Kinetic-photometric determination of iodide based on its inhibitory effect on the bromate oxidation of Victoria Blue 4-R.

A new sensitive kinetic method has been developed for the determination of trace amounts of I- over the range of 50-300 ng cm(-3). The method was based on the inhibitory effect of iodide on the oxidation of Victoria Blue 4-R by KBrO3. The reaction is monitored spectrophotometrically at 596.3 nm. Method development includes optimization of reagent concentration and temperature. The kinetic parameters of the reaction were reported and a rate equation was suggested. The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. The proposed method was successfully applied to the determination of iodide in real samples. The new developed method was found to have fairly good selectivity, sensitivity, simplicity and rapidity.     

Kinetic spectrophotometric method for the determination of trace amounts of oxalate by an activation effect.

A new, simple and inexpensive kinetic catalytic spectrophotometric method for the determination of oxalate is described. The method is based on an activation effect of oxalate on a catalytic effect of iron(II) on the oxidation of iodide by bromate. The reaction is monitored by measuring the absorbance of triiodide ion at lambda max = 352 nm. A calibration graph was obtained from 0.10 - 7.0 microg cm(-3) of oxalate with a detection limit of 0.080 microg cm(-3). The standard deviations for ten replicate determinations of 0.50, 1.0 and 5.0 microg cm(-3) of oxalate were 4.0, 2.6 and 1.8%, respectively. The applicability of the method was demonstrated by the determination of oxalate ion in real samples.     

Catalytic determination of nanogram amounts from iron(III) using its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by hydrogen peroxide

A kinetic method is described for the determination of iron(III) based on its catalytic effect on the oxidation of sodium pyrogallol-5-sulphonate by hydrogen peroxide. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance of the coloured product at 436.8 nm. Nanogram amounts of iron(III) (2.0-75.0 ng cm(-3)) can be determined with good accuracy and reproducibility. The influence of foreign ions on the results was investigated and the method was found to be adequately selective. It has been applied satisfactorily to the determination of iron(III) in tap water samples. The kinetic parameters of both the catalysed and uncatalysed reactions are reported.     

Kinetic spectrophotometric determination of thiocyanate based on its inhibitory effect on the oxidation of methyl red by bromate.

A kinetic spectrophotometric method for measuring thiocyanate is described. The proposed method is based on the inhibitory effect of thiocyanate on the oxidation of Methyl Red by bromate in the presence of nitrite, which was monitored at 520 nm. The variables affecting the rate of the reaction were investigated and the optimum conditions were established. Thiocyanate can be measured in the range of 0.05-1.1 microg ml(-1) with a detection limit of 0.025 microg ml(-1). This method has been used to determine trace thiocyanate in urine and tap water samples.     

Kinetic spectrophotometric determination of traces of molybdenum(VI) by its inhibitory effect on the oxidation of 4-hydroxycoumarine by potassium permanganate.

The present paper describes a simple, selective and sensitive kinetic method for the determination of trace amounts of molybdenum(VI) based on its inhibitory effect on the reaction oxidation of 4-hydroxycoumarine by KMnO(4) in the presence of hydrochloric acid, at pH 1.75 at 25 degrees C. The rate of the indicator reaction was followed spectrophotometrically by measuring the decrease in the absorbance of KMnO(4) at 525 nm. The development method includes optimization of the reagent concentration and temperature. The calibration graph was linear in the range of concentrations from 20 to 200 ng/cm(3) of molybdenum(VI). The probable relative error was in the interval 3.10 - 10.52% for the concentration range of 200 - 20 ng/cm(3) molybdenum(VI), respectively. The interference effects of the foreign ions were determined to assess the selectivity of the method. The developed method was found to have relatively good selectivity, sensitivity, simplicity and rapidity. The proposed method was applied to the determination of molybdenum(VI) in a particular type of steel and alloy (hastelloy).     

Spectrophotometric determination of urea in dermatologic formulations and cosmetics

A rapid, relatively sensitive, and low-cost method for the determination of water-soluble urea content in dermatological therapy products and cosmetics is proposed using a new spectrophotometric assay with water as the only extraction solvent. Spectrophotometric methods involve addition of a known excess of bromate to urea in an acid medium, followed by the determination of residual bromine and chlorine reacting with methyl orange and measurement of absorbance at 505 nm. The absorbance increases linearly with urea concentration (r = 0.9998). The systems obey Beer's law for 6 - 90 microg ml(-1). The calculated apparent molar absorbance values are found to be 4.537 x 10(3) dm(3) mol(-1) cm(-1) and the Sandell's sensitivity is 0.013 microg cm(-2). The variables affecting the rate of the reaction were investigated. The relative standard deviation for five-replication determination of 60 microg ml(-1) urea was 2.1% and the detection limit of the method is 0.34 ng ml(-1).     

Kinetic determination of traces of iodide by its catalytic effect on oxidation of sodium pyrogallol-5-sulfonate by hydrogen peroxide.

The kinetic method is based on a catalytic effect on the oxidation of sodium pyrogallol-5-sulfonate by hydrogenperoxide. The reaction is followed spectrophotometrically at 436.8 nm. The kinetic parameters of the reaction are reported and a rate equation is suggested. The calibration graph is linear in the range 10-200 ng cm(-3). The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. This method has high sensitivity and good selectivity when anions are concerned as well. That is why it can be successfully applied to determination of iodide in real samples (mineral water and soil) directly after the elimination of cations, which interfere. The method was applied to determine iodide in natural waters and soil.     

Spectrophotometric determination of trace amount of copper(II) ion based on complexation with an anthraquinone derivative.

The spectrophotometric determination of Cu(II) with an anthraquinone derivative (Alizarin Red S) has been investigated. The experimental conditions, such as the pH of the sample and concentration of ligand, were optimized. This method is simple and sensitive for determination of Cu(II) ion. The interfering effects of diverse ions were investigated. Copper ion was determined by measuring the absorbance of the Cu(II)-ARS complex at 510 nm. Beer's law was obeyed over the concentration range of 0.011 - 0.320 mmol dm(-3) and the detection limit (S/N = 3) was 0.038 microg cm(-3). The relative standard deviation at 20 microg cm(-3) was 1.02% (n = 5). The method was applied for real samples.     

Kinetic method for determination of ascorbic acid on flow injection system by using its catalytic effect on the complexation reaction of an ultra sensitive colorimetric reagent of porphyrin with Cu(II)

A kinetic method performed on a flow injection system is described for the determination of ascorbic acid by using its catalytic effect on the complexation reaction of Cu(II) with 5,10,15,20-tetrakis(4-N-trimethyl-aminophenyl)porphyrin. The characteristic spectrum of porphyrin (Soret band), which shows intense absorption around 400 nm (epsilon>2.0 x 10(5) cm(-1)M(-1)), was used first time for determining ascorbic acid. By incorporating the complexation reaction into a flow injection system, ascorbic acid could be determined either over a broad dynamic range of 0.1-1000 microg/ml or at a trace level below 5 ng/ml. Good repeatability was also achieved by testing a working standard of 0.1 microg/ml with 10 injections at a throughput of 35 h(-1), obtaining a relative standard deviation of 0.11%. Substances like amino acids, vitamins, sugars, organic acids and metal ions, showed no or little interference even present at high concentrations. The method was validated in the determination of ascorbic acid contents of some commercially available soft drinks by comparison with the official 2,6-dichloroindophenol method with reasonable agreement.     

Copper(II)-catalysed oxidative coupling reaction of 3-hydroxyacetanilide with 3-methyl-2-benzothiazolinone hydrazone for the spectrophotometric determination of traces of copper(II)

A spectrophotometric method is developed for the determination of traces of copper(II), based on the catalytic oxidative coupling reaction of 3-hydroxyacetanilide with 3-methyl-2-benzothiazolinone hydrazone in the presence of ammonia and hydrochloric acid. Beer's law is obeyed in the copper(II) concentration range of 0.008-0.16 microg mL(-1), and the molar absorptivity at 530 nm is 2.5x10(5) L mol(-1) cm(-1). The Sandell's sensitivity of the product is 0.000254 microg cm(-2). The optimum reaction conditions and other important analytical parameters have been investigated. The proposed method is applied to the analysis of water and soil samples and the results are compared with the literature method.     

Separation and determination of enkephalin-related peptides using capillary electrophoresis

CZE with UV-absorption detection has been used for the separation and determination of enkephalin-related peptides. The experimental conditions, such as pH and concentration of running buffer, applied voltage, injection method, and time, were investigated in detail. Excellent separation efficiency could be obtained for ten enkephalin-related peptides with a 50 microm (ID) x 58 cm capillary using sodium dihydrogen phosphate as the running buffer (pH 3.11) when 20 kV of applied voltage was used. The concentration detection limits were found to be in the range of 0.31-1.94 microg/mL (defined as S/N = 3). The proposed method has been applied to analyze the spiked cerebrospinal fluid (CSF) sample, and the results showed that CZE is a powerful technique for separation and detection of the above biological peptides.     

1-(2-hydroxy-3-methoxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid as a reagent for the spectrophotometric determination of boron in ceramic materials

A sensitive and selective spectrophotometric method for the determination of boron is described. The method is based on the colour reaction between boron and the reagent 1-(2-hydroxy-3-methoxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid (HMOA). In a HOAc-NH4OAc buffer of pH 5.5, HMOA reacts with boron to form a 1:2 yellow complex with a maximum absorption at 423 nm. The absorbance (lambdamax = 423 nm) is linear up to 1.2 microg ml(-1) boron in aqueous solution with a repeatability (RSD) of 1.12%. The molar absorptivity and Sandell's sensitivity are 7.19 x 10(3) l mol(-1) cm(-1) and 0.0015 microg cm(-2), respectively. The limit of quantification and limit of detection were found to be 17.1 and 5.2 ng ml(-1), respectively. The interference of various ions was examined in detail. All the metal ions studied can be tolerated in considerable amounts; in particular, the tolerance limits of Fe, Al, Zn, Ca and Mg are superior to those of other reagents such as Azomethine-H and Azomethine-HR. The proposed method was applied to the determination of boron in ceramic materials with satisfactory results.     

Application of H-point standard addition method and partial least squares to the simultaneous kinetic-potentiometric determination of hydrazine and phenylhydrazine

Simultaneous determination of hydrazine (HZ) and phenylhydrazine (PHZ) by H-point standard addition method (HPSAM) and partial least squares (PLS) regression was carried out based on kinetic data from novel potentiometry methods. The rate of chloride ion production in the reaction of HZ and PHZ with N-chlorosuccinimide (NCS) was monitored by a chloride ion-selective electrode. The experimental data show the good ability of ion-selective electrodes (ISEs) as detectors not only for the direct determination of chloride ion but also for simultaneous kinetic-potentiometric analysis using HPSAM and PLS methods. The methods are based on the differences observed in the production rate of chloride ions. The results show that simultaneous determination of HZ and PHZ can be performed in concentration ranges of 0.5 - 20.0 and 0.8 - 25.0 microg mL(-1), respectively. The total relative standard error for applying the PLS method to 8 synthetic samples in the concentration ranges of 1.0 - 16.0 microg mL(-1) for HZ and 2.0 - 16.0 microg mL(-1) for PHZ was 3.96. In order for the selectivity of the method to be assessed, we evaluated the effects of certain foreign ions upon the reaction rate and assessed the selectivity of the method. Both methods (PLS and HPSAM) were evaluated using a set of synthetic sample mixtures and then applied for simultaneous determination of HZ and PHZ in water samples.     

Highly sensitive reaction of nitrate with brucine and 3-methyl-2-benzothiazolinone hydrazone hydrochloride for the determination of nitrate in environmental samples.

A modified and highly sensitive spectrophotometric method for the determination of nitrate in trace quantities in environmental samples is described. The method is based on the reaction of nitrate ion with brucine and 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in sulfuric acid medium to yield a violet-colored product which is stable for over two days. The optimum photometric range for the determination of nitrate is 0.04-0.16 microg cm(-3) and the Sandell's sensitivity being 0.000279 microg cm(-2). The proposed method is applied to various water samples and the results indicate that the reaction is highly sensitive than the original brucine method.     

A simple and rapid spectrophotometric determination of thallium(III) with trifluoperazine hydrochloride.

A simple, sensitive and rapid spectrophotometric method was developed for the determination of thallium(III) using trifluoperazine hydrochloride (TFPH). The method is based on the oxidation of TFPH by thallium(III) in a phosphoric acid medium to form a red-colored radical cation with an absorption maximum at 505 nm. Beer's law is valid over the concentration range of 0.5 - 6.5 microg ml(-1) of thallium(III). The molar absorptivity and Sandell's sensitivity of the color system are 2.14 x 10(4) l mol(-1) cm(-1) and 0.0095 microg cm(-2), respectively. The optimum reaction conditions and other analytical parameters were evaluated. The tolerance limit of the method towards various ions usually associated with thallium has been studied. The proposed method has been successfully applied to the analysis of thallium in alloys, minerals, standard reference material, water, and urine samples.     

Determination of diclofenac sodium in commercial pharmaceutical formulations and human control serum using a kinetic-spectrophotometric method

A kinetic method for the determination of micro quantities of diclofenac sodium (DS) is described in this paper. The method is based on a ligand-exchange reaction. The reaction was followed spectrophotometrically by monitoring the rate of appearance of the cobalt diclofenac complex at 376 nm. The optimum operating conditions regarding reagent concentrations and temperature were established. The optimized conditions yielded a theoretical detection limit of 1.29 microg ml(-1) based on the 3S(b) criterion. The interference effects of certain drugs, foreign ions and amino acids upon the reaction rate were studied in order to assess the selectivity of the method. The developed procedure was successfully applied to the rapid determination of diclofenac sodium in commercial pharmaceutical preparations and human control serum. The unique features of this procedure are that determination can be carried out at room temperature and the analysis time is short. The newly developed method is simple, inexpensive, and efficient for use in the analysis of a large number of samples.     

Kinetic determination of trace levels of selenium(IV) and total selenium by Nile Blue A/hydrogen peroxide method

A kinetic method for the determination of selenium(IV) traces is proposed, based on its inhibitory action on the oxidation of Nile Blue A by hydrogen peroxide in phosphate buffer (pH 10.5). A linear dependence was established between the rate of the proposed indicator reaction and selenium concentration in the range 9.5 × 10^–2-1.58 ng cm^–3. The experimental conditions of maximal selenium effect were established. Selenium, determined by the tangent method, was determined at concentrations over the range 0.22–1.26 ng cm^–3, with relative standard deviations up to 4.5%. The reaction rate was followed spectrophotometrically. The effect of foreign ions on the accuracy of this method was also investigated. The method was applied to the determination of selenium in pharmaceutical preparations and wheat flour.     

Spectrophotometric determination of periodate, iodate and bromate mixtures based on their reaction with iodide.

A rapid, simple, precise and accurate method is proposed for the determination of ternary mixtures of periodate-iodate-bromate based on their reaction with iodide ion at different pH values. The absorbance was measured at 352 nm. Three sets of reaction conditions were developed. In the first set of conditions, only periodate reacted with iodide, but in the second set the periodate and iodate reacted with iodide and in the third set the three ions reacted with iodide during the first 3 min after initiation of the reaction. The method could be used for individual determinations of periodate, iodate and bromate in the concentration range of 0.05-8.0 microg/ml, 0.05-5.0 microg/ml and 0.2-12 microg/ml, respectively. The data were evaluated by simultaneous equations.     

Novel sensitive spectrophotometric method for the trace determination of cyanide in industrial effluent.

The high toxicity of the cyanide ion at low concentration necessitates its analysis in a variety of environmental samples with a very low cyanide content. A new sensitive spectrophotometric method has been developed for the trace determination of cyanide with ninhydrin (NH) in an alkaline medium. Beer's law is obeyed in the range of cyanide concentration 0.04-0.24 microg cm(-3), and the molar absorptivity at 590 nm is 2.20 x 10(5) dm3 mol(-1) cm(-1). The Sandell's sensitivity of the product is 0.000118 microg cm(-2). The optimum reaction conditions and other important analytical parameters have been investigated. The results obtained by using the proposed method for environmental samples agree well with those obtained by the Aldridge standard method.     

Determination of aluminum in large volume parenteral drug products used in total parenteral nutrition therapy by ICP-MS with a dynamic reaction cell

The proposed method was developed for the determination of aluminum (Al) in large volume parenteral (LVP) drug products used in total parenteral nutrition (TPN) therapy. The determination of Al in LVP drug products was performed by an inductively coupled plasma mass spectrometer equipped with a dynamic reaction cell (DRC-ICP-MS). DRC-ICP-MS conditions for the analysis of Al were studied to obtain the best signal to background (S/N) ratios. The interfering polyatomic ions at mass 27 (Al) were reduced by using NH(3) as a reaction gas. The detection limit of Al in a 1% (v/v) HNO(3) aqueous solution was 2 ng/l. The Al contents in LVP drug products obtained by this method were in the range of 1.16-4.33 microg/l and were less than 25 microg/l, that is, the regulation value of Food and Drug Administration (FDA). In order to trace the origin of Al in LVP drug products, each part of the LVP drug product, which is composed of three chambers, was investigated. However, a clear difference of the Al contents in each chamber was not observed. Furthermore, the Al contents in injection bags were quantified. Although the Al contents in injection bags were relatively high (in the range of 27.5-33.6 microg/g), dissolution of Al from the injection bags was not observed in the stability testing. From all of these results, it was concluded that the Al contents in the LVP drug products investigated originated in the amount of the Al in each raw material.