Determination of trace impurities in high-purity iron using salting-out of polyoxyethylene-type surfactants

To an iron sample solution was added polyoxyethylene-4-isononylphenoxy ether (PONPE, nonionic surfactant, average number of ethylene oxides 7.5) and the surfactant was aggregated by the addition of lithium chloride. The iron(III) matrix was collected into the condensed surfactant phase in >99.9% yields, leaving trace metals [e.g., Ti(IV), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), and Bi(III)] in the aqueous phase. After removing the surfactant phase by centrifugation, the remaining trace metals were concentrated onto an iminodiacetic acid-type chelating resin. The trace metals were desorbed with dilute nitric acid for the determination by inductively coupled plasma-mass spectrometry or graphite-furnace atomic absorption spectrometry. The proposed separation method allowed the analysis of high-purity iron metals for trace impurities at low μg g⁻¹ to ng g⁻¹ levels.     

Analytische Multielement-Anreicherung an metallhydroxidbeladener Cellulose

Zusammenfassung Es wird die analytische Multielement-Anreicherung an metallhydroxydbeladener Cellulose beschrieben. Metallhydroxide [z.B. Fe(OH)₃, In(OH)₃] in geringen Mengen auf einem anderen Spurenfänger (z. B. Cellulose) fixiert, zeigen ein hohes Sorptionsvermögen für Elementspuren [z. B. Al, As, Be, Bi, Cd, Co, Cr(III), Cu, Lanthanoide, Mn, Mo, Ni, Pb, Sn, Ti, V, Zn] im ng/l- bis g/ l-Bereich. Die Spuren-VerteilungskoeffizientenK _d an dem synergistisch wirkenden Mischkollektor [Cellulose/1% Fe(III) bzw. Cellulose/2% In(III)] erreichen auch in konzentrierten Salzlösungen Werte von 10⁴ bis 10⁵. Komplexierende Wasserinhaltsstoffe (z.B. Citrat, Huminsäure, Phosphat) stören die Spurenanreicherung kaum, abgesehen von starken Chelatbildnern (z.B. NTA). Hauptvorteile gegenüber der herkömmlichen Mitfällung an Metallhydroxiden sind eine vereinfachte Handhabung (Schüttelverfahren) sowie erheblich verringerte Kollektormengen [z. B. einige hundert Mikrogramm Fe(III), In(III)]. Nach Elution mit 2 M HCl werden die angereicherten Elementspuren durch Flammen-AAS (Injektionsverfahren) bzw. ICP-AES bestimmt. Die Nachweisgrenzen (3) der wasseranalytischen Verbundverfahren liegen vielfach bei 0,1 g/l, die relativen Standardabweichungens _r bei 0,03 bis 0,05.

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Analytical multielement preconcentration on metal hydroxide-coated cellulose

Summary The analytical preconcentration of trace metals on metal hydroxide-coated cellulose is characterized. Metal hydroxides [e.g., Fe(OH)₃, In(OH)₃], in small amounts fixed on another adsorbent (e.g., cellulose), strongly bind many trace metals [e.g., Al, As, Be, Bi, Cd, Co, Cr(III), Cu, lanthanoids, Mn, Mo, Ni, Pb, Sn, Ti, V, Zn] in the ng/l to g/l range. The sorption of trace metals on the synergistically acting collector [e.g., cellulose/1% Fe(III), cellulose/2% In(III)] proceeds with half times of some minutes. Furthermore, the element distribution coefficientsK _d between adsorbent and strong saline solutions are of the order 10⁴ to 10⁵. Dissolved complexing matters (e.g., citrate, humic acid, phosphate) with the exception of chelating agents (e.g., NTA) do not interfere. The main advantages compared with the conventional co-precipitation of trace metals with metal hydroxides, are a simplified procedure (batch method) and lowered metal amounts [e.g., some 100 g Fe(III), In(III)]. After elution (2 M HCl) the preconcentrated trace metals are determined by flame-AAS (injection technique) and ICP-AES. With the analytical procedure developed for water analysis, detection limits (3) of 0.1 g/l and relative standard deviations of 0.03 to 0.05 can be achieved for many elements in surface-, mineral- and sea-water.

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Teilweise vorgestellt auf der Jahrestagung 1984 der Fachgruppe Wasserchemie der GDCh, Bad Homburg v. d. H., 28.–30. 5.1984     

Analytical Application of the Binary and Ternary Complexes of 2,10-Disubstituted Phenothiazines

Abstract

Phenothiazines (PT) are an important family of compound from a medical point of view. They are widely used among the tricyclic antidepressants. Their application in therapy requires methods for their determination in pharmaceuticals and body fluids. The extractive-spectrophotometric methods are very useful for these determinations. They are based on the formation of the binary and ternary complexes. Phenothiazines react with some organic substances (e.g., picric acid, alizarin S, bromocresol green, and triphenylmethane dyes) as well as with thiocyanate or halide complexes of metals [e.g., Co(II), Pd(II), Fe(III), Cr(III), Au(III), Ti(IV), Pt(IV), Mo(V), W(V), U(VI)] forming well-defined ion-association compounds. The compounds are sparingly soluble in water but quantitatively extracted from the aqueous phase into organic solvents. The extracts are intensely colored and stable for a few days. These properties are the basis for utilizing the binary and ternary complexes of phenothiazines in chemical and pharmaceutical analysis. This review described the analytical application of these complexes.     

Coordination complexes bearing potentially tetradentate phenoxyamine ligands

A series of metal complexes containing potentially tetradentate phenoxyamine ligands is described. The ligands are found to bind to main-group metals and first-row transition-metal centres with variable denticity depending upon the requirements of the particular metal centre. Bidentate [Al(III)], tridentate [Mg(II), Ca(II), Zn(II)] and tetradentate [K(I), Cr(III), Fe(II), Co(II)] binding modes have been established unambiguously through single-crystal X-ray structure determinations.     

Zur Methodik der Elementspezies-Analytik in Lebensmitteln

Summary Potentiometry with an ion-selective electrode as well as a cation-chelate-exchange procedure (combined with AAS) are presented as useful methods for the determination of stabilities of element species, for example of calcium in milk. The cation-exchange procedure is also applicable to other metals (e.g., magnesium) and other foodstuffs (e.g., meat extracts). New results of Ca- and Mg-extractabilities by the use of different aqueous extraction solutions (including enzymic solutions) are reported. Ultrafiltration, dialysis and gel-chromatography are further methods especially for the separation and analysis of protein-containing element species. Unoccupied binding fields can be detected after addition of Cu(II) ions by combination of gel chromatography and UV/VIS spectroscopy, as shown by example of rape-flour. The experiences gained in the analysis of element species in foodstuffs are combined to a strategy of analysis.     

Solvent extraction of zinc by 2-hexylpyridine in benzene from aqueous mineral acid — Thiocyanate media

Solvent extraction of Zn(II) by 2-hexylpyridine (HPy) in benzene has been studied from aqueous mineral acid—thiocyanate media. The extraction, though dependent on the acidity of the aqueous phase, is poor from mineral acids (HCl, HNO₃ or H₂SO₄). Addition of 0.02M KSCN to the aqueous phase enhances the distribution ratio by a factor of almost one thousand. The stoichiometry of the extracted complex established by the usual slope analysis method indicates that an ionic type complex, e.g. Zn(SCN)₄·(HPyH)₂, is responsible for extraction. Complexing anions like acetate, oxalate or citrate at 1 M concentration mask the extraction of Zn(II) almost completely. Separation factors determined at optimal conditions (0.1M HPy in benzene −0.05M H₂SO₄+0.2M SCN⁻) indicate that Zn(II), along with Hg(II), can be separated in a single extraction from a number of metals, e.g. Cs(I), Sr(II), Ln(III), Y(III), Cr(III) and (VI). Other metals of interest like Cu(II), Co(II), Fe(III), Mo(VI), U(VI) and Tc(VII) are coextracted but the separation factors are large enough to allow separation in a multistage extraction process.     

Multielement-preconcentration for atomic spectroscopy by sorption of dithiocarbamate-metal complexes (e.g., HMDC) on cellulose collectors

Summary The analytical preconcentration of trace metals from saline solutions by sorption of their dithiocarbamates on reversed-phase cellulose is reported. Heavy metals [e.g., Bi, Cd, Co, Cr(III), Cu, Fe, Hg, In, Ni, Pb, Tl, Yb, Zn] dissolved at the ng/l to g/l level can be quantitatively fixed as dithiocarbamates (e.g., HMDC) on cellulose within a few minutes. In salt solutions and without use of any carriermetal the distribution coefficients K _d are of the order 10⁴ to 10⁵ (ml/g) in the pH range between 4 and 10. The K _d values of dithiocarbamates on RP cellulose (e.g., acetylated cellulose) are higher by a factor of 5 to 10 than those on conventional RP sorbents (e.g., C₁₈, C₆H₅). Moreover, the chemical blanks caused by the cellulose collector (batch and column procedure) are below the detection limits of the determination methods used (flame-AAS, graphite furnace-AAS, ICP-OES), Cu, Fe and Zn excepted. Combined with the above atomic spectroscopy methods, the multielement preconcentration with the aid of HMDC complexes is applied to the determination of trace metals in natural waters (including sea water), biological matters (e.g., urine, bovine liver) and high-purity metals (e.g., Al). The accuracy and precision of the developed analytical procedure are confirmed by trace determinations in standard reference materials (e.g., NBS 1577, Alusuisse 112/02).

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Multielement-Voranreicherung für die Atomspektroskopie durch Sorption von Dithiocarbamat-Metallkomplexen an Cellulose-Kollektoren

     

Synthesis of Two N,N′-bis(N,N-dialkylamide) Derivatives of Diethylenetriaminepentaacetic Acid and the Stabilities of Their Complexes with Gd3+, Ca2+, Cu2+, and Zn2+

Two bis(N,N-dialkylamide) derivatives of DTPA [(carboxymethyl)iminobis (ethylenenitrilo) tetraacetic acid], DTPA-BDMA = the bis(N,N-dimethylamide) and DTPA-BDEA = the bis(N,N-diethylamide) were synthesized. Their protonation constants were determined by potentiometric titration in 0.10 M Me₄NNO₃ and by NMR pH titration at 25.0 ± 0.1 °C. Stability and selectivity constants were measured to evaluate the possibility of using the corresponding gadolinium(III) complexes for magnetic resonance imaging contrast agents. The stability constants of gadolinium(III), copper(II), zinc(II), and calcium(II) complexes with DTPA-BDMA and DTPA-BDEA were investigated quantitatively by potentiometry. The stability constant for gadolinium(III) complexes is larger than those for Ca(II), Zn(II), and Cu(II) complexes. The selectivity constants and modified selectivity constants of the amides for Gd³⁺ over endogenously available metal ions were calculated. Effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media is assessed by comparing pM values at physiological pH 7.4. Spin-lattice relaxivity values R₁ for Gd(III) complexes were also determined. The observed relaxivity values were found to decrease with increasing pH in the acid range below pH 4 and relaxivity values became invariant with respect to pH changes over the range of 4–10. ¹⁷O NMR shifts showed that the [Dy(DTPA-BDMA)] and [Dy(DTPA-BDEA)] complexes had one inner-sphere water molecule. Water proton spin-lattice relaxation rates for the [Gd(DTPA-BDMA)] and [Gd(DTPA-BDEA)] complexes were also consistent with one inner-sphere gadolinium(III) coordination position.     

Development of liquid-liquid extraction and separation method for ruthenium(III) with 2-octylaminopyridine from succinate media: Analysis of catalysts

Ruthenium(III) has been efficiently extracted from 0.05 M sodium succinate at pH 9.5 by 2-octylaminopyridine in xylene and stripped with aqueous 10% (w/v) thiourea solution and determined spectrophotometrically. Various parameters viz., pH, weak acid concentration, reagent concentration, stripping agents, contact time, loading capacity, aq.: org. volume ratio, solvent has been thoroughly investigated for quantitative extraction of ruthenium(III). The utility of method was analyzed by separating the ruthenium(III) from binary mixture along with the base metals like Cu(II), Ag(I), Fe(II), Co(II), Bi(III), Zn(II), Ni(II), Se(IV), Te(IV), Al(III) and Hg(II) as well as platinum group metals (PGMs). Ruthenium(III) was also separated from ternary mixtures like Os(VIII), Pd(II); Pd(II), Pt(IV); Pd(II), Au(III); Pd(II), Cu(II); Fe(II), Cu(II); Ni(II), Cu(II); Co(II), Ni(II); Se(IV), Te(IV); Rh(III), Pd(II); Fe(III), Os(VIII). The stoichiometry 1: 2: 1 (metal: succinate: extractant) of the proposed complex was determined by slope analysis method by plotting graph of logD _[Ru(III)] versus logC _[2-OAP] and logD _[Ru(III)] versus logC _[succinate]. The interference of various cations and anions has been studied in detail and the statistical evaluations of the experimental results are reported. The method was successfully applied for the analysis of ruthenium in various catalysts, synthetic mixtures corresponding to the composition of alloys and minerals.     

Potentiometric studies on the complexes of some trivalent rare earths with 5-chloropyridine-2,3-diol

The complexes of some rare earths [Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III), and Ho(III)] with 5-chloropyridine-2,3-diol (CPD) were studied potentiometrically in 50% dioxane-water at a ionic strength of 0.1M (NaClO₄) at 35±0.1 °C. The proton-ligand stability constant ofCPD and the stability constants of its complexes with the metals have been determined using theCalvin-Bjerrum technique as modified byIrving andRossotti. The order of the stability constants is found to be Ce < Pr < Nd < Sm < Tb < Dy < Ho.

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Potentiometrische Untersuchungen der Komplexe einiger trivalenter Seltenerdmetalle mit 5-Chlorpyridin-2,3-diol

Zusammenfassung Es wurden die Komplexe von Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III) und Ho(III) mit 5-Chlorpyridin-2,3-diol (CPD) in 50% Dioxan-Wasser bei einer Ionenstärke von 0,1M (NaClO₄) und einer Temperatur von 35±0,1 °C potentiometrisch untersucht. Die Proton-Ligand-Stabilitätskonstante vonCPD und die Stabilitätskonstanten der Metallkomplexe wurden nach der Methode vonCalvin-Bjerrum mit derIrving-Rossotti-Modifikation bestimmt. Die Reihenfolge der Stabilitätskonstanten ergab sich folgendermaßen: Ce < Pr < Nd < Sm < Tb < Dy < Ho.

     

New sorbents based on organosilicon guanidine derivatives

Monomeric and polymeric organosilicon derivatives of 1-acetylguanidine, which exhibits sorption properties, were synthesized. The organosilicon polymers prepared were studied as sorbents for heavy [Hg(II)] and noble [Ag(I), Au(III), Rh(III), Pd(II), Pt(IV)] metals. They actively take up platinum group metals and exhibit metallochromic properties by analogy with the starting compound, 1-acetylguanidine. Their interaction with all the elements studied is accompanied by coloration. The initial monomers exhibit similar metallochromic properties.     

Synthesis of Two Derivatives of 3,6,9‐tri(carboxymethyl)‐3,6,9‐triazaundecanedioic Acid and the Stabilities of Their Complexes with Ca2+, Cu2+, Zn2+, Dy3+ and Gd3+

Two N‐2‐hydroxy‐1‐phenylethyl and N‐2‐hydroxy‐2‐phenylethyl derivatives of DTPA (3,6,9‐tri(carboxymethyl)‐3,6,9‐triazaundecanedioic acid), DTPA‐H1P = 3,9‐di(carboxymethyl)‐6‐2‐hydroxy‐1‐phenylethyl‐3,6,9‐triazaundecanedioic acid, and DTPA‐H2P = 3,9‐di(carboxymethyl)‐6‐2‐hydroxy‐2‐phenylethyl‐3,6,9‐triazaundecanedioic acid were synthesized. Their protonation constants were determined by Potentiometric titration in 0.10 M Me₄NNO₃ and by NMR pH titration at 25.0 ± 0.1°C. The formations of lanthanide(III), copper(II), zinc(II) and calcium(II) complexes were investigated quantitatively by potentiometry. The stability constant for Gd(III) complex is larger than those for Ca(II), Zn(II) and Cu(II) complexes with these two ligands. The selectivity constants and modified selectivity constants of the DTPA‐H1P and DTPA‐H2P for Gd(III) over endogenously available metal ions were calculated. Comparing pM values at physiological pH 7.4 assesses effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media. The observed water proton relaxivity values of [Gd(DTPA‐H1P)]^? and [Gd(DTPA‐H2P)]^? became constant with respect to pH changes over the range of 4‐10. ¹⁷O NMR shifts showed that the [Dy(DTPA‐H1P)]^? and [Dy(DTPA‐H2P)]^? complexes at pH 6.30 had 1.91 and 2.28 inner‐sphere water molecules, respectively. Water proton spin‐lattice relaxation rates of [Gd(DTPA‐H1P)]^? and [Gd(DTPA‐H2P)]^? complexes were also consistent with the inner‐sphere Gd(III) coordination.     

Os(II)-nitrosyl and Os(II)-dinitrogen complexes from reactions between Os(VI)-nitrido and hydroxylamines and methoxylamines

Reactions between the Os(VI)-nitrido salts (e.g., trans-[Os(VI)(tpy)(Cl)(2)(N)]PF(6) (tpy = 2,2':6',2"-terpyridine), cis-[Os(VI)(tpy)(Cl)(2)(N)]PF(6), and fac-[Os(VI)(tpm)(Cl)(2)(N)]PF(6) (tpm = tris(pyrazol-1-yl)methane)) and the hydroxylamines (e.g., H(2)NOH and MeHNOH) and the methoxylamines (e.g., H(2)NOMe and MeHNOMe) in dry MeOH at room temperature give three different types of products. They are Os(II)-dinitrogen (e.g., trans-, cis-, or fac-[Os(II)-N(2)]), Os(II)-nitrosyl [Os(II)-NO](+) (e.g., trans- or cis-[Os(II)-NO](+)), Os(IV)-hydroxyhydrazido (e.g., cis-[Os(IV)-N(H)N(Me)(OH)](+)), and Os(IV)-methoxyhydrazido (e.g., trans-/cis-[Os(IV)-N(H)N(H)(OMe)](+), and trans-/cis-[Os(IV)-N(H)N(Me)(OMe)](+)) adducts. The products depend in a subtle way on the electron content of the starting nitrido complexes, the nature of the hydroxylamines, the nature of the methoxylamines, and the reaction conditions. Their appearance can be rationalized by invoking the formation of a series of related Os(IV) adducts which are stable or decompose to give the final products by two different pathways. The first involves internal 2-electron transfer and extrusion of H(2)O, MeOH, or MeOMe to give [Os(II)-N(2)]. The second which gives [Os(II)-NO](+) appears to involve seven-coordinate Os(IV) intermediates based on the results of an (15)N-labeling study.     

Extraktionsmethode zur Trennung kleiner Tellurmengen von Begleitelementen

Zusammenfassung Zur Trennung von Tellur aus Lösungen mit komplizierter Zusammensetzung wurde eine kombinierte Extraktionsmethode entwickelt. Die Extraktion von Eisen(III), Arsen(V), Antimon(V), Gold(III), Thallium(III), Wismut(III), Zinn(IV) und Selen(IV) erfolgt mit Diisopropyläther aus 8 M Salzsäure, wobei das gesamte Te(IV) in der wäßrigen Phase verbleibt. Diese wird dann mit Methylisobutylketon aus 4 M Salzsäure extrahiert, während in der wäßrigen Phase Kupfer(II), Aluminium(III), Silber(I), Nickel (II), Kobalt(II), Zink(II), Cadmium(II) und Blei(II) verbleiben. Die vollständige Abtrennung der Begleitelemente des Tellurs erfolgt durch zusätzliche Extraktion ihrer Kupferronate mit Methylisobutylketon bei pH 3–5. Das vorgeschlagene Extraktionsverfahren kann mit jeder bekannten Methode zur Bestimmung geringer Tellurmengen kombiniert werden.

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Extraction method for the separation of small quantities of tellurium from accompanying elements

A new combined solvent extraction method is proposed for the separation of tellurium from solutions of complex composition. Iron(III), arsenic(V), antimony(V), gold(III), thallium(III)J bismuth(III), tin(IV) and selenium(IV) are extracted with diisopropyl ether from 8 M hydrochloric acid. Under these conditions tellurium(IV) is quantitatively retained in the aqueous phase. Subsequently tellurium(IV) is extracted from 4 M hydrochloric acid with methylisobutyl ketone, so that copper(II), aluminium(III), silver(I), nickel(II), cobalt(II), zink(II), cadmium(II) and lead(II) remain in. the aqueous phase. The complete separation of the accompanying elements is realized by an additional extraction of their cupferronates with methylisobutyl ketone at pH 3–5. The separation described can be combined with any known method for the determination of small amounts of tellurium(IV).

     

Trace metal speciation in sea water — a paper electrophoretic approach

Stability constants of individual trace metal complexes form the basis for calculations predicting the distribution of trace metal species in complexing media, such as sea water. In this study, the electrophoretic mobility of radiotracer ²¹⁰Pb is measured as a function of ligand concentration in chloride and sulfate solutions of constant ionic strength and temperature. A theoretically-derived expression, relating mobility to ligand concentration and complex stability constants, is fitted by the method of least squares to the experimental data to obtain estimates of the conditional stability constants of lead(II) chloro and sulfato complexes at 23°C and ionic strength 0.7 i.e., under conditions resembling those of ocean water. The values obtained are: log β₁ = 0.999 ± 0.014, log β₂ = 1.037± 0.032, log β₃ = 1.250 ± 0.015 for lead(II) chloro complexes, and log β₁ = 1.048 ± 0.015 and log β₂ = 1.183 ± 0.025 for lead(II) sulfato complexes. Experiments with eight other metal ions [Au(III), Bi(III), Cd(II), Co(II), Cu(II), Hg(II), Ni(II), and Po(IV)] and with sea water as electrolyte indicate the general applicability of the method.     

Collection of trace metals with cationic surfactant-silica particles followed by flotation with an anionic surfactant for seawater analysis

The analysis of seawater for trace metals is important for pollution monitoring and better understanding of marine systems. The present paper describes an efficient preconcentration method for the determination of trace metals in seawater. Trace metals [Ni(II), Cu(II), Ga(III), Cd(II), Pb(II), and Bi(III)] in 1,000 mL of seawater sample were complexed with ammonium pyrrolidinedithiocarbamate and sorbed onto silica particles covered with cetyltrimethylammonium chloride. After the addition of sodium dodecyl sulfate, the particles were floated to the solution surface by bubbling and then collected by suction. The trace metals were desorbed with dilute nitric acid and determined by inductively coupled plasma–mass spectrometry. The rapid 200-fold preconcentration was demonstrated with certified seawater samples.     

Synthesis, complexation and water exchange properties of Gd(III)-TTDA-mono and bis(amide) derivatives and their binding affinity to human serum albumin

With the objective of tuning the lipophilicity of ligands and maintaining the neutrality and stability of Gd(III) chelate, we designed and synthesized two bis(amide) derivatives of TTDA, TTDA-BMA and TTDA-BBA, and a mono(amide) derivative, TTDA-N-MOBA. The ligand protonation constants and complex stability constants for various metal ions were determined in this study. The identification of the microscopic sites of protonation of the amide ligand by 1H NMR titrations show that the first protonation site occurs on the central nitrogen atom. The values of the stability constant of TTDA-mono and bis(amide) complex are significantly lower than those of TTDA and DTPA, but the selectivity constants of these ligands for Gd(III) over Zn(II) and Cu(II) are slightly higher than those of TTDA and DTPA. On the basis of the water-exchange rate values available for [Gd(TTDA-BMA)(H2O)], [Gd(TTDA-BBA)(H2O)] and [Gd(TTDA-N-MOBA)(H2O)]-, we can state that, in general, the replacement of one carboxylate group by an amide group decreases the water-exchange rate of the gadolinium(III) complexes by a factor of about three to five. The decrease in the exchange rate is explained in terms of a decreased steric crowding and charge effect around the metal ion when carboxylates are replaced by an amide group. In addition, to support the HSA protein binding studies of lipophilic [Gd(TTDA-N-MOBA)(H2O)]- and [Gd(TTDA-BBA)(H2O)] complexes, further protein-complex binding was studied by ultrafiltration and relaxivity studies. The binding constants (KA) of [Gd(TTDA-N-MOBA)(H2O)]- and [Gd(TTDA-BBA)(H2O)] are 8.6 x 10(2) and 1.0 x 10(4) dm3 mol(-1), respectively. The bound relaxivities (r1(b)) are 51.8 and 52 dm3 mmol(-1) s(-1), respectively. The KA value of [Gd(TTDA-BBA)(H2O)] is similar to that of MS-325 and indicates a stronger interaction of [Gd(TTDA-BBA)(H2O)] with HSA.