l -Glutamate biosensor for estimation of the taste of tomato specimens

An amperometric biosensor has been developed for measurement of Umami, or the taste based on the amount of l-glutamate, in tomato foods. The biosensor is based on an enzyme-mediator system in which l-glutamate oxidase is used for biochemical oxidation of l-glutamate and a tetrafulvalene-tetracyanoquinodimethane (TTF-TCNQ) paste, prepared from the mixture of TTF-TCNQ salt, graphite powder, and silicone oil, serves as the mediator. The limit of detection, calculated by use of a four-parameter logistic model, was 0.05mmol L−1, and the limit of quantification was 0.15mmol L−1. The correlation coefficient (R 2) was 0.990 and the relative standard deviation was no more than 1% (n=5). The response time (τ 95) was 20-50s, depending on concentration. The repeatability of the sensor was better than 5% (n=10). The sensor developed was stable for more than ten day

Application of Room Temperature Ionic Liquids to the Development of Electrochemical Lipase Biosensing Systems for Water-Insoluble Analytes

Biosensors have been prepared by modification of glassy carbon electrodes with functionalised multiwalled carbon nanotubes (MWCNT) dispersed in the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethane)sulfonimide (BmimNTF2) and with lipase cross-linked with glutaraldehyde. The biosensor was applied to the determination of olive oil triglycerides by cyclic voltammetry. A phosphate buffer (pH 7.0) / BmimNO3 mixture is a better electrolyte than aqueous buffer alone. The response signal in the buffer-BmimNO3 mixture was found to increase with the number of cycles until a constant current was achieved. The calibration curve obtained exhibited a sigmoid-shape and a fourparameter model was used to fit the data which gave a limit of detection of 0.11 μg mL−1. Close inspection of such calibration curves showed two distinct linear regions indicating changes in the mechanism of the electrochemical response. Overall, the oxidative analytical response was found to be due to phenolic compounds present in the olive oil, released in the presence of lipase, rather than due to triglycerides per se. It was also found that there were no interferences from either cholesterol or glycerol. A possible mechanism of olive oil determination at a MWCNT-BmimNTF2/Lip biosensor is proposed

Development of electrochemical oxidase biosensors based on carbon nanotube-modified carbon film electrodes for glucose and ethanol

Functionalised multi-walled carbon nanotubes (MWCNTs) were cast on glassy carbon (GC) and carbon film electrodes (CFE), and were characterised electrochemically and applied in a glucose-oxidase-based biosensor. MWCNT-modified carbon film electrodes were then used to develop an alcohol oxidase (AlcOx) biosensor, in which AlcOx-BSA was cross-linked with glutaraldehyde and attached by drop-coating. The experimental conditions, applied potential and pH, for ethanol monitoring were optimised, and ethanol was determined amperometrically at -0.3 V vs. SCE at pH 7.5. Electrocatalytic effects of MWCNT were observed with respect to unmodified carbon film electrodes. The sensitivity obtained was 20 times higher at carbon film/MWCNT-based biosensors than without MWCNT.http://www.sciencedirect.com/science/article/B6TG0-4RPM7TX-1/1/c7c201831d528c29b469d52592bc656

Being Female: a handicap for researchers in the competion for NCCR.

The Swiss National Science Foundation made a call for National Centers fo Competence in Research (NCCR) for the first time in 1999 and 2004. Together, these announcements concerned all disciplines and led to 126 preproposals, which were put forward by 2134 men and women researchers. It can be assumed that this operation mobilised Swiss researchers who regarded themselves as particularly well qualified to conduct high-level research in their field. The article uses network analysis and regression analysis methods to examine to what extend women had a lower success rate than men in the two selection rounds because of their sex. On the whole, the findings attest the gender neutrality of the National Science Foundation's selection procedures. However, they also confirm the well-known fact that women scientists are less represented in the higher echelons of academia and concentrated in the social sciences and humanities, as well as showing that this concentration reduces women's chances of success in scientific competition. The article shows that unequal gender-specific success rates prior to the NCCR funding contest play a fairly significant role

Spectrometric and electrochemical investigation of vanadium(V) and vanadium(IV) tartrate complexes in solution

Spectroscopic and electrochemical studies were carried out to characterize the vanadium(IV) and (V) complexes that form in solution and their interconversions. 51V NMR spectroscopy coupled with ¹H NMR, 13C NMR and EPR spectroscopy were used to characterize the vanadium(V)-tartrate complexes that form in the vanadium-tartrate system. The major complex that forms over most of the pH range is a 1:1 complex. In addition a minor 1:2 complex forms. The 1:2 complex formed from enantiomerically pure tartaric acid was less stable than complex formed from racemic tartaric acid. These complexes are different than the 2:2 complex that is the major contributor in the vanadium(IV)-tartrate system. The polarographic and cyclic voltammetic investigations of the electrochemical behavior of V(V) in the presence of tartrate demonstrated a complex formation. The diffusion coefficient values of free vanadium ions and vanadium-tartrate complexes were determined. The minimum average values for the diffusion coefficient for the vanadium(IV)-tartrate 2:2 complexes were determined to range from 3 <FONT FACE=Symbol>&acute;</FONT> 10-6 cm² s-1 to 17 <FONT FACE=Symbol>&acute;</FONT> 10-6 cm² s-1 depending on pH

A Sensor for Electrochemical pH Monitoring Based on Laser-Induced Graphene Modified with Polyfolate

A laser-induced graphene (LIG) modified with chitosan (Chit) and conducting polymer polyfolate (PFA) was used as a base to develop a flat and flexible pH sensor. LIGs were formed using two different irradiation wavelengths of 355 nm and 532 nm. Depending on the wavelengths, the obtained electrodes were named LIG355 and LIG532. Microscopic imaging revealed that the bare LIG electrode surface had rough structures after laser treatment giving hydrophilic properties, and that PFA forms fibre-like structures on Chit coated LIG. Electrochemical investigation with the redox probe demonstrated that diffusion is a limiting process at the bare and modified LIG electrodes. A capacitive behaviour was observed from electrochemical impedance spectra at bare electrodes, showing a rather rough interface at LIG355 but a microporous one at LIG532. The developed flat and flexible electrode was sensitive to pH in the region from 6.0 to 9.0. In the studied pH range, the sensitivity was 27.86 ± 0.81 for PFA/Chit/LIG355 and 30.32 ± 0.50 mV/pH for PFA/Chit/LIG532 with moderate stability for a period of more than two months

Screen-printed carbon electrodes bulk-modified with Bi2O3 OR Sb2O3 for trace determination of some heavy metals

Screen-printed carbon electrodes (SPCE) bulk-modified with Bi.2O3 or Sb2O3 have been investigated for their suitability to determinate some selected heavy metals using anodic stripping voltammetry. At a SPCE modified with 1.25% (w/w) Bi2O3, the corresponding re-oxidation peak potentials appeared at -0.785 V for Cd, or at -0.565 V for Pb. At a SPCE modified with 1.00% (w/w) Sb2O3, the reoxidation peak of Cd appeared at -0.805 V. Bulk-modified Bi2O3 -SPCEs, after an electrochemical preconditioning, can be used for monitoring Cd and Pb at concentrations with a preconcentration time of 600 s at -1.2 V vs.SCE. An analogous Sb2O3 -SCPE displays a higher quantification limit for Cd at the same conditions, whereas the determination of Pb seemed impossible by simple procedures. The SPCE modified with Bi2O3 was applied for determination of Pb(II) in drinking water and urine