Analytical applications of photochemical reduction of Azur B by EDTA-iodide determination.

A kinetic study of the photochemical reaction of Azur B and EDTA (in the absence of oxygen) has been made in connection with development of a new kinetic method for iodide. The reaction is first-order with respect to the dye, EDTA and absorbed light-intensity. The rate of photoreduction is strongly pH-dependent, and maximal at about pH 6.8. The photoreduction involves a long-lived excited state of the dye and is dramatically retarded by small amounts of iodide. A tentative mechanism is proposed, and the experimental conditions have been optimized. The variable time method appear to be the most suitable. A detection limit of 1.0 mug/ml and a coefficient of variation of about 3% can be achieved. Chloride and bromide do not interfere at levels below 100-fold mole ratio to iodide. Metal ions do not interfere if enough excess of EDTA is used. Coloured species may interfere at high concentration (filter effect).

Determination of acriflavine, rivanol, Acridine Orange, Acridine Yellow and proflavine by a catalytic photokinetic method.

A fast and sensitive photokinetic method for the determination of acriflavine, rivanol, Acridine Orange, Acridine Yellow and proflavine is described. It is based on the rate of photoreduction of methylviologen in the presence of EDTA, sensitized by these diaminoacridines. The rate is monitored spectrophotometrically by the formation of ferroin, which is generated after reduction of iron(III) by the methylviologen cation radical in the presence of 1,10-phenanthroline. The method has been successfully applied to the determination of acriflavine and rivanol in pharmaceuticals.

Flow injection fluorimetric determination of thiourea.

A flow injection configuration for the fluorimetric determination of thiourea is proposed. The procedure is based on the rapid oxidation of thiourea by thallium(III) with concomitant formation of fluorescent thallium(I). Linear calibration graphs were obtained between 5 x 10(-7) and 1 x 10(-5)M, with a sampling rate of 90 samples/hr. The usefulness of the method was tested in the determination of thiourea in fruit juices and fruit peels.

Flow injection fluorimetric determination of thiamine and copper based on the formation of thiochrome.

The reaction, involving the oxidation of thiamine by copper(II) in basic solutions to fluorescent thiochrome, has been adapted to the determination of thiamine by flow-injection analysis. Linear calibration graphs are obtained between 0.30 and 6.02 mug/ml with a sampling rate of 50 samples/hr and a relative standard deviation of 0.53%. This reaction has also been adapted to the determination of copper(II) over the range 0.5-5.0 mug/ml. The applicability of both methods for determination of thiamine and copper is demonstrated by investigating the effect of potential interferences and by the analysis of real samples (pharmaceuticals for thiamine and ores and alloys for copper).

Application of photochemical inhibition in flow injection systems: Determination of epinephrine and L-dopa.

An automated procedure for the photochemical determination of epinephrine and L-dopa has been developed. It is based on the strong inhibition by these catecholamines on the photochemical reaction between phloxin and ethylenediaminetetraacetic. The proposed flow-injection method allows the fluorimetric determination of epinephrine in the range 1.9-26.4 mug/ml and of L-dopa in the range of 1.5-12.7 mug/ml, with a sampling frequency of 35 samples/hr. The method was applied successfully to the determination of body catecholamines in pharmaceutical preparations.

Flow-injection successive determination of cysteine and cystine in pharmaceutical preparations.

A flow-injection configuration is proposed for the individual determination of cysteine and cystine and for the mixtures of both analytes. The procedure is based on the inhibitory effect of cysteine on the oxidation of thiamine to thiochrome by mercury(II). Linear calibration graphs were obtained between 1.0 x 10(-5) and 1.0 x 10(-4)M, with a sampling rate of 22 samples/hr and relative standard deviation of 1.14%. The inclusion of a selecting valve in the configuration, to pump water or hydroxylamine, allows the successive determination of these two analytes. The applicability of the method to the determination of cysteine and cystine in pharmaceutical preparations was demonstrated by investigating the effect of potential interferences and by the analysis of commercial preparations.

Flow-injection extraction-spectrophotometric determination of imipramine in pharmaceuticals with methyl orange.

Imipramine in aqueous solution is extracted into 1,2-dichloroethane as its ion-pair with Methyl Orange in an unsegmented flow system and quantified spectrophotometrically. A linear calibration graph was obtained between 0.79 and 25.3 mug/ml of imipramine. Up to 45 samples/hr can be processed with a RSD of 0.88-1.6%. The method was satisfactorily applied to the determination of imipramine in pharmaceutical preparations.

Flow-injection fluorimetric determination of nabam and metham.

A simple and sensitive flow-injection fluorimetric method was developed to determine nabam or metham in water and cereal samples. The procedure is based on the oxidation of these pesticides by thallium(III) with the concomitant formation of fluorescent thallium(I). Lineal calibration graphs were obtained between 0.25 and 2.56 muml(-1) for nabam, and between 0.26 and 2.65 mug ml(-1) for metham. The sampling rate was 80 samples h(-1). The method was satisfactorily applied to the direct analysis of water, wheat, barley and oat samples spiked with nabam or metham.

Flow-injection fluorimetric determination of vitamin K(1) based on a photochemical reaction.

The sensitizing effect of vitamin K(1) on the photo-oxidation of glucose has been used for the determination of the vitamin. The hydrogen peroxide formed in the photochemical reaction reacts with Fe(II) to yield hydroxylradical and this radical is scavenged by benzoic acid to form the fluorescent hydroxybenzoic acids, which are analysed by fluorescence detection. This analytical scheme was adapted to a flow-injection system, which permits the determination of vitamin K(1) between 1x10(-6) and 1x10(-4) M with a throughput of 20 samples h(-1) and relative standard deviation between 0.2 and 1%. The applicability of the method was demonstrated by determining vitamin K(1) in pharmaceutical preparations and vegetables.

Flow-injection fluorimetric determination of trimeprazine and trifluoperazine in pharmaceutical preparations.

A flow-injection configuration for the fluorimetric determination of trimeprazine and trifluoperazine is proposed. The procedure is based on oxidation of the drugs by cerium(IV). The fluorescence of cerium(III) formed in the oxidation of trimeprazine or trifluoperazine is monitored. Lineal calibration graphs were obtained between 2 x 10(-7) and 1 x 10(-5)M for both trimeprazine and trifluoperazine with a sampling rate of 60 samples/hr. The relative standard deviations were over the ranges 0.78-1.16 and 0.84-0.97% for trimeprazine and trifluoperazine respectively. The applicability of the method to determination of trimeprazine and trifluoperazine was demonstrated by investigating the effect of potential interferences and by analysis of commercial pharmaceutical preparations.

Automatic extraction-spectrophotometric method for the determination of ambroxol in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of ambroxol was carried out by liquid-liquid extraction using Bromothymol Blue with a flow-injection system. The determination of ambroxol in the range 8 x 10(-6)-4 x 10(-4) M was possible with a sampling frequency of 40 samples h(-1). The method was satisfactorily applied to the determination of ambroxol in pharmaceutical preparations.

Simultaneous determination of propranolol and pindolol by synchronous spectrofluorimetry.

The simultaneous determination of propranolol and pindolol using synchronous fluorescence spectrometric techniques is described. The method involves measuring the natural fluorescence of these drugs in a 50% (v/v) ethanol-water medium using zero and first derivative synchronous spectrofluorimetry. Under the optimum conditions, the linear determination ranges of propanolol and pindolol are ca. 0.02-1.0 and 0.04-1.2 mug ml(-1), respectively. The results showed that propranolol and pindolol can be determined simultaneously when the concentration ratio of propranolol to pindolol varies from 1:100 to 50:1 in the mixed sample. The method has been satisfactorily applied to the determination of propranolol and pindolol in urine samples and propranolol in pharmaceutical preparations.

Flow-injection determination of Novalgin using amperometric detection at a glassy carbon electrode.

An electroanalytical study of the oxidation of Novalgin (dipyrone) at a glassy carbon electrode in aqueous solution has been carried out. A flow-injection method with amperometric detection based on this oxidation process is also described. The influence of flow rate, coil length and injection volume on the sensitivity of the method was established. The calibration graph was linear within the range 3 x 10(-6)-3 x 10(-5) M in an ammonia buffer solution (pH 9) as a potential of 0.4 V versus an Ag/AgCl reference electrode. The sampling rate was 54 samples h-1. The applicability of the method to the determination of Novalgin in pharmaceutical preparations was demonstrated by investigating the effect of potential sources of interference and by analysing commercial preparations.

Flow-injection extraction-spectrophotometric determination of bromhexine with orange IV.

An automatic flow-injection photometric method for the determination of bromhexine is proposed. The drug was determined by formation of an ion-pair with orange IV, extraction into 1,2-dichloroethane and measurement of the absorbance at 412 nm of the organic phase. A linear calibration graph was obtained at concentrations of 5 x 10(-6)-1.6 x 10(-4) M of bromhexine. Up to 40 samples h-1 can be processed with an RSD of 0.32-0.88%. The method was applied to the determination of bromhexine in blood serum and a pharmaceutical preparation.

Fluorimetric determination of chloroxine using manual and flow-injection methods.

A reliable and highly sensitive method is described for the determination of chloroxine in pharmaceutical preparations. It involves the formation of a complex between chloroxine and aluminum(III) in a micellar medium. The complex is a very fluorescent species, and there is a linear relationship between chloroxine concentration and fluorescence intensity over the range 2.0 x 10(-8)-5.1 x 10(-5) mol l-1. The limit of detection is 5 x 10(-9) mol l-1. The method can be easily adapted to a flow system using a three-channel manifold, the peak height being proportional to the chloroxine concentration over the range 5.6 x 10(-7)-5.6 x 10(-5) mol l-1. Manual and flow-injection procedures permit the determination of chloroxine in the presence of chlorquinaldol, and have been successfully applied to the determination of chloroxine in pharmaceutical preparations.

Selective determination of naproxen in the presence of nonsteroidal anti-inflammatory drugs in serum and urine samples using room temperature liquid phosphorimetry.

A very simple, rapid and highly sensitive method is described for determining naproxen in serum and urine. This method is based on room temperature phosphorescence of naproxen in sodium dodecylsulphate micelles, with thallium(I) providing the external heavy atom and sodium sulphite acting as the oxygen scavenger. Under the optimum and experimental conditions, the range of application is 0.09-4.5 micrograms ml-1 and the limit of detection is 0.03 micrograms ml-1. The most relevant characteristic of this method is its great selectivity, e.g. naproxen can be determined in the presence of other nonsteroidal anti-inflammatory drugs (NSAIDs). The clinical applicability of this procedure has been tested, analysing naproxen in serum and urine samples. The analytical recoveries and inter- and intra assay precision data obtained demonstrate the usefulness of this procedure when used with very complex samples.

Flow-injection extraction-spectrophotometric method for the determination of chlorhexidine in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of chlorhexidine was carried out by liquid-liquid extraction using bromophenol blue with a flow system. The determination of chlorhexidine in the range of 1 x 10(-4) to 1 x 10(-5) M was possible with a sampling frequency of 40 samples per hour. The method was satisfactorily applied to the determination of chlorhexidine in pharmaceutical preparations.

A simple photokinetic method for the determination of nitroprusside in biological and pharmaceutical samples.

A simple method has been developed for the determination of nitroprusside in human serum and pharmaceutical preparations. The new method is based on the strong inhibitory effect of nitroprusside on the photochemical reduction of phloxin by ethylenediaminetetra-acetic acid. The rate measurements are accomplished very simply by measuring the time needed for the absorbance to be reduced to 1/10th of its initial value. Optimal conditions for the determination of nitroprusside at concentrations of 15-200 ng ml-1 are described.

Flow extraction spectrophotometric method for the determination of diclofenac sodium in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of diclofenac was carried out by liquid-liquid extraction using acridine yellow with a flow system. The determination of diclofenac sodium in the range of 3-80 micrograms ml-1 was possible with a sampling frequency of 40 samples h-1. The method was satisfactorily applied to the determination of diclofenac in pharmaceutical preparations.

Flow-injection extraction-spectrophotometric method for the determination of ranitidine in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of ranitidine was carried out by liquid-liquid extraction using bromothymol blue with a flow system. The determination of ranitidine in the range of 1 x 10(-5) - 1 x 10(-4) mol l(-1) was possible with a sampling frequency of 40 samples h(-1). The method was satisfactorily applied to the determination of ranitidine in pharmaceutical preparations and the recovery was quantitative and no interferences from excipients were observed.