Gas Chromatographic Behaviour Research Articles

Gas chromatographic, spectrophotometric and electrochemical behavior of substituted s-triazines

The behaviour of 18 s-triazine herbicides was studied gas chromatographically, spectrophotometriclly and electrochemically. The retention indices were measured on three stationary phases, Carbowax 20M, Versamid 900 and an SE-30 + Reoplex 400 mixed phase, and the effect of the substituents in the 2-, 4- and 6-positions on the retention data is discussed. The differences in the retention indices on two phases Δ I, were correlated with the basicities and the dipole moments of the substances studied. The UV spectra of the s-trazines were measured in methanol. A study of the anodic electrochemical behaviour of these substances was carried out in anhydrous acetonitrile. The E 1/2 values obtained indicated that the substances strongly resisted oxidation and the results are discussed together with the gas chromatographic and spectrophotometric data in relation to the structures of the s-triazines.

Volatility studies of metal chelates. III. Thermal and gas chromatographic properties of the volatile copper(II) and nickel(II) chelates of the isomeric tetradentate β-keto enamines formed in the reaction of 1,1,1-Trifluoro-5,5-dimethylhexane-2,4-dione with Ethane-1,2-diamine

The Schiff base, 6,6,6,6',6',6'-hexafluoro-2,2,2',2'-tetramethyl-5,5'-(ethane-1,2-diyldiimino)bis(hex-4-en-3-one), as normally prepared by the condensation of 1,1,1-trifluoro-5,5-dimethylhexane-2,4-dioneand ethane-1,2-diamine is only one of two isomeric forms which give distinct isomers with copper(II)and nickel(II), readily separated on columns of silica gel. The isomeric chelates have large volatility differences and display greater volatility than other tetradentate β- keto enamine complexes. The excellent gas chromatographic behaviour of the chelates leads to detection limits of about 2 picograms metal with the electron-capture detector.

Conversion of Cobalt(II) and Nickel(II) Fixed on the Ion Exchange Resin into Their Trifluoroacetylacetonates and Gas Chromatography of the Chelates

Abstract The conversion of cobalt(II) and nickel(II) ions collected on the ion exchange resin into the chelate compounds with trifluoroacetylacetone (Htfa) has been studied in various solvents. In the presence of pyridine, cobalt and nickel ions were quantitatively extracted from the resin into organic phase in the form of the base adducts [Co(tfa)2(py)2] and [Ni(tfa)2(py)2], respectively. The thermogravimetric and gas chromatographic behaviors of these compounds have been investigated. A gas chromatographic separation of [Ni(tfa)2] from [Co(tfa)2] was successfully performed.

Zusammenhänge zwischen der struktur pflanzlicher sterine und ihrem gaschromatographischen verhalten auf verschiedenen stationären phasen

Relationship between the structure of plant sterols and their retention behaviour in gas chromatography on several stationary phases The relative retention times of 49 plant sterols were determined as their trimethylsilyl ethers on 8 different stationary phases. Separation characteristics are derived from the gas chromatographic behaviour of the different types of double bonds and other structural specificities. Proper choice of a stationary phase for optimal separation of critical pairs is facilitated by the separation factors.

The preparation, gas liquid chromatography, and some physical and chemical properties of certain higher aliphatic 2,4-diketones--a new lipid class.

Fourteen saturated aliphatic 2,4-diketones, ranging in chain length from C7 to C25, and one unsaturated compound, delta12-2,4-heneicosenedione, were prepared by Claisen acylations of the appropriate methyl ketones, and their gas chromatographic behavior was studied. Mixtures of these diketones were resolved on columns containing UCW98 or Carbowax 20M stationary phases. Their methoxime and 2,4-dinitrophenylsemicarbazone derivatives were resolved on OV-17 and OV-1 stationary phases, respectively. Since higher homologous aliphatic 2,4-diketones have been found in mammalian tissues, they constitute a new lipid class.

Capillary gas chromatography of alkylbenzenes : II. Correlations between the structures and methylene group increments and differences in retention indices of isomers

The contribution to gas chromatographic retention behaviour of methylene group increments and differences in the retention indices (δ I) of isomers of alkylbenzenes up to C 16 on squalane and acetyltri- n-butyl citrate was studied. The methylene group increments appear to vary over a wide range (60–100 i.u.) and depend on the magnitude, positions and relative lengths of the alkyl chains and on the number of carbon atoms. Anomalous retention behaviour of n-propylbenzene and its derivatives, except for molecules in which there are alkyl groups in both positions vicinal to the n-propyl group, was found. Hence, the correlations of I CH 2 in homologous series can serve as indicators of fine structural peculiarities of the molecules. The applicability of regularities in methylene group increments and δ I values, based on precise measurements of retention indices of low-molecular-weight alkylbenzenes, for confirmation of the identities of high-molecular-weight alkylbenzenes ( > C 10) is demonstrated.

Comparison of chemically bonded and physically coated polyethylene glycol stationary phases in gas chromatography

Studies of the gas chromatographic behaviour of bonded and coated PEG 20M stationary phases showed that bonded PEG 20M has a liquid-type structure above room temperature. Retention diagrams for several solute molecules in the form of ln V r versus the reciprocal of the absolute temperature show clear differences between bonded and coated PEG 20M on Chromosorb W. The absence of an inflection in the retention diagrams for bonded PEG 20M is observed, in contrast to the marked change in retention volumes for coated PEG 20M at or near the melting points. Both bonded and coated PEG 20M have almost identical enthalpies above the melting point of coated PEG 20M and the same holds for bonded PEG 20M at .80 °C and 35 °C. Peak asymmetry was calculated and marked differences between bonded and coated PEG 20M stationary phases were observed.

Gas chromatographic behaviour of some polynuclear hydrocarbons on cadmium chloride columns modified with carbowaxes

The retention behaviour of some polynuclear hydrocarbons on cadmium chloride columns modified with Carbowaxes was studied and was found to be independent of the chain length of the glycol. This behaviour was not observed with other metal salts and liquid stationary phases. The sharp maxima in the absolute retention of phenanthrene and anthracene at a 4% salt coating level are surprising. Polynuclear hydrocarbons show both positive and negative retardation. Electron repulsion and slow interfacial mass transport in the micropores dictate the retention behaviour of the stationary phase.

Synthesis and spectroscopic and gas chromatographic behavior of isomeric chlorinated terphenyls.

Synthesis and spectroscopic and gas chromatographic behavior of isomeric chlorinated terphenyls.

Comparative gas chromatographic behaviour and detection limits of 2,6-di- tert.-butyl-4-methylphenol, 3- tert.-butyl-4-hydroxyanisole (BHA), and the trifluoroacetate of BHA

Comparative gas chromatographic behaviour and detection limits of 2,6-di- tert.-butyl-4-methylphenol, 3- tert.-butyl-4-hydroxyanisole (BHA), and the trifluoroacetate of BHA

Radio-gas-chromatographic investigation of sotope exchange reactions between inorganic halides

Gas-chromatographic behavior of halides of arsenic and phosphorus and isotope exchange reactions among these species were investigated by means of radiotracer techniques. The halides studied in the present work include AsCl3, AsBr3, PBr3,76AsBr3,76AsCl3, and As82Br3. It was demonstrated that the rapid isotope exchange of arsenic and bromine took place in the binary systems: AsBr3−AsCl3 and AsBr3−PBr3, in the course of the gas-chromatographic separation process.

Capillary gas chromatography of C6−C14 n-alkenes on polyphenyl ether and polyethylene glycol 4000

The retention indices (I) and their structural increments (σl/°C, H, Δl) of C6−C14 n-alkenes on polyphenyl ether (PFE) and C12−C14 n-alkenes on polyethylene glycol 4000 (PEG) at 20–160 °C have been determined and correlated with the molecular structure of the isomers. A number of common regularities in gas chromatographic behaviour on these liquid phases and squalane (SQ) [1–3] have been found. On PFE the elution order of isomeric n-alkenes is similar to that on SQ (except C8−C10 1-alkenes and cis-4-tetradecene), for pairs with cis- and trans-configuration it depends on the column temperature, position of double bond and the number of carbon atoms (n) in the molecule. On PEG the cis- are always retained longer than the corresponding trans-alkenes. The linear relationships between 1 and n on PFE and PEG are given in equation form.

The correlation between the physical properties and structure of alcohols and their gas chromatographic behaviour on polar and non-polar stationary phases : I. C1-C8 straight-chain alcohols

Primary and secondary straight-chain alcohols with one to eight carbon atoms have been analysed by gas chromatography at 100° on 3-m columns packed with 20% of squalane and Carbowax 400, 1000 and 20M, on chlorodimethylsilane-treated Chromosorb W (60–80 mesh), using thermal-conductivity and flame-ionization detectors. The specific retention volumes, Vg, and the retention indices relative to normal alcohols, have been determined for all of the compounds, and the effects of the positions of the hydroxyl groups have been investigated. Boiling points, vapour pressures and molecular volumes have been correlated with the measured retention values. The activity coefficients at infinite dilution and the normalized activity coefficients have been calculated, and their influence on the separation is discussed.

Identification and synthesis of the female sex pheromone of the citrus flower moth, Prays citri

The female sex pheromone of the citrus flower moth, Prays citri, has been identified as (Z)-7- tetradecenal . The unusually small amounts of pheromone which could be extracted from the female moth precluded identification by classical methods. Instead, the basic structure of the pheromone was deduced from its gas chromatographic (GC) behaviour using a male moth prepared for electroantennographic (EAG) recording as detector; double bond position and geometry were determined by high resolution GC of the natural pheromone and a range of tetradecenal isomers, and by recording male moth EAG responses to these isomers. Synthetic (Z)-7- tetradecenal was shown to be highly attractive to male Prays citri when tested in citrus groves in Israel. This is the first reported identification of the female sex pheromone of a member of the Yponomeutidae.

Gas chromatography of some oxovanadium(IV) tetradentate β-ketoamine chelates

The gas chromatographic elution behaviour is reported, for the first time, for the oxovanadium(IV) chelates of seven tetradentate β-ketoamines on a non-polar column. Interaction with Chromosorb W as support is shown to be appreciably greater than with Chromosorb 750. Detection limits using the Chromosorb 750 support and flame ionization detection are less than nanogram amounts of elemental vanadium. The separation of copper and nickel from vanadium complexes is demonstrated.

Gas chromatography of some beryllium oxycarboxylates

Beryllium oxyacetate, oxypropionate, oxyisobutyrate and oxypivalate have been prepared and their thermogravimetric, mass spectroscopic and gas chromatographic behaviour investigated. Previous adsorption difficulties in the gas chromatographic elution of the oxyacetate and oxypropionate have been overcome by using exhaustively silanized solid supports.

Gas chromatographic analysis of dialkylbarbituric acids

A variety of procedures for the derivatization of barbituric acids for gas-liquid chromatography (GLC) are described and a convenient procedure for n-alkylation of barbiturates is reported. The gas chromatographic behaviour of derivatives (methyl, ethyl, propyl, butyl, pentyl and hexyl) is discussed on the basis of the retention index. For the identification and quantitation of 23 barbiturates in biological fluids, use of the propyl derivatives allows a clear gas chromatogram to be obtained by using only one stationary phase. Alkylation with n-alkylating reagents gives only the N,N′-derivative, as confirmed by nuclear magnetic resonance (NMR) and infrared spectroscopy and gas chromatography-mass spectrometry (GC-MS). The fragmentation pattern by electron-impact mass spectrometry is discussed. Alkylation with branched alkylating reagents gives up to three peaks, the major peak being the N,N′-derivative; the other peaks identified by NMR and GC, correspond to the isomeric N,O-derivatives.

Gas chromatography of ternary complexes of manganese(II), iron(II), cobalt(II) and nickel(II) with hexafluoroacetylacetone and DI-n-butylsulphoxide

The gas Chromatographic behaviour of the ternary complexes of selected bivalent first-row transition metal ions with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione H(HFA), and di-n-butylsulphoxide, DBSO, was studied. Calibration plots of peak area vs. amount of metal injected were linear over a range of 60-900 ng for manganese(II), iron(II), cobalt(II) and nickel(II). The average relative standard deviation was less than 3.0% for all the metals studied. Detection limits of 60, 109, 112 and 115ng for cobalt(II), nickel(II), iron(II) and manganese(II), respectively, were obtained with flame-ionization detection. Various liquid phases, including OV-1, SE-30, and Dexsil 300 were used. The best results were obtained on columns of 5% Dexsil 300. No appreciable thermal decomposition was observed on stainless-steel or glass columns, but the best formed peaks were obtained on all-glass columns. The elution of the metallic species was confirmed by venting the exit gases from the gas chromatograph directly into an atomic-absorption spectrophotometer.

Capillary gas chromatography of hypnotics, methyprylon (noludarR) and pyrithyldion (persedonR), after derivatization in an all glass solid injector

The possibility of forming silyl derivatives of methyprylon and pyrithyldion following an alternative and time-saving procedure is discussed. The derivatives are formed on the needle tip of an all glass solid injector. The linearity and reproduciblity of their gas chromatographic behaviour on a capillary column is tested over a concentration range of 0.5 μg −2.5 μg.

The synthesis and gas chromatographic properties of bromobiphenyls

Bromobiphenyls constitute a group of chemicals used extensively as flame retardants in textiles, etc., the environmental fate of which is not known. For a thorough insight into the chemistry, analysis and toxicological and biological effects access to pure bromobiphenyl isomers will be of great value. Literature on bromobiphenyl syntheses have therefore been compiled and, in addition, a number of new compounds have been prepared and characterised. The gas chromatographic behaviour of bromobiphenyls is also described.