In the given chromatography, the negative charged compound used is:

This is ion exchange chromatography shown. In ion exchange chromatography: Either positive charge can be used on the column or negative charge. Carboxy group always gives negative charge because carboxy -COOH ionize to give COO-, E.g.CMC i.e. carboxy methyl cellulose is negatively charged. Amino group (NH2) always gives positive charge as NH2+ ionize to give NH3+. E.g. DEAE cellulose (Di Ethyl Amino Ethyl cellulose) positively charged. NOTE: The best method to measure HBA1C is ion-exchange chromatography.