Ferric ion complexes

Under alkaline cleaning conditions, sodium gluconate can be used to similar effect because the gluconate-ferric ion complex is particularly stable. 

Gluconate-ferric ion complex, in cleaning processes 640 Gluconates 123... 

Analytical methods for measuring hydroperoxides in fats and oils can be classified as those determining the total amount of hydroperoxides and those based on chromatographic techniques giving detailed information on the structure and the amount of specific hydroperoxides present in a certain oil sample (8). The PV represents the total hydroperoxide content and is one of the most common quality indicators of fats and oils during production and storage (9, 18). A number of methods have been developed for determination of PV, among which the iodometric titration, ferric ion complex measurement spectrophotometry, and infrared spectroscopy are most frequently used (19). 

Ferric Ion Complexes Other chemical methods based on the oxidation of ferrous ion (Fe ) to ferric ion (Fe ) in an acidic medium and the formation of iron complexes have also been widely accepted. These methods spectrophotometri-cally measure the abihty of lipid hydroperoxides to oxidize ferrous ions to ferric ions, which are complexed by either thiocyanate or xylenol orange (23, 28, 29). Ferric thiocyanate is a red-violet complex that shows strong absorption at 500-510 nm (8). The method of determining PV by coloremetric detection of ferric thiocyanate is simple, reproducible, and more sensitive than the standard iodometric assay, and has been used to measure hpid oxidation in milk products, fats, oils, and liposomes (8, 23). 

Ferric ion complexes (PV) Reduction of ROOH with Fe + and formation of Fe + complexes Absorption at 500-510 nm of the red complex with SCN- Absorption at 560 nm of the blue-purple complex with xylenol orange f=0.1-meq/kg fat 0.5-meq/kg sample Fats, oils and food lipids All samples... 

The evolution of carbon dioxide during polymerization has been used to follow the course of reaction [7—12] other techniques of monomer estimation include sodium methoxide titration [13], spectrophotometry [14] making use of the absorbance of the NCA carbonyls at 1860 or 1790 cm and colorimetry [15] based on the derived hydroxamate—ferric ion complex (514 nm). 

The overall ferric ion complex formation constants of siderophores cannot be determined directly at neutral pH, because the strong iron binding pulls the equilibrium (Eq. 1) to the right, exhibiting (in the case of hydroxamates) no appreciable dissociation into free ligand and free iron above pH 2. 

Cumulative constants of some ferrous and ferric complexes involving the same ligand are compared below in the order of increasing stability of the ferric ion complex. Strong (largely inner-sphere) complexes have been marked with an asterisk. 

Byme. R. H., and Kester, D. R. (1976b). A potentiometric study of ferric ion complexes in synthetic media and seawater. Mar. Chem. 4. 275-287. 

Acetyl and Feruloyl Esters in Pectin. A colorimetric method for determining degrees of acetylation in pectins from various sources ( ), has been shown to be rapid and quite sensitive. Hydroxy-lamine is reactive toward both the methyl and acetyl esters in pectin, and ferric ion complexes with the resulting hydroxamic acids are red. The pectin complex is insoluble and removed by filtration the intensity at 520nm in the soluble fraction, consisting of the ferric complex with acetohydroxamic acid, is a measure of acetyl content. The accuracy of the method was demonstrated in determinations of 0-acetyl levels in standard per-ace-tylated polysaccharides. Another method ( ) involves alkaline hydrolysis of the acetyl groups from pectin, followed by distillation of acetic acid and its titration with standard base. 

Ferric-ion complexes are important in acid-sulfate leaching because ferric ion can be generated from fenous ion using air or oxygen in situ. The reduction of ferric iron to ferrous occurs as the ferric-ion complex diffuses through fluid-filled pores and channels in the rock matrix and encounters reactive metals or sulfides. In most instances, as already discussed, the rate of ferric ion reduction is a diffusion-limited process. The oxidation of ferrous iron to ferric in aqueous solution becomes of primary importance because of its in situ regeneration capacity under appropriate oxidation potentials. 

EDTA was analyzed in drinking water samples as its ferric ion complex on a C,g column (2 — 254 nm) using an aqueous 0.3 M acetate buffer containing 20 mL/L of... 

It has been known for a long time that thiosulfate is present in normal human urine, but reliable methods for the determination of fairly low concentrations have not been available. A method based on the precipitation of the nickel-ethylenediamine complex of thiosulfate followed by iodometric determination was reported many years ago, but gives according to our experience unreliable results. We have earlier described a simple colorimetric method for determination of thiosulfate, based on the cyanolysis of thiosulfate to thiocyanate by the action of cyanide and cupric ions followed by determination of thiocyanate as its ferric ion complex. Unfortunately, this method is not sensitive enough for direct application to urine and, furthermore, other urinary compounds interfere in the cyanolysis reaction. It may, however, be used for assay of the very... 

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