Investigation of capillary electrophoresis-laser induced fluorescence as a tool in the characterization of sewage effluent for fluorescent acids: determination of salicylic acid

The investigation of emerging contaminant issues is a proactive effort in environmental analysis. As a part of this effort, sewage effluent is of current analytical interest because of the presence of pharmaceuticals and their metabolites and personal care products. The environmental impact of these components is still under investigation but their constant perfusion into receiving waters and their potential effect on biota is of concern. This paper examines a tool for the characterization of sewage effluent using capillary electrophoresis-laser induced fluorescence (CE-LIF) with a frequency-doubled laser operated in the ultraviolet (UV). Fluorescent acidic analytes are targeted because they present special problems for techniques such as gas chromatography-mass spectrometry (GC-MS) but are readily accessible to CE-LIF. As an example of the application of this tool, salicylic acid is determined near the 100 ng/L (7 x 10(-10) M) level in sewage effluent. Salicylic acid is a metabolite of various analgesics. Relatively stable in the environment, it is a common contaminant of municipal sewage systems. Salicylic acid was recovered from freshly collected samples of the effluent by liquid-liquid extraction. Confirmation of identity was by electron ionization GC-MS after conversion of the salicylic acid to the methyl ester by means of trimethylsilyldiazomethane. CE-LIF in the UV has revealed more than 50 individual peaks in the extract and a background response that suggests a large and indeterminate number of additional compounds are present. These data together with complementary techniques provide information on the complexity and components in these effluent streams.