Development of an isotope dilution GC–MS procedure for the routine determination of creatinine in complex serum samples

• Isotope dilution GC–MS procedure for routine determination of serum creatinine
• Application of microwave radiation decreases sample preparation time.
• Minimally labeled analog and multiple linear regression avoid calibration graph.
• Method provides serum creatinine concentrations in less than 45 min.
• Comparison with Jaffé and enzymatic methods in interfered serum sample analyses

The accurate determination of creatinine in serum is essential for the diagnosis and treatment of kidney diseases. The determination of serum creatinine in clinical laboratories is routinely carried out by the Jaffe method or by enzymatic methods that may suffer from interferences. So, the development of reliable, fast and interference-free routine methods for complex serum samples is required. A fast method using isotope dilution mass spectrometry (IDMS) and gas chromatography mass spectrometry (GC–MS) was developed using minimally 13C labeled creatinine analogs, multiple linear regression and rapid derivatization of creatinine with acetylacetone in 2 min by using focused microwave technology. The proposed method was validated with the analyses of two Certified Reference Materials (ERM-DA252a and ERM-DA253a) and compared with the Jaffe and enzymatic methods when analyzing real serum samples containing variable levels of bilirubin The proposed method is capable of providing accurate serum creatinine concentrations in less than 45 min from sample arrival to full data treatment and can be an alternative routine procedure for creatinine determinations in complex serum samples.