Manfred Reichenbächer

Method development for the determination of anthocyanins in red wines by high-performance liquid chromatography and classification of German red wines by means of multivariate statistical methods

A simple and fast HPLC method without sample pretreatment is described for the separation of anthocyanins in red wines using a new pH-stable stationary phase. The linearity between peak area and concentration and ruggedness of the method were checked. Investigations were made about the safekeeping of red wine samples concerning anthocyanins. Classification of 52 different wine samples was performed by multivariate statistical methods.

Analysis of Wine Bouquet Components Using Headspace Solid‐Phase Microextraction‐Capillary Gas Chromatography

Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds.

Challenges in molecular structure determination

Mass Spectrometry.- Vibrational Spectroscopy.- Electron Absorption Spectroscopy.- Nuclear Magnetic Resonance Spectroscopy (NMR).- Molecular Structure Determination by Means of Combined Application Methods.- Tables.

Challenges in Analytical Quality Assurance

Challenges in analytical quality assurance , Challenges in analytical quality assurance , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

Thermochromism and photochromism of aryl substituted acyclic azines1: Uncatalised and acid-catalised thermal isomerisation

Abstract The photochemical E-Z isomerisation of the benzophenone-9-anthraldehyde azine (1), benzophenone-9-acridine aldehyde azine (2) and 9-anthraldehyde azine (3) is thermally reversible. The thermal reaction gives the same isomers as the photochemical reaction. We have studied the mechanism of the thermal isomerisation of these azines. Our results are in accordance with an inversion of the N atom which is connected with a rotation movement about the N-N single or the CN double bond.

Thermochromism and photochromism of aryl-substituted acyclic azines II: Photokinetics

Abstract Acyclic azines with higher condensed aromatic and heterocyclic substituents are photochromic and show both thermal isomerization and photochemical isomerization. From the point of view of formal kinetics the azines can be divided into four reaction types depending on the substituents R i . The correspondence of the expected formal kinetic behaviour of the azines with the experimental results is a direct proof of a photochemical E – Z isomerization of these compounds. We investigated acyclic azines which fulfil all criteria of a complicated unitary photoreaction of the type A ⇌ B as well as those azines showing a reversible consecutive photoreaction A ⇌ B ⇌ C. All quantum yields were determined using formal kinetics.

Thermochromism and photochromism of aryl-substituted acyclic azines III: Investigations on the mechanism of photochemical isomerization

Abstract We studied the reaction mechanism of the unsensitized as well as the sensitized photochemical E — Z and Z — E isomerizations of benzophenone-9-anthraldehyde azine. The photochemistry of this compound follows a unitary E ⇌ Z reaction. For qualitative investigations we used benzophenone-9-acridinealdehyde azine, 9-anthranyl-2-pyridinealdehyde azine, 9-anthranyl-3-quinolinealdehyde azine, 9-anthranyl-9-acridinealdehyde azine and 9-acridinealdehyde azine. The experimental results are consistent with the following mechanism for the photoisomerization of azines. In the photochemical E — Z isomerization the S 1 state of the E isomer is reactive; sensitization of the triplet state does not induce the reaction. A singlet mechanism is also very probable for the Z — E isomerization. The most effective photophysical processes competing with isomerization are intersystem crossing in the E isomer and radiationless internal conversion in the Z isomer.

Electronic Absorption Spectroscopy

According to quantum mechanics, the double bonds in conjugated systems are weakened. Conversely single bonds are stronger in the S1 state resulting in changed energy barriers for the rotation around the respective bond in the ground (S0) and first excited state (S1) of a conjugated system; see Fig. 3.21 for the structure moiety aryl–C=C–

Solution to quality assurance challenge 11

The regression model must be validated in order to verify that the chosen model adequately describes the relationship between the two variables x and y, and to check the assumptions of normality and homoscedasticity of variance, or in other words that the variances of the residuals are constant across the working range. When these variances are not equal the assumption of variance homoscedasticity is violated, and we conclude that there is heteroscedasticity. If the assumption of homoscedasticity of variance is violated, the simple least-squares procedure cannot be used without reducing the reliability of the estimations. In this case it is necessary to use a weighted least squares procedure [1, 2]. In the challenge referred to here, the highest calibration standard (500 μg benzene/l) is 100 times greater than the lowest one (5 μg/l), so the variance is not expected to be constant across the working range. Homoscedasticity of variance can be verified using Cochran’s test [3]. This test is appropriate for multiple comparisons of variance if all groups have the same number of values. Cochran’s criterion is based on comparing s 2 with all the other variances:

Synthesis and biological activities of 2β-chloro-, 2β-fluoro-, and 2β-methoxy-1α,25-dihydroxyvitamin D3

Abstract Using 1α,2α-oxido-cholesta-5,7-diene-3β,25-diol ( 2 ) as a starting material, the provitamins of calcitriol with an additional 2β-chloro-, 2β-fluoro-, and 2β-methoxy-substituent ( 3,4,5 ) are obtained by transdiaxial opening of the oxirane ring with nucleophiles. An efficient irradiation process is described and used for the synthesis of the 2β-substituted calcitriols NS2 (2β-Cl), NS6 (2β-F), and NS7 (2β-OCH 3 ). The affinity of these three vitamin D 3 derivatives to the vitamin D receptor (VDR) and was determined. These three A-ring derivatives of 1,25(OH) 2 D 3 were further tested for their proliferation-inhibitory and anti-adipogenic activity and gene regulatoric activity in the vitamin D 3 -sensitive, murine, mesenchymal cell line C3H10T 1 2 . The VDR-affinity of the 2β-chloro derivative, NS2 (2β-Cl), was identical to 1,25(OH) 2 D 3 and its vitamin D binding protein (DBP)-affinity was in the range of 1,25(OH) 2 D 3 . NS2 inhibited the proliferation of C3H10T 1 2; (BMP-4)-cells in the presence of fetal calf serum (FCS) 9 times, and, in the absence of FCS, 111 times lower, as compared with 1,25(OH) 2 D 3 . The ID 50 dose of adipogenesis-inhibition of NS2 was 13 times higher than the ID 50 dose of 1,25(OH) 2 D 3 . NS6 (2β-F) displayed a slightly higher affinity than 1,25(OH) 2 D 3 to the VDR and DBP-affinity. The proliferation-inhibitory activity in the presence of FCS was 90 times higher, as compared with 1,25(OH) 2 D 3 . In the FCS-free proliferation assay NS6 displayed an inhibitory activity in the range of 1,25(OH) 2 D 3 . NS6 showed an 5 times higher potency to inhibit (pre)adipocyte-differentiation in C3H10T 1 2 (BMP-4)-cells than 1,25(OH) 2 D 3 . NS7 (2β-OCH 3 ) showed the lowest VDR-affinity and the highest DBP-affinity of the tested substances, as compared with 1,25(OH) 2 D 3 (11 times lower and 35 times higher respectively). Its proliferation-inhibitory activity in the FCS-free medium was 9 times and in the FCS-containing assay 67 times lower in comparison with 1,25(OH) 2 D 3 . A 1250 times higher NS7 -dose was needed to reach the anti-adipogenic potency of 1,25(OH) 2 D 3 . All tested substances displayed a similar ability to activate a vitamin D responsive element-regulated reporter gene compared to 1,25(OH) 2 D 3 ( NS2 and NS6 : 1.3 times higher activity; NS7 : 1,4 times lower activity).