Beta2-agonist extraction procedures for chromatographic analysis

Normally, different procedures were necessary to prepare sample matrices for chromatographic determination of β₂-agonists. The present review includes sampling, pre-treatment and extraction/purification for urine, plasma, liver, meat, feeds, hair and milk powder, as previous steps for chromatographic analysis of β₂-agonists. Six methodologies were especially revised for extraction/purification namely, liquid–liquid extraction, solid-phase extraction (SPE), matrix solid-phase dispersion, immunoaffinity chromatography, dialysis and supercritical fluid extraction. SPE was discussed in detail and five mechanisms were described: adsorption, apolar, polar, ion-exchange and mixed phase. A brief conclusion in this field was also outlined.     

A formal synthesis of (±)-physostigmine via 3,3-rearrangement of a bis-enamine

A new flexible approach to hexahydropyrrolo[2,3-b]indole system via the [3,3]-sigmatropic rearrangement of 1-(2′-methoxycarbonyl-N-methylvinylamino)skatole, culminating in the synthesis of (±)-desoxyeseroline, is described.     

Heterogeneity in styrene-butadiene latex films

Low-Tg styrene-butadiene (SB) latex films were investigated by noncontact atomic force microscopy and scanning electric potential microscopy, revealing a number of different morphologies and electric potential patterns across films cast from the same SB latex dispersions under the same conditions. Surface leveling and charge dispersion throughout the films are, thus, restrained even at temperatures above Tg and the minimum film-formation temperature. An unprecedented electric pattern is observed, in which the particle cores are more positive than the contacting particle outer layers. Different packing patterns, including cubic and hexagonal arrays, coexist in neighboring areas. Zonal centrifugation of the SB latex in sucrose density gradient shows that particles cover a broad range of densities. Thus, film surface heterogeneity is at least partly due to particle heterogeneity. Fractal dimensions of topographic profiles are lower than those of the electric potential profiles, showing that charge mobility is much more restrained than polymer chain motion at the film surface and that it imposes a limit to the charged chain-ends motion.     

First asymmetric hetero Diels-Alder reaction of 1-sulfinyl dienes with nitroso derivatives. A new entry to the synthesis of optically pure 1,4-imino-L-ribitol derivatives

Hetero Diels-Alder (HDA) cycloaddition of chiral 1-p-tolylsulfinyl-1,3-pentadiene with benzyl nitrosoformate, under mild conditions, yields 2H-1,2-oxazine 3 with complete regioselectivity and pi-facial diastereoselectivity. Sequential osmylation and protection of the resulting glycol gives the oxazine 5 which is directly transformed into enantiomerically pure 1,4,5-trideoxy-1,4-imino-L-ribitol 8 by reduction under Pd/C.     

Standard dilution analysis of beverages by microwave-induced plasma optical emission spectrometry

In this work, standard dilution analysis (SDA) is combined with microwave-induced plasma optical emission spectrometry (MIP OES) to determine seven elements in coffee, green tea, energy drink, beer, whiskey and cachaça (Brazilian hard liquor). No sample preparation other than simple dilution in HNO₃ 1% v v⁻¹ is required. Due to relatively low plasma temperatures, matrix effects may compromise accuracies in MIP OES analyzes of complex samples. The method of standard additions (SA) offers enhanced accuracies, but is time-consuming and labor intensive. SDA offers a simpler, faster approach, with improved accuracies for complex matrices. In this work, SDA's efficiency is evaluated by spike experiments, and the results are compared to the traditional methods of external calibration (EC), internal standard (IS), and standard additions (SA). SDA is comparable to the traditional calibration methods, and it provides superior accuracies for applications involving ethanol-containing beverage samples. The SDA-MIP OES procedure is effective. Using only two calibration solutions, it may be easily automated for accurate and high sample throughput routine applications.