A. Zlatkis

Concentration and analysis of trace volatile organics in gases and biological fluids with a new solid adsorbent

SummaryA new procedure for sampling, transfer, and analysis of volatile organic compounds by gas chromatography has been developed. An adsorbent trap ultimately becomes an insert for a modified injector port, and a valve system allows the sample to be transferred to a cooled precolumn and finally to the separating column. Several traps may be used for sampling (for multiple injections), and it has been established that such traps may be stored without loss of sample. The ease and reproducibility of this procedure is amenable for the investigation of volatile organic compounds involving air and water pollution, flavor, and aroma analyses, and body fluid metabolites.

Temperature and pressure effects in supercritical-fluid chromatography

Abstract In the search for a suitable programming technique, the effects of pressure and temperature in superficial-fluid chromatography were studied. Both pressure and inverse temperature programming can be used to influence the retention characteristics. The selectivity of separation can further be controlled by a “moderator”. Values of height equivalent to a theoretical plate for model compounds were measured within a wide range of operating conditions and correlated with pressure drop measurements. The results suggest that a compromise between the particle size and pressure drop is necessary.

Collection and analysis of trace organic emissions from natural sources

Abstract A study was undertaken to develop practical techniques for measurement of hydrocarbons and oxygenated volatiles in rural areas. A limited number of rural and urban samples were taken to demonstrate the general applicability of the method. Sampling locations were selected in a large forest at a distance of about 35 miles from a heavily populated area. It turned out that this distance was not sufficient to escape the urban influence and compounds typical of urban activities were found at dilute concentrations. The sampling method is based on adsorption of the trace organics on suitable adsorbents with subsequent thermal elution. Besides Tenax GC and Carbopack BHT the use of a new carbonaceous adsorbent, Ambersorb XE-340 (Rohm and Haas, Philadelphia, Pa., U.S.A.), was investigated. In preliminary experiments, this material had shown very good adsorption properties for low molecular weight compounds. The analysis of the volatile compounds was performed by gas chromatography-mass spectrometry with both metal and glass capillary columns. It was found that olefins, terpenes and other thermally labile compounds adsorbed on such materials were not altered even when stored over long periods of time. In general, the amount of volatiles found in rural air were 10–500 times lower than the corresponding levels in urban atmospheres, the lowest levels being found during the winter season. Semiquantitative data were obtained for some major compounds from rural areas. The level of organics strongly depends on season and meteorological conditions. Characteristic substances indigenous to plant life have been identified. Besides terpenes, a number of lower alcohols and esters have been found. Preliminary data are presented for a limited number of samples. Further studies are necessary to characterize and quantitate completely natural organic emissions.

Cyclic derivatives for the selective chromatographic analysis of bifunctional compounds

Abstract Only a few reagents capable of forming cyclic derivatives with bifunctional compounds have been described in the chromatographic literature. Some reagents are selective for a particular compound, whereas others such as the boronic acids are more generally applicable to a wide range of bifunctional compounds. All reagents provide a high degree of selectivity through the chemical discriminatory power of the reaction employed and some reagents have been developed which have high detector discriminatory power as well. These are of particular interest for the analysis of a few components (bifunctional compounds) in a complex matrix without the need for a tedious amount of sample clean-up. When it is necessary to isolate bifunctional compounds from complex sources, columns containing immobilized boronic acid groups have been used and advantage taken of the reversibility of the boronate complexation reaction for attachment and later removal of the desired bifunctional compound.

Profiles of volatile metabolites in body fluids

Abstract A method for the analysis of volatile metabolites present in plasma, urine, breast milk and amniotic fluid collected from mother-infant pairs has been developed which requires only 100 μl of plasma, 3 ml of urine, 20 μl of breast milk and 500 μl of amniotic fluid. After extraction with diethyl ether, the volatile compounds were adsorbed on glass wool in a special concentration tube and subsequently desorbed and transferred to a 100-m nickel capillary column for analysis by gas chromatography and gas chromatography-mass spectrometry. The separations, carried out by temperature programming, were complete in 90 min.

Preparation of high resolution nickel open tubular columns

SummaryA detailed description of the production of nickel open tubular columns is given and the important steps are discussed. Two types of surface modification, etching and introduction of a suspended silanized silica, which result in conventional open tubular (COT) and in support coated open tubular (SCOT) columns are described. Properties of these columns are presented for one phase, Emulphor ON 870 and several examples of applications are given.

Simultaneous gas chromatography of volatile and non-volatile carboxylic acids as tert.-Butyldimethylsilyl derivatives

Abstract Solid phase extraction with subsequent ion pair formation and silylation was investigated for the simultaneous trace enrichment of volatile and non-volatile carboxylic acids from complex aqueous samples. The solid phase extraction of acids was performed using Chromosorb P as the solid sorbent. The ether eluate was treated with triethylamine. The resulting triethylammonium salts of the acids were converted to stable tert.-butyldimethylsilyl (TBDMS) derivatives, which were analyzed by gas chromatography (GC) and GC-mass spectrometry. The characteristic M - 57 ions in the mass spectra of TBDMS derivatives enabled rapid identification of acids. The application of the method to the organic acid profiling of urine and saliva samples is demonstrated.

Concentration and anlalysis of organic volatiles in skylab 4

Abstract The volatile components in the cabin atomosphere of Skylab 4 at various times during the mission were concentrated and analysed. More than 300 compounds could be detected by high-resolution gas chromatography with differences in concentration of as much as six orders of magnitude. 107 substances were identified by mass spectromety, covering a molecular-weight range of approximately 60 to more than 500. The concetration of 80 compounds were determined for three samples taken on days 11·47 and 77 of the mission. The compositionof the volatiles in the spacecrafts atmosphere differs significantly from other environments. A wide variety of various silicon compounds, mostly methylated siloxanes of molecular weight up to 584, was detected. Fluorocarbons (Freons) were also present.

Analysis of trace volatile metabolites in serum and plasma

Abstract A method is described for analyzing volatile constituents in 5- to 10-ml samples of human serum and plasma. A headspace sampling technique was employed by which volatile sample constituents are carried in a stream of ultra-pure nitrogen and adsorbed onto a porous polymer with subsequent heat desorption. The concentrated volatiles were separated on highly efficient capillary columns. Mass spectrometric identifications were made with 55 ml of serum. Characteristic components in normal serum are: ethanol, 4-methyl-2-pentanone, hexanal, 1-butanol, 2-hexanol, 2-heptanone, and benzaldehyde.

High-performance thin-layer chromatographic determination of psychopharmacologic agents in blood serum.

High-performance thin-layer chromatography affords a rapid, sensitive method for determination of psychopharmacologic agents in blood serum samples. Quantitation of the representative drugs chlorpromazine, amitriptyline, nortriptyline, imipramine, and desipramine at levels as low as 5 ng/ml is demonstrated by scanning the developed thin-layer plates with a chromatographic spectrophotometer in the ultraviolet absorption mode. Neither derivatization prior to, nor color development after chromatographic separation is required to achieve sensitivity and reproducibility of determinations.