Page 177 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon

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Comment on possible reasons for the very noisy signals obtained and suggest how a lower detection
limit might be obtained.

B.2 Laboratory Exercises

Before carrying out any of the following laboratory exercises, the appropriate safety audits should be
performed. In particular, attention is drawn to the Control of Substances Hazardous to Health (COSHH)
regulations.

B.3 Operation and Optimization of an Atomic Absorption Spectrometer and Determination of
Magnesium in Synthetic Human Urine.

For a given spectrometer it will be necessary to refer to the manufacturer's handbook and instructions
for operation.

B.3.1 Introduction

Practically all magnesium in the human body is found intracellularly (98%), with bones, muscles and
the liver being the main sites of deposition. Of the magnesium ingested (10-20 mmol per day), two
thirds is excreted in the stool with the remainder being reabsorbed, the majority of which is excreted
through the kidneys which regulate magnesium concentration.

The biological activity of magnesium is manifold. It serves as an indicator for many enzyme reactions,
predominantly phosphate metabolism (e.g. as a co-factor in the phosphorylation of glucose). It also
plays a part in the regulation of the neuromuscular excitation process.

Atomic absorption spectrometry is the method of choice for clinical chemists, with serum usually being
analysed to determine magnesium concentration, although in this case synthetic urine is being analysed
to assess the amount of magnesium being processed by the kidneys.

B.3.2 Objectives

1 To optimize the instrumental conditions for the analysis of magnesium by atomic absorption
spectrometry.

2 To quantify magnesium in synthetic human urine using calibration standards.