A novel and highly sensitive resonance scattering spectral assay for horseradish peroxidase using cationic surfactant

A novel and ultrasensitive resonance scattering (RS) spectral assay was proposed for detection of horseradish peroxidase (HRP) activity. It was based on that the HRP strongly catalyze H2O2 oxidation of excess I- to form I3-, the resulting I3- combined with four cationic surfactant (CS), including tetradecyl pyridinium bromide (TPB), cetyltrimethyl ammonium bromide (CTMA), cetylpyridinium chloride (CPCM) and tetradecyl dimethylbenzyl ammonium chloride (TDMBA) to produce association particles (TPB-I3)n, (CTMA-I3)m, (CPCM-I3)l and (TDMBA-I3)k, which exhibit a strongest resonance scattering peak at 478, 423, 538 and 491 nm, respectively. For the four systems of TPB, CPCM, CTMBA and TDMBA, the HRP activity determined was in the linear range of 0.004-5.6, 0.04-3.2, 0.04-8.0, 0.08-8.0 ng/mL, with a detection limit of 0.0034, 0.040, 0.033, 0.016 ng/mL, respectively. The TPB resonance scattering spectral assay was best and has been applied to the analysis of HRP in real samples, with satisfactory results.