Preconcentration of albumin on silica with attached groups of polyoxyethylated isooctyl phenol

The potencies of silica with attached groups of polyoxyethylated isooctyl phenol (SiO ₂ -TX) as an adsorbent for the solid phase extraction (SPE) preconcentration of bovine serum albumin (BSA) in urine are examined. SiO₂-TX is shown to effectively extract BSA (up to 96%) as an ion associate with cationic (at pH 8) and anionic (at pH 1.5) surfactants. The maximal capacity of SiO₂-TX to BSA makes 33 mg/g in the presence of octylpyridinium bromide, 27 mg/g in the presence of cetyltrymethylammonium bromide or sodium dodecylsulfate with the linearity range in Henri’s area up to 23 and 20 mg/g of SiO₂-TX, respectively; the distribution coefficients attain 1.8 × 10³ mL/g. BSA is eluted quantitatively with 1–4 mL of acetonitrile containing NaOH, which makes possible the use of adsorbent for the reaction of protein with trifluoroethanol (TFE) before its photometric determination by the Lowry method. The influence of accompanying urine components is studied, i.e., urea, glucose, Na⁺, K⁺, Mg²⁺, chlorides, and phosphates, on the efficiency BSA extraction from model aqueous solutions on SiO₂-TX. The detection limit for BSA makes 4 mg/L and the analytical range, from 12 to 140 mg/L.