Boletín de la Sociedad Chilena de Química
versión impresa ISSN 0366-1644
BRUHN, Carlos G. et al. DETERMINATION OF Cd IN MUSSELS AND NON-FAT MILK POWDER BY FLOW INJECTION - FLAME ATOMIC ABSORPTION SPECTROPHOTOMETRY (FI-FAAS) WITH ON-LINE EXTRACTION BY A CHELATING RESIN. Bol. Soc. Chil. Quím. [online]. 2002, vol.47, n.2, pp. 123-135. ISSN 0366-1644. doi: 10.4067/S0366-16442002000200008.
A simple low-cost FI-FAAS methodology was developed for determination of Cd traces in food samples using preconcentration by on-line extraction in a chelating resin, a strategy usually applied for analytical measurements in water samples. In the case of food samples, a more complex matrix medium, the pH of acid digested solutions (pH 1) was raised first to pH 3-5 off-line with 0.5 mol/L NH3, and then was on-line adjusted to pH 8.0 with ammonium acetate buffer (1.15 mol/L CH3COOH / 2.0 mol/L NH3) to proper retention of Cd as Cd-8-hydroxiquinoline complex, minimizing interferences. Cadmium was preconcentrated in a minicolumn filled with 8-hydroxiquinoline azo-immobilized on controlled-pore glass (80 mg). A multivariate approach was adopted to establish the main parameters involved in the FI system. Subsequently, the sample, eluent, and buffer flow rates were optimized using an univariate approach. An enrichment factor of 27 was achieved for 3.0 mL of reference solution and the sampling frequency was 63 h-1. The detection limit (3sBL / slope) was 0.7 and 0.4 mg/L for a preconcentration time of 30 and 60 s, respectively. The developed methodology was validated employing certified reference materials (Oyster tissue, Mussel, and Spiked skim milk powder) and the determined and certified values are in agreement (95% confidence level). The methodology was applied for trace levels determination of Cd in lyophilized mussel samples from the Chilean coast and non-fat milk powder, and a comparison made with graphite furnace electrothermal atomization (ETAAS) showed no statistically significant differences in results (95% confidence level)
Palabras clave : Flow injection; flame atomic absorption spectrophotometry; cadmium; chelating resin; food samples.