Study of reaction mechanism between piroxicam and tenoxicam drugs with iodate and N-bromosuccinamide oxidants and their microdetermination by spectrophotometric and potentiometric measurements

Piroxicam [Pir] and tenoxicam [Ten] are specified as nonsteriodal anti-inflammatory drugs. They are used in the symptomatic management of osteoarthritis, rheumatoid arthritis and in short term management of soft-tissue injury. Therefore, their reactions with oxidants, Iodate and N-bromosuccinamide [NBS] are suggested, discussed and used for microdeterminations of these essential biomedical drugs. A sensitive Spectrophotometric method has been suggested and used in comparison with a potentiometric one to follow these reactions mechanisms aiming to apply them in microdetermination of piroxicam [Pir] and tenoxicam [Ten]. No interference from excipients was observed in both techniques. The Spectrophotometric procedure was better than the potentiometric one, because of the sensitivity of the former to detect lower concentration ranges [50 to 1100 micro g ml[-1]] of the pure standard drugs and the detection of high concentration range [300 to 3980 micro g ml[-1]] by the latter. The high molar absorptivity [e = 0.25-0.29 x 10[3] L.mol[-1] cm[-1]] and Sandell sensitivity [1.2 - 13 micro g cm[-2]] refer to the high selectivity of the Spectrophotometric method. The between -day precision of the potentiometric procedure refers to the greater stability and good reliability of this procedure in high concentration [% recovery = 99 to 102%]. These procedures were applied for successful microdetermination of Pir and Ten in many pharmaceutical preparations, such as tablets and capsules. The values of SD [0.03 to 0.6 for five replicates] and RSD [0.6 to 1.2%] refer to reproducibility and precision of the applied procedures. The results of analyses of these drugs were compared with those obtained by the application of the official method using Ringbom, t-test and f-test. These results gave t- value of 2.776 and f-value of 6.31 at 95% confidence level. The obtained results also refer to the robustness of the proposed procedures

Spectrophotometric determination of levodopa, carbidopa and alpha-methyldopa

The dopamine derivatives participate in the regulation of a wide variety of physiological functions in human body and in medication life. A sensitive spectrophotometric method is developed for the determination of levodopa [LD], carbidopa [CD] and alpha methyldopa [MD]. It proposed on the bases of metal complex formation of these compounds with copper tetramine then coupling with 4-aminoantipyrine. The optimum conditions [pH, time, ratio and sequence of addition] are established. The method permits the determination of LD, CD and MD as a rectlinear relation in calibration curve over a concentration range 19.72 to 69.02, 13.79 to 63.34 and 31.24 to 98.94 micro g ml -1, respectively. The obtained data of SD [0.174 to 0.59], CV [0.68 to 1.16%] and correlation coefficient [0.995 to 0.999] reflect the reliability, reproducibility and accuracy of this procedure. The method is applicable to the assay of LD and MD in pharmaceutical drugs [Levocare and Aldomet respectively], and the results are in a good agreement with those obtained by the official method. The method was simple, rapid, reproducible and accurate to follow of medication of schizophrenic patient

Determination of paracetamol bromopotentio-metrically using silver amalgam and bromide ion-selective electrode

A study of the oxidation of paracetamol with bromine in acetate buffer media has been carried out using potentio bromometric techniques. The different variables such as ratio of the reactants, temperature, pH and time affecting the microdetermination of paracetamol were investigated. The optimum conditions obtained at [Br[2]] / [p-AAP] = 3.0, T = 303K, pH = 4.0 and t = 5 - 10 min, permit the quantitative determination of paracetamol in the concentration range of 0.113 to 13.61 mg using silver amalgam electrode or in the concentration range of 143 to 638 micro g ml[-1] using bromide ion-selective electrode. Application of the proposed techniques for rapid, simple and direct determination of paracetamol in ten different pharmaceutical preparations was demonstrated

Spectrophotometric determination of ampicillin, dicloxacillin, flucloxacillin and amoxicillin in pharmaceutical preparations using potassium periodate

Different Spectrophotometric methods were used for the determination of beta-lactam antibiotics using complex formation with Cu [II][1-6] and nickel [II][7]ions or titration against Cu [II] ions using ion-selective electrode [8,9]. Modified Spectrophotometric methods were developed for the determination of some important antibiotics including amoxicillin and ampicillin through charge transfer complexation reaction with chloranil [10,11] Amoxicillin and ampicillin were determined spectrophotometrically in pharmaceutical preparations using potassium iodate [12] picric and picramic acids [13] some nitro compounds [14] certain pi-acceptors[15] or with ammonium molybdite [16]. A Spectrophotometric method based on coupling of amoxicillin with different diazotized primary aromatic amines was developed [17]. Amoxicillin was determined spectrophotometrically in a binary mixture with dicloxacillin[18] or in the presence of dicloxacillin or flucloxacillin[19] Dicloxacillin [in urine] and flucloxacillin [in some pencillin derivatives] were determined using TLC spectrophotometry [20,21]. Two Spectrophotometric methods [22] [using N-bromos- uccinimide and N-chtorosuccinimide] or two colourimetric methods [23] [using sodium hypochlorite and 1-chlorobenzotriazole] were described for the determination of amoxicillin. Ampicillin was determined spectrophotometrically in tablets, capsules, powder and granules with the use of Na 3, 4 -naphthaquinone -1- sulphonate [24]or with l-fluoro-2,4-dinitrobenzene[22] reagents. HPLC methods [26,27] were used for the determination of amoxicillin in different pharmaceutical preparations

Spectrophotometric microdetermination of Mo [V] in pure and in steel using its thiocyanate complex interaction with chloroquine and pyrimethamine reagents

A rapid simple, accurate and sensitive spectrophotometric method was developed for the determination of a low concentration of molybdenum in pure and in complicated matrix. It is based on the extraction of the ion-pairs of Mo [V]-thiocyanate-chloroquine [1] and Mo [V]-thiocyanate-pyrimethamine [2], which are orange-red in color into dichloromethane from hydrochloric acid medium. The ion-pairs have an absorption maximum at gamma = 467 and 471 nm with molar absorptivities [epsilon] of 6.16 x 103 and 5.80 x 103 1/mol/cm for the Mo [V] ion- pairs [1] and [2]. The Sandell sensitivity was found to be 0.027 and 0.042 mug/cm2 for [1] and [2]. The effect of temperature, reagent concentration, time and diverse ions upon the absorbance of the ion- pairs was critically assessed. Beer's law was valid over a concentration range of 2.0-22.0 and 2.0-25.0 mug Mo/ml in case of [1] and [2]. Both reagents [chloroquine and pyrimethamine] were successfully applied for the determination of molybdenum in synthetic mixtures and molybdenum steels

Microdetermination of aminophenols and cresols via their reactions with bromine

The oxidation of aminophenols [APs] and cresols [CRs] with bromine in aqueous solution was investigated and used for microdetermination of these reductants under selected optimum conditions of pH, temperature, catalyst, time of contact of reactants and concentration ratios. The potentiometric-argentimetric titration of the librated bromide using silver amalgam electrode was found to be independent of the bromine concentration. Possible schemes, for the course of these reactions were simply suggested. The reactions were quantitative at concentration ranges of APs, 9.80 to 22.24 mg, percent recovery 98 to 103 percent and SD = 0.11 to 0.023 at [Br[2]]/[APs] ratio 2 to 4 and CRs in the concentration range 3.24 to 25.95 mg, percent recovery = 96.6 to 104.8 percent and SD = 0.19 to 0.03 at Br[2]]/[APs] ratio 2 to 6. The reaction between Br[2] and APs was fast in the order p-AP > o-AP > m-AP and with CRs it was in the order O-CR > m-CR > P-CR under the selected optimum conditions

Reaction kinetics of bromine and aminophenols

The kinetics of reactions of bromine and aminophenols has been studied at different temperatures. The overall order of the reactions determined from the half-life times was found to be 2.1, 2.12 and 2.4 for, 0-, m- and p-aminophenol, respectively. The thermodynamic parameters of activations were calculated and discussed. The final products of the reactions were investigated by elemental analysis, IR and mass spectra. Proposed schemes for these reactions were presented