Determination of total copper in white wine by stripping potentiometry utilising medium exchange

A comparison of conventional stripping potentiometry (SP), and SP with medium exchange for the determination of total copper in white wine has been carried out. Medium exchange proved to be beneficial for the longer-term stability of the mercury film, provided mercury(II) was included in the enrichment solution. With an enrichment solution containing 1.0M HCl and 20 mu g ml(-1) mercury chloride, and 4.0 M ammonium acetate as the stripping solution, there is a high degree of correlation between the results obtained by medium exchange SP and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) (r=0.9964). Four-fold analyses of the wine sample with single point standard addition calibration allowed the one him to be used for 32 enrichment-stripping cycles. With conventional SP, in which a high concentration of mercury(II) in the sample matrix is required to achieve fast stripping, significant over-estimation of the copper concentration was observed. The advantages of medium exchange SP compared to conventional SP are identified. (C) 2000 Elsevier Science B.V. All rights reserved.