Spectrophotometric determination of iodine species in table salt and pharmaceutical preparations

A sensitive spectrophotometric method for the determination of iodine species like iodide, iodine, iodate and periodate is described. The method involves the oxidation of iodide to ICl(2)(-) in the presence of iodate and chloride in acidic medium. The formed ICl(2)(-) bleaches the dye methyl red. The decrease in the intensity of the colour of the dye is measured at 520 nm. Beer's law is obeyed in the concentration range 0-3.5 microg of iodide in an overall volume of 10 ml. The molar absorptivity of the colour system is 1.73 x 10(5) l mol(-1) cm(-1) with a correlation coefficient of -0.9997. The relative standard deviation is 3.6% (n=10) at 2 microg of iodide. The developed method can be applied to samples containing iodine, iodate and periodate by prereduction to iodide using Zn/H(+) or NH(2)NH(2)/H(+). The effect of interfering ions on the determination is described. The proposed method has been successfully applied for the determination of iodide and iodate in salt samples and iodine in pharmaceutical preparations.     

Direct determination of nanogram amounts of iodine by atomic-absorption spectroscopy using a graphite-tube atomizer

The direct determination of iodine by AAS at its 183.0 and 178.2 nm resonance lines by using a small graphite-tube atomizer, electrodeless discharge-lamp source and vacuum monochromator is described. Optimum conditions for the determination of iodine have been established; similar sensitivity is obtained when iodide or iodate samples are examined. With 10 mul aqueous samples sensitivities (for 1% absorption) of 4 x 10(-10) g and 2 x 10(-10) g of I were obtained at 183.0 and 178.2 nm respectively; a detection limit of 2 x 10(-10) g was observed at both lines. Non-specific molecular absorption from common inorganic salts causes interference with the determination; the iodine non-resonance line at 184.4 nm may be employed to correct for this interference when moderate amounts of common salts are present.     

Spectrophotometric study of the reaction mechanism between DDQ as pi-acceptor and potassium iodate and flucloxacillin and dicloxacillin drugs and their determination in pure and in dosage forms

Two simple and accurate spectrophotometric methods are presented for the determination of beta-lactam drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure and in different pharmaceutical preparations. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) pi-acceptor and potassium iodate via oxidation reduction reaction where the highly coloured complex species or the liberated iodine have been spectrophotometrically studied. The optimum experimental conditions have been studied carefully. Beer's law is obeyed over the concentration range of 2-450 microg ml(-1) for Fluclox and 10-450 microg ml(-1) for Diclox using DDQ reagent and at 50-550 microg ml(-1) for Fluclox and 50-560 microg ml(-1) for Diclox using iodate method, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 6-450 and 15-450 microg ml(-1) for Fluclox and Diclox using DDQ, respectively, and 65-550 and 63-560 microg ml(-1) for Fluclox and Diclox using iodine, respectively. The Sandell sensitivity is found to be 0.018 and 0.011 microg cm(-2) for DDQ method and 0.013 and 0.011 microg cm(-2) for iodate method for Fluclox and Diclox, respectively, which indicates the high sensitivity of both methods. Standard deviation (S.D.=0.01-0.80 and 0.07-0.98) and relative standard deviation (R.S.D.=0.13-0.44 and 0.11-0.82%) (n=5) for DDQ and iodate methods, respectively, refer to the high accuracy and precision of the proposed methods. These results are also confirmed by between-day precision of percent recovery of 99.87-100.2 and 99.90-100% for Fluclox and Diclox by DDQ method and 99.88-100.1 and 99.30-100.2% for Fluclox and Diclox by iodate method, respectively. These data are comparable to those obtained by British and American pharmacopoeias assay for the determination of Fluclox and Diclox in raw materials and in pharmaceutical preparations.     

Indirect determination of tungstate in rat tissues by atomic absorption spectrometry

An indirect method is described for the determination of tungsten as tungstate in tissue samples by atomic absorption spectrometry (AAS). Tungstate forms a stable ion-association complex [Fe(dipy)3]2+WO4(2-) (dipy = 2,2'-dipyridyl) in acidic solution, which can be extracted into chloroform with an efficiency of higher than 98%. The extract can be analysed for iron (and hence indirectly for WO4(2-] by flame AAS after stripping back into 60% perchloric acid. The calibration graph is linear up to 19 p.p.m. of WO4(2-) and the limit of detection is 0.17 p.p.m. Many foreign ions do not interfere and the method has been applied successfully to the determination of tungstate in rattus norvegicus tissue samples.     

Sequential flow injection determination of iodate and periodate with spectrophotometric detection

A flow injection (FI) system is described for the sequential determination of periodate and iodate based on their reaction with iodide at pH 3.5. Two sample plugs were injected into the same carrier stream sequentially. One injection is for the iodate determination and the other for the sum of iodate and periodate determination. For iodate determination, molybdate solution buffered at pH of 3.5 was used for selective masking of periodate. The influences of reagent concentrations were studied by a univariable method and the influence of FI manifolds was studied using univariable and simplex method. Periodate and iodate can be determined in the range of 0.050-5.0 and 0.050-10 microg/ml, respectively. The 3 sigma limit of detection was 0.030 and 0.050 microg/ml for periodate and iodate, respectively. The proposed method has been applied for the sequential determinations of periodate and iodate in water samples.     

(NH_4)_(42)[Mo_(132)O_(372)(CH_3COO)_(30)(H_2O)_(72)]膜修饰电极的构筑和电化学性质的研究

由于过渡金属替代的多金属氧酸盐(polyoxometalates)的催化、磁性、电化学等性质,越来越受到人们的关注~([1-7]). 目前世界上约有10亿人生活在缺碘地区,碘的缺乏严重影响人类健康.对食物、生物临床、环境及工业中碘含量检测很有实际意义.     

间接原子吸收法测定药物制剂中利血生的含量

提出了利血生的间接原子吸收法，该法基于利血生在碱性介质中的分离－产物半胱氨酸在适当的PH条件下与铜离子生成灰色沉淀，通过测定上清液中铜的含量来间接测定利血生的含量，在法在10－100mg/L范围内呈良好的线性关系（r=0.9992),回收率为98．5％－101．6％。该法可成功地用于药物制剂中利血生的测定。     

Sensitive kinetic-spectrophotometric determination of iodate in iodized table salt based on its accelerating effect on the reaction of bromate with chloride ion in the presence of hydrazine.

A simple, precise, sensitive and accurate method was developed for rapid determination of trace quantities of iodate. The method is based on the accelerating effect of iodate on the reaction of bromate and chloride acid in the presence of hydrazine in acidic media. The decolorization of Methyl Orange with the reaction products was used to monitor the reaction spectrophotometrically at 525 nm. Iodate could be determined in the concentration ranges of 0.03 - 1.2 microg ml(-1). The relative standard deviation for ten replicate determinations of 0.3 microg ml(-1) of iodate was 1.65%. The proposed method was applied to the determination of iodate in table salts with satisfactory results.     

Indirect atomic absorption spectrometric determination of sulfate in human blood serum.

An indirect method for the determination of sulfate by atomic absorption spectrometry (AAS) is described. Sulfate forms a stable ion-association complex, [Cu(neocuproine)2]2+(SO4(2-)), in neutral medium, which can be extracted into isobutyl methyl ketone in the presence of a polar medium (methanol) with an efficiency higher than 98.0% and the extract can be analysed directly for copper (and hence indirectly for sulfate) by AAS. Measurement of the copper atomic absorption signal from the organic phase allows the indirect determination of 0.14-1.12 micrograms ml-1 of sulfate, giving a 450-fold increase in sensitivity over the conventional method of precipitation with barium. The limit of detection (3 sigma) is 3.2 ng ml-1 which is better than that of ion chromatography (0.15 micrograms ml-1). Indirect AAS allows the accurate assay of inorganic sulfate anion in biological fluids and tissues. The sulfate concentration determined by the proposed method in human blood serum (n = 6 in each instance) was 35.4-43.3 micrograms ml-1 in normal persons, 50.3-62.5 micrograms ml-1 in jaundice patients and 83.3-155.6 micrograms ml-1 in diabetic patients. A good correlation between measured sulfate and the sulfate added to blood serum was obtained.     

Colorimetric determination of inorganic iodine in fortified culinary products

The presented colorimetric procedure only requires simple laboratory equipment and is suitable as a routine procedure for checking concentrations of iodine in fortified culinary products. The Moxon and Dixon colorimetric procedure for iodine determination has been optimised for the determination of iodide and iodate in fortified culinary products, always containing high salt levels. The high sensitivity of the method permits a high dilution of the product solutions, thus reducing interferences from the inherent colour of the products. The calibration is linear in the range from 0 to 12 microg L(-1) of iodine with R2 > 0.99. A series of commercial culinary products were used to validate the method. Recoveries of iodine, added as iodide and/or iodate, were generally in the range 100+/-10%. High concentrations of chloride are essential to obtain a complete recovery of iodate. Limit of quantification was estimated to be 2 mg kg(-1) of product, based on 2-3 g of product. Concentrations of iodine determined with this method were similar to those obtained by an ICP-MS procedure.     

Reverse flow injection spectrophotometric determination of iodate and iodide in table salt

A very simple and sensitive reverse flow injection method is described for the determination of iodate and iodide. The iodate reacts with excess iodide in acidic medium to form tri-iodide, which can be spectrophotometrically monitored at 351 nm, and the absorbance is directly related to the concentration of iodate in the sample. The determination of iodide is based on oxidizing iodide to iodate. The calibration curve is linear in the range of 0.02-3.0 μg ml⁻¹ I with r²=0.9998, and the limit of detection is 0.008 μg ml⁻¹ I. The chemical and flow injection variables were studied and optimized to make the procedure suitable for quantitating iodate and iodide in table salts. It is shown that the reverse flow injection analysis could greatly improve the sensitivity and precision for determination of iodate with a relative standard deviation of 0.9%. A complete analysis, including sampling and washing, could be performed in 35 s. The procedure was applied successfully to the determination of iodate and iodide in table salts, and the results were statistically compared with results determined by standard iodometry method.     

Kinetic study and analytical application of the iodate-hypophosphite reaction in strongly acidic solutions

The iodate—hypophosphite reaction in strongly acidic solutions was studied spectrophotometrically. Reaction rate constants and the activation energy of the reaction are reported. A method for determining hypophosphite on the basis of this reaction is described. Hypophosphite in the range 0.06–4 mg (10^-3–6·10^-2 M) can be determined with a relative error and relative standard deviation of 2—3%.     

Spectrofluorimetric flow injection determination of trace amounts of periodate

A sensitive, rapid and selective procedure is proposed for the flow injection determinations of periodate by spectrofluorometric detection. The method is based on the reaction of periodate with Alizarin Navy Blue in basic solution. The reagents and manifold variables influence on the sensitivity have been investigated and the optimum conditions are established. Periodate can be determined for the range of 0.250-5.00 microg ml(-1) with a limit of detection of 0.08 microg ml(-1), and with a sample rate of 15 +/- 2 samples h(-1). The relative standard deviations for eight replicate determination of 0.500 and 5.00 microg ml(-1) was 1.3 and 1.1%, respectively. Periodate can be determined in the presence of iodate and bromate. The proposed method was used to determination of periodate in water samples.     

Microchemical determination of lodate and iodide in sea waters by flow injection analysis

A flow injection analysis method for iodate and iodide in sea water is described. The system involves spectrophotometric detection based on the catalytic, fading effect of either iodate or iodide on the indicator reaction of iron (III) thiocyanate and nitrite. With and without an anion-exchange column in the flow conduit, the system allows the determination of iodate and total iodine, respectively; iodide can be found by difference. Both iodate-iodine and total iodine can be determined in the range 0.75 to 150 g/1 on the sea water basis with analysis times of 20 min for iodate-iodine and 9 min for total iodine. The RSDs are within 1.3% for both iodate and iodide. Results are presented for the determination of iodate and iodide in sea waters and some brines associated with natural methane gas evolution.     

Liquid-phase microextraction-gas chromatography-mass spectrometry for the determination of bromate, iodate, bromide and iodide in high-chloride matrix

In the determination of bromate and iodate, any free bromide and iodide present was quantitatively removed by anion exchange with silver chloride exploiting the differences in silver salts solubility product, being AgCl, 1.8 x 10(-10), AgBr, 5.0 x 10(-13), AgI, 8.3 x 10(-17), AgBrO(3), 5.5 x 10(-5) and AgIO(3), 3.1 x 10(-8). The oxyhalides were reduced with ascorbic acid to halides and converted to 4-bromo-2,6-dimethylaniline and 4-iodo-2,6-dimethylaniline by their reaction with 2-iodosobenzoate in the presence of 2,6-dimethylaniline at pH 6.4 and 2-3, respectively. Single drop microextraction (SDME) of the haloanilines in 2 microl of toluene and injection of the whole extract into GC-MS, or liquid-phase microextraction (LPME) into 50 microl of toluene and injection of 2 microl of extract, resulted in a sensitive method for bromate and iodate. The latter method of extraction has been found more robust, sensitive and to give better extraction in shorter period than SDME. Total bromine/iodine was determined without any treatment with silver chloride. High concentration of chloride in the matrix did not interfere. A rectilinear calibration graph was obtained for 0.05 microg-25 mg l(-1) of bromate/bromide and iodate/iodide, the limit of detection were 20 ng l(-1) of bromate, 15 ng l(-1) of iodate, 20 ng l(-1) of bromide and 10 ng l(-1) of iodide (by LPME in 50 microl of toluene). The method has been applied to seawater and table salt. From the pooled data, the average recovery of spiked oxyhalide/halide to real samples was in range 96.7-105.7% with RSD in range 1.6-6.5%.     

Spectrophotometric determination of bromide (and iodide) in a flow system after oxidation by peroxodisulphate

The peroxodisulphate method for the determination of bromide has been modified. A flow-injection system for the spectrophotometric finish has been developed and the size of the ion-exchange column in the preconcentration step has been scaled down. The sum of bromate and iodate produced in the oxidation is determined by treating the oxidized sample with iodide in hydrochloric acid. The iodate is separately determined by applying the reaction in acetic acid. The working range of the spectrophotometric finish is 1-15muM and the limit of determination (10 sigma) is 0.7muM for iodate and for iodate plus bromate. The enrichment factor in the preconcentration step is 50, yielding a limit of determination of 15nM for bromide in natural waters. Eighteen samples of water from the Baltic, with salinity ranging from 3 to 33%. have been analysed. A Br/Cl ratio of (1.53 +/- 0.02) x 10(-3) was found. A comparative study of the original and the new preconcentration step has been made with three river waters, rich in humic substances. The results agreed within +/- 1. 5%.     

Triphenyltetrazolium chloride for determination of iodate and periodate

Optimum conditions for complexation in the systems triphenyl-tetrazolium chloride-iodate-iodide-dichlorethane and triphenyltetrazolium chloride-periodate-iodide-dichlorethane were found. The molar absorptivity of the complex was 7.48 x 10(4) 1. mole(-1). cm(-1) for the iodate, and 9.09 x 10(4)1. mole(-1) cm(-1) for the periodate. Beer's law is adhered to in the range of 0.04-0.7 mug/ml for iodate and 0.02-0.35 mug/ml for periodate. The influence of foreign ions was studied. Cr(VI), Hg(II) and S(2)O(2-)(3) interfere. The proposed method has been applied to analysis of iodate and periodate in fresh water.     

Chemical enhancement method for the determination of mercury by spectrophotometry after iodide extraction

A selective and sensitive spectrophotometric method for the determination of 0.08-2.5 ppb of mercury(II) is described. Mercury is extracted as tetraiodomercury(II)-Cd-phenanthroline ion-pair into benzene and selectively stripped into EDTA. The iodide associated with mercury present in the stripping is oxidized to iodate and then treated with excess iodide to give iodine. The iodine formed is extracted into benzene and equilibrated with iodate in acidic medium in the presence of chloride and Rhodamine 6G for the formation of ICI(-)(2) species and its extraction as ion-pair with Rhodamine 6G. Determination is completed by measuring the absorption of the extract at 535 nm. The coefficient of variation is 1.5% for 10 determinations of 200 ng of mercury. The method has been applied to establish the mercury content of natural waters and chloralkali plant effluent.     

Spectrophotometric determination of periodate and iodate by a differential kinetic method

A rapid, simple and sensitive differential kinetic method is presented for the determinations of periodate and iodate ions. The method is based on their reaction with iodide in the presence of methylene blue. The reactions can be monitored spectrophotometrically by measuring the decrease in absorbance at 665 nm. Two sets of conditions were established that in one set of conditions only periodate reacted with iodide but in the other set both the ions reacted with iodide during the first 180 s after initiation of the reaction. The data were evaluated by proportional equations. The method allowed the determination of periodate and iodate at concentrations between 0.1 and 1.0 and 0.1 and 1.3 mug ml(-1), respectively. The method was applied to the determination of periodate and iodate in tap water and spring water with satisfactory results.     

Determination of the purity of potassium iodate by constant-current coulometry

This paper describes a method of determining the purity of potassium iodate by constant-current coulometry. The determination can be divided into two steps. First, a Na₂S₂O₃ solution is prepared and its reductive value is determined. Second, the purity value of an oxidimetric quantity of potassium iodate is determined. This paper discusses the conditions of the reaction process and evaluates type A and B standard uncertainty of this method. The expanded relative uncertainty of this method is 0.02% (k=2). Received: 15 June 2000 Accepted: 27 December 2001