Some ionic and dilution effects in the measurement of urinary oestrogens in pregnancy

The estimation of oestrogen in aqueous solutions and pregnancy urines using an automated procedure is affected by the presence of certain ions, and by dilution. These effects have been studied by calculating regression equations from the values obtained with urines to which ions have been added with and without urine dilution. The results suggest that the ionic effect is chemical rather than physical and that there is no advantage in including a predilution step in the analysis. Other means of removing the ionic effects have so far proved unsuccessful.