HPLC-UV platform for trace analysis of three isomeric mononitrophenols in water with chitin based solid phase extraction

Abstract

A method is described for simultaneous determination of trace levels of three isomeric mononitrophenols (MNPs) in environmental water samples using chitin (cheap, effective, biocompatible, green and safe) based solid phase extraction and high-performance liquid chromatography-ultraviolet detection. Various parameters were investigated and optimized for extraction and enrichment of three MNPs, and chitin-MNP adsorption was investigated using SEM, FT-IR and Raman spectroscopy. Validation tests of spiked water samples showed good linearities for all three MNPs (R² = 0.9990–0.9999) over a wide concentration range of 0.001–1 μg mL⁻¹. Limits of detection (LODs) and quantification (LOQs) were measured at ng mL⁻¹ levels: 0.13 ng mL⁻¹ and 0.39 ng mL⁻¹ for 2-NP, 0.09 ng mL⁻¹ and 0.27 ng mL⁻¹ for 3-NP and 0.19 ng mL⁻¹ and 0.57 ng mL⁻¹ for 4-NP. Inter- and intra-day precision tests showed variations of 1.67–1.80%, 1.06–1.56%, and 1.14–1.62% for 2-NP, 3-NP, and 4-NP, respectively. Average recoveries were in the range of 56.70–97.51%, with relative standard deviations below 15%. The developed method was then applied to analyze 8 real environmental water samples. Moreover, 4-NP was the most frequently detected MNP at concentration levels of 0.749–0.947 μg mL⁻¹, followed by 2-NP. Furthermore, 3-NP was not detected in any studied real sample. The validated method is simple and economical, with adequate sensitivity for trace levels of three isomeric MNPs. This method could be adopted by water quality analysis laboratories and allows an easy expansion to other related nitrophenols (NP) in water matrices' analysis.