Wang R Y, Dienel G A
Laboratory of Cerebral Metabolism, NIMH, Bethesda, MD 20892.
Biotechniques. 1994 Jul;17(1):106, 108, 110 passim.
Suppressed conductivity detection, developed for use with ion chromatography, might be useful to assay specific activities of organic acids after metabolic labeling. Because the suppressor reduces background conductivity by acid-base neutralization and removal of ions from the eluent, it could influence recoveries and apparent retention times of labeled compounds. Elution times of 14C-labeled glucose and neutral amino acids, compounds not detected by conductivity, from the analytical column were found to be similar to those of lactate and acetate. When the suppressor was connected to the HPLC system in the recycle mode, the apparent elution times of amino acids increased and various organic acid fractions would be contaminated. When the suppressor was used in the external water mode, the labeled neutral amino acids and portions of acidic amino acids were recovered in the waste fraction; this indicated that recoveries of total 14C in the analyte fraction would be incomplete if the loss were not taken into account. Thus, the procedure to insert the suppressor into the system influences the apparent retention times and the recoveries of labeled amino acids in the analyte fraction; labeled metabolites not detected by conductivity can cause serious errors in specific activities of organic acids and should be removed from the sample prior to analysis.
为离子色谱法开发的抑制型电导检测法，可能有助于在代谢标记后测定有机酸的比活性。由于抑制器通过酸碱中和及从洗脱液中去除离子来降低背景电导，它可能会影响标记化合物的回收率和表观保留时间。发现分析柱上未通过电导检测的¹⁴C标记葡萄糖和中性氨基酸的洗脱时间与乳酸和乙酸的洗脱时间相似。当抑制器以循环模式连接到高效液相色谱系统时，氨基酸的表观洗脱时间会增加，并且各种有机酸馏分会受到污染。当抑制器以外部水模式使用时，标记的中性氨基酸和部分酸性氨基酸会在废液馏分中回收；这表明如果不考虑损失，分析物馏分中¹⁴C的总回收率将不完整。因此，将抑制器插入系统的操作会影响分析物馏分中标记氨基酸的表观保留时间和回收率；未通过电导检测的标记代谢物可能会导致有机酸比活性出现严重误差，并且在分析前应从样品中去除。
