• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.119-122
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• 2003

Quantitation methods of total petroleum hydrocarbons to determinate oil contaminated level in soil were discussed. Extraction characteristics of several pretreatment methods and practical detection limit and reappearances in gas chromatography/mass spectrometry. with each pretreatment method were investigated. The obtained results showed that the newly adopted quantitation method and mechanical shaking extraction method using methanol with extraction solvent are more practical and applicable to real sample than the conventional methods. In applying these methods to gasoline, kerosene, fuel oil which are major source of soil contamination, the practical quantitation limit and % relative standard deviation was able to determine with range of 2.5 - 10 ppm, 5 - 7 ％.

• Korean Journal of Environmental Agriculture
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• v.32 no.2
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• pp.128-135
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• 2013

BACKGROUND: This study was performed to develop a single residue analytical method for new herbicide metazosulfuron in crops. METHODS AND RESULTS: Brown rice, apple, mandarin, Kimchi cabbage and soybean were selected as representative crops, and clean-up system, partition solvent and extraction solvent were optimized. Instrumental limit of quantitation (ILOQ), linearity of calibration curve and method limit of quantitation (MLOQ) were determined based on the chromatography and whole procedures. For recovery tests, brown rice, apple, mandarin, Kimchi cabbage and soybean samples were macerated and fortified with metazosulfuron standard solution at three levels (MLOQ, 10 MLOQ and 100 MLOQ). And then those were extracted with acetonitrile, concentrated, and partitioned with ethyl acetate. Then the extracts were concentrated again and cleaned-up through $NH_2$ (aminopropyl) SPE cartridge with acetone : dichloromethane (1% acetic acid) (20 : 80, v/v) before concentration and analysis with HPLC. CONCLUSION(S): ILOQ of metazosulfuron was 2 ng (S/N${\geq}$10) and good linearity was achieved between 0.05 and 12.5 mg/Kg of metazosulfuron standard solutions, with coefficients of determination of 0.9999. MLOQ was 0.02 mg/Kg. Good recoveries from 74.1 to 116.9% with coefficients of variation (C.V.) of less than 10% were obtained, regardless of sample type, which satisfies the criteria of Korea Food and Drug Administration (KFDA). Those results were reconfirmed with LC-MS (SIM). The method established in this study is simple, economic and efficient to be applied to most of crops as an official and general method for residue analysis of metazosulfuron.

• YAKHAK HOEJI
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• v.54 no.6
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• pp.429-440
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• 2010

HS-SPME-GC/MS was studied and optimized for the determination of 17 orgarnophosphorous pesiticides (OPPs: chlorpyrifos, chlorpyrifos-methyl, demeton-s-methyl, diazinon, dimethoate, EPN, fenitrothion, fenthion, malathion, methidathion, monocrotophos, parathion, phenthoate, phosphamidon, sulfotep, terbufos, triazophos) in blood. Optimum SPME parameters were selected: choice of SPME fiber (85 ${\mu}m$ polyacrylate), pH effect (0.5 N HCl), salt effect ($Na_2SO_4$, 0.2 g; 20%), headspace incubation temperature ($80^{\circ}C$), headspace incubation time (1 min), headspace adsorption time (30 min) and GC desorption time (2 min). These parameters were optimized using HS-SPME autosampler coupled with gas chromatography-mass spectrometry (GC-MS). Method validation was carried out in terms of linearity, limit of detection (LOD), limit of quantitation (LOQ) and recovery in blood. The assay was linear over 0.5~5.0 mg/l ($r^2$=0.955~1.000). Limit of detection (LOD) and limit of quantitation (LOQ) in blood were determined 0.03~0.3 mg/l (S/N=3) and 0.1~1.1 mg/l (S/N=10), respectively. Relative recovery with 0.5, 1 and 5 mg/l (in blood) were 90.8%, 98.5% and 94.1%, respectively. This method will be applied to the determination of the orgarnophosphorous pesticides in postmortem blood. The proposed protocol can be an attractive alternative to be used in routine toxicological analysis.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.371-380
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• 2010

This study was performed to develop a precise single residue analytical method of fungicide cyprodinil in representative crops for using as general residue analytical methods which could be applied to most of crops. Apple, mandarin, Korean cabbage and green pepper were selected as representative crops, and they were macerated, extracted with acetonitrile, concentrated and partitioned with n-hexane. Then the extracts were concentrated and cleaned-up through silica gel column with ethyl acetate:n-hexane (15:85, v/v) before concentration and analysis with HPLC. LOQ (limit of quantitation) of cyprodinil was 5 ng (S/N>10) and MQL (method qnantitation limit) was 0.05 mg/kg. Recoveries were measured at three fortification levels (MQL, 10MQL and 100MQL) on crop samples and ranged from 82.0 to 108.2% and coefficients of variation were less than 10% regardless of sample type.

• Analytical Science and Technology
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• v.22 no.6
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• pp.514-518
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• 2009

Coenzyme $Q_{10}$($CoQ_{10}$), a vitamin E-like substance, represents a components of the complex antioxidant system of the human organism. $CoQ_{10}$ levels in human plasma were determined by high performance liquid chromatography (HPLC) with UV detection. It was dissociated from lipoproteins by methanol and extracted into n-hexane with liquid-liquid extraction procedure, after centrifugation, the supernatant was dried under nitrogen gas stream. The residue was dissolved in the absolute ethanol. Determination of $CoQ_{10}$ was performed on a $C_{18}$ reversed-phase analytical column with ultraviolet detection at 275 nm and the mobile phase containing 15% (v/v) ethanol in methanol at a flow rate of 1.7 mL/min. The low limit of quantitation was 0.02 mg/L (S/N=10), the linearity between the concentration and peak height is from 0.1 to 2.0 mg/L. Twenty-four randomly selected plasma samples from apparently healthy, 27 to 44 year old individuals (males and females) were analyzed for total $CoQ_{10}$. The average level in these subjects was $0.62{\pm}0.13mg/L$ with the range of 0.41-0.98 mg/L. This method has a specific and a sufficient limit of quantitation (LOQ) for analysis of $CoQ_{10}$ in human plasma in both a clinical study and research at laboratories.

• Horticultural Science & Technology
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• v.34 no.4
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• pp.644-654
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• 2016

Supervised residue trials for mandipropamid in Korean cabbage(Brassica campestris L.) were conducted to establish its pre-harvest residue limit (PHRL), a criterion to ensure the safety of the terminal pesticide residue during cabbage production. Tissues of Korean cabbage were collected at 0, 1, 3, 5, 7, and 10 days after mandipropamid application and subjected to residue analysis. The analytical method was validated by recoveries ranging from 88.2-92.2% at two levels (0.4 and $2.0mg{\cdot}kg^{-1}$), and a limit of quantitation (LOQ) of $0.04mg{\cdot}kg^{-1}$. Mandipropamid residues in Korean cabbage gradually decreased over time. The dissipation rate of the residue would be affected by intrinsic degradation of the compound along with dilution resulting from the fast growth of Korean cabbage. The decay pattern was well fitted by simple first-order kinetics. Biological half-lives of mandipropamid in Korean cabbage ranged from 3.9-4.0 days in two field conditions. Calculated by the regression curve of mandipropamid dissipation, the PHRLs of mandipropamid in Korean cabbage were recommended as 11.07-12.19 and $5.76-6.05mg{\cdot}kg^{-1}$ for 10 and 5 days prior to harvest, respectively.

• Archives of Pharmacal Research
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• v.13 no.3
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• pp.215-220
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• 1990

Two different, derivative spectrophotometric and gas-liquid chromatographic, procedures for direct quantitation of caffeine and some commonly dispensed antihistaminics in bulk forms, in their laboratory prepared mmixtures and in dosage formulations, have been investigated. The limit, sensitivity reproducibility and accuracy of each method were studied for each individual drug substance and in some usual pharmaceutical formulations.

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1515-1518
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• 2009

The objective of this study was to compare 3 extraction methods including, solid phase extraction (SPE), acetonitrile extraction, and methanol extraction, for their usefulness as extraction methods to determine capsaicinoids. The determination of capsaicinoids in the extracts was carried out on a reverse-phased high performance liquid chromatography (HPLC) using a fluorescence detector. Three extraction methods, i.e., SPE, acetonitrile extraction, and methanol extraction were compared for the quantification of capsaicinoids using raw peppers and pepper powder. The highest analytical values were observed using methanol extraction and the lowest values using SPE. Also, the analytical method validation parameters such as accuracy, precision, limit of detection, limit of quantitation, and specificity were calculated to ensure the method's validity. This method provides a fast and accurate approach for the determination of capsaicinoids in peppers.

• Mass Spectrometry Letters
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• v.10 no.4
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• pp.112-116
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• 2019

In this study, a chloroform consumer chemical product (CCP) reference material (RM) is successfully developed, with potential to be used in the proficiency testing of hazardous compounds in CCPs for analysis and testing agencies. Validation experiments are rigorously conducted to evaluate whether the RM meets the requirements set by the ISO 13528 and ISO Guide 35, using a reliable GC/MS method for the analysis of chloroform. The obtained calibration plot linearity, limit of detection (LOD), and limit of quantitation (LOQ) are excellent. The developed RM meets the homogeneity and stability requirements; the between-unit (s_bb) and within-unit (s_wb) standard deviations are less than 2.5%, and the stability is found to be guaranteed for 50 days.

• Journal of Food Hygiene and Safety
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• v.12 no.4
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• pp.288-293
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• 1997

Analytical method using capillary GC/ECD was developed to determine trace residues of chlofluazuron, 1-[3, 5-dichloro-5-trifluoromethyl-2-pyridyloxy)phenyl]-3-(2, 6-difiuorobenzoyl), in meat, and applied to analyze the residues in domestic and imported meats. The analytical scheme developed does not require column chromatographic cleanup; chlorfiuazuron was extracted with diethyl ether and petroleum ether (50: 50), partitioned against acetonitrile, cleaned up with silica Sep-Pak cartridge, identified GC/ECD, and comfirmed by GC/MS. The mean recoveries of the pesticide in meat fortified with standard solution 0.1, 0.5, 0.1 mg/kg were ranged from 82 to 95%. The limit of detection and limit of quantitation were 0.001 and 0.005 mg/kg, respectively. Chlorfluazuron residues were not found in domestic samples, but found in imported Australian beef ranging from 0.02 to 0.17 mg/kg, detected by 18% among the samples.