Detection of carbohydrates by electrospray ionization ion mobility spectrometry following microbore high-performance liquid chromatography

This paper reports the first example of electrospray ion mobility spectrometry as a detection method for HPLC separation, demonstrating its potential for the quantitative and selective detection of non-volatile and non-chromophoric organic compounds. Reduced mobility constants (K-o) for 21 carbohydrates, including simple sugars, sugar alcohols and amino sugars, were determined to range from 0.68 to 1.37 cm(2) V-1 s(-1). Minimum detectable quantities were measured from as low as 5.8.10(-14) mol for D(+)-cellobiose to as high as 8.2.10(-11) mol for L-iditol. A plot of carbohydrate mass with respect to inverse ion mobility indicated that, to a first approximation, mobility was inversely proportional to mass for most carbohydrates. However, in several cases, isomeric separation could be achieved by ion mobility spectrometry, demonstrating that ion mobility separation is based on size and shape of the molecule rather than molecular mass. Other notable exceptions to the mobility-mass relation were beta-D-maltose and D(+)-cellobiose, which exhibited significantly lower mobilities than expected, and maltoheptaose, which exhibited a significantly higher mobility than expected. Dimerization and multiple charges may have caused these deviations from the simple mass-mobility correlation. Parametric optimization coupled with further basic investigations of this ionization and detection method should lead to a novel approach for the analytical determination of carbohydrates. (C) 1998 Elsevier Science B.V. All rights reserved.