Biomedical subjects

I Smetena

Publications and source records attributed to I Smetena.

5 recordsLinked to original sources

PubMed2002

Determination of tobacco alkaloids by gas chromatography with nitrogen-phosphorus detection.

An improved method, gas chromatography (GC) with nitrogen-phosphorus detection (NPD), has been used for determination of alkaloids in green and cured tobacco. Tobacco alkaloids of interest included nicotine, nornicotine, myosmine, anabasine, and anatabine. Tobacco samples were treated with a small quantity of aqueous ammonia solution to "loosen" tobacco tissue and to adjust pH, then extracted with solvent. The composition of the extraction solvent solution affected recoveries of the alkaloids, particularly nornicotine, and also contributed to other phenomena such as carry-over in the injection liner and "quenching" of the nitrogen-phosphorus detector. Use of a packed injection liner (e.g. with Carbowax-KOH on Chromosorb) to reduce carry-over was studied. Quenching of the nitrogen-phosphorus detector was eliminated by reducing the injection volume (i.e. increasing the split ratio), by use of a packed injection liner, and by reducing the amount of pretreatment with aqueous ammonia. A narrow bore capillary column (i.e. 0.18 mm id) was used to improve sensitivity and resolution and to increase the speed of GC analysis. An internal standard, 2,4'-dipyridyl, was used for quantitative measurement of these tobacco alkaloids.

Alkaloids↗

PubMed2002

Optimization of headspace sampling using solid-phase microextraction for volatile components in tobacco.

Solid-phase microextraction (SPME) was evaluated as a tool for headspace sampling of tobacco samples. Several experimental parameters (e.g. sampling temperature, pH, moisture, and the type of SPME fibers) were optimized to improve sampling efficiency in two aspects; maximum adsorption and selective adsorption of volatile components onto SPME fibers. The effect of these parameters was often dominated by the physical and chemical nature (e.g. volatility, polarity) of target compounds, thus, SPME sampling conditions can be adjusted to favor a selected group of compounds, such as organic acids in tobacco.

Gas Chromatography-Mass Spectrometry↗

PubMed1996

Recent advances in the residue analysis of N-methylcarbamate pesticides.

This paper highlights recent advances in the determination of methylcarbamate residues in water, soil and plant tissues. Chromatographic analyses (e.g., HPLC, GC, supercritical fluid chromatography and TLC) with various sample pretreatment procedures and detection methods are reviewed. More generally, some non-chromatographic techniques such as immunoassay, biosensor and spectrophotometry are included.

Biosensing Techniques↗

PubMed1996

Evaluation of micellar electrokinetic capillary chromatography for the analysis of selected tobacco alkaloids.

Micellar electrokinetic capillary chromatography was evaluated for simultaneous determination of several tobacco alkaloids with similar molecular structure. Satisfactory separation of nicotine, nornicotine, myosmine, anatabine and anabasine extracted from tobacco was achieved by introducing an ionic surfactant, sodium dodecyl sulfate, into the buffer system at a concentration of 100 mM. Sample preparation involved a single extraction with water containing 1% triethanolamine. Separation was performed on a 72 cm long, uncoated fused-silica capillary. Experimental parameters such as applied voltage, pH value, buffer composition and surfactant concentration were optimized. Enhancement of UV absorption of alkaloids in the presence of micelles was also studied.

Alkaloids↗

PubMed1994

Determination of aldicarb, aldicarb sulfoxide and aldicarb sulfone in tobacco using high-performance liquid chromatography with dual post-column reaction and fluorescence detection.

A screening method for the determination of aldicarb (AS) and its sulfoxide (ASX) and sulfone (ASN) metabolites in tobacco at low ppm levels is described. Tobacco samples are extracted using methanol with the aid of sonication at ambient conditions. The extract is filtered and then injected into a high-performance liquid chromatograph equipped with a dual post-column reaction system and a fluorescence detector. Chromatographic separation is performed on a C18 column with a mixture of methanol-acetonitrile-water containing 0.1% of triethanolamine as the mobile phase. Triethanolamine is added to improve peak shape of AS residues and to reduce the undesired interaction between residual silanols and interferences, mainly amino acids and other amines. The average recoveries for AS residues spiked in tobacco are higher than 95% for AS, 91% for ASN and 85% for ASX at levels of 0.5-10 ppm (w/w). The detection limit is 0.5 ppm for each of the target compounds.

Aldicarb↗