Chromatographic Trace Research Articles

Preparation of dopamine 3-O-sulphate and dopamine 4-O-sulphate as reference substances and high-performance liquid chromatographic trace determination

Simple syntheses of the biologically important but hitherto difficult to obtain dopamine sulpho conjugates dopamine 3-O-sulphate (I) and dopamine 4-O-sulphate (II), as analytical reference substances, starting from dopamine hydrochloride are described. A method for the determination of I and II with reversed-phase high-performance liquid chromatographic separation and coulometric detection in human urine together with calibration and current-voltage curves are presented. Detection limits of approximately 100 pg of I or II and unequivocal substance identifications even in very complex substrates such as human urine are reported.

Use of backflushing and peak-cutting technique in gas chromatographic trace analysis

A backflusing, peak-cutting method was developed for the analysis of trace components present in the tail of a major component peak. Using a helium-ionization detector, the minimum detectable concentration (MDC) was: oxygen in hydrogen, 0.5ppm; nitrogen in oxygen or argon, 1ppm; and methane and carbon monoxide in nitrogen, 1ppm. The corresponding MDC values for the conventional single-column method were 7.2ppm, 8.3ppm, and 14 and 5ppm, respectively. Equations used to predict the retention time are given. The accuracy of the predicted retention time is about two percent compared to experimental results.

Liquid chromatographic trace enrichment with on‐line capillary gas chromatography for the determination of organic pollutants in aqueous samples

AbstractTrace enrichment for the GC analysis of a series of chlorinated pesticides and polychlorinated biphenyls (PCBs) in aqueous samples has been achieved through a simple on‐line technique involving sorption on an LC micro‐precolumn followed by direct elution into a gas chromatograph with hexane. A 5‐m retention gap coupled to the capillary GC column served as the recipient of a relatively large sample volume (ca. 100 μl) introduced into the GC. Partially concurrent solvent evaporation during sample introduction allowed a large sample capacity. Recoveries of more than 95% were observed for the majority of the compounds studied. Using 1.0 ml aqueous samples, detection limits of less than 1 ppt were found. The applicability of the developed method was demonstrated for a river water sample.

Estimation of Volatile Substances in the Atmosphere of Forest Ecosystems by Gas Chromatography

Abstract Volatiles occurring in the open atmosphere of forested areas can be determined practically only by employing sample enrichment techniques of gas chromatographic trace analysis. A technique was developed of concentrating trace volatiles from large air samples (5–151) on trapping columns packed with Tenax GC, followed by the thermal desorption and gas chromatographic analysis of the concentrate by using a flame ionization detector. A procedure is shown of calculating the masses of the individual components of the concentrate by virtue of the basic properties of the flame ionization detector as a non-ideal coulometer, which makes it possible to estimate reliably the concentrations of the analytes in the air analysed from the parameters of the chromatogram without direct calibration for the components under determination. At the usual concentrations of the analytes in the forest atmosphere, special measures have to be taken in order to protect the samples entrapped in the Tenax column against contami...

Comparison of Cannabis Samples from Different Origins by the Headspace Technique and an Assessment of Chromatographic Traces Using the r-Matrix

Chromatographic patterns from headspace samples of the same cannabis samples and cannabis from different geographic origins have been assessed numerically by means of a retention index matrix ( r-matrix). Replicates from the sample bulk sample gave high superimposability coefficients (0.858 to 0.872) whereas comparison of chromatograms from a bulk sample of Moroccan origin with those from bulk Pakistan cannabis gave superimposability coefficients of 0.58 to 0.64.

Analysis of Amines in the Industrial Environment

Abstract Different methods for gas chromatographic trace analysis of a wide variety of amines are described. Both packed columns and glass capillary columns are used. The advantages of a nitrogen selective detector and a nitrogen-free stationary phase are demonstrated. Special concern is devoted to direct analysis of free amines on packed columns in organic solvents as well as in alkaline aqueous solutions with varying salt concentrations. Determination limits below 0.1 ppm are usually obtained and the precision at the 1 ppm level is generally about 2–3%. A permethylation procedure applicable to aqueous solutions has been developed for polyamines. Air sampling in acidic absorption solutions as well as on a solid adsorbent (Chromosorb 103) combined with thermal desorption is discussed. Applications from various industries and from the building sector are presented.

Pyrolysis-gas chromatography applied to organic geochemistry: Structural similarities between kerogens and asphaltenes from related rock extracts and oils

Previous studies have shown structural similarities between kerogens and asphaltenes from chloroform extracts of the same rocks. Migrated oils contain a small asphaltenes fraction, which obviously must bear a relationship to the asphaltenes remaining in the source rock. In this work, investigations were extended to the joint study of kerogens, asphaltenes remaining in the source rock and asphaltenes from migrated oils. Gas chromatographic traces of total pyrolysates from kerogens, rock-extract asphaltenes and oil asphaltenes show a striking similarity, which indicates a common origin of the major components in the gas chromatographic traces. This simple examination cannot be used for compounds present in small amounts, even if they are especially informative, as with C 25-C 35 polycyclics. These compounds were therefore studied by gas chromatography-mass spectrometry. Some hydrocarbon families were distinguished, viz., tri-, tetra- and pentacyclics, which constitute remnants of biological structures, the so-called biochemical fossils. Their distributions are closely similar. The results indicate a general structural similarity between kerogens and asphaltenes from both source rocks and reservoired oils. The main difference is in the size of the macromolecular units, kerogen units being the largest and most condensed, oil asphaltenes the smallest and least condensed.

Gaschromatographische Untersuchung der Adsorptionseigenschaften von Silicalit und ZSM-5

High silica molecular sieves (silicalite, ZSM-5) were tested as adsorbents for gas chromatographic trace analysis. Therefore the retention behaviour of low-boiling organic compounds (hydrocarbons, halogenated hydrocarbons, amines, alcohols and ethers) on these materials was investigated. The specific retention volumes at different temperatures have been determined and elution orders and peak shapes were studied. The retention data allow a simple calculation of the breakthrough volumes (dynamic adsorption capacity) and the chromatographic characterisation of the adsorbents. Both nitrogen and oxygen containing compounds could not—or at least unreproducibely—be eluated up to 300°. The elution order and the peak shape of compounds with the same number of carbon atoms but different geometric and electronic structure (e.g.n-butenes;n-hexane, cyclohexane, benzene) can be explained by the action of exclusion effects and different diffusion barriers.

Quantitation of l-α-acetylmethadol and its metabolites in human serum by capillary gas—liquid chromatography and nitrogen detection

A procedure is described for the simultaneous measurement of l-α-acetylmethadol and its two pharmacologically active metabolites: noracetylmethadol and dinoracetylmethadol. In the method an intramolecular conversion reaction of the two metabolites to their amide configuration is utilized. The reaction is performed while the metabolites are still in the serum. Following solvent extraction the samples are analyzed by capillary gas—liquid chromatography coupled with nitrogen detection. Quantitation is achieved by internal standardization. The lower limit of sensitivity is 5 ng/ml in serum. Absolute sensitivity is 0.1 ng for all three compounds. The advantages over other procedures are: (1) speed due to the single extraction step; (2) increased recovery of noracetylmethadol and dinoracetylmethadol due to decreased polarity of the amides; (3) greater stability of the metabolites in the amide configuration; (4) better chromatographic quantitation and separation because detector response for the amides is greater than it is for the original configuration of the metabolites and the area of the chromatographic tracing is free of interfering substances.

Procedure for the semi-quantitative analysis of chromatographic traces containing overlapping peaks

A manual calculation procedure is described for estimating the amplitude of individual peaks in chromatographic traces where peak overlap occurs. The method is based on the assumptions that the peaks are Gaussian in shape and are reproducible, that small changes in elution volumes can be accommodated by a simple correction procedure and that individual protein elution curves can be summed to give the observed experimental curve. The reproducibility of peak height estimations for five consecutive repeat chromatographic separations ranged from 1.5% for major components to 15% for minor peaks.

Chromatographic trace analysis of guanidine, substituted guanidines and s-triazines in water

Chromatographic trace analysis of guanidine, substituted guanidines and s-triazines in water

Forms of vitamin B6 in human milk

AbstractA previously developed high performance chromatographic method has been modified slightly and used to determine the forms of vitamin B6 in human milk. The chromatographic traces are free of compounds that would interfere with the two principal forms found, pyridoxal and pyridoxal phosphate. The method is fast and reliable; it yields recoveries of from 90 to 106% for the vitamers and agrees with results obtained on the same samples with the standard microbiological assay.

High-pressure liquid chromatography of petroporhyrins: evaluation as a geochemical fingerprinting method by principal components analysis

High-pressure liquid chromatographic traces of petroporphyrins can be compared on the basis of areas under selected peaks. Principal components analysis of such data obtained from a suite of twelve crude oils (McKittrick Field, California; Tertiary age) shows inter-sample relationships similar to those observed in a multivariate statistical analysis of published hydrocarbon distributions in the oils. Both groups of compounds appear to reflect the operation of processes in the geologic environment which have been inferred elsewhere to be migration and maturation.

A new device for contamination-free injection for gas chromatographic trace estimation of oxygen and nitrogen

The paper presents a new device modifying normal injection port of a gas chromatograph for eliminating air contamination thus enabling determination of traces of oxygen or nitrogen. Further modification is also proposed which enables the analysis to be carried out with a limited quantity of sample gas. Potential application of this device in the analysis of reactive gases like florine has been indicated.

Metal-chelate gas-chromatography for trace element analysis

Abstract

Micro liquid chromatographic trace analysis for insecticide phosphoric esters in body fluids

A Chromatographic method for the direct determination of nonpolar substances in biological fluids is described. For this micro method no sample-preparation steps are necessary. It is possible to determine a pesticide in human serum in the ng/ml concentration range.

B6 vitamer analysis in human plasma by high performance liquid chromatography: a preliminary report

An extraction procedure that can be used successfully with a high performance liquid chromatography sample clean-up and analytical method is outlined for the determination of B6 vitamer and pyridoxic acid concentrations in human plasma. The method is a modification of ones developed for food and animal tissue investigations. Chromatographic traces, relatively clean of interfering compounds are obtained. The method has the advantage of speed and reproducibility and yields recoveries of from 90 to 100% for all vitamers and pyridoxic acid.

Excretion, isolation and structure of a new phenolic constituent of female urine.

The regular occurrence of a peak due to an unidentified substance (X) in the gas chromatographic traces obtained from phenolic extracts of urine from human pregnant and non-pregnant females has been reported. The biphasic excretion of X with maxima in the luteal phase of the ovulatory cycle and relatively high levels in the first trimester of pregnancy were noteworthy and suggested that the substance may have a biological significance. Close similarities between the excretory pattern, the chemical and chromatographic properties of X and of those of the known phenolic steroids suggested initially that this compound was steroidal in nature. The same, or a similar, substance seems to be excreted in the vervet monkey (Cercopithecus aethiops pygerythrus). We now report the excretory pattern of X in more detail, the isolation of the pure compound from pooled pregnancy urine and the chemical structure. The structure determined by mass spectrometry, IR spectroscopy and NMR spectrometry is: trans-(+/-)-3,4-bis[(3-hydroxyphenyl)methyl]dihydro-2-(3H)-furanone (HPMF) and was confirmed by synthesis.

C15+ HYDROCARBONS IN THE SEDIMENTS OF THE NEW YORK BIGHT

ABSTRACT The purpose of this study was to document the distribution and abundance of C 15+ hydrocarbons in sediment samples taken from the Hudson River, the New York Harbor, and across the continental shelf to the continental rise. Collection of 35 of these samples took place in 1975–76 using a multiple corer, a bottom grab, or the submersible Alvin. Materials obtained from these areas were considered representative and included dredge spoils, sewage sludge, and sediment from both the Deepwater Dumpsite 106 on the continental rise and the comparatively cleaner sea floor of the continental shelf beyond the apex of the New York Bight. Total C15+ hydrocarbons are most abundant (3000–6000 parts per million) in areas highly impacted by man—harbor sediments and dredge spoil and sewage sludge disposal areas. Values from the continental shelf are lower (80 ppm) and values from the continental rise are the lowest (40 ppm). Gas chromatographic traces clearly distinguish the hydrocarbons in the dredge spoil and sewage sludge sediment samples from the hydrocarbons found in sediment samples relatively free of sludge or spoil materials.

High-performance liquid chromatographic separation and trace determination of the antitumour derivatives of ellipticine and related quaternary ammonium compounds

High-performance liquid chromatographic separation and trace determination of the antitumour derivatives of ellipticine and related quaternary ammonium compounds