Resonant nano-cluster devices

The resonance-enhanced absorption (REA) by metal clusters on a surface is an effective technique on which to base bio-optical devices. A four-layer device consisting of a metal mirror, a polymer or glass-type distance layer, a biomolecule interaction layer and a sub-monolayer of biorecognitively bound metal nano-clusters is reported. Experiments indicate a strong influence of the resonator homogeneity on the absorption maximum. Layer stability plays an important role in the overall performance of the device. Techniques and optimised lab protocols to set up biochips that use the REA process in the detection are presented. The sensors show one to three narrow reflection minima in the visible and or infra-red (IR) part of the spectrum and therefore they do not suffer from the spectral limitations associated with spherical gold colloids. Metal clusters (synthesised by thermal step reduction) as well as metal- dielectric shell clusters (synthesised by various shell deposition processes) are used to precisely shift the readout of the device to any frequency in the visible and near IR range. Disposable single-step protein chips, DNA assays as well as complex biochip arrays are established that use various DNARNA, antigen-antibody and protein-protein interaction systems.     

Determination of Bisphenol A diglycidyl ether (BADGE) and its hydrolysis products in canned oily foods from the Austrian market

 Bisphenol A diglycidyl ether (BADGE) is determined in canned oily foods from Austria using a new simplified HPLC method. Samples are extracted with pentane, back extracted with methanol, and finally dissolved in the mobile phase (cyclohexane/tert–butyl methyl ether). Separation is performed on a normal-phase HPLC column using fluorescence detection. Verification of the BADGE-containing peak is carried out by using off-line GC-MS. Additionally, the synthesis and determination of BADGE hydrolysis products, Bisphenol A bis(2,3-dihydroxypropyl) ether (BADGE.2H₂O) and Bisphenol A glycidyl (2,3-dihydroxypropyl) ether (BADGE.H₂O) are presented. From 67 analyzed cans, containing various fatty meat or fish products, 16% were above the maximum quantity of 1 mg/kg tolerated by the European Community, 45% were in the range between 0.1–1 mg/kg, 24% between 0.02 and 0.1 mg/kg, and in 15% the BADGE concentrations were below the detection limit of 0.02 mg/kg. The hydrolysis product BADGE.H₂O was not detected in any sample, whereas BADGE.2H₂O was found in some samples up to a concentration of 0.5 mg/kg. Received: 11 May 1998 / Revised version: 1 July 1998     

Simultaneous determination of bisphenol A-diglycidyl ether, bisphenol F-diglycidyl ether and their hydrolysis and chlorohydroxy derivatives in canned foods

A new method for the simultaneous determination of bisphenol A-diglycidyl ether (BADGE), bisphenol F-diglycidyl ether (BFDGE) and their hydrolysis and chlorohydroxy derivatives in canned foods is presented. Oily and aqueous food samples were extracted with tert-butyl methyl ether and acetonitrile, respectively. The compounds in both extracts were determined by using reverse-phase gradient high-performance liquid chromatography with fluorescence detection. Optimization of extraction and chromatographic determination is outlined in detail. After validation the method was used to analyze various canned food samples, such as tuna and sardine in oil, vegetables, fruit cocktails, etc. In none of the samples were significant amounts ( >100 μg/kg) of BADGE or BFDGE found, whereas in most samples BADGE/BFDGE chlorohydroxy compounds were detected. These originate most probably from the use of organosol varnishes instead of epoxy resins. Risk assessment and regulations of these compounds by the European Union are urgently needed. Additionally, the syntheses and characterization of the not available standard compounds bisphenol A-p-glycidyl-p′-(3-chloro-2-hydroxypropyl) ether (BADGE.HCl) and bisphenol A-p-(2,3-dihydroxypropyl)-p′-(3-chloro-2-hydroxypropyl) ether (BADGE.HCl.H₂O) are presented. Received: 28 July 1999 / Revised version: 29 October 1999     

Multinuclear metal nucleobase complexes

Of all properties of metal nucleobase complexes, formation of multinuclear species appears to be an outstanding feature. After a brief introduction into well known polymeric metal nucleobase complexes, three aspects recently Studied in our laboratory will be dealt with in more detail: (i) Heteronuclear complexes derived from trans-[(amine)(2)Pt(1-MeC)(2)](2+) (1-MeC=1-methylcytosine). They form, e. g. with Pd(II) or Hg(II), upon single deprotonation of the exocyclic amino group of each 1-MeC ligand, compounds of type trans-[(amine)(2)Pt(1-MeC-)(2)MY](n+), displaying Pt-M bond formation. (ii) Cyclic nucleobase complexes derived from cis-a(2)Pt(II). A cyclic compound of composition {[(en)Pt(UH-N(1),N(3))](4)}(4+) (UH=monoanion of unsubstituted uracil) is presented and the analogy with organic calix-[4]-arenes is pointed out. (iii) Cyclic nucleobase complexes from trans-a(2)Pt(II). Possible ways for the preparation of macrocyclic nucleobase complexes containing trans-a(2)Pt(II) linkages are outlined and precursors and intermediates are presented.     

Phenolic composition and antioxidant activity of Rocha pear and other pear cultivars – A comparative study

The phenolic profile and the antioxidant activity of Rocha pear, a Portuguese pear cultivar, were determined and compared with the commercially available pear varieties Comice, Abate, General Leclerc and Passe Crassane. Phenolic composition of the methanolic extracts of these pears was determined by high performance liquid chromatography with diode array detection (HPLC-DAD), while antioxidant activities were evaluated using three complementary test systems: DPPH radical scavenging activity, ferric reducing power capacity and β-carotene/linoleic acid bleaching assay. When compared to the studied varieties, Rocha pear (peel and flesh) presented the highest content of total phenolics. Among them, chlorogenic, syringic, ferulic and coumaric acids, arbutin and (?)-epicatechin were detected as major components. In addition, among the tested varieties, Rocha pear presented the best antioxidant activities in the DPPH and ferric reducing power assays.     

Experimental Characterization of Short Fiber-Reinforced Composites on the Mesoscale by Indentation Tests

Applied Composite Materials - Indentation tests are widely used to characterize the material properties of heterogeneous materials. So far there is no explicit analysis of the spatially distributed...     

Kapillargaschromatographisches Prüfverfahren auf Zusätze von synthetischer DL-Äpfelsäure zu Obsterzeugnissen

A method for the determination of D-malic acid in products of fruits is presented. After addition of undecanoic acid as internal standard the dehydrated sample is extractive methylated by conc. hydrochloric acid, methanol and anhydrous magnesium sulfate. The extract is subjected to gaschromatographic separation on a chiral phase. Quantification of D-malic acid is done by the method of standard addition. The relative standard deviation is in the range of 1,8–4,4%, the detection limit 2,1–2,7 mg/l, the limit of quantitation 3,6–4,1 mg/l. Measures of fruit juice, fruit wine, wine and vinegar are tabulated.