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H Iturriaga

Publications and source records attributed to H Iturriaga.

At least 19 recordsLinked to original sources
PubMed2002

Kinetic-spectrophotometric determination of theophylline, dyphylline, and proxyphylline by use of partial least-squares regression.

A kinetic-spectrophotometric method for the determination of theophylline, dyphylline and proxyphylline, based on their azo coupling reaction with the diazonium ion of sulfanilic acid after a treatment with alkali, is proposed. The absorbance is recorded from 340 to 600 nm every second during reaction for 90 s, and calibration is performed by partial least-squares regression, using first derivative spectra values. Mixtures containing 2.5-13 micro g mL(-1) dyphylline and proxyphylline, and 2-9 micro g mL(-1) theophylline were successfully resolved with root mean squared errors of prediction (RMSEP) of 0.4, 0.3, and 0.2 for dyphylline, proxyphylline, and theophylline, respectively. The proposed method was satisfactorily applied to the determination of the three compounds in a commercially available pharmaceutical preparation and provided results similar to those obtained by HPLC.

Aminophylline↗
PubMed2001

Resolution of isomers of sorbitolparaben esters by chromatographic and electrophoretic techniques.

Pharmaceutical preparations usually contain preservatives and sweeteners. When parabens are used as preservatives and a polyol as a sweetener, a transesterification reaction may happen, yielding the transester polyol-paraben. The products formed in the transesterification reaction of methylparaben and sorbitol were analyzed by micellar electrokinetic chromatography and by HPLC. Up to six positional isomers of sorbitolparaben (SPB) can be produced. However, only three peaks were found by HPLC. The higher efficiency and resolution power of MEKC allowed one to resolve five peaks. Results were compared with those obtained by capillary zone electrophoresis in borate buffer, where the separation of isomers occurred in a different way, because of a complexation between SPB and borate.

Chromatography, High Pressure Liquid↗
PubMed2001

Analytical control of a pharmaceutical formulation of sodium picosulfate by capillary zone electrophoresis.

A new procedure for the analytical control of a pharmaceutical formulation by capillary zone electrophoresis (CZE) is proposed. It allows the simultaneous determination of the major compounds in the formulation: active compound (sodium picosulfate) and preservative (methylparaben), and the degradation products of the preservative, which slowly degrades by hydrolysis or by transesterification with sorbitol (sweetener in excess in the formulation) yielding p-hydroxybenzoic acid and sorbitolparaben, respectively. UV-Vis detection in the absorption maxima of the analytes and 20 mM borate solution at pH 10 as background electrolyte are used. Results are compared with those provided by the HPLC procedure. The method has also been validated using the HPLC procedure as the reference method, evaluating selectivity, accuracy, linearity and precision. The CZE procedure developed is sufficiently accurate and the precision achieved is about 1% for major and 3% for minor compounds.

Calibration↗
PubMed2001

Multi-component kinetic-spectrophotometric analysis. Selection of wavelength and time ranges.

An empirical method for the selection of the best wavelength and time ranges which can be used in the quantification of binary mixtures, in a kinetic-spectrophotometric system, is proposed. It is based on finding those ranges which provide the least correlation between the kinetic profiles and the spectra of the products of reaction. The method was applied to the analysis of binary mixtures using simulated data with different rate constant ratios and in the presence of an interference that shows spectral overlap with the analytes. Subsequently, the proposed method was applied to the resolution of dyphylline and proxyphylline mixtures. The system studied was characterized by an elevated similarity in the kinetic behavior of the analytes under pseudo-first-order conditions and an elevated degree of spectral overlap of the products of reaction. In spite of this, satisfactory results were obtained in the quantification of the two analytes. The standard error of prediction (SEP) and the standard deviation between replicates (SDBR) did not show significant differences, being of the order of 4 and of 3% for dyphylline and proxyphylline, respectively.

Journal Article↗
PubMed2001

Influence of the procedure used to prepare the calibration sample set on the performance of near infrared spectroscopy in quantitative pharmaceutical analyses.

Calibrating near infrared diffuse reflectance spectroscopy (NIRS) methods usually involves preparing a set of samples with a view to expanding the analyte concentration range spanned by production samples. In this work, the performances of the two procedures most frequently used for this purpose in near infrared pharmaceutical analysis, viz., synthetic samples obtained by weighing of the pure constituents of the pharmaceutical and doped samples made by under- or overdosing previously powdered production samples, were compared. Both procedures were found to provide similar results in the quantification of the active compound in the pharmaceutical, which was determined with a relative standard error of prediction (RSEP) of < 1.6%. However, the two types of sample preparation provide different spectra, which precludes the accurate quantification of synthetic samples from calibrations obtained with doped samples and vice versa. None of the mathematical pre-treatments tested with a view to reducing this different scattering (viz., second derivative, standard normal variate and orthogonal signal correction) could effectively solve this problem. This hinders accurate validation of the linearity of the procedure and makes it advisable to use doped samples which are markedly less different to production samples.

Calibration↗
PubMed2000

Development and validation of a near infrared method for the analytical control of a pharmaceutical preparation in three steps of the manufacturing process.

A near infrared diffuse reflectance spectroscopy (NIRS) procedure for the quantitative control analysis of the active compound (otilonium bromide) in a pharmaceutical preparation in three steps of the production process (blended product, cores and coated tablets) and a methodology for its validation are proposed. The analytical procedure is composed by two consecutive steps. First, the sample is identified by comparing its spectrum with a second derivative spectral library. If the sample is positively identified, the active compound is quantified by using a previously established partial least squares (PLS) calibration model. The procedure was validated by studying repeatability, intermediate precision, accuracy and linearity. To this end, an adaptation of ICH (International Conference on Harmonisation) validation methodology to an NIR multivariate calibration procedure is proposed. The relative standard error of prediction (RSEP) was < or = 1% and the suitability of the procedure for control analysis was confirmed by the results obtained analysing new production samples produced over a three-month period.

Calcium Channel Blockers↗
PubMed2000

Characterization of the oligosaccharides of plasma sex hormone binding globulin from noncirrhotic alcoholic patients.

In previous reports we have demonstrated high plasma levels of sex hormone-binding globulin (SHBG) in asymptomatic alcoholic men. In the present work the physicochemical properties of SHBG from plasma of noncirrhotic alcoholic patients have been further compared with SHBG of control subjects. Steroid binding to SHBG was similar for the two groups: alcoholic men, K(d) of 0.62 +/- 0.07 nM and control individuals, K(d) of 0.70 +/- 0.10 nM. The structure of oligosaccharides attached to SHBG from controls and alcoholic men were determined by using serial chromatography. Our data indicated that 7% of SHBG of control individuals was not retarded by the Con-A column, whereas approximately 30% of SHBG of alcoholic men eluted in the void volume of Con A. Approximately 46% of SHBG of alcoholics applied to Con A, possessed biantennary complex oligosaccharides, as indicated by the fact that it could be eluted with methyl-alpha-D-glucopyranoside and by its retention on wheat germ agglutinin; in contrast, when SHBG from control men was analyzed, approximately 51% was eluted with methyl-alpha-D-glucopyranoside. Approximately 9% of the biantennary complex oligosaccharides on SHBG of control men and none of those on SHBG from alcoholic men were fucosylated on the chitobiose core, as determined by chromatography on Lenn culinaris lectin. Galactosylated oligosaccharides were also present on the SHBG fraction as indicated by its interaction with Ricinus communis-I. Approximately 24% of SHBG of alcoholic men and 39% of those on SHBG from control individuals applied to Con-A were retained and could be eluted with methyl-alpha-D-mannopyranoside. Evidence based on the binding on mannoside-eluted SHBG to Con-A, wheat germ agglutinin, and R. communis-I indicated that at least the SHBG in this fraction, from alcoholics or controls, contained two glycosylation sites and that the sites were differentially glycosylated.

Adult↗
PubMed1999

Development and validation of a method for the analysis of a pharmaceutical preparation by near-infrared diffuse reflectance spectroscopy.

A near-infrared (NIR) spectroscopic method based on the use of a fiber optical probe for the analysis of a commercially available pharmaceutical preparation is proposed. The analyte is identified by comparison with a second-derivative spectral library, using the correlation coefficient as the discriminating parameter. Once a sample has been positively identified, the active principle is quantified with partial least-squares (PLS) calibration. The proposed method was validated for use as a control method; to this end, the selectivity of the identification process, and the repeatability, intermediate precision, accuracy, linearity, and robustness of the active principle quantitation, were assessed.

Sensitivity and Specificity↗
PubMed1999

Kinetic spectrophotometric determination of hydrocortisone acetate in a pharmaceutical preparation by use of partial least-squares regression.

A kinetic spectrophotometric method for the determination of hydrocortisone acetate based on its condensation with isonicotinic acid hydrazide is proposed. The method is applied to the determination of hydrocortisone acetate in a commercially available pharmaceutical preparation, presented as a pomade, that also contains another corticosteroid and additional active compounds. The operating procedure involves dissolving the pomade in chloroform and the addition of the reagent solution directly to the cuvette, in this way avoiding the previous extraction of analytes from the insoluble pomade matrix required by the alternative HPLC procedure. Calibration is performed by partial least-squares regression, using absorbance or first derivative spectra values recorded each minute during the first 30 min of reaction. Use of first derivative spectra overcomes possible scattered light problems produced by excipients precipitating, and produced slightly better results than absorbance data. The relative standard deviation obtained for 11 replicates analysed on different days was approx. 1.5%. The proposed method improves both accuracy and precision of the classical initial rate method and the precision of the HPLC procedure.

Hydrocortisone↗
PubMed1998

Chiral and nonchiral determination of ketoprofen in pharmaceuticals by capillary zone electrophoresis.

The new method for the enantiomeric resolution of various 2-arylpropionic acids by capillary zone electrophoresis (CZE) using heptakis-tri-O-methyl-beta-cyclodextrin as chiral selector was applied to the determination of ketoprofen in different commercially-available pharmaceutical preparations. The analyte was determined under chiral and nonchiral conditions (viz. in the presence and absence of 50 mM heptakis-tri-O-methyl-beta-cyclodextrin in the background electrolyte), with significantly similar results and relative standard deviations from 1.2 to 6.5% in both cases. The limits of detection and determination for the inactive enantiomer, R-(-)-ketoprofen, were calculated to be 7.0 x 10(-7) and 1.6 x 10(-6) M, respectively. The proposed method was successfully used to determine enantiomeric purity in the drugs studied, with results comparable to those provided by the chiral HPLC method.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Separation of profen enantiomers by capillary electrophoresis using cyclodextrins as chiral selectors.

A method for resolving the enantiomers of various 2-arylpropionic acids (viz. ketoprofen, ibuprofen and fenoprofen) by capillary zone electrophoresis (CZE) using a background electrolyte (BGE) containing a cyclodextrin as chiral selector is proposed. The effects of the type of cyclodextrin used and its concentration on resolution were studied and heptakis-2,3,6-tri- O-methyl-beta-cyclodextrin was found to be the sole effective choice for the quantitative enantiomeric resolution of all the compounds tested. The influence of pH, BGE concentration, capillary temperature and addition of methanol to the BGE on resolution and other separation-related parameters was also studied. The three compounds studied can be enantiomerically resolved with a high efficiency in a short time (less than 20 min) with no capillary treatment. This makes the proposed method suitable for assessing the enantiomeric purity of commercially available pharmaceuticals.

Cyclodextrins↗
PubMed1998

Near-infrared analytical control of pharmaceuticals. A single calibration model from mixed phase to coated tablets.

A new method for analysis of the active compound in a commercial pharmaceutical formulation in different steps of the production cycle, based on near-infrared diffuse reflectance spectroscopy, is proposed. The analysis includes three different steps of the production cycle: granules ready for compression (mixed phase), cores (intermediate) and coated tablets (final product). Satisfactory predictive results for production samples, independently of its origin in the production cycle, require calibration with laboratory-made samples covering the concentration range involved in the manufacturing process, and also production samples from various production batches and different steps, which introduce the variation sources inherent in such a process. A global and sole model was found to determine the active compound during the production cycle, with errors of prediction less than 1.8% in all cases. Tablets can be individually analysed with high accuracy and precision, so a content uniformity analysis may be performed.

Calibration↗
PubMed1997

Determination of water in ferrous lactate by near infrared reflectance spectroscopy with a fibre-optic probe.

Near infrared diffuse reflectance spectroscopy with a fibre-optic probe was used to determine the water content in ferrous lactate dihydrate. Spectra were recorded by immersing the probe in a beaker containing the ferrous lactate sample. Spectral data were processed by using two different multivariate calibration procedures, viz. stepwise multiple linear regression (SMLR) and partial least-squares regression (PLSR). The results provided by the two calibration procedures were similar and departed by less than 1.5% from the values obtained by Karl Fischer titration.

Ferrous Compounds↗
PubMed1997

[Markers of hepatic fibrogenesis in alcoholic patients].

BACKGROUND: An elevation of serologic markers of hepatic fibrogenesis has been reported in liver diseases of different etiologies. Among these, the N-terminal type III procollagen (P-III-P) and the P1 proteolytic fragment of laminin (P1 laminin) increase in alcoholic liver damage, in proportion to the progression of this condition. AIM: To study serum levels of P-III-P and P1 laminin in asymptomatic alcoholics with and without liver damage and decompensated alcoholic cirrhotics, compared to normal controls. METHODS: Serum P-III-P and laminin levels were measured in asymptomatic alcoholics during detoxification treatment. Liver biopsies were obtained, in order to detect liver damage, which was graded with a numeric score, considering values over 6 as severe damage. Serum fibrogenesis markers were also measured in a group of decompensated alcoholic cirrhotics. RESULTS: P-III-P levels were significantly higher in cirrhotic patients compared to alcoholics with or without liver damage and to normal controls. Laminin was not different between groups. P-III-P did not correlate with histologic score in asymptomatic patients. CONCLUSIONS: In this study P-III-P and P1 laminin were not usefull discriminators of severe liver damage among asymptomatic alcoholics; their levels were found to rise significantly only when liver disease has become clinically evident.

Adult↗
PubMed1997

[Present and future of internal medicine].

To mention the crisis of Internal Medicine has become a commonplace, that is extremely wrong, because Internal Medicine is stronger than ever, with many recent and important contributions like randomised clinical trials, metaanalysis, evidence-based diagnosis, cost-benefits analysis, etc. We consider as Internists the General Internist, the sub-specialist and the primary care physician. Among them, it is the General Internist who needs to redefine his working areas, that are progressively moving from the hospital into ambulatory care. Internal Medicine is stretched by 3 strong vectorial forces: 1. Its own development and technological progress. 2. Economical factors trying to limit increasing costs. 3. Social forces demanding a better quality of care Internal Medicine shall need to equilibrate all these forces and be prepared to solve future challenges such as demographic changes, including an ageing population, the compression of morbidity, increasing demands of better care and quality of life, contemption of excessively high costs and now technical and ethical problems. The internist should be the best prepared specialist to cope with these challenges; but to better assume them, deep changes in pre and post graduate medical education are needed.

Forecasting↗
PubMed1996

Partial least-squares regression for the quantitation of pharmaceutical dosages in control analyses.

A spectrophotometric method for the simultaneous determination of the active principle and a flavouring agent in syrups containing additional excipients is proposed. The calibration matrix must include all the variability expected in the samples and this is achieved using laboratory-made mixtures and production samples in order to ensure correct results. The optimum number of principal components for the regression model was selected by using various procedures. The proposed method was used to quantify samples from different production batches. The results are compared with those provided by HPLC.

Allylbenzene Derivatives↗
PubMed1995

Artificial neural networks for multicomponent kinetic determinations.

An artificial neural network (ANN) procedure that uses the scores of a principal component model as input data was tested for calibration in the resolution of binary mixtures from kinetic measurements. The results thus obtained are compared with those provided by partial least-squares (PLS) regression and principal component regression (PCR). The ANN was first applied to simulated single wavelength kinetic curves. The effect of experimental variability was considered by assuming rate constants to fit a normal distribution curve. An amount of instrumental noise was also added to the simulated curves. Both linear and nonlinear systems were tested. Non-linearity was assumed to result from interactions between analytes and modeled by introducing a multiplicative term in the rate equation. The results provided by the three methods on linear systems were comparable; in the presence of interactions between analytes, however, the ANN method clearly outperformed the other two. The ANN method was also used to resolve mixtures of Fe(III), Co(II), and Zn(II) by displacement from their EGTA complexes with 4-(2-pyridylazo)resorcinol (PAR) using a stopped-flow injection assembly including a diode array detector. Preliminary experiments revealed the Co(II) and Zn(II) displacement reactions to be pseudo-first-order and that of Fe(III) to be a multistep process that departed from the linear behavior of the other two. Again, the results obtained with ANN were better than those provided by PCR and PLS.

Calibration↗