Calibrationless quantitative analysis by indirect UV absorbance detection in capillary zone electrophoresis: The concept of the conversion factor

A new, fast and efficient procedure is described for the simultaneous quant. anal. of various non-UV absorbing species in a sample, by capillary zone electrophoresis with indirect UV absorbance detection. The procedure is based on the concept of the conversion factor (CF). The CF of an analyte is defined as the ratio of the measured temporal peak area and the product of its migration time and transfer ratio (TR). Thus defined, the CF is of general validity for all analytes sepd. and detected in a given background electrolyte (BGE), since it has the same value for the same amts. of various analytes. If a sample is enriched with a known concn. of a std. component and analyzed by CZE, the CF of this std. component can be calcd. and then the concns. of all other analytes can be detd., without the use of any calibration graph. The individual TRs can be detd. a priori from tabulated ionic mobilities and pK values of the analytes and of the constituents of the BGE or, for strong analytes, by using exptl. data from the electropherogram of the anal. itself. The practical procedure of the anal. includes enrichment of the sample with a known quantity of a suitable std. and a single CZE run of the resulting mixt. The injected vol. does not need to be known and thus the procedure also eliminates the injection error. The proposed procedure was verified exptl. and reproducible and accurate values were obtained by using four different CZE app. for the analyses of std. mixts. of cations in three different BGEs. [on SciFinder (R)]