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On-line complexation/preconcentration system for the determination of lead in wine by inductively coupled plasma optical emission spectrometry with ultrasonic nebulization
WUILLOUD, RODOLFO G.; GONZÁLEZ, ALFREDO; MARCHEVSKY, EDUARDO; OLSINA, ROBERTO A.; MARTINEZ, LUIS D.
Simposio; SIXTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY; 2000
Universidad de Concepción
The main sources of lead intake in humans are inhaled air, diet, and drinking water. The exposure level is strongly dependent on pollution, type of diet, country, and so forth. Therefore, the determination of lead in beverages samples is important. Lead contents in wine may vary within a broad range, however the reported permissible maximun levels of lead in wines are betwen 0.1 to 0.3 mg/L..The determination of low concentrations of lead in wine samples requires powerful techniques and only few techniques have sufficient sensitivity. If conventional inductively coupled plasma optical emission spectrometry (ICP-OES) is used, the low level of lead concentration in wine is not compatible with the determination limit of this technique. In order to achieve accurate, reliable and sensitive results, preconcentrations and separations are needed when the concentrations of analyte elements in the original material or the prepared solution are too low to be determined directly by ICP-OES.Preconcentration is an effective mean for extending the detection limits of ICP-OES methods. However, when practised manually in the batch mode, the operations are usually too tedious to be compatible with the ICP-OES measurements. This situation has been improved significantly utilizing flow injection (FI) associated with ICP-OES, such that the general drawbacks of batch preconcentration procedures have been largely eliminated, and currently on-line preconcentrations could be achieved almost as efficiently as a simple ICP-OES determination. In fact, up to now the most dramatic improvements achieved in FI-ICP-OES are in the field of on line preconcentration. On the other hand, the use of an ultrasonic nebulizer can provide a 5-50 fold improvement in detection limits.In order to be used as packing in preconcentration columns for FI, materials have to meet several requirements. XAD resins meet many of these requirements and have been used as supports for immobilisation of chelating agents and metal complexes.Quinolin-8-ol forms stable complexes with numerous metal ions, and is therefore a suitable reagent for lead preconcentration on a XAD resin.In the present work, a method for preconcentration and determination of lead in wine samples using a microcolumn filled with a macroporous Amberlite XAD-16 resin is proposed. Lead was retained under the form of Pb-Quinolin-8-ol complex. The determination was performed using ICP-OES associated with an FI methodology and ultrasonic nebulization system. With the ultrasonic nebulization system the use of an additional ICP-OES hydride generation system was avoided, simplifying the whole measurement procedure.A total enhancement factor of 225 was obtained with respect to ICP-OES using pneumatic nebulization (15.0 for USN and 15.0 for column). The detection limit value for the preconcentration of 10 mL of wine sample was 0.04 ug/L of Pb with a relative standard deviation (RSD) of 2.5%, calculated with the peak heights obtained.The method was successfully applied to the determination of lead in wine samples.