Chromatographic and mass spectrometric characterization of a landfill leachate and an industrial wastewater
The purpose of this research was to apply analytical techniques to identify and investigate specific organic compounds present in a municipal landfill leachate and an industrial wastewater. Accurate characterization of wastewaters can assist environmental engineers and scientists in the design of treatment systems. Several extraction and analytical techniques were utilized for the analysis of components in complex environmental samples focusing on nonvolatile or thermally labile compounds.
Of the extraction procedures evaluated, C₁₈ solid phase extraction was found most useful in preparing the samples for analysis. Recoveries ranged from 48% for a benzenesulfonamide to 96% for 2,4-dinitrotoluene. Liquid chromatography/mass spectrometry (LC/MS) techniques were utilized in conjunction with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography with a diode array detector (LC/DAD), to identify specific organic chemicals in the samples.
GC/MS analysis of the leachate confirmed the presence of two benzenesulfonamides and two phthalate esters. Several other components were detected, but not identified. A significant number of components were detected by LC/MS that were not detected by GC/MS. Thermospray LC/MS results provided positive and negative ionization spectra which were useful for identifying standards and providing molecular weight information.
GC/MS, LC/DAD and LC/MS analysis of the industrial wastewater confirmed the presence of 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, diphenylamine, and dibutyl phthalate. GC/MS analysis also confirmed the presence of 4-nitro-2-aminotoluene. Tentative identification of methylnitrobenzene, dinitrobenzene, aminonitrobenzaldehyde, and a dinitrotoluene isomer was made by GC/MS while two components remained unidentified. LC/DAD analysis also confirmed the presence of dioctyl phthalate, aminobiphenyl and a diphenylamine impurity while ten components were not identified. LC/MS results suggested the presence of a dinitrotoluene isomer, a diphenylamine dimer, N-nitrosodiphenylamine, methylnitrobenzenamine and dioctyl phthalate, while ten other components remained unidentified. Thermospray has severe limitations in its ability to identify unknown constituents. However, the application of the methods explored in this work to monitor the effectiveness of wastewater treatment is warranted.