Mass spectrometric study of randomly methylated ?-cyclodextrins using ionspray, atmospheric pressure chemical ionization and matrix-assisted laser desorption/ionization

Abstract

Mixtures of methylated beta-cyclodextrins were characterized using three different methods of mass spectrometry: ionspray, atmospheric pressure chemical ionization (APCI) and matrix-assisted laser desorption/ionization (MALDI). Each of these methods allows a fast and simple determination of the degree of substitution, and can provide evidence for differences in the methylation of batches which have very similar global degrees of substitution. The three methods are in good qualitative agreement, but there are systematic differences in the quantitative results for the percentages of the various methylated molecules present in a batch. This is attributed to ionization yields which increase with the number of methyl groups, with different slopes for the different methods.

Probing the common alkali metal affinity of native and variously methylated β-cyclodextrins by combining electrospray-tandem mass spectrometry and molecular modeling

“…Different 1 : 2 complexes were observed for Li + , Na + and K + with native b-CD, but only the variously methylated b-CDs allowed to detect a complex involving two K + . 29,31,32 Here, they were found to carry 2 to 11 methyl groups and 9 to 17 methyl groups, respectively ( Fig. In the same time, affinity for lithium dropped by twofold (17% to 33-35%) while relative abundance of potassied species remained steady (11-17%).…”

“…HCD mode. 29,31,32 Based on chemical reactivity of b-CD hydroxyls during methylation processes, we tentatively assigned the first subset curve to an homogeneous 2,6-O-methyl-b-CD and the second subset curve to a 2,3,6-O-methyl and 6-O-methyl glucose units randomly distributed through the one b-CD molecule for a total of 14 methyl groups. This one-third rule is governed by the choice of the instrumental Q value depending on the r f amplitude.…”

“…If CID is a standard fragmentation technique easily accessible in present-day instruments, it suffers from a well-known low-mass cutoff (LMCO) limitation which does not allow the trapping of fragments below 30% of the precursor m/z. 5E and (26,32,38 and 48 eV for-native b-CD, CRYSMEB, RAMEB and TRIMEB, respectively) ( Fig. An alternative way is the recently introduced HCD fragmentation in a not Q dependent matter.…”

What structural information can ion trap mass spectrometry bring for the characterization of permethylated cyclodextrins?

“…Ammonium salts are often preferred in ESI-MS because they are more volatile. [7][8][9] The spectra obtained here, however, showed better signal/noise and better sensitivity with NaCl than with NH 4 CH 3 CO 2 (data not shown). Addition of NaCl, a non-volatile salt, is usually thought to induce pollution of the source.…”

“…In fact, quadrupole mass spectrometry with electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) has been used to determine the DS for DiMe-b-CD, 7 Me-b-CD, 8,9 and sulfobutylether-CD. 10 Ion trap mass spectrometry (ITMS), has, however, been rarely described in the literature for this purpose.…”