Determination of Cd in food using an electrothermal vaporization capacitively coupled plasma microtorch optical emission microspectrometer: Compliance with European legislation and comparison with graphite furnace atomic absorption spectrometry

• Cd determination in food using a plasma microtorch and a microspectrometer.
• Optimization of Cd electrothermal vaporization from a small-sized Rh filament.
• Method validation according to the requirements in European legislation.
• Statistical comparison with GFAAS using the Bland and Altman test.

A precise, accurate and sensitive method based on electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry for Cd determination in various dietary products was developed. The instrumentation is inexpensive as it includes a low power (15 W) and low argon consumption (150 ml min−1) microplasma connected to a small-sized Rh electrothermal vaporization device and a low resolution microspectrometer. The sample was subjected to microwave assisted digestion in HNO3 – H2O2 mixture and Cd was determined in 10 μl sample without preconcentration. The standard addition method was used to compensate for the non-spectral matrix effects. The new method was in-house validated by analyzing certified reference materials and test dietary samples for which the Cd maximum level was established in Commission Regulation 488/2014/EU. The figures of merit of the proposed method and the experimental results were compared to those obtained in graphite furnace atomic absorption spectrometry as standardized method and discussed in relation with the requirements in the Commission Decision 2002/657/EC and Commission Regulations 2011/836/EU and 2007/333/EC. The limit of detection in fresh sample (0.001–0.009 mg kg−1), limit of quantification (0.002–0.018 mg kg−1), recovery (103 ± 15%), trueness (−3.0)–(+7.3)% and precision (0.8–14.0%) were similar to those found in the reference method and comply with the minimal criteria imposed to a method to be used in official laboratories for Cd determination in food. Precision for Cd determination close to maximum admitted levels or higher was of 0.8–6.0%, while for lower concentration in the range 4.0–14.0%. The Bland and Altman statistical test allowed successful evaluation of the new method as an alternative to the well established graphite-furnace atomic absorption spectrometry. The proposed method has analytical potential and is easy to run, while the full miniaturized instrumentation could be considered as a useful tool for the future as an alternative to the traditional instrumentation.