Acid In Biological Fluids Research Articles

Evaluation of pulsed electromembrane extraction for the analysis of diclofenac and mefenamic acid in biological fluids

In the present study, electromembrane extraction (EME) and pulsed electromembrane extraction (PEME) coupled with high-performance liquid chromatography (HPLC) were compared for the extraction of two acidic drugs including diclofenac (DIC) and mefenamic acid (MEF).

Fullerene–C60–MWCNT composite film based ultrasensitive electrochemical sensing platform for the trace analysis of pyruvic acid in biological fluids

We propose development of a novel electrochemical sensor based on fullerene-multi-walled carbon nanotubes composite film for the sensitive determination of the pyruvic acid in biological fluids. The developed sensor was characterized by cyclic voltammetry. The nanocomposite film of C60–MWCNTs on GCE exhibits electrocatalytic activity towards pyruvic acid reduction and also decreases the reduction overpotential. The influence of the optimization parameters such as pH and effect of loading of composite mixture of C60 and MWCNTs on the electrochemical performance of the sensor were evaluated. Various kinetic parameters such as electron transfer number (n=2), proton transfer number (m=2) and charge transfer coefficient (α=0.56) were also calculated. Under optimized conditions, the squarewave reduction peak current was linear over the concentration range of 2.0–55nM with the detection and quantification limit of 0.1nM and 0.8nM respectively. The fabricated sensor was successfully applied to the detection of pyruvic acid in biological samples with good recovery ranging from 97.6% to 103.6%.

Graphene nanosheets as a sensing platform for amplified electrochemical measurement of quercetin and uric acid in biological fluids

A simple and selective electrochemical method was investigated for the simultaneous determination of quercetin (Qu) and uric acid (UA) in aqueous media (citrate buffer solution, pH 4.0) on a glassy carbon electrode modified with graphene nanosheets as a sensing platform (GNSs/GCE). Cyclic voltammetry, transmission electron microscopy, and Fourier transform infrared spectroscopy were employed to characterize the nanostructure of the sensor. Separation of the oxidation peak potentials for Qu and UA was about 160 mV, and the anodic currents for the oxidation of both Qu and UA are greatly increased at GNSs/GCE, which makes it suitable for simultaneous determination of these compounds. The detection limits were 0.0011 and 0.0137 μmol/L for Qu and UA, respectively. The method was applied to the determination of Qu and UA in human blood serum and urine samples.

Magnetic solid phase extraction of mefenamic acid from biological samples based on the formation of mixed hemimicelle aggregates on Fe3O4 nanoparticles prior to its HPLC-UV detection

A novel and sensitive solid phase extraction method based on the adsorption of cetyltrimethylammonium bromide on the surface of Fe3O4 nanoparticles was developed for extraction and preconcentration of ultra-trace amounts of mefenamic acid in biological fluids. The remarkable properties of Fe3O4 nanoparticles including high surface area and strong magnetization were utilized in this SPE procedure so that a high enrichment factor (98) and satisfactory extraction recoveries (92-99%) were obtained using only 50mg of magnetic adsorbent. Furthermore, a fast separation time (about 15min) was achieved for a large sample volume (200mL) avoiding time-consuming column-passing process of conventional SPE. A comprehensive study on the parameters effecting the extraction recovery such of the amount of surfactant, pH value, the amount of Fe3O4 nanoparticles, sample volume, desorption conditions and ionic strength were also presented. Under the optimum conditions, the method was linear in the 0.2-200ngmL(-1) range and good linearity (r(2)>0.9991) was obtained for all calibration curves. The limit of detection was 0.097 and 0.087ngmL(-1) in plasma and urine samples, respectively. The relative standard deviation (RSD %) for 10 and 50ngmL(-1) of the analyte (n=5) were 1.6% and 2.1% in plasma and 1.2% and 1.9% in urine samples, respectively. Finally, the method was successfully applied to the extraction and preconcentration of mefenamic acid in human plasma and urine samples.

Mass spectrometric quantification of L-arginine and its pathway related substances in biofluids: The road to maturity

The amino acid L-arginine together with its metabolites and related substances is in the center of many biologically important pathways, especially the urea cycle and the nitric oxide (NO) synthesis. Therefore, the concentrations of these substances in various biological fluids are of great interest as predictive markers for health and disease. Yet, they provide major analytical difficulties as they are very polar in nature and therefore not easily to be separated on standard reversed phase HPLC stationary phases. Furthermore, as endogenous substances, no analyte-free matrix is available, a fact that results in complicated calibration procedures. This review evaluates the analytical literature for the determination of L-arginine, symmetric dimethylarginine, asymmetric dimethylarginine, monomethylarginine, L-citrulline, L-ornithine, L-homoarginine, agmatine and dimethylguanidinovaleric acid in biological fluids. Papers are discussed, which were published since 2007 and describe methods applying capillary electrophoresis (CE), gas chromatography (GC), reversed phase HPLC or polar phase HPLC, coupled to mass spectrometric quantification. Nowadays, many carefully developed and validated methods for L-arginine and its related substances are available to the scientific community. The use of stable isotope labeled internal standards enables high precision and accuracy in mass spectrometry-based quantitative analysis.

Modified hplc method of determination of the valproic acid in biological fluids

Proposed modified HPLC method for determination of valproic acid in biological fluids. Created solid-phase extraction of valproic and heptanoic acids (internal standard, IS) on the cartridges packed hyper cross-linked polystyrene which maintain some tens extractions without losses of efficiency. Carboxylic acids are derivative with 1-(bromoacetyl)pyrene in acetone at presence of triethylamine. Chromatographic separation of derivatives is performed on Chromolith Perfonnance RP-18e columns, which packed unique monolithic sorbent. UV detection at 360 nm. Mobile phase acetonitrile - water (90:10, v/v) plus 1% isopropanol, speed flow 2000 microL/min, pressure 21 bar. Complete chromatographic cycle less than 3 minutes. Yield of IS and valproic acid (extraction plus derivatization) was 101-106%. Sensitivity (limit detection) was near 1 ng for valproic and near 0.6 ng for heptanoic acid during signal/noise ratio = 3.

Enantioanalysis of Pipecolic Acid with Stochastic and Potentiometric Microsensors

Stochastic and potentiometric microsensors based on porphyrins and polymeric surfactants such as polysodium N-undecanoyl-L-leucylvanilate and polysodium N-undecanoyl-L-vanilate were developed for enantioselective assay of pipecolic acid. The matrices used for the design of the stochastic sensors were diamond paste and graphite paste, while the matrix used for the design of potentiometric sensors was carbon paste. The response characteristics of the microsensors were determined for the enantiomers of pipecolic acid. The response characteristics, selectivity, and enantioselectivity studies proved that the proposed microsensors can be used for clinical enantioanalysis of pipecolic acid in biological fluids, e.g., urine and whole blood.

Distribution of serotonin, 5-hydroxyindolacetic acid and homovanillic acid in biological fluids of psycotic patients treated with clozapine

Distribution of serotonin, 5-hydroxyindolacetic acid and homovanillic acid in biological fluids of psycotic patients treated with clozapine

Chromogenic System for Measuring Hydrogen Peroxide: The Enzymatic Uric Acid Assay

Featured Article: Fossati P, Prencipe L, Berti G. Use of 3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone chromogenic system in direct enzymic assay of uric acid in serum and urine. Clin Chem 1980;26:227–31.1 Our 1980 report in Clinical Chemistry described an improved chromogenic detection system that, coupled with the enzyme oxidation of uric acid, led to a direct method for assaying uric acid in biological fluids. The system assay was reliable, simple, rapid, and suitable for either manual or automated procedures. The work was developed in the context of the Sera-Pak line of clinical chemistry reagents at Miles Italiana SpA’s Ames research and development laboratories. This line of reagents was marketed in 58 countries throughout the world. Before our investigation, chemical and enzymatic methods for uric acid assay had been described, but these assays had practical disadvantages: lack of direct assay in a small sample with a single reagent, need for a serum blank, long incubation times, and false negatives …

Determination of hippuric acid in biological fluids using single drop liquid–liquid-liquid microextraction

A simple, sensitive, and inexpensive single drop liquid–liquid-liquid microextraction (LLLME) followed by isocratic reverse phase high performance liquid chromatography (RP-HPLC) and UV detection was developed for determination of hippuric acid in human urine and serum samples. The analyte was extracted from an acidic aqueous sample solution (pH 3) through a thin layer of organic solvent membrane and back-extracted to a basic acceptor drop (pH 11) suspended on the tip of a 10-μL HPLC syringe in the organic layer. The influence of several important parameters on extraction efficiency of hippuric acid was evaluated. Under optimized experimental conditions, the calibration graph was linear in the concentration range of 1–400 μg L−1 with coefficient of determination 0.998. The limits of detection and quantification were 0.3 and 1.0 μg L−1, respectively. Intra-day and inter-day precision were in the range of 1.1–2.7% and 1.1–3.1%, respectively. This procedure was successfully applied to the determination of hippuric acid in spiked urine and serum samples with satisfactory results. The relative recoveries of urine and serum samples ranged from 91.4 to 99.3%, with relative standard deviations varying from 1.6 to 4.2%.

Novel poly(3-methylthiophene)/Pd, Pt nanoparticle sensor: Synthesis, characterization and its application to the simultaneous analysis of dopamine and ascorbic acid in biological fluids

Abstract A promising modified electrode was fabricated by distributing Pt or Pd nanoparticles into conductive polymer matrix of poly(3-methylthiophene) (PMT). Electrochemical investigation of the resulting films was achieved using cyclic voltammetry and differential pulse voltammetry. Several factors affecting the electrocatalytic activity of the hybrid material were studied. Some are related to the polymer such as film thickness, method of its formation and dedoping the polymer film before loading metal particles, other factors are related to the metal particles such as type of metal deposited, method of its deposition, its amount and deposition voltage. EDX analysis was employed to confirm the loading of metal particles to the polymer film. The results suggest that the hybrid film modified electrode combining the advantages of PMT and metal nanoparticles exhibits dramatic electrocatalytic effect on the oxidation of dopamine (DA) and results in a marked enhancement of the current response. The proposed method was applied to the simultaneous determination of ascorbic acid (AA) and dopamine (DA) in physiological pH 7.4 PBS. It was observed that in the presence of AA at millimolar level (0.1 mM), the Pd nanoparticle-modified PMT electrode can sense the increase of DA at micromolar concentration (0.05–1 μM) which is typical of the physiological conditions. The interference study shows that the modified electrode exhibits excellent selectivity in the presence of AA and uric acid (UA) and glucose. It has been shown that this modified electrode can be used as a sensor with high reproducibility, sensitivity, and stability. The method was applied to urine and healthy human blood serum samples and excellent results were obtained.

Déficit de succínico semialdehído deshidrogenasa. Disminución de los niveles de 4 OH butírico con dosis bajas de vigabatrina

Succinic semialdehyde dehydrogenase deficiency (gamma-hydroxybutyric aciduria) is a rare neurometabolic disease caused by a deficiency in gamma-aminobutyric degradation, resulting in an increase in gamma-hydroxybutyric acid in biological fluids. The clinical spectrum is heterogeneous, including a variety of neurological manifestations and psychiatric symptoms. The treatment usually used is vigabatrin, but its clinical efficacy is under discussion. We present two affected siblings. The older brother was examined when he was 2.5 years old due to psychomotor and developmental delay, disturbances in motor coordination, axial hypotonia and language disability. His younger brother had mild axial hypotonia when 5 months old. Metabolic studies demonstrated a high plasma and urine concentration of gamma-hydroxybutyric acid. Mutation analysis of the gene ALDH5A1 confirmed the disease. After 1 year of treatment with low-doses of vigabatrin of the older patient, a decrease in gamma-hydroxybutyric acid plasma levels and a slow clinical improvement were observed.

Chemical Redox Modulation of the Surface Chemistry of CdTe Quantum Dots for Probing Ascorbic Acid in Biological Fluids

Most of the fluorescence resonance energy transfer (FRET)-based sensors employing quantum dots (QDs) usually use organic fluorophores and gold nanoparticles as the quenchers. However, complex processes for the modification/immobilization of the QDs are always necessary, as the generation of FRET requires strict distance between the donor and acceptor. Herein, a simple chemical redox strategy for modulating the surface chemistry of the QDs to develop a QD-based turn-on fluorescent probe is reported. The principle of the strategy is demonstrated by employing CdTe QDs with KMnO(4) as the quencher and ascorbic acid as the target analyte. The fluorescence of CdTe QDs is quenched with a blue-shift upon addition of KMnO(4) due to the oxidation of the Te atoms on the surface of the QDs. The quenched fluorescence of the QDs is then recovered upon addition of ascorbic acid due to the reduction of CdTeO(3)/TeO(2) on the surface of the QDs to CdTe. The recovered fluorescence of the QDs increases linearly with the concentration of ascorbic acid from 0.3 to 10 microM. Thus, a novel QD-based turn-on fluorescent probe with a detection limit as low as 74 nM is developed for the sensitive and selective detection of ascorbic acid in biological fluids. The present approach avoids the complex modification/immobilization of the QDs involved in FRET-based sensors, and opens a simple pathway to developing cost-effective, sensitive, and selective QD-based fluorescence turn-on sensors/probes for biologically significant antioxidants.

A simple method for hyaluronic acid quantification in culture broth

The carbazole assay has been used for determination of the percentage of hyaluronic acid in biological fluids. However, it is difficult to measure the concentration of hyaluronic acid in culture broth because glucose and polysaccharides remaining after cultures can react with sulfuric acid and carbazole. The glucose and polysaccharide remnants must be completely removed in order to get the correct value for hyaluronic acid. The turbidity assay, another method for estimating the concentration of hyaluronic acid, is based on the formation of insoluble complexes between hyaluronic acid and cetyltrimethylammonium bromide. This method is very easy and fast compared with the carbazole assay. Because concentrations of hyaluronic acid measured by the turbidity assay were ranged around 100% of those measured by the carbazole assay, the content of hyaluronic acid in culture broth can be determined by the turbidity assay. The turbidity method also has the advantage of being safer than the carbazole assay.

Conventional and planar chip sensors for potentiometric assay of uric acid in biological fluids using flow injection analysis

The potentiometric response properties of several PVC-based membrane sensors using phthalocyanine complexes of cobalt(II) (CoPC) and Fe(II) (FePC) as anion carriers, towards uric acid were constructed and characterized. The sensors demonstrated fast near-Nernstian response for uric acid over the concentration ranges 9.1 × 10 −6 to 9.1 × 10 −2 and 3.1 × 10 −5 to 3.1 × 10 −2 M with detection limits 0.67 and 2.85 μg mL −1 over pH 6.5–8 for CoPC and FePC based membrane sensors plasticized with o-NPOE and 1% TDMAC, respectively. A novel solid-state planar chip urate sensor was developed, characterized according to IUPAC recommendations, easily used in a single channel wall-jet flow injection system and compared with a tubular detector. The intrinsic characteristics of the detectors in a low dispersion manifold were determined and compared with data obtained under hydrodynamic mode of operation. Validation of the assay methods with the proposed sensors by measuring the lower limit, range, accuracy, precision, repeatability and between-day-variability revealed good performance characteristics confirming applicability for continuous determination of uric acid. The sensors were used for determining urate in biological fluids at an input rate of 50 samples per hour. The results compare favorably with data obtained by the standard spectrophotometry.

Direct determination of valproic acid in biological fluids by capillary electrophoresis with contactless conductivity detection

Capacitively coupled contactless conductivity detection (C 4D) is a new technique providing high sensitivity in capillary electrophoresis (CE) especially for small ions that can otherwise only be determined with indirect methods. In this work, direct determination and validation of valproic acid (VPA) in biological fluids was achieved using CE with C 4D. VPA is of pharmacological interest because of its use in epilepsy and bipolar disorder. The running electrolyte solution used consisted of 10 mM 2-( N-morpholino)ethane sulfonic acid (MES)/ dl-histidine (His) and 50 μM hexadecyltrimethylammonium bromide (HTAB) at pH 6.0. Caproic acid (CA) was selected as internal standard (IS). Analyses of VPA in serum, plasma and urine samples were performed in less than 3 min. The interference of the sample matrix was reduced by deproteinization of the sample with acetonitrile (ACN). The effect of the solvent type and ratio on interference was investigated. The limits of detection (LOD) and quantitation (LOQ) of VPA in plasma samples were determined as 24 and 80 ng/ml, respectively. The method is linear between the 2 and 150 μg/ml, covering well the therapeutic range of VPA (50–100 μg/ml).

A ratiometric and non-enzymatic luminescence assay for uric acid: differential quenching of lanthanide excited states by anti-oxidants

The excited states of Tb and Eu complexes of a common macrocyclic ligand are quenched preferentially by electron transfer from the urate anion, allowing the creation of a new assay to measure uric acid in biological fluids.

Multicommuted optosensor for the determination of pipemidic acid in biological fluids

Multicommuted optosensor for the determination of pipemidic acid in biological fluids

An Inexpensive Biosensor for Uric Acid Determination in Human Serum by Flow-Injection Analysis

An inexpensive and easy to construct miniaturized biosensor is described for the determination of uric acid in biological fluids. The amperometric biosensor was prepared by using a carbon paste electrode prepared with uricase from Arthrobacter globiforms and tetracyanoquinodimethane as electron transfer mediator. When incorporated into a flow-injection system it was enabled to perform 50 measurements/h of uric acid in the analytical range of 1–100 μmol dm−3 with a relative standard deviation of 0.20% (n=14). The system was applied to human serum samples analysis providing good data correlation with those obtained by the reference spectrophotometric method. A linear relationship AM (μmol dm−3)=1.02 (±0.05) SP (μmol dm−3) −0.12 (±0.13) was obtained evidencing the absence of significant error. The constructed biosensor was successfully used for at least four months (250 assays) with only a 13% of decrease in the enzymatic activity.

Biological microsystem for measuring uric acid in biological fluids

This paper describes a biological microsystem (bio-system) for measuring uric acid concentration in serum, plasma or urine. Its operation is based on optical absorption in a well-defined part of the visible spectrum. The bio-system is composed by two dies: one is fabricated in polystyrene and contains the microchannels and the other is fabricated in a CMOS standard process and contains the photodetector and readout electronics. The uric acid concentration is measured by using a mixture of 14 l of infinity TM uric acid reagent with 0.25 lo f sample. The achieved sensitivity is 0.33 mg/dl (±0.6% of the value in urine of a healthy person), with a 1 mm lightpath. Using an optical absorption method, a maximum peak at wavelength λ = 494 nm, is detected. This bio-system can be included in the group of low-cost disposable devices for biological fluids analysis. © 2003 Elsevier B.V. All rights reserved.