A Simple and Rapid Spectrophotometric Method for Nitrite Detection in Small Sample Volumes

Yudtapum Thipwimonmas,Kritsada Samoson,Adul Thiangchanya,Vacharachai Khunseeraksa,Warakorn Limbut,Kah Haw Chang,Janjira Jaidam,Ahmad Fahmi Lim Abdullah,Apichai Phonchai

doi:10.3390/chemosensors9070161

Yudtapum Thipwimonmas, Kritsada Samoson + Show 7 more

Open Access

https://doi.org/10.3390/chemosensors9070161

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Abstract

A simple, rapid, and environmentally-friendly spectrophotometric method for nitrite detection was developed. Detection was based on a redox reaction with iodide ions in an acidic condition. The reaction was evaluated by detecting the increase in absorbance of the colored product of iodine at 362 nm wavelength. To obtain a good spectrophotometric performance, the iodide ions concentration, hydrochloric acid concentration, and reaction time were optimized. In the optimal condition, the developed spectrophotometric method provided a linear range of 0.0625 to 4.00 mg L−1 (r = 0.9985), reaction time for 10 min, a limit of detection of 25 µg L−1, and a limit of quantitation of 85 µg L−1. This method showed good repeatability (RSD < 9.21%), high sample throughput (9 samples min−1), and good accuracy (recovery = 88 ± 2 to 99.5 ± 0.4%). The method has the potential to be used in crime scene investigations as a rapid screening test for gunshot residue detection via nitrite detection.

Highlights

The gunshot residue (GSR) is the product of primer detonation, gunpowder combustion, and emitted particles of cartridge, projectile, and gun barrel
The color of the mixture solution was changed from colorless to yellow, as observed by the naked eye. Such change was due to the oxidation of iodide ion (I− ) to iodine (I2 ) [34–36]
Pb2+ did not interfere with nitrite determination. These results suggested the applicability of the method in the determination of nitrite, in suspected GSR samples

Summary

Introduction

The gunshot residue (GSR) is the product of primer detonation, gunpowder combustion, and emitted particles of cartridge, projectile, and gun barrel. In routine forensic analysis, GSR is identified through morphological and elemental analysis using scanning electron microscopy coupled with energy dispersive X-ray analysis [6]. Inductively coupled plasma-mass spectrometry [7] and atomic absorption spectroscopy [8] were reported in analyzing GSR. These techniques had demonstrated good accuracy and high sensitivity; these techniques could be limited by their respective cost, time, availability, and accessibility of instrumentation, as well as the need for well-trained operators [9,10]. A fast, inexpensive, and simple screening technique for determining GSR could benefit the forensic science community prior to the application of specific confirmatory techniques

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