Ultraviolet digestion

Agemian and Chau [55] have described an automated method for the determination of total dissolved mercury in fresh and saline waters by ultraviolet digestion and cold vapour atomic absorption spectroscopy. A flow-through ultraviolet digester is used to carry out photo-oxidation in the automated cold vapour atomic absorption spectrometric system. This removes the chloride interference. Work was carried out to check the ability of the technique to degrade seven particular organomercury compounds. The precision of the method at levels of 0.07 pg/1, 0.28 pg/1, and 0.55 pg/1 Hg was 6.0%, 3.8%, and 1.00%, respectively. The detection limit of the system is 0.02 pg/1. 

Achterberg, E.P. and C.M.G. van den Berg. 1994. In-line ultraviolet-digestion of natural water samples for trace metal determination using an automated voltammetric system. Anal. Chim. Acta 291 213-232. 

ASTM D7511-09e2, Standard test method for total cyanide by segmented flow injection analysis, in-line ultraviolet digestion and amperometric detection, ASTM International. 

Technology has been introduced for on-line estimation of the kappa number based on absorption of ultraviolet light (35). This breakthrough ia optical sensor technology permits closed-loop feedback control of digesters from on-line measurement of the kappa number. 

Figure 11.4 Analysis of in vitro synthesized RNAs. 32P-Radiolabeled RNAs (48 nucleotides) capped with m7Gp3G (A and C) or m27,3 °Gp3G (B and D) were digested with either RNase T2 (A and C) or RNase T2 plus tobacco acid pyrophosphatase (TAP) (B and D) followed by anion-exchange HPLC on a Partisil 10SAX/25 column as described in the text. Fractions of 1 ml were collected, and the Cerenkov radiation was determined. The elution times of the following standard compounds, detected by ultraviolet (UV) absorption, are indicated with arrows 3,-CMP (Cp), S UMP (Up), 37-AMP (Ap), 3 -GMP (Gp), 3, 5 -m7GDP (pm7Gp), 3, 5 -GDP (pGp), 5 -GDP (p2G), 5 -GTP (p3G), and guanosine-SCtetraphosphate (P4G).

II) complexes. This method was also successfully applied to chemically derivatized GAGs that cannot be depolymerized by enzymes [62]. Similarly, capillary electrophoresis (CE) can be used for digested GAGs that are then detected by ultraviolet spectroscopy or mass spectrometry. Complexation of GAGs using copper (II) ions improved the sensitivity. However, complete separation of intact GAGs was not feasible by CE and most methods still rely on enzymatic or chemical depolymerization prior to analysis [46]. 

This chapter presents an overview of sample treatment procedures [e.g., decomposition, digestion, mineralization, oxidation, ultraviolet (UV) decomposition, and ozonation] and discusses a range of analytical techniques for the mineralization of natural aquatic systems. Other samples, such as effluents and sewage sludge, are beyond the scope of this contribution and will not be discussed here. 

The FE method does suffer from the disadvantage that comparatively small amounts of C have to be measured in 0.5 M K2S04. Vance et al. (1987) used a dichromate digestion method. However, C can be more conveniently determined by an automated system using persuflate and ultraviolet (UV) oxidation, which gives essentially the same results but more rapidly and easily (Wu et al. 1990). 

As already described the enzyme-modified 7S protein retains a high molecular weight like the native protein it is excluded by Bio-Gel P-150 which has an exclusion limit of 150,000 daltons. The specificity of rennin is such that it is easy to control and limit the extent of digestion. When the enzyme action is monitored by ultraviolet absorption it is apparent that the rennin action is quite different from that obtained with an enzyme such as trypsin (Figure 1). Thus the UV difference spectrum for the rennin-modified protein shows an initial unfolding of the 7S protein chains as indicated by a negative peak at 236 nm. As rennin action continued this negative peak was replaced by a positive peak at about 237 nm characteristic of an ordered secondary structure. 

Fig. 2.1. Nucleotide fractionation. A sample of p2 phage RNA uniformly labelled with and the pyrimidines labelled with was digested with alkali ( 2.1.1) and separated by column chromatography on Dowex 50 formate eluted with 0.25 M ammonium formate pH 4.1. The ultraviolet transmission graph is traced from the record of a Uvicord I ultraviolet monitor output Radioactivities were measured by dissolving the samples in a scintillation cocktail and counting in a liquid scintillation counter. The peaks were identified from their ultraviolet spectra.

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