IHHHH ‘H l \H EXTRACTION OF LANTHANUM (Ill) BY MORlN-METHYL ISOBUTYL KETONE Thesis {or “no Dog”. 0‘ M. S. MICHIGAN STATE UNIVERSITY Yuk-Hang Cheuk 19 .61 3v ‘ ; ‘ MICHIGAN A STATE‘UNWERSITY EAST LANSINGIA‘ICHIGAN mcHrc-w STATE umvmsnv I_UERARY ABSTRACT EXTRACTION OF LANTHANUMHII) BY MORIN- * ‘METHYL ISOBUTYL KETONE by Yuk-Hang Cheuk Lanthanum(III) forms with morin a complex which can be extracted quantitatively from an aqueous perchloric acid solution at pH 6. 70-6.‘80 into hexone (methyl isobutyl ketone). Spectrophotometric and spectrofluoro- metric methods were employed for analyzing the organic phase. The various factors which affect the extraction of this complex in given system were investigated. The selected volume ratio of organic to aqueous phase was 2. to 1. At pH 6. 7-6. 8 lanthanum(III) forms a 1:2 complex with morin. It is assumed that the extracted species would be the ion-pair formed between lanthanum(III)-morin and an anion, such as hydroxide, perchlorate, or chloride ion. The lanthanum(III)-morin complex in hexone is excited by the 365 mu radiation, and the fluorescence radiation is emitted with peak intensity at 505-510 mu. Morin hexone solutions do not fluoresce appreciably under these conditions. The absorption band peak of the lanthanum(III)- morin complex and morin are at 410 and 356 mp. respectively. The absorbance and fluorescence intensities of the complex in hexone vary linearly when the concentration of lanthanum(III) in the aqueous phase is varied between 0-487 with 400'? of morin in hexone. Above 487 of lanthanum(III), the absorbance and fluorescence decrease. Yuk-Hang Cheuk When successive extractions were made from an aqueous sample solution, the major part of the lanthanum(III) in the aqueous phase was extracted with the first portion of morin reagent, and up to 287 of lanthanum(III) can be extracted by this single extraction. 6 The second portion of morin reagent was effective for‘ completing the extraction when the concentrationof lanthanum(III) was between 28 to 487 in the original aqueous sample solution. . The addition of samarium(III) to the original aqueous phase has a slight effect on the fluorescence intensity of the organic phase at very dilute aqueous lanthanum(III) levels. . Lanthanum(III) also can be extracted from aqueous dilute solutions of hydrochloric acid, nitric acid or sulfuric acid into hexone containing 400 7 of morin. EXTRACTION OF LANTHANUMUII) BY MORIN- METHYL ISOBUTYL KETONE BY Yuk-Hang Cheuk A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemistry 1961 ACKNOWLEDGMENTS The author wishes to express her sincere appreciation to Dr. A. Timnick for his guidance and encouragement throughout the course of the entire investigation and preparation of this thesis. ************** ii VITA Name: Yuk-Hang Cheuk Born: May 27, 1935. Hong Kong Academic Career: Chung Wha Middle School (1953) Bowling Green State University, Bowling Green, Ohio (1956-1959) Michigan State University, East Lansing, Michigan (1959—1961) Degree Held: B. S. Bowling Green State University (1959) iii TABLE OF CONTENTS Page INTRODUCTION ......................... l HISTORICAL ‘ ................... , ........ 3 THEORETICAL ......................... 7 EXPERIMENTAL ........................ 1 1 Instrumentation ...................... 1 1 Reagents .......................... l 1 Preparation of Reagent Solutions ............. 12 Experimental Procedures. . . . ............. 13 EXPERIMENTAL RESULTS AND DISCUSSION ......... 15 Solvents Tested . . . . . ................... 15 Effect of pH ..... . .................. 16 Effect of Lanthanum(III) Concentration .......... 19 Effect of Morin Concentration ............... . 22 Effect of Samarium(III) .................. 22 Effect of Acid ....................... 25 Completeness of Extraction ........... . . . . 25 ‘ Stability of the Complex in the Organic Phase . . . . . . 27 Nature of the Complex ............. . . . . . . 30 CONCLUSION ........................ .. .. 31 LITERATURE CITED ..................... . . 34 iv LIST OF TABLES TABLE Page 1. Extraction of Lanthanum(III) from "Different Media at pH 6.7-6.8 by Morin-hexone . . . . . ......... 26 2. Lanthanum(III) Recovery by a’ Single Extraction. with Morin-hexone from Aqueous Perchloric Acid Sample. Solutions at pH 6. 7-6. 8 ................. 29 FIGURE 10 LIST OF FIGURES Effect of pH in the aqueous phase on the fluorescence of hexone phase containing lanthanum(III)-morin complex or morin . . . . . . .. . . .. ......... . . Effect of pH in the aqueous phase on the absorbance of hexone phase containing lanthanum(III)-morin complex or morin ................... Absorption and fluorescence intensity curves for lanthanum(III)-morin complex and morin in hexone. . Relationship between lanthanum(III) concentration in the aqueous phase and absorbance or fluorescence intensity of hexone phase .............. Relationship between morin content in hexone (reagent) and absorbance or fluorescent intensity of hexone phase. . . .. ...... . . . ......... Effect of samarium(III) on absorbance and fluor- escence intensity of the hexone phase containing lanthanum(III)-morin complex . . . . . . .. ..... Effectiveness of each of three successive extractions performed on individual sample solutions ...... vi Page 17 18 20 21 23 24 28 INTRODUCTION Liquid - liquid solvent extraction has long been known as a method of separation in analytical procedures. The principles of the distribution (or extraction) method’were introduced by Nernst (1891) [22]. He estab- lished the constancy of the partition coefficient for species of the same molecular composition distributed between two immiscible solvents, and the possibility of using his distribution law to study the dissociation equilibria of a number of substances in aqueous solution. Shortly after- wards, Hendrixson [l 1] studied the distribution coefficient between organic and aqueous phases. In recent years, many investigators have shown interest to utilize the extraction technique for separating elements including individual rare earths from ores and sandsp A valuable appli- cation is in radiochemical separations. The phenomenon is based upon, the fact that if a substance {is dis- solved in a system of two immiscible or slightly. miscible liquids, the substance is distributed between the two layers in a definite manner. The classification of extraction system is based on the type of extract- able species formed. Two broad categories are chelate and ion association extraction systems. . Most extractable species whichinvolve chelation solely are coordination complexes [18]. The solubility of internal complexes and of a number of complexes of metals with inorganic ligands in organic solvents makes it possible to utilize the distribution method. Furthermore, many of the complexes have a distinct color, enabling them to be adapted to colorimetric or fluorometric analysis. Many- variables are involved to formulate quantitatively the relation between the partition coefficient for a metal in a given system [17], such as the concentrations of the metal ion itself, pH of the aqueous phase, concentration and type of reagent, temperature, and nature of the organic solvent. A few organo-lanthanide complexes can be excited in the near ultraviolet and visible region of the spectrum to emit intense fluor- escence [10, 14, 23, 35, 38], which is characteristic of the complex. Lanthanum(III), gadolinium(III), and lutetium(III) are the only tripositive lanthanide ions which contain sufficiently stable cation electronic configurations to yield an observable fluorescence. The work which follows was undertaken to study the distribution of microgram quantities of lanthanum(III) between an aqueous layer and various organic solvents containing the organic reagent morin (2', 4', 3, 5, 7-pentahydroxy flavone) . The interrelationship between absorbance or fluorescence intensity and concentration of lanthanum(III) was to be determined to establish whether or not, extraction followed by measurement of absorbance or fluorescence of the organic phase could form the basis for quantitative determination of small quantities of lanthanum(III) in an original aqueous s olution . HISTORICAL The book entitled Solvent Extraction in Analytical Chemistry by Morrison and Freiser [20] still represents the only comprehensive treatment of extraction as applied to inorganic analysis. .iIn this book, principles of solvent extraction, apparatus and general technique, extraction systems and separations are discussed thoroughly. 1 More recently, their chapter in Comprehensive Analytical Chemistry [21] has served to present the latest information in a rapidly developing area of analysis. The new edition of Sandell's book [32] Colorimetric Determination of Traces Metals also gives increasing emphasis to extraction methods. With regards to reviews, a series on extraction written by Craig [3-8] in Analytical Chemistry presents an excellent survey of the developments in the organic and biochemical fields, with emphasis on the technique of countercurrent distribution. . In two review articles by Morrison and Freiser [18, 19], approxi- mately 600 references are cited. . The technique as applied to the separation of inorganic and biochemical substances is emphasized. In a series of articles by Rydberg [25, 26, 27, 28] and other Scandinavian investigators the applicability of the distribution method for the quantitative study of complex formation in solution is demon- strated. To interpret data relating to the extraction of a metal complex by an organic solvent from an aqueous phase of low and constant ionic strength, they also examined the influences of temperature, the metal ion itself and anions in the solution. The possibility of separating metals by extracting some of them as acetylacetonates from aqueous sodium perchlorate solution into the organic solvents, chloroform, benzene or hexone is discus sed. Brown, Steinback and Wagner [1] have developed a method for lanthanides which can be selectively extracted from aqueous solution with acetylacetone at pH 4 to 6. Solubility and extractability of the acetylacetonates vary with the radius of the lanthanide ions. Extraction of the lanthanides with acetylacetone is enhanced by the decrease in basicity of the central metal ion. Templeton and Peterson [36] carried out batch extractions of aqueous solutions of lanthanum(III) and neodymium(III) nitrate mixtures with n-hexyl alcohol at room temperature. A spectrophotometric method was employed to determine neodymium, and the total oxides were determined by ignition. Dryssen and Dahlberg [9] have studied the extraction of lanthanum(III) Samarium(III), hafnium(IV), thorium(IV) and uranium(VI) with oxine and cupferron. Two organic solvents were used, chloroform and methyl isobutyl ketone. The distribution of the metals between the two phases were measured radiometrically. The ionic strength ‘in the aqueous phase was kept constant at 0. l M using perchloric acid, sodium perchlorate, and sodium hydroxide. The complex formation constants were calculated. They also point out that the total metal concentration always was low (<10'3 >10'8M). If higher metal concentration had been used, the metal oxinates and cupferrates would have precipited at certain pH values. . Separations by extraction of certainlanthanide ions as 5, 7-dichloro- 8-quinolinol chelates are described by Moeller and Jackson. [16]. . The extraction of corresponding 5, 7-dichloro-8-quinolinol chelates into chloroform was complete in controlled pH ranges. They also showed that it is favored by decreased basicity of the lanthanide ions. The quantities of material extracted were determined spectrophometrically. An extraction and flame spectrophotometric method for the determination of lanthanum(III) was investigated by Rains and Dean [24]. Microgram quantities of lanthanum(III) were selectively extracted by a 0. l M solution of 2-thenoy1trif1uoroacetone in hexone from a .l M acetate solution buffered at pH! 5. . Lanthanum(III) was determined by a flame photometer. Eighteen elements were tested for interferences. A . Numerous papers have described the extractionof metal ions through complex formation with one of the organic esters of orthophos- phoric acid or butyl derivatives. Warren and Suttle [37] have extensively studied the extraction of scandium(III),' yttrium(III), and lanthanum(III) into an amyl alcohol solution containing the mono(n-alkyl) orthophosphoric acid. from an aqueous nitric acid solution. The result was interpreted in terms of chelate formation of a four-membered ring. . Pollard, McOmie and Stevens [23] have reported a paper chromato- graphic method for the separation and detection of lanthanides. . Individual lanthanons and lanthanon groups located at various spots on the paper were distinguished by using different spray reagents upon spots of the nitrates. . Lanthanum(III) yielded a brightly green fluorescent spot when the dried strip was sprayed with morin in 50% alcohol, then exposed to ammonia and examined in ultraviolet light. . Lederer [12, 13], employing paper chromatography for the separa- tion of ions, demonstrated the separation of suchpairs of lanthanons as lanthanum-yttrium, lanthanum-dysprosium, and lanthanum-ytterbium using one solvent-~ethanol containing 30% of 1 N hydrochloric acid or 10% of 2 N hydrochloric acid. The chromatogram was air-dried and dipped into an ammoniacal alcohol solution of 8-quinolinol and viewed under ultra-violet light. . Lanthanum(III), and lutetium(III) yield yellow or green fluorescent spots while all others yield brown or black spots. Morin has been used as a sensitive reagent for the fluorometric analysis or fluorometric detection of a large number of metals [2, 33]. . Sandell [31,1 32] has stated that morin gave a yellow-green fluor- escence with beryllium(II) in a solution containing sodium hydroxide or potassium hydroxide. Sill and Willis [34] have reported a fluorometric method using morin as chelating reagent for submicrogram quantities of beryllium(II) which produced fluorescence in alkaline solution. Experimental condi- tions have varied considerably, particularly with respect to instru— mentation, quality and concentration of morin and alkalinity. Thorium(IV) reacts with morin to yield a yellow complex that fluoresces when irradiated with ultraviolet light. . This system has been investigated by Milkey and Fletcher [15]. The effect on the fluorescence by such variables as concentration of acid, alcohol, thorium, morin and complex, temperature and wavelength of exciting light are studied to determine experimental conditions yielding maximum fluorescence. The effects of zirconium(IV), aluminum(III), iron(III), calcium(II), and lanthanum(III) are discussed. THEORETICAL The possibility of using the distribution method to study complex compounds in solutions and the feasibility of separating substances by this method was demonstrated a long time ago. The general practical quantity in describing extraction or separation is the distribution ratio, D, a stoichiometric ratio including all species of the same component in respective phases, is defined as follows, _Total concentration in organic phase Total concentration in aqueous phase Another quantity which indicates the degree of separation obtain- able and which is related to D, is the percent extraction E. . It is defined as follows , E _ 100[A]o V0 __ 100D [A]0Vo + [A]WVW D + VW7V0 where A = concentration of a substance and o and w refer to the two solvents V = solvent volume In inorganic extraction systems, complexing of metal ions by organic complexing agents leads to the formation of uncharged species which fall into. two main categories, chelates and ion as soc‘iation systems. Chelate extraction systems include only those involving neutral chelates. The case may be described by Mn+ + nR' ———> MR where Mn+ = n-valent metal ion R" an anion of a suitable chelating agent In association extraction, the metal ion combines with a molecule or ion to form a positively or negatively charged ion. 4 This charged species then forms an effective neutral ion pair with. other ions. These possible interactions are shown by the following equations, n+ n+ .M +bB———9 MBb n+ _ n+ _ MBb +nX —>(MB ,nX) OI' n+ " a M +(n+a)X —-> MXn+a an + aY+ ———> (aY n+a <-—- + a“ ’ MXn+ a) where U1 ll neutral ligand X" = an anion appropriate for pairing with the cation *4 II a suitable cation required to form the ion-pair From a quantitative standpoint, consideration of equilibria existing in the extraCtion system is helpful in pointing out "whichexperimental parameters play an important role in the completeness as well as the selectivity of the extraction. Although a chelate extraction was chosen to represent the inorganic type, the same general approach may be used for ion association extraction [20]. . The ionization and complexation reactions, and the distribution of various species and the pertinent respective equilibrium constants can be represented by the following condensed expressions (HR. will serve as a general formula for the reagent), + _ . H - + R —_—>i’ HR —-—'>' HR n+ " : M + nR -——> MRn -——-> MRn water 2 organic solvent I The chelating reagent distributes between the two phases a _ [HR HR aq +_ HRorg Km- [HRIW the reagent dissociates in the aqueous phase + .. HR ——>4_ H+ + R' Ka= [liHleR 1 to give a chelating anion R- which reacts with the metal ion and forms the extractable chelate n+ ‘ _ [MR M + nR ———> MRn K'f—[Mn ][R" which in turn, distributes between the phases > _ [MRnlo' MRn .4.— MRn(0rg) KDx - [MRn] w Therefore, the distribution ratio D, can be evaluated from these equilibrium expr es sions . Thu 5 , _ - (M). _ [MR 10 _ Kf K n KD HRo n D— —— — ——-—£—- - a . (M)W [Mn 1w KD I x [H ‘W r It may be noted from [the equation above that the extractability of a metal ion with given reagent and organic solvent depends greatly upon the organic phase concentration of the reagent and the hydrogenrion concentration in the aqueous phase. An increase in the reagent concen- tration in the organic phase or a decrease in the hydrogen ion. concen- tration in the aqueous phase will increase the distribution ratio D. 10 Also,the equation indicates that D is dependent directly on the chelate stability (Ki), the relative solubility of the chelate in the organic phase (KDx)’ the reagent dissociation in the aqueous phase (Ka) and. inversely on the extent of extraction of the undissociated organic reagent into the organic phase (KDr). If several species can be formed between ion and a. complexing agent and several species are extracted into the organic phase, an extremely complex relationship among the extraction parameters exists. The general pattern for ion association extraction is not suitable for de 3 c ribing thi s extraction . EXPERIMENTAL Instrumentation Extraction separatory funnels with "Teflon" stop-cocks were used for the entire extraction procedures. The spectrofluorometer employed in this study was the same one used by Fleck [10] in this laboratory, also the same procedure employed in obtaining fluorescence intensity measurements. . The only change was that the entrance slit of the Bausch and Lomb monochromator, and the exit slit of the Beckman D.U. were set to 1.0 mm. The Bausch and > Lomb monochromator was set at 365 mu for all measurements. The instrument was calibrated with 0. 47 per ml.’ dichlorofluorescein standard solution. Beckman D.U. sensitivity was adjusted when this solution was excited in the le20x50 mm. silica cell so that a fluorescence intensity of 50 was attained. A Beckman DK-Z spectrophotometer was used for all absorption measurements. Matched one cm silica cells were employed in all these measurements. . A Beckrnan model G pH meter with a glass-saturated calomel electrode pair was used to measure pH of the aqueous phase. The meter was standardized at pH 4 with, Beckman standard buffer solution. Reagents Lanthanum sesquioxide -- Optical grade, Heavy Mineral Co. , . Chattanooga, Tennessee Samarium sesqut; oxide -- Labeled purity 99. 9 per cent, Michigan Chemical Corporation, St. Louis, Michigan Dichlorofluorescein -- Eastman Kodak, white label. 11 12 Morin --- Reagent grade. Lot 8861,. K 81 K' Laboratories, Inc. Methyl isobutyl ketone -- Eastman Kodak, C.. P. Perchloric acid -- 70-72 per cent Bakers Analyzed Reagent. Hydrochloric acid -- A. C.S. Baker Analyzed Reagent. Sulfuric acid -- A. C.S. DuPont Analyzed Reagent. Nitric acid -- A.C.S. DuPont Analyzed Reagent. Sodium bicarbonate -- A. C.S. Fisher Certified Reagent. . Ammonium hydroxide -- A. C. S. Baker Analyzed Reagent Hexone (methyl isobutyl ketone or 4-methyl 2-pentanone) of technical quality was purified by the procedure of Rydberg and Brita Bernstron [30]. The solution was filtered and was washed withsodium bicarbonate and water to remove acid and water soluble impurities. Then the solution was saturated with water overnight, and distilled. . A 1030 to 1040 C fraction was collected and the purified hexone was stored in an amber colored screw capped bottle. The distilled water used throughout this investigation was passed through a "crystalab Deeminizer" ion exchange column in order to remove possible metal ion impurities contained in the water. Preparation of Reagent Solutions All stock solutions of lanthanum(III) perchlorate, sulfate, nitrate and chloride or samarium(III) perchlorate were prepared by dissolving the required amounts of freshly ignited oxides in 1- M perchloric acid, sulfuric acid, nitric acid or hydrochloric acid. The concentrations were as follows: La(III) in perchloric acid ....... 0. 326 mg per ml La(III) in sulfuric acid ......... l3. 2 mg per ml La(III) in nitric acid .......... l4. 3 mg per ml La(III) in hydrochloric acid ...... 13. 2 mg per ml Sm(III) in perchloric acid . ...... 3. 5 mg per ml 13 Working solutions were prepared from the stock solution by dilution with "deemi’nized" water. Solution of morin of the desired» concentrations were prepared by dissolving a weighed quantity of the solid mate rial in purifiedhexone. Fresh reagent solution was prepared for every trial. Fluorometric procedures were standardized with 0.47 per ml. solution of dichlorofluorescein in four percent ethanol. . The standard solution was prepared by dissolving a 4 mg. quantity of reagent in l: l... 95 percent ethanol. . A 10 m1. aliquot of this stoCk solution was diluted to 100 ml. for the working solution. Expe rim ental Pr oc edures All experimental work in this investigation was carried out at room temperature, 26 i l0 C. .A variety of solvents under various experimental conditions was examined for the purpose of finding a method for quickly and efficiently extracting lanthanum(III) from aqueous solution. ~ Organic solvents tested were chloroform, cyclohexanol or hexone. But of these only hexone' showed any promise, and therefore the procedures which follow, pertain .to this solvent. . The remaining solvents were tested by similar procedures and reasons for rejecting these are given in the discussion section. All standard metal ion solutions were prepared by dilution. . The concentrations are expressed in units of micrograms, 7,, per 10 m1. of solution. A 10 ml. aqueous sample solution containing a fixed amount (4 - 647) of lanthanum(III) was transferredwith. a volumetric pipet to a separatory funnel, 20 ml. (containing 100 - 8007 morin) of the organic reagent morin in hexone was added. The solution was mixed thoroughly. Finally the pH of the aqueous phase was adjusted to the desired level 14 with dilute ammonia or dilute perchloric acid. The funnel was shaken for three minutes. The phases were allowed to separate. Within a 30 minutes period, two clear layers were formed. The organic layer was yellow in color and water layer colorless. The respective layers were transferred to individual glass stoppered 25 ml. flasks. The pH of the aqueous phase was measured. . Aliquots of the organic phase were taken out for spectrophotometric and spectrofluorometric measurements. , Absorption spectra of the lanthanum(III)-morin complex in hexone were measured over the range from 270 mp to 700 mp. The entire spectrum was run against hexone as a comparison liquid. For fluorescence intensity measurements, a portion of the organic phase was excited with 365 mp. radiation, and the intensity of the fluor- escence emitted at 505-510 mp. was measured. With each set of extrac- tions, a blank was carried through a similar procedure. The blank was merely very dilute perchloric acid. Its pH was that of the aqueous sample solution. . To test for completeness of extraction, three successive extractions of individual aqueous aliquots were performed. For the first extraction 20 ml. of morin reagent solution was used, for the second 15 m1. of morin reagent and 5 ml. of hexone and for the third 10 ml. of morin reagent and 10 m1. of hexone. In all extractions, a total of 20 ml. of hexone was pres ent. EXPERIMENTAL RESULTS AND DISCUSSION Solvents Tested In preliminary investigation, a variety of organic solvents such as chloroform, cyclohexanol and hexone were tested in search for an effective solvent for the extraction of lanthanons from aqueous solutions. Chloroform was not suitable because of the low solubility of morin in this solvent. When morin dissolved in purified cyclohexanol was added to dilute perchloric acid solutions containing lanthanum(III) and the pH adjusted for optimum complexation reaction with dilute ammonia, stable emulsions in both phases were formed.. In some trials, the emulsion was stable for twenty-four hours. Better separation of the phases was attained when dimethylformamide)dioxane or acetone was added. But when these mixed solvents were employed, the fluorescence intensities for the organic phase of the blank solutions were almost as high as those obtained with the organic phases separated from solution containing the reagent and lanthanum(III). Only small wavelength separations between the absorption peaks recorded with the organic phases from the blank and sample solutions were noted at all pH levels tested. Such information would lead to the conclusion that complexation of lanthanum(III) by morin does not occur to any great extent in the above media. . Investigations employing cyclohexanol as the extracting solvent were discontinued. . Hexone was the most satisfactory solvent for the desired extraction. With hexone a low and reproducible fluorescence intensity for the blank solution was obtained, and only a thirty-minute period was required for the separation of the aqueous and organic phases. 15 16 Since the distribution. ratio in a liquid-liquid extractionis a concentration ratio, the actual fraction of the total solute extracted »will vary with the ratio solv’ent volumes [2‘1]. . The selected volume ratio of organic to aqueous phase was 2 to 1 throughout this entire investigation. Volume ratios of 1:2, 1:1 and 3:1 were also tested... Six hours after shaking, an emulsion still persisted in the 1:2 system and the organic phase yielded an uncertain fluorescence intensity reading of 36.5. Good separation was attained in the 1:1 and 3:1 systems. Fluorescence intensity readings for the organic phases were 56. 5-61. 2 and 32. 5-34. 0 respectively, in duplicate trials. . Even though higher fluorescence intensity readings were obtained with the organic phase from the' 1:1 systems, more reproducible intensity readings were obtained with the organic phase from the 2:1 volume ratio system and was therefore used throughout this investigation. Effect of pH The extractability of metal complex is greatly influenced by the pH of the aqueous phase. . Extraction as a function of pH was studied. The organic phase was analyzed after extraction by spectrophotometric and fluorometric measurements. To investigate this effect, a series of solutions containing 327 of lanthanum(III) with pH ranging from 2 to 10 was prepared. To each. of these 4007 of morinin 20 m1. of hexone had been added and the extraction performed. . In. Figure 1, curveA shows that maximum fluorescence intensity 132: from the complex. in the organic phase is attained when the pH is 6. 7-6.8. Curve B shows that morin in the organic phase obtained from the extraction of the blank does not fluoresce appreciably until a pH of 8-9 in the blank is reached. In Figure 2, curve A shows the effect of pH on the absorbance of the organic phase containing the lanthanum(III)-morin solution at 410 mp. 17 £5.88— Ho xvamaoo .nmuofi A3584 .mqfifiwusoo owns? 28on mo oocoomouosd so 0923 msoodwm 05 5 EA mo “03mm - .a «:5th mm a . a .m LN p n _ a 4 a n I4 ‘11)“ 0 . n ' ‘ . - O Q m .. 0 9 £ r‘ 4 o Canoe room u m £85 53 + :83 Sm ... .4. 3 ON om ow om oo 33%} Aitsuaiul sons 3 99.101113 ’V‘ 18 .awuofi no 633500 canoe: #:de mswfimusoo @923 0:98: mo mocdnpomfim 9.3 so 0923 mfiooacm 6:“ GM .39 mo 33mm .N madmwh 0H <. canoe .Poov £38. roov + 55.3 (run u u 4:111 w 4 — [To l N o Lmd Ilmoo flux 0117 re soueqaosqv 19 The abs orbance of the lanthanum(III)-morin solutions 'reaCh amaximum at pH 6. 7-6. 8 and then decrease. . Above pH 8, the absorption peaks shift to a longer wavelength. It is suggested that another non-fluorescent species is being formed. Curve B shows that morin in the organic phase obtained from the extraction of the blank of pH 2 to 10 does not absorb appreciably at 410 mp. In subsequent studies the pH of the aqueous sample solutions was adjusted to pH 6. 7 to 6. 8 before the extraction. . . In Figure 3, curves A and B show the absorption spectra for solu- tions of pure morin and the lanthanum(III)-morin complex in the organic phase obtained from the extraction at pH 6. 7 to 6. 8, while curves C and D show the fluorescence spectra for pure morin and lanthanum(III) + morin complex solutions . Effect of Lanthanum(III) Concentration The effect of increasing lanthanum(III) concentration in the aqueous phase at pH 6. 7-6. 8 on the fluorescence and absorbance of the organic phase, when the original morin content in the hexone was kept at 4007, is shown in Figure 4. Curves A and B indicate that a nearly linear increase in the fluorescence and absorbance for the lanthanum(III)- morin hexone solutions is attained for the concentration range of 0 to 487 of lanthanum(III) in the original sample solution. The slopes of both curves decrease sharply at a lanthanum(III) concentration of above 487. This behavior suggests that the complex is relatively weak and/or that the limit of extractability was reached. This study indicated that 327 of lanthanum(III) would be used in the preparation of solutions to study various effects on extractability and fluorescence to ensure that the maximum amount of lanthanum(III) would be converted to the complex form which would be extracted. o . ed on on 20 ow om Op Fluorescence Intensity 1323 (curves C and D) or . vacuums dm _ Gian—H- pad . 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(g pue V ssnxnzr) aoueqzosqv .ommAm oaoxoa «0 33555.” oosmomouosm no ooddQHOmnm pad @923 mdoodvm ofi aficoflmuuaooaou AHHCSBSAHGS dookfioo. mwamfiofldfiom 3v madman AHfivEDsdaacmH many won 03%. 21 Absorbance at 410 mp. - Curve B ova on: 0mg Cal 9: ONH c: on: em cm on op om 0* on om OH o _ _ . _ . _ _ _ _ _ _ n .r a n . o 0" 2.91 ~61 .\ «to: e on mp... >6 mm «to r 5.86 $2. m6! om ed! 1 o o m >61 ow m.oT s 4 o; l - op V anxng 233 Aitsuaiul auaosaxontg 22 Effect of Morin‘ Concentration Figure 5, curve A shows the effect of the change of morin concen- tration in the hexone reagent solution on the fluorescence of the organic phase when the original aqueous phase contains 327 of'lanthanurn'uII) at pH 6. 7 to 6.8, while curve B shows the same effect on the absorbance. Maximum fluorescence is obtained from the organic phase containing 3007 to 4007 of morin reagent per 20 m1. of hexone. . On further increase of morin concentration the fluorescence intensity decreases. This effect may be due to the absorption of the exciting light by the non-fluorescent uncombined morin in solution. Curve B shows that there is a nearly linear increase in absorbance with increasing morin concentration up to 4007 morin per 20 ml. of hexone and on further increase in morin concentration the absorbance still increases but at a lower rate. . This is due to the absorption by the morin which absorbs 410 mp radiation but with lower absorptivity than that of the complex. Effect of Samarium(III) Figure 6 shows the effect of the addition of samarium(III) to the aqueous phase containing 327 lanthanum(III) when the pH is 6. 7-6. 8 on the fluorescence of the organic phase which originally contained 4007 of morin. Curve A shows that the fluorescence intensity increases slightly when samarium(III) content in the aqueous sample solution is varied from 0 to 207. It is suggested that a small amount of fluorescent species is being formed. When an extraction was carried out on an aqueous sample containing only 207 of samarium(III), a fluorescence intensity from the organic phase of approximately twounits was observed. . Above 207 of samarium(III), the fluorescence, intensity decreases slightly and this is probably due to the competition between 23 O Na m m. rvo- u [m . u. m was 4. t a e C n a .m. omo S b A .0993 0:38: mo anfimsouzw vasomonosfl .Ho mondQHOmorm pad Ausowmonv osoxoa GM 30200 GEOE £063.59. QEwnoflmHom .m shaman CECE .mgdumonowz oow oow 000 com 00¢ com com 02 _ u _ I. _ .1 o l J o; m .oé .8 mm 3:832”.qu Sm .. 4 - X .N 4 c o a o l v 0 J o.m C 0 4 0 .u. . I I or. r. 1 Com (V anno) - 3351 Airsusiul sousosszonl‘g 24 Absorbance at 410 mp - Curve B .xoasoo cwuoauAHHCEscmfisg mswaflmusoo 0923 23on may mo 133283“ mocoomonosfl pom ooGd£HOmnd Go AHHCESENEdm mo poommm .o oufimfih SHCESENENm mfidumouofiz on op om ow om om on o n q _ _ n q l l m 8;. .0 ma 1 5.88 33. + 5382222 Sm OH om om (V ammo) - 23:1 Airsusiul aousosaxomg 25 samarium(III) and lanthanum(III) for morin. Curve B indicates that the absorbance'increases with increasing concentration of samarium(III) from 01:0 207, then remains essentially constant above 207 of samarium(III). This study shows that samarium(III) has more effect on fluorescence at extremely dilute aqueous lanthanum(III) levels and high organic reagent concentrations. Effect of Acid Table 1 demonstrates the possibility of extraction of lanthanum(III) from a dilute hydrochloric, nitric acid or sulfuric acid solution at pH 6. 7-6. 8 into hexone by employing 4007 of morin in hexone. The general shape of the absorption and fluorescence curves for the organic phases is the same as that obtained from perchloric acid sample solutions in all cases. This study indicates that similar com- plexes are extracted into the organic phase. Nitrate, chloride, sulfate or perchlorate ions do not compete strongly with morin for lanthanum(III) and in their presence extractable ion-pairs with lanthanum(III)- morin and some anion are still formed. No significant difference in extractability of lanthanum(III) is attained from any one of these dilute acid solutions . Completenes s of Extraction Figure 7, curve A, B and C show the completeness of extraction on the fluorescence of the organic phase when aqueous solutions contain- ing various amounts of lanthanum(III) at pH 6. 7-6. 8 are extracted with successive portions of morin reagent (4007, 3007 or 2007 in 20 ml. of hexone). The results indicate that the major part of the lanthanum(III) in the aqueous solution is extracted with the first portion of morin 26 Table l. Extraction of Lanthanum(III) from Different Media at pH 6. 7-6. 8 by Morin-hexone Dil- Acid La(III). 7 Abs. , 410'mp. Fluor., 132; HCl 13.2 0.290 14.5 HCl 26.2 0.515 32.5 HNO3 14.3 0.225 11.1 HNo3 28.6 0.530 31.5 sto, 13.2 0.260 12.0 H2804 26.6 0.530 27.0 27 reagent (400'7 morin) and also that up to 287 of lanthanum(III) are extracted completely by this single extraction. The second portion of , the morin reagent (3007 morin) is effective for completing the extraction when the concentration of lanthanum(III), is between 28 and 487 in the sample solution. . A third portion of morin reagent (2007 -morin) was used. No significant extraction was accomplished by this step. Results from these experiments were also used to test the reproducibility in extraction. . Curve A of Figure 7 is essentially a calibration curve for lanthanum(III) determination by a single extraction. It is the best curve obtained when the respective fluorescence intensi- ties for the organic phase from the sample solutions were plotted against the concentrations of lanthanum(III) in the sample solutions. The difference between the lanthanum(III) concentration present in each of the sample solutions and that found by using curve A, to read off the concentration corresponding to the fluorescence intensity measured for each of the samples, is listed in Table 2 for the 24 solutions'tested. . Only three attempts yielded absolute deviations greater than 27. With better temperature control and standardization in experimental procedure, the deviations could undoubtedly be minimized. Stability of the Complex in the Organic Phase The color of the organic phase was fairly stable. When the hexone extract containing the lanthanum(III)-morin complex was stored in a dark place for a! period of twenty-four hours, no appreciable change in its absorption or fluorescence was produced. .msoEdHOm 03500 35336:“ no p08p0mn0m 3.5300303 0>Mmm00050 00.23 mo #000 m0 mm0n0>flo0mmm .N. 0ndmwh SHCEssmfiadd m 8.0." mo a 03% 28 on op om ow ’ om ON OH d soflomnfis ppm “8300.303 cam sofiuodupx0 um: [I] a OO _ _ .oH ON om ow cm 7.17 .33 23:1 "Airsusiul soueosaxonIJ 29 Table 2. Lanthanum(III) Recovery by a Single Extraction with Morin- Hexone from Aqueous Perchloric Acid Sample Solutions at pH 6.7-6.8 IL . Absolute Relative -Lanthanum(III), 7 Diff. , Deviation Sample Taken Found 7 p. p. h. 1 0 0 0 0 13 0 0 0 0 2 4.0 4.0 0 0 14 4.0 3.0 -1.0 25 3 8.0 6.5 -1.5 23 15 8.0 9.0 +1.0 12 4 16.0 14.5 -1.5 19 16 16.0 15.0 -1.0 6 5 22.0 20.0 -2.0 9 17 22.0 22.0 0 0 6 25.5 22.5 -3.0 12 18 25.5 27.0 +1.5 6 7 29.0 29.0 0 O 19 29.0 29.0 0 0 8 32.0 32.5 +0.5 2 20 32.0 34.0 +2.0 6 9 36.0 35.5 -0,5_ 1 21 36.0 40.0 +4.0 10 10 39.0 38.5 -0.5 1 22 39.0 39.0 0 0 11 42.5 43.5 +1.0 2 23 42.5 44.0 +1.5 3 12 48.0 45.5 -2.5 ‘5 24 48.0 48.5 +0.5 1 30 Nature of the Complex No attempt was made to obtain information onthe nature of the complex. The absorption curve and the fluorescence spectrum curve for the lanthanum(III) species extracted into hexone are identical with those obtained by Fleck [10] with the lanthanum(III)-morin complex in a 50-50 dioxane-water solution. By a continuous variationimethod and a slope ratio method he establishedthat the species was a 1:2 complex, lanthanum(III) to morin, and that a probable structure could be 1— ‘T + Such a charged species could only be extracted-into an organic solvent as an ion-pair. Since lanthanum(III) combines readily-with hydroxide ion, it is not unreasonable to assume that the extracted species would be the ion-pair formed betweenthe complex. and a hydroxide ion. It is also possible that the ion‘pair could consist of the lanthanum(III)-morin complex and the anion, such as perchlorate or chloride, which is present in the aqueous phase. . No experimental evidence was obtained in this study to establish the nature of the extracted species. CONCLUSION Lanthanum(III) forms with morin a complexwhich can be extracted quantitatively into hexone by a single extraction when the pH in the aqueous phase is adjusted to 6. '7 to 6. 8.. The selected volume ratio of organic to aqueous phase was 2 to l (20 m1. of hexone contain- ing 4007 of morin to 10 ml. of lanthanum(III) in dilute perchloric acid solution). In the absorption spectrum for the solution of lanthanum(III)- morin complex in hexone, the maximum absorption peak is at 410 mp, while for pure morin hexone solution, the peak falls at 356 mp, but it also absorbs to a small extent at 410 mp. ~ Pure morin hexone solution does not absorb beyond 450 mp, therefore the complex content in hexone could be determined at 450 mp. The lanthanum(III)-morin complex in hexone fluoresces when it is excited with 365 mp radiation, and the fluorescence radiation is emitted at 505-510 mp. Pure morin hexone solution obtained from the extraction of blank does not fluoresce when the pHof the aqueous blank. is 8. When aqueous solutions containing various amounts of lanthanum(III) at pH 6. 7 to 6. 8 were extracted with successive portions of morin reagent (4007, 3007 or 2007 in 20 ml. of hexone), the fluorescence intensity of the organic phase showed that the major part of the lanthanum(III) in the aqueous solution was extracted with the first portion of morin reagent (4007 morin) and also that up to 287 of lanthanum(III) can be extracted completely by this single extraction. The second portion of morin reagent (3007 morin) is effective for completing the extraction up to the concentration between 28 to 487 of lanthanum(III) in the aqueous solution. 31 32 The possibility of extracting lanthanum(III) from an aqueous dilute hydrochloric acid, nitric acid or sulfuric acid solution of pH 6. 7 to 6. 8 into hexone containing 4007 morin was studied. The absorption and fluorescence curves for the organic phase show that complexes identical to the one extracted from the perchloric acid solution, are extracted into the organic phase. A linear relationship was obtained between the absorbance or fluorescence intensity of the lanthanum(III)-morin hexone solutions and lanthanum(III) concentration when the concentration of lanthanum(III) in the aqueous layer was varied from 0 to 487. The slopes of bothcurves decrease sharply above the concentration of 487 of lanthanum(III). . This behavior suggests that the complex is relatively weak and /orthat the limit of extractability is reached. The effect of samarium(III) in the original aqueous phase contain- ing 327 of lanthanum(III) shows that samarium(III) has a- slight effect on the fluorescence intensity of the organic phase at very dilute aqueous lanthanum(III) levels from 0 to 207. Above 207, the fluorescence intensity decreases slightly probably due to the competition between samarium(III) and lanthanum(III) for morin. . Absorbance increases with increasing concentration of samarium(III) up to 207, then remains essentially constant above 207 of samarium(III). No attempts were made to obtaininformation of the nature of the complexin the organic phase. . It is assumed that the extracted species would be the ion-pair formed between the lanthanum(III)-morin and a hydroxide ion or perchlorate ion. This study was a preliminary investigation of the extraction of lanthanum(III) with morin into hexone. Since this study. was carried out with solutions of very low ionic strength, it would be interesting to test how the system would behave at high ionic strength. . It would also be interesting to determine the nature of extracted species by evaporating 33 the solvent and identifying the crystals obtained. . In further studies, - the extractability of all available lanthanide ions by morin in hexone could be tested. 10. 11 12. 13. 14. 15. 16. 17. 18. 19. LIT ERATU RE CIT ED . Brown, W. C., Steinback, J..F., Wagner, W. F., J. Inorg. 81 Nuclear Chem. _1_3_, 119 (1960). . Charlot, (3., Anal. Chim. Acta, 1, 218 (1947). . Craig, L. C., Anal. Chem. _2_1_, 85 (1949). .. Ibid., 22, 61 (1950). .. Ibid., 23,41 (1951). . Ibid., 241,766 (1952). .Ibid., 26, 110 (1954). — I.bid., 28, 723 (1959). Dyrssen, D. , Dahlberg, V. , Acta Chem. .Scand. , _7_, 1186 (1953). Fleck, L. ‘L., Ph. D. Thesis, Michigan State University, (1961). .. Hendrixson, W. 5., Z. Anorg. Chem., _13, 73 (1897). Lederer, M.,. Anal. Chim. Acta, _l_5, 46 (1956). Lederer, M., Nature, 176,. 462 (1955). Livingston, R. S., J. Phys..Chem.,_6_1_,. 860 (1957). Milkey, R. C., Fletcher, M. H., J. Am. Chem..Soc., 22, 5425 (1957). ‘ Moeller, T., Jackson, D. E., Anal. Chem., 22, 1393 (1950). Morrison, G. H.,.Anal. Chem. _2_2_, 1388.;(1950). Morrison, G. H.,. Freiser, H., Anal. Chem. _3_2, 632 (1958). Ibid., _3_2_, 3.713 (1960). 34 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 35 Morrison, G. H. , Freiser, H. , "Solvent Extraction in Analytical Chemistry, " John Wiley 81 Sons, New York, 1957. Morrison, G. H., Freiser, H., "Comprehensive Analytical Chemistry," C... L. Wilson and D.‘ W. Wilson, eds. , Vol. 1A, Elsevier, Amsterdam, 1959. Nernst, W., Z. Phys. Chem., 8, 110 (1891). Pollard,.F. H., McOmie, J. F. W., Stevens, H. M., J. Chem. Soc., 3435 (1954). ' " Rains, T. C., Dean, J. A., Anal. Chem. _3_1_, 187 (1959). Rydberg, J., Arkiv. Kemi, _5_, 413 (1953). 151a, g, 101 (1955). Ibid., _g, 113 (1955). Ibid., 9, 95 (1955). Rydberg, J., Acta Chem. Scand., 4, 1503 (1950). Rydberg, J., Bernstern, B., Acta Chem. Scand., _1_1_, 87 (1957). Sandell, E. B. , "Colorimetric Determination of Traces of Metals, " 3rd ed. , Interscience, New York, 1959. Sandell, E. E., Ind. Eng. Chem. Anal. 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