Sodium, potassium, ammonium and ammonia

OTHER ION (AND AMMONIA) STUDIES IN SERUM, PLASMA AND BLOOD Sodium, potassium, ammonium and ammonia 

The possibility of alkali metal ion-binding can be dismissed on the basis of sodium and potassium ion studies [26,36,139—145]. Glass electrode studies on serum indicate a correlation with flame photometer sodium levels amounting to no sodium binding [2,143]. One premise for this is the assumption of serum water content being 96 per cent by volume giving a mean /nb of 0.747 com- 

On the matter of correlations between electrode and spectroscopic data, there can be some bias but while electrode potassium values are very slightly higher in one study [145], it is the flame photometer potassium data that are higher in another [148]. The bias in the second example [148] was attributed to faulty electrode calibration. 

Nitrogen occurs in various forms in biological fluids and certain electrodes are suitable for at least three of these, namely, ammonium, ammonia, proteins (including enzymes) and urea. By way of illustration of possible applications, direct measurement of ammonia in serum and blood is clinically interesting since high levels are encountered in hepatic coma and may also indicate the nature of gastro-intestinal haemorrhage in accident cases. The ammonia gas electrode [149] and the air-gap electrode [150] are suitable for this purpose. 

On interferences of the ammonia electrode, the effect of amines like methyl-amine [151] and trimethylamine [152] is quite noticeable and a simple correction in the latter case was made by adding a 1 1 formalin sample to eliminate ammonia and obtain the trimethylamine reading [152]. Amphetamines and antihistamines have no effect on the electrode [151]. 

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