Novel nickel trap coupled with electrothermal vaporization for the direct solid-sampling analysis of cadmium in soil

In this study, a foamed nickel trap (NT) was first utilized as a gas-phase enrichment (GPE) material to preconcentrate Cd under ambient temperature and then release it by heating. This is the first time that 100% trapping of Cd could be achieved via on-line GPE following electrothermal vaporization (ETV) introduction. The solid-sampling ETV method coupled with NT was thus developed for the direct detection of Cd in soil samples via atomic fluorescence spectrometry (AFS) as a model detector. Due to the gaseous matrix separation and analyte enrichment caused by the NT, the detection limit (LOD) of Cd reached 0.035 ng g(-1) for a 20 mg sample size, and the relative standard deviations (RSDs) were within 4% for Cd standards and 6% for real soil samples, respectively, indicating favorable analytical sensitivity and precision. The measured Cd levels were consistent with the certified values of soil certified reference materials (CRMs) and those obtained by microwave digestion inductively coupled plasma mass spectrometry; furthermore, the recoveries were 95-106% for a series of real soil samples. The analysis time could be controlled within 5 min and allowed elimination of the acid digestion process. As a result, the proposed NT is an effective GPE tool with 100% Cd-trapping efficiency and only similar to 100 W power consumption, revealing its promising potential for the miniaturization and portability of direct solid-sampling analyzers in the future.

Automated summary

In this study, a foamed nickel trap was used as a gas-phase enrichment material to preconcentrate and release Cd. The developed method showed high sensitivity and precision for the direct detection of Cd in soil samples. It eliminated the need for acid digestion and has potential for miniaturization and portability in the future.