No abstract

The objective of this work was to design, construct and test the sample focusing and concentration enrichment device for gas chromatography. The device was based on four metal rings, between which a capillary column and two wire heaters were placed. The metal rings were connected to each other and cooled down using liquid nitrogen. The column was connected to the gas chromatography system using a heated transfer line. The research was conducted on how the length of the cooled column influences focusing and enrichment capabilities of the system. It was found that the analytes were focused better by using a longer cooled part of the column. The longer cooled column was also able to retain a greater volume of the analytes, injected consecutively. By using the 95 cm cooled column length, it was possible to retain 20 injections and detect a 20 times bigger peak area. By changing the temperature of the cooling zone, it was also observed that peak symmetry is heavily dependent on it. Lower cooled zone temperatures produced narrower and more symmetrical peaks.

A fast, precise and accurate high performance liquid chromatography method has been developed for the determination of dyes (Solvent Red 19 and Solvent Blue 35) and a marker (Solvent Yellow 124) in diesel. Separation was carried out on a 250 × 4.60 mm Agilent Zorbax Rx-SIL column (5 µm particle size). Detection was done in a visible wavelength range. The best performance of fuel dye separation and the shortest retention times were achieved when using hexane, toluene and ethyl acetate as a mobile phase. During this research the eluent composition and the elution gradient were optimized consequently that helped to perform the analysis within 15 min. The developed method was applied for the analysis of real samples of dyed diesel fuel. Preparation of the samples for the analysis simply consisted of filtering through a 0.45 µm filter previous to direct injection of the sample into the HPLC system for analysis.

We aimed to demonstrate that breath analysis can be used as a method for the detection of potentially harmful compounds in food after their ingestion. Development of such a method could be adapted as a tool for detection of food intoxication. To achieve this, we compared the levels of pyridine (Py) and furfuryl alcohol (FFA) found in breath with the quantity of these compounds ingested when drinking coffee. Coffee drink beverages were prepared in the laboratory and consumed by volunteers (n = 5). An aliquot of coffee was analysed using high performance liquid chromatography with diode-array detection (HPLC-DAD) to quantify Py and FFA in the beverage. Breath samples were collected several times over a 45 min period after ingestion of coffee and analysed by thermal desorption coupled to gas chromatography/mass spectrometry (TD/GC-MS). The levels of Py and FFA found in coffee ranged from 0.2 to 3 mg/cup of coffee, and from 7 to 30 mg/cup of coffee, respectively. The levels of these compounds detected in breath ranged from 7 to 1200 ng/l breath for Py and from 1 to 760 ng/l breath for FFA. Several parameters can influence the levels of these chemicals in breath, especially the collection time of the breath sample.

The aim of this study was to show how volatile organic compounds (VOCs) profiling can be used as a method to identify different environments across a city. To achieve that, we employed several methods. First, we carried out the profiling of VOCs in several different locations. Then we identified the marker compounds and their sources. Air samples were collected from 6 different locations within the Vilnius City centre using thermal desorption (TD) tubes. Samples were analysed using thermal desorption coupled with gas chromatography mass spectroscopy (TD/GC-MS) methodology. Compound identification was performed by the library match using the NIST MS Search 2.0 (2005) mass spectral library. The results show how variation in the levels of different VOCs can distinguish between locations within a relatively small area of 2 km2 depending on different emission sources.