2134/14464 Neil A. Devenport Neil A. Devenport Daniel J. Blenkhorn Daniel J. Blenkhorn Daniel J. Weston Daniel J. Weston Jim Reynolds Jim Reynolds Colin Creaser Colin Creaser Direct determination of urinary creatinine by reactive-thermal desorption-extractive electrospray-ion mobility-tandem mass spectrometry. Loughborough University 2014 untagged Chemical Sciences not elsewhere classified 2014-04-10 12:48:12 Journal contribution https://repository.lboro.ac.uk/articles/journal_contribution/Direct_determination_of_urinary_creatinine_by_reactive-thermal_desorption-extractive_electrospray-ion_mobility-tandem_mass_spectrometry_/9390128 A direct, ambient ionization method has been developed for the determination of creatinine in urine that combines derivatization and thermal desorption with extractive electrospray ionization and ion mobility-mass spectrometry. The volatility of creatinine was enhanced by a rapid on-probe aqueous acylation reaction, using a custom-made thermal desorption probe, allowing thermal desorption and ionization of the monoacylated derivative. The monoacyl creatinine [M + H] ion (m/z 156) was subjected to mass-to-charge selection and collision induced dissociation to remove the acyl group, generating the protonated creatinine [M + H] product ion at m/z 114 before an ion mobility separation was applied to reduce chemical noise. Stable isotope dilution using creatinine-d as internal standard was used for quantitative measurements. The direct on-probe derivatization allows high sample throughput with a typical cycle time of 1 min per sample. The method shows good linearity (R = 0.986) and repeatability (%RSD 8-10%) in the range of 0.25-2.0 mg/mL. The creatinine concentrations in diluted urine samples from a healthy individual were determined to contain a mean concentration of 1.44 mg/mL creatinine with a precision (%RSD) of 9.9%. The reactive ambient ionization approach demonstrated here has potential for the determination of involatile analytes in urine and other biofluids. © 2013 American Chemical Society.