On-line slurry formation and nebulization for inductively coupled plasma atomic emission spectrometry. Multi-element analysis of cocoa and coffee powder samples

A simple on-line slurry formation and direct nebulization system for inductively coupled plasma atomic emission spectrometric multi-element analysis was developed. A laboratory made micro-chamber with a magnetic-stirrer was used for on-line stable slurry formation in a dispersant solution of 0.5% v/v Triton X-100 and 1% v/v HNO3. A Babington-type nebulizer combined with cyclonic-type spray chamber was adopted for on-line slurry nebulization and atomization. All critical parameters were studied and optimized. The performance of the system was demonstrated for Al, Ca, Co, Cr, Cu, Fe, Mg, Mn, Ni, and Zn determination in cocoa and coffee powder samples. The recommended particle size was <70 mu m and the slurry concentration was 0.6% m/v, while the working slurry concentration could be ranged from 0.3 to 3.3% m/v with proportional sensitivity. Excellent agreement was found between the standard addition calibration procedure and the calibration curves using simple aqueous standard solutions for almost all of the investigated elements. The reliability of the proposed method was confirmed by comparing it with FAAS and ETAAS wet digestion methods for the analysis of cocoa and coffee samples. No significant differences were observed between the two methods.