Convective Interaction Media Monolithic Chromatography with ICPMS and Ultraperformance Liquid Chromatography−Electrospray Ionization MS Detection: A Powerful Tool for Speciation of Aluminum in Human Serum at Normal Concentration Levels

Abstract

A new analytical procedure using separation support based on Convective Interaction Media (CIM) was developed for speciation of Al in human serum at normal concentration levels. The separation of proteins was performed on a weak anion exchange CIM diethylamine monolithic column. Isocratic elution with buffer A (0.05 M tris(hydroxymethyl)aminomethane−hydrochloric acid + 0.03 M sodium hydrogen carbonate) was applied for 5 min, followed by linear gradient elution from 100% buffer A to 100% buffer B (buffer A + 1 M ammonium chloride) for the next 40 min. Separation of proteins was followed by UV detection at 278 nm. Separated Al species were detected online by inductively coupled plasma mass spectrometry. It was experimentally proven that 91 ± 7% of Al in human serum was eluted under the transferrin peak. Transferrin was identified on the basis of the retention volume and by ACQUITY ultraperformance liquid chromatography−electrospray ionization mass spectrometry. The problem of extraneous contamination with Al was successfully overcome by using efficient cleaning procedures of eluents and chromatographic supports. The efficient cleaning was of paramount importance to perform Al speciation at extremely low concentration levels. The repeatability of measurement tested for six consecutive separations of unspiked serum was ±8.6%. The limits of detection and quantification (based on 3 and 10 s of the blank) were 0.15 and 0.49 ng mL⁻¹ Al bound to transferrin, respectively. This is the first report on quantitative and reliable speciation of Al in human serum at normal concentration levels.