Simultaneous determination of Zilpaterol and other beta agonists in calf eye by gas chromatography/tandem mass spectrometry

Adrenergic drugs for growth promotion have been outlawed in European meat production; however, molecules such as Ractopamine and Zilpaterol are licensed for feeding swine and cattle in the United States, Mexico, and South Africa. Analysis of bovine retinal extracts has recently shown considerable extension in the detection period following withdrawal. Previous studies demonstrated that residual concentrations of Clenbuterol and related substances in retinal tissue were > 100 ng/g at day 50 of withdrawal. A method was developed to identify and simultaneously quantify Clenbuterol-like substances with anilinic moieties and drugs with phenolic and catecholic moieties, such as Ractopamine and Zilpaterol, in retinal tissue. The method was validated according to SANCO/1805/2000. After extraction in 0.1 N HCl, samples were cleaned up on C18 non-endcapped solid-phase extraction columns and analyzed as trimethylchlorosilane derivatives by gas chromatography/tandem mass spectrometry, electron impact mode. At concentrations of agonists between 62.5 and 250.0 ng/g in bovine retina, mean recoveries ranged from 85.3 to 94.8%, repeatability was < 9.6%, and within-laboratory reproducibility was < 10.5%. The decision limits (CCalpha) were within the range of 66.3-70.4 ng/g, and the detection capability (CCbeta) varied from 73.9 to 79.8 ng/g. Results are discussed in terms of a multiresidue approach to improve reliability of the monitoring strategy.     

Mass spectrometric synthesis. V. The gas-phase ion-molecule dimerization of some sulfur containing heterocycles

The gas-phase, ion-molecule reactions occurring in the ion source of a mass spectrometer between differently substituted thiazoles, employed as starting compounds for synthesis of polymers exhibiting semiconducting properties, have been studied in detail. The structural characterization of the dimeric moieties so obtained has been carried out by exact mass measurements, linked scans for metastable analysis and collisional spectroscopy.     

Synthesis and X-ray study of hexahydro- and tetrahydrophospholo-[2,3-d]isoxazoles,a new class of heterocycles of potential fungicidal activity

Hexahydro-, 5b-1 and 6a,f,1 and tetrahydrophospholo[2,3-d]isoxazoles 8, 9 and 10 were synthesized by 1,3-dipolar cycloaddition of nitrones 3b-1 and benzonitrile oxide ( 4 ) to 2,3-dihydro-1-phenyl-1H-phosphole 1-oxide ( 1 ) and 2,3-dihydro-1-ethoxy-1H-phosphole 1-oxide ( 2 ). The structural assignment to the compounds was confirmed by an X-ray study of two compounds of the series 5a and 5m . The compounds show a good activity as fungicides against Plasmopara viticola on vines and against Botrytis cinerea on apples. Compounds 5a-d showed weak to moderate activity as herbicides.     

The DNSev™ expert system in the auto-verification of tumour markers and hormones results

Most of the immunoassays workload is processed in clinical laboratories within a time span comparable to the clinical chemistry and the haematology assays and the analytical work is usually completed between 1:00 and 2:00 p.m. In order to accelerate the auto-verification of the results of tumour markers (Total and free PSA, CEA, CA 125, CA 15-3, CA 19-9, TPA, AFP, NSE, S 100 protein), and hormones (TSH, FT4, FT3, Prolactin, total testosterone) and Procalcitonin (PCT) we used DNSev^TM expert system implementing 13 rules based on decision levels/reference intervals and reference change values. The auto-verification procedure has been implemented after a 6-month trial in June 2004 and in 2005 the immunoassays section supervisor was able to verify about 500 results in about 30 min 5 days/week. We conclude that the auto-verification of immunoassays implemented in our laboratory is fast and consistent among different supervisors and leaves more time for an effective and timely interaction with clinicians and general practitioners.Presented at the 10th Conference Quality in the Spotlight, March 2005, Antwerp, Belgium     

Mesoporous benzene-silica hybrid materials with a different degree of order in the wall structure: an IR comparative study

Recent joint IR and computational work (Onida et al. J. Phys. Chem B 2005) has allowed a detailed characterization of the isolated silanols at the surface of highly ordered benzene-silica hybrid material. In the present paper, a similar characterization is provided for a less ordered sample. The comparison permits the assignment of IR features to the interaction of silanols either with one another or with benzene rings of the structure. The extent of structural imperfections appears to be limited, for example, no more than pairs of interacting silanols are found, readily healed by thermal treatment. Evidence is also provided that probe molecules with simultaneous H-acceptor and H-donor properties (benzene, methylacetylene) may interact with both the acidic proton in silanols and the electronic cloud in the framework aromatic rings.     

Synthesis of 3-acylamino-2-oxazolidinone derivatives through cyclic transformations of 5-aryl (or benzyl)-1,3,4-oxadiazol-2(3H)-one derivatives

New 3-acylamino-2-oxazolidinone derivatives 3 were obtained in good yields by reaction of 5-aryl (or benzyl)3-(2-hydroxyethyl)1,3,4-oxadiazol-2(3H)ones 1 with sodium ethylate. Treatment of ethyl 5-aryl-2-oxo-1,3,4-oxadiazole-3(2H)-acetates 7 with aromatic aldehydes in the presence of sodium ethylate or sodium hydride afforded 3-acylamino-5-aryl-4-ethoxycarbonyl-2-oxazolidinone derivatives as two trans- 5 and cis- 6 racemics. Only RS,SR-racemates were obtained with acetophenone under the same conditions.     

Thermal Rearrangement of Nitrone and Nitrile Oxide Cycloadducts to Bicyclopropylidene.(1) Synthesis of 3-Spirocyclopropane-4-pyridone and Furo[2,3-c]pyridine Derivatives

Bicyclopropylidene smoothly undergoes 1,3-dipolar cycloadditions to nitrones or nitrile oxides under different reaction conditions. The strained bisspirocyclopropanated isoxazolidines obtained from nitrones easily rearrange upon heating with selective opening of one of the two spirofused cyclopropane rings. This process produces 4-pyridone, 7-indolizinone, and 2-quinolizinone derivatives containing a spirocyclopropane moiety in the alpha-position to the carbonyl group in good yields. The same sequence of cycloaddition and rearrangement can be achieved in a "one-pot" operation with considerable benefit for the reaction yield. Bisspirocyclopropaneisoxazolines obtained from nitrile oxides are more stable than their saturated counterparts and rearrange only at higher temperature less chemoselectively. Opening of both spiro-fused cyclopropyl rings followed by aromatization produces interesting 2-substituted dihydrofuro[2,3-c]pyridine derivatives.     

Interactions of aziridines with nickel complexes: oxidative-addition and reductive-elimination reactions that break and make C-N bonds

Reaction of the N-tosylaziridines (p-CH(3)C(6)H(4)SO(2))NCH(2)CHR (1a, R = H; 1b, R = Me; 1c, R = n-Bu; 1d, R = i-Pr) with (bpy)Ni(cod) (2; bpy = 2,2'-bipyridine; cod = 1,5-cyclooctadiene) or (bpy)NiEt(2) (3) results in elimination of cod or butane from 2 and 3, respectively, and oxidative addition of an aziridine C-N bond to give the azametallacyclobutane complexes (bpy)Ni(NTosCHRCH(2)) (4a, R = H; 4b, R = Me; 4c, R = n-Bu; 4d, R = i-Pr) as maroon solids in 50-70% isolated yields. The structure of 4b exhibits a puckered four-membered azametallacycle containing a pyramidal nitrogen and with Ni-N(1) = 1.911(5) A; the tosyl group on N and the methyl substituent on the adjacent C are disposed in an anti conformation. The monodeuterated aziridine syn-(p-CH(3)C(6)H(4)SO(2))NCHDCH-n-Bu (1e) reacts with either 2 or 3 to give (bpy)Ni[NTosCH(n-Bu)CHD] (4e) in 60-65% yield, having an anti arrangement of the methine and methylene protons in the azametallacycle, and indicates that >95% inversion of stereochemistry has occurred at the methylene carbon during the oxidative-addition reaction. When the azametallacyclobutane complexes 4a-e are exposed to oxygen, oxidatively induced reductive elimination ensues, giving the free aziridines in 30-60% isolated yields. In the oxidation of 4e, the product aziridine is spectroscopically identical to its parent, 1e, indicating the elimination that forms the C-N bond also proceeds with inversion of stereochemistry (approximately 92% by (1)H NMR) at the methylene carbon.     

The isopropylsulfinyl group: a useful chiral controller for the asymmetric aziridination of sulfinylimines and the organocatalytic allylation of hydrazones

[reaction: see text] A comparative study shows that the isopropylsulfinyl group for which an enantiodivergent and highly diastereoselective approach is reported behaves better than the tert-butylsulfinyl and p-tolylsulfinyl groups, both in terms of reactivity and stereoselectivity in the Corey-Chaykovsky reaction of chiral sulfinylimines and the organocatalytic allylation of acyl hydrazones.