Determination of interferon-gamma in Chinese hamster ovary cell culture supernatant by coupled-column liquid chromatography

A robust tandem HPLC method coupling size-exclusion (Shodex Asahipak GS-320HQ) and reversed phase (Vydac 218TP54) columns with ultraviolet detection was developed for quantitative determination of interferon-gamma (IFN-gamma) in Chinese hamster ovary cell culture supernatant. The 2D-HPLC system was linked up by a 6-port 2-position low hold-up volume switch valve. Compared to a commercial ELISA kit for IFN-gamma, the coupled column LC approach was able to detect and quantify soluble IFN-gamma, regardless of the glycoprotein's molecular/conformational variability and sample background. Each LC-LC analysis took 90 minutes inclusive of column regeneration. The relative standard deviation of measurements (n = 5) was less than 3%. The limit of detection (LOD) was determined to be 0.35 microg IFN-gamma.     

Infrared spectroscopy of racemic and enantiomeric forms of atenolol

The molecular structure of conformational isomorphs given by X-ray diffraction for racemic and enantiomeric atenolol were optimized at the HF/6-31G* level of theory and the infrared spectra of the structure were calculated. These spectra are used to characterize the differences between the various atenolol conformers. The spectra of the (R,S)- and S-atenolol solid forms were recorded and the bands corresponding to the functional groups identified with the aid of the calculated spectra, fitting analysis, temperature effect and H/D isotopic exchange. Particular attention was paid to the stretch vibration modes of the functional groups present in the atenolol.     

Factorial analysis of a chemiluminescence system for bromate detection in water

A chemiluminescent flow system for bromate detection, based on the reaction of bromate with sulphite in acid medium and using the steroid hydrocortisone as sensitiser, was studied. A factorial analysis strategy for the study of the effect on the system response of the experimental factors, flow rates of two pumps (Q₁ — acid sulphite plus hydrocortisone aqueous solution; Q₂ — carrier, water), sample injection volume (V_L), reactor volume (V_R), sulphite concentration (C_S), hydrocortisone concentration (C_H) and acid concentration (C_A), was used. Screening analysis of the system performance was made using Plackett Burman designs. The system optimisation procedure was achieved by three levels three factors full factorial designs. V_L and C_H are the most significant factors — a quadratic C_H term was also observed to be significant. The optimised system responded linearly (logarithm of the detector signal as function of the logarithm of the bromate concentration) in the concentration range between 3.6×10⁻⁷ and 5.0×10⁻⁴ M with a limit of detection of about 8.0×10⁻⁸ M (about 10 microg/l). An analysis of some interfering ions was made and it was suggested that bromide and chloride begin to quench chemiluminescence when they are in a 10-fold excess relatively to bromate concentration.     

Hybrid system of nickel<Emphasis Type="Bold">–</Emphasis>cobalt hydroxide on carbonised natural cellulose materials for supercapacitors

Advanced carbon materials formed from abundant biomass are an exciting and promising class for energy devices due to the clear advantages of low cost, sustainability and good physical and electrochemical properties. However, these materials typically do not compete well with their metal functionalised counterparts. In this work, we demonstrate that xCo(OH)₂–(1?x)Ni(OH)₂ with various Ni:Co ratios can be deposited onto biomass-derived carbon to make a hybrid inorganic-carbon electrode with tuneable physical features and electrochemical performance. These features were tuned by adjusting the Ni:Co ratio within precursor solutions. The electrodes had shown a capacitance ranging from 780.7 to 2041 F g^?1, which is very close to the theoretical value for Ni(OH)₂ (2365 F g^?1). A hypothesis is presented to help explain this performance for a modified, biomass-derived carbon electrode.     

Voltammetric determination of 17β-estradiol in human urine and buttermilk samples using a simple copper(II) oxide-modified carbon paste electrode

This paper reports the voltammetric determination of 17β-estradiol in urine and buttermilk samples using a simple detector based on a carbon paste electrode (CPE) modified with copper(II) oxide (CuO). The CuO was obtained by the Pechini method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive (EDS), Fourier transform infrared (FTIR), and Raman spectroscopies. Cyclic voltammetry (CV) and square-wave voltammetry (SWV) demonstrated that the CuO-modified carbon paste electrode (CuO/CPE detector) displayed much higher electrocatalytic activity in the 17β-estradiol oxidation reaction than the CPE without modification, exhibiting a low detection limit of 21.0 nmol L^?1 with a wide linear range from 60.0 to 800.0 nmol L^?1 (R = 0.998). Satisfactory results were obtained for the determination of 17β-estradiol in human urine and buttermilk samples. The proposed electrochemical detector offers high repeatability, stability, fast response, low cost, and potential for practical application in the quantification of this hormone.

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Self-assembled films based on polypyrrole and carbon nanotubes composites for the determination of Diuron pesticide

In this work, polypyrrole (PPy) and its respective composite with functionalized multi-walled carbon nanotubes (MWCNT) were obtained by chemical polymerization of the monomer pyrrole in aqueous solution. The obtained PPy as well as its composite (PPy-MWCNT) were characterized by Fourier transform infrared spectroscopy (FTIR) and were used to produce nanostructured self-assembled (SA) films deposited onto glass substrates covered with indium tin oxide (ITO). The SA films were produced with alternated layers of polystyrene sulphonated (PSS) and were characterized by UV-visible, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) analyses. The applicability of the SA films was evaluated by square wave voltammetry (SWV) with standard additions of aliquots of Diuron pesticide in Britton-Robinson buffer solutions (pH = 2.0). The results showed an oxidation peak at 0.23 V which increases in function of the Diuron concentration for both the SA films. It was also observed that the SA film based on the composite (PPy-MWCNT/PSS) showed a peak current intensity about ten times higher in comparison with its unmodified counterpart (PPy/PSS) for a Diuron concentration of 4.29 × 10^?5 mol L^?1, indicating a synergic effect between PPy and MWCNT in the composite. The limits of quantification (LOQ) and limits of detection (LOD) were respectively 8.6 × 10^?7 mol L^?1 and 2.6 × 10^?7 mol L^?1.     

Selective binding of the cyano group in acrylonitrile adsorption on Si(100)-2 x 1

The covalent binding of acrylonitrile (CH(2)=CH-C triple bond N) and the formation of a C=C-C=N structure on Si(100) have been investigated using high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and density functional theory (DFT) calculations. For chemisorbed acrylonitrile, the absence of nu(C triple bond N) at 2245 cm(-1) and the appearance of nu(C=N) at 1669 cm(-1) demonstrate that the cyano group directly participates in the interaction with Si(100), which is further supported by XPS and UPS observations. Our experimental results and DFT calculations unambiguously demonstrate a [2 + 2] cycloaddition mechanism for acrylonitrile chemisorption on Si(100) through the binding of C triple bond N to Si dimers. The resulting chemisorbed monolayer with a C=C-C=N skeleton can serve as a precursor for further chemical syntheses of multilayer organic thin films in a vacuum and surface functionalization for in situ device fabrication.