Determination of glycine in body fluids at trace levels using the combination of quadrupole isotope dilution strategy and Liquid Chromatography-Quadrupole Time of Flight-Tandem Mass Spectrometry

In this study, Quadrupole Isotope Dilution Mass Spectrometry (ID⁴MS) strategy was coupled with Liquid Chromatography-Quadrupole Time of Flight-Tandem Mass Spectrometry (LC-QTOF-MS/MS) for the accurate and precise determination of glycine in body fluids at trace levels. The instrumental variables such as column temperature, injection volume, sample/gas flow rates, fragmentor/capillary voltages, were optimized. Under the all optimized conditions, the calibration plot of glycine demonstrated a linearity ranging 5.0–100 mg kg⁻¹ and, the detection and quantification limits were obtained as 1.4 and 4.7 mg kg⁻¹, respectively. Superior enhancement was achieved for the accuracy and precision of proposed method when combined with ID⁴MS strategy. Percent recoveries of the proposed method for human plasma and urine spiked at 80 mg kg⁻¹ were calculated as 99.72 ± 0.54% and 100.91 ± 1.32%, respectively. These results validated the applicability of the method to complex matrices as well as confirming the high accuracy and precision.