Total protein determinations by particle beam/hollow cathode optical emission spectroscopy (PB/HC-OES) system III: Investigation of carrier salts for enhanced particle transport

Particle beam hollow cathode optical emission spectroscopy (PB/HC-OES) is evaluated as a generic tool for total protein determinations by monitoring the carbon atomic emission (C (I) 193.0 nm) resultant from dissociated analyte species. Previous studies demonstrated the capability of the PB/HC-OES system for total protein determinations with limits of detection for bovine serum albumin (BSA) samples being at the single-nanogram level for 200 l injections. Non-linear behavior across the concentration range in the calibration curve was observed due to the poor transport of small particles (owing to low analyte concentrations) through the PB interface. The potential use of non-volatile salts as carrier agents is investigated in the determination of protein samples by PB/HC-OES. A range of chloride salts (different cations), potassium salts (different anions), and an organic modifier (ammonium acetate) is investigated here for possible use as carriers upon addition as sample injection matrices for protein samples. The analyte response curves of BSA samples with KCl added as the sample injection matrix show higher sensitivity, better linearity (R²) and subsequently lower detection limits in comparison to those obtained with water, HCl, KNO₃ or ammonium acetate as carrier matrices.