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PubMed1989

Determination of acetoacetate in urine by solid-phase spectrophotometry.

A method for the determination of acetoacetate has been developed based on solid-phase spectrophotometry (SPS). The acetoacetate reacts with nitroprusside and glycine and the reaction product is sorbed on Dowex 1-X8 resin. The absorbance of the resin phase at 590 and 720 nm is measured directly. The calibration graph is linear up to 3.3 mg l-1 and the RSD is 1.9%. The detection limit is 7.6 micrograms l-1. The method has been applied to the determination of acetoacetate in normal and diabetic subjects' urine without pretreatment of the samples, and the results compared with those of 1H-NMR and homogeneous nitroprusside methods.

Acetoacetates↗
PubMed1989

Determination of sulphacetamide, sulphadimidine or sulphathiourea in the presence of their degradation products using first derivative spectrophotometry.

A method is presented for the determination of sulphacetamide sodium, sulphadimidine and sulphathiourea in the presence of their acid-induced degradation products using first derivative spectrophotometry. By measuring the absolute value of the first derivative curves at the zero contribution of the corresponding degradation products, the concentration of the intact drug can be calculated directly without interference of the degradation product. The validity of the method was confirmed using synthetic mixtures of the intact drugs with their degradation products.

Drug Stability↗
PubMed1991

Simultaneous determination of imipramine and amitryptiline by derivative spectrophotometry.

Three methods are proposed for the simultaneous determination of imipramine and amitryptiline by derivative spectrophotometry, one of them using both first- and second-derivative spectra, and the others using the first- and second-derivative spectra, respectively, obtained from a "diode array" spectrophotometer. The methods allow the determination of 0.62-10.14 micrograms ml-1 of imipramine, and 0.63-10.04 micrograms ml-1 of amitryptiline, and have been applied to their determination in blood serum.

Amitriptyline↗
PubMed1991

Solubility and acid-base behaviour of midazolam in media of different pH, studied by ultraviolet spectrophotometry with multicomponent software.

The solubility of midazolam is less than 0.1 mg ml-1 at neutral pH and it increases considerably in acidic media. A pKa value of 6.04 at 24 +/- 1 degree C was calculated from the solubility data. In acidic media midazolam is reversibly converted to the corresponding benzophenone (open-ring form). The extent of this reaction was investigated by assaying the two compounds simultaneously by UV spectrophotometry with multicomponent software. The structure of the benzophenone derivative was verified by IR, MS and 1H and 13C NMR spectrometry.

Chromatography, Thin Layer↗
PubMed1994

Determination of imipenem and cilastatin sodium in Primaxin by first order derivative ultraviolet spectrophotometry.

A UV-spectrophotometric assay to measure the concentrations of the active drug components (imipenem and cilastatin) or Primaxin for routine release testing is described. The assay is based on the use of first order derivative spectrophotometry. The trough amplitudes in the first derivative spectrophotometric spectra at 243 and 318 nm were selected to determine cilastatin and imipenem, respectively. A linear relationship (R > 0.99) between the trough amplitudes and concentrations was demonstrated over the range 14-42 micrograms ml-1 for both drug components. Commercial IV formulations and laboratory prepared mixtures containing both drugs in different proportions were assayed using the developed method with good recoveries (ave. 100.6%). The method is rapid, precise, accurate and was shown to be equivalent to the more time consuming LC method; which is currently used for routine release testing. The specificity and stability indicating properties of the method will also be addressed.

Buffers↗
PubMed1995

Determination of ternary mixtures of antibiotics, by ratio-spectra zero-crossing first- and third-derivative spectrophotometry.

The ratio-spectra zero-crossing first- and third-derivative spectrophotometry have been used for determining ternary mixtures of penicillin-G sodium, penicillin-G procain and dihydrostreptomycin sulphate salts. The procedures are accurate, nondestructive and do not require resolutions of equations. In both methods, calibration graphs are linear, with zero-intercept, up to 30 micrograms ml-1 of penicillin-G sodium and penicillin-G procain, and up to 42 micrograms ml-1 of dihydrostreptomycin sulphate. r = 0.9999 in each instance. Working wavelengths, 218.5, 211 and 236 nm, respectively, in the first-derivative mode, and 222.5, 311.5 and 242 nm in the third-derivative mode. Detection limits for each drug at p = 0.01 level of significance were calculated to be 0.058, 0.010 and 0.014 micrograms ml-1 and 0.14, 0.012 and 0.34 micrograms ml-1, in the first- and third-derivative methods, respectively. Both methods apply favorably to either laboratory mixtures or commercial injections.

Dihydrostreptomycin Sulfate↗
PubMed1995

Simultaneous determination of enalapril maleate and hydrochlorothiazide by first-derivative ultraviolet spectrophotometry and high-performance liquid chromatography.

Two methods are described for the simultaneous determination of enalapril maleate and hydrochlorothiazide in combined pharmaceutical tablets. The first method depends on first-derivative ultraviolet spectrophotometry, with zero-crossing and peak-to-base measurement methods. The first-derivative amplitudes at 224 and 260 nm were selected for the assay of enalapril maleate and hydrochlorothiazide, respectively. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of acetonitrile-water (20:80, v/v) (pH 3.8) with programmable detection at 215 and 275 nm. Both methods showed good linearity, precision and reproducibility. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in commercial tablets.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Simultaneous determination of cefepime and L-arginine in injections by second-derivative spectrophotometry.

A simple spectrophotometric assay for the determination of cefepime and L-arginine in injections is described. Since zero-order spectra showed considerable overlap, second-derivative spectrophotometry was used to enhance the spectral details. A linear relationship between second-derivative amplitude and concentration of each compound was found. Beer's law was obeyed up to 50 and 22 micrograms ml-1 of cefepime and arginine, respectively, in the second-derivative mode. Detection limits were 0.31 and 0.58 micrograms ml-1 for cefepime and arginine, respectively. The method, which is rapid, simple and does not require any separation step, has been successfully applied to the assay of commercial injections containing cefepime and arginine.

Arginine↗
PubMed1995

Analysis of pharmaceutical creams: a useful approach based on solid-phase extraction (SPE) and UV spectrophotometry.

Solid-phase extraction (SPE) using C-18, diol and ion-exchange sorbents followed by UV spectrophotometric (conventional and derivative mode) assay was applied to the analysis of basic, acidic and neutral drugs commercially available in creams. A representative set of drugs (promethazine, chlorhexidine, benzydamine, ketoprofen, ibuprofen, fentiazac, piroxicam, fluorouracil, crotamiton and hydrocortisone acetate) was selected, and for each drug the appropriate SPE conditions (adsorption, washing and elution) were investigated to obtain a practical and reliable sample clean-up. It was shown that the developed SPE procedures were capable of removing interfering cream components (excipients including preservatives) allowing accurate spectrophotometric analyses to be performed. In some applications, derivative spectrophotometry was advantageous over the conventional absorption mode with respect to higher selectivity and versatility.

Pharmaceutical Preparations↗
PubMed1996

Analysis of binary mixtures of cephalothin and cefoxitin by using first-derivative spectrophotometry.

A method for the analysis of two-component mixtures of cephalothin and cefoxitin using zero-crossing first-derivative spectrophotometry is described. This technique permits the quantification of these drugs with closely overlapping spectral bands without any separation step. Linear calibration graphs of first-derivative values at 235.00 and 236.75 nm for cephalothin and cefoxitin, respectively, with negligible intercepts were obtained versus concentration in the range 4.0-32.0 micrograms ml-1 for both antibiotics. This paper presents a systematic examination of the experimental data by applying an exhaustive statistical analysis to demonstrate the validity of the method. The results of the determination of these antibiotics in mixtures of injectable dosage forms are also presented, together with their determinations in physiological serum and glucosed physiological serum.

Calibration↗
PubMedDate not supplied

Hepatic hemodynamics in alcoholic liver injuries assessed by reflectance spectrophotometry.

We have investigated the hepatic hemodynamics by reflectance spectrophotometry in patients with alcoholic liver disease. The analysis of 32 cases has shown that the estimated regional hepatic tissue blood hemoglobin concentration, expressed as a difference in absorbance between 569 and 650 nm (delta Er569-650), decreased significantly with progress of fibrosis in the liver, suggesting the relative compression of the vascular compartment due to the progress of alcoholic liver disease. The estimated hepatic oxygen consumption also decreased with progress of fibrosis in the liver. The estimated hepatic oxygen consumption correlated positively with prothrombin time and serum albumin level, and negatively with the fifteen minute retention rate of indocyanine green. Thus, it is concluded that the imbalance between supply and utilization of oxygen in the liver may have an important role in the progress of alcoholic liver disease.

Adult↗
PubMed1985

Separation and characterization of metallothionein in two species of seals by high performance liquid chromatography-atomic absorption spectrophotometry.

Metallothionein (MT) was separated from the livers of two species of seals, ribbon seal (Histriophoca fasciata) and harbour seal (Phoca vitulina), by high performance liquid chromatography--atomic absorption spectrophotometry (HPLC-AAS). Both gel permeation and anion-exchange HPLC demonstrated that MT was present as a mixture of at least two isoforms in the livers of both species of seals.

Animals↗
PubMed1994

Cerebral oxygenation in childhood moyamoya disease investigated with near-infrared spectrophotometry.

In children with moyamoya disease, the time courses of hemoglobin concentrations before and after hyperventilation were examined using near-infrared spectrophotometry (NIRS) to determine brain tissue oxygenation. Five patients were studied: 1 was studied both before and after surgery and 4 were studied only after surgery. Nine hemispheres of these 5 patients were examined. The oxygenated hemoglobin concentration increased immediately after beginning hyperventilation. This parameter later decreased sharply to below the prehyperventilation level and remained at the reduced level for a prolonged period. These changes in oxygenated hemoglobin concentration were similar to those previously reported in arterial blood oxygen and CO2 tension. The magnitude of variance in oxygenated hemoglobin concentration (C-HV) was significantly greater in moyamoya disease patients than in healthy controls (P < .003, Wilcoxon test). The changes of NIRS after operation were markedly more sensitive than those of electroencephalography or single-photon emission computed tomography. NIRS could be applied to cerebral oxygenation as well as cerebral hemodynamics, which may be used to better define the time sequence and pathologic processes of various childhood encephalopathies.

Adolescent↗
PubMed1995

An empirical technique to compensate for melanin when monitoring skin microcirculation using reflectance spectrophotometry.

Errors can occur in measuring blood content and oxygenation in subjects with significant skin pigmentation using reflectance spectrophotometry. The melanin in the epidermis not only reduces the amount of back-scattered light, but also has a characteristic absorption spectrum that varies between individuals. Skin color is primarily influenced by the concentration of melanin, blood content and oxygenation in the superficial microvasculature. A three-step process was developed empirically to accommodate the effect of melanin in the absorption spectrum of skin. A melanin index was developed and applied for each individual tested. Spectral components attributable specifically to melanin were subtracted from the measured spectrum, and its amplitude was normalized. This technique was tested with 26 able-bodied subjects with different levels of skin pigmentation. The melanin-compensated spectra from pigmented and caucasian skin were indistinguishable and no correlation was found between calculated values for indices of blood content and oxygenation, and melanin index.

Algorithms↗
PubMed2006

Microcirculation in DIEP flaps: a study of the haemodynamics using laser Doppler flowmetry and lightguide reflectance spectrophotometry.

The deep inferior epigastric perforator (DIEP) flap is ideally suited for breast reconstruction. The DIEP flap reduces abdominal wall morbidity when compared to a transverse rectus abdominis (TRAM) flap, however, there maybe a compromise of the flap vascularity. Early venous problems and late fat necrosis in DIEP flaps can occur. There is a limited literature on the haemodynamic and microcirculation of the DIEP flap. Sixteen consecutive patients who underwent immediate breast reconstruction with DIEP flap were prospectively monitored during the post-operative time for a minimum period of 48h using laser Doppler flowmetry (LDF) and lightguide reflectance spectrophotometry (LRS) to analyse blood flow and oxygenated haemoglobin percentage in the cutaneous microcirculation of the flap. LDF demonstrated an increase of capillary flow in comparison to the pre-operative levels. LRS showed an initial decrease of the values and a varying pattern of increase in relation to time, to reach the pre-operative levels. A correlation between lower values of post-operative LDF and LRS measurements and late fat necrosis and early venous congestion was demonstrable in this series. This study demonstrates a change in the cutaneous microcirculation of the lower anterior abdominal wall following its elevation as a DIEP flap. These findings could explain the clinical phenomenon occurring in this flap in the early post-operative period. Significant correlation between longer harvesting time and re-exploration and between longer ischaemia time and localised fat necrosis was found.

Abdominal Wall↗
PubMed2006

Determination of the degree of acetylation of chitosan by UV spectrophotometry using dual standards.

Determination of the degree of acetylation of chitosan by UV spectrophotometry using dual standards is investigated. The UV absorbance of a pure chitosan solution is contributed additively by the N-acetylglucosamine and glucosamine residues; the absorbance divided by the total molar concentration of the residues (A/c(t)) is linearly related to the degree of acetylation (DA). Using acetyl glucosamine and glucosamine hydrochloride as standards in 0.1M hydrochloric acid solution, the equation obtained by linear regression is A/c(t)=3.3615 DA+0.0218, R(2)=0.9958. The DA of the analytical sample (m milligram of chitosan in V liters solution) can be calculated by.

Acetylation↗
PubMed2006

Determination of sulfonamide compounds in sewage and river by mixed hemimicelles solid-phase extraction prior to liquid chromatography-spectrophotometry.

Mixed hemimicelles-based solid-phase extraction was investigated for the preconcentration of five sulfonamides from environmental water samples prior to HPLC-spectrophotometry determination in this paper. A comparative study on the use of sodium dodecyl sulfate (SDS) coating gamma-alumina or octadecyltrimethylammonium bromide (OTMABr) and OTMABr coating silica as sorbent materials were presented. The five analytes (sulfadiazine (SDA), sulfathiazole (STA), sulfapyridine (SPD), sulfamethazine (SMZ) and sulfamethoxazole (SMX)) were quantitatively adsorbed on OTMABr-gamma-alumina and OTMABr-silica mixed hemimicelles, but OTMABr-gamma-alumina was not adopted because it worked at a high pH (around 10), instead, OTMABr-silica was selected to overcoming the pH restriction. The analytes retained on the cartridge were quantitatively desorbed with suitable amounts of methanol. Factors influencing the extraction efficiency, such as the amount of surfactant, pH of sample and breakthrough volume were discussed. The proposed method had been applied to determining the five sulfonamides in several environmental water samples and concentration factors of 300 and 600 for SDA and other four analytes were achieved, respectively. Detection limits obtained ranged between 0.15 and 0.35microg/L for this five sulfonamides under the optimized conditions. The accuracy of the method was evaluated by recovery measurements on spiked samples, and good recovery results (89-113%) with precision of 3-6% were achieved.

Chromatography, Liquid↗
PubMed2004

Determination of ranitidine hydrochloride in pharmaceutical preparations by titrimetry and visible spectrophotometry using bromate and acid dyes.

Four new methods using titrimetry and spectrophotometry are described for the determination of ranitidine hydrochloride (RNH) with potassium bromate as the oxidimetric reagent and acid dyes, methyl orange, indigo carmine and metanil yellow. In direct titrimetry (method A), the drug is titrated directly with bromate in acid medium and in the presence of excess of bromide using methyl orange indicator. In back titrimetry (method B), the drug is treated with a measured excess of bromate in the presence of bromide and acid, and the unreacted bromine is determined iodometrically. Both spectrophotometric methods are based on the oxidation of RNH by a known excess of bromate in acid medium and in the presence of excess of bromide followed by estimation of surplus oxidant by reacting with either indigo carmine (method C) or metanil yellow (method D), and measuring the absorbance at 610 or 530 nm. In methods B, C and D, reacted oxidant corresponds to the drug content. The experimental conditions are optimized. Titrimetric procedures are applicable over the ranges 1-10 mg (A) and 1-17 mg (B), and the reaction stoichiometry is found to be 1:1 (BrO(-)(3): RNH). In spectrophotometric methods, the absorbance is found to increase linearly with increasing concentration of RNH, which is corroborated by the calculated correlation coefficient (r) of 0.9984 (C) and 0.9976 (D). The systems obey Beer's law for 2-12 and 1-7 microg ml(-1), for methods C and D, respectively. Method D with a molar absorptivity of 9.82 x 10(4) l mol(-l) cm(-1) is found to be more sensitive than method C ( epsilon = 2.06 x l0(4) l mol(-1) cm(-1)). The limits of detection and quantification are reported for both the spectrophotometric methods. The proposed methods were applied successfully to the determination of RNH in tablets and injections. The reliability of the assay was established by parallel determination by the official method and by recovery studies.

Acids↗