Spectrophotometric Determination of Chromium (Iii) and Chromium(Vi) Using 2-[E)-[3-[(2-Hydroxybenzylidene) Amino]PhenylImino)Methyl]Phenol

ABSTRACT

The Schiff base ligand, 2-[(E)-[{3--[(2-hydroxybenzylidene)amino]phenyl}imino)methyl]phenol was synthesized by condensing 1,3-diaminobenzene and 2-hydroxybenzaldehyde in absolute ethanol. Its Cr(III) and Cr(VI) complexes were equally synthesized. The ligand was characterized via UV, IR and NMR spectroscopy, whereas the complexes were characterized based on UV and IR spectroscopy and conductivity values. Stoichiometric studies indicated 1:1 metal to ligand ratio for both complexes. Cr(III) complex absorbed at 1042.56 cm-1 υ(C-O), 532.37 cm-1 υ(Cr-N) and 607.60 cm-1 υ(Cr-O) while the Cr(VI) complex absorbed at 1182 cm-1 υ(C-O), 749.37 cm-1 υ(Cr-O) and 457 cm-1 for υ(Cr-N). Based on UV, IR and NMR studies, the ligand coordinated to the metals using the nitrogen and oxygen atoms. Spectrophotometric determination of the metals using the ligand was done at 368 nm for Cr(III) and 465 nm for Cr(VI).Optimum conditions for complexation and stability were studied and it was shown that optimum pH for Cr(III) and Cr(VI) were 13.0 and 2.0 respectively. Very few ions such as Co2+, Cu2+, Mn2+, Mg2+, Fe3+ and Zn2+ interfered with the determination. Beer’s law was obeyed between 0.02 to 0.14ppm for both metals. The method was successfully applied in the analysis of steel.

TABLE OF CONTENTS

Title page - - - - - - - - - - i

Approval - - - - - - - - - - ii

Declaration - - - - - - - - - - iii

Dedication - - - - - - - - - - iv

Acknowledgements - - - - - - - - - v

Abstract - - - - - - - - - - vi

Table of contents - - - - - - - - - vii

List of Tables - - - - - - - - - - xi

List of Figures- - - - - - - - - - xii

List of Schemes - - - - - - - - - xiii

CHAPTER ONE

1.0 INTRODUCTION - - - - - - - - 1

1.1 Spectrophotometry - - - - - - - - 1

1.1.1 Beer- lambert’s law - - - - - - - - 2

1.2 Schiff Base Ligands - - - - - - - - 4

1.2.1 Preparation of Schiff bases - - - - - - - 4

1.2.2 Uses of Schiff Bases - - - - - - - - 6

1.2.3 Biological Importance of Schiff Bases - - - - - 7

1.2.4 Schiff Base Metal Complexes- - - - - - - 8

1.3 Chromium - - - - - - - - - 9

1.3.1 Determination of Chromium - - - - - - - 9

1.3.2 Uses - - - - - - - - - - 10

1.4 Statement of the Problem - - - - - - - 11

1.5 Aims and Objectives - - - - - - - 12

CHAPTER TWO

2.0 LITERATURE REVIEW - - - - - - - - 14

2.1 Catalytic Spectrophotometric Determination of Chromium - - - 14

2.2 Spectrophotometric Determination Of Trace Level Chromium Using Bis (Salicylaldehyde) OrthophenyleneDiamine In Non-ionic Micellar Media - 14

2.3 Spectrophotometric Determination of Chromium(III) and chromium(VI) in sea water.- - - - - - - - - - 15

2.4 Determination of Hexavalent Chromium in drinking water by ion chromatography with post-column derivatization and UV-visible spectroscopic detection. - 15

2.5 Determination of Cr(VI) in environmental sample evaluating Cr(VI) impact in a contaminated area. - - - - - - - 16

2.6 Indirect Extraction - Spectrophotometric Determination of chromium.- - 17

2.7 Sensitivity Determination of Hexavalent chromium in drinking water - - 18

2.8 Determination of Dissolved Hexavalent Chromium in Drinking Water, Ground Water and Industrial Waste Water Effluents by Ion Chromatography- - - - 18

CHAPTER THREE

3.0 Experimental - - - - - - - - - 19

3.1 Apparatus - - - - - - - - - 19

3.2 Preparation of Stock Solution - - - - - - - 19

3.3 Preparation of Buffer Solutions- - - - - - - 20

3.4 Synthesis of the Ligand (HBAPP) - - - - - - 20

3.5 Synthesis of Chromium (III) and Chromium (VI) Complexes of HBAPP - 21

3.5.1 Determination of the Stoichiometry of the Complexes by Slope-Ratio Method. 22

3.6 General Procedure for the Complexation Studies - - - - 23

3.6.1 Effect of Time on the Formation of the Complexes - - - - 23

3.6.2 Effect of Temperature on the Formation of the Complexes - - - 23

3.6.3 Effect of Concentration of Reagent on the Formation of the Complexes - 23

3.6.4 Effect of pH on the Formation of the Complexes - - - - 23

3.6.5 Effect of Interfering Ions on the Formation of the Complexes - - - 23

3.6.6 Calibration Curve-Beer’s Law - - - - - - - 24

3.7 Determination of Chromium in Alloy - - - - - - 24

3.7.1 Determination of Chromium in Alloy with Flame Atomic Absorption Spectrophotometry - - - - - - - - 24

3.7.2 Determination of Chromium in Alloys with UV Spectrophotometry - - 24

CHAPTER FOUR

4.0 Results And Discussion - - - - - - - 26

4.1 Physical Characterization and Molar Conductivity Data of the Ligands and Its Cr(III) and Cr(VI) Complexes- - - - - - - 26

4.2 Spectroscopic Characterization Of The Ligand And Its Cr(III) And Cr(VI) Complexes. - - - - - - - - - 26

4.2.1 Electronic Spectral Data of the Ligand and Its Complexes - - 26

4.2.2 Infrared Spectra - - - - - - - - 27

4.2.3 1H and 13C NMR Spectra of the Ligand - - - - - 28

4.2.4 13C NMR - - - - - - - - - 29

4.2.5 APT (Attached Proton Test) - - - - - - - 29

4.3 Stiochiomery of the Complexes - - - - - - 30

4.3.1 Metal-Ligand Mole Ratio of Cr(III) Complex - - - - 30

4.3.2 Metal-Ligand Mole Ratio of Cr(VI) Complex - - - - 31

4.3.3 Molecular Formulae and Structures of the Ligand and Its Complexes - 33

4.4 Complexation Studies- - - - - - - - 35

4.4.1 Effect of Time on the formation of the Complexes - - - - 35

4.4.2 Effect of the concentration of the reagent on the formation of the complexes- 36

4.4.3 Effect of temperature on the formation of the complexes - - - 38

4.4.4 Effect of pH on the absorbance of the complexes - - - - 41

4.4.5 Effect of interfering ions on the formation of Cr(III) and Cr(VI) complexes - 42

4.5 Calibration curve for determination of Cr(III) and Cr(VI) complexes - 44

4.5.1 Cr(III) complex - - - - - - - - - 44

4.5.2 Cr(VI) complex- - - - - - - - - 45

4.6 Application using steel solution- - - - - - - 46

4.6.1 Determination of Cr(III) in the steel solution - - - - - 47

4.6.2 Determination of Cr(VI) in steel solution - - - - - 47

4.7 Conclusion - - - - - - - - - 47

4.8 Recommendation - - - - - - - - - 48

References - - - - - - - - - - 49

Appendix A - - - - - - - - - - 55

Appendix B - - - - - - - - - - 58