Human salivary anionic analysis using ion chromatography

Objective: To survey concentrations and time-variability of the major anions of human saliva using ion chromatography (IC). Materials and methods: Resting saliva samples after overnight fasting, obtained under standardized conditions in time-series for 10 subjects, were analysed for chloride, phosphate, nitrate, sulphate, thiocyanate, acetate and lactate. A second group of five subjects provided mixed saliva as before, and in addition a sample of parotid saliva collected immediately afterwards using a Lashley cup. Analysis was by ion chromatography (DX-100, Dionex) using 1.7 mM NaHCO3 + 1.8 mM Na2CO3 + 100 mg/L p-cyanophenol (2 mL/min) and 1.6 mM perfluorobutyric acid + 0.3 mM sodium hydroxide (0.3 mL/min) as eluents for inorganic and organic anions, respectively. Results: The time-series data showed great natural variability. Analysis of the correlations showed that the concentration of nitrate was uncoupled from those of the other anions. Lactate was not detected. Parotid saliva showed marked differences from mixed saliva, most notably the absence of acetate and the presence in two instances of lactate. Bromide, nitrite and citrate were not detected. Conclusions: Acetate is a major component of the oral chemical environment. Simultaneous analyses permit the investigation of the relationships between component concentrations that otherwise might have been difficult to study.