Water samples, fluorescence analyses

Figure 2. The spectral analysis of light collected by the fiber placed in a pH=7 phosphate-buffered distilled water sample. The spectriun shows the important interferences which must be eliminated to relate the fluorescence intensity to concentration.

Figure 11. Diagram of system used to carry out automated preconcentration and analysis of water samples. Detection accomplished with UV absorption and photochemical dehalogenation with subsequent fluorescence detection of the photochemical reaction products. (Reproduced with permission from reference 50. Copyright 1982 Vieweg.)...

Thomas and Sniatecki [51] also performed an analysis of trace amounts of arsenic species in natural waters using hydride generation IPC-ICP-MS. Six arsenic species were determined with detection limits in the range 1.0-3.0 fig l-1 and total arsenic was determined using hydride generation by atomic fluorescence detection. It was found that the predominant species present in bottled mineral water samples was always As(V) with very low levels of As(III). The authors described how the system required . .. further work using special chromatographic software. .. to improve the quantitative measurement at a natural level. ... 

LAB 11 Laboratory for analysis of unfiltered water samples, stream sediment and floodplain sediment samples. Ion chromatography (IC) is used for Cf, Br, N03% N02, P043, S042 and ion specific electrode (ISE) for F and Total Organic Carbon (TOC) in water. X-Ray fluorescence spectrometry (XRF) analyses for over 30 elements is used for stream sediment and floodplain sediment samples. To be nominated (suggestion British Geological Survey). 

Despite the potential for direct aqueous injection of water samples into reverse phase systems, there are very few cases where this is possible due to the low detection levels normally required for environmental analysis. Using direct aqueous injection and coulometric electrochemical detection, the analysis of phenol and chlorophenols and 2-mercaptobenzothiazole have been achieved at trace levels (methods with limits of detection for phenol 0.034 ngp and 0.8 pgl for mercaptobenzothiazole have been achieved). There is a potential for the use of direct aqueous injection for the analysis of phenol in effluents using fluorescence detection which would be expected to detect down to low mg T. Direct aqueous injection has been used in an automated system similar to that shown in Figure 11.1. The trace enrichment cartridge was replaced by a large sample loop (50 pi) and a coulometric electrochemical detector used instead of the UV detector. 

Aqueous organic carbon analyzers helped revolutionize humic studies during the last decade. Not only could organic carbon measurements be made quickly and accurately on any water sample, but organic carbon analysis, used as a monitoring detector like conductivity and fluorescence, opened a new dimension in experimental design and approaches. In conjunction with other methods, the amount and distribution of humic substances in water in relation to other carbon-containing compounds could be determined. 

A similar preconcentration process was developed by Lochmuller, Galbraith and Walter (41) for the analysis of water for trace metals. The membrane after equilibration with the water sample is in this case analyzed by proton induced X-ray emission. Claimed advantages of the latter technique are a wider range of applicability than neutron activation, easier applicability to rapid routine analysis than anodic stripping and greater sensitivity than conventional X-ray fluorescence spectroscopy. 

---