Potential of electrospray mass spectrometry for quantifying glycohemoglobin

An electrospray ionization-mass spectrometric procedure has been developed for determining glycohemoglobin. Whole-blood samples from 78 diabetic and 50 nondiabetic subjects (glycation range 3-15%, as determined by electrospray mass spectrometry) were diluted 500-fold in an acidic denaturing solvent and introduced directly into a mass spectrometer. The resulting mass spectra were then processed to estimate the percentage of glycohemoglobin present in the sample. Total analysis time, including plotting the spectra and computing the percentage of glycation, was approximately 3 min. The imprecision (CV) of the method was < 5.1% for inter- and intrabatch analyses for total glycohemoglobin in the range 3.6-14%. Comparison of the mass spectrometric results with those from established affinity chromatographic procedures showed good overall agreement. The relative glycation of the alpha- and beta-chains was determined directly and was shown to be constant (0.64:1) over the glycation range measured. Only single glucose attachment to both the alpha- and beta-chains was observed.