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At least 163 records · Page 9Linked to original sources
PubMed2005

Study of inclusion complex formation between tropaeolin OO and beta-cyclodextrin by spectrophotometry and Infrared spectroscopy.

The mechanism of the inclusion of tropaeolin OO (TPOO) and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The inclusion depth of the guest molecule in the host molecule was demonstrated by infrared spectrometry. Effect of the pH, concentrations of beta-CD, solvents and ionic strength on the inclusion of TPOO and beta-CD were examined. The result showed that TPOO reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 1.50 x 10(3) l mol(-1). The thermodynamic parameters of inclusion reaction, DeltaG degrees , DeltaH degrees and DeltaS degrees were obtained.

Azo Compounds↗
PubMed2002

Photochemical reaction monitoring by ultra-violet spectrophotometry.

Within the framework of the monitoring of the trichloroacetylchloride (TCAC) photosynthesis, ultra-violet (UV) spectrophotometry is proposed as a simple and rapid tool allowing, in real time, the control of the process efficiency. A good correlation has been obtained between the results acquired by this alternative method and the standard gas chromatography.

Chloroacetates↗
PubMed2002

Study on the supramolecular interaction of curcumin and beta-cyclodextrin by spectrophotometry and its analytical application.

The supramolecular interaction of curcumin and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The mechanism of the inclusion was studied and discussed based on the variations of pK(a), absorption intensity, and infrared spectrograms. The results show that beta-CD reacts with curcumin to form a 2:1 host-guest complex with an apparent formation constant of 5.53 x 10(5) mol(-2) x L2. Based on the enhancement of the absorbance of curcumin produced through complex formation, a spectrophotometric method for the determination of curcumin in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and curcumin concentration was obtained in the range of 0-15 microg/mL, with a correlation coefficient (r) of 0.9991. The detection limit was 0.076 microg/mL. The proposed method was used to determine the curcumin in curry and mustard with satisfactory results.

Acetonitriles↗
PubMed2005

Study on the supramolecular interaction of thiabendazole and beta-cyclodextrin by spectrophotometry and its analytical application.

The beta-cyclodextrin-thiabendazole (beta-CD-TBZ) inclusion complex was synthesized and its structure characterized by (1)H NMR and IR. The mechanism of the supramolecular interaction of TBZ and beta-CD has been studied and discussed by spectrophotometry. The results showed that the phenyl ring of TBZ was included in the beta-CD cavity to form a 1:1 host-guest complex with an apparent formation constant of 1.60 x 10(3) mol(-1).L. On the basis of the enhancement of the absorbance of TBZ produced through complex formation, a spectrophotometric method for the determination of TBZ in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and TBZ concentration was obtained in the range of 8.86 x 10(-7)-1.45 x 10(-5) mol/L. The detection limit was 2.71 x 10(-7)mol/L, and the relative standard deviation was 0.86%. The interference of 48 coexisting substances was slight. The proposed method has been successfully applied to the determination of TBZ in fruits with recoveries of 96-103%.

Buffers↗
PubMed1962

The determination of copper in biological materials by flame spectrophotometry.

A method for the determination of the copper content of biological materials by flame spectrophotometry is described. The effects of interference by ions such as sodium and phosphate were eliminated by isolating copper as the dithizonate in CCl(4). Results obtained for the urinary excretion of copper by a patient with Wilson's disease before and after treatment with penicillamine are reported.

Copper↗
PubMed2002

[Determination of trace tin in food by solid-phase spectrophotometry].

A new method for the determination of trace amounts of tin by resin-phase spectrophotometry has been developed and the detailed experimental conditions investigated. Tin ion reacts with procatechol violet(PV) in potassium hydrogen phthalate-HCl buffer media(pH2.5) to form a stable complex. The complex enriched on an anion-exchange resin has a maximum absorption wavelength of 570 nm. The absorbance is directly proportional to the concentration of tin in the region of 0-150 micrograms.L-1 with an apparent molar absorptivity of 7.2 x 10(6) L.moL-1.cm-1. Most of the co-existed metal ions do not interfere the determination of tin ion. The developed procedure has been successfully employed to the determination of tin in some food examples.

Animals↗
PubMedDate not supplied

Determination of attapulgite and nifuroxazide in pharmaceutical formulations by sequential digital derivative spectrophotometry.

A new method for the sequential determination of attapulgite and nifuroxazide in pharmaceutical formulations by first- and second-derivative spectrophotometry, respectively, has been developed. In order to obtain the optimal conditions for nifuroxazide stability, studies of solvent, light, and temperature effects were performed. The results show that a previous hydrolysis of 2 h in 1.0 x 10(-1)M NaOH solution is necessary in order to obtain stable compounds for analytical purposes. Subsequently, the first- and second-derivative spectra were evaluated directly in the same samples. The sequential determination of the drugs can be performed using the zero-crossing method; the attapulgite determination was carried out using the first derivative at 278.0 nm and the nifuroxazide determination, using the second derivative at 282.0 nm. The determination ranges were 5.7 x 10(-6)-1.0 x 10(-4) and 3.7 x 10(-8) -1.2 x 10(-4)M for attapulgite and nifuroxazide, respectively. Repeatability (relative standard deviation) values of 1.2 and 3.0% were observed for attapulgite and nifuroxazide, respectively. The ingredients commonly found in commercial pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in tablets. Further, infrared spectroscopy and cyclic voltammetry studies were carried out in order to obtain knowledge of the decomposition products of nifuroxazide.

Anti-Infective Agents↗
PubMed2004

[Simultaneous determination of trace amounts of iron(II), copper(I) and cobalt(II) in aloe by second derivative peak area spectrophotometry].

A new method for simultaneous determination of iron(II), copper(I) and cobalt(II) was established by second derivative peak area spectrophotometry in chromogenic system of 1,10-phenanthroline. The method could avoid disturbing by some ions. The accuracy and sensitivity were improved. There is a linear relationship in the range of 0.0-8.5 microg x mL(-1) for Fe(II); of 0.0-7.3 microg x mL(-1) for Cu(I); and of 0.0-5.9 microg x mL(-1) for Co(II). The method has been applied to simultaneous determination of iron(II), copper(I) and cobalt(II) in aloe with satisfactory results. The average recovery is 98.6%-102% and the RSD is 0.1%-0.2%. There is no remarkable difference between these results and those of ICP-AES method.

Cobalt↗
PubMed1980

[Estimations of pregnanetriolone, pregnanetetrol, delta 5-pregnenetriol by spectrophotometry and by gas liquid chromatography (author's transl)].

The author describes two methods of simultaneous estimation of pregnanetriolone, pregnanetetrol and delta 5-pregnenetriol. These estimations may be carried out at the same time as those of pregnanediol and pregnanetriol. The first method is based on spectrophotometry of derivatives obtained with 80 % sulphuric acid. The second demands gas chromatography. It permitted us to verify the specificity of the first. Its specificity was also verified by coupling with mass spectrometry. These estimations are used in the diagnosis of deficiencies of 21 hydroxylase and 3-beta hydroxysteroid oxidoreductase from the adrenal cortex. The values frequently obtained for delta 5-pregnenetriol are given.

Chromatography, Gas↗
PubMedDate not supplied

Simultaneous determination of phenol and mononitrophenol isomers using PLS regression and conventional and derivative spectrophotometry.

The partial least squares regression method (PLS) was tested as a calibration procedure for the simultaneous determination of phenol, o-nitrophenol, m-nitrophenol and p-nitrophenol by both conventional and first derivative UV/Vis spectrophotometry. The experiments were conducted in the acidic, neutral and basic media. The results obtained by the application of the PLS procedure on the conventional and first derivative spectra in two solvent media were compared. It was found that the results obtained in the basic medium have better performance characteristics than those obtained in the acidic or neutral media. Comparable results were obtained in the case of both conventional and first derivative absorbance data. The proposed method was applied to the determination of the four phenol derivatives in natural spiked water samples at concentration levels between 1.0 and 10.0 microg ml(-1) with average recoveries in the range 96% - 99%.

Calibration↗
PubMed2006

Perioperative real-time monitoring of indocyanine green clearance by pulse spectrophotometry predicts remnant liver functional reserve in resection of hepatocellular carcinoma.

BACKGROUND: There is no standard method for predicting remnant liver functional reserve after hepatectomy or for monitoring it in real time. METHODS: Indocyanine green (ICG) clearance (K) was measured non-invasively and instantaneously using pulse spectrophotometry before surgery, during inflow occlusion and after hepatectomy in 75 patients who underwent anatomical liver resection for hepatocellular carcinoma (HCC). RESULTS: Eight patients (11 per cent) suffered liver failure and one (1 per cent) died in hospital. An estimated remnant K value of 0.090 per min was the cut-off value for liver failure. In a logistic regression model, the estimated remnant K (0.090 per min; P = 0.022) and age (65 years; P = 0.025) were significant predictors of postoperative liver failure. There was a correlation between the estimated and measured post-hepatectomy K, and between the inflow occlusion K and measured post-hepatectomy K (P < 0.001). The cut-off value of less than 0.090 per min for the estimated remnant K resulted in 88 per cent sensitivity and 82 per cent specificity for predicting liver failure. CONCLUSION: Perioperative real-time monitoring of ICG-K is useful for evaluating the remnant liver functional reserve before, during and after liver resection for HCC. The estimated remnant K is a significant predictor of liver failure.

Aged↗
PubMed1987

[Quantitative determination of the protein content of milk by ultraviolet spectrophotometry. 3. Determination of proteins in preserved milk samples].

It is reported upon the results of the quantitative estimation of protein content from preserved milk by means of ultraviolet spectrophotometry. In addition to the preservation by boric acid, bronopol, copper sulphate, potassium dichromate and ammonium peroxodisulphate storage at temperatures below 0 degrees C and freeze drying were tested. Besides bronopol and copper sulphate especially physical preservation methods proves fit for the protein estimation by measurements of absorbance at 210 nm, 235 and 280 nm or 210 and 220 nm. It is recommended to use solutions and filters of quartz with evaluated absorbance in daily calibrating of the spectrophotometer.

Animals↗
PubMedDate not supplied

Hepatic hemodynamics and oxygen consumption in alcoholic fatty liver assessed by organ-reflectance spectrophotometry and the hydrogen clearance method.

Hepatic blood flow and estimated hepatic oxygen consumption were studied in rats treated chronically with ethanol by organ-reflectance spectrophotometry and the hydrogen clearance method. In the withdrawal state from ethanol, the concentration of hemoglobin in the hepatic tissue (delta Er569-650), the estimated hepatic oxygen consumption (estimated VO2) and the regional liver blood flow decreased significantly in rats treated chronically with ethanol in comparison with their controls. On the other hand, there was no significant difference in the estimated oxygen saturation of the hepatic blood hemoglobin (estimated SO2) between both groups. That is, an increase in oxygen extraction, which was exhibited by a decrease in the estimated SO2, did not occur in rats treated chronically with ethanol in spite of a decrease in blood supply. Thus, in the withdrawal state from ethanol, both oxygen delivery to the liver and oxygen utilization in the liver were disturbed at the stage of alcoholic fatty liver.

Animals↗
PubMed1992

Determination of aluminum in biological fluids by furnace atomic absorption spectrophotometry.

Detailed procedures were developed for the furnace atomic absorption spectrophotometry (FAAS) determination of aluminum (Al) in serum, urine, cerebrospinal fluid (CSF), and proportionated dialysate. Of particular note were the use of Mg (NO3)2.6H2O as a matrix modifier and the employment of the standard additions routine in analysis. The accuracy of the method(s) used is supported by work with assayed controls and by recovery studies. The use of a "clean room" was shown to be unnecessary. Normal serum, urine, and CSF Al ranges observed were 4.8-8.9, 5.1-9.1, and 1.0-5.8 micrograms L-1 respectively.

Aluminum↗
PubMed2002

Partition of N-monodemethylated phenothiazine drugs to phosphatidylcholine bilayer vesicles studied by second-derivative spectrophotometry.

The partition coefficients (Kps) of three N-monodemethylated metabolites of phenothiazines (chlorpromazine (CPZ), triflupromazine, and promazine) between phosphatidylcholine (PC) vesicles (SUV) and water were determined to evaluate their affinity to biomembranes by second-derivative spectrophotometry without any separation procedures. The second derivative spectra showed distinct derivative isosbestic points confirming the entire elimination of the residual background signal effects of the SUV, which were observed in the absorption spectra. From the relationship between PC SUV concentration and the derivative intensity change (DeltaD) of each metabolite induced by its interaction with the PC bilayer, the Kp values were calculated and could be obtained with the R.S.D. of below 10% (n = 5) proving an accuracy of the derivative method. The obtained Kp values were similar to those of the parent drugs (the relative differences were within 15%), although the partition coefficient of N-monodemethylated CPZ measured in an octanol/buffer system was reported to be about 1/18 of CPZ. The results obtained from the PC liposome/buffer system do not contradict with psychoactivity and brain accumulation of N-monodemethylated metabolites of phenothiazines, in contrast to the results of the octanol/buffer system.

Antipsychotic Agents↗
PubMed1976

Binding study of tetracyclines to human serum albumin using difference spectrophotometry.

The binding of several tetracyclines to human serum albumin was studied using difference spectrophotometry and a spectrophotometric probe, 2-(4'-hydroxybenzeneazo)benzoic acid. Difference spectra observed for the interaction between the probe and human serum albumin were similar to probe-bovine serum albumin spectra but were less intense for a given concentration of probe and did not reach saturation as quickly. Difference spectra for the tetracyclines were dependent on the characteristics of the ring substituents. More hydrophobic substituents on the D and C rings tended to give more intense difference spectra, but charge-transfer complexing may also have been involved since methacycline with a methylene group in the 6-position showed the most intense spectra of the compounds studied. Solvent perturbation, pH, and urea studies tended to confirm that something other than hydrophobic binding of the tetracyclines was involved. Drug-probe displacement studies showed that methacycline gave the greatest probe displacement followed by doxycycline, chlortetracycline, oxytetracycline, and tetracycline. This order of displacement of the anionic probe indicates that both hydrophobic and charge-transfer binding are involved. Experiments with calcium ion and ethylenediaminetetraacetic acid showed that the difference spectra obtained with the tetracyclines and human serum albumin were not the result of metallic bridge-chelate formation.

Calcium↗
PubMed1976

Quantitative determination of theophylline in pharmaceutical dosage forms by differential spectrophotometry.

Theophylline was determined with good precision in tablets and capsules by differential spectrophotometry. Xanthines such as caffeine and theobromine did not interfere providing the total xanthine concentration was kept below 100 mug/ml. At a higher total xanthine concentration, nonlinearity occurred, presumably due to complex formation. This interference could be minimized by proper selection of the analytical wavelength.

Amobarbital↗
PubMed1988

Zero-crossing derivative spectrophotometry for the determination of mixtures of cephaloridine and cephalothin in pure and dosage forms.

First- and second-derivative spectrophotometry, with a zero-crossing technique of measurement, has been used for the quantitation of two-component mixtures of cephaloridine and cephalothin Na, which are cephalosporins with closely overlapping spectral bands. Beer's Law is followed for up to 28 and 36 micrograms/mL of cephaloridine in the first- and second-derivative modes, respectively, and up to 36 micrograms/mL of cephalothin Na in both modes. Detection limits at the 0.05 level of significance were calculated to be 0.13 and 0.37 micrograms/mL of cephaloridine and cephalothin Na, respectively, in the first-derivative mode, and 0.25 and 0.29 micrograms/mL, respectively, in the second-derivative mode. The recovery of these antibiotics in mixtures of injectable dosage forms is also reported.

Cephaloridine↗