Problems encountered with the routine application of HPLC to the analysis of carbamate pesticides

Summary This paper describes the determination of all carbamate pesticides mentioned in the Austrian regulations for pesticides and of some other carbamates commonly used in the EEC. Clean-up procedure is carried out by ethyl acetate extraction. Purification is by a liquid-liquid extraction step followed by use of a florisil column. Final detection of the carbamates is carried out by HPLC on silica gel and GLC respectively The method works well for all carbamates under consideration. Only benzimidazolamine-2, the decomposition product of benomyl and carbendazime cannot be determined by the method described. Therefore determination of benomyl, carbendazime and benzimidazolamine-2 was by hydrolysis of benomyl and carbendazime to benzimidazolamine-2, which is then determined by reversed-phase chromatography.     

Mesoporous micelle templated silica with incorporated C<Subscript>8</Subscript> and C<Subscript>18</Subscript> phase

Mesoporous silica material of MCM-41 type was synthesized by co-condensation of highly concentrated octyltriethoxysilane (OTEOS), octadecyltriethoxysilane (ODTEOS) and tetraethoxysilane (TEOS). The obtained hybrid materials were characterized using XRD, TG-DSC and low temperature adsorption/desorption of nitrogen. It was shown that the applied method of synthesis allows to obtain silica of MCM-41 type with a high degree of hydrocarbon saturation.     

Immobilization of thiabendazole-specific monoclonal antibodies to silicon substrates via aqueous silanization

Monoclonal antibodies specific for thiabendazole were immobilized to silicon, silicon dioxide, stoichiometric silicon nitride, and silicon-rich silicon nitride surfaces. This work provides the foundation for the development of a homogeneous sensor system for rapid detection and quantification of thiabendazole residues in produce and animal tissue. Immobilization was performed via aqueous silanization of the substrate followed sequentially by treatment with glutaraldehyde and contact with antibody solution in the presence of detergent. Surfaces were challenged with thiabendazole-horseradish peroxidase conjugate in an ELISA format to estimate immobilized antibody load. A stable and reproducible surface loading of 2 x 10¹¹ antibodies/cm² was obtained only after surfaces received postimmobilization treatments to remove nonspecifically adsorbed antibody. No difference in surface loading was noted when using 30% hydrogen peroxide rather than nitric acid for silanol activation. Little difference was noted among the antibody loadings achieved on the various silicon substrates. Bound antigen-enzyme conjugate was eluted with 0.1N acetic acid and reproducible surface activity was measured for up to four consecutive antigen challenges. Immobilized antibody surfaces were stabilized with 2% sucrose, dehydrated at 37‡C and stored in vacuum or stored at 4‡C in phosphate buffered saline containing 0.01% sodium azide without significant loss of activity.     

Current Trend in Synthesis,Post‐Synthetic Modifications and Biological Applications of Nanometal‐Organic Frameworks (NMOFs)

Since the early reports of MOFs and their interesting properties, research involving these materials has grown wide in scope and applications. Various synthetic approaches have ensued in view of obtaining materials with optimised properties, the extensive scope of application spanning from energy, gas sorption, catalysis biological applications has meant exponentially evolved over the years. The far‐reaching synthetic and PSM approaches and porosity control possibilities have continued to serve as a motivation for research on these materials. With respect to the biological applications, MOFs have shown promise as good candidates in applications involving drug delivery, BioMOFs, sensing, imaging amongst others. Despite being a while away from successful entry into the market, observed results in sensing, drug delivery, and imaging put these materials on the spot light as candidates poised to usher in a revolution in biology. In this regard, this review article focuses current approaches in synthesis, post functionalization and biological applications of these materials with particular attention on drug delivery, imaging, sensing and BioMOFs.     

Calorimetric approach to tetronic/water interactions

Tetronic^®comprises X-shaped copolymers formed by four poly(propylene oxide) (PPO) andpoly(ethylene oxide) (PEO) block chains bonded to an ethylene diamine centralgroup. Micellization behaviour of three representative Tetronics (T304, T904and T1307) was characterized to gain an insight into the interactions betweenthe copolymer unimers and the state of water in their solutions. The enthalpyof demicellization, recorded at 37°C in an isoperibol microcalorimeter,indicated that the process was in all cases exothermic and the enthalpy rankedin the order T1307≥T904>>T304. Micellization is entropy-driven owing tohydrophobic interactions between the PPO chains.DSC analysisshowed that the crystallization and melting peaks of the free water remainingin T304 and T904 solutions were progressively shifted toward lower temperaturesas the surfactant proportion increased, owing to a colligative effect. Boundwater corresponded to 3 water molecules per EO repeating unit. In the caseof T1307, which has longer PEO chains, a splitting of the melting peak wasobserved, one peak appearing around 0°C due to free water and anotherat –15°C due to interfacial water. As T1307 proportion raised, theenthalpy of the former decreased, whilst the enthalpy of the latter increased.In 40% T1307 solutions, interfacial water overcame the proportion of freewater; there being 1 interfacial and 3 bound water molecules per EO repeatingunit. Gaussian deconvolution of FTIR spectra also enabled to characterizethe evolution of free water as a function of Tetronic proportion. The dependenceof micellization and water interaction behaviour on Tetronics structure shouldbe taken into account to use these copolymers as drug solubilizers and micellarcarriers.     

Gas chromatographic trace analysis of underivatized nitrophenols

Summary A method for the gas chromatographic trace analysis of underivatized nitrophenols in ground-water is presented. Using a highly de-activated separation system a satisfactory precision for their quantitative GC analysis could be achieved by avoiding condensation of the solvent and by fast injection of the sample. The reproducibility of the peak areas of eleven nitrophenols in ethylacetate was <5 % RSD. Using a nitrogen-phosphorus detector detection limits were in a range from 10 to 30 pg. Within the concentration range from 0.1 to 10 ng μl⁻¹ the calibrations were linear with correlation coefficients >0.992. The approach described was applied to the analysis of nitrophenols in ground-water near a former ammunition plant, after preconcentration by continuous liquid/liquid extraction with ethylacetate. Using a GC-MS technique and retention times various nitrophenols were identified and then quantified in the μg/L-range by applying NPD.