Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectrophotometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources
PubMed1986

[Value of derivative spectrophotometry for the determination of plasma and urinary hemoglobin. Comparison with the method using Allen's correction].

We are proposing a technique enabling the dosage of hemoglobin in plasma or urine using spectrophotometry in derivative double dash. Around 420 nm hemoglobin has an elevated molecular extinction factor but the absorption of natural pigments creates a non-negligible interference in the classic spectrophotometric methods. On the contrary, the use of the derivative double dash enables to practically eliminate the background noise and to obtain a specific signal for hemoglobin while keeping an excellent sensitivity. In the plasma, where hemoglobin is entirely linked to haptoglobin, the dosage is done by direct reading (while in the urine the presence of several pigment forms requires the use of Drabkin's reagent. The method is simple, quick, precise and enables to titrate 1 mg.l (or 0.015 mumole.l-1) of hemoglobin. The influence of bilirubin is negligible. The comparison with a method using Allen's correction shows the superiority of the former as far as precision and accuracy are concerned, by avoiding the danger of a non-negligible systematic error.

Hemoglobins↗
PubMed1986

A new method to study glutathione adduct formation in periportal and pericentral regions of the liver lobule by micro-reflectance spectrophotometry.

A method was developed to measure the formation of glutathione adducts of 1-chloro-2,4-dinitrobenzene (CDNB) and 2,4-dichloro-1-nitrobenzene (DCNB) in periportal and pericentral regions of the liver lobule in the isolated perfused rat liver by surface reflectance spectrophotometry. Conjugates of DCNB and CDNB are released from livers of normal and phenobarbital-treated rats during perfusion in either the anterograde or the retrograde direction at maximal rates around 13-15 mumol/g/hr. The formation of S-(1-chloro-4-nitrophenyl)-glutathione and S-(2,4-dinitrophenyl)-glutathione by the liver decreased the amount of 366-nm light reflected from the liver surface detected with a large-tipped (2 mm) fiberoptic light guide. Initial rates of decrease in reflected light correlated highly with maximal rates of conjugate formation by the liver. Subsequently, micro-light guides were placed on periportal and pericentral regions of the liver lobule. Rates of glutathione adduct formation were calculated from the proportion of the total change in rate of reflected 366-nm light which occurred in each region and the overall rate of product formation by the liver. Changes in the reflectance signal require reduced glutathione (GSH) and were shown to originate from intracellular conjugate formation and not from adducts in the bile canaliculus. Livers from normal rats produced conjugated products from DCNB (100 microM) at maximal rates of 14 and 15 mumol/g/hr in periportal and pericentral regions of the liver lobule, respectively. With CDNB as substrate, changes in reflected light at 366 nm were detected nearly exclusively in periportal regions of the lobule in livers from normal rats. In sharp contrast, CDNB and DCNB were conjugated exclusively in periportal regions of the lobule at rates of 21-22 mumol/g/hr in livers from phenobarbital-treated rats (i.e., the reflectance signal was not altered by these substrates in pericentral areas). When CDNB and DCNB were infused into livers from phenobarbital-treated rats perfused in the retrograde direction, decreases in reflected light at 366 nm were detected initially in pericentral areas followed in about 12 min by changes in periportal regions. Maximal rates of adduct formation in both regions reached 25 mumol/g/hr during perfusion in the retrograde direction. Thus, pericentral regions indeed possess the capacity to conjugate both CDNB and DCNB. When glutathione synthesis was inhibited with L-buthionine sulfoximine treatment (6 mmol/kg), which partially depletes GSH, CDNB was conjugated in both periportal and pericentral regions of the liver lobule in livers from phenobarbital-treated rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

[Aminopenicillin crystalluria: identification by infrared spectrophotometry].

Renal stones and crystalluria can be characterized unambiguously by global physical methods. The authors report four cases of crystalluria induced by aminopenicillin (ampicillin and amoxicillin). Identification of these drug-induced crystalluria was made by high-pressure liquid chromatography and infrared spectrophotometry. The physico-chemical data and infrared absorption characteristics can give us diagnostic for various forms of ampicillin and amoxicillin.

Adult↗
PubMedDate not supplied

Electrothermal atomic absorption spectrophotometry of nickel in tissue homogenates.

A method for analysis of Ni concentrations in tissues is described, which involves (a) tissue dissection with metal-free obsidian knives, (b) tissue homogenization in polyethylene bags by use of a "Stomacher" blender, (c) oxidative digestion with mixed nitric, sulfuric, and perchloric acids, and (d) quantitation of Ni by electrothermal atomic absorption spectrophotometry with Zeeman background correction. The detection limit for Ni in tissues is 10 ng per g, dry weight; the coefficient of variation ranges from 7 to 15 percent, depending on the tissue Ni concentration; the recovery of Ni added in concentration of 20 ng per g, dry weight, to kidney homogenates averages 101 +/- 8 percent (mean +/- SD). In control rats, Ni concentrations are highest in lung (102 +/- 39 ng per g, dry weight) and lowest in spleen (35 +/- 16 ng per g, dry wt.). In descending order of Ni concentrations, the tissues of control rats rank as follows: lung greater than heart greater than bone greater than kidney greater than brain greater than testis greater than fat greater than liver greater than spleen. In rats killed 24 h after sc injection of NiCl2 (0.125 mmol per kg, body weight) Ni concentrations are highest in kidney (17.7 +/- 2.5 micrograms per g, dry weight) and lowest in brain (0.38 +/- 0.14 micrograms per g, dry weight). In descending order of Ni concentrations, the tissues of NiCl2-treated rats rank as follows: kidney much greater than lung greater than spleen greater than testis greater than heart greater than fat greater than liver greater than bone greater than brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Algorithms for automated ultramicroanalysis by bichromatic paper disk spectrophotometry.

Three types of methods for bichromatic paper disk spectrophotometry are described and illustrated by the detailed presentation of procedures for the dosage of hemoglobin and protein (with some applications in virology), as well as for glucose determination. The general algorithms that would make possible the automation of these methods by means of programmable systems are presented.

Autoanalysis↗
PubMed1985

[Ultraviolet spectrophotometry of the cerebrospinal fluid in the differential diagnosis of strokes].

The authors describe the possibility of using the results of ultraviolet spectrophotometry of the cerebrospinal fluid (CSF) for the differential diagnosis of ischemic, hemorrhagic and mixed cerebral strokes. It was found that repeated examinations may be of a definite prognostic value. A correlational analysis showed that the greatest effect on the optical density of the CSF in cases of hemorrhagic strokes is exercised by protein and bilirubin and in cases of ischemic strokes by protein and aspartate aminotransferase (AST).

Adult↗
PubMed1985

[Application of derivative spectrophotometry in biochemistry].

Derivative spectrophotometry is used to increase the specificity of spectroscopic measurements. The main advantages of this method are a better resolution of overlapping bands and a reduction in the effects of turbidity and coloured background. Its biochemical applications of this method are reviewed.

Amino Acids↗
PubMed1979

Direct determination of lead and cadmium in blood and urine by flameless atomic absorption spectrophotometry.

We describe procedures for direct determination of lead and cadmium in blood and urine by flameless atomic absorption spectrophotometry. Before analysis, the samples are pre-ashed in microboats in an ordinary laboratory oven. In this way, many samples can be prepared and pre-ashed simultaneously. We find the procedures presented in this work to be rapid, accurate, and precise.

Cadmium↗
PubMed1969

Assay of acyl-CoA:monoglyceride acyltransferase from rat small intestine using continuous recording spectrophotometry.

Acyl-CoA:monoglyceride acyltransferase in microsomal preparations from the small intestine of the rat has been measured by means of continuous recording spectrophotometry. The reaction of 5,5'-dithiobis(2-nitrobenzoic acid) with CoA has been employed for this assay and optimal conditions for the reaction have been defined. One of the substrates, palmitoyl-CoA, inhibits the reaction even in modest concentrations. This inhibition is largely prevented by the addition of bovine serum albumin to the incubation medium. The reliability of the assay method was confirmed by comparison with the more cumbersome assay method that uses radioactive substrate.

Acyltransferases↗
PubMed1978

Platelet metal levels in normal subjects determined by atomic absorption spectrophotometry.

A method has been developed for the estimation of iron, copper, zinc, calcium and magnesium in human platelets using atomic absorption spectrophotometry. Fe and Cu are either absent or present in very low concentration approaching the limit of detection: Zn, Ca and Mg are readily detectable. EDTA is preferable to ACD(A) or heparin as the anticoagulant for collection in that the platelet yield is reliable: however, slightly low results for Ca and Mg are obtained. Corrections for residual plasma and contaminating red cells are essential. Plasma and platelet metal levels in 33 normal subjects are reported together with the findings in four studies undertaken on platelets obtained from subjects with polycythemia vera.

Adult↗
PubMedDate not supplied

Nucleic acid spectrophotometry on paper disks.

A bichromatic spectrophotometry study in the near UV spectral range was performed on paper disks impregnated with DNA and RNA in NaCl solutions of different concentrations. Absorbance curves plotted versus a NaCl molarity log-scale degree of polymerization and the solubility of the polynucleotide. The -a/b value, determined by a previously reported equation, appeared to be constant for a given nucleic acid, irrespective of the wavelength in the spectral range 205-280 nm. This phenomenon cannot be attributed to a heterogeneous macroscopic distribution of the nucleic acid throughout the disk.

DNA↗
PubMed1978

Improved ultraviolet spectrophotometry of serum theophylline.

We present an improved method for ultraviolet spectrophotometry of theophylline in serum. We studied various extraction techniques aimed at eliminating interferences from co-extractable serum constituents. In the resulting modified procedure, 1 ml of serum is required and a salt-solvent pair of ammonium sulfate and chloroform/hexane is used for extraction. The solvent forms the top phase after extraction, the lower phase after back-extraction, thereby permitting easy removal of the appropriate phase from culture tubes. The use of ammonium sulfate coupled with the added specificity of the extraction solvent results in an extract with low background absorption and a well-defined spectrum for the extracted theophylline.

Humans↗
PubMed1982

Use of noninvasive fluorometry and spectrophotometry to study epithelial metabolism and transport.

Various examples illustrating the use of spectrophotometry and fluorometry in epithelia are presented. The first example uses the redox level of cytochrome aa3, measured spectrophotometrically as an index of tissue anoxia in cortical tubules and slices from the rabbit kidney. In the second example the redox level is used to measure the kinetics of aerobic energy production during transition to anoxia in the midgut of the tobacco hornworm. In the third application, the redox level of mitochondrial NADH is measured fluorometrically in a cortical tubule suspension from the rabbit kidney. Inhibition of active transport work causes reduction of NAD whereas increased work elicits oxidation of NAD, both occurring as expected from mitochondrial transitions to a lesser or more active state, respectively. Another use of NADH fluorescence is the determination of the relative effectiveness of metabolic substrates to deliver reducing equivalents to the respiratory chain in a particular tissue. Redox changes in mitochondrial NAD may be used to distinguish between primary metabolic and primary transport effects of hormones, drugs, and changes in the state of the organism. Finally, examples are provided of the use of an intracellular pH-sensitive dye and an extracellular calcium-sensitive dye in kidney tubules.

Animals↗
PubMed1984

Comparison of diluents for serum magnesium estimation by atomic absorption spectrophotometry.

In order to determine the optimal diluent for the determination of Mg by atomic absorption spectrophotometry, the following diluents were tested: deionized water, 0.1 mol/l HCl, 2.5 g/l SrCl2, 1.8 g/l LaCl3, 17.7 g/l LaCl3, half-saturated 8-hydroxyquinoline (oxine), 40 g/l trichloroacetic acid (TCA)/17.7 g/l LaCl3, and 100 g/l TCA/0.1 mol/l HCl. The calibration curves, obtained on the same day, were passed through the origin in the form of linear regressions. The variances about the calibration curves did not differ significantly (p greater than 0.05), while the calibration slopes for the diluents differed significantly (p less than 0.001). A standard serum solution was analyzed with the use of the eight diluents and the mean results did not differ significantly (p greater than 0.05). The % coefficient of variation varied from 0.8 to 2.0 and the percent recovery ranged from 95.5 to 102.5. The 99% confidence interval (CI) ranged from 0.02 to 0.09. Since conventional CIs do not take into account the random error of the calibration curve, the inverse CI were also calculated for each diluent. On both the conventional estimates and on the inverse CI, strontium chloride gave the best results, but only marginally in view of the interassay variability of approximately 1%.

Calibration↗
PubMedDate not supplied

Characterization of nucleic acids by bichromatic paper disk spectrophotometry.

The bichromatic paper disk spectrophotometry ultramicromethod developed in the "Stefan S. Nicolau" Institute of Virology can be successfully applied to the study of viral and cellular nucleic acids. The main applications - succinctly presented in the review - refer to : the identification and spectral characterization of nucleic acids, their quantitative determination, the study of the helix - statistical coil transition, the evaluation of the degree of polymerization of single stranded polynucleotides, the study of the kinetics of chemical and enzymatic hydrolysis and the determination of RNase activity, e.g. in human serum, the demonstration of the interaction between nucleic acids and other molecules of biological interest (biopolymers, poly- and oligocations, etc.), the rapid characterization of the ion exchange capacity of chromatography papers and of a mobile phase of the water - alcohol - electrolyte type.

Chromatography, Paper↗
PubMed1978

Atomic absorption spectrophotometry of free circulating platinum species in plasma derived from cis-dichlorodiammineplatinum(II).

We describe a method of analysis for free circulating platinum species derived from cis-dichlorodiammineplatinum(II) in blood plasma. Protein-bound and free platinum species were separated from each other by centrifugal ultrafiltration. Platinum in the ultrafiltrate was converted to a cationic complex by reaction with ethylenediamine, and the product was collected on paper impregnated with cation-exchange resin, where it could be stored indefinitely without loss. The platinum was eluted from the disk with 5 mol/liter hydrochloric acid, and an aliquot of this solution was then analyzed by flameless atomic absorption spectrophotometry. The overall analytical recovery of platinum was 80 +/- 2%. The minimum quantity of cis-dichlorodiammineplatinum detectable was 35 microgram/liter of plasma at the 99% confidence level. Detector response was linearly related to drug concentration in the range from 80 microgram to 290 mg of Pt per liter of plasma. Reaction variables were made optimal, so as to yield maximum sensitivity and reproducibility (+/- 2%) consistent with minimal sample transfers and manipulations.

Cisplatin↗
PubMed1983

Determination of ultrafiltrable zinc in plasma by flameless atomic absorption spectrophotometry.

Ultrafiltrable zinc can be determined in small volumes of plasma by using Amicon ultrafiltration membrane cones and either flameless atomic absorption spectrophotometry or 65Zn. The ultrafiltration membrane cone is made sufficiently zinc-free by acid washing, followed by rinsing with de-ionized water. Within-run CVs were 12 and 10%, respectively, for the two methods. Matrix effects are compensated for by using standards in solutions with an inorganic matrix that simulates the sample matrix. Results for ultrafiltrable zinc by the two techniques agreed, and agreed with previously published data obtained by different ultrafiltration techniques. The mean (and SD) percentage of plasma zinc that was ultrafiltrable in 12 control subjects was 1.0 (0.5) by AAS and 0.7 (0.3) by 65Zn.

Humans↗
PubMed1983

[Assay of serum selenium by atomic absorption spectrophotometry. Value in the biological diagnosis of nonobstructive cardiomyopathies].

The authors present a technique of direct assay of serum selenium by atomic absorption spectrophotometry, using electrothermal atomization in a graphite oven. The initial results of the assays performed in patients with non-obstructive cardiomyopathies (NOCM) reveal a decrease in the serum selenium level. This element could therefore represent a laboratory marker for these diseases.

Cardiomyopathies↗