Vida Vickackaite

Headspace extraction of alcohols into a single drop

The possibility of applying headspace microextraction into a single drop for the determination of alcohols in aqueous solutions is demonstrated. A drop of ethylene glycol containing butan-2-one as an internal standard is used for extraction. The analytes are extracted by suspending a 1 μl extracting drop directly from the tip of a microsyringe fixed above an extraction vial with a septum such that the needle passes through the septum and the needle tip appears above the surface of the solution. After the extraction is finished the drop is retracted back into the needle and injected directly into a GC column. Optimization of experimental conditions (sampling time, sampling temperature, stirring rate and ionic strength of the solution) with respect to the extraction efficiency were investigated and the linear range and the precision were examined. This headspace single drop microextraction method was applied to the analysis of beer.

Hollow fibre liquid phase microextraction of parabens

A hollow fibre liquid phase microextraction for gas chromatographic determination of some p-hydroxybenzoic acid esters has been developed. Chlorobenzene containing tetradecane as internal standard was used for the extraction. Optimized extraction was carried out at room temperature for 40 min in the presence of 0.4 g mL−1 NaCl in the sample solution. Calibration was linear up to 30 mg L−1. Correlation coefficients were 0.996–0.998. Enrichment factors were 21, 95 and 154, and detection limits were 0.20, 0.03 and 0.01 μg mL−1 for methylparaben, ethylparaben and propylparaben, respectively. Reproducibility was acceptable with relative standard deviations up to 11.7%. The technique was tested for water and urine analysis.

Speciation of methyltins by dispersive liquid–liquid microextraction and gas chromatography with mass spectrometry

Dispersive liquid-liquid microextraction in combination with an in situ derivatization is suggested for methyltin compound sampling and preconcentration from water solutions. The derivatization was carried out with sodium tetraethylborate at pH 3. The effects of extraction and disperser solvents type, volume, and extraction time on the extraction efficiency were investigated. 1,2-Dichlorobenzene was used as an extraction solvent and ethanol was used as a disperser solvent. The calibration graphs for all the analytes were linear up to 2 μg (Sn) L(-1), correlation coefficients were 0.998-0.999, LODs were 0.13, 0.05, and 0.06 ng (Sn) L(-1) for trimethyltin, DMT, and monomethyltin, respectively. Repeatabilities of the results were acceptable with RSDs up to 12.1%. A possibility to apply the proposed method for methyltin compound determination in water samples was demonstrated.

Polyaniline-polypyrrole coating for solid phase microextraction

A procedure for direct electrochemical deposition of polyaniline-polypyrrole blend coating on the surface of stainless steel wire was suggested. Incorporation of polyaniline and polypyrrole into the blend coating was confirmed by infrared spectroscopy. Key parameters (pyrrole, aniline, dopant and sulphuric acid concentrations and deposition potential) influencing the coating’s mechanical stability and surface homogeneity were optimised and thermostability of the coating was investigated. A possibility to apply the coating as a new fibre for solid phase microextraction was demonstrated. The coating showed better selectivity toward aromatic, hydrophobic compounds.

Determination of β-alaninediacetic acid in waste waters and aquatic environment using GC-NPD

New chelating agents need to be applied to industrial purposes, because the conventional compounds, such as ethylenediaminetetraacetic acid (EDTA), have been demonstrated to cause adverse environmental effects. A promising compound in this respect is β-alaninediacetic acid (β-ADA). A reliable analytical procedure for the determination of β-ADA in waste waters and natural waters is presented in this study. The method is also applicable to sediments after extraction of β-ADA with phosphate. An aqueous sample was evaporated to dryness and treated with an esterification reagent containing ethanol, propanol or butanol. The resulting esters were determined by capillary gas chromatography using a nitrogen–phosphorus specific detector (GC-NPD). The best results were obtained by esterification with propanol at 86 °C for 2 h. The response was linear up to 10 mg dm–3. The limits of detection in distilled, waste, lake and sea waters were 2.0, 2.7, 2.5, 2.9 µg dm–3, respectively, and 0.21 µg g–1 in sediments. The relative standard deviation (RSD) values of retention times did not exceed 0.46%. The run-to-run and day-to-day repeatabilities (calculated as RSD) in distilled water were below 7%, except near the limit of detection. In the natural waters studied the recoveries were 49–111%, in sediments only 19–21%. High concentrations (above 10 mg dm–3) of Fe3+ interfere with the determination of β-ADA.

The current state of analytical control in Lithuania

In Lithuania research and development in chemical analysis are concentrated in scientific institutes and universities. The main fields of interest focus on biosensors, electrochemical sensors, sampling techniques and methods, study of atomization processes in spectrochemical analysis and noise evaluation in analytical measurements. Some laboratories also take part in international environmental monitoring programmes. There are about 50 researchers at the Ph.D. level engaged in analytical chemistry and several hundred technicians specialized in the field of analytical control. About one hundred chemical laboratories are active in scientific institutes, universities and factories. Specialized laboratories of chemical analysis are at the disposal of Environmental Control and Health Protection Departments and forensic investigation organizations. So far no laboratories are accredited according to the ISO 9000 norms. Special courses on analytical chemistry are offered at a few schools of higher education in the country. Only at the Department of Analytical Chemistry of the University of Vilnius specialized programmes are available to postgraduate students working towards a Ph.D. to improve their skills in current techniques of analytical chemistry. Recently the Technical Committee TC-16 for Chemical Analysis was formed within the standardization system of Lithuania. Its main activities are centered on issues such as national terminology, certified reference materials (CRMs), analytical methods and analytical quality assurance. There are numerous problems related to national terminology, the preparation of special documents in the field of analytical control and the production of regional environmental CRMs. Problems, also arise in obtaining and using CRMs for analytical instrument calibration and validation.