ANALYTICAL STUDIES OF NEW CHROMOGENIC REAGENTS: SYNTHESIS, EVALUATION, AND APPLICATIONS OF A WATER-SOLUBLE TRIAZINE, EVALUATION OF SOME QUINOLYLHYDRAZONES, AND APPLICATIONS OF SEVERAL HYDRAZONES TO TRACE METAL SIMULTANEOUS DETERMINATIONS EMPLOYING A METHOD FOR THE SELECTION OF OPTIMUM WAVELENGTHS

The analytical properties and applications of a number of new ferroin-type reagents were investigated in a series of studies.

A sulfonated form of 3-(4-phenyl-2-pyridyl)-5-phenyl-1,2,4-triazine, PPTS, was synthesized and found to be water-soluble and highly sensitive as an iron reagent (a = 33,300 M('-1) cm('-1) at 565 nm) and moderately sensitive as a copper reagent (a = 10,800 M('-1) cm('-1) at 454 nm). Applied as a reagent for the determination of iron in a variety of water and plant samples, PPTS gave good precision and accuracy. A method for the indirect determination of reducing agents, based on the use of PPTS, was developed which gave linear plots of absorbance versus concentration of reductant, although reduction was not stoichiometric in all cases.

A series of twenty-two hydrazones of 2-, 3-, and 8-hydrazino-quinoline were evaluated for their potential as chromogenic reagents for iron, cobalt, nickel, copper, and zinc. The 2- and 8-quinolylhydrazones formed chelates with most of the metals tested whereas the 3-quinolyl analogs formed chelates only with copper(I). Three of the 2-quinolylhydrazones proved to be most promising because of the high molar absorptivities of their iron(II), cobalt(II), nickel(II), and zinc(II) chelates.

Analytical methods were developed using 2,2'-dipyridyl-2-pyridylhydrazone, isoquinoline-3-aldehyde-pyrazinylhydrazone, and isoquinoline-3-aldehyde-2-pyridylhydrazone for the simultaneous determination of iron, cobalt, and nickel. Good precision and accuracy were obtained for the simultaneous determination of iron and cobalt using DPPH at pH 3.5 in the presence of manganese, nickel, and copper, and zinc. Similarly, reliable results were obtained for the simultaneous determination of iron, cobalt, and nickel in a variety of solutions using either IAPZH at pH 9 or IAPH at pH 11. Interferences from manganese, copper, and zinc, when IAPH was used at pH 11, were eliminated by masking with EDTA. All three simultaneous determinations employed analytical wavelengths that were selected by a method designed to identify those wavelengths that would lend optimum precision to the determination of each of the components. The results obtained confirmed the effectiveness of the wavelength selection method.