OV-17 Column Research Articles

CORAL: Quantitative Structure Retention Relationship (QSRR) of flavors and fragrances compounds studied on the stationary phase methyl silicone OV-101 column in gas chromatography using correlation intensity index and consensus modelling

The quantitative structure-retention relationship (QSRR) is a significant approach in chromatography and is used to predict the retention time of unknown compounds. In the present research article, the QSRR approach is employed to develop robust models of 1176 flavor and fragrance compounds on the OV-101 glass capillary gas chromatography column using a statistical parameter “correlation intensity index (CII)”. This CII parameter is featured in the most recent release of the CORAL programme (www.insilico.eu/coral). The optimal descriptor i.e. descriptor of correlation weight (DCW) computed by simplified molecular input-line entry system (SMILES) notation is employed to build QSRR models. Two target functions, TF1 (WCII=0) and TF2 (WCII=0.3) are applied to design 12 QSRR models from six splits using the balance of correlation strategy. The models created using CII are better in terms of statistical results. The numerical value of Rvalidation2=0.9561 of TF2Split1 is found to be considerably greater than that of the Rvalidation2 of the other splits of both target functions, hence, it is acknowledged as a leading model. The lists of structural attributes responsible for the changes in the retention index (RI) of flavors and fragrances compounds are also retrieved and discussed. Finally, a consensus model is built utilising the allocation structure of split 1 and the modified consensus (CM1) i.e. an average of predictions from all 'qualified' Individual models is found best model based on MAE (95%; test). The numerical value of the determination coefficient (R2) of the test set for the modified consensus (CM1) model is found 0.9772 which is higher than the leading Model.

Least Absolute Deviation Regression and Least Squares for Modeling Retention Indices of Set Compounds Food and Pollutants of the Environment

Considering the importance of the statistical analysis of regression in modeling based separately on study for Quantitative structure retention indices on Carbowax 20 M (ICw20M) and OV-101 columns (IOV-101) relationships (QSRR) are determined for 114 pyrazines. The detection of influential observations for the standard least squares regression model is a problem which has been extensively studied. Least Absolute Deviation regression diagnostics offers alternative dicapproaches whose main feature is the robustness. Here a nonparametric method for detecting influential observations is presented and compared with other classical diagnostics methods. With have been applied for modeling separately retention indices of the same set of (89 pyrazines of Training and 25 of Test) eluted on Columns OV-101 and Carbowax-20M, using theoretical molecular descriptors derived from DRAGON Software and validating the results in the state approached graphically by Probability plot of the error and approached tests statistics of Anderson-Darling, in finished by the confidence interval thanks to robustness concept to check if errors distribution is really approximate.

Quantitative Structure–Retention Relationship Modeling of Morphine and Its Derivatives on OV-1 Column in Gas–Liquid Chromatography Using Genetic Algorithm

In this paper, a back propagation artificial neural network (BP-ANN) was used for quantitative structure–retention relationship (QSRR) modeling of retention time (t R) of 57 morphine and its derivatives. The molecular descriptors were calculated for each compound. By applying a genetic algorithm, the most relevant descriptors were selected to build the QSRR model. The selected descriptors were: Hosoya Index, kappa1, and most negative potential. The prediction results from the BP-ANN were in good agreement with the experimental values. The optimal QSRR model was developed based on a 3-3-1 artificial neural network architecture using molecular descriptors calculated from molecular structure alone. The root-mean-square error (RMSE) and squared correlation coefficient (R 2) for the ANN model were 0.3996 and 0.9559 for the training set (42 molecules) and 0.6052 and 0.9540 for the prediction set (15 molecules), respectively.

Study on Quantitative Structure-Retention Relationships (QSRR) for Oxygen-Containing Organic Compounds Based on Gene Expression Programming (GEP)

Gene Expression Programming (GEP) is a novel genetic algorithm, a highly effective, stable random searching method. We take GEP to make models of Quantitative Structure-Retention Relationship (QSRR) for a series of oxygen-containing organic compounds of GC retention index, and compare the predictive results with Artificial Neural Network (ANN) and Multiple Linear Regression (MLR). The correlation coefficient on OV-1 column is 0.9919, 0.9891 and 0.9911 for GEP, ANN and MLR respectively, on SE-54 column is 0.9955, 0.9892, and 0.9917. It is shown that the predicted results by GEP are in good agreement with experimental ones, better than those of ANN and MLR.

QSPR analysis for the retention index of flavors and fragrances on a OV-101 column

A predictive quantitative structure–property relationships (QSPR) is developed for modeling the retention index measured on the OV-101 glass capillary gas chromatography column, in a set of 1208 flavor and fragrance compounds. The 4885 molecular descriptors are calculated using the Dragon software and then are simultaneously analyzed through multivariable linear regression analysis using the replacement method (RM) variable subset selection technique. We proceed in three steps, the first one by considering all descriptor blocks, the second one by excluding conformational descriptors blocks, and the last one by analyzing only 3D-descriptors families. The models are properly validated through an external test set of compounds. Cross-validation methods such as leave-one-out and leave-more-out are applied, together with Y-randomization and applicability domain analysis. The results clearly suggest that 3D-descriptors do not offer relevant information for modeling the retention index, while a topological index such as the solvation connectivity index of first order has a high relevance for this purpose.

Micromethod for the determination of bupivacaine in maternal and foetal blood during obstetric analgesia.

Abstract A method for the determination of bupivacaine in maternal and foetal blood during obstetric analgesia is described. The drug and the internal standard, 1-pentyl-2-(2,6-xylylcarbamoyl)-piperidine, are initially extracted into methylene chloride. Perchloric acid is added to retain bupivacaine and the standard as Perchlorates in the organic phase accomplishing a selective separation from less hydrophobic amines. Bupivacaine and the standard are then re-extracted into sulphuric acid, followed by a purification with methylene chloride. The aqueous extract is finally made alkaline and the compounds extracted into 10 μl methylene chloride. This extract is analysed by gas chromatography using a 3% OV-17 column. The standard deviation of the method at therapeutic concentrations is about 10% and the lowest level which can be determined with reasonable accuracy is 15 ng ml−1.

Bis(isovalerylacetone)ethylenediimine Nickel(II) as Mixed Stationary Phase for Gas Chromatography

Bis(isovalerylacetone)ethylenediimine Nickel (II) (IVA(2)enNi) was examined as a mixed stationary phase with OV1 on Chromosorb G/NAW 60-80 mesh size for gas chromatography (GC) separation of aromatic hydrocarbons, heteroaromatics, alcohols, aldehydes, ketones, esters, nitro-, and amino compounds. Forty-six compounds were examined, and the GC results were compared with those obtained with 3% OV1 on Chromosorb G/NAW 60-80 mesh size under similar operating conditions. Improved resolutions, peak asymmetry, number of theoretical plates, and Kovats indices were obtained on the mixed stationary phase 3% OV1 + 5% IVA(2)enNi (w/w) compared to 3% OV1 column. The stability constant (K(m)), enthalpies (DeltaH), entropies (DeltaS), and Gibbs free energies (DeltaG) of the GC elution on column (2 m x 3 mm i.d.) packed with 3% OV1 + 5% IVA(2)enNi (w/w) on Chromosorb have been calculated. Donor-acceptor complexation in the gas phase indicated by the negative values of enthalpy (-DeltaH) were within 9.4-12.38 Kcal/mol, and Gibbs free energy (-DeltaG) ranged from 1.48 to 4.24 Kcal/mol. The retention time transformation on both the phases were calculated. The obtained ratios from the stationary phases 3% OV1 and 3% OV1 + 5% IVA(2)enNi (w/w) were plotted on the x-axis and y-axis, respectively. Two-dimensional chromatographic plots for alkanes, aromatics, heteroaromatics, ketones, alcohols, esters, and nitro compounds were obtained with coefficient of determination within 0.4934 and 0.9617, which is indicative of some different kinds of interaction of two stationary phases with the solutes.

Studies on GLC of TMS Derivatives of Organic Acid and Fatty Acid with QF-1, OV-17 and SE-30 Columns

Studies on GLC of TMS Derivatives of Organic Acid and Fatty Acid with QF-1, OV-17 and SE-30 Columns

Comparative analysis of volatile constituents between recipe jingfangsan and its single herbs by GC‐MS combined with alternative moving window factor analysis method

Comparative analysis of volatile constituents between recipe jingfangsan and its single herbs was performed by GC-MS combined with alternative moving window factor analysis (AMWFA), a new chemometric resolution method. Identification of the compounds was also assisted by comparison of temperature-programmed retention indices (PTRIs) on the OV-1 column with authentic samples. In total, 36, 29, and 42 volatile components in essential oil of Herba schizonepetae (HS), Radix saposhnikoviae (RS), and the recipe were respectively determined qualitatively and quantitatively, accounting for 81.80, 82.62 and 85.98% total contents of volatile oil of HS, RS, and the recipe respectively. Analysis by the method of AMWFA indicates that there are 22 common volatile constituents between the recipe and single herbal medicine HS, and 14 common volatile constituents between the recipe and single herb medicine RS. The experimental results also show that the volatile components of the recipe in number are almost addition of that of two single herbal medicines HS and RS, and are mainly from the single herbal medicine HS.

Comparative analysis of essential components between the herbal pair Radix Saposhnikoviae-Rhizoma seu Radix Notopterygii and its single herbs by GC-MS combined with a chemometric resolution method.

Comparative analysis of essential components in the herbal pair Radix Saposhnikoviae-Rhizoma seu Radix Notopterygii and its single herbs is performed using two-dimensional gas chromatography-mass spectrometry data coupled with a chemometric method, named alternative moving window factor analysis. Identification of the compounds is also assisted by comparison of temperature-programmed retention indices (PTRIs) on the OV-1 column with authentic samples. The experimental results show that the main volatile chemical components in the herbal pair are mainly from Rhizoma seu Radix Notopterygii, and the number of essential chemical components in the herbal pair is almost equal to the sum of the number in the two single herbs but with a different quantity.

Palladium(II) chelate of tetradentate Schiff base as mixed stationary phase for gas chromatography

Bis(acetylacetone)ethylenediiminepalladium(II) (PdAA2en) was examined as a mixed stationary phase with OV-1 on Chromosorb G/NAW 60-80 mesh size for the GC separation of aromatic hydrocarbons, heteroaromatics, alcohols, aldehydes, ketones, esters, and nitro compounds. Forty-two compounds were examined and the GC results were compared with those obtained with 3% OV-1 on Chromosorb G/NAW 60-80 mesh size under similar operating conditions. Improved resolution, peak asymmetry, theoretical plate numbers, and Kovats indices were obtained on the mixed stationary phase of 3% OV-1 + 5% PdAA2en compared to 3% OV-1 column. The stability constant (Km), enthalpies (deltaH), entropies (deltaS), and Gibbs free energies (deltaG) of the GC elution on the column (2 m x 3 mm id) packed with 3% OV-1 + 5% PdAA2en on Chromosorb G/NAW 60-80 mesh size have been calculated. Donor-acceptor complexation in the gas phase is indicated by negative values of enthalpy (-deltaH) within 5.81 to 10.89 kcal/mol and Gibbs free energy (-deltaG) from 1.34 to 4.08 kcal/mol. The retention time transformations on both the phases were calculated and the ratios obtained from the stationary phases 3% OV-1 and 3% OV-1 + 5% PdAA2en were plotted on the x-axis and the y-axis, respectively, and the coefficients of determination for alkanes, aromatic and heteroaromatics, ketones, and alcohols were observed to lie within 0.5253 to 0.9742, indicative of some different kinds of interaction of the two stationary phases with the solutes.

Characterization of wax esters, free fatty alcohols and free fatty acids of crude wax from sunflower seed oil refineries

The sunflower seed wax (10–12%) from oil refineries was purified through two steps, namely, extraction using solvents and precipitation with chilled acetone. Fatty esters, free fatty alcohols and free fatty acids were separated by thin-layer chromatography (TLC). The fractions of fatty esters and free fatty alcohols were separated and identified by gas chromatography (GC) using a Dexil-300 column and OV-101 column, respectively, at temperatures from 150–290 °C and were further confirmed by Gas chromatography–mass spectrometry (GC–MS), using a capillary silica column SPB™-1 coated with polydimethyl siloxane. Among the long chain fatty esters (C 38–C 54), comprised of one unit of fatty alcohol and one unit of fatty acid through an ester linkage, the major esters were C 40–C 44, of which C 42 was predominant. These fatty esters, upon hydrolysis, followed by methylation and subsequent GC–MS analysis, showed the presence of C 16–C 30 fatty acids in the bound form, whereas methylation of native wax indicated the presence of C 18–C 30 fatty acids in the free form. Acetylation of hydrolysis product showed the presence of C 18–C 30 fatty alcohols in the bound form, where as acetylation of native wax indicated that the C 18–C 32 fatty alcohols were in the free form. n-Triacontanol (C 30), a plant growth regulator, was found in both free and bound forms.

P-Hydroxybenzoic Acid Synthesis in Mycobacterium tuberculosis

Glycosylated p-hydroxybenzoic acid methyl esters and structurally related phenolphthiocerol glycolipids are important virulence factors of Mycobacterium tuberculosis. Although both types of molecules are thought to be derived from p-hydroxybenzoic acid, the origin of this putative biosynthetic precursor in mycobacteria remained to be established. We describe the characterization of a transposon mutant of M. tuberculosis deficient in the production of all forms of p-hydroxybenzoic acid derivatives. The transposon was found to be inserted in Rv2949c, a gene located in the vicinity of the polyketide synthase gene pks15/1, involved in the elongation of p-hydroxybenzoate to phenolphthiocerol in phenolic glycolipid-producing strains. A recombinant form of the Rv2949c enzyme was produced in the fast-growing non-pathogenic Mycobacterium smegmatis and purified to near homogeneity. The recombinant enzyme catalyzed the removal of the pyruvyl moiety of chorismate to form p-hydroxybenzoate with an apparent K(m) value for chorismate of 19.7 microm and a k(cat) value of 0.102 s(-1). Strong inhibition of the reaction by p-hydroxybenzoate but not by pyruvate was observed. These results establish Rv2949c as a chorismate pyruvate-lyase responsible for the direct conversion of chorismate to p-hydroxybenzoate and identify Rv2949c as the sole enzymatic source of p-hydroxybenzoic acid in M. tuberculosis.

Gas Chromatographic Method for Putrescine and Cadaverine in Shrimp

A gas-liquid chromatographic method developed for the determination of putrescine and cadaverine in fishery products was modified for application to the determination of diamines in shrimp. Addition of potassium chloride and hydrochloric acid to the methanol-water extraction solvent resulted in increased recovery of the diamines and minimized gel formation. The recovery of putrescine increased on average from 64 to 98%, and the recovery of cadaverine increased from 85 to 93%. The chromatographic separation of the derivatized diamines was significantly improved with a change from an OV-225 column (cyanopropyl methyl phenyl methyl silicone) to a more polar HP-Innowax column (crosslinked polyethylene glycol). Background levels of putrescine and cadaverine in known high-quality shrimp ranged from 0 to 0.7 ppm. Shrimp that failed sensory examination generally contained putrescine at levels >4.8 ppm and cadaverine at levels >1.3 ppm.

Gas Chromatographic Method for Putrescine and Cadaverine in Canned Tuna and Mahimahi and Fluorometric Method for Histamine (Minor Modification of AOAC Official Method 977.13): Collaborative Study

A collaborative study was conducted to test a modification to the AOAC fluorometric method for histamine (AOAC Official Method 977.13) that substitutes 75% methanol as the extracting solvent. All other steps remain unchanged. The extracts prepared with 75% methanol were also used to collaboratively test a gas chromatographic (GC) method for determination of putrescine and cadaverine in seafood. In the GC method, the extracted diamines are converted to fluorinated derivatives, the reaction mixtures are passed through solid-phase extraction columns, and the derivatives are quantitated by electron capture GC after separation on an OV-225 column. Fourteen laboratories using the GC method for putrescine and cadaverine and 16 laboratories using the fluorometric method for histamine analyzed 14 canned tuna and raw mahimahi (including blind duplicates and a spike) containing 0.2-2.6 ppm putrescine, 0.6-9.1 ppm cadaverine, and 0.6-154 ppm histamine. At the 5 ppm level, recoveries ranged from 71 to 102% for putrescine and 77 to 112% for cadaverine; the respective repeatability relative standard deviations (RSDr) were 5.2 and 15%, and the respective reproducibility relative standard deviations (RSDR) were 8.8 and 18%. At the 50 ppm level, histamine recoveries ranged from 84 to 125%, RSDr was 3.6%, and RSDR was 9.4%. The GC method for determination of putrescine in canned tuna and cadaverine in canned tuna and mahimahi has been adopted first action by AOAC INTERNATIONAL, and the AOAC Official Method 977.13, Histamine in Seafood, Fluorometric Method, has been modified.

Non-methane hydrocarbons in industrial locations of Bombay

Concentrations of non-methane hydrocarbons in atmospheric air are measured in areas close to five industrial locations in the city of Bombay during the period March 1993 to May 1994. Seventeen hydrocarbons, viz., ethane, ethylene, acetylene, propane, propylene, i-butane, n-butane, i-pentane, n-pentane, n-hexane, benzene, n-heptane, toluene, ethylbenzene, p-xylene, o-xylene, n-decane and identified in 260 urban air samples using a cryogenic preconcentration system and a Gaschromatograph with a flame-ionization detector. Analysis is done on packed columns: N-octane Poracil C column for the C 2C 5, OV-101 column for the C 6 and above hydrocarbons. A significant fraction of the C 6C 10 hydrocarbons remains unidentified. About 44% of the samples collected in the Thane region of Bombay (with large number of chemical industries) and 50.8% of the samples collected in the Mahul region of Bombay (adjacent to two oil refining units) showed concentrations above 240 ppbv, which is the recognized air quality standard for zones with chemical industries by the Maharashtra Pollution Control Board. The concentrations of C 6C 10 hydrocarbons were more than that for C 2C 5 at the two industrial sites located at Thane region of Bombay, while the C 2C 5 hydrocarbons were more at the Refineries area near Mahul, Bombay. Benzene concentrations are observed to be above 5.0 ppbv at four of the five chosen sites and its concentration was more than that of toluene. These studies indicate significantly higher ratios for some of the individual hydrocarbon to acetylene in air than corresponding autoexhaust values.

Implicit characteristic parameter of a programmed temperature retention index database

In a programmed temperature retention index (PTRI) database, there exists a characteristic parameter rt0/β that can be calculated if the experimental parameters are clearly given. This characteristic parameter can be used to flexibly reproduce the original PTRI data under chromatographic conditions different from those originally given. As this characteristic parameter is not explicitly given, it is suggested to name this parameter as the implicit characteristic parameter (TCP) of a PTRI database. The ICP in White's PTRI database was easily found and used satisfactorily to reproduce PTRI of some test compounds using either a Hewlett-Packard ultra-performance OV-1 column or a self-coated OV-1 column. The reproduction of PTRI could not be realized on columns of different materials. The fact that several PTRI databases measured on glass capillary columns could not satisfactorily be reproduced on fused silica column is explained.

Extraction-gas chromatographic method for the determination of organophosphorus compounds as lubricating oil additives

A direct solvent extraction-gas chromatographic method was developed for the determination of organophosphorus compounds as additives in lubricating oil for control purposes. Ethanol (95%) was used as an extractant and Varian GC-Vista 6000 gas chromatograph with a 3% OV-17 column and dual flame photometric detector was used for the measurements under the optimum experimental conditions. The accuracy and precision of the method were determined by preparing model samples of different types of engine lubricating base oils blended with different amounts of triphenyl phosphate or p-tricresyl phosphate ranging from 0.002 to 1.0% (w/w), which correspond to 2.12–955 ppm of phosphorus. The results showed errors ranging from 0.40 to 2.96% and the relative standard deviation did not exceed 3%. This method was applied successfully to the determination of phosphorus compounds in different types of lubricating oils. Each sample requires 20 min for analysis and 72 samples can be analysed per 8-h day. The effect of storage on the amount of phosphorus as an additive in lubricating oils was also considered.

Determination of Diethylstilbestrol Glucuronide in Beef by Gas Chromatography.

A gas-liquid chromatographic (GLC) method was developed for the determination of diethylstilbestrol glucuronide (DESG), a metabolite of diethylstilbestrol, in beef. DESG was extracted from beef with 90% acetonitrile. The extract was cleaned up without hydrolysis of DESG by Sep-pak NH2 cartridge and C18 cartridge. The purified extract was evaporated to dryness and reacted with pentafluoropropionic acid anhydride (PFPA) for 50 min at 50°C. PFPA derivatives of DESG were measured by GLC, using a 2% OV-17 column and electron capture detector. Recoveries of DESG obtained from beef spiked at 0.005-0.02 μg/g (as is DES) levels were 86.8-89.2%. The detection limit of DESG was 0.001 μg/g.

A study on the values computed by dieticians and chemical analysis of fats, cholesterol, and P/S ratio in food.

Dieticians computed the fat and cholesterol contents of 11 foods that were commercially produced as ready-to-eat food from food component lists and obtained the P/S ratio (polysaturated/saturated fatty acids) from the fatty acid component list. Meanwhile the same foods were diluted and homogenized. The internal standard was combined with hepatadecanoic acid and tricaprin. The samples that had been extracted by the Folch method were analyzed for their lipid content (GC analysis using a HS-SS-10 columns for fatty acids and an OV-1 column for lipid and cholesterol). A significant positive correlation was noted between the results of dieticians' analysis and those obtained from a gas chromatographic analysis of lipid and cholesterol contents and the P/S ratio, proving that lipid analysis of food by dieticians is highly reliable. Therefore for diseases (such as hyperlipemia, arteriosclerosis, obesity, diabetes mellitus, fatty liver, and pancreatitis) in which dietary factors have a significant effect on their clinical course, dietary instructions on dietary fats based on an analysis by dieticians are considered to be effective.