Preconcentration by coprecipitation

Stripping voltammetry procedure has been developed for determination of thallium(I) traces in aqueous medium on a mercury film electrode with application of thallium preconcentration by coprecipitation with manganese (IV) hydroxide. More than 90% of thallium present in water sample is uptaken by a deposit depending on conditions of prepai ation of precipitant. Direct determination of thallium was carried out by stripping voltammetry in AC mode with anodic polarization of potential in 0,06 M ascorbic acid in presence of 5T0 M of mercury(II) on PU-1 polarograph. 

Petit [563] has described a method for the determination of tellurium in seawater at picomolar concentrations. Tellurium (VI) was reduced to tellurium (IV) by boiling in 3 M hydrochloric acid. After preconcentration by coprecipitation with magnesium hydroxide, tellurium was reduced to the hydride by sodium borohydrate at 300 °C for 120 seconds, then 257 °C for 12 seconds. The hydride was then measured by atomic absorption spectroscopy. Recovery was 90 - 95% and the detection limit was 0.5 pmol/1. 

Technetium has been determined in seawater by inductively coupled plasma mass spectrometry after preconcentration by coprecipitation with iron hydroxide [33]. 

A sample treatment device composed of continuous hydride generation, pre-redissolution with thiourea and preconcentration by coprecipitation with La in a knotted reactor was studied... 

The strontium preconcentration by coprecipitation of calcium and strontium phosphates requires magnetic stirrers with heating plate and a centrifuge collecting the precipitate. A drying cabinet is used to gently dry the precipitate of calcium and strontium phosphates. 1220 Quantulus counter is routinely used for the determination of low-level radioactivities. 

No aqueous reference material was available in the laboratory during the validation tests. This test was thus performed on biological reference materials milk powder (IAEA-152) and dried clover (IAEA-156). These samples had to undergo a thermal mineralization at 500 °C. The salts were recovered in 1 M hydrochloric acid. Then alcalino-terrous elements were preconcentrated by coprecipitation in the form of calcium phosphate in basic medium to get rid of some undesirable elements. In order to eliminate a possible presence of Ra an Empore Radium Rad Disk was superposed on the usual Sr Rad Disk. 

Brindle, I.D Brindle, M.E. Le, X.-C. Chen, H. Preconcentration by coprecipitation.Part I. Rapid method for the determination of ultratrace amounts of germanium in natural waters by hydride generation—atomic emission spectrometry. J. Anal. Atomic Spectrom. 1991, 6, 129-132. 

Atsuya I, Itoh K, Ariu K. 1991. Preconcentration by coprecipitation of lead and selenium with nickel-pyrrolidine dithiocarbamate complex and their simultaneous determination by internal standard atomic absorption spectrometry with the solid sampling technique. Pure Appl Chem 63(9) 1221-1226. 

Z.-L. Fang, M. Sperling, B. Welz, Flame atomic-absorption spectrometric determination of lead in biological samples using a flow-injection system with online preconcentration by coprecipitation without filtration, J. Anal. At. Spectrom. 6 (1991) 301. 

Flame Atomic Absorption Spectrometric Determination of Lead and Cadmium in Whole Blood and Urine with On-line Preconcentration by Coprecipitation 232... 

Recently the system has been adapted with minor modifications to on-line preconcentration by coprecipitation for an ETAAS system (Fig. 7.6) [23]. Owing to the discontinuous nature of the operation in ETAAS, the term on-line is used in the sense that... 

The trace level bromide content of natural water samples was preconcentrated by coprecipitation as AgBr with AgCl in the work of Denis and Masschelein [72], The precipitate was oxidized to AgBrOs with NaClO at pH 7. After separation it was determined via DPP in 1 M MgCh solution using 50 mV pulse amplitude and —0.2 to 1.8 V sweep range. A 2 ng/cm detection limit could be achieved with this method. 

Trace metals in sea water are preconcentrated either by coprecipitating with Ee(OH)3 and recovering by dissolving the precipitate or by ion exchange. The concentrations of several trace metals are determined by standard additions using graphite furnace atomic absorption spectrometry. 

The possibility of preconcentration of selenium (IV) by coprecipitation with iron (III) hydroxide and lanthanum (III) hydroxide with subsequent determination by flame atomic absorption spectroscopy has been investigated also. The effect of nature and concentration of collector and interfering ions on precision accuracy and reproducibility of analytical signal A has been studied. Application of FefOH) as copreconcentrant leads to small relative error (less than 5%). S, is 0.1-0.2 for 5-100 p.g Se in the sample. Concentration factor is 6. The effect of concentration of hydrochloric acid on precision and accuracy of AAS determination of Se has been studied. The best results were obtained with HCl (1 1). 

The concentration of nickel in natural waters is so low that one or two enrichment steps are necessary before instrumental analysis. The most common method is graphite furnace atomic absorption after preconcentration by solvent extraction [122] or coprecipitation [518]. Even though this technique has been used successfully for the nickel analyses of seawater [519,520] it is vulnerable to contamination as a consequence of the several manipulation steps and of the many reagents used during preconcentration. 

Many metals in seawater can be preconcentrated for analysis by coprecipitation with Ga(OH)3. A 200-p.L HC1 solution containing 50p,g of Ga3+ is added to 10.00 mL of the seawater. When the pH is brought to 9.1 with NaOH, a jellylike precipitate forms. After centrifugation to pack the precipitate, the water is removed and the gel is washed with water. Then the gel is dissolved in 50 p,L of 1 M HN03 and aspirated into an inductively coupled plasma for atomic emission analysis. The preconcentration factor is 10 mL/50 p,L = 200. The figure shows elemental concentrations in seawater as a function of depth near hydrothermal vents. 

Rao RR and Chatt A (1993) Preconcentration neutron activation analysis of trace elements in seawater by coprecipitation with l-(2-thiazolylazo)-2-naph-thol, pyrrolidenedithiocarbamate and N-nitroso-... 

Shazali 1, Van t Dack L, Gijbels R (1987) Determination of precious metals in ores and rocks by thermal neutron activation/y-spectrometry after preconcentration by nickel sulfide fire assay and coprecipitation with tellurium. Anal Chim Acta 196 49-58 Stembeck J, Sjodin A, Andreasson K (2002) Metal emissions from road traffic and the influence of resuspension—results from two tunnel studies. Atmos Env 36 4735-4744 Sun Y, Guan X, Du A (1998) Determination of platinum group elements by inductively coupled plasma-mass spectrometry combined with nickel sulfide fire assay and tellurium coprecipitation. Spectrochim Acta B 53 1463-1467... 

S. Saracoglu, M. Soylak, and L. Eld. Separation/preconcentration of trace heavy metals in urine, sediment and dialysis concentrates by coprecipitation with samarium hydroxide for atomic absorption spectrometry. Talanta 59 287-293, 2003. 

Owing to inadequate detection limits by direct analysis, various workers examined preconcentration procedures, including dithiocarbamate preconcentration [447,732-734], ion exchange preconcentration [735-737], chelation solvent extraction [736], coprecipitation [738], and preconcentration in silica-immobilised 8-hydroxyquinoline [129]. 

Hiraide et al. [737] developed a multielement preconcentration technique for chromium (III), manganese (II), cobalt, nickel, copper (II), cadmium, and lead in artificial seawater using coprecipitation and flotation with indium hydroxide followed by ICP-AES. The metals are simultaneously coprecipitated with indium hydroxide adjusted to pH 9.5, with sodium hydroxide, ethano-lic solutions of sodium oleate and dodecyl sulfate added, and then floated to... 

Ahern et al. [386] has observed that organophosphorous compounds are coprecipitated with cobalt and pyrrolidine dithiocarbonate, and suggest that this might be a suitable means of preconcentrating the phosphorus fraction of harbour water prior to analysis by X-ray fluorescence spectrometry. 

If necessary a preconcentration was carried out on this solution to lower the detection limits of the method. Preconcentration was achieved by a method involving co-precipitation of the antimony with hydrous zirconium oxide in which the digest is stirred with 150mg zirconyl chloride and the pH adjusted to 5 with ammonia to coprecipitate antimony and hydrous zirconium oxide. The isolated precipitate is dissolved is 7M hydrochloric acid and 30% sulphuric acid. Antimony is then converted to the pentavalent state by successive treatment with titanium III chloride and sodium nitrite and excess nitrite destroyed by urea. 

The detection limits obtained by flame and graphite furnace AAS and the concentration levels of the elements in seawater are summarized in Table 2. In general, graphite furnace AAS provides better sensitivities for many elements than the flame technique. Even so, AAS sensitivity is insufficient for the direct determination of most ultra-trace elements. Furthermore, concentrated salts and undissolved particulates cause severe interferences with the determination of trace elements by AAS. Therefore, it is necessary to concentrate the analytes before the determination, and, if possible, to separate the analytes from dissolved major constituents and particulates. Solvent extraction, coprecipitation and ion-exchange techniques are the most widely used techniques for the preconcentration of seawater. In the following sections, these techniques will be reviewed. It should be noted here that the efficiencies of the recovery of the analytes as well as the contamination from reagents and solvents must be carefully examined when the preconcentration techniques are applied. Chakrabarti et al. [10] have summarized the work on the application of preconcentration techniques to marine analysis by AAS. Hence, only some representative applications will be introduced hereafter. 

The membranes are designed to retain strontium specifically. The disk can retain 3 mg strontium without significant loss (against 8 mg for the Eichrom s 2 mL Sr-spec columns). Some information provided by the manufacturer and other users indicate possible interferences. Presence of cations such as Na", K", NH/ and Ca " can interfere with strontium fixing. If necessary, a preconcentration with the Ca-phosphate coprecipitation technique can be performed to eliminate some interfering elements. 

FI. Wu, Y. Jin, Y.-Q. Shi, S.-P. Bi, On-line organoselenium interference removal for inorganic selenium species by flow injection coprecipitation preconcentration coupled with hydride generation atomic fluorescence spectrometry, Talanta 71 (2007) 1762. 

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