Histidine as a dipolar eluent component in cation chromatography. II. Prediction of retention data for alkaline and alkaline-earth ions.

The utility of cation chromatography has been developed by the application of L-histidine as a multiprotic and dipolar (zwitterionic) eluent component. The method simplifies the cation analysis. The chromatographic characteristics of this system were studied in detail with a view to determining the selectivity and the mechanism by which the cations (Na+, K+, Mg2+, Ca2+) are retained. Complete separations were observed in the isocratic run over the eluent concentration range 3.0-6.0 mM at pH below 2.0. Sensitive detection was achieved using suppressed conductivity at the pH of isoelectric point of the histidine. Retention equations are derived for mono- and divalent cations eluted from ion-exchange separation column with multiple ionic eluents. The theory is based on the extension of ion-exchange equilibrium by protonation equilibria. The selectivity data for analyte and eluent species are deterrmined using the model from the experimental retention data by computer-assisted iterative calculations. The model was utilized to predict retention data. The results in three-dimensional retention surfaces together with species distribution graphs are presented.

Effect of stationary phase hydrophobicity and mobile phase composition on the separation of carboxylic acids in ion chromatography.

In a previous work, we studied the retention behavior of monovalent and divalent carboxylic acids on a highly cross-linked polystryene-divinylbenzene anion-exchange column (IonPac AS4A-SC) using a carbonate-based buffer, and a retention model was applied to the chromatographic data obtained. In this work we characterized the retention of carboxylates (formic, acetic, propionic, lactic, pyruvic, oxalic, malonic, succinic, fumaric, maleic, tartaric, glutaric, adipic, malic, mucic, trans-beta-hydromuconic, trans,trans-muconic acids) on a column with higher hydrophilicity (IonPac AS11) according to analyte and stationary phase properties, using previously investigated eluent compositions and comparing the retention data obtained. Moreover, the effect of organic modifiers (CH3OH and CH3CN) in the eluent on the retention factors was also evaluated. The chromatographic data obtained on the IonPac AS11 column were fitted by the retention model and allowed one to obtain and to compare ion-specific selectivity constants (parameters of the model) with the ones obtained with the previous column.

Retention behaviours and separation of carboxylic acids by ion-exchange chromatography.

The use of high-performance suppressed ion chromatography for the separation of aliphatic carboxylic acids has become an attractive and viable method during the past years. This paper summarises and critically concludes that some new results have been achieved in separation and detection of low-molecular-mass organic anions. Theoretical and practical considerations of ion-exchange selectivity to control retention behaviour are presented. The major factors that determine the separation ability of ion-exchange chromatography (pKa values, the aliphatic nature and valency of solutes, eluent pH and the chemical composition of stationary phases) are discussed. The question of isocratic vs. gradient elution and different separation modes are examined briefly. The potentials and limitations of the developed methods and their specific application areas are outlined.

Elevated serum tumor necrosis factor-alpha concentrations and bioactivity in Type 2 diabetics and patients with android type obesity.

The role of tumor necrosis factor-alpha in insulin resistance has been studied in 59 patients with Type 2 diabetes, 28 with android type obesity and 35 healthy lean controls. Immunoreactive concentrations and bioactivity of serum tumor necrosis factor-alpha have repeatedly been determined in 8 weeks intervals for 12 months, five times per patients, by using ELISA and L929 cell cytotoxicity bioassay. Significantly higher immunoreactive tumor necrosis factor-alpha concentrations and bioactivity have been found in both, the Type 2 diabetic and obese groups as compared to the healthy persons. Tumor necrosis factor-alpha concentrations and bioactivity have showed a significant positive linear correlation with the elevated basal serum C-peptide levels and body mass indexes in both groups of patients. According to these data the cytokine might play a role in insulin resistance in obesity as well in Type 2 diabetes.

[Experience with benazepril, a long-acting ACE inhibitor, in the management of diabetic hypertension]. / Hosszú hatástartamú ACE-gátló készítménnyel, benazeprillel szerzett tapasztalatok a diabetes mellitust kísérö hypertonia kezelésében.

The therapeutic advantage of the long acting ACE-inhibitor benazepril in a 12 weeks intervention period on 23 diabetic (3 IDDM, 20 NIDDM) patients with essential hypertension was studied. Participants-giving informed consent before beginning the study-on the base of repeated casual blood pressure measurements were divided into "slightly" (n = 8) and "moderately" (n = 15) hypertonic groups. Type of diabetes, time elapsed since its manifestation, actual antidiabetic therapy, period of existence of the hypertension (newly discovered vs known and treated for a time) were independent from the point of view of entering the study. Initial dose of benazepril was 5-10 mg/day depending on the blood pressure level, followed by a stepwise dose elevation according to the control investigations (at weeks 2, 4, 8 and 12 casual blood pressure control, at weeks 4 and 12 ambulantory blood pressure monitoring, ABPM as well) to a maximal daily dose of 20 mg. In the majority of patients benazepril was given in a morning single dose, in some cases because of a better tolerability divided into two parts. 20 patients received benazepril in monotherapy, 3 patients combined with other antihypertensive preparations. Parameters indicating severity of hypertension-hypertonic time index, hyperbaric impact-showed significant improvement already at week 4 when analysed in the total of patients and the moderately hypertonic group respectively. As a tendence the same was observed also in the slightly hypertonic group. No remarkable side effects, or alterations of the metabolic state and in the investigated laboratory parameters appeared. Based on these results benazepril is an effective choice in the treatment of diabetic hypertensive patients.

Classical retention mechanism in ion exchange chromatography. Theory and experiment.

The classical model for ion exchange chromatography is characterized by firmly adsorbed driving ions at the surface of the stationary phase in an amount required by electroneutrality and stoichiometric ion exchange between the bulk of the eluent electrolyte and this immobilized Stern layer. Retention equations have been derived for system peaks, labeled eluent ions, and analytes in a system containing only strong electrolytes by strictly respecting this model. It is shown that the classical model described dependence of retention data on concentration and composition of the binary eluent with excellent precision, but the resulting system parameters were not self-consistent. Inconsistency of the results might be due to contributions from another retention mechanism.

Retention in analytical ion exchange chromatography-1. Strong electrolytes on strong ion exchangers.

A retention equation of general validity is adapted to ion exchange chromatography providing a self-consistent interpretation of retention of solutes and system peaks. Discussion is limited to eluent mixtures containing ions of invariant charge and to stationary phases with pH-independent surface charge. An interpretation is proposed for the retention volume of system peaks in binary eluents (mixtures of two eluent counter-ions). Retention volumes of labelled counter-ions of the eluent appear to provide useful information about the chromatographic system with clear interpretation in any multicomponent eluent.

Effect of lipanthyl in hyperlipoproteinaemic diabetic patients.

Diabetic metabolic disorder means, at the same time, a disturbed lipid metabolism. On the basis of this consideration the authors examined the drug in diabetic patients and found it to have a very advantageous effect. In response to the drug lipid parameters improved rapidly but after discontinuance of therapy these values deteriorated again which indicates the effectiveness of the product but calls the attention to the importance of continuous drug administration.

Acetylator phenotypes: effect of age.

The distribution of acetylator phenotypes in a Hungarian population of 253 Caucasian was studied. The patients were divided into two age groups - the elderly over 60 years, and young below that age. The individuals below the age of 60 years contained an equal proportion of the two acetylator phenotypes. The same distribution was observed in the population as a whole. In the elderly subjects the slow acetylator phenotype was predominant. The finding supports the hypothesis that age has an influence on hepatic drug acetylation rate.

The effect of oral contraceptives on serum lipids gamma-glutamyl transpeptidase, and excretion of d-glucaric acid.

The authors studied three oral contraceptives (Bisecurin, Ovidon, Rigevidon) in 37 healthy women in order to establish their effect on serum lipids, gamma-glutamyl transpeptidase and d-glucaric acid excretion. After 3-9 months of oral contraception, a significant increase was observed in serum cholesterol and beta-lipoprotein levels in women taking the two contraceptives with major hormone content. None of the contraceptives changed the serum glyceride level. Serum gamma-glutamyl transpeptidase levels were significantly enhanced. D-glucaric acid excretion increased. There was no correlation between the parameters of enzyme induction and the change of lipid metabolism.

[The effect of contraceptives on serum lipids, gamma glutamyl transpeptidase and D-glucaric acid elimination]. / Fogamzásgátlók hatása a szérum lipidekre, a gammaglutamyl-transzpeptidázra és a D-glukársav ürítésre.

PIP: The authors examined the effect of 3 oral contraceptives (OCs) (Bisecurin, Ovidon, and Rigevidon) on serum lipids, gamma glutamyl transpeptidase, and D-glutaric acid elimination. After 3-9 months of this medical contraception the two with the highest hormonal content significantly increased the serum cholesterol and the BLP levels. Neither one influenced the level of serum triglycerides. All significantly increased the serum level of gamma-glutamyl transpeptidase. The elimination of D-glutaric acid was also augmented. They did not find any correlation between the parameters of enzyme induration and lipid metabolism due to the taking of OCs.^ieng