AN ABSTRACT OF THE THESIS OF JOHN ARTHUR HAUSCHILD for the MASTER OF SCIENCE (Name) (Degree) in CHEMISTRY (ANALYTICAL) presented on (Major) Title: CHROMATOGRAPHIC SEPARATION OF ALKALINE EARTH METALS USING ALPHA-HYDROXYISOBUYRIC ACID Abstract approved: Redacted for Privacy Max B. Williams A systematic study of the elution of magnesium and calcium from Dowex 50 X 8 resin using a-hydroxyisobutyric acid (a-HIBA) at various pH values and concentrations, indicated that the difference in the equilibrium distribution coefficients of these two elements was large enough for a good separation.This fact was applied to develop a chromatographic procedure for the separationof milligram quantities of magnesium, calcium, strontium, and barium.After magnesium was eluted with 0. 22M a-HIBA at pH 4. 5, thethree remaining elements were eluted by varying the concentration and pH of a-HIBAduring the course of the elution (exponential gradient elution).After its respec- tive elution, each alkaline earth metal was directly determined by atomic absorption spectroscopy.Using this method, several success- ful analyses of synthetic samples (similar to the composition of sea water) were performed.Yield determinations of the alkaline earth metals from these analyses were consistently greater than 93%, with the overall average yield being 98%. Chromatographic Separation of Alkaline Earth Metals Using Alpha-Hydroxyisobutyric Acid by John Arthur Haus child A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science June 1971 APPROVED: Redacted for Privacy Professior of Chemistry in charge of major Redacted forPrivacy Chairman of Department of Chemistry Redacted for Privacy Dean of Graduate School Date thesis is presented )6,7)/q2) Typed by Mary Jo Stratton for John Arthur Hauschild ACKNOWLEDGEMENTS There are numerous people that have made it possible for my having the opportunity to pursue the program that has led up to this dissertation.It would be impossible to express my thanks to all of these individuals but there are a few that should be singled out for their help. I would like first to thank Dr. Max B. Williams, my major professor, for having the courage and patience to continue to support me throughout this entire program.Without his help and encourage- ment I would probably have never completed this program for the M. S. degree. Secondly,I would like to express my thanks to Captain Jack Terry, a fellow Air Force officer stationed at McClellan AFB, Sacramento, California.It was with his help that data for some of the experiments performed in this study were accumulated. Also I would like to thank Dr. Bert E. Christensen, former chairman of the chemistry department, and Dr. Stephen J. Hawkes for their assistance and guidance in my course work. Finally,I wish to express my sincere gratitude to the United States Air Force for making it possible for me to undertake this study at Oregon State University.The opinions expressed by me, however, are my own and do not reflect the policies or opinions of the United States Air Force or the Department of Defense. TABLE OF CONTENTS Page INTRODUCTION 1 Survey of Separational Methods 1 Purpose of This Study 11 PRINCIPLES OF ION EXCHANGE 14 Resins 14 Column Mechanics 16 Column Operation 17 Factors Affecting Separation 20 Column Parameters 23 Distribution Coefficient 23 Separation Factor 23 Volume Distribution Coefficient 24 SEPARATION FACTOR DETERMINATION 28 Objective 28 Apparatus 29 Preparation of Solutions 31 a- HIBA 31 Calcium and Magnesium Stock Solutions 31 Pretreatment of Cation Exchange Resin 32 Procedure for Peak Elution Volume Determination 32 Column Method 33 Concentration Determination 33 Results and Discussion 35 ANALYSIS OF SYNTHETIC SAMPLE 41 Preparation 41 Procedure 41 Results and Discussion 43 BIBLIOGRAPHY 56 LIST OF TABLES Table Page 1 Treatment Procedures for Cation Resin Columns. 32 2 Operating Conditions for Calcium and Magnesium. 34 3 Effect of Eluting Agent on Peak Elution Volumes. 38 4 Analysis of Synthetic Sample. 47 5 Operating Conditions of Perkin-Elmer Model 403 Atomic Absorption Spectro- photometer. 50 LIST OF FIGURES Figure Page 1 The separation of magnesium, calcium, strontium, barium, and radium with ammonium lactate eluent. 6 2 The separation of beryllium, magnesium, calcium, and strontium with 1. 5M hydro- chloric acid eluent. 7 3 The separation of magnesium, calcium, strontium, and barium with ammonium citrate eluent. 8 4 Separation of alkaline earths with zirconium molyb date. 10 5 System with constant-volume mixing chamber for gradient elution. 30 6 Influence of alpha-hydroxyisobutyric acid concentration and the effect of pH upon the elution of magnesium. 36 7 Influence of alpha-hydroxyisobutyric acid concentration and the effect of pH upon the elution of calcium. 37 8 Separation of alkaline earths and sodium with ammonium alpha-hydroxyisobutyrate eluent. 44 9 Calibration curve for magnesium, using the Perkin-Elmer 290B atomic absorption spectrophotometer. 48 10 Calibration curve for calcium, using the Perkin-Elmer 290B atomic absorption spectrophotometer. 49 11 Calibration curve for magnesium, using the Perkin-Elmer 403 atomic absorption spectrophotometer. 51 Figure Pa e 12 Calibration curve for calcium, using the Perkin-Elmer 433 atomic absorption spectrophotometer. 52 13 Calibration curve for strontium, using the Perkin-Elmer 403 atomic absorption spectrophotometer. 53 14 Calibration curve for barium, using the Perkin-Elmer 403 atomic absorption spectrophotometer. 54 CHROMATOGRAPHIC SEPARATION OF ALKALINE EARTH METALS USING ALPHA-HYDROXYISOBUTYRIC ACID I.INTRODUCTION While numerous methods for the separation of trace amountsof the alkaline earths are known, none of these methods aresimultane- ously practical and quantitatively successful in theseparation of Large amounts of these elements. A survey of the literatureshows that cation-exchange methods have been used almost exclusivelyin the few papers which have reported quantitativedata (7, 22, 25, 29), and this technique appears at the present time to be the mostpromising one for separating larger quantities of the alkaline earths. Survey of Separational Methods In recent years many investigators havereported separating the alkaline earths from each other and from severalother elements by methods other than precipitation procedures.One method where progress has been made in theseparation of the alkaline earth metals from each other is paper chromatography.Gordon and Hewel (11) reported quantitatively separating microgram amountsof several alkali and alkaline earth cations, and believed that acomplete separa- tion of alkaline earths and beryllium was possibleby their procedure. Another scheme, which describes the quantitativeanalysis of micro- gram amounts of alkaline earthmixtures, employs paper strips with 2 an eluting solvent consisting of methanol, isopropanol, formic acid, ammonium formate and water (35). Application of solvent extraction to the analysis of alkaline earths is not extensive.Few procedures are specific for these elements, and the applications have mainly been to the separation of these elements from one another.Morrison and Freiser (30) reviewed extraction procedures up to 1956.For the separation of calcium from strontium, resort must be made to the extraction of the anhydrous nitrates with such solvents as absolute alcohol and ether, acetone, nitric acid, or glacial acetic acid (3), which dissolves calcium nitrate and leaves most of the strontium and barium nitrate. This procedure has been applied particularly for the separation of a little strontium from much calcium. Extraction of calcium, barium, strontium and many other elements with organic solutions of 2-thenoyltrifluoroacetone (TTA) used in radiochemical separations has also been summarized (37). Stary and co-workers have made several systematic studies of many metals, alkaline earths included, by solvent extraction.In one study, the extraction of alkaline earths by 0. 500M oxine (8-hydroxyquinoline) in chloroform, in the absence of a complexing agent and in the presence of 0. 010M oxalic acid, was discussed (46).In another study, the extraction of alkaline earth metals by 0. 100M acetylacetone, benzoylacetone, and dibenzoylmethane solutions in benzene as a 3 function of pH was mentioned (47).These investigators were not able to extract the alkaline earths with chloroform in the presence of an excess of cupferron (0. 05M) throughout the pH region studiedin another investigation (48). The development of ion-exchange methods has been very rapid. At first ion exchangers were mostly used for water softening but they soon became widely employed in many other fields.These methods assumed great importance in chemical research, in analysis, in preparative work as well as in technology.The appearance of ion exchangers had a tremendous impact on analytical chemistry also. Their use gave analysts new methods which led to the solution of previously insoluble problems, such as separating the rare earth metals.The need for an accurate and fairly rapid procedure for the analysis of mixtures of alkaline earth metals also led to the applica- tion of ion-exchange chromatography to this problem. Trace amounts of alkaline earths have been separated from each other on anion exchange resin pretreated with 0. 05M ammonium citrate at pH 7.5, elution order being barium, strontium, and cal- cium (32).In another anion exchange study, Nelson, Day and Kraus (31) separated trace quantities of a number of elements