Representative chromatograms detected at λ = 267 nm. (A) a solution containing a mixture of zidovudine glucuronide (ZDVG), zidovudine (ZDV) and internal standard, 4-methylumbelliferone glucuronide (4MUG) at concentration of 150 μM. ZDVG, ZDV and 4MUG were eluted at 7.9, 9.9 and 13.1 min, respectively; (B) a HLM incubation matrix solution. No peaks were detected; (C) a HLM incubation assay in the absence of UDPGA. No metabolite (ZDVG) peak was detected whilst 4MUG was eluted at 13.1 min; (D) a HLM incubation assay in the presence of UDPGA. ZDVG and 4MUG were detected at 7.9 min and 13.1 min. (1) ZDVG; (2) ZDV; (3) 4MUG.