Determination of oxadixyl in wines by liquid chromatography- tandem mass spectrometry: single-laboratory and interlaboratory validation study.

A direct injection LC/MS/MS method for the determination of the pesticide oxadixyl in wines was developed and validated. A sample divert valve was used to deliver the fraction that contained oxadixyl to the mass spectrometer's electrospray ionization source. Oxadixyl was monitored and quantitated using two transitions in multiple reaction monitoring mode. The method demonstrated recoveries of 99.2 ± 2.0 and 96.7± 5.2% for red and white wines, respectively, a linearity range of 2-20 µg/L, LOD at 0.7 µg/L, LOQ of 2.0 µg/L, and precision values of 8.2% (RSDr) and 6.2% (RSDR). Direct injection of the wine onto a C18 ultra-performance LC column allowed automation and high throughput screening. Benefits of this approach includeminimal sample preparation, short (3 min) run times, and the use of matrix-matched calibration standards, which minimize the matrix effect due to interferences from wine phenolics, sugars, and various other components. The method's performance characteristics were not statistically different for white and red wines. An additional interlaboratory validation study involved 12 laboratories and demonstrated gooddata agreement with HorRat values ranging from 0.23 to 0.52.

Beginning of viniculture in France.

Chemical analyses of ancient organic compounds absorbed into the pottery fabrics of imported Etruscan amphoras (ca. 500-475 B.C.) and into a limestone pressing platform (ca. 425-400 B.C.) at the ancient coastal port site of Lattara in southern France provide the earliest biomolecular archaeological evidence for grape wine and viniculture from this country, which is crucial to the later history of wine in Europe and the rest of the world. The data support the hypothesis that export of wine by ship from Etruria in central Italy to southern Mediterranean France fueled an ever-growing market and interest in wine there, which, in turn, as evidenced by the winepress, led to transplantation of the Eurasian grapevine and the beginning of a Celtic industry in France. Herbal and pine resin additives to the Etruscan wine point to the medicinal role of wine in antiquity, as well as a means of preserving it during marine transport.

Ancient Egyptian herbal wines.

Chemical analyses of ancient organics absorbed into pottery jars from the beginning of advanced ancient Egyptian culture, ca. 3150 B.C., and continuing for millennia have revealed that a range of natural products--specifically, herbs and tree resins--were dispensed by grape wine. These findings provide chemical evidence for ancient Egyptian organic medicinal remedies, previously only ambiguously documented in medical papyri dating back to ca. 1850 B.C. They illustrate how humans around the world, probably for millions of years, have exploited their natural environments for effective plant remedies, whose active compounds have recently begun to be isolated by modern analytical techniques.

Comparison of methods for extraction of ethyl carbamate from alcoholic beverages in gas chromatography/mass spectrometry analysis.

A procedure to analyze ethyl carbamate (EC) by gas chromatography/mass spectrometry was optimized and validated. Deuterated EC (d5-EC) was added to the samples as an internal standard followed by extraction with polystyrene crosslinked polystyrene cartridges using minimal volumes of ethyl acetate. The EC response was measured in selective ion monitoring (SIM) mode and found to be linear in the range between the limit of quantitation (10 micro/L) and 1000 microg/L. EC recoveries varied from 92 to 112%, with the average value of 100 +/- 8%. The procedure compared well (r2 = 0.9970) with the existing AOAC Official Method with the added benefits of minimal solvent usage and reduced matrix interferences.

Identification of residues that confer alpha-conotoxin-PnIA sensitivity on the alpha 3 subunit of neuronal nicotinic acetylcholine receptors.

Neuronal nicotinic receptors composed of the alpha3 and beta2 subunits are at least 1000-fold more sensitive to blockade by alpha-conotoxin-PnIA than are alpha2beta2 receptors. A series of chimeric subunits, formed from portions of alpha2 and alpha3, were coexpressed with beta2 in Xenopus oocytes and tested for toxin sensitivity. We found determinants of toxin sensitivity to be widely distributed in the extracellular domain of alpha3. Analysis of receptors formed by a series of mutant alpha3 subunits, in which residues that differ between alpha3 and alpha2 were changed from what occurs in alpha3 to what occurs in alpha2, allowed identification of three determinants of alpha-conotoxin-PnIA sensitivity: proline 182, isoleucine 188, and glutamine 198. Comparison with determinants of alpha-conotoxin-MII and kappa-bungarotoxin sensitivity on the alpha3 subunit revealed overlapping, but distinct, arrays of determinants for each of these three toxins. When tested against an EC50 concentration of acetylcholine, the IC50 for alpha-conotoxin-PnIA blockade was 25 +/- 4 nM for alpha3beta2, 84 +/- 7 nM for alpha3P182Tbeta2, 700 +/- 92 nM for alpha3I188Kbeta2, and 870 +/- 61 nM for alpha3Q198Pbeta2. To examine the location of these residues within the receptor structure, we generated a homology model of the alpha3beta2 receptor extracellular domain using the structure of the acetylcholine binding protein as a template. All three residues are located on the C-loop of the alpha3 subunit, with isoleucine 188 nearest the acetylcholine-binding pocket.

Modulation of neuronal nicotinic acetylcholine receptors by mercury.

Mercuric chloride exerted a biphasic modulatory effect on rat neuronal nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus laevis oocytes as heteromers of the alpha3 or alpha4 and beta2 or beta4 subunits. The degree of modulation was subunit-dependent, with beta4-containing receptors displaying greater potentiation and alpha4-containing receptors displaying greater inhibition. Thus, alpha4beta4 receptors displayed both robust potentiation and robust inhibition. During prolonged coapplication of HgCl(2), first potentiation then inhibition of the acetylcholine (ACh) response was observed. Upon coapplication of 1 microM HgCl(2), a 2-fold increase in ACh-induced current was achieved in 55 +/- 1 s. With continued HgCl(2) application, the ACh response was slowly inhibited until, after 5 min, less than 10% of the initial response remained. By measuring potentiation at its peak and inhibition 5 min after the start of HgCl(2) coapplication, we obtained EC(50) and IC(50) values of 262 +/- 75 and 430 +/- 72 nM, respectively. HgCl(2) potentiation was voltage-dependent, increasing at more positive holding potentials. Upon washout of mercury chloride, potentiation reversed with a t(1/2) of 4.6 min. Inhibition reversed more slowly, with less than half the initial response recovered after 15 min of wash. Although free cysteine residues are common targets for mercury, elimination of all free cysteines located in the extracellular domains of the alpha4 and beta4 subunits did not alter the effects of mercuric chloride. Potentiation and inhibition of neuronal nAChRs may occur through action at a transmembrane or cytoplasmic location after passive diffusion of mercuric chloride across the plasma membrane.