Irradiation, organic matter removed

Fig. 3.21. (a) Spectrum of a stored waveform inverse Fourier-transform (SWIFT) isolated ion at nominal mass 453 m/z. This molecule is present in dissolved organic matter at the Experimental Nutrient Removal wetland outflow, (b) Spectrum of this ion and resulting products after fragmentation by sustained off-resonance irradiation collision-induced dissociation. Formulae in parentheses represent compositions of lost fragments. From these fragments, unambiguous determination of the elemental composition of the precursor ion at 453 m/z is possible. 

The interference by organic matter, including organic surfactants and ligands, is eliminated by U V irradiation (2-3 h) of the seawater. Peak instability can occur when fi-eshly irradiated, acidified, seawater is analysed. This has been shown to be due to the formation of hypochlorite which produces a broad peak under that of copper (Achterberg and van den Berg, 1994). The hypochlorite is unstable at pH 8 and decays over a period of = 30 min causing the apparent copper peak instability. Its removal is virtually instantaneous when a reduc-tant (hydroxyl ammonium hydrochloride, final concentration 0.1 mmol/L) is added. 

Viruses and bacteria may be eliminated by chemical methods or by irradiation, and organic poisons may also be controlled. Inorganic matter must be removed by other means. 

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