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맹정섭,남윤규,박승희,최우영 충남대학교 농업과학연구소 1995 농업과학연구 Vol.22 No.2
Two types of modified celluloses which contain trinitrophenyl groups as chromophore were synthesized from carboxymethyl cellulose Whatman CM 70 and CM 32. Diaminoethyl groups were added to the CM 70 and CM 32 to make DAE-CM celluloses and then the DAE-CM groups were substituted by 2,4,6-trinitrophenyl groups to produce TNP-celluloses. Average particle size of the TNP-cellulose from CM 32 was 44.6 ±9.6 μm in diameter and 127.9±22.5 μm in length, which was much smaller than those from CM 70, however its TNP-moiety per gram determined by using the molar extinction coefficient 1.33×10^4 of ε-TNP-lysine at 345 nm, was 0.68 millimoles, which was 5.6-fold greater than those from CM 70. The absorption spectrum of TNP-oligosaccharides which were the soluble products of TNP-celluloses by a cellulase preparation Onozuka R-10, showed a maximal peak at 344 nm. Increases in the absorbance during hydrolysis were linear with the enzyme concentration, and the differences of slope values between two types of TNP-celluloses that the more semsitive assay could be achieved by using those from CM 32 as substrate at the low range of the enzyme concentration.
Choi, Jeong-Heui,El-Aty, A.M.Abd,Park, Young-Seok,Cho, Soon-Kil,Shim, Jae-Han Korean Chemical Society 2007 Bulletin of the Korean Chemical Society Vol.28 No.3
A fast and simple high-performance liquid chromatography (HPLC) method for the simultaneous determination of four pesticides having fungicide properties has been proposed for Panax ginseng, C. A. Meyer grown for 4, 5, or 6 years. Analytical separation was performed on C18 columns using ultraviolet detector under gradient conditions. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The HPLC response for all pesticides was linear, with determination coefficients > 0.9986. The average rate of recovery for pesticides spiked with 2 fortification levels was > 72% with relative standard deviations < 9%. The limits of quantification (LOQ) ranged from 0.03 to 0.16 ppm. These LOQs were lower than the respective maximum residue limits (MRL) established by the Korean Food and Drug Administration (KFDA), except for cyazofamid. The proposed method was used to determine pesticide residue levels in samples of ginseng obtained from Jeonnam Province (Republic of Korea). None of the pesticides were found in ginseng samples grown for 4, 5, or 6 years.
Gas Chromatography Residue Analysis of Bifenthrin in Pears Treated with 2% Wettable Powder
Jeong-Heui Choi,Xue Liu,Hee-Kwon Kim,Jae-Han Shim 한국독성학회 2009 Toxicological Research Vol.25 No.1
This study was conducted to monitor the level of bifenthrin residues in pear sprayed with 2% bifenthrin wettable powder (WP) at the recommended rate at four different schedules prior to harvest. The target analyte was extracted with acetone, partitioned into dichloromethane, and then purified by florisil chromatographic column. The residue determination was performed on a DB-5 capillary column using GC with electron capture detector (ECD). Linearity of this method was quite good (r² = 0.9951) in the concentration ranged from 0.2 ㎎/㎏ to 10 ㎎/㎏. Recovery test was carried out at two concentration levels, 0.2 ㎎/㎏ and 1.0 ㎎/㎏, in three replicates, and their rates were from 82.9% to 107.2%. No quantitative bifenthrin was detected in pear of all kinds of treatments including the treatment sprayed 4 times until 7 days before harvest. This sensitive and selective method can be used to monitor the trace residual amounts of bifenthrin in pear in a quite low concentration level.
Choi, Jeong-Heui,Mamun, M.I.R.,Shin, Eun-Ho,Kim, Hee-Kwon,El-Aty, A.M. Abd,Shim, Jae-Han Korean Society of ToxicologyKorea Environmental Mu 2008 Toxicological Research Vol.25 No.4
Pesticide residues play several key roles as environmental and food pollutants and it is crucial to develop a method for the rapid determination of pesticide residues in environments. In this study, a simple, effective, and sensitive method has been developed for the quantitative analysis of methoxyfenozide in water and soil when kept under laboratory conditions. The content of methoxyfenozide in water and soil was analyzed by first purifying the compound through liquid-liquid extraction and partitioning followed by florisil gel filtration. Upon the completion of the purification step the residual levels were monitored through high performance liquid chromatography(HPLC) using a UV absorbance detector. The average recoveries of methoxyfenozide from three replicates spiked at two different concentrations and were ranged from 83.5% to 110.3% and from 98.1% to 102.8% in water and soil, respectively. The limits of detection(LODs) and limits of quantitation(LOQs) were 0.004 vs. 0.012 ppm and 0.008 vs. 0.024 ppm, respectively. The method was successfully applied to evaluate the behavioral fate of a 21% wettable powder(WP) methoxyfenozide throughout the course of 14 days. A first-order model was found to accurately fit the dissipation of methoxyfenozide in water with and a $DT_{50}$ value of 3.03 days was calculated from the fit. This result indicates that methoxyfenozide dissipates rapidly and does not accumulate in water.