Gas chromatographic retention indices of fentanyl and analogues

Narcotic analgesics of the fentanyl class are characterized by high potency and relatively short duration of action. These compounds nowadays have become a substitute for heroine and are highly addictive for abusers. Herein, we report retention indices of fentanyl and its eighteen analogues relative to the homologous n-alkane series. These values are determined on a moderately polar BP-5 capillary column under programmed temperature and isothermal chromatographic conditions. The analogues differ in the substituent attached to the piperidine ring nitrogen, and retention indices are found to vary according to the nature of the substituent. The effects of chromatographic conditions like temperature programming rate, carrier gas flow rate, and oven temperature are studied. Retention indices are also determined on a non-polar BP-1 column to study the influence of stationary phase polarity. Standard deviation of all the RI values is less than one index unit.     

Gas chromatographic retention indices of trimethylsilyl derivatives of terpene alcohols

This paper presents the experimentally determined retention indices (RI(TMS)) for a set of 75 silylated terpenols (33 monoterpenols and 42 sesquiterpenols). The attempt was made to assess the dependence of RI(TMS) on RI (for non-silylated terpenols) and on RI(Ac) (for acetylated terpenols). Satisfactory linear regression parameters (RI(TMS)=b(0)+b(1)RI) were observed for tertiary substituted monoterpenols and primary or secondary substituted sesquiterpenols. The mass spectra of silylated terpenols that were not found in the available literature are in Supplementary information.     

Gas chromatographic retention indices of biologically and environmentally important organic compounds on capillary columns with low-polar stationary phases

This work presents linear temperature programmed retention indices on the columns with stationary phases of 5% phenylpolydimethyl silicone of 389 organic compounds, including extractive substances of plant tissues and environmentally important compounds. Certain factors which influence the values and reproducibility of retention indices during gas chromatographic analysis of multicomponent mixtures are discussed.     

A new gas chromatographic retention index for pesticides and related compounds

A new gas chromatographic (GC) retention index based on a homologous series of tri-n-alkylamines is proposed for use in the detection of pesticides and related compounds because the standard n-paraffin hydrocarbons used for the Kovats index do not show up well on the nitrogen-phosphorus detectors commonly used in pesticide analysis. Using fused silica bonded phase capillary columns (DB-1 or DB-5), the trialkylamine indices of 106 selected pesticides and related compounds were measured and their relationship to the Kovats index determined.     

Gas chromatographic retention indices for alkenes on OV-101 and squalane capillary columns

Summary Gas chromatographic retention indices for 47 C₅ to C₈ alkenes on OV-101 dimethylsilicone at 50 and 70 °C were determined within a standard deviation of 0.3i.u. Data obtained on OV-101 are compared with those measured on squalane. The comparison of the retention index and dl/dT values from both columns is presented as linear regression equations with correlation coefficients greater than 0.98.     

Anomalous temperature dependence of gas chromatographic retention indices of polar compounds on nonpolar phases

The character of the temperature dependences of the retention indices RI(Т) of polar sorbates on nonpolar stationary phases was found to depend on the dosed amounts of sorbates, but not on column overloading. A physicochemical model was suggested to explain the observed anomalies in RI(Т).     

Gas chromatographic separation of the enantiomers of flumecinol and some related compounds

Flumecinol and related compounds can, without derivatization, be separated into their enantiomers by gas chromatography on cyclodextrin phases; permethylated β-cyclodextrin dissolved in OV-1701 can be particularly recommended. Thermodynamic data describing the different intensities of interaction of the individual enantiomers with the stationary phases were determined. The values measured imply different separation mechanisms for the compounds investigated.     

Gas chromatographic determination of vapour pressure and related thermodynamic properties of monoterpenes and biogenically related compounds

The (subcooled) liquid vapour pressure, heat of vapourization and gas-liquid heat capacity difference of monoterpenes and biogenically related compounds were determined by a gas-liquid chromatographic method based on Kovats retention indices. Compared to those used in previous studies using the same method, these compounds are structurally diverse and have relatively low boiling points. Despite of this and even though the difference in activity coefficients in the chromatographic column stationary phase between the test and reference compounds were ignored, results for vapour pressure compare favorably with experimental literature data. The results indicate that the method can be improved by introducing temperature dependent activity coefficients, preferably based on a physicochemical model for gas-liquid partitioning.     

Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns

Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds.The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented.As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.     

Gas chromatographic retention data of wax esters

Higher wax esters within the range of C24 to C44 (205 standards) were analyzed by means of gas chromatography and Kováts indexes (I) and reduced Kováts indexes (RKI) were calculated. The dependences of these retention data on number of carbon atoms and on number and position of double bonds in acid and in alcohol moieties of esters were plotted.     

Gas chromatographic system for the identification of halogenated pesticides by retention indices using n-alkanes as standards

A gas chromatographic system for the evaluation of linear temperature-programmed retention indices allowing n-alkanes to be adopted as the reference retention markers for any type of analyte, irrespective of the atoms present in their molecules, is described. It is based on the simultaneous use of two different detectors (a flame ionization detector and a specific detector suitable for the sample components), both connected (in parallel) to the same column outlet. The performance of this system has been tested by measuring the retention indices of fifteen chlorinated pesticides under conditions of linear programming temperature, by adopting an electron-capture detector as the specific detector. The reliability of the retention indices thus determined has been proven by verifying that they can be reproduced under different chromatographic conditions.     

Relationship between kováts retention indices and molecular connectivity indices of tetralones, coumarins and structurally related compounds

A study was undertaken to test the ability of several molecular connectivity indices to predict the retention indices (I) of tetralones, coumarins and structurally related compounds determined on OV-17 and Apiezon L as stationary phases. The regression analyses with I_OV-17 showed that a two-variable linear regression equation with ²χ and ⁴χ^v_pc gives the best correlation coefficient, suggesting that retention depends basically on branching and the presence and number of adjacent atoms, and secondarily on unsaturations and the number and orientation of substituents. I_ApL gives the best correlation with a two-variable linear regression equation with ¹χ and ³χ^v_p indicating that on this stationary phase retention depends basically on the presence and number of adjacent atoms, and secondarily on unsaturation, branching of adjacent atoms and the presence of heteroaroms. ΔI (ΔI = I_OV-17 - I_ApL), according to the different polarities of both phases, considered to be a measure of the polar forces in retention, does not give a good correlation.     

Gas chromatographic retention indices for C6 alkanols on OV-101 and Carbowax 20M capillary columns

Summary Gas chromatographic retention indices for 16 C₆ alkanols measured on capillary columns coated with OV-101 methylsilicone and Carbowax 20M propylethyleneglycol liquid phases at 80° and 90°C were determined. The respective standard deviation values were 0.5 and 0.8 i.u. The correlation between the retention indices measured on non-polar and polar stationary phases and the boiling points of the alkanols was studied.     

Calculation of gas chromatographic retention indices of organic compounds from the boiling points of their structural analogs

The possibility of calculating gas chromatographic retention indices (1) is discussed. The indices are important parameters for chromatospectral identification of organic compounds from the boiling points of their structural analogs (T _b ^* ) using the linear logarithmic equation log I = a log T _b ^* + bA + c, where A are the structural parameters reflecting the one- to- one position of the compounds being compared in the corresponding taxonomic groups, including homologous series.