A surface plasmon resonance sensing method for determining captopril based on in situ formation of silver nanoparticles using ascorbic acid

• A new spectrophotometric method for sensitive determination of captopril by AgNPs plasmon.
• Stable and dispersed AgNPs with intensified plasmon peak were synthesized in situ.
• First time ascorbic acid was used as reducer for in situ formation of AgNPs in sensing method.
• Detection limit is better than other methods based on spectrophotometric captopril detection.

A new method has been proposed to sensitive detection of captopril based on surface plasmon resonance band of silver nanoparticles (AgNPs). The stable and well-dispersed AgNPs with strong plasmon resonance signal were synthesized in situ using a simple and rapid procedure by applying ascorbic acid as reducer and sodium dodecyl sulfate as stabilizer, at room temperature. It was found that, the decreasing of AgNPs plasmon absorbance is proportional to the concentration of captopril which allows the spectrophotometric sensing of this compound. The presented method is capable of determining captopril over a range of 0.20–2.75 μmol L−1 with a limit of detection 0.07 μmol L−1. The relative standard deviation for eight replicate measurements of 1.00 and 2.50 μmol L−1 of captopril was 2.37% and 1.02%, respectively. The method was applied to the determination of captopril in pharmaceutical formulations with satisfactory results, which were in agreement with those of the official method.

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