Date of Award
Masters of Science (Research)
Magnesium is quantitatively the most important intracellular divalent cation (4), and has been found to serve in a wide range of enzymatic reactions (2). Studies have shown that up to ten percent of hospital patients may have hypomagnesaemia (6).
Atomic absorption spectrophotometry (AAS) under highly specified conditions is the de facto reference method for magnesium measurement but only about ten per cent of laboratories routinely use this method (4). This is because AAS is time-consuming, requires specialised equipment and a certain level of expertise, and may be hazardous due to the use of inflammable gases. Colourimetric methods e.g. calmagite are the most commonly used methods for magnesium measurement in the clinical laboratory. These depend on selective binding of magnesium with a number of metallochromic indicators. However, the specificity of these is disputed (4). Enzymatic methods offer the advantage of specificity with the convenience of automation on a clinical analyser.
The pyruvate kinase (EC 188.8.131.52) method for the measurement of magnesium was optimised and automated for use on the Olympus AU640 clinical analyser. The method demonstrated a clear correlation with the calmagite method, r = 0.9876. Analytical recovery and comparison with external quality control results were excellent. Sensitivity (detection limit = 0.033 mmol/l) and analytical range (up to 3.2 mmol/l) were evaluated. The method was free from interference by calcium and lithium. Manganese (at ten times the normal serum level) and lipaemia (up to 8 g/l) showed no interference. A CV of 1.7% was found for intra-run precision. A CV of between three and four percent was obtained for inter-batch precision when the reagents were kept on-board the analyser for five days without recalibration. In practice the stability of working reagent one was found to be three days.
Murphy, Joseph, "An Enzymatic Method For The Measurement of Magnesium" (2001). Theses [online].
Available at: https://sword.cit.ie/allthe/624