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PubMed2001

Application of LC and HPTLC-densitometry for the simultaneous determination of benazepril hydrochloride and hydrochlorothiazide.

Two methods are described for the simultaneous determination of benazepril HCl and hydrochlorothiazide in binary mixture. The first method was based on HPTLC separation of the two drugs followed by densitometric measurements of their spots at 238 and 275 nm for benazepril HCl and hydrochlorothiazide, respectively. The separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F(254,) using ethyl acetate-methanol-chloroform (10:3:2 v/v) as mobile phase. Second order polynomial equation was used for the regression line in the range 2-20 and 2.5-25 microg/spot for benazepril HCl and hydrochlorothiazide, respectively. The second method was based on HPLC separation of the two drugs on reversed phase, ODS column at ambient temperature using a mobile phase consisting of acetonitrile and water (35:65 v/v) and adjusting to pH 3.3 with acetic acid. Quantitation was achieved with UV detection at 240 nm based on peak area with linear calibration curves at concentration ranges 10-60 and 12.5-75 microg ml(-1) for benazepril HCl and hydrochlorothiazide, respectively. The two proposed methods were successfully applied to the determination of both drugs in laboratory prepared mixtures and in commercial tablets. No chromatographic interference from the tablets excipients was found.

Antihypertensive Agents↗
PubMed2002

Application of TLC-densitometry, first-derivative UV-spectrophotometry and ratio derivative spectrophotometry for the determination of dorzolamide hydrochloride and timolol maleate.

Three methods are described for the simultaneous determination of dorzolamide hydrochloride (DORZ) and timolol maleate (TIM) in ophthalmic solutions. The first method is based on application of thin layer chromatographic separation of both drugs followed by the densitometric measurements of their spot areas. After separation on silica gel GF(254) plates, using methanol-ammonia 25% (100:1.5 v/v) as the mobile phase, the chromatographic zones corresponding to the spots were scanned at 253 and 297 nm, respectively. The calibration function was established in the ranges of 2-18 microg for DORZ and 0.5-4.5 microg for TIM. The second method depends on first derivative ultraviolet spectrophotometry, with zero-crossing measurement method. The first derivative values D(1) at 250.2 and 312.5 nm were selected for the assay of DORZ and TIM, respectively. Calibration graphs follow Beer's law in the range 10-64 and 2.5-16 microg ml(-1), respectively. The third method is based on ratio first derivative spectrophotometry. The signals in the first derivative of the ratio spectra at 244 and 306.2 nm were selected to determine DORZ and TIM in the mixture and calibration graphs are linear in the range of 5-40 and 5.0-17.5 microg ml(-1), respectively. The proposed methods were successfully applied to the determination of these compounds in synthetic mixtures and in pharmaceutical preparations. The proposed methods are simple, rapid and suitable for quality control application.

Antihypertensive Agents↗
PubMed1998

Synaptophysin immunohistochemistry densitometry measurement in resected human hippocampus: implication for the etiology of hippocampal sclerosis.

Synaptophysin (SY) is a protein expressed at presynaptic vesicles. SY immunohistochemistry (IHC) was undertaken in surgically resected hippocampal specimens from 25 patients with intractable epilepsy. All were investigated with chronic ictal EEG videotelemetry, which showed a temporal onset in each case, and all had normal magnetic resonance imaging (MRI). The density of reaction product of SY IHC was used to generate optical density (OD) measurements as an estimate of synaptic density in CA1 and CA4 fields (ODCA1 and ODCA4), and inner third and outer two-thirds of the molecular layer of the dentate gyrus (ODIML and ODOML). There was significant correlation between ODCA1 (r=0.619, P=0.001) and ODCA4 (r=0.639, P=0.001) and onset age of epilepsy. There was no correlation between ODCA1 and duration of epilepsy. There was correlation between ODCA4 and duration (r=-0.412, P=0.041), but partial correlations showed no significant correlation between ODCA4 and duration when controlling for onset, although correlation between ODCA4 and onset when controlling for duration remained significant (r=0.536, P < 0.01). Univariate ANOVA revealed onset age to be the only predictor of ODCA1 and ODCA4. Chronological age and duration were not predictors. There was no correlation between ODIML or ODOML and either onset age or duration. ODIML and ODOML were not predicted by onset age, duration or chronological age. These findings support the hypothesis that the major cause of hippocampal sclerosis is an age specific insult rather than the result of repeated seizures.

Adult↗
PubMed2001

Practical aspects of Compton scatter densitometry.

A technique for determining the physical density distribution within an object using Compton scattered radiation is described. The technique is based on measuring the variation with the depth of 90 scattered radiation flux from an external monoenergetic photon source using a high-resolution solid-state detector. The measured scattered signal from an isolated volume element of the interrogated object is proportional to its electron density. For a definite region within the scanned object, the variation of the scattered yield with depth, along the direction of the incident beam, will give a counting curve with slope proportional to the density of the examined region. The spatial resolution of the system, determined by the collimator width, is 2 mm. The mathematical aspects of the technique are presented and the experimental data obtained in line scans of representative tissue equivalent materials are also shown to demonstrate the validity of the method.

Densitometry↗
PubMed1991

Experimental stray light in retinal densitometry.

The effects of stray light upon retinal pigment densitometric measurements were evaluated by adding specified amounts of stray light to fundus reflections. To allow for interpolations and extrapolations, a computer simulation was devised and validated against the empirical data. The results demonstrate that measured density is greatly decreased by increases in stray light but the time constant of pigment regeneration is little affected.

Computer Simulation↗
PubMed2004

Strength prediction of the distal radius by bone densitometry--evaluation using biomechanical tests.

Osteoporotic fractures represent an important medical problem as they are often early predictors of future fractures at other skeletal sites. The distal radius is one such fracture site. To determine the individual's risk of fracture, different measurement techniques have been developed. These methods differ in physical background, measurement site, output parameters, and cost. If correctly applied, biomechanical testing can be an efficient tool for the preclinical evaluation of these techniques. With biomechanical testing it is possible to determine the structural strength of bone which can then be correlated with various densitometric parameters. Here we will review experimental work performed in this context. Biomechanical testing conditions vary considerably from study to study with 3-point bending (shaft), axial compression (metaphysis), and fall simulations being some of the techniques used. Experimental evidence suggests that site-specific osteodensitometric measurements can predict the mechanical strength of the distal radius with moderate to high accuracy, but that measurements at remote sites display considerably lower predictive value. Geometry-based parameters of cortical bone are also good predictors, but have not been shown to offer significant advantage over measurement of bone mass. Some (but not all) studies have found that quantitative ultrasound and microstructural parameters contribute significant additional information to bone mass measurement. The most accurate prediction of distal radius fractures, however, appears to be (patient-specific) microstructural finite element modeling.

Animals↗
PubMed1996

Sensitive densitometry for the determination of platelet-activating factor and other phospholipids in human tears.

A sensitive TLC method is reported for the determination of the platelet-activating factor (PAF) and other phospholipids in human tears. Tear samples absorbed on filter-paper were subjected to diatomite column extraction with chloroform-methanol. The eluent containing phospholipids was spotted on a silica gel plate. After removing lipids other than phospholipids by pre-development with hexane-diethyl ether (4 + 1 v/v), individual phospholipid separation was carried out by development with chloroform-methanol-water (65 + 35 + 7 v/v). Phospholipase C and then alkaline phosphatase solutions were sprayed on the TLC plate at 45 degrees C to liberate phosphate from each phospholipid. By spray application of a mixture of ammonium molybdate and Malachite Green, the liberated phosphates appeared as blue-green spots of molybdophosphate-Malachite Green aggregate on a yellow-brown background. The absorbance of each spot on the plate was measured at 620 nm with a densitometer. The peak area was found to be linearly related to PAF content in the range 2-100 pmol per spot, the RSD being 2% (n = 7). Approximately 86% of standard PAF added to tears was recovered. By this method, lysophosphatidylcholine (lysoPC), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in human tears could also be detected with high sensitivity. Each phospholipid in healthy human tears showed a nearly constant content; PAF, lysoPC, PC and PE were present at levels of 26.2, 42.3, 10.0 and 19.7%, respectively.

Chromatography, Thin Layer↗