Standard Practice for Identification of Chemicals in Water by Fluorescence Spectroscopy
5.1 This practice is useful for detecting and identifying (or determining the absence of) 90 chemicals with relatively high fluorescence yields (see Table 1). Most commonly, this practice will be useful for distinguishing single fluorescent chemicals in solution, simple mixtures or single fluorescing chemicals in the presence of other nonfluorescing chemicals. Chemicals with high fluorescence yields tend to have aromatic rings, some heterocyclic rings or extended conjugated double-bond systems. Typical chemicals included on this list include aromatics, substituted aromatics such as phenols, polycyclic aromatic hydrocarbons (PAH’s), some pesticides such as DDT, polychlorinated biphenyls (PCB’s), some heterocyclics, and some esters, organic acids, and ketones.
5.2 With appropriate separatory techniques (HPLC, TLC, and column chromatography) and in some cases, special detection techniques (OMA’s and diode arrays), this practice can be used to determine these 90 chemicals even in complex mixtures containing a number of other fluorescing chemicals. With the use of appropriate excitation and emission wavelengths and prior generation of calibration curves, this practice could be used for quantitation of these chemicals over a broad linear range.
5.3 Fluorescence is appropriately a trace technique and at higher concentrations (greater than 10 to 100 ppm) spectral distortions usually due to self-absorption, or inner-filter effects but sometimes ascribed to fluorescence quenching, may be observed. These effects can usually be eliminated by diluting the solution. Detection limits can be lowered following identification by using broader slit widths, but this may result in spectral broadening and distortion.
5.4 This practice assumes the use of a corrected spectrofluorometer (that is, one capable of producing corrected fluorescence spectra). On an uncorrected instrument, peak shifts and spectral distortions and changes in peak ratios may be noted. An uncorrected spectrofluorometer can also be used if appropriate data is generated on the instrument to be used.
1.1 This practice allows for the identification of 90 chemicals that may be found in water or in surface layers on water. This practice is based on the use of room-temperature fluorescence spectra taken from lists developed by the U.S. Environmental Protection Agency and the U.S. Coast Guard (1). Ref (1) is the primary source for these spectra. This practice is also based on the assumption that such chemicals are either present in aqueous solution or are extracted from water into an appropriate solvent.2
1.2 Although many organic chemicals containing aromatic rings, heterocyclic rings, or extended conjugated double-bond systems have appreciable quantum yields of fluorescence, this practice is designed only for the specific compounds listed. If present in complex mixtures, preseparation by high-performance liquid chromatography (HPLC), column chromatography, or thin-layer chromatography (TLC) would probably be required.
1.3 If used with HPLC, this practice could be used for the identification of fluorescence spectra generated by optical multichannel analyzers (OMA) or diode-array detectors.
1.4 For simple mixtures, or in the presence of other nonfluorescing chemicals, separatory techniques might not be required. The excitation and emission maximum wavelengths listed in this practice could be used with standard fluorescence techniques (see Refs (2-6)) to quantitate these ninety chemicals once identification had been established. For such uses, generation of a calibration curve, to determine the linear range for use of fluorescence quantitation would be required for each chemical. Examination of solvent blanks to subtract or eliminate any fluorescence background would probably be required.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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