Detecting Sulfite Residue in Chinese Herbal Medicine


Chinese herbal medicines have become pervasive as a remedy for many ailments. In a recent study published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, a group of researchers explored using a novel technique for identifying sulfites and bisulfites in these herbal medicines (1).

The ancient Chinese medicine | Image Credit: © BrunoWeltmann -

The ancient Chinese medicine | Image Credit: © BrunoWeltmann -

Concerns have been rising over sulfur fumigation to preserve herbal remedies because it leaves behind potentially harmful residues, which can be toxic to people and in some cases, reduce the effectiveness of the treatment (1).

To combat this challenge, the research team introduced a ratiometric fluorescent probe designed to detect harmful sulfite residues. The probe, termed CPA, exploits the phenomenon of fluorescence resonance energy transfer (FRET) to achieve highly sensitive and specific detection of SO32−/HSO3 residues in medicinal samples (1).

Conventional methods for detecting sulfite residues rely on a single emission band; however, the CPA probe used a ratiometric approach that involved two distinct emission bands (1). The main benefit of this design is that instrumental noise and environmental concerns do not interfere with the probe. The CPA probe managed to have a reaction time of less than 15 s, coupled with an ultralow detection limit of 86 nM, which is significantly lower than more traditional methods of analysis (1).

The CPA probe's low cytotoxicity also opens the door for its use in living cell imaging experiments (1). This versatility marks a pivotal step towards understanding the impact of sulfite residues at a cellular level.As the global interest in herbal medicine continues to grow, developing better detection methods is of utmost importance.


(1) Chen, C.; Zhou, C.; Yang, W.; Hu, Y. A FRET-based ratiometric fluorescent probe for SO32− detection in Chinese medicine and living cells. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2023, 300, 122902. DOI: 10.1016/j.saa.2023.122902

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