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

A comparison of conventional stripping potentiometry (SP), and SP with medi um exchange for the determination of total copper in white wine has been ca rried out. Medium exchange proved to be beneficial for the longer-term stab ility of the mercury film, provided mercury(II) was included in the enrichm ent solution. With an enrichment solution containing 1.0M HCl and 20 mu g m l(-1) mercury chloride, and 4.0 M ammonium acetate as the stripping solutio n, there is a high degree of correlation between the results obtained by me dium exchange SP and inductively coupled plasma-atomic emission spectroscop y (ICP-AES) (r=0.9964). Four-fold analyses of the wine sample with single p oint standard addition calibration allowed the one him to be used for 32 en richment-stripping cycles. With conventional SP, in which a high concentrat ion of mercury(II) in the sample matrix is required to achieve fast strippi ng, significant over-estimation of the copper concentration was observed. T he advantages of medium exchange SP compared to conventional SP are identif ied. (C) 2000 Elsevier Science B.V. All rights reserved.