• Environmental Analysis Health and Toxicology
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• v.16 no.4
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• pp.181-188
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• 2001

A gas chromatographic method was established for the simultaneous determination of urinary nicotine and cotinine. The analytes in basified urine containing a sufficient amount of Na$_2$S0$_4$were extracted into dichloromethane by vigorous shaking. Into the transferred organic phase was added a small amount of acidified methanol (0.5 N HCI in methanol), followed by concentrating the mixture to dryness using a mild stream of nitrogen gas. The concentrate was reconstituted with methanol and the final solution analyzed using the gas chromatograph equipped with the nitrogen-phosphorus detector. The reproducibility tests showed coefficients of variation less than 11％ for both compounds. The percent recovery for both analytes ranged from 88 to 103％. The estimated method detection limits for nicotine and cotinine were 0.60 and 5.1 ng/mL, respectively. Extraction efficiencies for both nicotine and cotinine apparently declined without the addition of Na$_2$S0$_4$into the urine. Moreover, the absence of methanolic HCI in the extract resulted in almost complete evaporation of nicotine and partial loss of cotinine during the concentration process, indicating that the formation of nicotine-HCI and cotinine-HCI species is prerequisite to the suppression of the loss of both compounds.

• Food Science and Preservation
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• v.7 no.4
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• pp.409-413
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• 2000

Previously, the methanolic extracts of thirty Korean medicinal plant seeds were screened for tyrosinase inhibitors using a rapid and simple TLC method, which was superior to a conventional spectrophotometrical in vitro assay. As a result, the methanolic extracts of Thuja orientalis seeds was found to have strong tyrosinase inhibitory activity. To isolate active tyrosinase inhibitors, the seeds were defatted with n-hexane under reflux, and then extracted twice with methanol under reflux at 90$^{\circ}C$. The methanolic extract was evaporated to a small volumn in vacuo, and then successively fractionated with ether, ethyl acetate and n-butanol. The ether extract showing significant tyrosinase inhibitory activity was solubilized with 5% NaHCO$_3$and then acidified with 6N HCI. The ether souble acidic fraction was successively ohromatographed on silica gel, Sephadex LH-20 and preparative TLC. Among four compounds isolated, two of them showed stronger tyrosinase inhibitory activity, comparable to that of L-ascorbic acid (IC$\sub$50/=28$\mu\textrm{g}$/$m\ell$). These results suggest that Thuja orientalis seeds may be useful as potential sources of antibrowning agents in fruits and vegetables, and anti-melanoma agents in cosmetics and phamaceuticals.

• YAKHAK HOEJI
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• v.51 no.3
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• pp.206-213
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• 2007

Recently estimating the uncertainty of an analytical result has become an essential part of quantitative analysis. This study describes the uncertainty of the measurement for the determination of methamphetamine and its major metabolite amphetamine in human hair, The method consists of washing, drying, weighing, incubation and extraction with methanolic HCI solution, clean-up, trifluoroacetyl derivatization, and qualification/quantification of residues by gas chromatography/mass spectrometry (GC/MS). Traceability of measurement was established through traceable standards and calibrated volumetric equipment and measuring instruments. Measurement uncertainty associated with each analyte in real samples was estimated using quality control (QC) data. The main source of combined standard uncertainty comprised two components, which are uncertainties associated with calibration linearity and variations in QC, while those associated with preparation of analytical standards and sample weighing were not so important considering the degree of contribution. Relative combined standard uncertainties associated with the described method ranged for individual analytes from 4.99 to5.03%.