Magnetic solid-phase extraction and a portable photocolourimeter using a multi-colour light emitting diode for on-site determination of nitrite

• Published in: Microchemical journal 2020-01, Vol.152, p.104344, Article 104344
• Main Authors: Khoshmaram, Leila, Saadati, Masoud, Sadeghi, Fatemeh
• Format: Article
• Language: English
• Subjects: Homemade photometer; Magnetic solid phase extraction; Nitrite; On-site determination; Water samples
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2019.104344

•A novel method was developed for on-site determination of trace amount of nitrite.•It is based on a combination of MSPE with a LED-based portable photometer.•Graphene-based magnetic nanocomposite was chosen as the adsorbent in MSPE technique.•The proposed method provides good RSDs, high enhancement factor and good recovery.•Nitrite was determined successfully in atmospheric liquids and surface water. In this study, a new, simple, cheap, fast method for on-site determination of trace amount of nitrite in atmospheric liquids and surface water is suggested. The proposed method is based on a combination of magnetic solid phase extraction with a designed portable photometer based on light-emitting diodes. The colour reaction of nitrite was carried out with 4-nitroaniline in acidic medium and then coupled with naphth-1-ol in alkaline medium to form an azo product. The reaction and extraction conditions (e.g., acidity for diazotization and alkalinity for naphth-1-ol coupling, and other reagent concentrations, amount of sorbent, desorption solvent type and volume, etc.) were optimized. Under the optimal conditions, the calibration graph was linear in the range of 0.01–0.3 mg  L−1 with the limit of detection (LOD) of 0.0013 mg L−1. The enhancement factor was about 110. Relative standard deviations (RSDs) for the extraction of 0.03 and 0.1 mg L−1 of nitrite were obtained 2.49% and 5.34% for five replicates, respectively. The proposed method was able to analyse nitrite ion in water samples with satisfactory recovery ranged from 87% to 103%.