Preparation and Development of new Sensitive Chromogenic Reagents for Metal Analysis

Abstract

During the research period Jan 1985 to June 1987, following 27 new chromogenic reagents were prepared and their structure determined with the aid of IR, UV, 1HNMR and mass spectroscopic techniques: 1. 2,3-Bis (2’-Pyridyl)-5,5,6,6-tetramethyl1-5, 6-dihydropyrazine (BPTDP). 2. 2,3-Bis(2’-(6’-methylpyridyl))-5,5,6,6-tetramethyl-5,6-dihydropyrazine (BMPTDP). 3. 2-phenyl-3-(2’-pyridyl)-5,5,6,6-tetramethyl-5,6-dihydropyrazine (BPTDP). 4. 2,3-Bis(2’-pyridyl)-5-phenyl-5,6-dihydropyrazine (BPPDP). 5. 2,3-Bis[2’-(6’-methylpyridyl)]-5-phenyl-5,6-dihydropyrazine (BPPDP). 6. 2-(2’-pyridyl)-3,5-diphenyl-5,6-dihydropyrazine (PDPDP). 7. 2,3-Bis(2’-pyridyl)-5,6-ethyl-6-methyl-5,6-dihydropyrazine (BPEMDP). 8. 2,3-Bis[2’(6’-methylpyridyl)]-5-ethyl-6-methyl-5,6-dihydropyrazine (BMPEMDP). 9. 2,3-Bis (2’-Pyridyl)-5-phenyl-6methyl-5,6-dihydropyrazine (BPPMDP). 10. 2,3-Bis[2’-(6’-methylpyridyl)]-5-phenyl-6-methyl-dihydropyrazine (BMPPMDP). 11. 2-(2’-pyridyl)-3,5-diphenyl-6-methyl-5,6-dihydropyrazine (PDMDP). 12. 2,3-Bis (2’-Pyridyl)-5-phenylpyrazine (BPPP). 13. 2,3-Bis(2’-(6’-methylpyridyl))-5-phenylpyrazine (BMPP). 14. 2-(2’-pyridyl)-3,5-diphenyl-pyrazine (PDPP). 15. 2,3-Bis(2’-pyridyl)-5-methyl-6-methylpyrazine (BPEMP). 16. 2,3-Bis[2’-(6’-methylpyridyl)]-5-ethyl-6-methylpyrazine (BMPEMP). 17. 2,3-Bis(2’-pyradyl)-5-phenyl-6-methylpyrazine (BPPMP). 18. 2,3-Bis(2’-(6’-methylpyridyl))-5-methylpyrazine (BMPPM). 19. 2-(2’-pyridyl)-3,5-diphenyl-6-methylpyrazine (BPDPMP). 20. 2-(2’pyridyl)-3-phenylquinoxaline (PPQ). 21. 2,3-Bis(2’-furyl)-5,6-dihydropyrazine (BFDP). 22. 2,3-Bis(2’-furyl)-5-methyl-5,6-dihydropyrazine (BPMDP). 23. 2,3-Bis(2’-furyl) d1-5,6-diphenyl-5,6-dihydropyrazine (BPDPDP). 24. 2,3-Bis(2’-furyl) pyrazine (BFP). 25. 2,3-Bis(2’-furyl)-5-methylpyrazine (BFMP). 26. 2,3-Bis(2’-furyl)-5,6-diphenylpyrazine (BFDPP). 27. 2,3-Bis(2’-furyl) quinoxaline (BFQ). The effect of methyl, ethyl, phenyl, furyl and pyridyl substitution titration in dihydropyrazine, pyrazine and quinoxaline ring on the reactions towards copper (I), Iron (11), Ruthenium (11), Cobalt (11) and Nickel (11) are investigated in terms of solution stability, molar absorptivity, wavelength of maximum absorbance and extractability from the aqueous to organic solvents. The reagents BPPDP, BPPP, PDPDP, PDPP, BPEMDP and BPPMDP, react with copper (1), Iron (11), Ruthenium (11), to form highly colored solution, where color development with Iron (11) and Copper (1) is immediate but ruthenium takes longer time. The color reactions of other reagents towards iron are sterically hindered because of the substituents adjacent to imine solution nitrogen atom. The calibration range for copper is within 0.5-0.7. Oμg./ml and iron (11) and copper (1) in mixture is 0.4-4 μg/ml iron and 0.5-5 μg/ml copper. The effect of diverse ions on the copper determination with the reagent BMPTDP has been investigated and the reagent is applied for quantitative determination of copper different water sample and human head hairs. The results are compared using independent spectrophotometric method using bathocuproine (2,9-dimethyl-4, 7-disphenyl-1, 10-phenanthroline) as complexing reagent. The result agrees with each other. Finally, the reaction of the furyl substituted dihydropyrazine and quinoxaline towards copper, iron, cobalt and nickel have been studied qualitatively and spectrophotometrically.