Vortex-assisted liquid–liquid microextraction combined with spectrophotometry for the determination of trace nitrite in water samples

A vortex-assisted liquid–liquid microextraction (VALLME) method using isooctanol as extractant followed by spectrophotometry was developed for the extraction and determination of trace nitrite in water samples. The method is based on selective ion-pairing complex (I₃⁻ MG⁺) formation of triiodideanion I₃⁻ with cationic dye malachite green (MG) at pH 3.0, and its subsequent extraction in an organic solvent. The extracted organic solvent-rich phase is diluted with methanol, and its absorbance is measured against an analyte blank at 630 nm. The variables affecting VALLME efficiency were investigated, and a set of optimized conditions was obtained. Under the optimum conditions, the linear range of nitrite was from 1.0 to 100 ng mL⁻¹_. The relative standard deviations (n = 10) were 2.1–3.9% and the limit of detection was 0.5 ng mL⁻¹ and was successfully applied to the determination of nitrite in environmental water.