N-1 Substituted ethyl 4-pyrazolecarboxylates: Synthesis and spectroscopic investigations

The synthesis of various N-1 substituted ethyl 4-pyrazolecarboxylates via reaction of ethyl 2-formyl-3-oxo-propionate (= ethoxycarbonylmalondialdehyde) with appropriately substituted hydrazines is described. Moreover, detailed nmr-spectroscopic investigations with the title compounds are presented.     

Operation of KrF and ArF tunable excimer lasers without Cassegrain optics

A commercial tunable excimer laser consists of an oscillator-amplifier combination. The oscillator produces high-quality light that is sent to the amplifier and is distributed throughout the amplifier cavity via Cassegrain optics. We describe here two alternative approaches, a single-pass configuration for use with KrF and a triple-pass configuration with ArF, both of which do away with the Cassegrain optics. In each approach, the beam energy is the same as with Cassegrain optics. For KrF, the changes provide better locking, a higher degree of linear polarization, and a better spatial beam homogeneity, but a poorer beam divergence. For ArF, there is also better beam homogeneity, but the locking efficiency and divergence are not as good as with Cassegrain optics.     

The Isolation,Structure, and Synthesis of Davana Ether,an Odoriferous Compound of the Oil of Artemisia pallens Wall.

Several stereoisomers of 2,6,10-trimethyl-2:5, 7:10-diepoxy-dodeca-3,5,11-triene ( 3 ) have been isolated from the oil of Artemisia pallens. The synthesis of the isomeric mixture is described.     

Chemical surface modifications of microfibrillated cellulose

Microfibrillated cellulose (MFC) was prepared by disintegration of bleached softwood sulphite pulp through mechanical homogenization. The surface of the MFC was modified using different chemical treatments, using reactions both in aqueous- and organic solvents. The modified MFC was characterized with fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Epoxy functionality was introduced onto the MFC surface by oxidation with cerium (IV) followed by grafting of glycidyl methacrylate. The length of the polymer chains could be varied by regulating the amount of glycidyl methacrylate added. Positive charge was introduced to the MFC surface through grafting of hexamethylene diisocyanate, followed by reaction with the amines. Succinic and maleic acid groups could be introduced directly onto the MFC surface as a monolayer by a reaction between the corresponding anhydrides and the surface hydroxyl groups of the MFC.     

Fast quantitation of 5-hydroxymethylfurfural in honey using planar chromatography

An approach for rapid quantitation of 5-hydroxymethylfurfural (HMF) in honey using planar chromatography is suggested for the first time. In high-performance thin-layer chromatography (HPTLC) the migration time is approximately 5 min. Detection is performed by absorbance measurement at 290 nm. Polynomial calibration in the matrix over a range of 1:80 showed correlation coefficients, r, of ≥ 0.9997 for peak areas and ≥ 0.9996 for peak heights. Repeatability in the matrix confirmed the suitability of HPTLC–UV for quantitation of HMF in honey. The relative standard deviation (RSD, %, n = 6) of HMF at 10 ng/band was 2.9% (peak height) and 5.2% (peak area); it was 0.6% and 1.0%, respectively, at 100 ng/band. Other possible detection modes, for example fluorescence measurement after post-chromatographic derivatization and mass spectrometric detection, were also evaluated and can coupling can be used as an additional tool when it is necessary to confirm the results of prior quantitation by HPTLC–UV. The confirmation is provided by monitoring the HMF sodium adduct [M + Na]⁺ at m/z 149 followed by quantitation in TIC or SIM mode. Detection limits for HPTLC–UV, HPTLC–MS (TIC), and HPTLC–MS (SIM) were 0.8 ng/band, 4 ng/band, and 0.9 ng/band, respectively. If 12 μL honey solution was applied to an HPTLC plate, the respective detection limits for HMF in honey corresponded to 0.6 mg kg⁻¹. Thus, the developed method was highly suitable for quantitation of HMF in honey at the strictest regulated level of 15 mg kg⁻¹. Comparison of HPTLC–UV detection with HPTLC–MS showed findings were comparable, with a mean deviation of 5.1 mg kg⁻¹ for quantitation in SIM mode and 6.1 mg kg⁻¹ for quantitation in TIC mode. The mean deviation of the HPTLC method compared with the HPLC method was 0.9 mg kg^-1 HMF in honey. Re-evaluation of the same HPTLC plate after one month showed a deviation of 0.5 mg kg⁻¹ HMF in honey. It was demonstrated that the proposed HPTLC method is an effective method for HMF quantitation in honey.      

Automated column-switching high-performance liquid chromatographic determination of flumequine and oxolinic acid in extracts from fish

Two methods for automated analysis of extracts from edible muscle tissue of Atlantic salmon are described. Oxolinic acid and flumequine are extracted with phosphate buffer pH 9, and the extracts are analysed by high-performance liquid chromatography using a column-switching system. One method applies on-line concentration and clean-up of the extracts on a precolumn packed with polystyrene-divinylbenzene. This method was useful for the analysis of oxolinic acid and flumequine in the microgram/g range. The other method was based on on-line dialysis and concentration of the dialysate on the polymeric precolumn. This method was shown to be a reliable method for residue analysis, and the limit of detection was 2 ng/g for oxolinic acid and 3 ng/g for flumequine with fluorescence detection.