INFLUENCE OF THE CAPILLARY DIMENSIONS ON THE PERFORMANCE OF THE PRECONCENTRATION TECHNIQUE BASED ON PARALLEL CURRENT CHROMATOGRAPHY

The influence of the inner capillary diameter, length of the capillary , linear velocity of the mobile phase and volume of the retentive liqu id segment on the dynamic range of the gradient and the efficiency of enrichment of the new preconcentration technique was studied. Phenol, 2,4-dinitroaniline, phenanthrene and fluoranthene in water solution we re used as model analytes. Capillaries with inner diameters of 0.095 m m and 0.2 mm and lengths ranging from 3.5 to 15 m were examined. The s egment of the retentive liquid in capillary was generated by the injec tion of suitable volume of cyclohexanol. It was found that the enrichm ent increases with decrease in the inner capillary diameter and with i ncrease in its length. The working range of this technique was found. With analytes in sub-ppb concentrations in the injected sample, an enr ichment factor up to 280 was achieved. The application possibilities o f proposed procedure was demonstrated by off-line capillary GC analysi s of collected enriched solution of model mixtures of alkyl phthalates and polyaromates. (C) 1997 Elsevier Science B.V.