An affinity ligand-matrix conjugate comprises the matrix and conjugated thereto by the group Z, a ligand having general formula (I): wherein one X is N and the other X is N, CCL or CCn; A1 and A2 are each independently O, S or N—R1 and R1 is H, C1-6 alkyl, C1-6 hydroxyalkyl, benzyl or β-phenylethyl; B1 and B2 are each independently an optionally substituted hydrocarbon linkage containing from 1 to 10 carbon atoms; D1 is H or a primary amino, secondary amino, tertiary amino, quaternary ammonium, imidazole, guanidine or amidino group; and D2 is a secondary amino, tertiary amino, quaternary ammonium, imadazole, guanidine or amidino group; or B2-D2 is —CHCOOH—(CH2)3-4—NH2; and p is 0 or 1. Such conjugates are useful for the separation, isolation, purification, characterization, identification or quantification of an endotoxin.