Evaluation of new selective molecularly imprinted polymers prepared by precipitation polymerisation for the extraction of phenylurea herbicides.

Three different molecularly imprinted polymers (MIPs) have been prepared by precipitation polymerisation using linuron (LIN) or isoproturon (IPN) (phenylurea herbicides) as templates and methacrylic acid (MAA) or trifluormethacrylic acid (TFMAA) as functional monomers. The ability of the different polymers to selectively rebind not only the template but also other phenylurea herbicides has been evaluated. In parallel, the influence of the different templates and functional monomers used during polymers synthesis on the performance of the obtained MIPs was also studied through different rebinding experiments. The experimental binding isotherms were fitted to the Langmuir-Freundlich isotherm allowing to describe the kind of binding sites present in the imprinted polymers under study. It was concluded that TFMAA-based polymer using IPN as template presents the best properties to be used as a selective sorbent for the extraction of phenylurea herbicides.

Clean up of phenylurea herbicides in plant sample extracts using molecularly imprinted polymers.

Two different molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using linuron or isoproturon (phenylurea herbicides) as templates and trifluormethacrylic acid as functional monomer. These materials were used as selective sorbents in the development of molecularly imprinted solid-phase extraction (MISPE) procedures for the determination of several phenylurea herbicides (fenuron, metoxuron, chlortoluron, isoproturon, metobromuron, and linuron) in plant samples extracts. The MISPE procedures were fully optimized and applied to the clean up of selected phenylurea herbicides in carrot, potato, corn, and pea sample extracts and finally determined by HPLC-UV at 244 nm. Although a high degree of clean up was obtained, a decrease of the MIP recognition capabilities was observed in subsequent runs. Thus, a previous clean up protocol based on the use of a non-imprinted polymer was used to prevent the loss of MIP performance and to ease the removal of interferences. Following this procedure, namely two-step MISPE, matrix compounds were almost completely removed by the non-imprinted polymer retaining the ability of MIPs to selectively rebind target analytes unaltered. The developed MISPE procedures allowed the screening of phenylurea herbicides in plant samples at concentration levels required by established European maximum residue limits.

Multicenter evaluation of the efficacy and safety of gatifloxacin in Mexican adult outpatients with respiratory tract infections.

Respiratory tract infections (RTIs), the most common indication for outpatient antimicrobial therapy, impose a heavy medical and societal burden and present a difficult therapeutic challenge in the face of increasing pathogen resistance worldwide. Gatifloxacin is a new broad-spectrum fluoroquinolone with excellent activity against prevalent respiratory bacteria, including penicillin-resistant Streptococcus pneumoniae and atypical pathogens. A multicenter, open-label, noncomparative surveillance study carried out in Mexico evaluated the safety and efficacy of oral gatifloxacin 400 mg once daily in 17,923 adult outpatients with community-acquired pneumonia (CAP) (n = 3322), acute exacerbations of chronic bronchitis (AECB) (n = 5885), and acute bacterial sinusitis (n = 8716). Voluntary, unpaid physician participation contributed to an unbiased study design. Physician-assessed global rate of cure or improvement was 96.3%; efficacy was 95.8% in CAP, 96.1% in AECB, and 96.4% in sinusitis. The incidences of relapse (1.5%) and therapeutic failure (0.7%) were low. The most commonly reported adverse events, nausea (2.76%), headache (2.20%), and dizziness (1.33%), were generally mild and self-limited. Oral gatifloxacin 400 mg once daily is effective and safe for patients with CAP, AECB, and acute sinusitis.

The use of modified divinylbenzene-polystyrene resins in the separation of fermentation products. A case study utilizing amino acids and a dipeptide.

The adsorption of phenylalanine, aspartic acid, asparagine and aspartame from phosphate-buffered aqueous solutions with modified divinyl-benzene-polystyrene resins has been investigated using high pressure liquid chromatography (HPLC). The pH studied was 2.8, the temperature range was 293-313 K and the ionic strength was maintained at 1.0 mol dm-3. Over the range of variables investigated, the adsorption isotherms are linear and may be characterized by temperature and pH-dependent apparent adsorption equilibrium constants, characteristic of the resin-adsorbate system. By studying the dependence on temperature of this adsorption constant, heats of adsorption and entropy of adsorption have been estimated. In terms of the heat liberated on adsorption, the amino acids and a dipeptide can be ranked thus: aspartame > phenylalanine > aspartic acid > asparagine.