohexa-3,5-diene-1,2-dione) is generated by an oxidation reaction with the Tyr enzyme on the electrode surface. The reduction process of the product at 0.1 V (vs. Ag/AgCl) generating 4,4'-methylenebis(benzene-1,2-diol) was measured using cyclic and differential pulse voltammetries, resulting in a change in the peak current with respect to the concentration of BPF. In addition, we compared the detection performance of BPF using an ionic liquid electrolyte as an alternative to phosphate-buffered saline, which has been used in many previous sensing studies. Furthermore, the selectivity of bisphenol S, which acts as an interfering substance with a similar structure to BPF, was investigated. Finally, we demonstrated the practical applicability of the sensor by applying it to analyze the concentration of BPF in real samples prepared in the laboratory.

• Journal of Food Hygiene and Safety
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• v.38 no.3
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• pp.79-88
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• 2023

Trifludimoxazin is a triazinone herbicide that inhibits the synthesis of protoporphyrinogen oxidase (PPO). The lack of PPO damages the cell membranes, leading to plant cell death. An official analytical method for the safety management of trifludimoxazin is necessary because it is a newly registered herbicide in Korea. Therefore, this study aimed to develop a residual analysis method to detect trifludimoxazin in five representative agricultural products. The EN method was established as the final extraction method by comparing the recovery test and matrix effect with those of the QuEChERS method. Various sorbent agents were used to establish the clean-up method, and no differences were observed among them. MgSO₄ and PSA were selected as the final clean-up conditions. We used LC-MS/MS considering the selectivity and sensitivity of the target pesticide and analyzed the samples in the MRM mode. The recovery test results using the established analysis method and inter-laboratory validation showed a valid range of 73.5-100.7%, with a relative standard deviation and coefficient of variation less than 12.6% and 14.5%, respectively. Therefore, the presence of trifludimoxazin can be analyzed using a modified QuEChERS method, which is widely available in Korea to ensure the safety of residual insecticides.