DETERMINATION OF NITROPHENOLS BY CAPILLARY ZONE ELECTROPHORESIS IN A HYDRODYNAMICALLY CLOSED SEPARATION COMPARTMENT

The use of beta-cyclodextrin (beta-CD) and polyvinylpyrrolidone (PVP) as complexing agents to capillary zone electrophoretic (CZE) separatio ns of a group of ten nitrophenols was investigated. The analytes were baseline resolved in one CZE run when PVP was present in the carrier e lectrolyte at a 2.5% (w/v) concentration. beta-CD was less effective a s it did not baseline resolve a complete group of the studied nitrophe nols within an applicable concentration range (0-10 mmol/l). The separ ations were carried out in a 300-mu m I.D. capillary tube made of fluo rinated ethylene-propylene copolymer to enhance the load capacity of t he separation system. Under these working conditions, a 100-nl sample injection volume resulted in 20-80 ppb concentration limits of detecti on for nitrophenols, using a photometric absorbance detector operating at a wavelength of 254 nm. The separation efficiencies for the analyt es spanned from 1.6-2.10(5) theoretical plates per meter. Their migrat ion times were reproducible not only in a within day but also in a day -to-day time frame (1% or less for a period of several weeks). This wa s achieved for a hydrodynamically closed separation compartment while minimizing fluctuations in the concentration of CO2 in the carrier ele ctrolyte. Reproducibility in the determination of nitrophenols was in the range of 1-5% for 1-6 ppm concentrations. Rain, drinking and proce ss water samples served as matrices to assess the practical applicabil ity of the elaborated CZE procedure. This procedure can be combined wi th isotachophoretic sample pretreatment to make its use possible in si tuations when nitrophenols are present in the samples at low ppb conce ntrations.