Determination of α-Cypermethrin from Soil by Using HPTLC

JPC – Journal of Planar Chromatography – Modern TLC - α-Cypermethrin is a synthetic pyrethroid insecticide used to control insects. In soil, α-cypermethrin biodegrades...     

Modification of glassy carbon electrode by the electrochemical oxidation of 3‐aminophenylcalix[4]pyrrole in nonaqueous media

3‐Aminophenylcalix[4]pyrrole (3APCP) was grafted to a glassy carbon (GC) surface during the electrochemical oxidation process in 0.1 M tetrabutylammoniumtetra‐fluoroborate (TBATFB) containing acetonitrile solution. The presence of a surface film was confirmed electrochemically by comparing voltammograms of dopamine and ferricyanide redox probes at the bare and modified electrodes. Reflection‐absorption infrared spectroscopy (RAIRS), XPS, atomic force microscopy (AFM), ellipsometry and the contact angle measurements were also employed to characterize 3APCP film on GC electrode. RAIRS analysis revealed that calix[4]pyrrole was bonded to the glassy carbon surface via the etheric linkage. The stability of the modified GC electrode was also studied. Copyright © 2011 John Wiley & Sons, Ltd.     

On the stability of nonlocal difference schemes in subspaces

We consider finite-difference schemes for the heat equation with nonlocal boundary conditions. The original problem, as well as the approximating finite-difference schemes, is not stable under perturbations of the initial data. For such problems, we introduce the definition of stability of a finite-difference scheme in a subspace and derive estimates in terms of Hilbert norms expressing the stability with respect to the initial data in subspaces spanned by eigenvectors of the main difference operator.     

Simultaneous Determination of Benzodiazepines and Ketamine from Alcoholic and Nonalcoholic Beverages by GC-MS in Drug Facilitated Crimes

A GC-MS method with HP-5MS capillary column was developed for the simultaneous determination of underivatized flunitrazepam, clonazepam, alprazolam, diazepam and ketamine from drinks by extraction with chloroform: isopropanol 1:1 (v/v). All linearity ranges were between 50 and 1,000 μg mL^?1 for all compounds both in beer and in peach juice. Limit of detection was between 1.3 and 34.2 μg mL^?1, limit of quantification was between 3.9 and 103.8 μg mL^?1, the range of recoveries was 73.0 and 112.6% for all drugs in both beverages. The reported method was sensitive, rapid, and suitable for the analysis of the spiked drinks as evidence of sexual assault and robbery phenomena.     

Stability of nonlocal difference schemes in a subspace

We consider a family of two-layer difference schemes for the heat equation with nonlocal boundary conditions containing the parameter γ. In some interval γ ∈ (1, γ ₊), the spectrum of the main difference operator contains a unique eigenvalue λ ₀ in the left complex half-plane, while the remaining eigenvalues λ ₁, λ ₂, …, λ _N?1 lie in the right half-plane. The corresponding grid space H _N is represented as the direct sum H _N = H ₀⊕H _N?1 of a one-dimensional subspace and the subspace H _N?1 that is the linear span of eigenvectors µ⁽¹⁾, µ⁽²⁾, …, µ^(N?1). We introduce the notion of stability in the subspace H _N?1 and derive a stability criterion.