Simultaneous preconcentration and penta-elemental speciation analysis of Cr, As, Cd, Hg, and Pb by online solid-phase...

Species-specific toxic, metabolic, and bioavailable properties of commonly coexisting metal(loid)s-particularly Cr, As, Cd, Hg, and Pb-necessitate their speciation analysis. Because of the complexity and diversity in chemical form, concentration (from picograms to milligrams per liter), interactions, and sample matrix, multi-elemental speciation methods are preferred over traditional mono-elemental speciation methods. However, current multi-elemental speciation methods have primarily associated with only two metal(loid)s. Herein, we developed an efficient, sensitive, inexpensive, and green methodology for the simultaneous penta-elemental speciation analysis of Cr, As, Cd, Hg, and Pb using high-performance liquid chromatography combined with inductively coupled plasma mass spectrometry and online solid-phase extraction (SPE) preconcentration. Food samples were extracted with a mixture of 0.1 M HNO₃ and 5 mM _L-cysteine (Cys), chosen among 10 extractants for its good extraction efficiency, low noise, and minimal chromatographic interference. The proposed method offered a short analysis time (10 min for separation and 2 min for enrichment), excellent linearity (R² > 0.995), low detection limits (0.02 -0.12 μg L^-1 in SPE-free mode; 0.02 -3.2 ng L^-1 with online SPE), high precision (0.2 -2.4 %), and good recovery (81 -117 %) using an aqueous mobile phase of 5 mM tetrabutylammonium hydroxide + 5 mM Cys (pH 4.7). This demonstrates its good applicability to both food and water samples. Despite the incompatibility of Cr(VI) with As(III) and Cys, the proposed method excels in analytical, economic, and environmental aspects (maximizing the number of metal(loid)s within minimized analytical time using aqueous mobile phases), showing significant potential for a wide range of food, environmental, and biological samples.