Sulfur-Doped Graphene-Based Electrochemical Sensors for Fast and Sensitive Determination of (R)-(+)-Limonene from Beverages.

Two sensors based on sulfur-doped graphene, a gold nanoparticle paste modified with 5,10,15,20-tetraphenyl-21H,23H-porphine and 5,10,15,20-tetrakis (pentafluorophenyl chloride)-21H,23H-iron (III) porphyrin, were proposed for the determination of R-limonene in beverages (triple sec liqueur and limoncello). Differential pulse voltammetry was the method used to characterize and validate the proposed sensors. The response characteristics showed that the detection limits for both sensors were 3 × 10 mol L, while the quantification limits were 1 × 10 mol L.

Nanographene-based electrochemical sensors for ultrasensitive determination of sorbic acid from food.

Ultrasensitive determination of sorbic acid in food is essential for the assessment of the food quality. Therefore, two sensors based on nanographene decorated with gold nanoparticle paste modified with metal porphyrins (Zn protoporphyrin IX, and 2,3,7,8,12,13,17,18 octaethyl, 21H, 23H-porphirine Mn(III) chloride) were proposed for the determination of sorbic acid in food (bakery products and mayonnaise). Square-wave voltammetry was used for the characterization and validation of the proposed sensors.

Disposable stochastic sensors for fast analysis of ibuprofen, ketoprofen, and flurbiprofen in their topical pharmaceutical formulations.

Three disposable stochastic sensors based on maltodextrin (dextrose equivalent = 4-7) and nanostructures (copper monolayer, carbon monolayer and carbon-copper composite layer) deposited using cold plasma on copy paper were proposed for the fast analysis of ibuprofen, ketoprofen and flurbiprofen in pharmaceutical formulation samples. The widest linear concentration ranges recorded were: for ibuprofen 1 fmol/L - 1 mmol/L when the disposable stochastic sensor based on carbon monolayer was used, for ketoprofen 1 fmol/L - 1 mmol/L when the disposable stochastic sensors based on copper monolayer and carbon-copper composite layer were used, and for flurbiprofen 1 fmol/L - 10 mmol/L when the disposable stochastic sensor based on carbon-copper composite layer was used. The lowest limit of detection recorded for each non-steroidal anti-inflammatory drug was 1 fmol/L.

Fast screening test for molecular recognition of levodopa and dopamine in biological samples using 3D printed stochastic microsensors.

The simultaneous assay of levodopa and dopamine is essential for diagnosis and treatment of neurodegenerative diseases and brain cancer. 3D stochastic microsensors based on multi-walled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs) and 1-adamantyloleamide (AOA) was used for the simultaneous molecular recognition of levodopa and dopamine in biological samples (whole blood, urine, and brain tissue). The proposed 3D stochastic microsensors presented low limits of quantification, and high sensitivities.

Myoglobin-silver reduced graphene oxide nanocomposite stochastic biosensor for the determination of luteinizing hormone and follicle-stimulating hormone from saliva samples.

A silver reduced graphene oxide (Ag-rGO) nanocomposite paste was prepared for the assay of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in children's saliva. The paste was modified with a solution of myoglobin (Myb) to form the stochastic biosensor, to improve the sensitivity of the method. The Ag-rGO powder and Myb-Ag-rGO paste were morphologically and structurally characterized by SEM, TEM and XRD measurements.

Advances in immunosensors for clinical applications.

Immunoassay technique performs a fast, simple, reliable, and sensitive analysis of different compounds, being applied in several areas of interest such as clinical analysis for medical diagnosis, as well as in environmental analysis, and food quality control. The latest research activities in this field are represented by the attempts to achieve a low limit of detection by developing of new signal amplification strategies, eliminate the interferences, and decrease the cost of analysis.

Molecular Recognition of Nitrites and Nitrates in Water Samples Using Graphene-Based Stochastic Microsensors.

Two stochastic microsensors based on graphene powders and protoporphyrin IX were proposed for the simultaneous assay of nitrite and nitrate in water samples. The proposed microsensors can provide a fast screening of water samples with a qualitative and quantitative analysis for NO and NO at very low concentration levels. The linear concentration ranges were wide, covering clean as well as polluted waters.

Fast Screening of Whole Blood Samples and Pharmaceutical Compounds for Enantiorecognition of Free L-T3 , L-T4 , and D-T4.

A fast screening method of whole blood was proposed for enantiorecognition of free L-T3 , L-T4 , and D-T4 . Stochastic microsensors based on four inulins (IN, IQ, TEX, and HD) immobilized on diamond paste (DP) were used for recognition of free L-T3 , L-T4 , and D-T4 . For the enantiorecognition of free L-T4 and D-T4 in whole blood and pharmaceutical samples, the best microsensor was the one based on TEX/DP (wide linear concentration ranges, and low limits of quantification).

Pattern recognition of neurotransmitters using multimode sensing.

Background: Pattern recognition is essential in chemical analysis of biological fluids. Reliable and sensitive methods for neurotransmitters analysis are needed.

New Method: Therefore, we developed for pattern recognition of neurotransmitters: dopamine, epinephrine, norepinephrine a method based on multimode sensing.

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.

Amperometric biosensor based on diamond paste for the enantioanalysis of L-lysine.

An amperometric biosensor was proposed for the enantioanalysis of L-lysine. The biosensor is based on the impregnation of L-lysine oxidase in diamond paste. The potential used for the determination of l-lysine was 650 mV.

Determination of L- and D-fucose using amperometric electrodes based on diamond paste.

Monocrystalline diamond (natural diamond, synthetic-1 and synthetic-2) based electrochemical electrodes were designed for the analysis of L- and D-fucose. Response characteristics of the electrochemical electrodes were determined using cyclic voltammetry and differential pulse voltammetry (DPV). L-fucose was determined using DPV with electrodes based on natural diamond, synthetic-1 and synthetic-2, respectively, at 240 mV using NaCl as the electrolyte (pH 3.

Carbon and diamond paste microelectrodes based on Mn(III) porphyrins for the determination of dopamine.

Three Mn(III) porphyrins were used for the design of carbon paste and diamond paste based microelectrodes, which were employed for the determination of dopamine in pharmaceutical and biological samples using differential pulse voltammetry (DPV). The limits of detection lie between 1.6 x 10(-13) and 2.

Simultaneous determination of L- and D-T4 using a sequential injection analysis/sensors system.

A sequential injection analysis system was selected for the simultaneous determination of L- and D-T4 in raw material and pharmaceutical products, because of the highest precision and accuracy, the lower consumption of sample and buffer, and the flexibility of selecting different buffers accordingly with the type of sensors utilized as detectors. An amperometric biosensor based on D-amino acid oxidase was used as detector for D-T4 and an immunosensor based on anti-L-T4 was used as detector for L-T4. The SIA/biosensors system can be used reliably on-line in synthesis process control, for the simultaneous assay of L- and D- T4 with a frequency of more than 30 samples per hour.

Enantioanalysis of (-)butaclamol using vancomycin and teicoplanin as chiral selectors.

Butaclamol is an antipsychotic drug used in the treatment of schizophrenia. The macrocyclic antibiotics, vancomycin and teicoplanin, are proposed as chiral selectors for the design of the enantioselective, potentiometric membrane electrodes (EPMEs) for the assay of (-)butaclamol. The slopes of the electrodes are near-Nernstian for the assay of (-) butaclamol with linear concentration ranges between 10(-10) and 10(-7) mol/L and between 10(-9) and 10(-7) mol/L for vancomycin and teicoplanin based EPMEs.

Enantioanalysis of l-2-hydroxyglutaric acid in urine samples using enantioselective, potentiometric membrane electrodes based on maltodextrins.

Quantitative assay of l-2-hydroxyglutaric acid (l-2-HGA) is important for the diagnosis of l-2-hydroxyglutaric aciduria. Three enantioselective, potentiometric membrane electrodes (EPMEs) based on maltodextrins with different dextrose equivalent (DE) (DE: 4.0-7.

Immunosensor for the determination of azidothymidine: its utilization as detector in a sequential injection analysis system.

An amperometric immunosensor based on graphite paste (graphite powder and paraffin oil) has been constructed for the assay of azidothymidine (AZT). The graphite paste is impregnated with anti-AZT. The immunosensor can be reliably used for the assay of AZT in its pharmaceutical formulation.

Determination of (+)-3,3',5,5'-Tetraiodo-L-thyronine (L-T4) in Serum and pharmaceutical formulations using a sequential injection analysis/immunosensor system.

A sequential injection analysis/immunosensor system is proposed for the analysis of thyroxine (L-T4) in serum and in pharmaceutical formulations with a rate of 75 samples/hour. The immunosensor design is based on the physical immobilization of anti-L-T4 in carbon paste. The working concentration range of the immunosensor in the sequential injection analysis system is between 36 and 1080 ng/mL with a limit of detection of 24.

Determination of (+)-3,3',5-triiodo-L-thyronine (L-T3) from serum using a sequential injection analysis/immunosensor system.

A sequential injection analysis/immunosensor system is proposed for the analysis of T3 in serum with a rate of 75 samples/hr. The immunosensor design is based on the physical immobilization of anti-T3 in carbon paste. The working concentration range of the immunosensor in a sequential injection analysis system is between 3.

Simultaneous determination of L- and D-methotrexate using a sequential injection analysis/amperometric biosensors system.

A sequential injection analysis (SIA) is proposed for the simultaneous determination of L- and D-methotrexate (Mtx) using amperometric biosensors as detectors. A SIA system is proposed due to the highest precision and accuracy and lower consumption of sample and buffer. The amperometric biosensors used as detectors in SIA system were based on L-amino acid oxidase (L-AAOD) or/and L-glutamate oxidase (L-Glox) and horseradish peroxidase (HRP) for the assay of L-Mtx and D-amino acid oxidase (D-AAOD) and HRP for the assay of D-Mtx were selected.

Diamond paste-based electrodes for determination of Cr(III) in pharmaceutical compounds.

A new class of monocrystalline diamond paste-based electrodes is proposed for the determination of chromium(III) at trace levels in vitamins. Three types of monocrystalline diamond-natural diamond 1mu (natural diamond), synthetic diamond 50mu (synthetic-1), and synthetic diamond 1mu (synthetic-2)-were used for electrode construction. The linear concentration ranges are between 10(-10) and 10(-8); 10(-9) and 10(-7), and 10(-10) to 10(-8) mol L(-1), with limits of detection of 10(-12), 10(-12), and 10(-11) mol L(-1), when natural diamond, synthetic-1, and synthetic-2, respectively, are used as electrode materials.