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PubMed2002

Comparison of UV derivative-spectrophotometry and partial least-squares (PLS-1) calibration for determination of methotrexate and leucovorin in biological fluids.

Binary mixtures of methotrexate (MTX) and leucovorin (LV) have been resolved by application of first-derivative spectrophotometry and partial least squares calibration (PLS-1). By measuring the first-derivative signals of MTX and LV at 354 and 300 nm, respectively, simultaneous determination was possible. The mean recoveries for urine samples were 91 and 96% for MTX and LV, respectively. Partial least squares (PLS-1) multivariate calibration has been applied to the determination of these compounds in serum and in urine without pretreatment of the samples. The absorption spectra of serum or urine samples spiked with methotrexate and/or leucovorin, were used to optimize the calibration matrixes by the PLS-1 method. The sensitivity and selectivity of the proposed procedures were calculated. Mean recoveries were 101 and 97% for MTX and LV, respectively, for serum samples, and 101 and 98% for MTX and LV, respectively, for urine samples.

Antimetabolites, Antineoplastic↗
PubMed2003

Simultaneous determination of domperidone and cinnarizine in a binary mixture using derivative spectrophotometry, partial least squares and principle component regression calibration.

This work is concerned with the simultaneous determination of domperidone maleate (DOM) and cinnarizine (CINN) in a binary mixture form, without previous separation, by two different techniques. The first method is the application of derivative spectrophotometry where the linearity range and percentage recoveries for DOM and CINN were 2.5-30 micro g mL(-1), 5-25 micro g mL(-1) and 100.06+/-1.157, 99.93+/-1.377, respectively. The second method depends on the application of partial least squares (PLS) and principle component regression (PCR) models. A training set consisting of 10 mixtures containing 5-20 micro g mL(-1) for each component was used for the construction of the PCR and PLS models. These models were used after their validation for the prediction of the concentration of DOM and CINN in their mixtures. The proposed procedures were successfully applied for the simultaneous determination of both drugs in laboratory prepared mixtures and in commercial tablet preparations. The validity of the proposed methods was assessed by applying the standard addition technique where the percentage recovery of the added standard was found to be 99.98+/-0.297 and 99.84+/-0.700 for DOM and CINN, respectively, using the derivative spectrophotometric method and 100.29+/-0.398 and 100.11+/-0.363 for DOM and CINN, respectively, using the PLS and PCR methods. The proposed procedures are rapid, simple, require no preliminary separation steps and can be used for routine analysis of both drugs in quality control laboratories.

Calibration↗
PubMed2004

Simultaneous determination of chlorophyll a and chlorophyll b by derivative spectrophotometry.

Chlorophyll a (Chl a) and chlorophyll b (Chl b) plant pigments, which are important in the food industry and are beneficial as environmental pollution indicators, have been extracted with a novel solvent mixture (1:1 v/v acetone-propanol) not containing chloroform and simultaneously determined by first-derivative spectrophotometry. The results were statistically compared to those obtained by the ordinary absorption spectrophotometric reference utilizing the principle of additivity of absorbances. The testing of the developed method in synthetic mixtures of Chl a and Chl b and in real plant material samples (grass, spinach, chard, purslane, black cabbage, crisp lettuce, rocket, dill and seaweed) proved successful in that the developed extractive derivative spectrophotometric method was both rapid and precise, and was not dependent on the Chl a/b ratio in contrast to the reference method which was adversely affected by the latter parameter.

Calibration↗
PubMed1997

The effect of blood transfusion and haemodilution on cerebral oxygenation and haemodynamics in newborn infants investigated by near infrared spectrophotometry.

UNLABELLED: The objective of this study was to investigate the influence of blood transfusion and haemodilution on cerebral oxygenation and haemodynamics in relation to changes in cerebral blood flow velocity (CBFV) and other relevant physiological variables in newborn infants. Thirteen preterm infants with anaemia (haematocrit < 0.33) and ten infants with polycythaemia (haematocrit > 0.65) were studied during blood transfusion and haemodilution respectively using adult red blood cells and partial plasma exchange transfusion. Changes in cerebral concentrations of oxyhaemoglobin (cO2Hb), deoxyhaemoglobin (cHHb), total haemoglobin (ctHb), (oxidized-reduced) cytochrome aa3 (cCyt.-aa3) were continuously measured using near infrared spectrophotometry throughout the whole procedure. Simultaneously, changes of mean CBFV in the internal carotid artery were continuously measured using pulsed Doppler ultrasound. Heart rate, transcutaneous partial pressure of oxygen and carbon dioxide, and arterial O2 saturation were continuously and simultaneously measured. Blood transfusion resulted in increase of cO2Hb, cHHb, ctHb and red cell transport (product of CBFV and haematocrit), whereas CBFV decreased. The increase of cO2Hb exceeded that of cHHb, reflecting improvement of cerebral O2 supply. Haemodilution resulted in a decrease of cO2Hb, cHHb and ctHb, whereas CBFV increased. Red cell transport was unchanged. The decrease of cO2Hb exceeded that of cHHb, reflecting decreased cerebral O2 supply. cCyt.aa3 decreased after blood transfusion and remained unchanged after haemodilution, but the reliability of these results is uncertain. With the exception of a small, but significant increase in transcutaneous partial pressure of oxygen after blood transfusion, the other variables showed no changes. Each blood withdrawal during exchange transfusion resulted in only a significant increase in heart rate without changes in the other variables measured, suggesting unchanged cerebral perfusion. CONCLUSION: In newborn infants blood transfusion in anaemia results in improvement of cerebral oxygenation, but haemodilution in polycythaemia does not improve cerebral oxygenation despite possible improvement of cerebral perfusion.

Anemia↗
PubMed1998

Rectal mucosal hemodynamics, evaluated by reflectance spectrophotometry, in patients with chronic hepatitis.

To evaluate rectal mucosal hemodynamics in patients with chronic hepatitis, we employed reflectance spectrophotometry and examined the results in relation to the presence and severity of chronic hepatitis. Twenty-six patients with histologically diagnosed chronic hepatitis and 21 controls were examined for rectal vascular findings by endoscopy. Indices (I) of rectal mucosal oxygen saturation (ISO2) and rectal mucosal hemoglobin (IHb) concentration were measured. To minimize the effects of systemic anemia, the IHb was divided by blood Hb concentration, giving the rectal index for Hb (RHb). The relationship between rectal mucosal hemodynamics and the histological grade of chronic hepatitis was studied. Rectal vascular lesions were observed in three patients with chronic hepatitis (11.5%). The RHb in patients with chronic hepatitis was significantly higher than that in the controls (5.74 +/- 0.71 and 4.82 +/- 1.12, respectively; P < 0.01). There was no significant difference in ISO2 levels (44.23 +/- 5.84 and 41.94 +/- 4.91, respectively). No significant correlation was observed between rectal mucosal hemodynamics and the histological severity of chronic hepatitis, although rectal mucosal hemodynamics changed in patients with chronic hepatitis. Early vascular changes were observed in the rectal mucosa of patients with chronic hepatitis.

Adult↗
PubMed2005

[Simultaneous noninvasive monitoring for radial forearm and fibula flaps using laser Doppler flowmetry and tissue spectrophotometry].

AIM: In the literature currently available monitoring devices are usually divided into two major groups: those for monitoring perfusion and those for measuring tissue oxygenation. The O(2)C (oxygen to see) system combines these two ways of monitoring free flap viability. The aim of this prospective study was to determine the necessity of flap revision and when unnecessary revision can be avoided. Another point of interest was the question of whether critical values for the successful course of free flaps could be defined and in addition whether such values would differ for different flap types. PATIENTS AND METHODS: In a prospective study 82 free flaps (61 radial forearm flaps and 21 fibula flaps) were monitored with the O(2)C monitoring unit. Measurements were carried out intraoperatively and postoperatively up to 14 days. RESULTS: Perfusion compromise occurred in 12 (14.6%) of 82 monitored free flaps. Operative exploration was performed in seven cases, in five of them successfully. Five flaps (three radial forearm and two fibula flaps) were lost due to vascular compromise, which led to an overall success rate of 93.4%. Venous congestion was identified by a rapid increase in hemoglobin concentration of more than 30%. An abrupt decline of blood flow and hemoglobin oxygenation indicated arterial occlusion. Vascular complications were detected in all cases prior to clinical assessment with no false positive or negative results. For radial forearm flaps a hemoglobin oxygenation of 15%, a superficial flow of 10 AU, and a deep flow of 20 AU were identified as minimum values for flap viability. For fibula flaps a hemoglobin oxygenation of 10%, a superficial flow of 5 AU, and a deep flow of 15 AU were determined as minimum values. CONCLUSION: O(2)C combines laser Doppler flowmetry and tissue spectrophotometry and for the first time allows simultaneous measurement of the microcirculatory parameters including blood flow, flow velocity, hemoglobin concentration, and hemoglobin oxygenation. We found this new noninvasive technique to be a reliable and accurate method for evaluating flap viability and improving the success rate in free flap transfer.

Adolescent↗
PubMed1984

Determination of unsaturated glycosaminoglycan disaccharides by spectrophotometry on thin-layer chromatographic plates.

Chondroitin sulfate isomers and hyaluronate, digested with chondroitinase AC II and separated as unsaturated disaccharides by thin-layer chromatography on cellulose, were quantitated with scanning spectrophotometry using reflectance measurement at 232 nm. The sensitivity of the assay was increased by one order of magnitude as compared to previous modifications of the disaccharide analysis on cellulose. The method allowed quantitation of 0.2-20 micrograms of glycosaminoglycan uronic acid. Since the elution of the disaccharides from the plate could be omitted, the speed and reproducibility of the assay was enhanced.

Animals↗
PubMed1985

Quantitation of zinc in nitric acid-digested plasma by atomic absorption spectrophotometry.

Human plasma, digested in a screw-capped Teflon vial for 1 h at 130 degrees C in concentrated nitric acid, is assayed for zinc by atomic absorption spectrophotometry using a single-slot, 10-cm burner and air/acetylene flame. The assay is linear to 10.00 mg Zn/liter, recovery averages 100.9%, and inter- and intraassay coefficients of variation are 5.9 and 1.9%. With this method, there is no burner clogging or adjustment necessary for sample viscosity. Sodium chloride does not interfere with the assay. The linear regression data of the standard curve for milligrams of Zn per liter (x) and milliabsorbance units (y) is y = 40x + 0.001.

Humans↗
PubMed1985

Quantitative determination by derivative spectrophotometry of Triton X-100 in solubilized preparations of membrane proteins.

The amount of the nonionic detergent Triton X-100 in protein preparations cannot be determined spectrophotometrically from the normal spectrum because the spectral bands of the detergent and proteins overlap, but it was found that the detergent could be determined accurately by 4th-derivative spectrophotometry. The intensity of the derivative absorbance difference between the positive and negative peaks at about 277.5 and 281 nm, respectively, increased linearly with increase in the detergent concentration at more than its critical micelle concentration (about 0.03%). Proteins had little effect on these spectral bands of the detergent. This method is very simple and accurate for determination of the concentration of Triton X-100 in solubilized preparations of membrane proteins.

Animals↗
PubMed1986

Separation and quantitation of metallothioneins by high-performance liquid chromatography coupled with atomic absorption spectrophotometry.

A rapid, reproducible, and sensitive high-performance liquid chromatography (HPLC) method for the determination of the concentrations of metallothionein-I (MT-I) and metallothionein-II (MT-II) in rat liver has been developed. Metallothioneins (MTs) were separated and quantitated by anion-exchange high-performance liquid chromatography coupled with atomic absorption spectrophotometry (AAS). Purified rat liver MT-I and MT-II, used as standards for developing the method, were easily resolved, eluting at 7.5 and 10.4 min, respectively. To establish standard curves, protein concentrations of solutions of the purified MTs were determined by the Kjeldahl method for the determination of nitrogen, after which the standards were saturated with Cd (final concentration of 50 ppm Cd). Rat liver cytosols obtained from untreated and Cd- or Zn-treated rats were prepared for HPLC-AAS analysis by saturation with Cd (50 ppm Cd) followed by heat denaturation (placing in a boiling water bath for 1 min). Based on the method of standard additions, recovery of MTs exceeded 95% and repeated injection of a sample yielded a coefficient of variance of approximately 2%. A detection limit of 5 micrograms MT/g liver was established for the method. Only MT-II was detected in untreated rats, whereas following exposure to Cd or Zn, both forms of MTs were detected. Concentrations of total MTs in liver of untreated and Cd- or Zn-treated rats were also determined by the Cd/hemoglobin radioassay (which fails to distinguish MT-I from MT-II) and indicated that results obtained with the HPLC-AAS method compared favorably to the Cd/hemoglobin radioassay. Thus, the HPLC-AAS method for quantitating MT-I and MT-II offers the advantage of determining the concentrations of both proteins in tissues and should be useful for studying the regulation of MT-I and MT-II.

Animals↗
PubMed1981

Hemoperfusion, rate of oxygen consumption and redox levels of mitochondrial cytochrome c (+c1) in liver in situ of anesthetized rat measured by reflectance spectrophotometry.

Utilizing reflectance spectrophotometry, hemoperfusion, rate of oxygen consumption and redox level of mitochondrial cytochrome c (+c1) in livers in situ of anesthetized rats were measured. The transition to the anoxic state was induced by raising the pressure on the liver surface to more than the hepatic blood pressure by pressing with the tip of the optical guide of the reflectance spectrophotometer. During this transition, the average oxygen saturation of hemoglobin in the liver in situ decreased linearly with time until it became 10--20% of the total. This was followed by reduction of mitochondrial cytochrome c (+c1), which reached completion in 10--20 s. The measured O2 consumption rate remained constant until the percentage of oxyhemoglobin in situ decreased to a critical level. There was then a decrease in the rate of O2 consumption which was accompanied by a progressive reduction of cytochrome c (+c1). It was shown that amounts of hemoglobin and mitochondrial respiratory chain cytochromes in the liver in situ could be measured non-invasively and could provide important signals for vital cellular functions. The changes in hemoperfusion and rate of O2 consumption of the liver in situ following ethanol ingestion were also shown in rats, and are briefly discussed with respect to possible application of this method to study the pathophysiology of tissues.

Animals↗
PubMed1988

Membrane-buffer partition coefficients of tetracaine for liquid-crystal and solid-gel membranes estimated by direct ultraviolet spectrophotometry.

The membrane-buffer partition coefficient of tetracaine was measured by direct ultraviolet spectrophotometry in dimyristoylphosphatidylcholine unilamellar liposomes at temperatures above and below the main phase transition. The partition coefficients of uncharged tetracaine to solid-gel (18 degrees C) and liquid-crystal (30 degrees C) membranes were 6.9 x 10(4) and 1.2 x 10(5), respectively. Despite the general assumption that local anesthetic binding to the solid membrane is negligible, this study showed that the solid membrane binding amounts to 57.5% of the liquid membrane binding. Binding of the charged form to the liquid or solid membrane was not detectable under the present experimental condition of 0.03 mM tetracaine bulk concentration. The present method measures metachromasia of local anesthetics when bound to lipid membranes. Its advantage is that the separation of the vesicles from the solution is not required. A linearized equation is presented that estimates the partition coefficient or binding constant graphically from a linear plot of the absorbance data. The method is applicable for estimation of drug partition when a measurable spectral change occurs due to complex formation.

Buffers↗
PubMed1985

Dissociation kinetics of DNA-anthracycline and DNA-anthraquinone complexes determined by stopped-flow spectrophotometry.

The first order rate constants for the dissociation of daunorubicin, doxorubicin, and 1-; 1,4-; 1,5-; and 1,8-; N,N-diethylaminoethylamino-substituted anthraquinones from calf thymus DNA were determined using stopped-flow spectrophotometry. Sodium dodecyl sulphate was used to disrupt the equilibrium. In all cases there was an increase in the rate constant with temperature. The dissociation rate constants at 20 degrees, 25 degrees and 37 degrees, were in the order 1-; much greater than 1,8-; greater than 1,4-; greater than daunorubicin and doxorubicin greater than 1,5-disubstituted anthraquinone. The 1,5-disubstituted anthraquinone (VII) thus shows the slowest rate of dissociation from DNA; the DNA complex dissociating more slowly than the DNA complexes of the anthracyclines, daunorubicin and doxorubicin. The result is consistent with the data from computer graphics modelling studies [39] which show that DNA-breathing (transient base pair unstacking) has to occur to allow the docking of the 1,5-disubstituted anthraquinone (VII) into the receptor site. Hence once the 1,5-disubstituted anthraquinone molecule has intercalated into DNA, DNA-breathing is required before dissociation can take place. This is not necessary with the other compounds (though the 1,4-disubstituted anthraquinone (V) can bind in this manner as well). So the very slow dissociation of the DNA/1,5-disubstituted anthraquinone complex relative to that of the DNA complexes of the other compounds examined here, supports the proposed mode of binding [39].

Anthraquinones↗
PubMed1993

Dynamic changes in cerebral oxygenation in chemically induced seizures in rats: study by near-infrared spectrophotometry.

Using near-infrared spectrophotometry, the redox state of copper in cytochrome oxidase, and the hemoglobin oxygenation state were measured in the rat brain in situ during and after chemically induced seizures. Pentylentetrazol (PTZ) administration caused the partial reduction of cytochrome oxidase in the brain just before the electroencephalogram (EEG) showed desynchronization, and then blood pressure was elevated concomitantly with an increase in cerebral blood volume. When blood pressure reached a maximum, bursts of spikes appeared on the EEG and cytochrome oxidase was reoxidized to reach the initial oxidation level, giving a rapid, transient reduction of cytochrome oxidase in the preictal period. Hemoglobin was more oxygenated than before the administration throughout the seizure. In the late postictal phase, cytochrome oxidase was partially reduced again, while blood pressure remained high and hemoglobin was more oxygenated than initially. The second administration of PTZ in the late postictal phase induced the same responses as observed after the first administration. By decreasing oxygen concentrations in the inspired gas during the seizure, cytochrome oxidase was more reduced than in the non-epileptic rat, and spike activity was observed until about 85% of cytochrome oxidase was reduced. The transient cerebral hypoxia reflected by the reduction of cytochrome oxidase in the preictal period may be a trigger for an increase in cerebral blood flow rather than the result of a delayed autonomic response. The second reduction of cytochrome oxidase observed in the late postictal phase may be due to a lasting arterio-venous shunt that opens during seizures. These results revive the classical theory that cellular hypoxia is responsible for epileptic brain damage.

Animals↗
PubMed1975

[Determination of bismuth in blood urine and cerebrospinal fluid by flameless atomic absorption spectrophotometry (author's transl)].

A method for the determination of bismuth in blood, urine and cerebrospinal fluid is described. Using ammonium pyrrolidine dithiocarbamate as chelating agent, bismuth is extracted in hexane and determined by flameless atomic absorption spectrophotometry with a graphite furnace. A sample of 0.5 ml is sufficient for the determination of bismuth at concentrations ranging from a few mug/l to 2000 mug/l. In subjects not receiving bismuth, the concentration in blood is below 10 mug/l and in subjects intoxicated with bismuth prescribed for digestive diseases the concentration can reach 2000 mug/l and more.

Bismuth↗
PubMed1976

Determination of oxalic acid in urine by atomic absorption spectrophotometry.

A method is described for determination of oxalic acid in urine using atomic absorption spectrophotometry. The concentration of urinary oxalic acid is calculated by using the difference between two determinations of calcium: first, the excess of calcium in the supernatant after precipitation as calcium oxalate at pH 5, and second, the total calcium determined at pH less than 1 (endogenous and added). Analytical parameters (pH of precipitation, temperature, calcium and oxalate added, precipitation time, interfering substances) were studied with the aid of [14C]oxalic acid. A constant recovery of 95% of total oxalic acid allows the use of a correction factor. The accuracy and reproducibility of the method make it useful for routine determination of urinary oxalic acid.

Evaluation Studies as Topic↗
PubMed1976

Determination of manganese in blood and urine by flameless atomic absorption spectrophotometry.

A method for the determination of manganese in blood and urine is described. A chelate fo manganese with cupferron is extracted with methylisobutylketone and determined by flameless atomic absorption spectrophotometry. The method is directly applicable to urine but the determination of manganese in blood required a preliminary digestion step. With the use of internal standards, this technique allows the determination of manganese concentrations of the order of 1 mug/1 of urine or 1 mug/100 ml whole blood.

Humans↗
PubMed1977

Differential spectrophotometry for the determination of serum methemalbumin.

A method for the direct determination of methemalbumin in serum by means of difference scanning spectrophotometry is described. The advantages of this quantification technique resides in the ability to obviate unequal background characteristics such as turbidity in one treated sample portion, the avoidance of subtractive measurement on the sides of steep spectra, and a qualitative observation simultaneously derived from the single difference scan. A measure of the stability of the prepared standards is described along with a minimized use of sample and reagent volumes if the latter is desired.

Hemeproteins↗