Flow Injection Spectrophotometric Determination of Fe(III) and V(V)
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FLOW INJECTION SPECTROPHOTOMETRIC DETERMINA TION OF Fe(III) AND V(V) INIS-SD-124 SD0000045 By Azza Mohammed Fath Elrahman A Thesis Submitted in Accordance with the Requirement for the Degree of Master of Chemistry in the University of Khartoum University of Khartoum Faculty of Science Dept. of Chemistry January 2000 31/ 39 Dedication To my beloved parents To Khalid Acknowledgment I would like to express my deepest gratitude to my supervisor Dr. Taj Elsir Abbas for his valuable guidance, helpful suggestions, directions and kind help. I also wish to record my thank to the Chemistry Department, Faculty of Science, University of Khartoum for providing the facilities that made it possible for this research to be performed. Finally, I wish to thank the National Centre for Research for financing this research. List of Contents Contents Page Dedication I Acknowledgment II List of contents Ill List of tables V List of figures VII Abstract (in English) IX Abstract (in Arabic) X Chapter One: Introduction 1.1 Hydroxyxanthene dyes 1 1.1.1 The 2,3, 7~trihydroxy-6-fluorone group 4 1.1.2 Application of hydroxyxanthene reagents 10 1.1 Micelle 16 1.2.1 Micelle characteristics 17 1.2.2 Micelle-substrate interactions 22 1.2.3 Micellar catalysis 22 1.2.4 The analytical utility of micelles 23 1.2.4.1 Electrochemical measurements 23 1.2.4.2 Micelle in spectrophotometry 24 1.2.4.2.1 Acid-base considerations 24 1.2.4.2.2 Micelle-ligand effects 25 1.2.4.2.3 Solubilization effects 25 1.2.4.2.4 Micelle in luminescence techniques 25 1.2.4.2.5 Other spectrophotometric methods 27 1.2.4.3 Micelle in analytical separation 28 1.3 Flow injection analysis (FIA) 29 1.3.1 Principles of flow injection analysis 29 43 Til 1.3.1 Principles of flow injection analysis 29 Research Objectives 43 Chapter Two: Experimental 2.1 Instruments 44 2.2 Chemicals 44 2.3 Synthesis of phenylfluorone (PHF) 44 2.3.1 Synthesis of hydroxyquinone triacetate (1,2,4-benzentriol triacetate) 44 2.3.2 Condensation of hydroxyquinone triacetate and benzaldehyde 45 2.3.3 Identification of PHF 45 2.4 Preparation of various working solutions 47 2.4.1 Standard metal ions solutions 47 2.4.2 Micelles solutions 47 2.4.3 Phenylfluorone solution 47 2.5 Establishing the conditions for the maximum absorbance of Phenylfluorone using batch technique 48 2.5.1 Investigation of the wavelength and absorbance of Phenylfluorone 48 2.5.2 Effect of micelles on the wavelength and absorbance of PHF complexes with Fe(III) and V(V) 52 2.6 Optimization of the flow injection conditions for Phenylfluorone 55 2.7 Calibration curves 63 2.8 Effect of foreign metal ions on the absorbance of Fe(III)-PHF and V(V)-PHF complexes 67 Chapter Three: Discussion i Discussion !. 69 Chapter Four: References and Appendices References 72 Appendices '. 78 IV List of Table Table No. Page Table 1. Effect of n-dodecylpyridinum bromide on the wavelength of PHF 48 Table 2. Effect of sodium n-dodecylsulphate on the wavelength of PHF 48 Table 3. Effect of n-hexadodecylpyridinum bromide on the absorbance OfPHF 49 Table 4. Effect of sodium n-dodecylsulphate on the absorbance of PHF 49 Table 5. Effect of n-hexadodecylpyridinum bromide on the wavelength Of Fe(IlI)- PHF and V(V)-PHF complexes 52 Table 6. Effect of sodium n-dodecylsulphate on the wavelength of Fe(lll)- PHF and V(V)-PHF complexes 52 Table 7. Effect of n-hexadodecylpyridinum bromide on the absorbance Of Fe(III)- PHF and V(V)-PHF complexes 53 Table 8. Effect of sodium n-dodecylsulphate on the absorbance of Fe(III)-PHF and V(V)-PHF complexes: 53 Table 9. Effect of n-hexadodecylpyridinum bromide as carrier on the absorbance of 25 ppm Fe(III)-PHF and 25 ppm V(V)-PHF complexes 55 Table 10. Effect of sodium n-dodecylsulphate as earner on the absorbance of 25 ppm Fe(III)-PHF and 25 ppm V(V)-PHF complexes 57 Table 11. Effect of H2O as carrier on the absorbance of 25 ppm Fe(IIl)- PHF and 25 ppm V(V)-PHF complexes and different concentrations on n-hexadodecylpyridinum bromide 59 V Table 12. Effect of H2O as carrier on the absorbance of 25 ppm Fe(IIT)-PHF and 25 ppm V(V)-PHF complexes and different concentrations of sodium n-dodecylsulphate 59 Table 13. Calibration curve for Fe(IlT)-PHF using lxl0'6M PHF and H2O as carrier 63 Table 14. Calibration "curve for V(V)-PHF using lxl0"6M PHF and H2O as carrier 65 Table 15. Effect of foreign metal ions on the absorbance of 15 ppm Fe(III)-PHF complex 67 Table 16. Effect of foreign metal ions on the absorbance of 15 ppm V(V)-PHF complex 68 VI List of Figures Fig. No. Page Fig. 1. The basic structure of hydroxyxanthene dyes 5 Fig. 2. Nonaromatic derivatives of 2,3,7-trihydroxy-9-fluorone 6 Fig. 3. Aromatic derivatives of 2,3,7-trihydroxy-9-fluorone 7 Fig. 4. Heterocyclic derivatives of 2,3,7-trihydroxy-9-fluorone 8 Fig. 5. Some of bisfluorone structures 9 Fig. 6. Critical micelle concentration 18 Fig. 7. Schematic representation of aifinverse micelle 21 Fig. 8. (A):Schematic diagram of the simplest single-line FIA manifold (B):A typical recorder output as obtained with a spectrophoto- metric flow through cell 34 Fig. 9. Dispersion in the FIA system 37 Fig. 10. Limited, medium and large dispersion types 38 Fig. 11. (A): Atypical Rheodyne low pressure teflon rotary valve (B): Cross-section of a 4-way rotary valve interchange between two stream 42 Fig. 12. The synthesis of phenylfuorone 46 Fig. 13. Effect of n-hexadodecylpyridinum bromide on the absorbance of PHF 50 Fig. 14. Effect of sodium n-dodecylsulphate on the absorbance of PHF 51 Fig. 15. Effect of n-hexadodecylpyridinum bromide on the absorbance of Fe(III)-PHF complex 54 Fig. 16. Effect of n-hexadodecylpyridinum bromide as a earner on the absorbance of 25 ppm Fe(III)-PHF complex 56 Fig. 17. Effect of using sodium n-dodecylsulphate as a carrier on the Absorbance of 25 ppm Fe(III)-PHF complex 58 VII Fig. 18. Effect of H2O as a earner on the absorbance of 25 ppm Fe(TTT)-PHF complex and different concentrations of n-hexadodecylpyridinum bromide 60 Fig. 19. Effect of H2O as a earner on the absorbance of 25 ppm Fe(III)-PHF complex and different concentrations of sodium n-dodecylsulphate 61 Fig. 20. Effect of H2O as a earner on the absorbance of 25 ppm V(V)-PHF complex and different concentrations of sodium n-dodecylsulphate 62 Fig. 21. Calibration curve for Fe(III)-PHF using lxlO'6M PHF, lxlO'2 sodium n-dodecylsulphate and H2O as a carrier 64 Fig. 22. Calibration curve for V(V)-PHF using lxlO"6M PHF, lxl0'2 sodium n-dodecylsulphate and H2O as a carrier 66 Abstract Phenylfluorone was synthesized with the objective of developing a method for determining Fe(III) and V(V) in the presence of micelles using flow injection technique. Phenylfluorone showed a wavelength of the maximum absorption at 412 nm which was not affected by the presence of micelles i.e. n-hexadodecylpyridinum bromide and sodium n-dodecylsulphate, but they have different effects on the absorbance of PHF. The complexes of PHF-Fe(III) and PHF-V(V) showed the wavelength of the maximum absorption at 428 nm and 412 nm, respectively. Presence of micelles shifted the wavelength of the two complexes to a lower one. Generally the addition of micelles increased the absorbance of phenylfluorone metal ions complexes except for PIIF-V(V) with hexadodecylpyridinum bromide. With flow injection technique two approaches were practiced the use of micelle as a carrier or water as a carrier. Sodium n-dodecylsulphate increased the absorbance of the two complexes when it was used as a carrier or added to the metal ions using water as a carrier. On the other hand, the use of n-hexadodecylpyridinum bromide as a carrier increased the absorbance of the complexes but it decreased the absorbance when it was used in conjunction with metal ions and water as a carrier. After establishing the optimum FI conditions for PHF-Fe(III) and PHF-V(V) complexes, the calibration curves were constructed and produced semilinear response in the concentration range studied. Ti(I V) showed a negative interference with both complexes whereas V(V), Mo(VI) and Fe(IIt), Mo(VI) showed a positive interference in PHF-Fe(III) and PHF-V(V) complexes, respectively. IX CHAPTER ONE INTRODUCTION Introduction 1.1 Ilydroxyxanthene dyes Hydroxyxanthene dyes are the most frequently used reagents in spectrophotomefric determination of metal iotis in addition, the formation of coloured chelates of metal ions with some of them is often used in the visual indication of the equivalence point in the compleximetric titrations. The most common and longest-known of xanthene dyes are eosine, phenylflouorone, calcein, methylfluorone, fluorescein and pyrogallodl red groups(l). There was a great increase in the interest in these groups of dyes in 1950s and 1960s, where a number of substances with this structure were prepared and used in spectrophotometric studies(1). Further development associated with the use of surface-active substance in spectrophotometry occurred in the 1970s. At present, in addition to the solution of old problems and application of methods already developed to the analysis of practical sample, quaternary systems containing combination of various types of micelles and other complicated systems, permitting a considerable increase in sensitivity and other parameters of analytical method, are being studied (1).