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PubMedDate not supplied

Comparative sensitivities of flame atomic absorption spectrophotometry (AAS) and molecular absorption spectrophotometry (MAS).

A sensitivity comparison was made between conventional atomic absorption spectrophotometry (AAS) and conventional molecular absorption spectrophotometry (MAS) for the serum trace metals, copper, iron, and zinc. The sensitivity aspect considered was absorbances was obtained for concentrations in the solutions analyzed using unit lightpaths of 1 cm and 10 cm for MAS and AAS, respectively. A distinction was made between procedural sensitivity and measurement sensitivity where the latter represents molar absorptivity. Some was given to the concepts of procedural sensitization by concentration of the analyte through the use of lyophilization, extraction or ashing. The misuse of data obtained with scale expanders is described as a commonly occurring phenomenon of both AAS and MAS and a source of confusion in the understanding of measurement sensitivity.

Copper↗
PubMed1989

Continuous monitoring of gastroduodenal mucosal hemodynamics in rats by laser-Doppler flowmetry and reflectance spectrophotometry.

Gastroduodenal mucosal hemodynamics in rats was monitored continuously by laser-Doppler flowmetry (LDF) and reflectance spectrophotometry, and the validity of these techniques was determined. Corpus mucosal hemodynamics was recorded for 90 min, under stable conditions. In cases of graded hemorrhagic hypotension, corpus mucosal blood flow by LDF and hydrogen gas clearance, and potential differences showed a good correlation. Corpus, antral, and duodenal mucosal hemodynamics monitored by LDF, hydrogen gas clearance, and reflectance spectrophotometry reflected regional hemodynamic differences. In monitoring mucosal hemodynamics by LDF and reflectance spectrophotometry, regular oscillations (4-6 cycles/min) were observed in most animals. The characteristic change of oscillations during graded hemorrhagic hypotension was thus elucidated. In moderate hypotension (50-90 mmHg), high-amplitude and high-frequency (5-10 cycles/min) oscillations were observed, while in cases of severe hypotension (25-40 mmHg), the oscillations almost ceased. Observation of the oscillatory changes is thus a new application of LDF and reflectance spectrophotometry.

Animals↗
PubMed1991

The effect of white light exposure on the rabbit eye lens as measured by fluorophotometry and spectrophotometry.

Fluorophotometry and spectrophotometry of the rabbit lens were performed after white light exposure to detect possible changes in the lens before damage could be seen by biomicroscopic slit lamp examination. In nine rabbits the lens of one eye was exposed to white light and that of the fellow eye was used as a control. The incident light power was 240 mW for 90 min on a lenticular area of 3 mm2. Slit lamp examination of lens and cornea prior to, 1 hr after and 2 days after light exposure did not reveal any sign of damage. The mean in vivo autofluorescence ratio between exposed lens and non-exposed fellow lens was found to increase significantly from 1.0 +/- 0.08 S.D. (n = 9) before exposure to 3.3 +/- 0.8 S.D. (n = 9; P less than 0.004) 1 hr after exposure and hereafter to decay exponentially with a half time of 0.8 days to the ratio before exposure (correlation coefficient: -0.97, P = 0.0013). Three additional rabbits were exposed as described above with subsequent in vitro spectrophotometry of the lenses between 400 and 800 nm revealing an absorbance peak at 468 nm with a half width of 10 nm. The ratio between the absorbance peak of exposed lens and non-exposed fellow lens was found to increase from 1.1 before exposure to 2.8 1 hr after exposure and then to decrease to 1.4 at 1 day after exposure. The corresponding autofluorescence ratios measured in vivo before spectrophotometry were 0.93, 2.6 and 1.5, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

Heavy metal-nucleoside interactions. Binding of methylmercury(II) to inosine and catalysis of the isotopic exchange of the C-8 hydrogen studied by 1-H nuclear magnetic resonance and raman difference spectrophotometry.

Raman difference spectrophotometry reveals that CH3HgII binds quantitatively to N(1) of inosine at pH 8, substituting for the proton. When N(1) is saturated, binding occurs at a second site. Measurements of the 1-H nuclear magnetic resonance spectra of both inosine and of CH3Hg-II are in agreement with the N(1) binding and indicate that the second site for mercuriation is N(7). This second binding reaction is observed to increase the rate of exchange of the C(8) hydrogen with solvent, consistent with results observed for alkylation at N(7). Coordination of the electrophilic CH3Hg-II to N(7) increases the acidity of H(8), facilitating OHminus--catalyzed proton abstraction and reprotonation by themedium. For comparison, the reaction of CH3Hg-II with [8-2-H]inosine has been studied. Displacement of the N(1) hydrogen upon mercuriation of inosine causes a significant electron delocalization into the ring, increasing the basicity of N(7), and accounting for the synergic effect in metal binding observed originally by Simpson. In contrast, 1-methylinosine interacts only slightly with CH3Hg-II at pH 8. Coordination appears to be at N(7), since H(8) again is observed to exchange rapidly with solvent protons. In acidic solution, pH less than 2, binding to inosine is almost quantitative and exclusively to N(7). The behavior of CH3Hg-II is compared with that of Pt(II) and with Ni(II), Co(II), AND Zn(II). A brief comparison is made among ultraviolet absorption spectrophotometry, nuclear magnetic resonance (NMR), and Raman difference spectrophotometry for studying reactions of nucleosides and nucleotides.

Binding Sites↗
PubMed1975

Computer tomography compared with spectrophotometry of cerebrospinal fluid in cerebrovascular diseases.

Eighty patients with cerebrovascular diseases were examined by computer tomography and spectrophotometry of CSF, most cases being followed by repeat examinations. Specific diagnoses were obtained in 76 per cent of the cases at tomography and in 95 per cent at spectrophotometry, generally at one examination. In cases examined angiographically or by isotope encephalography, the corresponding figures were 60 and 58 per cent. Twenty patients with confirmed haemorrhage or infarction examined only at tomography further indicated the high diagnostic significance of this method. The combination of tomography and spectrophotometry, being complementary to each other, obviously means a break-through in the diagnosis of cerebrovascular diseases, which is a prerequisite for a more rational therapy of these common and frequently disabling disorders.

Brain↗
PubMed1978

Computer tomography of the brain and spectrophotometry of the CSF in cerebral concussion and contusion.

Computer tomography (CT) and spectrophotometry of CSF were performed in 30 patients with the clinical diagnosis of cerebral concussion or contusion. The patients with concussion all had normal CT-findings. Spectrophotometry of CSF was sometimes positive for cerebral contusion with normal CT-findings, but the two methods were complementary so that the extent of the lesion was determined by CT and spectrophotometry of CSF indicated the cause.

Brain Concussion↗
PubMed1991

Determination of serum acetaminophen in emergency toxicology: evaluation of newer methods: Abbott TDx and second derivative ultraviolet spectrophotometry.

Newer methods for the determination of serum acetaminophen in emergency toxicology, the Abbott TDx immunoassay and second derivative ultraviolet spectrophotometry, were evaluated and compared to a high pressure liquid chromatographic procedure. The Abbott TDx immunoassay within-run and day to day precision yielded coefficients of variance below 2.7% and 7.2% respectively: Abbott TDx immunoassay results correlated well with those of high pressure liquid chromatographic in patient serums 15.0 to 333 mg/L acetaminophen; r2 = 0.954, n = 40. The Abbott TDx immunoassay assay was rapid, easy to perform, free of interferences from other drugs and exhibited no carryover from previous samples. The within run precision of the second derivative ultraviolet spectrophotometry method yielded coefficients of variance of less than 7.0%. Second derivative ultraviolet spectrophotometry results demonstrated good correlation with high pressure liquid chromatographic results in patient sera; r2 = 0.923, n = 40; however, performance deteriorated below 50.0 mg/L acetaminophen. Spectral interferences were noted at high concentrations of some drugs.

Acetaminophen↗
PubMed1991

[Determination of trimethoprim and sulfamethoxazole in pharmaceutical preparations by non-relative component reference-multiplier derivative spectrophotometry].

This paper provides the basic principle and experimental technique of non-relative component reference-multiplier derivative spectrophotometry. The procedure overcomes the problem of overlapping in derivative spectrophotometry and quantitative analysis of lower content component in mixture can be done without separation. This method was investigated to assay the contents of trimethoprim (TMP) and used to assay the zero crossing derivative spectrophotometry for the assay of sulfamethoxazole (SMZ) in pharmaceutical preparations. The average recoveries of TMP and SMZ were 102.5 +/- 1.63% (CV) and 100.3 +/- 0.99% (CV) respectively. The results show that it not only can effectively remove the interference from each other, but also give a higher sensitivity and accuracy.

Drug Combinations↗
PubMed1985

Comparison of liposome entrapment parameters by optical and atomic absorption spectrophotometry.

Methods for the complete characterization of liposomes prepared by ether-injection are described in detail. The validity of atomic absorption spectrophotometry for measuring markers of trapped volume was checked by comparative determinations of markers with established optical spectrophotometrical methods. The favorable results using atomic absorption spectrophotometry to quantitate the marker Mn2+ are of particular relevance as manganese ion is also the paramagnetic probe in n.m.r. measurements of water permeability of liposomes; our results indicate that in such measurements no other marker need be incorporated.

Liposomes↗
PubMed1987

[Diagnostic value of cerebrospinal fluid spectrophotometry in acute cerebral circulatory disorders].

The direct spectrophotometry of the cerebrospinal fluid (CSF) is recommended as an auxiliary method for differential diagnosis in patients with acute cerebrovascular disorders. Using both literature data and their own findings the authors have developed the scheme of spectrophotometry of the CSF which includes measuring the optic density in 265, 280, 365, 400, 415, 450, 460, 530 and 540 nm. This measuring in 9 ranges makes it possible to identify the character of the illness without analyzing the optic density in the full spectrum of ultraviolet and visible light.

Acute Disease↗
PubMed1990

Effect of submucosal epinephrine injection on local gastric blood flow. A study using laser Doppler flowmetry and reflectance spectrophotometry.

Clinical studies have demonstrated the efficacy of submucosal epinephrine injection in the control of bleeding ulcers. Since endoscopic techniques for assessing gastroduodenal blood flow are limited, we employed an animal model to study the mechanism of control of bleeding. The effect of submucosal epinephrine injection on local gastric blood flow was studied in the rat using laser Doppler flowmetry and reflectance spectrophotometry. Submucosal injection of 0.1 ml of 1/10,000 epinephrine caused a significantly greater drop in local gastric blood flow (laser Doppler flowmetry) compared with vehicle (10% sodium metabisulfite) injection. The reduction persisted for up to 120 min. This vasoconstrictive effect of epinephrine was confirmed by observations with reflectance spectrophotometry, which documented a pattern of ischemia without congestion (lower index of hemoglobin concentration, lower index of oxygen saturation). The autoregulatory escape from adrenergic vasoconstriction was not evident in either instance. We conclude that, after submucosal injection of epinephrine, the absence of autoregulatory escape from adrenergic vasoconstriction and the marked and prolonged decrease in local gastric blood flow enhance the homeostatic mechanisms (eg, platelets and other coagulative factors) to effect hemostasis in bleeding ulcers.

Animals↗
PubMed1991

Experimental studies on the prediction and prevention of stress ulcers using tonometry, reflectance spectrophotometry and oxygenated perfluorochemicals.

The present study investigates whether oxygenated perfluorochemicals protect the gastric mucosa against hemorrhage-induced stress ulceration. The influence of oxygenated perfluorochemicals on both macroscopic and microscopic lesion formation, gastric intramural pH, index of oxygen saturation and index of hemoglobin saturation of the gastric mucosa was studied. To assess the severity of gastric mucosal ischemia, intramural pH was directly measured using a pH sensitive microelectrode and indirectly by utilizing hollow viscus tonometry, and the indices of oxygen saturation and hemoglobin saturation were measured by reflectance spectrophotometry. Oxygenated perfluorochemicals (30 ml/kg/h) significantly protected the gastric mucosa against both gross (lesion index 0.85 +/- 0.2 vs 2.23 +/- 0.31) and microscopic (lesion index 0.52 +/- 0.02 vs 2.04 +/- 0.03) injuries. This protection was associated with a significantly decreased acidification of the mucosa during shock (intramural pH 7.24 +/- 0.02 vs 6.97 +/- 0.02) and significantly increased oxygen saturation of the gastric mucosa (30 +/- 6 vs 5 +/- 2). These data indicate that topical oxygenated perfluorochemicals protect the gastric mucosa against mucosal damage provoked by hemorrhagic shock, and this protection seems to be mediated by an increased oxygen saturation of the gastric mucosa. Tonometry and reflectance spectrophotometry thus are able to predict the critical level of gastric mucosal ischemia.

Animals↗
PubMed1988

Rapid determination of kinetic constants by competitive spectrophotometry.

The use of competitive spectrophotometry to measure kinetic constants for enzyme-catalyzed reactions is described. The equation for the progress curve characterizing the kinetic behavior of an enzyme acting simultaneously on two alternative substrates is derived. By the addition of a competition term to the integrated Michaelis-Menten equation, the kinetic constants of an alternative substrate can be evaluated by measuring the competition with a substrate of known kinetic constants in a single experiment. Studies are presented involving the enzymes leucine aminopeptidase (LAP) and carboxypeptidase A (CPA). The results obtained with LAP and CPA showed that the kinetic constants determined using competitive spectrophotometry were in agreement with values cited in the literature or with values determined by single substrate enzyme kinetics.

Binding, Competitive↗
PubMed1990

Determination of tryptophan, tyrosine, and phenylalanine by second derivative spectrophotometry.

Second derivative spectrophotometry has been useful for the determination of aromatic amino acids. However, published methods produce erroneous results, because those methods measure second derivative values by the vertical distance between peak and trough which is subject to variation according to the aromatic amino acid composition of proteins. This paper presents a method of second derivative spectrophotometry which measures second derivative absorbance values by means of the vertical distance from baseline to the derivative curve at a wavelength specifically assigned to each aromatic amino acid, and makes corrections for the interference from other amino acids at the same wavelength. The Appendix describes a computational method for obtaining absolute values of second derivative absorbances directly from normal absorbance values without using the spectrophotometer's derivative mode, because most commercial instruments produce completely arbitrary second derivative values which make comparison of data obtained on two different instruments impossible.

Humans↗
PubMed1976

Differentiation between chelated and non-chelated DNA-Pt complexes by atomic absorption spectrophotometry.

As a continuation of our study of the properties of the cis-trans platinum series we have investigated the DNA-Pt complexes of [Pt(dien)Cl]Cl, cis-Pt (en)Cl2, cis-Pt (NH3)2Cl2 and K2[PtCl4] by atomic absorption spectrophotometry. The DNA-Pt complexes correspond to the saturation of the N7-(Guanine) sites. It has been found that the chelate complexes obtained with cis-Pt(en)Cl2, cis-Pt(NH3)2Cl1 and K2[PtCl4] show the same absorbance. The [Pt(dien)Cl]Cl and trans-Pt (NH3)2Cl2 which are bound to the N7 (tuanine) site only, show an absorbance greater than the chelate complexes by a factor of two. In addition, it has been possible in the case of the trans-Pt (NH3)CCl1 complex to follow the fixation of platinum to DNA by atomic absorption spectrophotometry. The result is similar to the ionic chlorine liberation procedure reported previously.

Binding Sites↗