Colorimetric assay of strychnine and brucine in nux vomica.

Two colorimetric methods are described for the estimation of strychnine and brucine in nux vomica. The first is a modification of the Karawya and Ghourab method for the determination of strychnine, in which the sensitivity of the color is increased by changing certain conditions of the method. The second was developed for the determination of brucine and is based on measuring the intensity of the violet color produced by treating brucine with nitric acid and methanolic stannous chloride. In the presence of large amounts of strychnine, brucine is isolated prior to colorimetric analysis by a quantitative thin layer chromatographic technique.     

Spectrophotometric determination of strychnine and brucine in liquid galenicals.

A rapid method is presented for determining strychnine and brucine in liquid galenicals. At pH 5.0, both strychnine and brucine are complexed with methyl orange. After treatment with 0.1N NaOH, the liberated alkaloids are determined spectrophotometrically, using the 2-wavelength method of analysis. The method has been successfully applied to the analysis of 4 batches of nux vomica tincture, nux vomica acid, and nux vomica alkaline mixtures. The method has a relative standard deviation of 0.52%.     

First derivative spectrophotometric determination of anhydrotetracyclines in tetracyclines

A rapid method is presented for detection and determination of anhydrotetracycline-HCl (ATC-HCl) and 4-epianhydrotetracycline-HCl (4-EATC-HCl) in tetracycline-HCl (TC-HCl). The method determines the 2 compounds as a sum, not individually. The first derivative absorption curve has a trough (D1) at 460 nm which is linearly related to concentration (1-10 mg/mL). ATC-HCl + 4-EATC-HCl content was determined in TC-HCl powder and capsules by the D1 and the compensation D1 spectrophotometric methods. The results were compared with those obtained using U.S. Pharmacopeia and British Pharmacopoeia methods.     

High-performance liquid chromatographic determination of strychnine in grain baits.l.

A simple and rapid high-performance liquid chromatographic procedure is described for the determination of strychnine. Grain baits containing strychnine alkaloid are ground, mixed, and extracted by shaking with chloroform. Without further cleanup, extract filtrates are injected directly into a liquid chromatograph. Chromatography is complete within 7 min and peak heights are used for quantitation. Separations were made on a 30 cm times 4 mm id stainless steel column packed with mu Porasil (8-12 mum silica). The eluting solvent was methanol-chloroform (10+90) at a flow rate of 2.0 ml/min. Recovery of spiked samples ranged from 91.5 to 95.2%. Confirmation of strychnine from a commercial sample was made by high resolution mass spectrometry with mass agreement to 1.2 ppm.     

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.     

Liquid chromatographic determination of strychnine in stomach contents

A chloroform extract of stomach contents at basic pH is concentrated and then extracted with 0.1 M phosphoric acid. The acid extract is chromatographed on a 10 cm reverse phase column, using 0.005 M phosphate buffer (pH 3.0)-acetonitrile-tetrahydrofuran (750 + 135 + 115) containing 0.01 M octanesulfonic acid at a flow rate of 1.0 mL/min for elution. Strychnine eluted in 7.3 min. Recoveries from spiked stomach contents averaged 92%. The method can be used without modification for other alkaloids.     

Gas-liquid chromatographic determination of strychnine in grain baits.

A simple and rapid gas-liquid chromatographic procedure, using a 6' times 1/4' glass column packed with 5% SE-30 on Chromosorb W (DMCS) and a flame ionization detector, is described. Grain baits containing strychnine alkaloid are ground, mixed, and extracted by shaking with chloroform containing an internal standard, 1,3,5-triphenylbenzene. Without further cleanup, extract filtrates are injected directly into a gas chromatograph. Peak height ratios are used for quantitation of strychnine. The analysis of commercial samples shows that the method compares well with a commonly employed ultraviolet spectrophotometric method; good precision, with recoveries ranging from 89.9 to 91.7%, is obtained in the analysis of prepared samples. The method is sensitive to 2 mug strychnine.     

Atomic absorption spectrophotometric determination of cobalt in foods

A method is described for the determination of cobalt in foods. After wet digestion, iron in the sample is removed by liquid-liquid extraction, and cobalt is isolated and extracted. Final determination is done by flame atomic absorption spectrophotometry. Analysis of NBS reference materials by this procedure gives results in close agreement with certified values. The limit of quantitation is 4.3 ng/mL. Recovery studies and analysis of standard materials show that this method is reliable.     

Atomic absorption spectrophotometric determination of chromium in foods

A method is reported for determination of chromium in foodstuffs. Organic matter is digested with nitric acid, followed by oxidation to Cr(VI) and extraction with methyl isobutyl ketone (MIBK) after HCl addition. Chromium determinations are performed by flame absorption spectroscopy. Absence of interferences is verified and recovery tests are performed on food samples. Quantitation limit (3.8 ng/mL), accuracy (NBS Standard Reference Material 1,573 Tomato Leaves, 4,500 +/- 500 ng/g, found 3,860 +/- 409 ng/g), and precision (CV for vegetable matrix = 9.05%, CV for animal matrix = 14.95%) of the procedure are evaluated.     

Improved spectrophotometric determination of cyclopiazonic acid in poultry feed and corn

An improved visible spectrophotometric method has been developed for cyclopiazonic acid in poultry feed and corn. The method is based on the reaction of cyclopiazonic acid with Ehrlich reagent and detection at 580 nm. Reaction conditions were optimized with respect to reaction and measurement times and acid and Ehrlich reagent concentrations. Calibration curves were linear from 1 to 20 micrograms cyclopiazonic acid in 3 mL Ehrlich reagent, with a lower detection limit of 0.08 mg/kg for 50 g samples of poultry feed and corn. Recoveries from 50 g samples of poultry feed spiked with cyclopiazonic ranging from 0.16 to 1.20 mg/kg averaged 93.8%. Moldy corn and poultry feed samples analyzed by this method contained between 1 and 4 mg/kg cyclopiazonic acid.     

Liquid chromatographic and ultraviolet spectrophotometric determination of bevantolol and hydrochlorothiazide in feeds

Separate assay methods have been developed for the 2 components of an 80 + 20 drug blend of bevantolol and hydrochlorothiazide (HCT) in admixtures with animal feed. Drug/diet admixtures are extracted with methanol for reverse phase ion-pair liquid chromatographic (LC) assay of bevantolol, and with acetonitrile for ultraviolet spectrophotometric assay of HCT. Bevantolol, a cardioselective beta blocker, is separated from soluble feed components with an RP-18 column, using methanol-water-acetic acid (60 + 40 + 1) containing 0. 005M octane-sulfonic acid, sodium salt, as ion-pairing reagent. HCT is determined spectrophotometrically in acetonitrile extracts, using a suitable blank extract as reference. Average recovery of HCT from an admixture of 0.5 mg blend/g diet is 94.5% +/- 4.3 RSD and at 2.0 mg/g, 101.5% +/- 3.5 RSD. Bevantolol recovery from the same admixtures is 101.8% +/- 2.7 RSD and 99.0% +/- 3.5 RSD, respectively, using the method as described.     

Fluorometric and spectrophotometric determination of pirbuterol hydrochloride in authentic and dosage forms

Pirbuterol hydrochloride has been assayed in alkaline medium by using a fluorometric method to measure fluorescence intensity at 372 nm with excitation at 310 nm and by the delta A method at 242 nm. The linearity ranges are 0.5-4 micrograms/mL and 10-50 micrograms/mL, respectively. An authentic pirbuterol HCl sample was analyzed by nonaqueous potentiometric titration using 0.1N perchloric acid, and the results were compared with those for fluorometric and delta A methods. The mean percent recoveries for the authentic sample were 98.72 +/- 1.13 and 99.24 +/- 0.85, respectively. When applied to commercial capsules containing 10 mg and 15 mg each, the fluorometric method gave mean percent recoveries of 101.11 +/- 1.05 and 98.12 +/- 0.93; the delta A method gave mean percent recoveries of 100.57 +/- 0.83 and 97.80 +/- 0.75, respectively.     

Simple spectrophotometric method for determination of phosphine residues in wheat

A method has been developed for determination of phosphine residues in wheat, based on the reaction of phosphine with silver nitrate in aqueous solution to form an egg-yellow chromophore with an absorption maximum at 400 nm. At this wavelength, there is a linear relationship between absorbance and concentration of phosphine in the range 10-100 ng/mL. Phosphine-fumigated wheat is soaked in a known volume of AgNO3 solution, and the absorbance of the filtrate is read against a blank at 400 nm. The method is sensitive, with lower detection and estimation limits of 0.008 and 0.01 micrograms PH3, respectively. Recovery of added phosphine from a closed system was 85-100%. Accuracy for this method has been compared with that for the gas chromatographic method.     

Ultraviolet spectrophotometric determination of benzoic acid in soy sauce.

Proteins and other interfering substances are precipitated from soy sauce, using sodium tungstate under acidic conditions. After centrifugation, the supernate is successively extracted with ethyl ether to isolate the benzoic acid in the organic solvent. The ethyl ether extract is washed with dilute HCl. Benzoic acid is then quantitatively determined by ultraviolet spectrophotometry. Recovery of sodium benzoate added to soy sauce ranged from 94 to 104%.     

On routine colorimetric determination of trace nitrates,by brucine,in the presence of chloride

A colorimetric method was developed for the determination of trace nitrates in solutions containing up to 50 g 1^?1 of sodium chloride. Beer's law applies, in such solutions for concentrations of up to 1 mg of NaNO₃ per liter. Effects of sodium chloride concentration and time on the development of color were quantitatively evaluated with an overall error of about 4%. Temperature effects on solutions analyzed were found to be a major cause of inconsistencies in this otherwise satisfactory method.     

Simple and rapid spectrophotometric method for determination of adrenaline and isoprenaline

A simple, rapid, and specific method for determination of adrenaline bitartrate and isoprenaline sulfate was developed. The method is based on the oxidation reaction in aqueous solution of either adrenaline bitartrate or isoprenaline sulfate in the presence of silver oxide to give a red aminochrome measurable at 490 nm. The color is stable for 2 h. Beer's law is valid within a concentration range of 5-80 micrograms/mL for each drug. All variables were studied to optimize the reaction conditions. The method is specific for catecholamine drugs having a secondary amine in the side chain. Other catecholamines such as orciprenaline and noradrenaline do not interfere, and no interference was observed in the presence of common pharmaceutical adjuvants. Interference due to sodium metabisulfite and sodium chloride was circumvented. The validity of the method was tested by analyzing adrenaline injections and isoprenaline tablets. Good recoveries were obtained for these preparations. The results were comparable to those obtained by official procedures. The proposed method is also recommended as a stability indicating assay for oxidative degradation of both drugs.