Alkaline peroxide method, determining

The peroxide method for determining U is of rather low sensitivity [140]. A yellow peruranate is formed in the reaction of H2O2 with U(VI) in alkaline media. Hydrogen peroxide can be added to the carbonate complex of U, or an acidic solution containing U and H2O2 is made alkaline with NaOH. The absorbance is measured at 370-400 nm. 

Com stover used for this study was harvested in 2003 at the Kramer Farm in Wray, Colorado. The stover was pretreated either in-house at the National Renewable Energy Laboratory or received via subcontract fiom the CAFI [12] pretreatment group members. The samples selected for this study were pietreated by alkaline peroxide (NREL), sulfite steam explosion (UBC), ammonia fiber explosion (MSU), and dilute sulfuric acid (NREL) methods. The composition of the pretreated stover was determined by a two-stage sulfuric acid hydrolysis treatment according to the NREL Laboratory Analytical Procedure titled Determination of Stmctural Carbohydrates and Lignin in Biomass [13]. The pretreatment conditions and compositional information for each substrate are listed in Table 2. 

Latner (1948) described in a preliminary communication the application of the diazo reaction after the treatment of ultrafiltrates of blood or plasma with strong alkali. Touster (1951) made use of the reaction of ergothioneine with bromine water to form inorganic sulfate, which was determined colorimetrically. Quantitative recoveries were not obtained. Ohara et al. (1952) determined the amount of sulfate produced from blood and tissues by oxidation with alkaline peroxide. Jocelyn (1958) has determined free and bound ergothioneine in blood and proteins by a method based on the estimation of trimethylamine released by heating the material with strong alkali. The validity of results obtained with these methods cannot be assessed at this time since the absence of interfering substances has not, in the reviewer s opinion, been adequately demonstrated. 

The hydrogen evolved in the alkaline peroxide oxidation of formaldehyde has been used as a basis for a gas volumetric method of formaldehyde determination by Frankforter and West. ... 

Potassium Cyanide Method. Romijn also devised this method of formaldehyde determination which is considered by Mutschin to be as. accurate as the sodium sulfite, alkaline peroxide, and iodimetric methods for pure solutions of formaldehyde, and superior to them in the presence of acetoner acetaldehyde, benzaldehvde, higher aldehydes, and ketones. The procedure is based on the quantitative formation of cyanohi drin when formaldeh de is treated vith a solution containing a -known excess of potassium cyanide. 

Peroxidic Compounds. When hydrogen peroxide is added to a solution of titanium(IV) compounds, an intense, stable, yellow solution is obtained, which forms the basis of a sensitive method for determining small amounts of titanium. The color probably results from the peroxo complex [Ti(02)(0H)(H20)J, and crystalline salts such as K2[Ti(02)(S0 2] H20 can be isolated from alkaline solutions. The peroxo ligand is bidentate the two oxygen atoms ate equidistant from the titanium (98). 

A multiwavelength approach might have been considered as an alternative to chemical derivatisation. Ruddle and Wilson [62] reported UV characterisation of PE extracts of three antioxidants (Topanol OC, Ionox 330 and Binox M), all with identical UV spectra and 7max = 277 nm, after reaction with nickel peroxide in alkaline ethanolic solutions, to induce marked differentiation in different solvents and allow positive identification. Nonionic surfactants of the type R0(CH2CH20) H were determined by UV spectrophotometry after derivatisation with tetrabromophenolphthalein ethyl ester potassium salt [34]. Magill and Becker [63] have described a rapid and sensitive spectrophotometric method to quantitate the peroxides present in the surfactants sorbitan monooleate and monostearate. The method, which relies on the peroxide conversion of iodide to iodine, works also for Polysorbate 60 and other surfactants and is more accurate than a titrimetric assay. 

Sakamoto [243] determined picomolar levels of cobalt in seawater by flow injection analysis with chemiluminescence detection. In this method flow injection analysis was used to automate the determination of cobalt in seawater by the cobalt-enhanced chemiluminescence oxidation of gallic acid in alkaline hydrogen peroxide. A preconcentration/separation step in the flow injection analysis manifold with an in-line column of immobilised 8-hydroxyquinoline was included to separate the cobalt from alkaline-earth ions. One sample analysis takes 8 min, including the 4-min sample load period. The detection limit is approximately 8 pM. The average standard deviation of replicate analyses at sea of 80 samples was 5%. The method was tested and inter calibrated on samples collected off the California coast. 

HTAB has been used, on the one hand, to increase the CL intensity of the reaction of 2,6,7-trihydroxy-9-(4 chlorophenyl)-3-fluorene with hydrogen peroxide in alkaline solution, in the presence of traces of Co(II) as a catalyst [43]. As a consequence, a CL method has been established for determination of ultratraces of Co(II). On the other hand, HTAB micelles sensitize the CL oxidation of pyro-gallol with A-bromosuccimide in an alkaline medium [44], while anionic and nonionic surfactants inhibit the CL intensity of this reaction (Table 3). This sensitized process allows the determination of pyrogallol by flow injection in an interval of 5 X 10 7-3 X 10 5 M. 

Other cationic surfactants such as TTAB, DTAB, DODAB, STAC, CEDAB, and DDDAB have been used in CL reactions with less frequency. Thus, tetradecyltrimethylammonium bromide [TTAB] has been used to increase the sensitivity of the method to determine Fe(II) and total Fe based on the catalytic action of Fe(II) in the oxidation of luminol with hydrogen peroxide in an alkaline medium [47], While other surfactants such as HTAB, hexadecylpiridinium bromide (HPB), Brij-35, and SDS do not enhance the CL intensity, TTAB shows a maximum enhancement at a concentration of 2.7 X 10 2 M (Fig. 11). At the same time it was found that the catalytic effect of Fe(II) is extremely efficient in the presence of citric acid. With regard to the mechanism of the reaction, it is thought that Fe(II) forms an anionic complex with citric acid, being later concentrated on the surface of the TTAB cationic micelle. The complex reacts with the hydrogen peroxide to form hydroxy radical or superoxide ion on the... 

Cyanophenanthridine forms the corresponding amide on treatment either with 90% sulfuric acid, or hydrogen peroxide in alkaline solution.296 Complete hydrolysis, followed by decarboxylation to the parent phenanthridine, provides a ready method of structure determination.80... 

The semiquantitative and quantitative methods discussed in this section are based on the optical properties of melanins in both the transmission and reflection mode, and they may require solubilization and/or partial degradation of the samples (305). The melanin content in tissues has been determined visually (306) following treatment with Fe and potassium ferricyanide (307) and by reflectance (308) and remittance (143) methods. For fluorimetric determination of melanins (melanoma cells), the sample is solubilized with alkaline hydrogen peroxide (pH 7.8, 100°C, 30 min) the excitation wavelength is 410 nm, emission 500 nm (148). Fairly good chemical stability of melanins has been determined in gravimetric determinations after separation from all other constituents of melanosomes with acid digestion (6 N HCl, 100°C, 72 hr) (110). 

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