The determination of benzene, toluene, p-xylene, tetrachloroethene, chlorobenzene, and dibromomethane in water by headspace analysis combined with gas chromatography-mass spectrometry (HS-GC-MS) has been investigated. An optimization strategy for the analysis of the six volatile organic compounds (VOCs) is presented with the experimental design and response surface methodology aid. Thermostatting time, temperature, and salt quantity were optimized by using a central composite design, and quadratic models relating peak areas to the three factors were built. The mathematical models were tested on a number of simulated data set and had a coefficient of R2>0.98. The factor effects were visualized as three-dimensional response surfaces and contour plots. The optimal conditions were achieved in 36.8 min, at 90 degrees C, and with 6 g of NaCl. The method showed a good agreement between the experimental data and predictive values throughout the studied parameter space, and was suitable for optimization studies of the VOCs in water by the HS-GC-MS method.
A gas chromatographic method was developed and validated for the determination of bilobalide and ginkgolides A, B, C and J in Ginkgo biloba L. The Ginkgo terpene trilactones have been dissolved in 57% of pure ethanol in purified water and separated by extraction with a mixture of toluene/ethyl acetate. After evaporation of the solvent with nitrogen and derivatization, these chemical markers have been quantified using GC-FID. The intra-day RSD was ranged from 1.13% for bilobalide to 2.34% in case of ginkgolides. The inter-day RSD was ranged from 2.54% and 3.68% for, bilobalide and ginkgolides respectively. Mean recoveries were 99.78% ± 0.82% and 99.48% ± 0.86% for ginkgolides and bilobalide, respectively. Based on chromatograms, the response of the terpene trilactones was linearly dependent on the terpene concentration, i.e. linear calibration curve was found in the range of the method and was applied to analyze standard extract (containing 5-7% total terpenoids and 22-25% total flavonoids) as working standard and for the analysis of six Ginkgo pharmaceutical products offered on the market.
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