Arsenazo complex

The following table lists the molar absorptivities for the Arsenazo complexes of copper and barium at selected wavelengths. " Determine the optimum wavelengths for the analysis of a mixture of copper and barium. 

The rate of Sm(III) dissociation from humic acid was studied using a ligand exchange technique. A solution of the Sm(III)-humate complex was equilibrated for a fixed time, then an aliquot of arsenazo III was added. The Sm(III)- arsenazo III complex is so stable (9) that it prevents reformation of the Sm(III)-humate. The rate of Sm(III)-Ars complex formation is quite rapid (9) and we found that the observed formation of the Sm(III)-arsenazo complex was determined by the rate of dissociation of the Sm(III)-humate. The formation of the Sm(III)-Ars complex was monitored spectrophotometrically by the increase in absorbance at 665 nm. Reactions were monitored either with a Milton Roy Spectronic 1201 (ti/2 ... 

Atomic absorption spectroscopy is a preferred method in clinical chemistry. However, UV/Vis spectrometry by use of chelating methods combined with photometry of chromophores offers simple and fast approaches. Examples are methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS 1990) taking ferrocene for Fe, eliminating interferences by Cu by addition of thiourea. Mg is determined by addition of xylidyl blue, Ca by use of o-cresolphthalein or arsenazo complexes. Interferences by Mg are reduced by addition of 8-hydroxyquinoline. Further chromophores and complexing agents are discussed in subsequent chapters and elsewhere [39]. 

Only slightly less accurate ( 0.3—0.5%) and more versatile in scale are other titration techniques. Plutonium maybe oxidized in aqueous solution to PuO " 2 using AgO, and then reduced to Pu" " by a known excess of Fe", which is back-titrated with Ce" ". Pu" " may be titrated complexometricaHy with EDTA and a colorimetric indicator such as Arsenazo(I), even in the presence of a large excess of UO " 2- Solution spectrophotometry (Figs. 4 and 5) can be utilized if the plutonium oxidation state is known or controlled. The spectrophotometric method is very sensitive if a colored complex such as Arsenazo(III) is used. Analytically usehil absorption maxima and molar absorption coefficients ( s) are given in Table 10. Laser photoacoustic spectroscopy has been developed for both elemental analysis and speciation (oxidation state) at concentrations of lO " — 10 M (118). Chemical extraction can also be used to enhance this technique. 

MIXED-LIGAND COMPLEXES (MLC) OF La WITH AMINOPHOSPHONIC ACID GRAFTED ON SILICA AND ARSENAZO I, III AND XYLENOLE ORANGE... 

As the result of the performed investigations was offered to make direct photometric determination of Nd microgram quantities in the presence of 500-fold and 1100-fold quantities of Mo and Pb correspondingly. The rare earth determination procedure involves sample dissolution in HCI, molybdenum reduction to Mo (V) by hydrazine and lead and Mo (V) masking by EDTA. The maximal colour development of Nd-arsenazo III complex was obtained at pH 2,7-2,8. The optimal condition of Nd determination that was established permit to estimate Nd without separation in solution after sample decomposition. Relative standard deviations at determination of 5-20 p.g of Nd from 0,1 g PbMoO are 0,1-0,03. The received data allow to use the offered procedure for solving of wide circle of analytical problems. 

The results of the complexation study of Cu(II), Pb(II), Zn(II), Fe(III), Hg(II), Cd(II), Sn(IV), Zr(IV), Ti(IV) with arsenazo III, sulfonazo III, SPADNS, Eriochrome T, Acid Chrome Dai k Blue, Xylenol Orange, Methyl Thymol Blue, Pyrocatechol Violet, Chrome Azurol S, Eriochrome Cyanin R, Basic Blue K, Methyl Violet, Brilliant Green, Rhodamine C and Astraphoxin in solid phase. The obtained data ai e used for the working out of a new method of metal determination. 

Arsenazo (III) to produce a colored complex, which can be determined with standard colorimetric methods. Arsenic compounds are highly toxic. 

Hirose and Sugimura [89] investigated the speciation of plutonium in seawater using adsorption of plutonium (IV)-xylenol orange and plutonium-arsenazo (III) complexes on the macroreticular synthetic resin XAD-2. Xylenol orange was selective for plutonium (IV) and arsenazo (III) for total plutonium. Plutonium levels were determined by a-ray spectrometry. 

Buryak and Severin have described the use of dynamic libraries of Cu(II) and Ni(II) complexes as sensors for tripeptides [61]. A notable aspect of this work is that as isolation of the metal complexes is not necessary (sensing is accomplished by observing changes in the UV-vis spectrum), potential concerns over the lability of coordination complexes do not apply. Specifically, three common dyes [Arsenazo I (41), Methyl Calcein Blue (42), and Glycine Cresol Red (43), Fig. 1.18] were mixed with varying ratios and total concentrations of Cu(II) and Ni(II) salts in a 4X5 array. Previous work had demonstrated that these conditions produced equilibrating mixtures of 1 1 and 2 1 homo- and heteroleptic complexes [62], These arrays were able to clearly and unambiguously differentiate tripeptides based on the differential pattern of response. The Severin laboratory has... 

Chromium(iii) has been shown to complex with arsenazo(i) at the hydroxy-groups on the naphthalene nucleus. ... 

Protactinium is separated by solvent extraction and anion exchange processes by using sulfate solutions. After chemical separation, the protactinium salts are ignited to a pentoxide, Pa205, which may be converted into an arsenazo(III) complex. The absorbance of the solution is measured at 630 nm with a spectrophotometer. Protactinium-231 is an alpha emitter and also forms photons at 300 KeV, which can be measured by various radioactive counters and spectrophotometric techniques. Protactinium also can be measured by neutron activation analysis. 

X-ray structure showed octahedral Yb06 groups to be present.251 Ion exchange, dialysis and spectrophotometry using Arsenazo-III have been used to study the hydrolysis of the hydrated Y3+ ion at 10-5 to 10-2 M and pH 1 to 9. Mono- and poly-nuclear complexes were present, and Kx for Y(OH)-aq was 2.52 x 106.252... 

A colorimetric method based on the inhibitory effect of EDTA on the Mn(II) catalyzed oxidation of malachite green by periodate was reported [32]. An alternative method based on using Fe(III) instead of Mn(II) was proposed [33]. The reduction of the absorbance of Bi(III) bromo-pyrogallol red tenside ternary complex upon the addition of EDTA has been exploited for its determination. Calibration curves obtained at 650 nm were linear over the range of 0.2-6 pg/mL of EDTA [34]. EDTA in ophthalmic solutions could be assayed by spectrophotometric titration using Mg(II) as the titrant and Arsenazo I as the indicator. The working range was 0.05-2 pg/mL [35]. 

The luminescence characteristics of four complexes formed with arsenazo (I and II) and thorin (I and II) dyes (fig. 67) as well as those of the corresponding ternary complexes with phen have been investigated in aqueous solution. In presence of Ybm ions, 1 1 complexes are formed, except for thorin I, which yields a 1 2 (Yb L) complex. As a consequence, for thorin I only one phen molecule is present, yielding a 1 2 1 (Yb L phen) ternary complex, while 1 1 2 stoichiometries are observed for the three other complexes. Addition of phen results in a significant enhancement (2- to 7-fold) of the luminescence quantum yields, which reach a maximum value of 0.13% for the complex with arsenazo I. As a consequence, the detection limits are lowered by similar factors, from 2 to 8. 

Kinetics of formation and dissociation of lanthanide complexes [La(III) = Pr, Eu, Tb, Ho, and Yb] with l-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) in toluene-water phase were studied by monitoring the fate of La3+— arsenazo III (AZ) complex (MAZ) in the aqueous phase with the hydrophilic separator. The structures of the ligands and AZ are given below ... 

Natural waters Sample concentration by cation-exchange resin, separation by ion-exchange resin and complexation with Arsenazo III Spectrophotometry (total uranium) 0.1 fjg/L 80% Paunescu 1986... 

Ore leachates Separation as arsenazo III complex Flow injection spectro- photometric 6.6 pg/L No data Perez et al. 1990... 

U Silica gel (U complex) Rocks, underground waters Photometry reaction with Arsenazo III M-Amounts 174)... 

K. Inaba, S. Murahdharan, and H. Freiser, Simultane-ons characterization of extraction eqnilibria and back-extraction kinetics Use of arsenazo III to characterize lanthanide-bis(2,4,4-trimethylpentyl)phosphinic acid complexes in surfactant micelles. Anal. Chem. 65 1510 (1993). 

Ca + Arsenazo III > dyed complex Schematic structure of the slide ... 

Fig. 6-13. Absorption spectra of Arsenazo I and its corresponding calcium complex.

In strongly acid solutions (1-10 M HCl) Arsenazo III reacts only with Th, Zr, Hf and U(rV). The molar absorptivities, e, of the complexes with these metals are about 10. At pH 1-4 Arsenazo III reacts with U(VI), Sc, Fe(ni), Bi, and rare earths. The sensitivity of the colour reactions is lower in this case ( -510 ). The use of Arsenazo III in strongly acid medium overcomes difficulties connected with the hydrolysis of some multivalent metals (c.g., Zr, Th, U). In the determination of these metals the high acidity enhances the selectivity of the reagent. 

The absorbance of free Arsenazo III ( max 520-530 nm) at the absorption maxima of the metal complexes (k 655-665 nm) is very slight. The large difference (AX) between the wavelengths of the absorption maximums of the complexes and the free reagent is important. In the case of Th and U the spectrophotometric method with Arsenazo HI is specific owing to the use of masking agents (oxalic acid, HF) and an appropriate acidity of the medium. 

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