An explosively driven high-power microwave pulsed power system

The increased popularity of high power microwave systems and the various sources to drive them is the motivation behind the work to be presented. A stand-alone, self-contained explosively driven high power microwave pulsed power system has been designed, built, and tested at Texas Tech University's Center for Pulsed Power and Power Electronics. The system integrates four different sub-units that are composed of a battery driven prime power source utilizing capacitive energy storage, a dual stage helical flux compression generator as the main energy amplification device, an integrated power conditioning system with inductive energy storage including a fast opening electro-explosive switch, and a triode reflex geometry virtual cathode oscillator as the microwave radiating source. This system has displayed a measured electrical source power level of over 5 GW and peak radiated microwaves of about 200 MW. It is contained within a 15 cm diameter housing and measures 2 m in length, giving a housing volume of slightly less than 39 l. The system and its sub-components have been extensively studied, both as integrated and individual units, to further expand on components behavior and operation physics. This report will serve as a detailed design overview of each of the four subcomponents and provide detailed analysis of the overall system performance and benchmarks.

A stability-indicating first-derivative spectrophotometric assay of acetazolamide and its use in dissolution and kinetic studies

A simple, rapid, stability-indicating first-derivative spectrophotometric assay procedure for the determination of the degradation products of acetazolamide is described. The dissolution and kinetics of drug degradation in aqueous buffered solutions were studied using the proposed method. Acetazolamide solution exhibited optimum stability at pH 4. The influences of temperature and sonic energy on the degradation of acetazolamide in 0.01 M NaOH solution were also studied. The results showed first-order reaction kinetics, with a degradation rate constant and degradation half-life of 3.51 x 10(-3) day-1 and 8.23 days, respectively.

Spectrophotometric determination of cimetidine in the presence of its acid-induced degradation products

Cimetidine has been determined in the presence of its acid-induced degradation products using a second derivative (D2-) spectrophotometric method (method I) or a colorimetric method (method II). The former is based on D2-value measurement at 216 nm, whilst the latter depends on charge-transfer complexation with dichlorophenol-indophenol. The two methods are proved to be stability indicating, since plots of log C% versus time were linear. The application to cimetidine determination in tablets and ampoules gave good results.

Determination of isothipendyl or dimethothiazine with their sulphoxides using third- and fourth-derivatives spectroscopy on a diode-array spectrophotometer

Third- and fourth-derivative spectrophotometry (3D + 4D), with a diode-array spectrophotometer, has been used for the assay of mixtures of each of isothipendyl hydrochloride (I) and its sulphoxide (II) or dimethothiazine mesylate (III) and its sulphoxide (IV). The parent compounds have been determined by measuring the 3D at 256 nm, 246-256 nm and 256-264 nm and 4D at 250 nm for (I) and 3D at 255 nm or 283 nm and 4D at 257 nm for (III). The sulphoxides have been assayed by measuring the 3D at 285-290 nm and 4D 285-290 nm for (II) and 3D at 305 nm and 4D at 303-310 nm for (IV). Beer's law is obeyed and the detection limits for the proposed 3D and 4D has been calculated. The recovery of these drugs and their sulphoxides in laboratory-made mixture and dosage forms has been reported.

Derivative spectrophotometric determination of clotrimazole in single formulations and in combination with other drugs

First (D1) and second (D2) derivative spectrophotometric methods are presented for the determination of clotrimazole after its acid hydrolysis. Mixtures of clotrimazole with azidamfenicol and dexamethasone have been assayed using D2 measurement at 302 nm after acid hydrolysis for clotrimazole, D1 measurement at 288 nm for azidamfenicol, and D1 measurement at 436 nm after reaction with phenylhydrazinium sulfate for dexamethasone. Reproducible results with relative standard deviations of less than 2% are obtained. The proposed method has been successfully applied to the analysis of creams, topical solutions, and vaginal tablets.

Second derivative spectrophotometric determination of acetaminophen and phenacetin in presence of their degradation products

A rapid and accurate method for determining acetaminophen and phenacetin in presence of their degradation products is presented. Solutions of these drugs in 0.1N HCl were analyzed by measuring their second derivative spectral response at 295 nm where the degradation products do not interfere. The mean percent recoveries for mixtures of acetaminophen and/or phenacetin with the corresponding degradation products were 100.2 +/- 0.6 and 100.6 +/- 1.1, respectively. The method can be used for assessing the stability of the 2 drugs. The proposed method is also applied to the determination of acetaminophen in tablets and syrups.

Determination of ethinyloestradiol in the presence of norethisterone by derivative-difference spectrophotometry

A simple and direct method for the determination of ethinyloestradiol as a minor component in the presence of norethisterone and in oral contraceptive tablets is presented. The method is based on measuring the signal intensity, d delta A/d lambda and d2 delta A/d lambda 2, of the generated first and second derivative spectra of the delta-absorbance curves obtained by measuring solutions in methanol and methanol-sodium hydroxide at certain wavelengths. The method has been applied to the determination of ethinyloestradiol in oral contraceptive tablets, with a coefficient of variation of less than 2%.

Detection of some alkaloids on thin layer chromatograms using pi-acceptors

The reactions of chloranil, fluoranil, 2,5 dichlorobenzoquinone and chloranilic acid with some alkaloids on thin layer chromatograms were examined with a view to determine their suitability as visualizing agents. Chloranil and 2,5 dichlorobenzoquinone (each 0.5% w/v in dioxan) were found to be most suitable as they gave coloured reaction products with many alkaloids.

Bromination methods for determination of phenylephrine hydrochloride in nose drops, salicylamide in tablets, and tetracycline hydrochloride in capsules

Two methods, kinetic and titrimetric, based on an electrophilic substitution reaction with bromine, are described for the assay of phenylephrine hydrochloride in nose drops, salicylamide in tablets, and tetracycline hydrochloride in capsules. The kinetic method depends on the linear relationship between concentration of the drug (microgram/mL) and time (s) for nuclear monobromination, indicated by bleaching of the methyl orange acid color. The titrimetric method is based on addition of excess of bromate-bromide with subsequent determination of excess bromine by an iodide-thiosulfate procedure. This method is also used to count the number of bromine atoms necessary for the electrophilic substitution reaction. Preservatives or tablet-capsule bases do not interfere in either method. Recoveries of drugs added to laboratory-prepared samples were good. As indicated by the F-test, the methods are equally reproducible.

Utility of chloranil in assay of naphazoline, clemizole, penicillin G sodium, and piperazine

A simple and sensitive spectrophotometric method is described for the assay of naphazoline, clemizole, penicillin G sodium, and piperazine. The method was based on the formation of a charge transfer complex between these drugs as n-donors and chloranil, the pi-acceptor. Conformity to Beer's law enabled the assay of dosage forms of these drugs. Compared with official methods, the results obtained were of equal accuracy. A more detailed investigation of th naphazoline-chloranil complex was made with respect to its composition, association constant, and free energy change.

Colorimetric acetaminophen determination in pharmaceutical formulations

Different approaches for the colorimetric determination of acetaminophen, based on its coupling with diazotized o-nitroaniline, are described. Copper(II) chelation with the coupled compound makes the method highly selective. Sensitivity is increased when the acetaminophen assay is carried out indirectly through the determination of the chelate's copper content. Optimum conditions for performing the different approaches are described. The stoichiometric balance for the reactants in the coupled compound and chelate is determined. The degree of dissociation and the instability constant are computed. The rectilinear relationship between the absorbance of the different products and the concentration of acetaminophen allows for its determination in different pharmaceutical formulations. Compared with the official method, the proposed methods give more accurate results.

Spectrophotometric determination of tolbutamide, thiamine hydrochloride, and pyridoxine hydrochloride in combination products

The first derivative curve is used for tolbutamide determination in unit-dose tablets and in combination products. The absorbance contribution from tablet excipient and coexisting components, thiamine and pyridoxine, is thereby nullified. The interference from tolbutamide during thiamine and pyridoxine determination is eliminated by solvent extraction and pH-induced differential spectrophotometry. Thiamine is measured at the isosbestic point of pyridoxine. The latter is determined by the differential absorbance measurement at two wavelengths with the consequent computation of the delta absorbance value.

Spectrophotometric determination of acetaminophen in tablets, sirups, and suppositories

A differential spectrophotometric method and Glenn's method of orthogonal function are described for the assay of acetaminophen in tablets, sirups, and suppositories. Interference from excipients in the formulations is thereby avoided. Accuracy of the analyses is greater with the proposed methods than with the British Pharmacopoeia method.

Spectrophotometric determination of tolbutamide in tablets

Two spectrophotometric methods, Glenn's method of orthogonal function and the basic dye method, are described for determing tolbutamide in tablets without interference from the tablet excipients. In Glenn's method, the absorbance of tolbutamide in 95% ethanol is measured in the vicinity of 250--270 nm at 4 nm intervals and the p2 coefficient is calculated. The coefficient is linearly related to concentration within a range of 0.1--0.4 mg/mL. Tolbutamide gives a complex of a ratio 1:1 with basic dye Brilliant Cresyl Blue (BCB) or Safranin T (ST). The complex is easily extracted with chloroform. The absorbance of the chloroform extract is measured against either a blank or reference experiment. The latter is obtained by using a specific concentration of tolbutamide: 0.4 mg/mL in tolbutamide-BCB or 0.024 mg/mL in tolbutamide-ST. The ST complex method is more sensitive compared with the other methods. When the t-test is applied, the results of the proposed methods are more accurate than those of the traditional ultraviolet spectrophotometric method.

Spectrophotometric determination of theophylline formulations

Minophylline (theophylline ethanoate of piperazine) and aminophylline (theophylline ethylenediamine) were determined spectrophotometrically in dosage forms without interference from excipients and/or preservatives. A mixture of minophylline, in about 30-fold concentration, with phenobarbital was assayed for both components with good accuracy and high reproducibility.

pH-induced difference spectrophotometric assay of acetazolamide, hydrochlorothiazide, and furosemide

On the basis of pH-induced spectral changes for acetazolamide, hydrochlorothiazide, and furosemide, 3 different spectrophotometric methods are described. The methods were successfully applied to the assay of these drugs in different pharmaceutical formulations (tablets and ampoules). The accuracy of the analysis is increased by using the suggested methods as compared with conventional spectrophotometry.