Determinação de íons zinco em óleos lubrificantes por voltametria de redissolução anódica

Abstract

The determination of Zn ions in automotive new lubricating oils (minerals and synthetic), used oil and in addictive by means of concentrated HCl and H2O2 aided by an ultrassom bath with heating extraction with was proposed. Íons Zn determination is madenecessary due to the same being one of the representatives of the main ones addictive in lubricating oils.In order to determine the extraction conditions multivariates desing were made (factorial fractional, full factorial and by central composition), being defined a 90°C as themaximum experimental temperature and a 60 minutes time, using 2.00 mL of HCl and 2.00 mL of H2O2 (30% w/v). After the extraction, Zn was quantified in the aqueous phase by anodic stripping voltammetry using the electrode of pending mercury drop as work electrode. The voltammetric analyses were reproducible and they presented a selectivity and sensibility in a small time of analysis (about 50 s). It was obtained a limit of detection of 2.95 mg Kg-1 and a limit of determination of 4.49 mg Kg-1 for a time deposition of 30s. For the procedure validation analyses by ICP-OES following the norm ASTM D4951 were made. There were no significant differences among the methodologies by comparing results at the level of 95% of trust for the test-T. A recovery rehearsal in sevenreplicates was made, proving the effectiveness of the extraction. The results understood between 98 and 103%. An analysis of a certified sample reached an error in the precision of 1.5%, rendering the validation of the method.