A computerized system for potentiometric stripping analysis made o f commercially available components with corresponding software is described. Application t o the determination o f lead in wines and vinegars is also reported.
INTROD IJCTIONPotentiometric stripping analysis (I'SA) is a wellestablished technique for the determination o f several metals in biological materials [ 1-71, The technique, like anodic stripping voltammetry, consists o f a potentiostatic deposition step and a subsequent stripping step. However, in PSA, the electrodeposited metals are n o t stripped by a potential scan but are cliemically oxidized by a suitable oxidizing agent (that can be the oxygen naturally present in the sample) and the potential is monitored as a function of time.The main advantage o f PSA with respect t o other stripping techniques is that it is much less affected by organic electroactive species [ 1, 31 and measurements can be performed in biological matrices with little or no sample pretreatment. However, since any oxidant present in the sample solution can participate in the stripping process, samples need t o be deoxygenated or longer plating times should be used in order t o get useful analytical results. Hy using ;I computerized PSA system it has heen siiown [ 8, 91 that this problem can be overcome and many biological samples can be analyzed without deoxy genntion o f the sample and using very short electrolysis times. In this paper we describe a PSA computerized system, assembled with commercially available hardware, and operated under a very simple program written in Asyst language. Applications to analysis o f wines and vinegdrs are also described.* ASYST is 3 specilk software from Macmill:in softw:ire.' To whom corresponcleiice shottld be addressed.
EXPERTMENTAL
ReagentsHigh-purity reagents and deionized water were used. Standard solutions o f lead were prepared daily from a 1000 ppm stock solution specially prepared for atomic absorption spectroscopy (HIIH Chemicals 1,td.) containing 1.0 g/liter o f the element. Wines and vinegars were obtained from a local retailer. Vinegars were chosen to cover a wide range o f the Italian production. Samples 4 and 5 were aromatized vinegars.
InstrumentationAll measurements were performed by using the proposed computerized system consisting o f -Kadiometer ISS820 ion scanning system -Radiometer TTAHO titration assembly -Lab Master 20009 MI> converter, 12-bit and maximum conversion rate of 30 kHz (approximate price l1.S. $1900).-Microcomputer AT IRM-compatible, 640-kb KAM, equipped with mathematics coprocessor 80287, IHM enhanced color graphics card, 256-kb graphics memory, and high-resolution monitor. Serial plotter 7470-compatible A saturated calomel reference electrode (Kadiometer K4040), a platinum wire auxiliary electrode (Kadiometer P1312), and a glassy carbon working electrode (Kadiometer F3500) were also used. The coating o f the working electrode was done as was previously described 141 by performing 10 plating/stripping cycles with a solution containi...
