Study of the gas chromatographic behavior of selected alcohols and amines

The gas chromatographic behavior of selected linear and non-linear alcohols and amines was investigated using four capillary columns containing phenyl substitution levels of 0%, 5%, and 50% and 50% cyanopropyl substitution. In a previous study, the positions of specific compounds inside the capillary column were iteratively modeled using only two thermodynamic parameters (ΔH and ΔS). The present study addresses the validation of the two-parameter model for retention time prediction for selected alcohols and amines using thermodynamic data obtained from as few as two data points. The difference between predicted and observed retention times under different temperature conditions was generally less than 1% of the experimental value and the predicted order of elution was correct in the used model.     

Influence of the solvent on the gas chromatographic behaviour of urea herbicides

Summary Degradation products of chlorsulfuron, chlortoluron, diuron, fluometuron, isoproturon, linuron, metabenzthiazuron, metobromuron, and monuron formed in the gas chromatographic injector have been used for identification of the respective herbicides. Mass spectra of the derived compounds were obtained with a quadrupole mass spectrometric detector working in scan mode (20–450 amu). The compounds generated often depended on the solvent used for phenylurea herbicide injection (ethanol, methanol, dichloromethane, and acetonitrile). When methanol and ethanol were used as solvents the major products formed from phenylureas were carbamic acid esters. When acetonitrile or dichloromethane were used the main derivatives were phenylisocyanates. Chlorsulfuron and metabenzthiazuron, however, generated a triazine plus a phenylsulfonamide and a benzothiazolamine, respectively, irrespective of the solvent used. Linuron and diuron behaved similarly and gave degradation products with the same mass spectra. The thermal reactions occurred instantaneously in the injector block and were promoted by the high temperature selected (300°C). Detemination of the compounds derived from urea herbicides, by use of a 30 m BP10 column and a selected ion registering (SIR) program based on two or three ions, can be used for sensitive detection of the presence of urea herbicides in environmental extracts. With standards in methanol instrument detection limits ranged from 0.1 pg for chlorsulfuron (detected as 2-chlorobenzensulfonamide) to 1 pg for monuron and metobromuron (both detected as their carbamic acid methyl esters).RSD were below 9% at the 5 ng L⁻¹ level. The response was linearly dependent on quantily (r>0.9986) in the 5 ng L⁻¹ to 25 μg L⁻¹ range. Unequivocal identification of some phenylurea herbicides was not always possible because some herbicides with similar structures, for example diuron and linuron, gave the same derivative.     

Derivatization of amines with chloroformate esters for gas chromatographic analysis

Summary The gas chromatographic analysis of amines after conversion to electron capture sensitive carbamates in two-phase systems has been studied. Hydrophilic compounds, for instance methylamine, are reacted with 2,2,2-trichloro-tert. butyl chloroformate. Quantitation below 10^–7 M can be made by thermionic or electron capture detection. A hydrophobic amine, namely N,N-dimethyl-n-octylamine, was derivatized with 2,4,6-tribromophenyl chloroformate with addition of iodide ion to the aqueous phase. The favorable effect of iodide ion as well as the choice of pH and chloroformate ester is discussed.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Quantitative analysis of some preservatives in pharmaceutical formulations by different chromatographic methods

Different chromatographic methods for determination of methyl hydroxybenzoate and propyl hydroxybenzoate in pharmaceutical formulations are compared. Procedures for HPTLC, HPLC and GC/MS are given.     

Effect of some parameters on the liquid chromatographic separation of biogenic amines and their metabolites

The liquid chromatographic separation of some biogenic amines and their metabolites with a reversed-phase ion-pair system has been optimized. The effects of the nature of the stationary phase, the column temperature, the pH, and the ion-pair reagent concentration of the mobile phase have been investigated. The most striking result is the influence of the column temperature on selectivity.     

Derivatization of aromatic amines with bromine for improved gas chromatographic determination

Summary For improved determination of aromatic amines by gas chromatography and detection with an electron capture detector (GC-ECD) a derivatization method based on the bromination of the aromatic ring in an acetic acid medium was developed. In general, all free ortho and para-positions relative to the amino group undergo electrophilic substitution. Separation of at least 30 compounds in a single chromatographic run in 30 min is possible. With this method, 56 aromatic amines were studied and only in 6 cases were no derivatives obtained. Quantitation limits determined from calibration data are 1.2–40 μg L⁻¹ for a 100 mL sample and an injection volume of 1 μL. Previous experiments suggest that both sample and injection volume may be increased to lower the quantitation limit.     

Improvements in the gas chromatographic determination of trace amounts of aliphatic amines in aqueous solution

The analysis of aliphatic amines at the parts per million level in aqueous solution has been improved with respect to a previously reported chromatographic method which made use of Carbopack B modified with 0.8% potassium hydroxide and 4% PEG 20M by altering these concentrations to 0.3% and 4.8%, respectively, by using a modified coating procedure. By this means, difficulties in duplicating from batch to batch the chromatographic characteristics of the column packing have been eliminated, and the instability of the retention times of amines on prolonged use of the column, the intolerance of the packing to injections of water and overlapping of tailed peaks for alcohols with the amine peaks no longer affect the trace determination of amines.     

Gas chromatography in qualitative analyses. An investigation of the oxidation of some silicones used as gas chromatographic stationary phases

Summary The on-column oxidation of apolar and polar silicones used as gas chromatographic stationary phases is investigated. Even at 225° the effects of oxidation are found to be slight. Of the materials investigated the methylphenylsilicones are the most stable.     

Multidimensional gas chromatographic separation of selected PCB atropisomers in technical formulations and sediments

A simple dual-column gas chromatographic system with a six-port switching valve has been used to separate the atropisomers of PCB congeners 84, 91, and 95 in technical PCB formulations and in extracts of soil and river sediment. A capillary column coated with a methylphenylsiloxane stationary phase (CP-Sil 8) was used as the first column, for retention window selection, and a permethylated β-cyclodextrin (ChirasilDex) capillary column as the main separation column. Because peak overlap could not be eliminated by optimization of column temperature, the enantiomeric ratios of PCB congeners could not be determined from the original chromatograms. The correct enantiomer ratio was determined from the peak areas obtained by deconvolution of the chromatograms. Whereas the PCB atropisomers considered were present in equal concentrations in the technical PCB formulations, analysis of a river sediment sample confirmed different residual concentrations of the atropisomers of congener 95.     

Evaluation of stationary phases and gas chromatographic detectors for determination of amines in water

For the first time, a systematic overview deals with the advantages and disadvantages of several stationary phases (polar and non‐polar) and gas chromatographic detectors (flame ionization detector, nitrogen–phosphorus detector and MS) for the determination of 27 amines (aliphatic and aromatic amines and N‐nitrosamines) in water samples. To increase sensitivity (250 mL of sample was eluted with 150 μL of solvent) and matrix elimination, an automatic SPE system was employed prior to GC determination. The best results in terms of resolution and retention times were achieved using a column coated with 5% phenyl‐dimethylpolysiloxane (DB‐5). Capacity factor (k) values for the 27 amines increased with the rise in the polarity of the stationary phase, ranging from 3.0–27.7 and 2.2–14.4 for polar (polyethylene glycol) and non‐polar (DB‐5) columns, respectively. The detection limits of the method were 0.9–9 μg/L for flame ionization detector, 8–95 ng/L for nitrogen–phosphorus detector and 0.2–6.3 ng/L for MS. The precision was similar for the three detectors (RSD, 3.7–6.0%). The GC‐MS method was applied with a high degree of accuracy and precision to determine amines in real samples including tap, river, pond, well, swimming pool and wastewaters.     

Development and evaluation of gas and liquid chromatographic methods for the analysis of fatty amines

In contrast to the plethora of publications on the separation of fatty acids, analogous studies involving fatty amines are scarce. A recently introduced ionic‐liquid‐based capillary column for GC was used to separate trifluoroacetylated fatty amines focusing on the analysis of a commercial sample. Using the ionic liquid column (isothermal mode at 200°C) it was possible to separate linear primary fatty amines from C₁₂ to C₂₂ chain length in less 25 min with MS identification. The log of the amine retention factors are linearly related to the alkyl chain length with a methylene selectivity of 0.117 kcal/mol for the saturated amines and 0.128 kcal/mol for the mono‐unsaturated amines. The sp² selectivity for unsaturated fatty amines also could be calculated as 0.107 kcal/mol for the ionic liquid column. The commercial sample was quantified by GC with flame ionization detection (FID). An LC method also was developed with a reversed phase gradient separation using acetonitrile/formate buffer mobile phases and ESI‐MS detection. Native amines could be detected and identified by their single ion monitoring chromatograms even when partial coelution was observed. The analysis of the commercial sample returned results coherent with those obtained by GC–FID and with the manufacturer's data.