Isotope dilution-LC-MS/MS method for quantification of the urinary cotinine-to-creatinine ratio.

One essential novelty of the method presented here is the simultaneous quantification of creatinine and cotinine covered by one analytical method. Despite the very different natural concentrations of creatinine and cotinine, this allows the immediate reporting of the cotinine-to-creatinine ratio without the need for a separate creatinine analysis.