Analysis of Nitroaromatics: A Comparison Between Gas Chromatography, Liquid Chromatography and their Hyphenation with Solid Phase Micro-Extraction

A major class of nitro-explosives being used in military and commercial purposes belongs to organic compounds containing nitro (NO2) groups like nitrobenzene, nitrotoluenes, and nitramines. Apart from being energetic materials, these substances are inherently toxic to human beings. These substances may find their way into different environmental matrices from the site of their military or commercial applications. They are present in nature at ultra-trace levels. Chromatographic techniques have been widely used for the detection and quantification of nitro-explosives from various environmental matrices. The current study involves a comparison of the performance of liquid and gas chromatography with and without pre-concentration techniques like Solid Phase Micro-extraction (SPME) to detect ultra-trace levels nitrobenzene and nitrotoluenes in water. The addition of SPME to chromatographic techniques significantly improves the quality of the analysis in terms of ease and sensitivity. Both SPME-HPLC and SPME-GC are equally competent techniques for the analysis of nitroaromatic explosives from water. Detection limits were improved by upto 5 orders of magnitude by these methods. The methodology for determining nitroaromatic explosives in water samples has been optimized and validated after trying four different methods and comparing their performance. GC and HPLC techniques used alone cannot be sensitive enough to detect these compounds at ultra-trace levels. Both SPME-HPLC-UV and SPME-GC-FID are equally competent techniques. SPME method has been proved to be an excellent tool with no requirement of any tedious sample preparation and chemical processing of the samples.