Cation Interferences

Mutual interferences of cations have been observed in many cases. Aluminum interferes with calcium and magnesium, as does silicon. Other examples include calcium and gallium, calcium and indium, and the interferences of beryllium, chromium, iron, molybdenum, silicon, titanium, tungsten, and the rare earth elements. These interferences are neither spectral nor ionic in nature and the mechanisms of their interactions are unknown. Cation-cation interferences, however, invariably decrease the signal intensity of the analyte element. 

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I have carried out widespread studies on the application of a sensitive and selective preconcentration method for the determination of trace a mounts of nickel by atomic absorption spectrometry. The method is based on soi ption of Cu(II) ions on natural Analcime Zeolit column modified with a new Schiff base 5-((4-hexaoxyphenylazo)-N-(n-hexyl-aminophenyl)) Salicylaldimine and then eluted with O.IM EDTA and determination by EAAS. Various parameters such as the effect of pH, flow rate, type and minimum amount of stripping and the effects of various cationic interferences on the recovery of ions were studied in the present work. 

The effects of vaiious cationic interferences on percent recovery of Cobalt were studied. The method was successfully applied for the determinations of Cobalt ion from synthetic and water samples. 

The combined effect of cation interference for both Mg11 and Ca11 is almost identical with the solid curve in Fig. 5.7, indicating that the magnesium ion interference is the dominant one. 

An analytical procedure that quantifies the total AE concentration resolved by alkyl chain length for various environmental matrices (influent, effluent, and river water) was developed by Di Corcia et al. [41]. The method utilises a reverse-phase column to extract and concentrate AE from surface waters and wastewaters and utilises strong anionic and cationic exchange columns to remove potential interferences. Samples are passed through the RP extraction column (Ci). AE and potential anionic and cationic interferences are eluted from the Ci column and passed directly through the SAX and SCX. The SAX and SCX columns retain anionic and cationic materials while non-ionic AE are not retained. Recovery of AE from influent, treatment plant effluent, and river water is quantitative (65—102%) over a range of concentrations for all matrices. 

The atomic absorption characteristics of technetium have been investigated with a technetium hollow-cathode lamp as a spectral line source. The sensitivity for technetium in aqueous solution is 3.0 /ig/ml in a fuel-rich acetylene-air flame for the unresolved 2614.23-2615.87 A doublet under the optimum operating conditions. Only calcium, strontium, and barium cause severe technetium absorption suppression. Cationic interferences are eliminated by adding aluminum to the test solutions. The atomic absorption spectroscopy can be applied to the determination of technetium in uranium and its alloys and also successfully to the analysis of multicomponent samples. 

Microgram amounts of pertechnetate can be determined by measuring the extinction of its colored complex with toluene-3,4-dithiol in 2.5 N hydrochloric acid after extraction into carbon tetrachloride . One hour must be allowed for the development of the color. The molar extinction coefficient at 450 nm is 15,000. Beer s law is followed over the range of 1.5 to 16.5 fig Tc per ml. The overall error does not exceed a standard deviation of 5%. Because many cations interfere, an initial separation of technetiiun is necessary. 

Accdg to Ref ll,p 608, this analysis is not applicable to chlorates of Co, Au, Cr, Mn and probably Hg. This is because they offer possibility of cationic interference in the reduction step. This interference can be overcome by reducing chlorate to chloride by ignition with Na2C03 or NH4C1 followed by detn of resulting chloride by pptn with AgNOg A volumetric method for simultaneous... 

Transition metal cations interfere by forming stable complexes. Chloride and bromide also interfere. Interference from sulfide is removed by the addition of 10 M NaOH ISA. ... 

F6. Foster, W. H., and Hume, D. N., Mutual cation interference effects in flame photometry. Anal. Chem. 31, 2033-2036 (1959). 

An attractive approach to the removal of interferents involves the use of the chelating ion-exchange resin Chelex 100. With the exception of iron(Il) and iron(III), all identified cationic interferents can be overcome by passing the sample solution (at pH 4.0) through a column of this resin. The ubiquitous nature of iron, however, precludes the application of this procedure in most practical circumstances. 

The explanation is the same a solvent of low polarity favours ion pairing. Thus, in solvents of high polarity, the base forms a cyclic transition state with the substrate directly, without the involvement of its corresponding cation, i.e. the transition state is now a five- and not a six-membered ring, and so the base is now in an optimal position to remove the syn-hydrogen. Conversely, in solvents of low polarity with large amounts of ion pairing, the presence of the cation interferes with the abstraction of the proton and so anti-elimination once more predominates. 

The voltammetric determination of nitrate following a preconcentration step using Permion 1025 was developed by Cox, Lundquist and Washinger (33). Nitrate is exchanged from the sample solution through the membrane into a small volume cell contain ing 0.1 M potassium chloride and 0.01 M lanthanum chloride. The method eliminates cationic interferences with the voltammetry but does not successfully deal with anionic interferences such as a sulfate or nitrite. 

The pH of the silicate solutions with R — 2.0 and R = 1.5 are given in Table 1. The listed values are corrected for cation interference. Accurate pH determinations for Li silicate solutions and silicate solutions for which R = 0.4 could not be made because the error due to cation interference was on the order of 2 pH units. 

This is a most elegant and attractive method, which is likely to be used increasingly in flame photometric analysis. As will be discussed later, interference effects are not inherently absent with this method anionic interference is equally or more troublesome with this method than with emission ffame work, while cationic interference is less prominent, not because of the inherent nature of the method, but because of the lower flame temperatures usually used with this method. Its attraction is that it has some claims to be an absolute method in certain cir-... 

Cation interferences are readily removed with a strong cation exchange resin in the hydrogen form ... 

Tesfalidet et al.[32] reponed on a novel application of an on-line anion-exchanger packed bed. loaded with borohydride reductant for hydride generation AAS. The packed reactor provided the multi-function of separating cation.interferents, analyte preconcentration, and reaction environment. 

Besides ferric ammonium sulfate, permanganate solutions can be used to titrate the reduced titanium. Although many cations interfere with the permanganate titration, this reagent is still useful in the assay of highly purified titanium dioxide materials. Potassium dichromate can be used to titrate Ti(III) solutions (with the aid of 0.2% indigo as the indicator), and Ce(lV) reagents can also be used as titrants. 

The high affinity of Pd-chloro-complexes to strong anion exchange materials enables the use of various anion exchange sorbents for preconcentration of Pd with simultaneous elimination of cationic interferents. Especially styrene or acrylic polymers cross-linked with divinylbenezene can be applied for enrichment of PGE from large sample volumes (Matsubara et al. 2000 Kovacheva and Djingova 2002 Lesniewska et al. 2006). 

For cations, interferences are easily determined again in view of solubility products ... 

Cation interference has been observed as well. For example, aluminum causes low results in the determination of magnesium, apparently as a result of the formation of a heat-stable aluminum-magnesium compound (perhaps an oxide). 

Ions of potassium, lead, magnesium, ammonium, and lithium do not interfere in the detection of Na- - when present in amounts not exceeding the concentration of Na+ by 4, 7, 15, 3 and 4 times respectively. Other cations interfere. 

Jenke and Pagenkopf [20] reported on the occurrence of cationic interferences during the anion analysis of aqueous samples using nonsup-... 

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