Characterization and quantification of epilepsy patients with hospital episodes in Portugal: A multicenter retrospective study from Liga Portuguesa Contra a Epilepsia

INTRODUCTION

Epilepsy affects around 50 million people worldwide and is associated with lower quality of life scores, an increased risk of premature death, and significant socio-economic implications. The lack of updated evidence on current epidemiology and patient characterization creates considerable uncertainty regarding the epilepsy burden in Portugal. The study aims to characterize and quantify the epilepsy patients who have been hospitalized, with medical or surgical procedures involved, and to analyze their associated comorbidities and mortality rates.

METHODS

A multicenter retrospective study was conducted using hospital production data of epilepsy patients. The study included all patients diagnosed with epilepsy-related International Classification of Diseases-9/10 codes between 2015 and 2018 in 57 Portuguese National Health Service (NHS) hospitals (n = 57 institutions). Patient characterization and quantification were done for all patients with an epilepsy diagnosis, with specific analyses focusing on those whose primary diagnosis was epilepsy. Baseline, demographic, and clinical characteristics were analyzed using descriptive statistics.

RESULTS

Between 2015 and 2018, a total of 80,494 hospital episodes (i.e., patient visit that generates hospitalization and procedures) were recorded, with 18 % to 19 % directly related to epilepsy. Among these epilepsy-related hospital episodes, 13.0 % led to short term hospitalizations (less than 24 h). Additionally, the average length of stay for all these epilepsy-related episodes was 8 days. A total of 49,481 patients were identified with epilepsy based on ICD-9/10 codes. The median age of patients was 64 years (min: 0; max: 104), with a distribution of 4.8 patients per 1,000 inhabitants. From the total of deaths (9,606) between 2015 and 2018, 14% were associated with patients whose primary diagnosis was epilepsy, with 545 of these being epilepsy-related deaths. Among patients with a primary diagnosis of epilepsy, the most common comorbidities were hypertension (24%) and psychiatric-related or similar comorbidities (15%), such as alcohol dependance, depressive and major depressive disorders, dementia and other convulsions.

CONCLUSION

This study showed similar results to other European countries. However, due to methodological limitations, a prospective epidemiological study is needed to support this observation. Furthermore, the present study provides a comprehensive picture of hospitalized epilepsy patients in Portugal, their comorbidities, mortality, and hospital procedures.

Massive degeneration and atrophy of the native heart after heterotopic transplantation: a case report

Extreme myocardial degeneration leading to advanced stages of cardiomyopathy with extensive atrophy is rarely observed before patients die. However, heterotopic transplantation is a special situation wherein this phenomenon can be observed. The greater part of the failed heart shows recuperation after receiving circulatory assistance by reduction of myocardial work. Herein we have reported an unusual behavior of degenerative cardiomyopathy associated with intense myocardial apoptosis resulting in extreme ventricular atrophy after heterotopic heart transplantation. An 11-year-old girl with end-stage heart failure due to dilated cardiomyopathy of undetermined etiology without pulmonary hypertension underwent heterotopic cardiac transplantation with an undersized (by weight mismatch) donor heart. After 9 years heart failure reappeared due to native heart enlargement leading to allograft compression. The patient underwent native heart replacement leaving her with 2 donor hearts. Despite normal hemodynamic recuperation, the patient experienced massive arterial microemboli which led to death. Pathological studies showed exuberant myocardial degeneration in the native heart with intense atrophy of the muscle and gigantic ventricular enlargement. The left ventricle wall was extremely thin with rarefaction of cardiomyocytes and replacement by fibrosis. The right ventricle showed old extensive thrombosis. In conclusion, this report is not usual as it is not frequent to observe cardiomyopathy with an intense degree of myocardial degeneration and atrophy, because the patient dies earlier. In special situations it is possible that a recipient may have 2 donor hearts with normal hemodynamics. Heterotopic heart transplantation is a surgical alternative in a priority situation offering excellent outcomes; however, the native heart must be removed when there is compromise of the function of the heterotopic allograft.

Comparison of maize similarity and dissimilarity genetic coefficients based on microsatellite markers

The present study compared different similarity and dissimilarity coefficients and their influence in maize inbred line clustering. Ninety maize S0:1 inbred lines were used and genotyped with 25 microsatellite markers (simple sequence repeat). The simple matching, Rogers and Tanimoto, Russel and Rao, Hamann, Jaccard, Sorensen-Dice, Ochiai, and Roger's modified distance coefficients were compared by consensus index, projection efficiency in a two-dimensional space and by Spearman's correlation. Changes were found in high genetic similarity groupings with different coefficients using the consensus index. Russel and Rao and Jaccard coefficients had the greatest stress values with 75.67 and 40.16%, respectively, indicating that these coefficients should not be used. Genotype ranking changed, mainly in the comparison of the Roger's modified distance in relation to some coefficients (rs = 0.75). Russel and Rao's and Jaccard's coefficients should be avoided for their low accuracy. Moreover, genotype clustering by different similarly coefficients, without a close consideration of these coefficients could affect the research results.

A nonsense mutation in the LIMP-2 gene associated with progressive myoclonic epilepsy and nephrotic syndrome

The main clinical features of two siblings from a consanguineous marriage were progressive myoclonic epilepsy without intellectual impairment and a nephrotic syndrome with a strong accumulation of C1q in capillary loops and mesangium of kidney. The biochemical analysis of one of the patients revealed a normal beta-glucocerebrosidase activity in leukocytes, but a severe enzymatic deficiency in cultured skin fibroblasts. This deficiency suggested a defect in the intracellular sorting pathway of this enzyme. The sequence analysis of the gene encoding LIMP-2 (SCARB2), the sorting receptor for beta-glucocerebrosidase, confirmed this hypothesis. A homozygous nonsense mutation in codon 178 of SCARB2 was found in the patient, whereas her healthy parents were heterozygous for the mutation. Besides lacking immunodetectable LIMP-2, patient fibroblasts also had decreased amounts of beta-glucocerebrosidase, which was mainly located in the endoplasmic reticulum, as assessed by its sensitivity to Endo H. This is the first report of a mutation in the SCARB2 gene associated with a human disease, which, contrary to earlier proposals, shares no features with Charcot-Marie-Tooth disease both at the clinical and neurophysiological levels.

Genetic distance estimates among single cross hybrids and correlation with specific combining ability and yield in corn double cross hybrids

The objective of the present study was to correlate the genetic distances (GD) of single cross hybrids with yield, heterosis and specific combining ability (SCA) in the double cross hybrid synthesis. For this, 10 single cross commercial hybrids were used from different companies, and all the possible double hybrids were synthesized by a complete dialell. The hybrids were assessed in 15 locations in the 2005/2006 agricultural season, using the randomized complete block design with three repetitions. DNA was extracted from the single cross hybrids and 20 simple sequence repeat primers were used, nine of which were linked to the quantitative trait loci. It was ascertained that the single hybrids were superior in general to the double cross hybrids and that yield was highly correlated with heterosis and SCA (r = 0.75 and 0.82, respectively). There was no significant correlation between yield and GD (r = 0.25), but this index was at the limit of significance. There was a medium correlation between GD and heterosis (r = 0.40) and GD and SCA (r = 0.38). The intergroup hybrids placed by genetic grouping were generally more productive than intragroup hybrids, and the hybrids with GD greater than 0.84 had the maximum heterosis and SCA. It was concluded that the markers were efficient in placing hybrids in different heterosis groups and were also useful in eliminating the most negative heterosis and SCA.

Derivative spectrophotometry as a tool for the determination of drug partition coefficients in water/dimyristoyl-L-alpha-phosphatidylglycerol (DMPG) liposomes

The partition coefficients (K(p)) between lipid bilayers of dimyristoyl-L-alpha-phosphatidylglycerol (DMPG) unilamellar liposomes and water were determined using derivative spectrophotometry for chlordiazepoxide (benzodiazepine), isoniazid and rifampicin (tuberculostatic drugs) and dibucaine (local anaesthetic). A comparison of the K(p) values in water/DMPG with those in water/DMPC (dimyristoyl-L-alpha-phosphatidylcholine) revealed that for chlordiazepoxide and isoniazid, neutral drugs at physiological pH, the partition coefficients are similar in anionic (DMPG) and zwitterionic (DMPC) liposomes. However, for ionised drugs at physiological pH, the electrostatic interactions are different with DMPG and DMPC, with the cationic dibucaine having a stronger interaction with DMPG, and the anionic rifampicin having a much larger K(p) in zwitterionic DMPC. These results show that liposomes are a better model membrane than an isotropic two-phase solvent system, such as water-octanol, to predict drug-membrane partition coefficients, as they mimic better the hydrophobic part and the outer polar charged surface of the phospholipids of natural membranes.

Partition coefficients of beta-blockers in bile salt/lecithin micelles as a tool to assess the role of mixed micelles in gastrointestinal absorption

The objective of this study was to develop non-invasive spectroscopic methods to quantify the partition coefficients of two beta-blockers, atenolol and nadolol, in aqueous solutions of bile salt micelles and to assess the effect of lecithin on the partition coefficients of amphiphilic drugs in mixed bile salt/lecithin micelles, which were used as a simple model for the naturally occurring mixed micelles in the gastrointestinal tract. The partition coefficients (Kp) at 25.0 +/- 0.1degreesC and at 0.1 M NaCl ionic strength were determined by spectrofluorimetry and by derivative spectrophotometry, by fitting equations that relate molar extinction coefficients and relative fluorescence intensities to the partition constant Kp. Drug partition was controlled by the: (i) drug properties, with the more soluble drug in water (atenolol) exhibiting smaller values of Kp, and with both drugs interacting more extensively in the protonated form; and by (ii) the bile salt monomers, with the dihydroxylic salts producing larger values of Kp for the beta-blockers, and with glycine conjugation of the bile acid increasing the values of Kp for the beta-blockers. Addition of lecithin to bile salt micelles decreases the values of Kp of the beta-blockers. Mixed micelles incorporate hydrophobic compounds due to their large size and the fluidity of their core, but amphiphilic drugs, for which the interactions are predominantly polar/electrostatic, are poorly incorporated in mixed micelles of bile salts/lecithin.

Effect of liposomes on the rate of alkaline hydrolysis of indomethacin and acemetacin

The anti-inflammatory, analgesic, and antipyretic drugs indomethacin (INDO) and acemetacin (ACE), extensively used for the treatment of diseases of degenerative or inflammatory character, exhibit marked gastric irritant action, have low water solubility at neutral pH, and decompose in alkali. Alternative formulations are being investigated to obtain products with lower toxicity and higher stability. Here we examine the effect of liposome charge on the rate of alkaline decomposition of INDO and ACE using micelles as reference. Binding of ACE and INDO to zwitterionic hexadecylphosphocholine (HDPC) micelles and phosphatidylcholine (PC) liposomes was analyzed using a two-phase separation model to quantify the effect of these aggregates on the rate of alkaline degradation. The substrate association constants to HDPC micelles were 1335 and 2192 M(-1) for INDO and ACE, respectively, whereas the corresponding values for PC vesicles were 612 and 3050 M(-1). The difference was attributed to the additional hydrophobicity of ACE. The inhibitory effect of HDPC micelles and PC vesicles was quantified by calculating the ratio between the rate constants in water (k(w)) and in the aggregate (k(m)). The values of the k(w)/k(m) ratios for INDO and ACE in HDPC micelles were, respectively, 80 and 42, and in PC liposomes these ratios were 21 and 3.7, respectively. Positively charged micelles of hexadecyltrimethylammonium chloride (CTAC) and vesicles containing varying proportions of dioctadecyldimethylammonium chloride (DODAC) and PC increase the rate of INDO and ACE alkaline decomposition. Vesicle effects were very sensitive to the DODAC/PC ratio, with rates increasing with the proportion of DODAC. The data were analyzed quantitatively using a pseudophase model with explicit consideration of ion exchange. The calculated second-order rate constants in micelles and vesicles were lower than that in water. The charge density in the liposome necessary to increase the entrapment efficiency and decrease drug decomposition can be modulated, by judicious choice of pH and ionic strength. These manipulations can lead to more stable formulation with increased efficiency in drug entrapment and controlled effects on drug stability.

Cost minimization analysis of antiepileptic drugs in newly diagnosed epilepsy in 12 European countries

A recent United Kingdom cost minimization analysis (CMA) of four antiepileptic drugs (AEDs) used to treat newly diagnosed adult epilepsy demonstrated that a new drug, lamotrigine (LTG), incurred higher costs than carbamazepine (CBZ), phenytoin (PHT), and valproate (VPA), whose costs were similar. This analysis took account of each drug's side-effect and tolerability profile. The present analysis investigated the costs of treatment with LTG, CBZ, PHT, and VPA in 12 European countries. Data were derived from published sources and from a panel of locally based experts. When no published data were available, estimates were obtained using expert opinion by a consensus method. These data were incorporated into a treatment pathway model, which considered the treatment of patients during the first 12 months after diagnosis. The primary outcome considered was seizure freedom. Randomized controlled trials demonstrate that the drugs considered are equally effective in terms of their ability to achieve seizure freedom, and thus the most appropriate form of economic evaluation is a CMA. These trials provided data on the incidence of side effects, dosages, and retention rates. The economic perspective taken was that of society as a whole and the analysis was calculated on an "intent-to-treat" basis. Only direct medical costs were considered. In each country considered, LTG was twofold to threefold more expensive than the other drugs considered. A sensitivity analysis demonstrated that varying each of the assumptions (range defined by expert panels) did not significantly alter the results obtained.

Study of partition of nitrazepam in bile salt micelles and the role of lecithin

The effect of trihydroxy (sodium cholate and sodium glycocholate) and dihydroxy (sodium deoxycholate and sodium glycodeoxycholate) bile salt micelles on the spectrophotometric properties and on the solubility of nitrazepam in aqueous solution, at 25.0 degrees C and at ionic strength 0.1 M in sodium chloride, has been assessed. From the results obtained it was possible to calculate the partition coefficients (Kp) of nitrazepam between aqueous and micellar phases. The partition coefficients of nitrazepam have also been determined in mixed micelles of cholate or deoxycholate with lecithin (egg yolk phosphatidylcholine), which were used as a model of the gastrointestinal tract. Drug partition was found to depend on the bile acid (number of hydroxyl groups and conjugation with glycine), and our data indicate further that addition of lecithin to bile salt micelles decreases the values of the partition coefficients in the mixed micelles at physiological pH.

Construction and evaluation of ion selective electrodes for nitrate with a summing operational amplifier. Application to tobacco analysis

In this paper, the construction and evaluation of an electrode selective to nitrate with improved sensitivity, constructed like a conventional electrode (ISE) but using an operational amplifier to sum the potentials supplied by four membranes (ESOA) is described. The two types of electrodes, without an inner reference solution, were constructed using tetraoctylammonium bromide as sensor, dibutylphthalate as solvent mediator and PVC as plastic matrix, the membranes obtained directly applied onto a conductive epoxy resin support. After the comparative evaluation of their working characteristics they were used in the determination of nitrate in different types of tobacco. The limit of detection of the direct potentiometric method developed was found to be 0.18 g kg(-1) and the precision and accuracy of the method, when applied to eight different samples of tobacco, expressed in terms of mean R.S.D. and average percentage of spike recovery was 0.6 and 100.3%, respectively. The comparison of variances showed, on all ocassions, that the results obtained by the ESOA were similar to those obtained by the conventional ISE, but with higher precision. Linear regression analysis showed good agreement (r=0.9994) between the results obtained by the developed potentiometric method and those of a spectrophotometric method based on brucine, adopted as reference method, when applied simultaneously to 32 samples of different types of tobacco.

A fast and reliable spectroscopic method for the determination of membrane--water partition coefficients of organic compounds

Partition coefficients (Kp) between egg yolk phosphatidylcholine multilamellar vesicles and water were determined for two nonsteroidal anti-inflammatory drugs (indomethacin and acemetacin) using two independent methodologies: derivative spectrophotometry and variation of the experimental acidity constant in the presence of increasing vesicle concentration. Second-derivative spectrophotometry allowed for total elimination of background signal effects arising from lipid vesicles, without the need for separation techniques that may disturb equilibrium states. By using a model based on a simple partition, the values of K(T)p can be obtained directly; furthermore, by performing determinations at two different pH values it is possible to calculate partition coefficients for the neutral and negatively charged forms of the drugs (K(AH)p and K(A)p). In the other methodology, values of apparent acidity constants (K(app)) were determined by spectrophotometry at different pH values and different lipid concentrations, and an increase in K(app) with decreasing lipid concentration was observed for both drugs, and from this dependence it was possible to calculate K(AH)p and K(A-)p for each drug. These values were used as a check for those obtained by derivative spectroscopy, which has proven to be a reliable and more expeditious method to obtain K(AH)p and K(A-)p .

Enzymatic determination of choline in milk using a FIA system with potentiometric detection

The development of a FIA system for the determination of total choline content in several types of milk is described. The samples were submitted to hydrochloric acid digestion before injection into the system and passed through an enzymatic reactor containing choline oxidase immobilised on glass beads. This enzymatic reaction releases hydrogen peroxide which then reacts with a solution of iodide. The decrease in the concentration of iodide ion is quantified using an iodide ion selective tubular electrode based on a homogeneous crystalline membrane. Validation of the results obtained with this system was performed by comparison with results from a method described in the literature and applied to the determination of total choline in milks. The relative deviation was always < 5%. The repeatability of the method developed was assessed by calculation of the relative standard deviation (RSD) for 12 consecutive injections of one sample. The RSD obtained was < 0.6%.

Phenolic acids and derivatives: studies on the relationship among structure, radical scavenging activity, and physicochemical parameters

The antiradical activity of caffeic acid (1), dihydrocaffeic acid (5), and their corresponding n-alkyl esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) method. Dihydrocaffeic acid (5) was the most potent compound, having an antiradical effect higher than that of (+/-)-alpha-tocopherol, whereas caffeic acid (1) was less efficient. Esterification of the carboxyl group of dihydrocaffeic acid (5) had a dramatic effect on its antiradical potency, but similar effects were not observed for caffeic acid (1) derivatives. The n-alkyl esters of both phenolic series had similar potencies, and their antiradical activities were independent of the alkyl chain length. Dose-dependent scavenger effects were found in both series. Acid-base properties of the compounds, evaluated by using potentiometry and spectrophotometry, showed that the catechol moiety had pK(a2) and pK(a3) values of 9. 24-9.02 and 11.38-10.99 in the dihydrocaffeic series and 8.48-8.24 and 11.38-11.07 in the caffeic series, respectively. Antiradical activity and pK(a) values of the compounds were not related.

Sequential injection system for the spectrophotometric determination of reducing sugars in wines

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described. The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with 2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the interference of some coloured compounds. In this way, direct sample introduction into the system was possible, without any previous treatment of the wine samples. The proposed method can be applied to the determination of reducing sugars in two concentration ranges: from 2 to 25 g l(-1) (table wines) and from 20 to 140 g l(-1) (Port wines). To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational parameters were changed in the controlling software. A sampling-rate of 14-18 samples per hour was obtained with good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) <2.1%). The results obtained from 19 wine samples were comparable to those obtained by the reference method.

Spectrophotometric flow injection determination of total phosphorus in beer using on-line UV/thermal induced digestion

A flow injection system for the automatic determination of total phosphorus in beer is described. The developed manifold uses a two-stage photooxidation/thermal digestion procedure together with oxidizing and hydrolyzing reagents to convert all forms of phosphorus compounds to orthophosphate. Polyphosphates are hydrolyzed by acid and heat, and organo-phosphates are digested by UV-catalyzed peroxodisulfate oxidation. The orthophosphate formed is then spectrophotometrically determined by the phosphomolybdenum blue reaction, using stannous chloride as reducing agent. The results obtained for a set of 19 beer samples (with concentrations from 120 to 735 mg P/L) were in good agreement with the reference method, the maximum relative deviation found being 4.7%. Relative standard deviations for ten consecutive determinations were lower than 1.5%, and a detection limit of 1 mg P/L was achieved.

Acid-base properties and solubility of pindolol, diazepam and chlordiazepoxide in SDS micelles

The effect of sodium dodecyl sulphate (SDS) on the acid-base properties and on the solubility of a beta-blocker (pindolol) and of two benzodiazepines (diazepam and chlordiazepoxide) has been assessed. The study was performed by potentiometric and spectrophotometric determinations of the acidity constants and by spectrophotometric evaluation of the solubilities of the pharmaceutical drugs in aqueous solution and in solutions to which was added SDS with concentrations below and above the critical micelle concentration (cmc), at 25 degrees C and at an ionic strength 0.1 M (NaCl). The effect of the organized assemblies on the pKa values was quantified by the application of two theoretical models that differ in the inclusion of ionic exchange between positively charged species in solution. These models have allowed the determination of the binding constants for drug/micelle and yielded values in good agreement with those obtained by the solubility method, and in addition provide a more detailed picture of the effect of drug charge on its partition. The results can be taken to evidence different interaction modes of the drugs with the SDS micelles.

Electrochemical behaviour of Venlafaxine and its determination in pharmaceutical products using square wave voltammetry

An electrochemical method for the determination of Venlafaxine in pharmaceutical formulations recently available on the European market is described. The electrochemical oxidation of Venlafaxine was studied at a HMDE electrode over a wide pH range (1.9-10.0) of buffered aqueous solutions using different potential sweep techniques. The results obtained showed that the best definition of the analytical signals was found in boric acid/potassium tetrahydroxoborate buffer at pH 8.7 using anodic stripping square wave voltammetry. Recovery trials were performed to assess the accuracy of results and these were compared to those provided by a HPLC technique according to the method described in literature and to the features of the pharmaceutical formulations. A relative deviation of < 0.2% was obtained. With the developed methodology, the limit of detection was 0.124 mg/l.

Monosegmented flow-analysis of serum cholesterol

A monosegmented flow system is designed for enzymatic spectrophotometric determination of cholesterol in blood serum. The sample (4.5 microliters), enzymatic reagent (150 microliters) and an air plug (100 microliters) are simultaneously inserted into a carrier stream buffered to pH 7.4 (potassium dihydrogenphosphate). In order to avoid the step of air removal, a relocating detector was used. This system handles about 42 samples per hour, yielding precise results (R.S.D. usually < 3.0%). Sensitivity is 46 mAU 1/mmol (mAU stands for milliabsorbance units), being the method linear up to 10.3 mmol/l cholesterol. Accuracy was assessed by running 30 samples already analysed by a conventional procedure: no statistical difference between methods was found at the 95% confidence level.

Fluorimetric and solubility studies of nadolol and atenolol in SDS micelles

The effect of sodium dodecyl sulfate (SDS) micelles on the spectrofluorimetric intensities and on the solubility of two beta-blockers (atenolol and nadolol) were studied at 25.0 +/- 0.1 degrees C and I = 0.1 M NaCl. From the dependence of these physical properties on SDS concentration it was possible to calculate the binding constants drug-micelle, and it was found that both techniques yield similar results for the binding constants, and that are in agreement with those calculated from the effect of micelles on the apparent acidity constants of the beta-blockers.

Tetracycline, oxytetracycline and chlortetracycline determination by flow injection potentiometry

This paper describes tetracycline (TCH), oxytetracycline (OTCH) and chlortetracycline (CTCH) determination by flow injection potentiometry. In the flow system proposed TC samples are inserted in a carrier solution and converged with a Cu(II) solution of known concentration; the Cu(II) decrease due to its complexation with tetracyclines (TC) was monitored. The detector used was a homogeneous crystalline CuS/Ag2S double membrane tubular electrode with increased sensitivity. The present system allows tetracyclines determinations within a 48.1-4.8 x 10(3) ppm for TCH, 49.1-4.9 x 10(3) ppm for OTCH and 51.5-5.1 x 10(3) ppm for CTCH and a precision better than 0.4% for the three TC species. This procedure accomplishes 150-200 samples h(-1) with a Cu(II) consumption of about 13 microg determination(-1).

Cefuroxime selective electrodes for batch and FIA determinations in pharmaceutical preparations

Different cefuroxime selective electrodes, without internal reference solution and comprising PVC membranes, were constructed and evaluated. Membranes were prepared with cefuroxime tetraoctylammonium (A) or cefuroxime bis(triphenylphosphoranylidene)ammonium (B) as ion-exchanger, 2-nitrophenyl octyl ether (X) or bis(2-ethylhexyl)sebacate (Y) as plasticizing mediator solvent and 4-tert-otcylphenol (TOP) as additive. From the comparative evaluation of the described electrodes, membranes comprising 2-nitrophenyl octyl ether, cefuroxime tetraoctylammonium and 4-tert-otcylphenol presented better working characteristics. For these electrodes (type XA-TOP), with a lifetime > 5 months, a lower limit of linear range of 2.8 x 10(-4) M, a practical detection limit of 1.3 x 10(-4) M, a reproducibility of approximately +/-0.6 mV day(-1) and a slope of -50.4 mV decade(-1), under H3PO4/NaH2PO4 solutions (pH 3.5; I =0.1 M), were found. The presence of the additive on the membranes was of crucial importance for the electrodes good characteristics. Interference from sulphate, chloride, nitrate, iodide, cefaclor, cefadroxil, cefazolin and cephradine, on the electrodes behaviour was evaluated. Only a slight interference from nitrate and iodide was recorded, being type XA-TOP electrodes the most selective units. Electrodes with a tubular configuration prepared with type XA-TOP membranes, aiming flow injection analysis, were also constructed. When these tubular potentiometric detectors were evaluated in a double-channel flow injection manifold, with 3.5 pH and 0.1 M ionic strength conditions, significantly better working characteristics than those of the corresponding conventional electrodes, namely higher slopes (-54.6 mV decade(-1)) and better reproducibilities (+/-0.2 mV day(-1)), were found. Both conventional and tubular type XA-TOP electrodes were used for injections analyses by batch and FIA, respectively, presenting low consumption of samples and reagents. Relative error deviations to the reference procedures <3.0% were found.

Merging zones standard addition technique for determination of copper in beer by flow injection atomic absorption spectrophotometry

A flow injection system for determination of copper in beer by atomic absorption spectrophotometry by the standard additions method is described. The manifold, based on the merging zone technique, prevents the burner head from clogging, as observed with the conventional reference method. With 5 standard additions, results are comparable with those of the reference method. Relative deviations were less than 5.8%, precision was better than 6.4%, and sampling rate was about 30 samples/ h. A less precise, less accurate, but faster procedure (75 samples/h) is possible with only 2 standard additions. The detection limit was 5 micrograms/L.

An automatic determination of caffeine in soft drinks using flow injection system with amperometric detection

An automatic procedure based on a flow injection analysis manifold has been developed for the determination of caffeine in soft drinks using an amperometric detection (+1.70 V vs AgCl/Ag). The sample and standards were injected without pre-treatment, with a sampling rate of 120 determinations per hour. The determination of caffeine in several soft drinks available in Portugal using the developed automatic system provided results with mean recovery values between 98% and 103% and a mean standard deviation between 2% and 5%. The results obtained were compared with those given by the reference method recommended by AOAC. Relative deviation was always less than 4%. Reproducibility of the method was assessed by the relative standard deviation (RSD%), values of which were less than 2%.

Acid/base properties of beta-blockers and benzodiazepines in sodium dodecyl sulfate micelles. A spectrophotometric and potentiometric study

The effect of sodium dodecyl sulfate (SDS) micelles on the acid-base properties of two family of pharmaceutical drugs (beta-blockers and benzodiazepines) at 25 degrees C and I = 0.1 M NaCl have been studied. The characterization of the several solution equilibria for the system drug/SDS micelle solution was performed by potentiometry and spectrophotometry, below and above the critical micelle concentration (cmc). Two widely used models have been applied to quantify the effect of micelles on the pKa of the drugs, and the results obtained point to different interactions of each family of drugs with the micelles.

Determination of SO(2) in Wines Using a Flow Injection Analysis System with Potentiometric Detection

This paper describes the development and application of a flow injection analysis system manifold comprising a gas diffusion unit and a potentiometric detector to the determination of free and total SO(2) in white and red wines. A homogeneous crystalline iodide double-membrane tubular electrode was used as detector. SO(2) determination based on the Ripper method was carried out by dosing the iodide formed in the oxidation of SO(2) with iodine, followed by the separation of the formed compound through a diffusion Teflon membrane. The results obtained from the analyses of free and total SO(2) in 30 wine samples showed good agreement between the proposed method and the rapid assay method recommended by the UE and OIV. The relative error deviations of the results obtained by both methods were <6%. This procedure is suitable for samples with approximately 3.2-180 mg L(-)(1) SO(2), performing determinations of 75-100 samples h(-)(1).

Copper(II) increases bile acid binding to asparagine

Interactions of two bile acids (cholic and glycocholic acids) with asparagine have been studied by potentiometry in aqueous solutions under conditions similar to those observed in biological fluids (37 degrees C and I = 0.15 M NaCl), and in the absence and presence of copper(II). To characterize the equilibria for the systems copper(II)/bile acid/asparagine, specifically to assess cooperative binding between bile acids and asparagine, the acidity constant of asparagine and formation constants for copper(II)/bile acid and copper(II)/asparagine were also obtained under the same conditions. The results obtained suggest cooperativity in the binding of bile acid to asparagine in the presence of copper(II).

Ion-selective electrodes for promethazine determinations in pharmaceutical preparations and application to flow injection analysis

The construction and evaluation of PM-selective electrodes with a conventional configuration and without internal reference solution are described. Two different PVC membranes were prepared with PM tetraphenylborate dissolved in 2-nitrophenyl octyl ether (type A) or bis (2-ethylhexyl)sebacate (type B). When the electrodes were evaluated in 0.01 M ionic strength solutions, both presented linear responses from 5 x 10(-5) to 1 x 10(-2) M, slopes close to the theoretical value, practical detection limits of approximately 2 x 10(-5) M, reproducibilities of +/- 0.2 mV/day, and a quick response (< 20 s). Using phosphate buffer solutions (pH 6.0), type B electrodes presented a lower practical detection limit and a better reproducibility than type A. Selectivity against several cations was assessed by the separated solutions method, and the type B electrodes were generally more selective. The type B membrane was also used for the construction of tubular electrodes for the automatic analysis of pharmaceutical products by flow injection analysis (FIA). These tubular detectors, evaluated in a low dispersion FIA system, presented better selectivity and sensitivity than the corresponding conventional ones. Several pharmaceutical preparations were analyzed with both conventional and tubular electrodes. The results obtained by FIA presented relative deviations of < 2% when compared with those obtained from the United States Pharmacopoeia monographs.

Simultaneous assay of nitrite, nitrate and chloride in meat products by flow injection

A flow injection (FI) analytical method for the simultaneous assay of nitrite, nitrate and chloride in meat products is reported. The method is based on the potentiometric determination of chloride using a tubular ISE and on the spectrophotometric determination of nitrite. The FI system consisted in splitting the flow after potentiometric detection using a tubular detector and the subsequent confluence of the flow before reaching the spectrophotometric detector. This allowed the reduction of nitrate to nitrite in part of the sample plug on an on-line copper cadmium reductor column. Since each channel had a different residence time, two peaks were obtained for nitrite and nitrite plus nitrate. Spectrophotometric determination was made after a diazotization-coupling reaction. The results obtained were in good agreement with reference procedures and showed adequate precision (RSDs less than 6% for chloride and nitrite and 2% for nitrate). A high sampling rate was obtained (120 determinations per hour corresponding to 40 samples per hour).

Construction and evaluation of PVC conventional and tubular tripelennamine-selective electrodes: their application in pharmaceutical preparations

The construction and evaluation of tripelennamine conventionally-shaped ion-selective electrodes and tubular detectors for the determination of this compound in pharmaceutical formulations are described. Electrodes with conventional configuration have been constructed without an internal reference solution, using several types of immobilized ionic sensors in PVC. The different electrode membranes were prepared by using tripelennamine tetraphenylborate as ionic-exchanger, dissolved in 2-nitrophenyl octyl ether (type A), dibutylphthalate (type B) and bis-(2-ethylhexyl)sebacate (type C) as plasticizer solvents. The general working characteristics of the different types of conventional electrodes were evaluated in tripelennamine solutions, with adjusted ionic strength, showing a linear response in the concentration range of about 4 x 10(-5) - 1 x 10(-1) M and a slope near the theoretical value. The electrodes presented a fast response (> 20 s) and a high reproducibility (> or = 0.2 mV per day). The electrode selectivity in the presence of some interferents, such as sodium, potassium, lithium, ammonium, chlorpheniramine, diphenydramine, promethazine, meclizine and pentazocine, was good, particularly for those whose sensor membrane was prepared with tripelennamine tetraphenylborate dissolved in 2-nitrophenyl octyl ether (type A). Tubular detectors were also prepared using the same sensor membrane and were evaluated in a low-dispersion flow-injection manifold. Under these conditions the detectors presented response characteristics similar to those of the corresponding conventionally-shaped electrodes. The analysis of different pharmaceutical forms (creams, syrups and gels) gave good results with mean recoveries of 99.8-100.6% when the experiments were conducted by direct potentiometry and 99.9-100.4% where the same determinations were conducted by flow-injection analysis with tubular detectors.

FIA titrations of ephedrine in pharmaceutical formulations with a PVC tetraphenylborate tubular electrode

A flow injection system for the titration of ephedrine in pharmaceutical products with potentiometric detection was developed. For this purpose a tetraphenylborate tubular electrode was constructed. The electrode was prepared without inner reference solution and with a PVC membrane based on tetrapentylammonium tetraphenylborate as ion exchanger and 2-nitrophenylphenyl ether as mediator solvent. Its operational characteristics were evaluated in a low dispersion manifold and compared with more conventionally shaped electrodes using the same sensor. In the pH range 2.5-11.5, the electrodes showed linear response between 3.8 x 10(-6) and 0.1 M with a slope of -56.4 mV/log[BPh4]. Ephedrine determinations in pharmaceutical products were carried out in a single channel manifold with a mixing chamber incorporated and using the tubular electrode as detector. Recovery rates of 98.6 +/- 2.5% were obtained in the analysis of tables, nasal drops and syrups with a sampling rate of about 60 h-1.

Potentiometric determination of formation constants of copper(II)/bile acid/peptide in aqueous solution

A potentiometric method was used to study the equilibria in aqueous solution for the systems copper(II)/bile acid salt/peptide [bile acid salt-sodium cholate or glycocholate; and peptide-glutamic acid (glutamate), glutamine or glutamylglutamic acid], specifically to assess cooperative binding between small peptides and bile acids in the presence of copper(II). The results obtained suggest large cooperativity in formation of ternary complexes with amino acids when they are coordinated to copper(II) as bidentate ligands.

Sequential flow-injection determination of ionic and total calcium in saliva

In this paper a flow injection manifold for the sequential determination of ionic and total calcium in a small (75 microL) sample of saliva is presented. This setup incorporates two detectors, a tubular potentiometric detector and an atomic absorption spectrophotometer, for determining the ionic and total calcium, respectively. Furthermore, the saliva samples can be injected directly into the manifold without any pre-treatment or loss of carbon dioxide. The results of the analyses of 20 saliva samples were in good agreement with those obtained by the two reference procedures, the direct potentiometry for ionic calcium and atomic absorption spectroscopy for total calcium. The paired Student's t-test showed that there were no statistical differences in the results obtained. The relative standard deviations of ten consecutive measurements of the same salive sample were approximately 3% for ionic calcium and 4% for total calcium. Effects of differences in coexisting ions, ionic strength, and pH between standard solutions and samples were negligible.

Optimal design of an enzymatic reactor for flow injection analysis

A simulation procedure for the optimization of enzymatic reactors used in sandwich flow injection systems is evaluated. The system is modeled as a plug-flow reactor with axial dispersion. To calibrate it, dispersion coefficients can be evaluated using residence time distribution techniques; meanwhile, enzymatic kinetics must be determined for the system considered, according to the values of the substrate conversion attained. The model has been linked to an optimization routine based on the Powell algorithm. The proposed approach has been evaluated in a system performing simultaneous determinations of glucose and glycerol, considered the common carbon sources in a fermentation process.

PVC membrane electrode without inner reference solution for the direct determination of ephedrine in pharmaceutical preparations

A PVC membrane electrode, without inner reference solution, based on an ion association extraction system responding to ephedrine is described. It incorporates an ephedrine-tetrakis (4-chlorophenyl)borate ion-pair complex in 2-nitrophenyloctyl ether. The prepared electrode exhibits a near Nernstian response (57.5 mV per decade) over the concentration range of 2 x 10(-5)-10(-1) M ephedrine in solutions of pH 2.5-9. The reproducibility of the electrode potentials were +/- 1 mV by day during at least 6 months. Response time was about 6 s for ephedrine concentrations between 10(-5) and 10(-1) M. Determinations of ephedrine in pharmaceutical preparations (tablets, nasal drops and syrups) by direct potentiometry gave an average recovery of 99.1% (w/w) and a mean standard deviation of 1.9% (w/w).

Flow injection system based on the sandwich technique for saving expensive reagents

We report the application of a sandwich technique in flow injection systems which afford low consumption of expensive reagents and two reagent recirculation systems. The potential applicability of the technique thus developed was assessed by determining glucose in serum samples by the enzymatic glucosidase/peroxidase method. It was possible to perform up to 450 determinations with the same amount of reagent used to perform 50 determinations by batch procedures. The sampling rate was 80 determinations per hour with a 0.9% relative standard deviation.

Vitamins B1 and B6 tubular electrodes as FIA detectors; their use in the analysis of pharmaceutical products

Ion-selective electrodes without an inner reference solution and tubular potentiometric detectors for the determination of vitamins B1 and B6 in pharmaceutical preparations by flow injection analysis (FIA) are reported. The membranes were prepared with the vitamin tetra(2-chlorophenyl)borate (TCPB) dissolved in o-nitrophenyloctyl ether (o-NPOE) and immobilized on PVC. Intrinsic behaviour of the tubular detectors was assessed using a low-dispersion single-channel FIA manifold and was compared with conventionally-shaped electrodes using the same membrane. Data obtained in the determination of vitamins B1 and B6 in pharmaceutical preparations with a double channel flow injection manifold incorporating the tubular detectors are presented and compared with those obtained by the U.S. Pharmacopeia method and by direct potentiometry with conventionally-shaped electrodes.

Flow injection analysis of inorganic cationic species in serum and urine

This paper describes three flow injection analysis (FIA) systems for the automatic determination of sodium, potassium, lithium, calcium, magnesium, zinc, copper and iron in certain biological fluids and compares the results obtained to those of flame photometry and atomic absorption spectrometry. The set-ups were designed to allow the samples to be prepared in the same manner as that used for batch procedures with the same analytical instrument. For determinations requiring a high sample dilution, it was found of definite advantage to split the stream and pass large amounts of liquid through the detection systems. The comparison of the results obtained by FIA and conventional methods yielded correlation coefficients in the range 0.990 to 0.999. The proposed methodology show good precision, with variation coefficients between 0.5% to 5%.

Solid-state PVC flow-through benzoate electrode

A general construction procedure for conventional shape ion-selective electrodes based on a conductive support prepared with a mixture of a non-conductive epoxy and graphite was used in the preparation of a flow-through benzoate electrode to be used as potentiometric detector in flow injection analysis manifolds. The membranes were prepared from tetraoctylammonium benzoate in o-nitrophenyloctylether immobilized on PVC. The results of the assessment of the tubular electrodes behaviour in low dispersion manifolds against that of conventional electrodes with the same membrane are reported. Data obtained with a double-channel flow injection manifold incorporating these tubular detectors for benzoate determinations in several commercially available pharmaceutical preparations are also presented.

[The growth curve in asthmatic children]

The growth of 209 children with moderate and severe bronchial asthma seen at two different Health Care Centers for Bronchial Asthma Patients: (ICr and USP) was studied. The two groups differ mainly in socioeconomic level. Age at the onset of the disease, as well as duration and severity of the illness were considered. The first manifestations of the disease occurred before two years of age in 68.4% of the children. There was a predominance of males over females, with an almost 2:1 ratio in severe cases. The relationship between socioeconomic level and severity of the disease was highly significant (p less than 0.002). Weight and height were predominantly in the 50 percentile or below. This predominance was more evident for height. The height percentiles were significantly lower for the ICr group (p less than 0.01). Only 5.7% of the population studied had been submitted to prolonged (more than 3 months) corticoid treatment.