Chloride spectrophotometric determination

Quantitative. Classically, silver concentration ia solution has been determined by titration with a standard solution of thiocyanate. Ferric ion is the iadicator. The deep red ferric thiocyanate color appears only when the silver is completely titrated. GravimetricaHy, silver is determined by precipitation with chloride, sulfide, or 1,2,3-benzotriazole. Silver can be precipitated as the metal by electro deposition or chemical reduciag agents. A colored silver diethjldithiocarbamate complex, extractable by organic solvents, is used for the spectrophotometric determination of silver complexes. 

Bromide ndIodide. The spectrophotometric determination of trace bromide concentration is based on the bromide catalysis of iodine oxidation to iodate by permanganate in acidic solution. Iodide can also be measured spectrophotometricaHy by selective oxidation to iodine by potassium peroxymonosulfate (KHSO ). The iodine reacts with colorless leucocrystal violet to produce the highly colored leucocrystal violet dye. Greater than 200 mg/L of chloride interferes with the color development. Trace concentrations of iodide are determined by its abiUty to cataly2e ceric ion reduction by arsenous acid. The reduction reaction is stopped at a specific time by the addition of ferrous ammonium sulfate. The ferrous ion is oxidi2ed to ferric ion, which then reacts with thiocyanate to produce a deep red complex. 

SPECTROPHOTOMETRIC DETERMINATION OF HYDROXYUREA AS A COMPLEX WITH FERRIC CHLORIDE AFTER STABILIZATION BY FERROUS IONS... 

Various chromogenic reagents have been used for the spectrophotometric determination of boron in seawater. These include curcumin [108,109], nile blue [110], and more recently 3,5 di-tert butylcatechol and ethyl violet [111]. Uppstroem [108] added anhydrous acetic acid (1 ml) and propionic anhydride (3 ml) to the aqueous sample (0.5 ml) containing up to 5 mg of boron per litre as H3BO3 in a polyethylene beaker. After mixing and the dropwise addition of oxalyl chloride (0.25 ml) to catalyse the removal of water, the mixture is set aside for 15-30 minutes and cooled to room temperature. Subsequently, concentrated sulfuric-anhydrous acetic acid (1 1) (3 ml) and curcumin reagent (125 mg curcumin in 100 ml anhydrous acetic acid) (3 ml) are added, and the mixed solution is set aside for at least 30 minutes. Finally 20 ml standard buffer solution (90 ml of 96% ethanol, 180 g ammonium acetate - to destroy excess of protonated curcumin - and 135 ml anhydrous acetic acid diluted to 1 litre... 

Tsunogai [7] carried out a similar coprecipitation allowing a 20-hour standing period to ensure that iodide is fully recovered in the silver chloride coprecipitate. Again, the iodide is oxidised to iodate prior to spectrophotometric determination of the latter. This procedure also includes a step designed to prevent interference by bromine compounds. 

An alternative to qdt, (.S )-2-(3-mercaptoquinoxalinyl)thiourinium, is stable and soluble in aqueous ethanol solutions unlike qdt (27). At pH 10 in ammonia-ammonium chloride buffer, this reagent hydrolyzes to qdt. (5)-2-(3-Mercapto-quinoxalinyl)thiourinium has been used for the simultaneous detection of nickel and cobalt and the determination of palladium (27, 28). A related reagent, 6-nitro-(S)-2-(3-mercaptoquinoxalinyl)thiourinium has also been used in metal analysis (7). This reagent is hydrolyzed in ammonia buffer to generate 6-nitro-2,3-quinoxalinedithiol (nqdt). Following adjustment to pH 2.0, the mixture is extracted with methyl isobutyl ketone and spectrophotometrically analyzed. 6-Nitro-(5)-2-(3-mercaptoquinoxalinyl)thiourinium has been used for the simultaneous spectrophotometric determination of nickel and cobalt by the quantification of [Ni(nqdt)2]2 (710 nm, e = 20,700 L mol 1cm 1) and [Co(nqdt)2]2 (530 nm, e = 40,000 L moE cm-1), respectively. 

Uesugi K, Nagahiro T. 1983. A highly sensitive spectrophotometric determination of uranium with chromal blue G in the presence of cetytrimethylammonium chloride. Analytica Chimica Acta 148 315-320. 

Spectrophotometric determination of the chain end groups produced by termination with dinitrobenzoyl chloride showed that the growing carbanion and phosphonium ion concentrations were equal. 

Clark and Tedder have studied the fluorination of carbon tetrachloride by flowing together F2 and CCI4, both diluted in nitrogen. FCl was converted to HF and HCl followed by titration of fluoride and spectrophotometric determination of the chloride. Experiments at 20 °C are interpreted in terms of the mechanism... 

N-(m/is-Cinnamoyllmidazole (1). Mol. wt. 198.22, m.p. 133-133.5°. Prepared in high yield by reaction of cinnamoyl chloride with imidazole in benzene at 10-25°. The reagent reacts rapidly and quantitatively with the active site of a-chymotrypsin and hence can be used for the spectrophotometric determination of the normality of an enzyme solution by titration. 

If higher sensitivities are desired then the ammonium phosphomolybdate product may be reduced with stannous chloride or ascorbic acid in order to give soluble molybdenum blue [24]. Spectrophotometric determination of the blue absorbance at 885 nm gives a detection limit of 0.003 mg/L phosphate, stated as phosphorus (3 ppb in freshwater) or 0.0092 mg/L as expressed phosphate [24]. 

The oxidizing properties of chlorate are utilized in its spectrophotometric determination. Chlorate admixtures in perchlorates have been determined by its colour reaction with benzidine [44] and J(5-thiosemicarbazone dimedone (e= 1.910 at 417 nm) [45]. Chlorate in water has been determined with o-tolidine [46]. At a suitably high chloride concentration in 3-7 M H2SO4, chlorate reacts quantitatively with Cf to form CI2, which decreases the absorbance of Methyl Orange [47]. 

Besides Rhodamine 6G (see above). Malachite Green and Crystal Violet form ion-associates with the anionic iridium chloride-SnCl j complexes and these ean also be used for flotation-spectrophotometric determination of iridium. The molar absorptivity e with Malachite Green is 1.55-10 [77,78]. 

Besides PAN, numerous other pyridylazo reagents have been proposed for spectrophotometric determination of Zn. This group comprises the related reagent PAR [14,47-50]. The complex of Zn with PAR is extracted with chloroform in the presence of cetyldimethylbenzylammonium chloride (e = 9.1-10 ) [51]. Zinc (and other heavy metals) are preconcentrated on a cation-exchanger, modified with PAR [52]. Bromo- and chloro-derivatives of pyridylazo compounds have become a basis for more sensitive methods, e.g., 5-Br-PADAP, (formula 4.3) [53,54], 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol (3,5-diBr-PADAP) (e = 1.3-10 at 570 nm) [55], and other bromine derivatives [56]. Application of the chlorine derivatives of pyridylazo reagents has been reviewed [53,57,58]. 

Solid-phase extraction of various analyte complexes on e.g. microcrystalline naphthalene (Ni [23] and Cu [24] with nitroso-R salt and tetradecyldimethylbenzylammonium chloride), ammonium tetraphenylborate-naphthalene (U with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol) [25], chitin column (Cr(VI) with 1,5-diphenylcarbazide) [26], strong anion-exchange cartridge (Cr(VI) at pH 8) [27], Cig cartridge (CL-azo dye) [28] and minicolumn (As with ammonium diethyl dithiophosphate) [29], silica modified chemically with A-allyl- or A-phenyl-TV -propylthiourea (OSO4) [30] and Sephadex DEAE A-25 (chloride form) (V with Eriochrome Cyanine R) [31] prior to the spectrophotometric determination has recently been reported. The application of solid-phase spectrophotometry to determine nitrite and nitrate in water samples has recently been described [32]. 

Dimethoxyhydroxyphenylflurone has been proposed as a chromogenic reagent for the spectrophotometric determination (e = 1.3610 1 mof cm ) of trace amounts of Mo in steel and pure iron [4]. Thiazolylazo compounds were used as chromogenic reagents to determine Mo in human urine [5]. Thiazolyl blue tetrazolium bromide and 3,4,5-trihydroxybenzoic acid and nitrobluetetrazolium chloride were employed to determine Mo in soil [6,7]. 

By use of releasing agents Considering the reaction M-X-i-R = R- Xh-M, it becomes evident that an excess of the releasing agent (R) will lead to an enhanced concentration of the required gaseous metal atoms (M) which will be of special significance if the product R-X is a stable compormd. Hence in the determination of calcium in presence of phosphate the addition of excess of strontium chloride to the test solution will lead to the formation of strontium phosphate and the calcium can then be determined in an acetylene-air flame without any interference due to phosphate. Also addition of EDTA to a calcium solution before analysis may increase the sensitivity of the subsequent flame spectrophotometric determination which may be due to the formation of an EDTA complex of calcium which is readily dissociated in the flame. 

J. Ruzicka, J.W.B. Stewart, E.A.G. Zagatto, Flow injection analysis. Part IV. Stream sample splitting and its application to the continuous spectrophotometric determination of chloride in brackish waters, Anal. Chim. Acta 81 (1976) 387. 

This innovation generally involves modifications to the operation of the sampler and random access reagent selection, and can be implemented in both segmented and unsegmented flow analysers. For unsegmented flow analysis, the spectrophotometric determination of zinc and phosphate in soil extracts [368] is a good example. Zinc was determined only when phosphate was present at concentrations above a threshold level. The number of determinations required was reduced by 30%. Analogously, an expert flow system was proposed for the turbidimetric determination of chloride and sulphate in natural waters [369]. Both methods were implemented in the same manifold, and the need for sulphate determination was dependent on the chloride concentration determined. 

A column of silver chloranilate was used for chloride ion determination in a FIA system. According to reaction 3, the column liberates into the solution violet chloranilate ions (38), that are measured with a spectrophotometric detector at 530 nm. The method is fast (30 samplesh-1) and was applied to the analysis of fresh and waste waters (1-20 ppm Cl-) with negligible interference of other anions107. 

EXPERIMENT 37 SINGLE-LINE FIA SPECTROPHOTOMETRIC DETERMINATION OF CHLORIDE... 

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