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Microwave Digestion of Textile Sample and TLC Determination of Heavy Metals

Determination of metal content present in the textile fibre and textile materials is of great importance because of possible effects on processing and product quality, and of potential environmetnal concerns and constrains. Presence on inorganic elements in raw cotton depends on soil, growth area and harvest season, while in textile material can be the result of processing: Co, Cr, Cu and Ni form a part of some dyes, while zinc and manganese salts are used extensively in textile processing. Iron can be present either as the result of contamination or from the soil.Total inorganic constituents in various samples of cotton vary considerably, and are present as ash 0.1 to 1 %. A possibility of metal ion separation and identification by thin-layer chromatography after sample microwave digestion in the microwave oven (CEM, Matthens, NC, USA) with nitric acid and water was examined. The best separation was achieved on microcrystalline cellulose pre-coated layers with the acetonitrile- HCl konc. - water (15:12:73) developer and by visualisation with quercetine - dimethiglioxime - NH3 reagents. A highly sensitive 3CCD colour video camera HV-C20 (Hitachi, Densi, Japan) was used to capture the chromatograms under white light. Image acquisition, processing and archiving were controlled via Video Store 2 version 2.30 documentation software (Camag, Muttenz, Switzerland). Rf values were determined from the stored chromatograms via Vista Scan TLC/HPTLC 1.01.00 program. Spoth width (w) was determined for diferent metal ions, and resolution factor (Rs) was calculated. All the statistical and contour plot constructions were done by experimental design software package Design-Expert 6 (DX6). Optimisation of mobile phase composition was performed to improve the separation of all the individual components of the mixture with as few experiments as possible. The principle of optimization was the relationship between resolution factor (Rs) and the composition of ternary mobile phase. The results were analysed via State-ease software package Design - Expert 6 which calculated the area where all Rs values exceeded value of 1.

heavy metals; TLC; textile material; optimisation

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