Spectrophotometric determination with azomethine

2 Spectrophotometric determination with azomethine-H General remarks 

In buffered solution, borate ions react with azomethine-H to produce a 

If the water sample under analysis is turbid, filtration must be carried out. 

If interference occurs, the boron can either be separated by distillation 

Dissolve 1.0 g of the sodium salt of azomethine-H together with 3.0 g of 

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F. J. Krug, J. Mortatti, L. C. R. Pessenda, E. A. G. Zagatto, and H. Bergamin F-, Flow Injection Spectrophotometric Determination of Boron in Plant Material with Azomethine-H. Anal. Chim. Acta, 125 (1981) 29. 

L. Sun, Z. Sun, L. Li, and Z. Fang, The Determination of Soil Available Boron with Azomethine-H by a Flow Injection Spectrophotometric Method [in Chinese]. Turang Tongbao, 5 (1983) 41. 

Kiss [8] examined various techniques for the efficient separation and preconcentration of boron from marine sediments. Alkaline fusion with potassium carbonate was used to render boron reactive, even in the most resistant silicate minerals. Fusion cakes were extracted with water and borate was isolated by Amberlite XE-243 boron-selective resin. Borate was determined spectrophotometrically, following elution with 2 mol L 1 hydrochloric acid. Either the carminic acid complex (620nm), formed in sulphuric acid (94%) or sulphuric acetic acid (1 4), or the azomethine hydrogen ion association complex (415nm) formed at pH5.2, were used for borate measurement. 

A kinetic-photometric method for the determination of EDTA, zinc, and bismuth by interchange reactions of azomethine groups, was reported by Rios and Valcarcel [26], The method involves the in situ formation of the Ni(II) complex with 6-methylpicolinaldehyde thiosemicarbazone when Ni(II), 6-methylpicolinaldazine, and thiosemcarbazide are mixed at pH 4.5. The reaction was monitored spectrophotometrically at 396 nm. 

Once in solution, the preferred method for measurement of boron is inductively coupled plasma atomic emission spectroscopy (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS). The most widely used nonspectrophotometric method for analysis of boron is probably ICP-MS because it uses a small volume of sample, is fast, and can detect boron concentrations down to 0.15 pgL . When expensive ICP equipment is not available, colorimetric or spectrophotometric methods can be used. However, these methods are often subject to interference (e.g., nitrate, chloride, fluoride), and thus must be used with caution. Azomethine-H has been used to determine boron in environmental samples (Lopez et al. 1993), especially water samples. Another simple, sensitive spectrophotometric method uses Alizarin Red S (Garcia-Campana et al. 1992). 

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