Rapid and Portable Detection of Hg and Cd in Grain Samples Based on Novel Catalytic Pyrolysis Composite Trap Coupled with Miniature Atomic Absorption Spectrometry

Abstract

As toxic metals, Hg and Cd are a concern for food safety and human health; their rapid and portable analysis is still a challenge. A portable and rapid Hg–Cd analyzer constructed from a metal–ceramic heater (MCH)-based electrothermal vaporizer (ETV), an on-line catalytic pyrolysis furnace (CPF), a composite Pt/Ni trap, and a homemade miniature atomic absorption spectrometer (AAS) was proposed for grain analysis in this work. To enhance sensitivity, a new folded light path was designed for simultaneous Hg and Cd analysis using charge coupled device (CCD) in AAS. To eliminate the grain matrix interference, a catalytic pyrolysis furnace with aluminum oxide fillers was utilized to couple with a composite Pt/Ni trap. The method limits of detection (LODs) were 1.1 μg/kg and 0.3 μg/kg for Hg and Cd using a 20 mg grain sample, fulfilling the real sample analysis to monitor the grain contamination quickly; linearity R2 > 0.995 was reached only using standard solution calibration, indicating the sample was free of grain matrix interference. The favorable analytical accuracy and precision were validated by analyzing real and certified reference material (CRM) grains with recoveries of 97–103% and 96–111% for Hg and Cd, respectively. The total analysis time was less than 5 min without sample digestion or use of any chemicals, and the instrumental size and power consumption were <14 kg and 270 W, respectively. Compared with other rapid methods, this newly designed Hg–Cd analyzer is proven to be simple, portable, and robust and is, thus, suitable to quickly monitor Hg and Cd contamination in the field to protect grain and food safety.

Atomic spectrometry update: review of advances in the analysis of clinical and biological materials, foods and beverages

“…Liu and co-workers 122 were concerned with the potential to achieve on-site measurements of Cd and Hg in grain samples, to fulfil the need for rapid analysis of these staple foods and warrant their safety for human consumption. To this aim they designed a portable instrument, based on a metal–ceramic heater for ETV, an on-line catalytic pyrolysis furnace with aluminum oxide fillers, a composite Pt/Ni trap, and a miniature AA spectrometer, including a charge coupled device to achieve the simultaneous determination of the two elements.…”

“…The ability to carry out analysis in the field is particularly useful for food production and safety, but often there is a compromise with detectability with portable equipment. Utilising catalytic pyrolysis followed by miniature AAS, Liu et al 122 were able to demonstrate LODs of 1.1 μg kg −1 and 0.3 μg kg −1 for Hg and Cd using a 20 mg grain sample within 5 min. With safety limits of 100 μg kg −1 for Cd and 20 μg kg −1 for Hg, this technology is sufficient to satisfy these demands.…”