Application of light-absorption ratio variation approach as an optimum spectrophotometry to determination of Mn(II) in ng ml−1 level using a competitive replacement complexation

The light-absorption ratio variation approach (LARVA) which produces an outstandingly increasing of analytical sensitivity was applied to the quantitative detection of ultramicro amounts of Mn(II) by light-absorption spectrometry using the competitive replacement complexation among 1,5-di(2-hydroxy-5-sulfophenyl)-3-cyanoformazan (DSPCF), Zn(II) and Mn(II) in the presence of o-phenanthroline (OPTL). Not only masks OPTL foreign metal ions but also seriously sensitize the competitive complexation. All the binary and ternary complexes were characterized by the break point approach. Results have shown that the limit of detection (3δ) of Mn(II) is only 0.7 ng ml−1. This method has been applied to analysis of water quality with satisfactory results.