Evaluation of multiple hydrophilic interaction chromatography columns and surrogate matrix for arginine quantification in saliva by high-resolution mass spectrometry

Arginine, a pivotal ingredient in many biochemical synthetic pathways, can be used as a biomarker for many oral care clinical applications. It is still a challenge to develop a sensitive and reliable chromatographic method to quantify arginine as a biomarker in saliva, with or without arginine product pretreatment. The current method solved two critical issues for arginine quantitation in human saliva. The first issue was how to optimize arginine peak shape. A hydrophilic interaction chromatography method based on the column selection, pH and pKa relationship, mobile phase ionic strength, organic solvent consideration, and temperature effects was developed. An optimized chromatographic condition for arginine quantitation in the saliva matrix was obtained. The second issue was how to build confidence in the use of a simple surrogate matrix methodology to replace the more complex traditional standard addition methodology. The surrogate matrix methodology we developed is applicable to the measurement of arginine as a potential non-invasive biomarker in human saliva. The method detection and quantification limit reached 2 and 6 ng/mL. The tailing factor was within the 0.9-1.1 range even though arginine had three pKa values at 2.18, 9.09, and 13.2.

Automated summary

The study developed a chromatographic method for quantifying arginine as a biomarker in saliva, solving key issues of peak shape optimization and surrogate matrix methodology replacement for traditional methods. The method achieved detection and quantification limits of 2 and 6 ng/mL with a tailing factor within the 0.9-1.1 range.