Study on the potential application of salivary inorganic anions in clinical diagnosis by capillary electrophoresis coupled with contactless conductivity detection

• The interesting inorganic anions in saliva were directly determined by CE–C4D.
• The LODs could reach ng/mL level with the assistance of online enrichment approach.
• The advantages are high sensitivity, low cost fabrication and without derivatization.
• This proposed method provided a potential fast screening tool for clinical test.

A capillary electrophoresis approach with capacitively coupled contactless conductivity detection method has been developed for the determination of inorganic metabolites (thiocyanate, nitrite and nitrate) in human saliva. Field amplified sample injection, as a simple sample stacking technique, was used in conjunction for online preconcentration of above inorganic anions. A selective separation for the target anions from other coexisting constituents present in saliva could be obtained within 14 min in a 10 mmol/L His—90 mmol/L HAc buffer (pH 3.70) at the separation voltage of −18 kV. The limits of detection and limits of quantification of the three analytes were within the range of 3.1–4.9 ng/mL (S/N = 3) and 10–16 ng/mL (S/N = 10), respectively. The average recovery data were in the range of 81–108% at three different concentrations. This method provides a simple, rapid and direct approach for metabolite analyses of nitric oxide and cyanide based on noninvasive saliva sample, which presents a potential fast screening tool for clinical test.