Biomedical subjects

Boaventura F Reis

Publications and source records attributed to Boaventura F Reis.

12 recordsLinked to original sources

PubMed2006

Multicommuted flow system employing pinch solenoid valves and micro-pumps. Spectrophotometric determination of paracetamol in pharmaceutical formulations.

A multicommuted spectrophotometric flow-based procedure for the determination of paracetamol in pharmaceutical formulations is proposed. The method is based on the reaction of paracetamol with sodium hypochlorite forming N-acetyl-p-benzoquinoneimine, which reacts with sodium salicylate in alkaline medium producing a blue indophenol dye that was measured at 640nm. The flow system was designed employing four pinch solenoid valves and two solenoid micro-pumps, which were assembled aiming to obtain a compact module, resulting in minimization of reagents consumption and waste generation. Aiming to prove the usefulness of flow system an analytical procedure for paracetamol determination in pharmaceutical formulations was developed. To allow accuracy assessment samples were also analyzed using the AOAC reference method. Applying the paired t-test between results no significant difference at the 95% confidence level was observed. Other profitable features such as a linear response ranging from 5.0 to 125.0mgl(-1) (R=0.9992, n=7), a sampling rate of 60 determinations per hour, a detection limit of 0.4mgl(-1) paracetamol, a relative standard deviation of 1.5% (n=11) for a typical sample solution containing 25.0mgl(-1) paracetamol, reagent consumption of 1.28mg sodium hypochlorite and 6.4mg sodium salicylate per determination were also achieved.

Acetaminophen↗

PubMed2006

An automatic flow injection analysis procedure for photometric determination of ethanol in red wine without using a chromogenic reagent.

An automatic reagentless photometric procedure for the determination of ethanol in red wine is described. The procedure was based on a falling drop system that was implemented by employing a flow injection analysis manifold. The detection system comprised an infrared LED and a phototransistor. The experimental arrangement was designed to ensure that the wine drop grew between these devices, thus causing a decrease in the intensity of the radiation beam coming from the LED. Since ethanol content affected the size of the wine drop this feature was exploited to develop an analytical procedure for the photometric determination of ethanol in red wine without using a chromogenic reagent. In an attempt to prove the usefulness of the proposed procedure, a set of red wines were analysed. No significant difference between our results and those obtained with a reference method was observed at the 95% confidence level. Other advantages of our method were a linear response ranging from 0.17 up to 5.14 mol L(-1) (1.0 up to 30.0%) ethanol (R = 0.999); a limit of detection of 0.05 mol L(-1) (0.3%) ethanol; a relative standard deviation of 2.5% (n = 10) using typical wine sample containing 2.14 mol L(-1) (12.5%) ethanol; and a sampling rate of 50 determinations per hour.

Automation↗

PubMed2005

Micro-pumping flow system for spectrophotometric determination of anionic surfactants in water.

A novel procedure has been developed for spectrophotometric determination of anionic surfactants in water using a solenoid micro-pump as fluid-propulsion device. The proposed method is based on substitution of methyl orange (MO) by anionic surfactants in the formation of an ion-pair with the cetyl pyridine ion (CPC+) at pH 5.0. The flow network comprised four solenoid micro-pumps which, under microcomputer control, enabled sample and reagent introduction, and homogenisation in the reaction zone. The system is flexible and simple to operate and control, and sensitive and precise. The analytical plot for the anionic surfactant was linear between 1.43x10(-6) and 1.43x10(-5) mol L(-1) (0.5 to 5.0 mg L(-1); R=0.997, n=5). The relative standard deviation was 0.8% (n=11) for a sample containing 5.74x10(-6) mol L(-1) (2 mg L(-1)) surfactant. The limit of detection was 9.76x10(-8) mol L(-1) (0.034 mg L(-1)) and the sampling throughput was 60 determinations per hour. The results obtained for washing-water samples were comparable with those obtained by use of the reference method, and no significant differences at the 95% confidence level were observed.

Journal Article↗

PubMed2004

Simultaneous photometric determination of albumin and total protein in animal blood plasma employing a multicommutated flow system to carried out on line dilution and reagents solutions handling.

An automatic flow procedure for the simultaneous determination of albumin and total protein in blood plasma samples is proposed. The flow network comprised a set of three-way solenoid valves assembled to implement the multicommutation. The flow set up was controlled by means of a computer equipped with an electronic interface card which running a software wrote in QUICKBASIC 4.5 performed on line programmed dilution to allow the determination of both albumin and total protein in blood plasma. The photometric methods based on Bromocresol Green and Biuret reagents were selected for determination of albumin and total protein, respectively. Two LEDs based photometers coupled together the flow cells were employed as detector. After the adjustment of the operational parameters the proposed system presented the following features: an analytical throughput of 45 sample processing per hour for two analytes; relative standard deviations of 1.5 and 0.8% (n=10) for a typical sample presenting 34 g l(-1) albumin and 90 g l(-1) total protein, respectively; linear responses ranging from 0 to 15 g l(-1) albumin (r=0.998) and total protein (r=0.999); sample and reagents consumption, 140 microl serum solution, 0.015 mg VBC and 0.432 mg CuSO4 per determination, respectively. Applying the paired t-test between results obtained using the proposed system and reference methods no significant difference at 95 and 90% confidence level for albumin and total protein, respectively, were observed.

Albumins↗

PubMed2003

Flow-injection spectrophotometric determination of paracetamol in tablets and oral solutions.

A flow injection method is proposed for the determination of paracetamol in pharmaceutical dosage forms. The method is based on the nitration of paracetamol with sodium nitrite, and the absorption of the reaction product is measured at 430 nm in alkaline medium. Unlike other colorimetric methods used for determination of paracetamol, this method does not require the use of heat. The influence of several operating parameters is studied. The method was applied to the determination of paracetamol in oral solutions and in tablets, alone or associated with caffeine. When the results were compared with those obtained by the official HPLC method (USP 24) the relative differences found were from 0.4 to 2.3%, with relative standard deviations below 1%.

Acetaminophen↗

PubMed2003

An automatic flow procedure for the determination of 3-hydroxybutyrate in animal serum and plasma.

An automatic flow procedure based on the multicommutation concept, comprising three-way solenoid valves, for the spectrophotometric determination of 3-hydroxybutyrate in animal serum and plasma is proposed. The 3-hydroxybutyrate was enzymatically converted to acetoacetate with the reduction of NAD+ to NADH monitored at 340 nm. It was possible to carry out up to 600 determinations without a significant decrease in the analytical signal, with 5 mg of 3-hydroxybutyrate dehydrogenase immobilized on porous silica beads and packed in a column. The system enabled 60 determinations/h of 3-hydroxybutyrate in the range of 10-150 mg L(-1), with a consumption of 0.9 mg of NAD+ and 200 microL of sample per determination. A detection limit of 2 mg L(-1) for both animal serum and plasma and coefficients of variation of 1.4% and 1.2% (n = 17), respectively, were determined. Animal serum and plasma samples were analyzed without previous treatment, the results of which agreed with those obtained using the conventional method (UV kit, Sigma).

3-Hydroxybutyric Acid↗

PubMed2003

Ion-selective electrodes based on metalloporphyrins for gibberellic acid determination in agricultural products.

This work describes the construction, evaluation and analytical application of electrodes selective to the gibberellate anion for the determination of gibberellic acid in agricultural products. Several types of PVC membrane electrodes without internal reference solution were prepared using the manganese(III) complex of meso-tetraphenylporphyrin (TPP) as ionophore and dibutyl phthalate (DBP), as plasticizer. The incorporation of lipophilic chemical species as additives, was also carried out aiming the evaluation of the response characteristics of the electrodes. To accomplish the analysis of commercial agricultural products a selective membrane composed of 28.0% (w/w) of PVC, 66.0% (w/w) of plasticizer and 6% (w/w) of ionophore was used, with no additive. This potentiometric unit presented a linear response between 10(-4) and 10(-1) mol L(-1) in gibberellate, a slope of about -69 mV dec(-1) and a reproducibility of about +/-1 mV day(-1). The potentiometric analysis of gibberellic acid in commercial products was carried out by direct potentiometry and the results obtained were compared with those provided by HPLC.

Crops, Agricultural↗

PubMed2003

Automatic procedure exploiting multicommutation in flow analysis for simultaneous spectrophotometric determination of nonstructural carbohydrates and reducing sugar in forage materials.

A multicommutated flow procedure for simultaneous spectrophotometric determination of nonstructural carbohydrates and reducing sugar in forage materials is proposed. Determination of both analytes was based on the neucroine method after acid hydrolysis of nonstructural carbohydrates. Results for both analytes presented the following features: no significant difference at 90% confidence level when compared with reference method, linear response between 0.2 to 0.8% (w/v) (r = 0.999); relative standard deviations of < 2.0% (n = 10), and sampling rate of 32 determinations per hour.

Automation↗

PubMed2002

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.

Ascorbic Acid↗

PubMed2002

Potentiometric flow injection determination of glycerol in distilled spirits.

A single-line flow injection system including a tubular periodate-selective electrode without inner reference solution is proposed for glycerol determination in distilled spirits, based on oxidation of this polyol by periodate. Interferences due to 5.0 mg L(-1) Cu, 5000 mg L(-1) sucrose, and 3000 mg L(-1) fructose plus glucose were investigated. The procedure is characterized by a linear response for 20-500 mg L(-1) glycerol (r > 0.9999, n = 7), a relative standard deviation of results of <0.03, and an analytical throughput of 30 determinations per hour. Accuracy was assessed by applying the procedure to distilled spirits of sugarcane and grape already analyzed by HPLC; in addition, recoveries within 96 and 120% were obtained.

Alcoholic Beverages↗

PubMedDate not supplied

Automatic flow system titration based on multicommutation for spectrophotometric determination of total acidity in silage extracts.

A multicommutated flow titration procedure is proposed for the spectrophotometric determination of total acidity in silage extracts. The flow network comprises a set of 3-way solenoid valves, computer-controlled to provide facilities to handle the titrand, titrant, and carrier solutions by using a single pumping channel. The procedure is based on the volumetric fraction variation approach that maintains the same volume of titrand solution and varies the titrant solution step by step, to provide determination without the use of an analytical curve. The procedure is implemented by using phenolphthalein as an external indicator; the proposed algorithm was able to titrate silage extracts presenting different color intensities. Sample solutions with concentrations ranging from 10(-3) to 10(-1) mol/L total acidity could be analyzed by using 10(-2) mol/L sodium hydroxide as the titrant solution. Other advantages include a relative standard deviation of <1.0% (n = 4) for a typical silage extract solution containing 26 mmol/L total acidity; an analytical throughput of 16 determinations per hour was also achieved. Accuracy was assessed by processing a set of silage extract solutions and comparing the results with those obtained by using the conventional potentiometric titration procedure. No significant difference at the 95% confidence level was observed.

Hydrogen-Ion Concentration↗

PubMedDate not supplied

Automatic flow procedure for the determination of ethanol in wine exploiting multicommutation and enzymatic reaction with detection by chemiluminescence.

An automatic procedure for the determination of ethanol in wines using a flow system based on multicommutation and enzymatic reaction is described. Alcohol oxidase was immobilized on aminopropyl glass beads and packed in an acrylic column. The peroxide due to enzymatic reaction with ethanol reacted with luminol and generated the chemiluminescence radiation that was monitored by using a laboratory-made detector based on photodiodes. The system manifold comprised a set of 3-way solenoid valves controlled by a microcomputer furnished with electronic interfaces, which ran on software written in Quick BASIC 4.5 to provide facilities to perform on-line sample dilution, reagent addition, and data acquisition. After system parameters optimization, ethanol samples were processed without prior pretreatment. The following suitable features were achieved: linear response ranging from 2.5 to 25% (v/v) ethanol, relative standard deviation of 1.8% (n = 10), detection limit of 0.3% (v/v) ethanol, sampling rate of 23 determinations per hour, and low reagent consumption of 0.23 mg luminol and 7 mg hexacyanoferrate (III) per determination. When the results were compared with those obtained using the AOAC Official Method, no significant difference at the 90% confidence level was observed.

Acetaldehyde↗