Validation of a simple and cheap standard addition method for the determination of nitrate levels in human saliva by UV spectrophotometry

Epidemiological data shows that human exposure to nitrates is related to some cancers, with salivary nitrate analysis proposed as a measure of nitrate burden and as an indicator of risk for upper aerodigestive tract cancers. However, mean salivary nitrate values in literature shows great differences, namely for basal values turning hard the use of this biomarker in consistent way. This work aimed to develop and validate a standard addition method for determination of salivary nitrate, which could provide reliable results. Nitrate determination had a confidence interval of 0.37 mg/L while intra- and interday standard addition points accuracy, measured by Addition Quantification Accuracy (Qbias%), and precision, measured by Coefficient of Variation (CV%) were within acceptance criteria, ±15% and