In this study, proton affinitive derivatization using picolinic acid and its analogs (3- and 6-methylpicolinic acid and 5-butylpicolinic acid) with proton affinitive moieties was performed for the highly sensitive determination of testosterone (T) and 5α-dihydrotestosterone (DHT) in saliva by LC-ESI-MS/MS. T and DHT were converted to their corresponding picolinate esters and their chromatographic behavior was investigated with a reversed phase column. The picolinate ester of each steroid exhibited a clear single peak and elution occurred in the following order: picolinate, 3/6-methylpicolinate, and 5-butylpicolinate. Estimation and understanding of the separation and retention time of each picolinate ester was made simple using the develop method. Although the peaks of picolinate and 3/6-methylpicolinate esters were suppressed by interference from the saliva background (matrix effect), the 5-butylpicolinate esters were only marginally affected.
Keywords: LC-MS/MS; Proton affinitive derivatization; ion suppression; matrix effect; picolinic acid analog; saliva sample.