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A quantitative structure-retention relationship study was performed for 286 flavor compounds with highly structural diversity on different stationary phases of different polarities. Firstly, the structure-retention relationship was statistically explored using constitutional, topological, molecular properties, charge descriptors and quantum chemical descriptors. Some recently developed chemometric methods, such as the ones for robust analysis and variable selection were firstly employed to predict accurately the gas chromatographic retention indices. The stability and validity of models have been tested by internal and external validation, and good robustness and predictive ability were obtained. The resulting QSRR models were well correlated, with the square of correlation coefficient for cross validation, Q, values of 0.9847, 0.9838, 0.9745 and 0.9646 on stationary phase DB5, OV101, OV17 and C20M, respectively. The molecular properties known to be relevant for GC retention index, such as molecular size, branching, electron density distribution and hydrogen bond effect were well covered by generated descriptors. The descriptors used in models on four stationary phases were compared, and some reasonable explanations about gas chromatographic retention mechanism were obtained. The developed model may be useful for the prediction of flavor compounds while experimental data are unavailable. [ABSTRACT FROM AUTHOR]

Concentration of heavy metals in blood and urine of rabbit after inhaling three different kinds of cigarette was studied through the animal passive smoking pattern. The samples were prepared by nitric acid solution digestion and determination of seven kinds of heavy metals including Hg, Se, Sn, Pb, Cd, Ni and Cr was performed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The ICP-AES method was established with good precision and accuracy, relative standard deviation ( n=6) was between 2.9% and 5.9%, and the recovery was in the range of 95.0%-104.2%. Concentration of six heavy metals increases in some extent in blood and urine after period of smoking and the increasing of heavy metals in blood and urine all shows time dependence. Significantly higher heavy metal levels are observed in the blood and urine of the cigarette inhaling rabbits in the exposed group. The concentration of six kinds of heavy metals in the blood of the rabbit increases after 16 weeks exposing to cigarette smoking. Three times of Hg, ten times of Se and trace amount of Pb, Cd, Ni and Cr are detected in the blood after 16 weeks of smoking. For urine samples, about three times of Hg, two times of Se, five times of Pb and trace amount of Cd are detected after 16 weeks of inhalation of cigarette. Comparatively, higher concentration of heavy metals are detected after inhaling of Nise cigarette. [ABSTRACT FROM AUTHOR]

The essential oils from two varieties of Osmanthus fragrans have been extracted by steam distillation and analyzed by gas chromatography-mass spectrometry with the help of heuristic evolving latent projections (HELP), an effective chemometric resolution method. The overlapped peak clusters were resolved into pure chromatograms and pure mass spectra with HELP. Identification of the components was by comparison of temperature-programmed retention indices (PTRIs) and by similarity searches in the National Institute of Standards and Technology mass database. Quantitative results were obtained by overall integration of the peaks. The reliability of the qualitative and quantitative results was greatly improved by using HELP and PTRIs. The main components from O. fragrans Lour. var. thunbergii Mak. (TM) and O. fragrans Lour. var. aurantiacus Mak. (AM) were 1,2-epoxy linalool and nonanal, respectively. In total, 52 volatile components in essential oil of TM and 45 in AM were analyzed qualitatively and quantitatively, accounting for 95.67 and 92.28% total contents of the essential oils. [ABSTRACT FROM AUTHOR]

Chromatography-mass spectrometry (GC-MS) was used to analyze the volatile components of cut tobacco samples with the help of heuristic evolving latent projections (HELP). After extracting with simultaneous distillation and extraction method, the volatile components in cut tobacco were detected by GC-MS. Then the obtained original two-dimensional data were resolved into pure mass spectra and chromatograms. The qualitative analysis was performed by similarity searches in the national institute of standards and technology (NIST) mass database with the obtained pure mass spectrum of each component and the quantitative results were obtained by calculating the volume of total two-way response. The accuracy of qualitative and quantitative results were greatly improved by using the two-dimensional comprehensive information of chromatograms and mass spectra. 107 of 141 separated constituents in the total ion chromatogram of the volatile components were identified and quantified, accounting for about 88.01% of the total content. The result proves that the developed method is powerful for the analysis of complex cut tobacco samples. [ABSTRACT FROM AUTHOR]

Uniform design was used to optimize extraction condition of direct refluence extraction of coumarins from the Chinese traditional medicine of radix angelicae pubescentis(Duhuo); the sum peak area of coumarins separated with high performance liquid chromatography (HPLC) at detection wavelength of 320 nm was considered as detection index, two factors of solvent concentration and extraction time were mainly studied at extraction temperature of 85°C and a volume ratio of solvent to sample of 10 : 1. Optimal subclass, quadric polynomial step by step aggression and neural network method were applied to process the experimental results. The results show that the first and second methods give the same factors combination (concentration of ethanol: 95%, extraction time: 3.6 h) and the second method is much better than the first one. The extraction model is consequently developed. [ABSTRACT FROM AUTHOR]

The volatile and semi-volatile components in tobacco flavor additives were extracted by both simultaneous distillation extraction and solid-phase micro-extraction. Extraction conditions for solid-phase micro-extraction were optimized with information theory. Then, detection were accomplished by gas chromatography-mass spectrometry. Characteristic of each method was compared. Qualitative analysis and quantitative analysis of 6# tobacco flavor sample were accomplished through both simultaneous distillation extraction and solid-phase micro-extraction. The experimental results show that solid-phase micro-extraction method is the first choice for qualitative analysis and simultaneous distillation extraction is another good selection for quantitative analysis. By means of simultaneous distillation extraction, 20 components are identified, accounting for 92.77% of the total peak areas. Through solidphase micro-extraction, there are 17 components identified accounting for 91.49% of the total peak areas. The main aromatic components in 6# tobacco flavor sample are propanoic acid, 2-hydroxy-, ethyl ester, menthol and menthyl acetate. The presented method has been successfully used for quality control of tobacco flavor. [ABSTRACT FROM AUTHOR]

Gas chromatography — mass spectrometry (GC-MS) coupled with chemometric resolution upon two-dimensional data was employed to analyze the constituents of essential oils of essential oils of Angelica sinensis. Constituents in essential oils of Angelica sinensis root were identified by GC-MS with the help of subwindow factor analysis (SFA) method resolving two-dimensional original data into mass spectra and chromatograms. 76 of 97 separated constituents in essential oil of Angelica sinensis root were identified and quantified, and they account for about 91. 36% of the total content. The results show that ligustilide, butylene phthalide, 2-methoxy-4-vinylphenol, carvacrol, alloocimene,2,6,6-trimethylbicyclo-[3,1,1]hept-2-ene are the main constituents in essential oil of Angelica sinensis root. [ABSTRACT FROM AUTHOR]

A simple, fast, sensitive, and reproducible isocratic liquid chromatography-mass spectrometry (LC-MS) method coupled with an atmospheric pressure chemical ionization (APCI) interface for simultaneous separation and determination ofL-arginine (ARG) and its methylated metabolites,N-monomethyl-L-arginine (MMA),N G,N G-dimethylarginine (asymmetric dimethyl arginine, ADMA), andN G,N' G-dimethylarginine (symmetric dimethyl arginine, SDMA), in human plasma is presented. Sample pretreatment is not required other than deproteinization with 5-sulfosalicylic acid (5-SSA). Satisfactory chromatographic separation was achieved on a 2.0×150-mm Shimadzu VP-ODS column by using a mobile phase consisting of water/acetonitrile (90/10, v/v) containing 0.5% trifluoroacetic acid (TFA). Positive selective ion monitoring (SIM) mode was chosen for quantification of each analyte. The positively protonated molecular ions [M+H]+ of ARG, MMA, ADMA, and SDMA were monitored atm/z175, 189, 203, and 203, respectively.L-Homoarginine was used as the internal standard (IS) for the assay. The limits of quantification (LOQs) were found to be 1.0 µmol L-1 for ARG, and 0.2 µmol L-1 for MMA, ADMA, and SDMA. The inter-assay precision and accuracy were in the range of 1.8-4.9% and -3.0-5.0%, respectively. The intra-assay precision and accuracy were in the order of 1.7-4.6 and -2.6-4.0%, respectively. The recoveries were between 90.0 and 106.6%. The levels of ARG, MMA, ADMA, and SDMA in human plasma were also determined using the developed method. [ABSTRACT FROM AUTHOR]

A simple, sensitive and reproducible high performance liquid chromatography-mass spectrometry coupled with electrospray ionization method for simultaneous separation and determination of adenine, adenosine and uridine was developed. The analytical column is a 2.0 mm × 150 mm Shimadzu VP-ODS column and volume fraction of the mobile phase is 86.5% water, 12.0% methanol and 1.5% formic acid. 2-chloroadenosine was used as internal standard. Selective ion monitoring mode and selective ion monitoring ions at ratio of mass to electric charge of 136 for adenine, 268 for adenosine and 267 for uridine were chosen for quantitative analysis of the three active components. The results show that the regression equations and linear range are Y=0.062X+0.005 and 2.0 – 140.0 µg·mL−1 for adenine, Y=0.049X+0.004 and 4.0–115.0 µg · mL−1 for uridine, Y=0.154X+0.014 and 1.0–125.0 µm · mL−1 for adenosine. The limits of detection are 0.6 µg·mL−1 for adenine, 1.0 µg·mL−1 for uridine and 0.2 µg·mL−1 for adenosine. The recoveries of the three constituents are from 96.6% to 103.2%. [ABSTRACT FROM AUTHOR]

A combined approach of sub-window factor analysis and spectral correlative chromatography has been employed to analyze the constituents of essential oils of Dong quai. Essential oils are the main pharmacological active individuals of Dong quai. Some constituents in the main root of Dong quai have been identified by GC-MS with the help of sub-window factor analysis resolving two-dimensional original data into mass spectra and chromatograms. Correlative constituents in another part of the root fiber have been recognized by spectral correlative chromatography. Seventy six of 97 separated constituents in the essential oil of main root were identified and quantified, accounting for about 91.36% of the total content. Sixty seven correlative components in the essential oil of root fiber were recognized. The result proves that the combined approach is powerful enough for the analysis of complex herbal samples. [ABSTRACT FROM AUTHOR]

An improved ethylene blue method for determination of sulfide is developed. It has been adapted to a direct determination of sulfide by both common spectrophotometric method and total differential spectrophotometric method. In common spectrophotometric method, the calibration curve is A=1.69 ρ+0.006 and the correlation coefficient is 0.9994. The apparent molar absorptivity is 5.42 × 104 L·mol−1·cm−1 and calibration curve is liner when ρ is in the range of 0–0.9 mg·L−1. In total differential spectrophotometric method, the calibration curve is A=9.25 ρ + 0.004 and the correlation coefficient is 0.9996. The apparent molar absorptivity is 2.96 × 105 L·mol−1 L·mol−1·cm−1 and calibration curve is liner when ρ is in the range of 0–0.10 mg·L−1. The sensitivity of this method is increased significantly compared with the former ethylene blue method. The speed of reaction is also faster than the former one. The limit of detection is found to be 1.0 ng·mL−1 by both common spectrophotometric method and total differential spectrophotometric method. Ten replicate analyses of a sample solution containing 100 ng·mL−1 sulfide give a relative standard deviation of 1.8%. The effects of various cations and anions on the determination of sulfide are studied and procedures for removal of interference is described. The method is used for the determination of sulfide in environment samples with satisfactory results. [ABSTRACT FROM AUTHOR]