Abstract:

A novel direct sampling method to determine cadmium in beverages by solid sampling electrothermal
vaporization atomic fluorescence spectrometry (SS-ETV-AFS) was established, where a tungsten coil as a Cd trap was used
to remove matrix interferences and foam graphite as an electrothermal vaporizer and a sample boat. In the present
study, 10 μL sample was loaded onto a sample boat, and then vaporized with 70 W for 30 s after being ashed
wi th 100 W for 30 s (natural spring water) or 50 s (beverages), using Ar/H2 (9:1) as the carrier gas with a flow
rate of 600 mL/min. Results showed that the calibration curve for Cd had good linearity (from 0 to 5 ng), and a correlation
coefficient (r) was more than 0.998; the recovery rates for Cd in 10 kinds of beverages were 92.2%-111.8%. The detection
limit was 0.04 μg/L, and the relative standard deviations (RSD) were less than 10%. This method is simple, sensitive,
fast (the whole analytical process including sample pretreatment can be completed within 3 min) and suitable for in-field
determination of ultra-trace amounts of Cd in beverages.

Key words: direct sampling, tungsten coil trapping, electrothermal vaporization (ETV), atomic fluorescence spectrometry (AFS), beverages, ultra-trace cadmium