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Results for “Spectrophotometry, Ultraviolet”

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At least 217 records · Page 12Linked to original sources

PubMed2000

Interaction of 6-p-toluidinylnaphthalene-2-sulphonate with beta-cyclodextrin.

The present study examines the complexation of beta-cyclodextrin (beta-CD) with 6-p-toluidinylnaphthalene-2-sulfonate (TNS), a fluorescent probe for exploring hydrophobic regions of several biological substances. The complexation was monitored in aqueous solution by ultraviolet spectrophotometry. At first, the stoichiometry of the formed complex was examined by applying the continuous variation (Job plot) method. Next, the kinetic of the complex formation as well as the determination of the stability constant were calculated by monitoring the spectrophotometric properties of TNS in the presence of increasing concentrations of beta-CD applying both linear and nonlinear models. The results suggested that TNS forms a stable complex with beta-CD with a stability constant of 1109 M(-1) and 1:1 molar ratio, at least at the examined concentrations.

Cyclodextrins↗

PubMed2001

Spectrophotometric determination of benazepril hydrochloride and hydrochlorothiazide in binary mixture using second derivative, second derivative of the ratio spectra and chemometric methods.

Different spectrophotometric methods are presented for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide in pharmaceutical tablets. The first method depends on second derivative (2D) ultraviolet spectrophotometry, with zero crossing and peak to base measurement. The second derivative amplitudes at 214.8 and 227.4 nm were selected for the assay of benazepril hydrochloride and hydrochlorothiazide, respectively. The second method depends on second derivative of the ratio spectra by measurement of the amplitudes at 241.2 and 273.2 nm for benazepril hydrochloride and hydrochlorothiazide, respectively. Chemometric methods, classical least squares and principal component regression, were applied to analyze the mixture. Both the chemometric methods were applied to the zero and first order spectra of the mixture. The proposed methods were successfully applied for the determination of the two drugs in laboratory prepared mixtures and in commercial tablets.

Antihypertensive Agents↗

PubMed2001

Spectrophotometric and HPTLC-densitometric determination of lisinopril and hydrochlorothiazide in binary mixtures.

Different spectrophotometric and HPTLC-densitometric methods are presented for the simultaneous determination of lisinopril and hydrochlorothiazide in pharmaceutical tablets. The spectrophotometric methods include third derivative (3D) ultraviolet spectrophotometry with zero crossing measurement at 217.4 and 233.4 nm, second derivative of the ratio spectra with measurement at 214.3 and 228.0 nm; both classical least squares and principal component regression were applied to the UV absorption and first derivative spectra of the mixture. The HPTLC method was based on separation of both drugs followed by densitometric measurements of their spots at 210 and 275 nm for lisinopril and hydrochlorothiazide, respectively. The separation was carried out on Merck HPTLC aluminum plates of silica gel 60 F254, using chloroform-ethylacetate-acetic acid (10:3:2 by vol.) as mobile phase. The linear and second order polynomial were used for the regression equation of lisinopril and hydrochlorothiazide, respectively.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2001

Spectrophotometric determination of trifluoperazine HCl and isopropamide iodide in binary mixture using second derivative and second derivative of the ratio spectra methods.

Two methods are presented for the simultaneous determination of trifluoperazine hydrochloride and isopropamide iodide in binary mixture. The first method depends on second derivative ((2)D) ultraviolet spectrophotometry, with zero crossing and peak to base measurement. The second derivative amplitudes at 270.4 and 230.2 nm were selected for the assay of trifluoperazine hydrochloride and isopropamide iodide, respectively. The second method depends on second derivative of the ratio spectra by division of the absorption spectrum of the binary mixture by a normalized spectrum of one of the components and then calculating the second derivative of the ratio spectrum. The second derivative of the ratio amplitudes at 257 and 228 nm were selected for the determination of trifluoperazine hydrochloride and isopropamide iodide, respectively. The two proposed methods were successfully applied to the determination of the two drugs in laboratory prepared mixtures and in commercial tablets.

Chemistry, Pharmaceutical↗

PubMed2003

Simultaneous determination of moexipril hydrochloride and hydrochlorothiazide in tablets by derivative spectrophotometric and high-performance liquid chromatographic methods.

Two new simple and selective assay methods have been presented for the binary mixtures of moexipril hydrochloride (MOEX) and hydrochlorothiazide (HCTZ) in pharmaceutical formulations. The first method depends on second-derivative ultraviolet spectrophotometry with zero-crossing measurements at 215 and 234 nm for MOEX and HCTZ, respectively. The assay was linear over the concentration ranges 1.0-11.0 microg ml(-1) for MOEX and 0.5-9.0 microg ml(-1) for HCTZ. The determination limits for MOEX and HCTZ were found to be 1.0 and 0.5 microg ml(-1), respectively; while the detection limits were 0.2 microg ml(-1) for MOEX and 0.1 microg ml(-1) for HCTZ. The second method was based on isocratic reversed-phase liquid chromatography by using a mobile phase acetonitrile-20 mM phosphate buffer (pH 4.0) (50:50, v/v). Lisinopril was used as an internal standard (IS) and the substances were detected at 212 nm. The linearity range for both drugs was 0.5-12.0 microg ml(-1). The determination and detection limits were found to be 0.100 and 0.010 microg ml(-1) for MOEX and 0.025 and 0.005 microg ml(-1) for HCTZ, respectively. The proposed methods were successfully applied to the determination of these drugs in synthetic mixtures and commercially available tablets with a high percentage recovery, good accuracy and precision.

Chromatography, High Pressure Liquid↗

PubMed1997

Analysis of nifedipine-acebutolol hydrochloride binary combination in tablets using UV-derivative spectroscopy, capillary gas chromatography and high performance liquid chromatography.

Three methods are described for the simultaneous determination of nifedipine and acebutolol hydrochloride in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with peak-to-base and zero-crossing measurements methods. The first derivative amplitudes at 400 and 352 nm were selected for the assay of nifedipine and acebutolol hydrochloride, respectively. Calibration graphs follow Beer's law in the range of 4-12 and 44-132 micrograms ml-1 and the linearity was satisfactory (r = 0.999) for nifedipine and acebutolol hydrochloride, respectively. The second method was based on the separation of nifedipine from acebutolol hydrochloride, with an internal standard thymolphthalein, using capillary gas-liquid chromatography with a programmable temperature change. The third method was based on high performance liquid chromatographic separation of the two drugs on a reversed-phase, C18, column using a mobile phase of methanol-water (55:45, pH 4.5) with a programmable flow rate of 1 ml min-1 for 4 min which changed to 2 ml min-1 for the rest of the run. The detection was done at 260 nm using oxprenolol hydrochloride as an internal standard. Both chromatographic methods showed good linearity, precision and reproducibility. No spectral or chromatographic interference from the tablet excipients were found. The proposed methods were successfully applied to the assay of commercial tablets and a content uniformity test. The procedures were rapid, simple nondestructive and suitable for quality control application.

Acebutolol↗

PubMed1985

Determination of the kinetics of deuteration of DNA.RNA hybrids by ultraviolet spectroscopy.

The kinetics of the hydrogen-deuterium exchange reactions of poly(dA).poly(rU) and poly(rA).poly(dT) has been examined, at pH 7.0 and at various temperatures in the 15-35 degrees C range, by stopped-flow ultraviolet spectrophotometry. For comparison, the deuteration kinetics of poly[d(A-T)].poly[d(A-T)] and poly(rA).poly(rU) has been reexamined. At 20 degrees C, the imino deuteration (NH----ND) rates of the two hybrid duplexes were found to be 1.5 and 1.8 s-1, respectively. These are nearly equal to the imino deuteration rates of poly[d(A-T)].poly[d(A-T)] (1.1 s-1) and poly(rA).poly(rU) (1.5 s-1) but appreciably higher than that of poly(dA).poly(dT) (0.35 s-1). It has been suggested that a DNA.RNA hybrid, an RNA duplex, and the AT-alternating DNA duplex have in general higher base-pair-opening reaction rates than the ordinary DNA duplex. The amino deuteration (NH2----ND2) rates, on the other hand, have been found to be 0.25, 0.28, and 0.33 s-1, respectively, for poly(dA).poly(rU), poly(rA).poly(dT), and poly[d(A-T)].poly[d(A-T)], at 20 degrees C. These are appreciably higher than that for poly(rA).poly(rU) (0.10 s-1). In general, the equilibrium constants (K) of the base-pair opening are considered to be greatest for the DNA.RNA hybrid duplex (0.05 at 20 degrees C), second greatest for the RNA duplex (0.02 at 20 degrees C), and smallest for the DNA duplex (0.005 at 20 degrees C), although the AT-alternating DNA duplex has an exceptionally great K (0.07 at 20 degrees C). From the temperature effect on the K value, the enthalpy of the base-pair opening was estimated to be 3.0 kcal/mol for the DNA.RNA hybrid duplex.

DNA↗

PubMed1980

1,25-Dihydroxyvitamin D3 stimulated increase of 7,8-didehydrocholesterol levels in rat skin.

A convenient, accurate assay was developed for determining skin cholesta-5,7-dien-3 beta-ol (7,8-didehydrocholesterol) concentrations. Ultraviolet spectrophotometry provided quantitation of the sterol from rat skins following saponification and chromatography on Lipidex and high-performance liquid chromatography. Correction for recoveries was accomplished by using 7,8-didehydro[3 alpha-3H]cholesterol as an internal standard. Chronic dosing of vitamin D-deficient rats with 1,25-dihydroxyvitamin D3 caused a 4-fold increase in skin 7-dehydrocholesterol content. This rise was not the result of changes in food consumption, body weight, or plasma calcium. Cholesterol concentrations were not significantly elevated although some of the other nonsaponifiable lipid components found in the high-performance liquid chromatogram appeared to be increased by the treatment. These results suggest that the vitamin D hormone 1,25-(OH)2D3 may exert a positive feedback regulation on the production of vitamin D3 in skin.

Animals↗

PubMed1978

Identification of 5,8-oxyretinoic acid isolated from small intestine of vitamin A-deficient rats dosed with retinoic acid.

A retinoid was isolated by a multistep procedure from the small intestines of vitamin A-deficient rats given a single dose of retinoic acid. The compound, designated 8II, was pure, as demonstrated by four high-pressure liquid chromatographic procedures. It was positively identified as 5,8-oxyretinoic acid by ultraviolet spectrophotometry, mass spectrometry, and spectral and chromatographic comparison to known compounds. It is probable that 5,8-oxyretinoic acid was produced from 5,6-epoxyretinoic acid under the acidic conditions used in the isolation. It is highly probable, therefore, that the natural product is 5,6-epoxyretinoic acid.

Animals↗

PubMed2003

Survey of nitrate and nitrite contents of vegetables grown in Korea.

A scientific basis for the evaluation of the risk to public health arising from excessive dietary intake of nitrate in Korea is provided. The nitrate () and nitrite () contents of various vegetables (Chinese cabbage, radish, lettuce, spinach, soybean sprouts, onion, pumpkin, green onion, cucumber, potato, carrot, garlic, green pepper, cabbage and Allium tuberosum Roth known as Crown daisy) are reported. Six hundred samples of 15 vegetables cultivated during different seasons were analysed for nitrate and nitrite by ion chromatography and ultraviolet spectrophotometry, respectively. No significant variance in nitrate levels was found for most vegetables cultivated during the summer and winter harvests. The mean nitrates level was higher in A. tuberosum Roth (5150 mg kg(-1)) and spinach (4259 mg kg(-1)), intermediate in radish (1878 mg kg(-1)) and Chinese cabbage (1740 mg kg(-1)), and lower in onion (23 mg kg(-1)), soybean sprouts (56 mg kg(-1)) and green pepper (76 mg kg(-1)) compared with those in other vegetables. The average nitrite contents in various vegetables were about 0.6 mg kg(-1), and the values were not significantly different among most vegetables. It was observed that nitrate contents in vegetables varied depending on the type of vegetables and were similar to those in vegetables grown in other countries. From the results of our studies and other information from foreign sources, it can be concluded that it is not necessary to establish limits of nitrates contents of vegetables cultivated in Korea due to the co-presence of beneficial elements such as ascorbic acid and alpha-tocopherol which are known to inhibit the formation of nitrosamine.

Allium↗

PubMed2004

The chemical investigations on the ripe fruits of Ammi visnaga (Lam.) Lamarck growing in Turkey.

Two furanochromones and one furanochromone glycoside were isolated from the fruits of Ammi visnaga (L.) Lam. They were identified as khellin, visnagin, and khellol glycoside by interpretation of spectral analyses. Quantitative determination of furanochromones in A. visnaga (L.) ripe fruits from Hatay region (Turkey) was carried out by ultraviolet spectrophotometry and gas chromatography. In addition, photochemical properties of furanochromones and chemical composition of essential oil were determined.

Ammi↗

PubMed1976

Ultraviolet spectrophotometric analysis of barbiturates. Current assessment as an emergency screening procedure.

Several laboratory methods are currently available for the detection of barbiturates, but few are suitable for emergency use, The authors evaluated use of an ultraviolet spectrophotometric method as a screening procedure and compared the results with results obtained by other barbiturate methods (colorimetric, gas-liquid chromatographic, and immunochemical), Procedure time was approximately 40 minutes, sensitivity 0.2 mg/dl, precision (coefficient of variation) 5.4%, recovery 97.8% for phenobarbital, and there was good correlation with results obtained by gas-liquid chromatography and the EMIT system for phenobarbital. The authors recommend ultraviolet spectrophotometry as an excellent screening procedure for assessing the severity of barbiturate intoxication.

Barbiturates↗

PubMedDate not supplied

Sudden death due to ingestion of cocaine.

A 27-year-old male died as the result of swallowing a bag of cocaine. Using gas chromatography and ultraviolet spectrophotometry, the concentration of cocaine was determined on all specimens submitted for analysis. These analyses revealed what may possibly be the highest concentrations of cocaine ever reported in the toxicology literature. These values were confirmed by another medical examiner toxicology laboratory.

Adult↗

PubMedDate not supplied

Disopyramide fatality: case report and GC/FID analysis.

This case involves massive ingestion of disopyramide by a 19-year-old male, found dead, not having had the benefit of medical intervention. Quantitation of the drug was accomplished by gas chromatography using a flame ionization detector (GC/FID). Identification of the compound was done by thin layer chromatography (TLC) and ultraviolet spectrophotometry (UVS). The blood concentration of disopyramide was 15 times the usual therapeutic level and was easily detected by FID.

Adult↗

PubMedDate not supplied

The determination of amoxapine in human fatal overdoses.

Amoxapine, a recently introduced dibenzoxazepine, has been found effective in clinical studies for the treatment of various types of depression. Two amoxapine related deaths, a 53-year-old white male and a 21-year-old white female, have been investigated by this office. Both had been prescribed amoxapine for depression. Quantitation of amoxapine was by gas chromatography using a 3% OV-17 column with confirmation by ultraviolet spectrophotometry and thin layer chromatography. Blood amoxapine concentrations were found to be 18 mg/L in the first subject, and 6.7 mg/L in the second subject. These concentrations are many-fold higher than the therapeutic serum concentrations of up to 0.21 mg/L reported in a clinical study. These cases illustrate the potential lethality of amoxapine overdosage and the need for caution in prescribing amoxapine to patients with suicidal tendencies.

Amoxapine↗

PubMedDate not supplied

Acute thiothixene overdose.

An acute thiothixene intoxication is presented. Blood thiothixene concentration of 0.52 mg/L was detected before it declined to 0.047 mg/L in 12 hrs. Analysis was by thin layer chromatography, ultraviolet spectrophotometry, and fluorescence spectrophotometry.

Adult↗

PubMed1975

Cyclization of uridine monophosphate by diethyl pyrocarbonate.

Reaction between diethyl pyrocarbonate and uridine 2'-phosphate or uridine 3'-phosphate leads to the formation in high yields of uridine 2':3'-cyclic phosphate. This reaction product was identified in experiments involving (a) ultraviolet spectrophotometry, (b) paper chromatography, (c) high voltage paper electrophoresis at both pH 3.5 and 7.4, (d) acid hydrolysis, and (e) digestion with pancreatic ribonuclease.

Alkaline Phosphatase↗

PubMed1996

Clinical and biochemical screening for Smith-Lemli-Opitz syndrome. Italian SLOS Collaborative Group.

Smith-Lemli-Opitz syndrome (SLOS) is a multiple congenital anomalies/mental retardation disorder possibly due to a defect of delta 7-sterol reductase, leading to low plasma cholesterol levels and to the accumulation of 7-dehydrocholesterol (7-DHC) and other cholesterol precursors. This study aimed to identify clinical features that could potentially be specific indicators for the clinical diagnosis of SLOS, and to test the reliability of ultraviolet spectrophotometry (UVS) as a biochemical screening procedure for the syndrome. Twenty patients with clinical suspicion of SLOS, referred to 11 Italian paediatric and clinical genetic centres, were collected during 1994. In 10 patients the diagnosis was confirmed biochemically by gas chromatography/mass spectrometry (GC/MS) analysis of serum sterols, whereas in the other 10 patients the serum sterol profiles were normal. A comparison between confirmed SLOS patients and biochemically negative subjects did not show clinical signs specific for the syndrome. UVS measurement of 7-DHC correlated well with GC/MS profiles, showing 100% sensitivity and specificity. Four out of five patients had serum bile acid concentrations below the normal range of controls.

Adolescent↗