Specific and robust ion chromatographic determination of hypothiocyanite in saliva samples

Abstract

The enzymatic system in saliva, consisting of salivary peroxidase (SPO), hydrogen peroxide (H2O2), and thiocyanate (SCN−), produces hypothiocyanite (OSCN−) as a high effective antibacterial compound. OSCN− is of great importance for the natural non-specific antibacterial resistance in the oral cavity. However, no analytical method currently exists to selectively quantify OSCN− in saliva samples. A robust and specific analytical method for the determination of OSCN− was developed based on ion chromatography with combined UV and electrochemical detection. Calibration was achieved by calculating a derived calibration factor based on the known ratio of molar extinction coefficients of SCN− and OSCN−. Thus, the specific quantification of OSCN− in saliva samples is possible, as demonstrated here. The median value of 200 saliva samples was determined to be 0.56 mg L−1 (median), with a maximum of 3.9 mg L−1; the minimum value was below the detection limit (< 0.09 mg L−1). The recovery rate in individual saliva samples was 95 ± 8%.