Analytical EDTA technique

Anions of weak acids can be problematic for detection in suppressed IEC because weak ionization results in low conductivity and poor sensitivity. Converting such acids back to the sodium salt form may overcome this limitation. Caliamanis et al. have described the use of a second micromembrane suppressor to do this, and have applied the approach to the boric acid/sodium borate system, using sodium salt solutions of EDTA.88 Varying the pH and EDTA concentration allowed optimal detection. Another approach for analysis of weak acids is indirect suppressed conductivity IEC, which chemically separates high- and low-conductance analytes. This technique has potential for detection of weak mono- and dianions as well as amino acids.89 As an alternative to conductivity detection, ultraviolet and fluorescence derivatization reagents have been explored 90 this approach offers a means of enhancing sensitivity (typically into the low femtomoles range) as well as selectivity. 

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. 

Methods based on the inhibitory effect of the analyte and the use of an enzyme thermistor have primarily been applied to environmental samples and typically involve measuring the inhibitory effect of a pollutant on an enzyme or on the metabolism of appropriate cells [162]. The inhibiting effect of urease was used to develop methods for the determination of heavy metals such as Hg(II), Cu(II) and Ag(I) by use of the enzyme immobilized on CPG. For this purpose, the response obtained for a 0.5-mL standard pulse of urea in phosphate buffer at a flow-rate of 1 mL/min was recorded, after which 0.5 mL of sample was injected. A new 0.5-mL pulse of urea was injected 30 s after the sample pulse (accurate timing was essential) and the response compared with that of the non-inhibited peak. After a sample was run, the initial response could be restored by washing the column with 0.1-0.3 M Nal plus 50 mM EDTA for 3 min. Under these conditions, 50% inhibition (half the initial response) was obtained for a 0.5-mL pulse of 0.04-0.05 mM Hg(II) or Ag(I), or 0.3 mM Cu(II). In some cases, the enzyme was inhibited irreversibly. In this situation, a reversible enzyme immobilization technique... 

An alternative technique for preventing the analyte forming refractory compounds in the flame is to add a compound to the sample which forms a preferential complex with the analyte. Ethylenediaminetetraacetic acid (EDTA) is often used since it complexes with the cation thus preventing its association with an anion that can lead to the formation of a refractory compound. 

Cd + can be detected by the insolubility of its yeUow sulfide (see Analytical Chemistry of the Transition Elements). Several reaction and spot tests allow the identification of Cd +. Quantitative determinations are based on gravimetric (CdS or /3-naphthylquinoltne complex) or titrimetric (EDTA) methods. Several physical techniques can be used in quantitative and qualitative analysis polarography (or related techniques, even in the presence of Zn, Cu, Bi and Pb), electrodeposition, colorimetric methods, flamephotometric methods, neutron activation, atomic absorption, and ICP spectrometry and ion selective electrodes. 

The most commonly applied methods for the analysis of polyamines in erythrocytes make use of amino acid analyzers and HPLC techniques. A capillary gas chromatographic method with nitrogen-phosphorous detection was applied to the simultaneous determination of 1,3-diaminopropane, putrescine, cadaverine (Cad), spermidine (Sd), and spermine (Sp) in human erythrocytes. Blood samples, collected by venipuncture into EDTA containing Venoject tubes, were subjected to the removal of plasma by centrifugation and erythrocytes were washed three times with two volumes of 0.9% NaCl. The stability of polyamines in erythrocyte suspensions was also investigated. Quantification of polyamines was done by comparing the peak-area ratio of each analyte and its internal standard with that of the standard. The polyamine samples were eluted with 0.1 M hydrochloric acid solutions. The eluate was evaporated to dryness at 120°C under a stream of air and 200 each of acetonitrile and heptafluorobutyric anhydride were added. The isolation of derivatives... 

Initial application of ion exchange to modern LC depends on the analyte having a specific property such as ultraviolet absorbance, fluorescence or radioactivity. As many ion exchange methods require the presence of com-plexing agents (EDTA, citrate) and various electrolyte additions to achieve the required resolution, conductivity detectors could not be used without modification of the technique, since this parameter is a universal property of ionic species in solution. 

Fluoride can be determined by means of an iron(iii) thiocyanato complex extracted into isobutylketone. Iron is extracted back into the aqueous phase with the fluoride sample solution. The atomic absorption signal of iron is directly proportional to the concentration of fluoride (0.5-6 ju,g F ml ). EDTA can be determined by a similar technique. Copper is first extracted as the hydroxyquinolinato complex into isobutylketone, and then extracted back into the aqueous solution with the EDTA sample solution. In these methods the analyte anion must form a more stable complex compound with the metal ion than the ligand used for the first solvent extraction. These kind of... 

Chau et al pointed out that as the authenticity of the compounds to be analyzed must be preserved, any of the digestion methods with acids or alkalis are not suitable, and that extraction seemed to be the method of choice for removing these compounds from samples. For this traction, they adopted benzene as recommended by Sirota and Uthe for the quantitative extraction of tetramethyllead and tetraethyllead from fish homogenates suspended in aqueous EDTA solution. Although ionic forms of lead such as Pb(II), diethyllead dichloride, and trimethyllead acetate do not extract in the benzene phase, any lead compounds that distribute into the benzene phase as tetraalkyllead will be determined. Chau et al421 found that environmental samples can contain other forms of organolead compounds that are extractable into benzene but which are not volatile enough to be analyzed by the GC-AAS technique, hence the need for a speciation specific analytical system. 

Several reports summarized and reviewed the EPRI/SGOG development effort. Jevec reviewed the work on developing the iron sludge solvent, including the tests to determine if citric acid was a desirable additive, proper concentration of hydrazine, and optimum pH. Three types of copper solvents were reviewed EDTA/sodium nitrite ammonia/air and EDTA/peroxide/EDA. The development of analytical and monitoring techniques was addressed. 

Each variation was repeated four times in plots of 25 m of which 15.25 m were used in order to avoid edge effects. The plots were randomized as is accepted procedure in such tests. Soil samples were taken from each plot in the Ap horizon by the so-called compound sample technique. From each plot samples of vegetable parts were taken such as stalks, leaves, seeds, fruit tubers in quite representative quantities. The preparation of the soil was performed in such a way as to get fine soil as required by the various analytical methods used in the determination of the relevant physical and chemical parameters and in accordance with the pertinent official methods [3]. The exchangeable cations were determined according to a method proposed by Casalicchio and others. More specifically the soluble nickel was extracted from the soil with distilled water at a ratio of 1 5 with a shaker for 60 minutes, and in ammonium acetate solution and EDTA at a ratio of 1 10, shaking time 60 minutes. 

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