Systematic study of several causes and effects due to absorbent blanks in determinations of one analyte

A systematic study is performed about several factors involved in the measu rements when a absorbent blank is used, as molar absorption coefficient of the: formed complex, absorbance of the blank at the measured wavelength, an d kind of spectrophotometer used (conventional double-beam or diode-array). It is proved that the usual methodology, measuring against reagent blank, produces less accurate measurements than those obtained against solvent bla nk. On the other hand, use of the H-Point standard additions method provide s always equal or better results than the best ones obtained at single wave lengths by using measurements against solvent bank, at the maximum of the f ormed complex. To test the methodology, calcium determination with Arsenate III, at basic pH, is studied at different peaks.