Liquid chromatographic methodology for the characterization of orange juice

Liquid chromatographic (LC) methodology potentially useful for the characterization of orange juice, with particular regard to detecting adulteration of orange juice by computer pattern recognition analysis, has been developed. After dilution with methanol the juice is extracted with hexane to remove the carotenoids, which are chromatographed on a C18 column with an acetonitrile-methanol-methylene chloride mobile phase and detection at 450 nm. Further extraction of the juice with methylene chloride isolates the methoxylated flavones, which are chromatographed by reverse phase LC with an acetonitrile-methanol-water mobile phase and detection at 280 nm. The flavanone glycosides remaining in solution are chromatographed on a C18 column with an acetonitrile-water mobile phase and detection at 280 nm. The precisions of the heights of the 32 LC peaks selected for pattern recognition analysis were determined from 5 replicate analyses of a single juice. Coefficients of variation of the replicates ranged from 0.3 to 4.5%, with an average of 2.1%. Adulteration of products with sodium benzoate-fortified pulpwash or grapefruit juice can be detected by this method. Pattern recognition analysis of the data obtained for 80 authentic and 19 adulterated orange juices showed that the method is potentially useful for distinguishing between authentic and adulterated products.     

Protective effect of the AT137RQ and ARQK176 PrP alleles against classical scrapie in Sarda breed sheep

The susceptibility of sheep to scrapie is under the control of the host’s prion protein (PrP) gene and is also influenced by the strain of the agent. PrP polymorphisms at codons 136 (A/V), 154 (R/H) and 171 (Q/R/H) are the main determinants of susceptibility/resistance of sheep to classical scrapie. They are combined in four main variants of the wild-type ARQ allele: VRQ, AHQ, ARH and ARR. Breeding programmes have been undertaken on this basis in the European Union and the USA to increase the frequency of the resistant ARR allele in sheep populations. Herein, we report the results of a multi-flock study showing the protective effect of polymorphisms other than those at codons 136, 154 and 171 in Sarda breed sheep. All ARQ/ARQ affected sheep (n = 154) and 378 negative ARQ/ARQ controls from four scrapie outbreaks were submitted to sequencing of the PrP gene. The distribution of variations other than those at the standard three codons, between scrapie cases and negative controls, was statistically different in all flocks. In particular, the AT₁₃₇RQ and ARQK₁₇₆ alleles showed a clear protective effect. This is the first study demonstrating a protective influence of alleles other than ARR under field conditions. If further investigations in other sheep breeds and with other scrapie sources confirm these findings, the availability of various protective alleles in breeding programmes of sheep for scrapie resistance could be useful in breeds with a low frequency of the ARR allele and would allow maintaining a wider variability of the PrP gene.     

Comparison of endoscopy,histology, and cytokine mRNA of the equine gastric mucosa

In recent years, gastric ulceration has been recognized as a common, possibly performance-limiting disease, of adult horses. The aim of this study was to compare endoscopic features, histological diagnosis, and mRNA levels of various cytokines (TNF-α, IL-1β, and IL-13) from horse gastric biopsies. Eleven horses suffering from equine gastric ulcer syndrome and seven horses with normal histological gastric features were assessed. No correlation between endoscopic features and histology (i.e., the gold standard) was observed. Based on histological diagnosis, a significant (p < 0.05) increase in cytokine mRNA levels (specifically, TNF-α and IL-13) was observed in horses affected by equine ulcerative gastric syndrome.

     

Liquid chromatographic determination of sulfite in grapes and selected grape products

A liquid chromatographic (LC) method is described for the determination of sulfite in grapes and certain grape products. Sulfite is extracted from grapes with aqueous formaldehyde solution buffered at pH 5; free sulfite is converted to hydroxymethylsulfonate (HMS), which is extremely stable at pH 3-7. Subsequent heating to 80 degrees C for 30 min converts reversibly bound forms of sulfite to HMS. The extract is then analyzed by reverse-phase ion-pairing liquid chromatography, using a C18 column and a mobile phase of aqueous 0.005 M tetrabutylammonium ion in 0.05 M acetate, pH 4.7, and a flow rate of 1 mL/min. Aqueous KOH is added to the eluate to convert HMS to free sulfite, which is then treated with 5,5'-dithiobis[2-nitrobenzoic acid]. This reaction produces the 3-carboxy-4-nitrothiophenolate anion, which is determined by measurement of electronic absorption at 450 nm. For grapes spiked with HMS at 5-20 ppm (as SO2), recoveries ranged from 92 to 112%, with a coefficient of variation of 4.6%. The method was also used to determine sulfite in various grape products. Results were comparable to those obtained by the AOAC official Monier-Williams method.     

Transient electronic structure and melting of a charge density wave in TbTe3

Obtaining insight into microscopic cooperative effects is a fascinating topic in condensed matter research because, through self-coordination and collectivity, they can lead to instabilities with macroscopic impacts like phase transitions. We used femtosecond time- and angle-resolved photoelectron spectroscopy (trARPES) to optically pump and probe TbTe3, an excellent model system with which to study these effects. We drove a transient charge density wave melting, excited collective vibrations in TbTe3, and observed them through their time-, frequency-, and momentum-dependent influence on the electronic structure. We were able to identify the role of the observed collective vibration in the transition and to document the transition in real time. The information that we demonstrate as being accessible with trARPES will greatly enhance the understanding of all materials exhibiting collective phenomena.     

Electronic structure of solids with competing periodic potentials

When electrons are subject to a potential with two incommensurate periods, translational invariance is lost, and no periodic band structure is expected. However, model calculations based on nearly free one-dimensional electrons and experimental results from high-resolution photoemission spectroscopy on a quasi-one-dimensional material do show dispersing band states with signatures of both periodicities. Apparent band structures are generated by the nonuniform distribution of electronic spectral weight over the complex eigenvalue spectrum.     

Survey results of benzene in soft drinks and other beverages by headspace gas chromatography/mass spectrometry

Benzene, a carcinogen that can cause cancer in humans, may form at nanogram per gram levels in some beverages containing both benzoate salts and ascorbic or erythorbic acids. Through a series of reactions, a hydroxyl radical forms that can decarboxylate benzoate to form benzene. Elevated temperatures and light stimulate these reactions, while sugar and ethylenediaminetetraacetic acid (EDTA) can inhibit them. A headspace gas chromatography/mass spectrometry method for the determination of benzene in beverages was developed and validated. The method was used to conduct a survey of 199 soft drinks and other beverages. The vast majority of beverages sampled contained either no detectable benzene or levels below the U.S. Environmental Protection Agency's drinking water limit of 5 ng/g. Beverages found to contain 5 ng/g benzene or more were reformulated by the manufacturers. The amount of benzene found in the reformulated beverages ranged from none detected to 1.1 ng/g.     

Reverse phase ion pair high pressure liquid chromatographic determination of ethylenediaminetetraacetic acid in crabmeat and mayonnaise.

A method is described for the determination of ethylenediaminetetraacetic acid (EDTA) in crabmeat and mayonnaise. EDTA is extracted from the food sample with water and converted to its copper chelate, which is then quantitated by reverse phase ion pair high pressure liquid chromatography with ultraviolet detection. Maximum sensitivity is obtained with detection at about 254 nm; higher wavelengths may be used for enhanced specificity. Cleanup procedures for crabmeat and mayonnaise were improved by using a radiotracer method. Analyses of crabmeat and mayonnaise samples spiked at 3 different levels showed greater than 90% recovery of EDTA.     

The determination of semicarbazide (N-aminourea) in commercial bread products by liquid chromatography-mass spectrometry

Recently, semicarbazide has been found in food in jars sealed with cap liners that were manufactured using azodicarbonamide as a blowing agent. These reports raised the concern that the use of azodicarbonamide-an approved dough conditioner-may result in semicarbazide residues in bread. To answer this question, a method based upon the previously reported liquid chromatography/tandem mass spectrometry determination of the semicarbazone of o-nitrobenzaldehyde was utilized. The method adopted for this work includes an extensive cleanup and reaction with o-nitrobenzaldehyde at pH 3.5, rather than with the widely used 0.1 M HCl, to form the semicarbazone derivative. A stable isotope dilution assay was used to determine the free semicarbazide present in the bread products. Levels of semicarbazide ranged from 10 to 1200 ppb in commercial bread products with azodicarbonamide listed among their ingredients.