Miniaturized ascorbic acid assay platform based on point discharge atomic emission spectrometry coupling with gold...

Miniaturized microplasma-based atomic emission spectrometry (AES) has been extensively used for element analysis in recent years due to the advantages of low power consumption, low gas consumption, relatively low manufacturing and running cost, and the potential for real-time and field analysis. However, few applications in bioassay detection have been reported based on microplasma AES systems because of their relatively low sensitivity and the absence of indirect analytical strategies. It is still a challenge to develop a simple, sensitive, and portable microplasma-based AES bioassay approach.

In this work, a portable analytical system was designed based on point discharge chemical vapor generation atomic emission spectrometry (PD-CVG-AES) coupling with gold filament enrichment. The detection of ascorbic acid (AA) was realized indirectly by means of the highly sensitive analysis of Hg²⁺. The measurement was based on Ag ⁺ can decrease the concentration of Hg²⁺ by forming Ag-Hg amalgam in the presence of the reductant SnCl₂, while AA can pre-reduce Ag ⁺ to Ag⁰, leading to the generation of silver nanoparticles (Ag NPs). The pre-reduce procedure can decrease the generation of Ag-Hg amalgam, resulting in the recovery of Hg²⁺ signal. The dissociative Hg²⁺ was further detected by PD-CVG-AES combination of gold filament enrichment, which significantly improved the detection sensitivity for both Hg²⁺ and AA. Under optimal conditions, the limit of detection (LOD) of AA is as low as 19 nM with a relative standard deviation (RSD, n = 5) of 0.7 %.

The developed novel analytical strategy obviously broadens the application of microplasma-based AES, and it is well demonstrated by the determination of AA in several traditional Chinese medicines (TCMs), offering a higher level of sensitivity compared to current AA detection techniques. It has potential for future application in point-of-care testing (POCT) assays.