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Liquid chromatography of metal complex of N-disubstituted dithiocarbamic acids
Journal of Chromatography, 172 0 Ekevier Scientific Publishing
(1979) 384-387 Company, Amsterdam -
Printed in The NetherIands
CHROM. 11,659
Note
Liquid chromatography bamic acids _
of metal
complexes
IV. Separation of mixtures of fn(ll), Cu(ll), Co(ll), Cd(lI) and Fe(ll) diethyldithiocarbamate ance liquid chromatography 0. LI%4,
J. LEHOTAY
of N-disubstituted
dithiocar-
Mn(lI), Ni(ll), pb(lI), Cr(lll), complexes by high-perform-
and E. BRANDSTETEROVA
Department of Anaiytical Chemistry, Slovak Tecizzical University, 880 37 Eratislava (Czechoslovakia)
2nd G. GUIOCHON and H. COLIN Laboratoire de Chimie Analytique C&&x (France)
Physique,
&ore
Poiytechnique,
Route de Sacloy, 91128 Po.!aiFeou
(Received December 1 lth, 1978)
The simultaneous detection and determinatioa of several metal ions in mixtures at trace levels are possible by various instrumental methods. The choice is mainly a matter of convenience, depending on the specific problem and especially the matrix. High-performance liquid chromatography (HPLC) is one of the most recent methods, which permits the simultaneous separation and determination of many individual ions in mixtures. The greatest interest has been devoted to the separation of metal mixtures by ion-exchange chromatography, but liquid-solid and even liquid-liquid chromatography have also been used. Many workers have successfully used for these HPLC separations different aetyiacetonate complexes14; others separated dithizonatess.6*‘0, SchiEbase chelates’, #I-ketoamine?, neutral te’sadentate chelates with fluorinated and non-fluorinated ,8-ketoamino and salicylaldimine ligands9, l-(pyridylazo)-2-naphtol chelates”, diacetylbis(thiobenzoyl)hydrazone chelates”+ and glyoxaIbis(2,2,3,3-tetramethylbutyl)- and diacetylbis(cyclohexyl)thiosemicarbazoneslz. In HPLC, only three papers have dealt with the separation of metal dithiocarbamate (DTC) complexes in spite of the fact that Hulanicki13 pointed out in 1967 the generai possibility of using DTC derivatives for$he concentration of small amounts of many metals by extraction or precipitation followed by their determination usin? various conventional instrumental methods in trace analysis. Recently, Heizmann anti Ballschmiterlz published interesting results on the separation of diethyl-DTC, her.&methyl-DTC and diethoxyethyl-DTC complexes of different metals and Moriyas:: * Tinis paper was presented at the 111.International Symposium on Colunm Liquid Chromar& graph,v, Salzburg, September 27-30, I977. Tie majority of the papers presented at this symposiu-.’ has been published in J. Chromatogr., Vol. 149 (1978).
355
NOTES
and Hashirn~to’~ reported the separation and determination of diethyl-DTC chelates of heavy metals by HPLC on a deactivated silica gel column using n-hexane or cyclohexane-ethyl acetate mixtures. as the solvent. Quite recently O’Laugblin and 0’13rienroreported the separation of seven metal diethyl-DTC chelates by HPLC on Ccrasil(30-50 pm) and pPorasil(l0 pm) columns. In the course of a general study of the HPLC analysis of metal DTC complexes, we have investigated the possibility of separating mixtures of different cations. We have studied the intluence of the nature of the N-substituents on the chromatographic properties of the copper (II) DTC complexes in order to choose an appropriate ligand for the optimal separation of different metals. We have also investigated the idhence of the mobile phase composition on the retention of DTC complexes_ EXPERIMENTAL
All experiments were carried out on a Packard Model 820 high-pressure liquid chromatograph with a UV detector at 254 run. A stainless-steel column (200 x 4.5 mm I.D.) tilled with LiChrosorb SI 60 (particle diameter 10 pm) was used. Chemicals The bisdiethyl-DTC complexes of Zn(II), Cu(EL), Mn(II), Ni(II), Pb(II), Co(H), Cd(H) and Fe(H) and Cu(II) DTC complexes with different substituents on the nitrogen atom (dimethyl, methylpropyl, diisopropyl, methylphenyl and cyclopentamethylene) were prepared according to the usual procedure in the absence of oxygexYs. The Cr(III)trisdiethyl-DTC complex was prepared according to the procedure of Tuljupa and Zeltobrjuch I6. The complexes were recrystallized from chloroform and characterized by elemental analysis, melting point determination and UV spectroscopy. All chemicals were of analytical-reagent grade (Lachema, Bmo, Czechoslovakia). The solvents were dried over magnesium perchlorate and redistilled before use. Procedure
Solutions (0.001 M) of metal DTC complexes in chloroform were freshly For the determination of k’ values, 10~1 of solution were injected using a lo-p1 Hamilbaon syringe. A mixture -of metal N,Ndiethyl-DTC complexes was prepared as a standard solution by mixing equal volumes of 0.01 M solutions of each component. Samples of 5 ~1 of this standard mixture were injected.
prepared for each series of experiments.
RESULTS
AND
DISCUSSION
The results obtained in previous studies17*fsfacilitated the selection of an appropriate mobile phase. We chose chloroform-cyclohexane, which gives the op-
timal results. We investigated the contribution of various N-substituents in the DTC ligand to the overall retention of Cu(IL) complexes. These complexes were chosen in a search for the most suitable substituents, because they exhibit small retentions with the system we have used and the Cu(lJ) complexes with the six N-substituents studied are eluted in an acceptable range of k' values (O-10) (Fig. 1). The calculation of the eluotropic
6O a
405
0
Fig. 1. Relationship between log k’ of Cu(II) bis(N,N-disubstitute)-DTC complexes and &vent eluotropic strength, E”. Column: LiChrosorh SI-60, 200 x 4.6 mm I.D.; particie size, 10pm. 2 = N,N-pentamethy!ene; i&bile phase: chloroform-cyclohexane mixtures. 1 = N,N-Dimethyl: 3 = N-methyl-N-isopropyl; 4 = N,N-diethyl; 5 = N-methyl-N-phenyl; 6 = N,N-diisopropyl. 11, logk’ \
Fig. 2. Relationship between log k’ of N,N-dietbyl-DTC metal complexes and solvent eluotroF~ strength, 9. Column as in Fig. 1. Mobile phase: chloroform-cyclohexane mixtures. Metal complexe: 1 = Z&II); 2 = Cu(I1); 3 = Mn(II); 4 = Ni(I1); 5 = Pb(l1); 6 = Cr(II1); 7 = CaOI); S = CdW 9 = F&II).
NOTES
387
strength of the bimry sohem mixfures was made according to the theory of Snyd#: _ The elution sequenceof these Cu(H) DT% complexeswith the solvent systemsstudied was N,N-diisopropyl- < N-methyl-N-pbeayl- c N,N-die’ihyl- c N-rnetbyi-Nisopropyl- < N,B&pent2methylene- < N,N-dimethyl-DTC. On the basis of f&e results obtained 1?yesekcted the N,N-die~hyr_DrCnpand& for further studies. The infiuence of the composition of the mobile phase on the capacity ratios of the meti N,N-diethyI-DTC- compIexes is iHkstr&ed-in F&--2. According to &is 6-m we chose, 2s the optid mobile phase composition, cycIohexme-10% chloroform (E” = O.IOS). An empIe of the separation of a sykthefic mixture of nine metal DTtI complexes is shown in Fig. 3, which demonstrates the usefulness of HEX for the r;ppidseparation of the m@i complexes studied. .;
, 8
I
.;
P
I
6
20
I
25mhl
Fig.3. Separation of a synthe& mixture of N,N-diethyl-DTC compkxe~ of zn(E), titzr),Mn(Ia,
Ni(II), E%(H), Cr(Hr), COOI), Cd(H) and Fe(H). Column as in Fig. I. Mobile phase: 10% ch!otpform in cyclohcx.zne. inlet pressuqz: 2.5 Mb. Solvent velocity: 0.13 cm-set-‘. Detector: W (254 nm). Sample size: 5 yl of a synthetic mixture ofcomp1ex.s iu ck$orofonn (5.6 lo-’ 151of E-X&compomdf.
The conditions for the extraction of the metis 2s the DTC kompfexes from diEerentaqueous solutions 2nd the quantitzttiveanalysis of trace amounts of metals will be published later. REFERENCES 1 J. F. K. Huber; J. C. Km&
and H. Veening,
Anal. Ckem., 44 (1972)
i554.
2 I. Jonas 2nd B. Norden, Ncziure(Lom.&m), 258 (1975) 597. 3 K. S&oh and N. Suzuki, J. Ckrmzarogr.,
4 D. R. Jones end S. E. Mannhan, Ad. 5 6 7 8 9
109
(1975)333.
Lett.. g-($9775) 569.
K. Lo&en. K. Mueller uld pi. Spitzy, A&zvchim. ACJU, (1975) 602. AM.Lokumilier, P. Heizmnnn and K. Ekdischmiter,J. Ckromafogr., 133 (1977) 156. P. C. Uden and F. H. Wafters, Am!. Claim. AC&r,79 (1975) 175. E. Gaemi, C. F. Laureri, A. Mimgia and 0. Pm&xi, Ancil. C&cm., 48 0976) 1725. P. C. Wden, E. M. Parees and F. H. Walters, Arral. kff.., 8 (E973) 795.
10 A. Gal&, AIL&.Ckk. ACIO~ 57 (1971)399.
II P. Heirmann acd K. Balkchmiter, 2. Ami. Ckem.. 266 (P973) 206. 12 P. Heizmann and K. Bakzhmiter. 1. Ckronuzrugr., 137 (197.7) 153. 13 A. HuImicki, Tafanta, 14 (1967) 1371. 14 M. Moriyasu and Y. Hashimoto, AI&.-L&c., All (1978) 593. 15 G. D. Thorn and R. A. Ludwig, The DiUzimar&~rss cnzfR.ekzkxfCompom&
E~v&:~~-
:6 F. M. Tuijupa and L, P. ZeltoSEjuch, ukr. &Trim.Zk, I (19703 72. ;7 0. L&s, G. Guiachon and H. C&in, J. Ckrmmzfo~~, ITI (1979) 145. ! 8 0. Liska,J. Lehotay, E. Brand.&etesov&and G. Guiochm, f. Chumat&., 171 Cl9791 153. 19 L. R. Snyder, RiwipCes of Adwrption Ckrmrarogmpky, MazeI Bekk.~ NewYork. 1968. 10 J. W. O’Laughiin and T. P. O%ien, Anal. E&Z., (1978) 829.
(1979) 384-387 Company, Amsterdam -
Printed in The NetherIands
CHROM. 11,659
Note
Liquid chromatography bamic acids _
of metal
complexes
IV. Separation of mixtures of fn(ll), Cu(ll), Co(ll), Cd(lI) and Fe(ll) diethyldithiocarbamate ance liquid chromatography 0. LI%4,
J. LEHOTAY
of N-disubstituted
dithiocar-
Mn(lI), Ni(ll), pb(lI), Cr(lll), complexes by high-perform-
and E. BRANDSTETEROVA
Department of Anaiytical Chemistry, Slovak Tecizzical University, 880 37 Eratislava (Czechoslovakia)
2nd G. GUIOCHON and H. COLIN Laboratoire de Chimie Analytique C&&x (France)
Physique,
&ore
Poiytechnique,
Route de Sacloy, 91128 Po.!aiFeou
(Received December 1 lth, 1978)
The simultaneous detection and determinatioa of several metal ions in mixtures at trace levels are possible by various instrumental methods. The choice is mainly a matter of convenience, depending on the specific problem and especially the matrix. High-performance liquid chromatography (HPLC) is one of the most recent methods, which permits the simultaneous separation and determination of many individual ions in mixtures. The greatest interest has been devoted to the separation of metal mixtures by ion-exchange chromatography, but liquid-solid and even liquid-liquid chromatography have also been used. Many workers have successfully used for these HPLC separations different aetyiacetonate complexes14; others separated dithizonatess.6*‘0, SchiEbase chelates’, #I-ketoamine?, neutral te’sadentate chelates with fluorinated and non-fluorinated ,8-ketoamino and salicylaldimine ligands9, l-(pyridylazo)-2-naphtol chelates”, diacetylbis(thiobenzoyl)hydrazone chelates”+ and glyoxaIbis(2,2,3,3-tetramethylbutyl)- and diacetylbis(cyclohexyl)thiosemicarbazoneslz. In HPLC, only three papers have dealt with the separation of metal dithiocarbamate (DTC) complexes in spite of the fact that Hulanicki13 pointed out in 1967 the generai possibility of using DTC derivatives for$he concentration of small amounts of many metals by extraction or precipitation followed by their determination usin? various conventional instrumental methods in trace analysis. Recently, Heizmann anti Ballschmiterlz published interesting results on the separation of diethyl-DTC, her.&methyl-DTC and diethoxyethyl-DTC complexes of different metals and Moriyas:: * Tinis paper was presented at the 111.International Symposium on Colunm Liquid Chromar& graph,v, Salzburg, September 27-30, I977. Tie majority of the papers presented at this symposiu-.’ has been published in J. Chromatogr., Vol. 149 (1978).
355
NOTES
and Hashirn~to’~ reported the separation and determination of diethyl-DTC chelates of heavy metals by HPLC on a deactivated silica gel column using n-hexane or cyclohexane-ethyl acetate mixtures. as the solvent. Quite recently O’Laugblin and 0’13rienroreported the separation of seven metal diethyl-DTC chelates by HPLC on Ccrasil(30-50 pm) and pPorasil(l0 pm) columns. In the course of a general study of the HPLC analysis of metal DTC complexes, we have investigated the possibility of separating mixtures of different cations. We have studied the intluence of the nature of the N-substituents on the chromatographic properties of the copper (II) DTC complexes in order to choose an appropriate ligand for the optimal separation of different metals. We have also investigated the idhence of the mobile phase composition on the retention of DTC complexes_ EXPERIMENTAL
All experiments were carried out on a Packard Model 820 high-pressure liquid chromatograph with a UV detector at 254 run. A stainless-steel column (200 x 4.5 mm I.D.) tilled with LiChrosorb SI 60 (particle diameter 10 pm) was used. Chemicals The bisdiethyl-DTC complexes of Zn(II), Cu(EL), Mn(II), Ni(II), Pb(II), Co(H), Cd(H) and Fe(H) and Cu(II) DTC complexes with different substituents on the nitrogen atom (dimethyl, methylpropyl, diisopropyl, methylphenyl and cyclopentamethylene) were prepared according to the usual procedure in the absence of oxygexYs. The Cr(III)trisdiethyl-DTC complex was prepared according to the procedure of Tuljupa and Zeltobrjuch I6. The complexes were recrystallized from chloroform and characterized by elemental analysis, melting point determination and UV spectroscopy. All chemicals were of analytical-reagent grade (Lachema, Bmo, Czechoslovakia). The solvents were dried over magnesium perchlorate and redistilled before use. Procedure
Solutions (0.001 M) of metal DTC complexes in chloroform were freshly For the determination of k’ values, 10~1 of solution were injected using a lo-p1 Hamilbaon syringe. A mixture -of metal N,Ndiethyl-DTC complexes was prepared as a standard solution by mixing equal volumes of 0.01 M solutions of each component. Samples of 5 ~1 of this standard mixture were injected.
prepared for each series of experiments.
RESULTS
AND
DISCUSSION
The results obtained in previous studies17*fsfacilitated the selection of an appropriate mobile phase. We chose chloroform-cyclohexane, which gives the op-
timal results. We investigated the contribution of various N-substituents in the DTC ligand to the overall retention of Cu(IL) complexes. These complexes were chosen in a search for the most suitable substituents, because they exhibit small retentions with the system we have used and the Cu(lJ) complexes with the six N-substituents studied are eluted in an acceptable range of k' values (O-10) (Fig. 1). The calculation of the eluotropic
6O a
405
0
Fig. 1. Relationship between log k’ of Cu(II) bis(N,N-disubstitute)-DTC complexes and &vent eluotropic strength, E”. Column: LiChrosorh SI-60, 200 x 4.6 mm I.D.; particie size, 10pm. 2 = N,N-pentamethy!ene; i&bile phase: chloroform-cyclohexane mixtures. 1 = N,N-Dimethyl: 3 = N-methyl-N-isopropyl; 4 = N,N-diethyl; 5 = N-methyl-N-phenyl; 6 = N,N-diisopropyl. 11, logk’ \
Fig. 2. Relationship between log k’ of N,N-dietbyl-DTC metal complexes and solvent eluotroF~ strength, 9. Column as in Fig. 1. Mobile phase: chloroform-cyclohexane mixtures. Metal complexe: 1 = Z&II); 2 = Cu(I1); 3 = Mn(II); 4 = Ni(I1); 5 = Pb(l1); 6 = Cr(II1); 7 = CaOI); S = CdW 9 = F&II).
NOTES
387
strength of the bimry sohem mixfures was made according to the theory of Snyd#: _ The elution sequenceof these Cu(H) DT% complexeswith the solvent systemsstudied was N,N-diisopropyl- < N-methyl-N-pbeayl- c N,N-die’ihyl- c N-rnetbyi-Nisopropyl- < N,B&pent2methylene- < N,N-dimethyl-DTC. On the basis of f&e results obtained 1?yesekcted the N,N-die~hyr_DrCnpand& for further studies. The infiuence of the composition of the mobile phase on the capacity ratios of the meti N,N-diethyI-DTC- compIexes is iHkstr&ed-in F&--2. According to &is 6-m we chose, 2s the optid mobile phase composition, cycIohexme-10% chloroform (E” = O.IOS). An empIe of the separation of a sykthefic mixture of nine metal DTtI complexes is shown in Fig. 3, which demonstrates the usefulness of HEX for the r;ppidseparation of the m@i complexes studied. .;
, 8
I
.;
P
I
6
20
I
25mhl
Fig.3. Separation of a synthe& mixture of N,N-diethyl-DTC compkxe~ of zn(E), titzr),Mn(Ia,
Ni(II), E%(H), Cr(Hr), COOI), Cd(H) and Fe(H). Column as in Fig. I. Mobile phase: 10% ch!otpform in cyclohcx.zne. inlet pressuqz: 2.5 Mb. Solvent velocity: 0.13 cm-set-‘. Detector: W (254 nm). Sample size: 5 yl of a synthetic mixture ofcomp1ex.s iu ck$orofonn (5.6 lo-’ 151of E-X&compomdf.
The conditions for the extraction of the metis 2s the DTC kompfexes from diEerentaqueous solutions 2nd the quantitzttiveanalysis of trace amounts of metals will be published later. REFERENCES 1 J. F. K. Huber; J. C. Km&
and H. Veening,
Anal. Ckem., 44 (1972)
i554.
2 I. Jonas 2nd B. Norden, Ncziure(Lom.&m), 258 (1975) 597. 3 K. S&oh and N. Suzuki, J. Ckrmzarogr.,
4 D. R. Jones end S. E. Mannhan, Ad. 5 6 7 8 9
109
(1975)333.
Lett.. g-($9775) 569.
K. Lo&en. K. Mueller uld pi. Spitzy, A&zvchim. ACJU, (1975) 602. AM.Lokumilier, P. Heizmnnn and K. Ekdischmiter,J. Ckromafogr., 133 (1977) 156. P. C. Uden and F. H. Wafters, Am!. Claim. AC&r,79 (1975) 175. E. Gaemi, C. F. Laureri, A. Mimgia and 0. Pm&xi, Ancil. C&cm., 48 0976) 1725. P. C. Wden, E. M. Parees and F. H. Walters, Arral. kff.., 8 (E973) 795.
10 A. Gal&, AIL&.Ckk. ACIO~ 57 (1971)399.
II P. Heirmann acd K. Balkchmiter, 2. Ami. Ckem.. 266 (P973) 206. 12 P. Heizmann and K. Bakzhmiter. 1. Ckronuzrugr., 137 (197.7) 153. 13 A. HuImicki, Tafanta, 14 (1967) 1371. 14 M. Moriyasu and Y. Hashimoto, AI&.-L&c., All (1978) 593. 15 G. D. Thorn and R. A. Ludwig, The DiUzimar&~rss cnzfR.ekzkxfCompom&
E~v&:~~-
:6 F. M. Tuijupa and L, P. ZeltoSEjuch, ukr. &Trim.Zk, I (19703 72. ;7 0. L&s, G. Guiachon and H. C&in, J. Ckrmmzfo~~, ITI (1979) 145. ! 8 0. Liska,J. Lehotay, E. Brand.&etesov&and G. Guiochm, f. Chumat&., 171 Cl9791 153. 19 L. R. Snyder, RiwipCes of Adwrption Ckrmrarogmpky, MazeI Bekk.~ NewYork. 1968. 10 J. W. O’Laughiin and T. P. O%ien, Anal. E&Z., (1978) 829.