Development of a complex-based flow injection spectrophotometric method for determination of the herbicide pinoxaden in environmental samples

Abstract

A flow injection (FI) spectrophotometric method for the determination of the herbicide pinoxaden (PXD) has been proposed. PXD was converted in alkaline media with hydroxylamine hydrochloride to the hydroxamate salt. The salt was reacted with iron(III) chloride, and the absorbance of the red colored tris iron hydroxamate complex was measured at 500 nm using a FI system. The method was found to be linear between 0.5 and 40 mg L⁻¹ with a molar absorptivity of 1.53 × 10⁴L mol⁻¹cm⁻¹. The limit of detection and limit of quantification were found to be 0.1 ± 0.01 mg L⁻¹ and 0.6 ± 0.05 mg L⁻¹, respectively. Any interference of fenoxaprop-p-ethyl (FE) was avoided by the separation of PXD by liquid chromatography with a mixture of dichloromethane and n-hexane (1 : 1) as eluent. The method was applied to the determination of PXD in soil, water, and wheat grains with percent recoveries of 98 ± 2, 100 ± 2, and 98 ± 5, respectively. Sample throughput of 60 samples per hour was achieved under optimized conditions.

Keywords:

• pinoxaden
• Fe(III) hydroxamate complex
• flow injection
• spectrophotometric analysis
• fenoxaprop-p-ethyl