The application of 1-(4-tolyl)-2-methyl-3-hydroxy-4-pyridone
(HY) to the extraction and spectrophotometric determination of
iron (III) are described.
In the aqueous phase iron (III) and HY form two different
complexes; FeY2+ and FeY2+, depending on the iron-HY concentration
ratio and the pH of the solution. It was found that only
the FeY2+ complex is extracted into chloroform

B. Tamhina

M . J. Herak

English

HRČAK - Portal of Croatian Scientific and Professional Journals

CROATICA CREMICA ACTA CCACAA 46 (3) 237-241 (1974) CCA-840 YU ISSN 0011-1643 543. 7 ;545,82 Origina.l Scientific Paper Application of 1-(4-Tolyl)-2-methyl-3-hydroxy-4-pyridone for the Extraction and Spectrophotometric Determination of Iron(III) M . J. Hemk and B. Tamhina Laboratory of Analytical Chemistry, Faculty of Science and Institute of Inorganic and Analytical Chemistry, University of Zagreb, 41000 Zagreb, Croatia, Yugoslavi a Received May 13, 1974 The application of 1-(4-tolyl)-2-methyl-3-hydroxy-4-pyridone (HY) to the extraction and spectrophotometric determination of iron (III) are described. In the aqueous phase iron (III) and HY form two different complexes; FeY2+ and FeY2+, depending on the iron-HY concen-tration ratio and the pH of the solution. It was found that only the FeY2+ complex is extracted into chloroform. INTRODUCTION In our previous publications1- 1 , the application of 2-carbethoxy-5-hydroxy--1-(4-tolyl)-4-pyridone and 1-phenyl-2-methyl-3-hydroxy-4-pyridone to the extraction and spectrophotometric determination of niobium(V), tantalum(V), zirconium(IV), thorium(IV), protactinium(V), gallium(III), vanadium(V) and iron(III) were described. While the above-cited reagents form three different complexes with iron(III) ~n the aqueous phase, the new reagent, 1-(4-tolyl)-2-methyl-3-hydroxy--4-pyridone (HY), forms only two complexes. The formation and properties of theE:e complexes and the application of this new reagent for the extraction and spectrophotometric determination of iron(III) are described in this paper. Th is reagent is very selective for the extraction and ,spectrophotometric determ 'nation of certain metals8 and its synthesis is very simple. 1-(4-Tolyl)-2-methyl-3-hydroxy-4-pyridone EXPERIMENTAL Reagents The synthesis and physical properties of 1-(4-tolyl)-2-methyl-3-hydroxy-4--pyridone were described previously9• Radionuclides s5.s9Fe (Institute »Boris Kidric«, 238 M . J . HERAK AND B . TAMHINA Vinca, Yugoslavia) in chloride form were used to study the extraction. The inactive iron (III) solution was standardized gravimetrically. All of the reagents were of analytical purity. Apparatus Absorbance measurements were made on a Beckman Spectrophotometer, model DU-2. A pH-meter, Radiometer, model TTT 1 was used for pH measurements Isolation of iron(III) extracted species The iron (III) extracted species was obtained by shak~ng a chloroform solution of the reagent (0.05 M) with an equal volume of the iron (III) solution at pH about 2.2. Iron was in excess of the reagent. The organic phase was separated and the solvent evaporated i n vacuo. The solid product was recrystallized from chloro-form-ligroin mixture (1 : 2) and analyzed. AnaL C26H240 4N2C1Fe (519.78) calc'd : C 60.07 ; H 4.66 ; N 5.39; Cl 6.82 ; Fe 10.75%. found : C 60.58; H 4.70 ; N 5.43; Cl 6.68 ; Fe 10.45°/o. Procedure for the spectrophotometric determination of iron(iII) The pH of the (8 ml) solution containing 10-100 µ;g of iron (III) was adjusted to 2- 2.5 by NaOH or HCl and a glycocoll buffer pH 2.2 (2 ml) was added. The aqueous solution was shaken for 2 min. with 5 ml of 5 X 10-3 M HY in chloroform. The phases were separated and the chloroform solution was transfered into a 10 ml volumetric flask. The remaining aqueous phase was shaken with ca. 3 ml of chloroform, and this extract transfered to the same volumetric flask . The solution was filled to volume with chloroform and absorbance measured at 418 or 465 nm. RESULTS AND DISCUSSION Iron(III) reacted in a moderately acidic solution with HY in 500/o· ethanol. Gradually a violet colour appears, which changes to orange-yellow. These effects were studied spectrophotometrically and results of these measurements are given in Table I. They indicate that, in a water-ethanol solution TABLE I The dependen ce of Amax on Fe (III)-HY molar ratio at varied pH . Concentrati on of iron (III) is 1 x 10-4 M pH ---0.2 0.5 1.0 1.5 2.0 2.5 3.0 3.5 5.0 [Fe] : [HY] I 1 : 1 I.max/nm [Fe] : [HY] I [Fe] : [HY] I· [Fe] : [HY] 1 : 2 I 1 : 3 1 : 10 ------·---- --colourless 575 575 575 575 575 575 575 579 572 570 560 560 570 530 525 520 560 520 520 490 560 520 510 480 520 510 480 470 480 470 470 470 DETERMINATION OF IRON(III) 239 iran(III) and HY form different complexes depending on the iron-HY con-centration rntio and the pH of the solution. The composition of these com-plexes wa:s determined by a modification of Job's method10- 12 and by the Harvey and Manning's method1s. Obtained results indicate the existence of two complexes: FeY2+ and FeY2+. At pH= l.O only a violet complex FeY2+, with absorption maximum at 575 nm is formed. At pH higher than 1.5, two complexes are always present in solution. With an increase of the pH in solution aind the 1initial HY-iron concentration ratio, the concentration of HY2+ increase. At a higher HY-iron concentration ratio and at pH higher than 2.5, the orange-yellow FeY/ complex with absorption maximum at 470 nm is practically the only species present in the solution. The extraction of iron(III) with HY in chloroform was studied spectr©-photometrically and ·radiometrically. The results of these dete11minations show that the optimal pH for the extraction is 1.8- 2.6. Quantitative back-extraction of iron was carried out with a 5 M concentration of HCl, HN03 or HC104 • The visible spectrum of the extracted complex i:n chlorofomn has two maxima, at 418 and 465 nm. The composition of the iron extractable complex was studied spectrophotometrically by Job's method and by the dependence of the iron distribution ratio, D, on the HY concentration in the organic phase. A curve with a slope of 2 was obtained, indicating that two molecules of the reagent are bound to ·one atom of iron. TABLE II Influence of anions on the spectrophotometric determination of iron (III). Concentration of iron (III) 5 x 10-5 M, HY 2.5 X 10-3 M. Anion Iron-anion I Absorbance I Absorbance molar ratio at 418 nm at 465 nm 0.306 0.308 Nitrate 1 : 10000 0.306 0.307 Sulphate 1 : 10000 0.308 0.308 Chloride 1 : 10000 0.307 0.308 Phosphate 1 : 10000 0.310 0.307 Perchlorate 1 : 10000 0.307 0.307 Citrate 1: 10000 0.265 0.266 1 : 1000 0.305 0.307 Tarta.rate 1 : 10000 0.269 0.269 1 : 1000 0.302 0.303 Acetate 1 : 10000 0.265 0.266 1 : 1000 0.298 0.297 1 : 100 0.306 0.307 Fluoride 1 : 1000 0.296 0.298 1 : 100 0.307 0.308 Bromide 1 : 1000 0.303 0.304 Cyanide 1 : 100 0.260 0.261 1 : 10 0.275 0.277 1 : 1 0.292 0.292 Oxalate 1 : 100 0.084 0.083 1 : 10 0.272 0.272 1 : 1 0.290 0.290 240 M. J . HERAK AND B . TAMHINA These results show that only the FeY/ complex is extracted into chloro-form, and the extract!on mechanism can be represented as: Fe3+ ~qq) + c1- (aq) + 2HY (org) ~ FeY2 Cl (or,g) + 2H+ (aq) The quantitative analysis of the complex isolated from chloroform was con-sistent with the formula FeY2 Cl. The solution of the FeY2Cl complex in the- organic phase obeys Lam-bert-Beer's law. The optimal iron concentrations are 1-10 µg/ml. The molar absorptiviity amounts to 6120 at 418 and 465 riin. The absorbance of the solutions are stable for at least several days. Constant absorbance occurs at molar ratio Fe : HY = r: 10. The reprodu~ibility of the method, expressed by standard deviation is 0.2-20/o depending on the iron concentration. The influence of vari.ous ions on the · 1spectrophotometric determination of iron by HY is shown in Table II and III: The majority cif cations and anions have no influence on the determination of iron. Nb(V), Zr(IV) and Ga(III) are extracted with HY forming colourless complexes. In those cases an amount of HY sufficient for the complete· extraction of iron should be added. U(VI), Ti(IV,) V(V), MoEVI), Ta(V), cyanide and oxalate interfere in the determination of iron. TABLE III Influence of cations on the spectrophotometric determination of iron(IIJ). Concentration of iron(III) 5 X 10-5 M, HY 2.5 X 10-3 M . Cation Iron-cation I Absorba1I1ce I Absorbance molar ratio at .418 nm at 465 nm 0.306 I 0.308 Na(!) 1 : 10000 0.306 0.308 K(I) 1 : 10000 0.310 0.311 NH4+ 1 : 10000 0.310 0.310 Mg(II) 1 : 10000 0.306 0.307 Ca(II) 1 : 10000 0.307 0.308 Ni(II) 1 : 10000 0.306 0.306 Al(III) 1 : 10000 0.307 0.307 Cd(Il) 1 : 10000 0.305 0.306 Ba(II) 1 : 10000· 0.302 0.304 Mn(ll) 1 : 5000 0.310 0.3U-Zn(II) · 1 : 5000 0.309 0.310 Co(II) 1 : 10000 0.310 0.309 Cr(III) 1 : 1000 0.315 0.315 Cu(II) 1 : 1000 0.492 0.369 1 : 100· 0.323 0.325 1 : 10 0.320 0.315 Pb(II) 1 : 100 0.301 0.303 Mo(VI) 1 : 10 0.645 0.032 U(VI) 1 : 1 0.406 0.380 Ti(IV) 1 : 1 0.890 0.405 V(V) 1 : 1 0.496 0.509 Zr(IV) 1 : 1 0.313 0.311 Nb(V) 1 : 1 0.315 0.309 Ta(V) 1 : 1 0.009 0.007 Ga(III) 1 : 1 0.310 0.308 DETERMINATION OF IRON(III) 241 REFERENCES 1. M. J . Her a k , M. J a n k o, and K. B 1 a z e vi c, Croat . Chem. Acta 41 (1969) 85. 2. M. Jank o and M. J . Her a k , M i crochim. Acta (1972) 198. 3. M. J. Her a k and M. J an k o, J. Inorg. NucL Chem. 34 (1972) 2627. 4. M. J. Her a k , B . Tam hi n a, and K. J a k op c i c, J. Inorg. Nucl. Chem. 35 (1973) 1665. 5. M. J . Her a k , M. J a n k o, and B. T am hi n a, Microchi m . Acta (1'973) 783. 6. B. Tam hi n a a nd M. J . Her a k , Microchim. Acta (1974) in press. 7. B . Tam hi n a a nd M. J . Her a k , Croat. Chem. Acta 45 (1973) 603. 8. B . Tamhina, M. J . He ra k, and K. Jakopcic, J . Less-Common MetaLs, 33 (1973) 289. 9. B. Tam hi n a, K. J a k op c i c, F. Zorko, and M. J. Her a k, J . Inorg. Nucl. Chem. 36 (1974) 1855. 10. W. C. Ve s burg and G. R. Coop er, J. Amer. Chem. Soc. 63 (1941) 437. 11.R. K . Gould andW. C. Vesburg, J.Amer . Chem.Soc.64(1942)1630. 12. J. H . Yoe and A. E. H ar vey, Jr., J. Amer. Chem. Soc. 70 (1948) 648. 13. A. E . H a r v e y, Jr., and D. L. Manni n g, J . Amer. Chem. Soc. 72 (1950) 4488. SAZETAK Primjena 1-(4-tolil)-2-metil-3-hidroksi-4-piridona za ekstrakciju i spektrofotometrijsko odredivanje zeljeza(III) M . J. Herak i B. Tamhina Opisana je pmmJena 1-(4-tolil)-2-metil-3-hidroksi-4-piridona (HY) za ekstrak-ciju i spektrofotometrijsko odredivanje foljeza(III) . U vodenoj otopini zeljezo(III) i HY stvaraju dva razliCita kompleksa ; F eY z+ i FeY2+, ovisno o molnom omjeru zeljeza i reagensa i o pH otopine. Utvrdeno je da se u organsku fazu ekstrahira samo kompleks F eY2+. ZAVOD ZA ANALITJCKU KEMIJU PRIRODOSLOVNO-MATEMATICKI FAKULTET, ZAGREB i INSTITUT ZA ANORGANSKU I ANALITICKU KEMIJU SVEUCILLSTA U ZAGREBU Primljeno 13. svibnja 1974. 

Application of 1-(4-Tolyl)-2-methyl-3-hydroxy-4-pyridone for the Extraction and Spectrophotometric Determination of Iron(III)

Abstract

Similar works

Full text

Available Versions

HRČAK - Portal of Croatian Scientific and Professional Journals