Title: Elimination of ionic interferences in the determination of sulphates in water using the lead-sensitive ion-selective electrode
Abstract: In the titration of sulphate ions with lead(II) perchlorate solution using a lead-sensitive electrode for end-point determination, the addition of 75%V/V of methanol permits titration of 10–5M samples. Under these conditions, a 200-fold excess of nitrate does not interfere, but chloride at this concentration introduces a small systematic error of 4%. Significant errors are caused by the presence of calcium, which co-precipitates as calcium sulphate with lead sulphate. In titrations carried out rapidly, the negative error increases with the amount of calcium and the true equilibrium may be obtained after a relatively long time. Increasing the ionic strength of the solution by addition of sodium perchlorate eliminates the interference by calcium, but for concentrations of sulphate below 10–4M it is advantageous to remove calcium by using a cation-exchange resin in the hydrogen form. The method has been applied successfully to the determination of sulphate in water.
Publication Year: 1976
Publication Date: 1976-01-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 16
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