Cristina Almeida

Automatic potentiometric flow titration procedure for ascorbic acid determination in pharmaceutical formulations

A flow procedure for the determination of ascorbic acid in pharmaceutical formulations exploiting potentiometric titration is described. The method is based on the reduction of IO3- by ascorbic acid and the detection was carried out employing a flow-through ion selective electrode for iodide. The flow network controlled by a microcomputer was designed to implement multicommutation for ease of operation and robustness. The titration system allowed the determination of ascorbic acid in pharmaceutical formulations with concentrations ranging from 7.5 to 15.0 mmol l(-1). No significant differences at the 95% confidence level were observed in comparison with results obtained by a manual procedure. Merit figures of results such as a relative standard deviation of 1.0% (n=6) and a reagent consumption of 21.4 mg IO3- per determination were obtained.

Lipid profile changes by high activity anti-retroviral therapy

OBJECTIVE Study of the lipid profile in patients infected with HIV treated with different combinations of high activity anti-retroviral therapy (HAART). DESIGN AND METHODS A retrospective cohort study of the lipid profile in patients undergoing HAART. The study analyzes the evolution of concentrations of triglycerides (TG), total cholesterol (TC), LDL-cholesterol (LDLc) and HDL-cholesterol (HDLc) in a period of at least 3 years of treatment. From a total of 750 clinical cases analyzed in Hospital Joaquim Urbano (Oporto, Portugal) 124 patients were selected for this study. RESULTS After 3 years of treatment, we observed the development of dyslipidaemia by increases in TG (17%), TC (29%) and LDLc (9%), particularly in patients treated with a combination of drugs which included protease inhibitors (PI). Moreover, the non-nucleoside reverse transcriptase inhibitors (NNRTI) were associated with better lipid profile. The increase of 46% in HDLc was the most surprising finding. CONCLUSIONS The results indicate that patients with HAART have a more atherogenic lipidic profile with increased TC, LDLc and TG levels. Since the effectiveness of NNRTI is similar to that of PI, but with a smaller atherogenic profile, it should be the first choice drug to be selected in the HIV treatment.

Fatty Acid Profile of Human Milk of Portuguese Lactating Women: Prospective Study from the 1st to the 16th Week of Lactation

Background/Aims: Fatty acid (FA) composition varies over the course of the day and during lactation. The aim of this study was to evaluate FA composition and its compositional stability in human milk, from day 7 to week 16 of lactation. Methods: Human milk was collected from all feedings over 24 h at day 7 and weeks 4, 8, 12 and 16 of lactation in 31 lactating women. FAs were analyzed through gas chromatography. Comparisons were made with analysis of variance. Results: Total monounsaturated FAs decreased from 33.04 ± 2.58% wt/wt at day 7 to 31.48 ± 3.32% wt/wt at week 16 of lactation, much at the expenses of the decrease in the major monounsaturated FA found in human milk, oleic acid. Main polyunsaturated FAs n-6 and n-3 showed fluctuations from day 7 up to week 16 of lactation, but with no statistical significance. Arachidonic acid significantly decreased from transitional to mature milk. Conclusions: The FA profile obtained throughout the study time points presented very low levels of oleic acid and very high linoleic acid/α-linoleic acid ratios which reflect recent changes in Portuguese women’s food patterns. Despite this, the ascorbate/dehydroascorbate ratio remained constant during the study, suggesting a protective metabolic mechanism.

Trace element compositional changes in human milk during the first four months of lactation

Abstract The aims of this paper were to evaluate changes in specific oligoelements in human milk during the first four months of lactation and to correlate such changes with total antioxidant status (TAS) and other parameters, such as the mother’s age, primipara versus multipara, and supplement intake. Milk samples were collected from 31 lactating women following 1, 4, 8, 12 and 16 weeks after birth. Trace levels of 13 elements were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The results obtained for the oligoelements exhibited a decrease in concentration from 7 days to 4 months of breast-feeding, with exceptions. Correlations were found between TAS and Co, V, Rb and Tl. Between primipara and multipara, differences were found for Ni and Rb. Regarding the mother’s age, correlation was found for Rb and Ba (increased for mothers older than 30 years). Increased amounts of Rb, Mo and Tl at any lactation period appeared in women who took supplements.

Biochemical markers of neonatal myocardial dysfunction

Introduction. Cardiac ultrasounds (US) are not always available at the bedside. Cardiac Troponin I (cTnI), CK-MB and NT-proBNP may be an alternative or complementary to influence evaluation and treatment. Objectives. To determine reference ranges of biochemical markers cTnI, CK-MB and NT-proBNP in normal neonates. Methodology. Cord and blood samples were collected from neonates and the above biochemical markers were determined. Ultrasounds were performed blindly. Results. CK-MB remains constant from cord blood to the first day, declining thereafter to almost half the values (81.5 vs 52.0 U/l); cTnI increases from 0.004 to 0.058 ng/ml by 72 h falling to 0.030 by day 10; NT-proBNP peaks by 24 h (5085.5 pg/ml), subsiding to 3388.5 pg/ml by day 3, falling to 1316.0 pg/ml by day 10. Conclusions. CK-MB, mostly of muscle origin and reflecting labor stress or injury, is not to recommend as a measure of myocardial damage in the neonate. The rise in cTnI may be explained by a degree of myocardial involvement, albeit physiological. The initial rise and subsequent fall of NT-proBNP represents the physiological ventricular overload of transient birth adaptation.

Automatic flow titrator based on a multicommutated unsegmented flow system for alkalinity monitoring in wastewaters

Abstract A full automatic flow system based on potentiometric titration for alkalinity monitoring in wastewater treating plants is presented. Titration to an end-point of pH 5.75 partial alkalinity (PA) and then to pH 4.3 intermediate alkalinity (IA) allows to distinguish the relative buffering contributions of both bicarbonate and volatile acids in anaerobic digesters and, thus, the attainment of a IA:PA ratio which is a sensitive parameter of digestion monitoring that increases rapidly with the process upset. The titration approach is based on a time-based sequential introduction of increasing titrant and decreasing titrand volumes into a mixing chamber. The theoretical model for the titration process already presented and discussed was used to determine the titrand concentration without prior calibration. The interface between the analytical system and the anaerobic digester was also developed, allowing completely automated on-line monitoring of alkalinity. The results obtained were reproducible (R.S.D. lower than 2.4 and 5.1% for repeatability and reproducibility, respectively) and in good agreement with those given by the comparative method.

Precipitation titrations using an automatic titrator based on a multicommutated unsegmented flow system

An automatic flow titrator based on a multicommutated unsegmented flow system was used to perform precipitation titrations with potentiometric detection. The titration approach is based on sequential introduction of increasing titrant and decreasing titrand volumes into a mixing chamber. The system allows the attainment of complete curves, the titration end point being determined by the Gran method, as is usually employed in batch potentiometric titrations. The theoretical model for the analytical process is presented and discussed and the determination of titrand concentration is performed without any prior calibration. The automatic flow titrator developed was applied to chloride determination in bottled natural waters and the results obtained were reproducible (RSD 3.2 and 3.8% for repeatability and reproducibility, respectively) and in good agreement with those given by the reference procedure (relative deviation within the range from −4.6 to 4.8%).

Oxidability Determination in Waste Waters Using an Automatic Titrator Based on a Multicommutated Unsegmented Flow System

Abstract The automatic titrator based on a multicommutated unsegmented flow system was applied to redox titrations and used for oxidability determination in waters analysis. This automatic titrator allows the attainment of complete titration curves, being the determination of titrand concentration performed without requiring any prior calibration. After sample treatment (oxidation step), the oxidability determination in waste water samples was accomplished by the automatic flow titrator (titration step). Repeated determinations of standard solutions gave a 3.5% RSD (n=10, 0.010M) for repeatability and a 3.2% RSD (n=2, 0.057M) for reproducibility. Samples results (n=9) were in good agreement (t-test) with those obtained with a reference procedure.

Glycaemic profile changes by highly active antiretroviral therapy in human immunodeficiency virus-infected patients.

To study dysglycaemia in human immunodeficiency virus (HIV)-infected patients we conducted a retrospective cohort study of the glucose profile in HIV-infected patients. The fasting blood glucose was analysed taking into consideration conventional risk factors as well as HIV infection and highly active antiretroviral therapy (HAART). One hundred seventy-three cases were selected for this study. Five risk factors had significant effects (p < 0.05) on glucose levels: age, body mass index (BMI), hepatitis C virus/hepatitis B virus (HCV/HBV) co-infection, viral load (VL), and CD4+ T-lymphocyte count. Fasting blood glucose levels increased with age (0.59 mg/dL/year), decreased with the VL (−4.1 × 10−6 mg/dL/number of viral RNA copies) and the CD4+ T-lymphocyte count (−0.016 mg/dL/cell count). Furthermore, obese patients and those co-infected with HCV/HBV were more prone to develop dysglycaemia having, on average, 15.4 mg/dL and 13.8 mg/dL higher levels, respectively, of fasting blood glucose. Despite an increase of 1.0% and 8.4% in the glucose levels noticed among HIV patients treated with non-nucleotide inhibitors of reverse transcriptase and protease inhibitors, respectively, HAART did not prove to be a significant predictor of fasting glucose levels as well as lipodystrophy and male gender. Age, BMI, HCV/HBV co-infection and HIV-related (VL and CD4+ T-lymphocyte count) factors seem to be the most influential on fasting blood glucose levels in HIV-infected individuals.

Metabolic syndrome in human immunodeficiency virus-infected patients

The objective of this study was to investigate the factors underlying the development of metabolic syndrome (MetS) in HIV-infected patients. Two hundred and sixty-six clinical cases were selected for a retrospective study. The sample was classified using the Adult Treatment Panel III guidelines and the identification of risk or protective factors associated with MetS evaluated via multivariate logistic or multinomial regressions. HIV-infected individuals diagnosed with MetS tend to be older, overweight, or obese (85% have a BMI ≥ 25), with a waist circumference > 90 cm (96.5 [88.8–105.5] cm, median [interquartile range]). Blood testing these individuals revealed high fasting levels of insulin (8.1 [5.8–21.6] pg/ml), glucose (98.0 [84.0–116.0] mg/dl), triglycerides (201.0 [142.0–267.3] mg/dl), and high-density lipoprotein cholesterol (36.5 [29.8–43.3] mg/dl) in addition with higher levels of inflammatory mediators such as high-sensitivity C-reactive protein (2.5 [1.0–4.9] mg/dl) and interleukin-6 (3.4 [2.8–3.8] pg/ml). The likelihood of HIV-infected individuals who are virally suppressed developing MetS is about 60% higher than those with acute infection. Treatment with nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors (PIs) increases the chance of developing MetS by around 2.4 times. Individuals with a lower antioxidant capacity (total antioxidant status [TAS] <1.33) have a 2.6 times higher risk of developing MetS. HIV-related chronic inflammation, a low TAS, and treatment with NRTIs in association with PIs are additional MetS risk factors.