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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↗
PubMed2003

Second and first-derivative spectrophotometry for efficient simultaneous and individual determination of palladium and cobalt using 1-(2-pyridylazo)-2-naphthol in sodium dodecylsulfate micellar media.

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous and individual determination of palladium and cobalt at trace levels. PAN complexes of palladium and cobalt at neutral pH form green-color neutral complexes, which are soluble in aqueous SDS micellar media. Under optimum conditions, calibration graphs for individual determinations by zero and first-derivative spectrophotometry, and also for simultaneous determinations by second-derivative spectrophotometry were obtained. A zero-crossing method using second-derivative spectrophotometry at 628 or 578 and 614 nm, respectively, for cobalt and palladium was used for simultaneous determinations. The method is able to determine the cobalt-to-palladium ratio, 5:1 to 1:10 (Wt/Wt), accurately. The accuracy and reproducibility of the determination method for various known amounts of cobalt and palladium in their binary mixtures were tested. The effects of diverse ions on the determination of cobalt and palladium to investigate the selectivity of the method were also studied. The recommended procedures were applied to a synthetic binary alloy, cobalt in vitamin B12 and B-complex ampoules, a Co2O3-Co3O4 laboratorial chemical mixture, some synthetic cobalt-alloy samples, a Pd-charcoal catalyst, and some synthetic palladium alloys.

Alloys↗
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↗
PubMed2006

A detailed study of thermal decomposition, amalgamation/ atomic absorption spectrophotometry methodology for the quantitative analysis of mercury in fish and hair.

The analytical method for determining the concentration of mercury in fish by thermal decomposition, amalgamation/ atomic absorption spectrophotometry was thoroughly studied. Specific issues addressed were accurate modeling of instrumental response, the use of quartz and nickel boats, carryover effects, software limitations, and troubleshooting. The DMA-80 Direct Mercury Analyzer instrument was calibrated using a total of 22 points, and the resultant curves statistically analyzed. At minimum, second-order polynomials were required to adequately model the data. TORT-2 standard reference material was analyzed in both quartz and nickel boats and found to give equivalent performance in both types of vessels and well within the 95% confidence interval. DOLT-3 standard reference material also yielded values well within the 95% confidence interval, but the DORM-2 standard reference material did not. Carryover effects were found to be minimal with a new catalyst tube but increased with catalyst age. Blanks should be run after the analysis of high mercury content samples; however, when the catalyst has aged, two blanks are required to reduce apparent mercury signals to nominal blank values. Comparable results between thermal decomposition, amalgamation/atomic absorption spectrophotometry and cold-vapor atomic absorption spectrophotometry were demonstrated. The feasibility of using this instrument to analyze hair was also explored and found to be suitable. Software problems and limitations have been noted when attempting to implement a high-throughput methodology. Instrumental drift was found to be minimal when operated over long periods. Blank values can provide important diagnostic indicators.

Animals↗
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↗
PubMedDate not supplied

[Determination of glutathione with the GSH-400 method: value of derivative spectrophotometry].

The GSH-400 method (Oxis International SA) performed in acid supernatant, provides an assay of reduced glutathione (L-gamma-glutamyl-L-cysteinylglycine) (GSH) in biological samples by a two step chemical reaction followed by a spectrophotometric detection. We improved the analytical performances of the assay by using derivative spectrophotometry (delta). The second order derivative (delta 2) spectrophotometry gave identical signals with either a GSH standard solution or a erythrocyte lysate containing the same amount of GSH, whereas the corresponding absorbances (Abs.) were different. The linearity range of the method was 20 to 2,000 mumol/l. Detection limit (DL) was not modified with derivative spectrophotometry (DL Abs. = 7 mumol/l; DL delta 2 = 12 mumol/l). The GSH-400 method was not suitable for plasma GSH determination. Erythrocyte GSH concentrations (M +/- SD) in 23 healthy subjects (8 men, 15 women, median age 36) obtained with absorbance measurements (2.66 +/- 0.60 mmol/l) were significantly higher than those obtained with delta 2 (2.30 +/- 0.41 mmol/l) (p < 0.001). Erythrocyte lysate storage at -20 degrees C did not lead to satisfactory conservation (65% decrease of the GSH concentration in erythrocytes after 15 days freezing). The derivative spectrophotometric detection improved analytical performances of GSH-400 method, when compared to the absorbance measurement at 400 nm.

Adult↗
PubMed2000

Near infrared spectrophotometry for the diagnosis of vasculogenic erectile dysfunction.

A specialized near infrared spectrophotometry instrument for noninvasive, continuous monitoring of the hemodynamic events of erection in the human penis has been developed. Its potential application for the diagnostic evaluation of erectile dysfunction was investigated. Thirty-eight patients and 18 volunteer subjects underwent penile near infrared spectrophotometry using an optical sensor probe with wavelength selectivity for hemoglobin absorption spectra. Penile blood volume changes and their time courses were measured following intracavernous pharmacostimulation in patients and visual sexual stimulation in volunteers. Spectrophotometric results were compared with results obtained simultaneously using color duplex ultrasonography, strain gauge penile circumference monitoring, penile tonometry, and clinical assessments. Spectrophotometric recordings of penile erection showed measurable blood volume changes consistent with the hemodynamic events of this biological function. Blood volume per cent (BV%) increase correlated with clinical ratings of erection quality (P < 0.001), penile rigidity measurements (P < 0.005), and penile circumference increases (P < 0.0001), and it correlated with mean peak systolic velocity measurements when BV% increase was restricted to values less than 50% (P < 0.001). The time to reach half the maximum blood volume change (BV T1) correlated directly with the time to reach half the maximum penile circumference size increase (P < 0.001), whereas BV T4 correlated inversely with mean resistive index measurements only when BV T(1/2) was restricted to values greater than 120 s (P < 0.05). Spectrophotometric criteria consisting of BV % less than 35% and BV T(1/2) greater than 120 s affirmed the diagnosis of severe erectile impairment with a similar degree of accuracy as standard ultrasonographic criteria (P < 0.002). Penile near infrared spectrophotometry is a safe, inexpensive and simply used biomedical optics technique that provides quantitative measurements of the vascular physiology of penile erection and appears to offer clinical utility in the diagnosis of vasculogenic erectile dysfunction.

Adult↗
PubMed1999

Regional differences of cerebral hemoglobin concentration in preterm infants measured by near infrared spectrophotometry.

Near infrared spectrophotometry has been used to measure total cerebral hemoglobin concentration (micromol/l) as a major indicator of the oxygen transport capacity in neonates. The aim of this study was to find out how the position of the probe influences the quality of the measurement and the actual cerebral hemoglobin concentration-values. We studied 10 healthy preterm infants with a mean gestational age of 31.5 weeks and a birthweight of 1513 g. The data were collected by a two channel near infrared spectrophotometry system using a geometrical principle to measure absolute cerebral hemoglobin concentration. The incoming signal of the light emitting diode as a value allows a prediction of the quality of the measurement: a high value refers to a high signal/noise ratio. Starting from the centre of the forehead (0%) for each measurement the probe was moved by 2.5% of the headcircumference to the left respectively right side of the head up to 20%. The cerebral hemoglobin concentration-values increased from 87 respectively 93 micromol/l up to 164 respectively 173 micromol/l on the right respectively left side, while the light emitting diode signal-values decreased from 21 respectively 21 down to 10 respectively 11, the more laterally the probe was moved. There were two plateaus of these variables in the frontal (0-5%) respectively lateral (15-20%) region. A further investigation on a solid phantom for premature heads showed that hair has either no or a contrary effect on the cerebral hemoglobin concentration-values than expected. The extracerebral tissue (soft tissue, skull, cerebrospinal fluid layer) is discussed to have a significant influence on the light attenuation in adult heads. Still there is no evidence for a significant effect on prematures, because this overlying tissue is much thinner and more translucent than the one in adults. Absolute cerebral hemoglobin concentration measured by near infrared spectrophotometry is substantially influenced by the position of the probe at the infant's head. Considering our results we recommend placing the probe at 2.5% of the headcircumference away from the centre of the forehead for the measurement of cerebral hemoglobin concentration in premature infants.

Brain↗
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↗
PubMed1999

[Are ultraviolet and visible spectroscopy and spectrophotometry obsolete methods in pharmaceutical analysis?].

It has been investigated if UV-VIS spectroscopy and spectrophotometry can be regarded to be obsolete methods in pharmaceutical analysis. The conclusions are as follows. As a consequence of the introduction and spreading of highly efficient spectroscopic methods in the structural analysis of organic compounds the importance of UV-VIS spectroscopy as a structure elucidation tool has greatly decreased. At the same time, however, diode-array UV spectrophotometers used as HPLC detectors have created very convenient possibilities for the identification of minor components (impurities, degradation products, etc.) in drugs. This statement is illustrated by several practical examples. On the basis of some data taken from the British Pharmacopoeia 1998 it is stated that UV spectrophotometry as a quantitative analytical method still belongs to the most frequently used analytical techniques in pharmaceutical analysis. At the same time, however, the authors are of negative opinion about the up-to-dateness and usefulness of colorimetric methods still very often published for the determination of drug substances.

Colorimetry↗
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↗
PubMed1996

Oxygenation and blood volume changes in flaps according to near-infrared spectrophotometry.

OBJECTIVE: To test the ability of near-infrared spectrophotometry (NIRS) to predict vascular compromise in flaps postoperatively. DESIGN: Pilot study. SUBJECTS: Eleven denervated latissimus dorsi flaps were assessed in 8 pigs. INTERVENTIONS: Flaps were isolated on their vascular pedicle. We used NIRS to demonstrate tissue oxygen saturation and quantities of deoxygenated hemoglobin and oxygenated hemoglobin when flaps underwent venous or arterial occlusions. Oxygen saturation (percentage of oxygenated hemoglobin) was calculated as the difference between the 2 light intensities (860-750 nm) with the use of 2 time periods: preoperative (80%) oxygen saturation and during arterial occlusion (0%) oxygen saturation with NIRS. Blood volume changes within the flap were also measured. RESULTS: Arterial occlusion resulted in significant decreases in oxygen saturation and in blood volume with immediate recovery. Venous occlusion resulted in an initial rapid increase in blood volume with no appreciable early deoxygenation. CONCLUSIONS: Near-infrared spectrophotometry appears promising as a noninvasive, low-cost, portable bedside monitor that can demonstrate in real time changes in blood volume and oxygen saturation within a flap at a variety of tissue depths.

Animals↗
PubMedDate not supplied

Zero-crossing second derivative spectrophotometry for simultaneous determination of palladium and nickel using 1-(2-pyridylazo)-2-naphthol in mixed micellar solutions.

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous determination of nickel and palladium at trace levels. PAN complexes of nickel and palladium in the pH 1.98 form red and green colored complexes, respectively, which are soluble in aqueous 4:1 Triton X-100 to sodium dodecylsulfate (SDS) micellar media with total detergent concentration of 3.2%. Under optimum conditions, calibration graphs for the simultaneous determination by second derivative spectrophotometry were obtained. Zero crossing second derivative spectrophotometry at 668 and 572 nm, respectively for palladium and nickel was used for the simultaneous determination. The method is able to determine palladium to nickel ratio 70:1 to 1:6 (Wt/Wt), accurately. Accuracy and reproducibility of the determination method on the known various amounts of palladium and nickel in their binary mixtures were tested. Effects of diverse ions on the determination of palladium and nickel to investigate selectivity of the method also were studied.

Detergents↗
PubMed1995

Use of lightguide spectrophotometry to quantify skin oxygenation in a variable model of venous hypertension.

A variable model of venous hypertension was used to examine the immediate effect on skin oxygenation and blood flow. Measurements were carried out using laser Doppler flowmetry, transcutaneous oximetry and both macro- and micro-lightguide spectrophotometry to measure haemoglobin saturation (SO2). Assessments were performed on 20 normal subjects and in ten patients with deep venous insufficiency lying supine with a pressure cuff left uninflated (P0), then inflated to 40 mmHg (P40), 60 mmHg (P60) and 80 mmHg (P80). All measurements were performed at the gaiter area of the leg. In normal subjects median Doppler values fell significantly at P40 (P < 0.001) but further pressure increases had no more effect. Mean values of transcutaneous partial pressure of oxygen (PtcO2) fell steadily (P < 0.001), although the initial fall at P40 was small. Median SO2 fell with increasing occlusion pressure with both macro- and micro-lightguide spectrophotometry (P < 0.001), although the main reduction occurred predominantly at lower occlusion pressures. Higher levels of SO2 were obtained with local heating up to 44 degrees C, with a pattern similar to that of PtcO2. In patients, the same pattern of response to increased venous pressure occurred in areas of clinically normal skin. These data suggest that small increases in venous hypertension have an immediate and profound influence on skin blood flow and oxygen availability in normal skin.

Adult↗
PubMed2000

Use of stopped-flow spectrophotometry to establish midpoint potentials for redox proteins.

Stopped-flow spectrophotometry was examined as a tool to assign midpoint potentials to protein redox half-reactions. The method involves the rapid mixing of protein and electron transfer mediator solutions and the determination of the absorbance of at least one of the reacting species or products at equilibrium. The utility of the method was demonstrated with two different redox proteins (nitrogenase iron protein and cytochrome c) with very different midpoint potentials. The overall errors ranged from about +/-0.5 to 3 mV. Advantages of the method include short times required for the experiments, the precision and accuracy of the method in comparison to other methods, the conservative use of valuable protein in the experiments and the ease of obtaining midpoint potentials for redox protein half-reactions, and the potential range covered by a single electron transfer mediator when the method involves mediated electron transfer. It is concluded that the stopped-flow spectrophotometry should be considered the method of choice for determining protein midpoint potentials.

Adenosine Diphosphate↗
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↗
PubMed1997

[Microlight-guided spectrophotometry of the cochlea].

BACKGROUND: Intraoperative measurements of local intracapillary hemoglobin oxygenation of the human cochlea via the round window membrane have been shown to be possible using the Erlangen microlight-guided spectrophotometer. The aim of the present study was to develop a new microlight guide suitable for measurements in the round window niche and to evaluate electrophysiologically the possible impact of the procedure on the cochlea. METHODS: Measurements were made for wavelengths of 450 to 900 nm at a total power of 5.3 mW. The exit diameter of the light guide was 200 microns and the angle used was 20 degrees. The recording depth was about 250 microns. The atraumatic character of the spectrophotometry was demonstrated by monitoring the compound action potential (CAP) threshold tuning curve from 1 to 34 kHz in ketanest-anesthetized guinea pigs. RESULTS: CAP thresholds remained constant (0.3 +/- 3.9 dB SPL) during 3 to 30 min of exposure to the light. CONCLUSIONS: These results suggest that the spectrophotometry may be useful as a new technique for intraoperative monitoring of intracapillary hemoglobin without causing physiological deterioration of the cochlea.

Animals↗