Antimony spectrophotometric determination

Methylfluorone is recommended for the spectrophotometric determination of antimony [5,57,58]. In a weakly acidic medium (pH 2), the orange Sb(III)-methylfluorone complex [which exists as a stable sol in the presence of gelatine or poly(vinyl alcohol)], is formed (e = 4.0-10 at 530 nm). Dibromophenylfluorone allows one to determine Sb in the presence of Bi [59]. Sb was determined with the use of vanillylfluorone in the presence of poly(vinyl alcohol) [60]. 

Unsaturated and hydroxylated triterpenes and steroids give colored products with aromatic aldehydes in strong mineral acids, with acetic anhydride in sulfuric acid, and with inorganic salts (cerium(IV) sulfate and antimony(III) chloride, for example) in an acidic solution. These reactions have been used as the basis for determination of saponins. The analysis of Ginseng radix (Panax ginseng, Araliaceae) in Pharmacopoeia Helvetica VII, for example, relies on reaction with glacial acetic acid/sulfuric acid and spectrophotometric determination at 520 nm of the red product. The jS-aescine component of horse chestnut (Aesculus hippocastanum, Hippocastan-aceae) saponin can be determined spectrophoto-metrically after treatment with a mixture of iron(III) chloride, acetic acid, and sulfuric acid. 

Direct UV-visible spectrophotometric determination of vitamin D is limited to pure dosage forms that should not even contain other fat-soluble vitamins. In an older colorimetric AOAC procedure the absorbance of a colored product resulting from the reaction of vitamin D with antimony trichloride was measured at 500 nm. However, the other fat-soluble vitamins, particularly vitamin A, as well as the... 

Another example is a fully computerized MSFIA system for the spectrophotometric determination of available phosphorus in soil extracts. The molybdenum blue method is chosen for the colorimetric determination, using ascorbic acid as reducing agent, antimony to accelerate the reduction to the blue complex and applying the Egner-Riehm method to extract phosphorus from soil samples. It presents a hnear calibration curve between 0.75 and 15 mg/1. A determination frequency of 15/h may be achieved, with good repeatability for 12 consecutive injections of soil extracts (RSD <1.7%). Results obtained from 12 soil samples were statistically comparable to those attained by the usual batch method [102]. 

Silver diethyldithiocarbamate [1470-61-7] is a reagent commonly used for the spectrophotometric measurement of arsenic in aqueous samples (51) and for the analysis of antimony (52). Silver iodate is used in the determination of chloride in biological samples such as blood (53). 

Spectrophotometric methods based on an enhancement of the blue color produced on reduction of 12-molybdophosphate (arsenate) in the presence of antimony(III) are widely used for the determination of phosphoms(V) or arsenic(V). However, nature of heteropoly blue, their spectra, mechanism of the reaction are obscure. In addition, mixed POMs were shown as very efficient analytical forms for the determination of P(V) and As(V). 

Discussion. In acid solution arsenic(III) can be oxidised to arsenic(V) and antimony(III) to antimony(V) by the well-established titration with a solution of potassium bromate and potassium bromide (Section 10.133). The end point for such determinations is usually observed indirectly, and very good results have been obtained by the spectrophotometric method of Sweetser and Bricker.23 No change in absorbance at 326 nm is obtained until all the arsenic)III) has been oxidised, the absorbance then decreases to a minimum at the antimony(III) end point at which it rises again as excess titrant is added. 

After adjusting to 2 mol 1 1 in hydrochloric acid, 500 ml of the sample is adsorbed on a column of Dowex 1-XS resin (Cl form) and elution is then effected with 2 M nitric acid. The solution is evaporated to dryness after adding 1M hydrochloric acid, and the tin is again adsorbed on the same column. Tin is eluted with 2 M nitric acid, and determined in the eluate by the spectrophotometric catechol violet method. There is no interference from 0.1 mg of aluminium, manganese, nickel, copper, zinc, arsenic, cadmium, bismuth, or uranium any titanium, zirconium, or antimony are removed by ion exchange. Filtration of the sample through a Millipore filter does not affect the results, which are in agreement with those obtained by neutron activation analysis. 

Antimony is then determined by a spectrophotometric method utilizing crystal violet in which the extract is treated with this chromogenic agent and... 

Haring et al. [31] determined arsenic and antimony by a combination of hydride generation and atomic absorption spectrometry. These workers found that, compared to the spectrophotometric technique, the atomic absorption spectrophotometric technique with a heated quartz cell suffered from interferences by other hydride-forming elements. 

Colorimetric methods Silicon is determined by the molybdenum blue spectrophotometric method after solubilization in H2O, in alkaline solutions or in concentrated HF. A flow analysis procedure for the measurement of soluble silicon with respect to the total Si concentration is used. The proposed method is applied to samples of rain water and of aerosols on filters [45]. Simultaneous determination of orthophosphate and silicate in brackish water is performed by the same technique. Molybdate/ antimony, ascorbic acid, and oxalic acid reagents are added to the samples and spectra are recorded in the wavelength range 410-820 nm after a total reaction time of 30 min [46]. 

Spectrophotometric methods for antimony speciation in waters using cationic dyes were reviewed [2]. Possible methods for preconcentration were suggested. N,N -diphenylbenzamidine and Brilliant Green in an aeidic non-ionic micellar media were used in chemical speciation and determination of Sb in fresh ground water and waste water [3]. 

Gas-phase spectrophotometric method was proposed for the determination of arsenic in tap water after the conversion into hydride, its collection in a trap cooled by liquid N2 and subsequent evaporation at 80°C in a flow of N2. The recovery of 73-86.7% As was reported. Simultaneous determination of arsenic, antimony, selenium and tin was accomplished. 

A spectrophotometric procedure has been described184 based on the formation of a coloured complex with antimony pentachloride in carbon tetrachloride, for the determination of 0.01-1.0% biphenyl in phenyltrichlorosilane. These workers also described a spectrophotometric method for the determination of 0.01-10% biphenyl in phenyltrichlorosilane based on measurement of the difference in extinction of solutions of the sample and a standard in chloroform-ethanol at 251 nm. The determination of biphenyl in phenyltrichlorosilane and its hydrolysis products have also been discussed185 The extinctions of pure phenyl trichlorosilane and the sample are measured at 251 nm in chloroform ethanol 1 1 the difference is related to the content of biphenyl, which absorbs 60 times more strongly than phenyltrichlorosilane at that wavelength 0.05-10% of biphenyl may be determined. 

An important consideration in the determination of antimony in aqueous matrices is the fact that antimony can be present in the (III), (IV), or (V) valence state. To avoid analytical problems, it is desirable that the antimony be present in a specific valence state. This is particularly important if a spectrophotometric method is to be used because the reagents employed usually react only with a particular oxidation state. Maren observed in a study of the use of rhodamine B that Sb(IV) could not be easily oxidized to the required Sb(V) (3). In work on the determination of antimony using 3,4,7-trihydroxyflavone, a reagent which reacts only with Sb(III), Fider demonstrated that Sb(IV) and Sb(V) could be reduced to Sb(III) by hydroxylamine sulfate (13). 

The complex is extracted with CCl /chlorobenzene (1 4) and determined spectrophotometrically at 365 nm (8 555 = 70 000). Due to the low antimony content in natural waters it is necessary to concentrate the element by coprecipitation with manganese dioxide hydrate. The addition of ethanol to the KMnOz solution improves the adsorption characteristics of the carrier. 

Gravimetric methods for the determination of Sb(III) as trisulphide or as 8620 are not very specific. A quick volumetric method for Sb(III) is based on its oxidation by iodine, using starch as indicator. On the other hand, Sb(V) oxidises iodide to iodine which can be titrated against thiosulphate. Antimony as well as arsenic and bismuth can be determined by atomic absorption spectroscopy, the suitable wavelengths and concentration ranges and other conditions are usually supplied by the manufacturer. A useful spectrophotometric method is based on the yellow complex tetraiodobismuthate(III). 

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