This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.Glycans may be considered to a first approximation as an acidic comound class. This is justified for animal glycans based on relatively high levels of capping of N- and O-glycans with sialic acids and by the prevalence of the sulfated glycosaminoglycan classes. It is becoming clear that mass spectrometric analysis of native glycans is best accomplished using negative ions. As part of the activity at the MSR, amide-silica HILIC and porous graphitized carbon have been used for native glycan separations. Commercial mass spectrometric interfaces have been optimized for analysis of biomolecules in the postive ion mode. The most common spray devices employ silica or stainless steel materials. Silica material does not produce adequate spray stability in the negative mode due to a variety of factors. Stainless steel may undergo electrochemical reactions during the negative ion electrospray process. The extent to which these problems occur depends on the commercial instrument being used. To date, negative ion LC/MS using the Bruker Esquire instrument has been very robust using a stainless steel sprayer. This instrument places electrical potential on the MS optics, leaving the sprayer at ground. Tests Agilent ion trap and QTOF instruments using the chip chromatographic interface have been very successful. The spray is stable and robust. The sprayer is at ground potential and the spray tip is made of polyimide. It has not been possible to achieve stable spray using a Qstar instrument using a silica sprayer. This instrument places the electrical potential on the spray tip. It appears that this configuration accentuates the extent to which electrochemical reactions result in clogging of the tip. In ongoing work, the utility of stainless, platinum, and polyimide tips will be compared for the Qstar and Orbitrap instruments at the MSR. The goal is to achieve robust performance in the negative mode for these instruments.
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