Effects of storage temperature and mercuric chloride on preservation of blood samples for later determination of ammonia-N.

Effects of chemical and physical preservation of blood on changes in ammonia concentration during storage were studied with samples containing init ial concentrations of .143, .316, .771, .816, and 1.308 mg ammonia-N per 100 ml blood. A saturated solution of mercuric chloride was added to the blood in amounts of 3.33, 5.00, 6.66, 8.33 or 10.00%. Deionized water was added to control samples in the same amounts as mercuric chloride. Samples were stored at 22, 5, or 2 0 C for 3, 5, 7 or 14 days. The ammonia concentration in the control samples stored for 7 days increased 1408, 86 and 22% when stored at 22, 5 or 2 0 C, respectively. Respective increases in samples stored with mercuric chloride were 44, 16 and 9%. There were no statistically significant differences among the ammonia attr ibutable to the various concentrations of mercuric chloride used. Blood stored with at least 6.66% mercuric chloride for 3 or 5 days showed essentially no increase in ammonia. Control samples stored at 2 0 C for 7 days did not differ from mercuric chloride-treated samples stored under similar conditions. However, at 14 days control samples stored at 2 0 C contained more ammonia than did mercuric chloride-treated samples. The relationship between initial concentration of ammonia and its change during storage was negative and significant. Samples with less initial ammonia changed most during storage. Ammonia concentration changed less in plasma than in whole blood when both were stored at 5 C. However, separating plasma from blood increased the initial blood ammonia 15 to 25%.