Application of the chromatographic retention index system for the estimation of the calibration constants of permeation passive samplers with polydimethylsiloxane membranes

The paper presents the results of research on the calibration of permeation passive samplers equipped with polydimethylsiloxane (PDMS) membranes using the physico-chemical properties of the analytes. Strong correlations were found between the calibration constants of the samplers and the linear temperature-programmed retention indices of the analytes determined on columns coated with pure PDMS (r2 = 0.914). These correlations make it possible to estimate the calibration constants for unidentified analytes, which is impossible when using conventional procedures. This, in turn, enables the deployment of permeation passive samplers in the same way in which active samplers are deployed. The reproducibility of the calibration constants determined in different laboratories and retention indices determined using different chromatographic systems was very good, indicating that the calibration constants estimated using this approach should be reproducible as well. The approach proposed should lead to more widespread use of permeation passive samplers.     

The synthesis and thermal,optical and electrical properties of novel aromatic–aliphatic five- and six-membered thermotropic polyimides

Polymers have been prepared by the polycondensation of 4,4′-(butane-1,4-diylbis(oxy)) bis(butane-4,1-diyl) bis(4-aminobenzoate) and 5,10,15,20,25,30,35,40,45,50,55,60-dodecaoxatetrahexacontane-1,64-diyl bis(4-aminobenzoate) (PBBA 1200) with three dianhydrides based on naphthalene, perylene and phthalic moieties, respectively. This has resulted in five novel aliphatic–aromatic polyimides. The polyimides differed in aliphatic chain length and whether the imide ring was five- or six-membered. The chemical structure of the polyimides has been confirmed by ¹H NMR and FTIR spectroscopy and by elemental analysis. The optical and electrical properties of the polyimides have been studied using current–voltage measurements, and the effect of the polyimide structure on thermal and mesomorphic behaviour investigated by differential scanning calorimetry and polarising optical microscopy. Wide-angle X-ray diffraction at different temperatures was employed to confirm the structural properties of the polyimides. All the novel polyimides, with the sole exception of that obtained from PBBA1200 and 3,4,9,10-perylenetetracarboxylic dianhydride, showed liquid crystalline properties. As far as we are aware, this is the first time that six-membered polyimides exhibiting liquid crystalline properties have been reported.     

The Chemical Composition of Oils and Cakes of Ochna serrulata (Ochnaceae) and Other Underutilized Traditional Oil Trees from Western Zambia

Currently, the negative effects of unified and intensive agriculture are of growing concern. To mitigate them, the possibilities of using local but nowadays underused crop for food production should be more thoroughly investigated and promoted. The soybean is the major crop cultivated for vegetable oil production in Zambia, while the oil production from local oil-bearing plants is neglected. The chemical composition of oils and cakes of a three traditional oil plant used by descendants of the Lozi people for cooking were investigated. Parinari curatellifolia and Schinziophyton rautanenii oils were chiefly composed of α-eleostearic (28.58–55.96%), linoleic (9.78–40.18%), and oleic acid (15.26–24.07%), whereas Ochna serrulata contained mainly palmitic (35.62–37.31%), oleic (37.31–46.80%), and linoleic acid (10.61–18.66%); the oil yield was high (39–71%). S. rautanenii and O. serrulata oils were rich in γ-tocopherol (3236.18 μg/g, 361.11 μg/g, respectively). The O. serrulata oil also had a very distinctive aroma predominantly composed of p-cymene (52.26%), m-xylene (9.63%), γ-terpinene (9.07%), o-xylene (7.97), and limonene (7.23%). The cakes remaining after oil extraction are a good source of essential minerals, being rich in N, P, S, K, Ca, and Mg. These plants have the potential to be introduced for use in the food, technical, or pharmaceutical industries.     

Temperature investigations of E/Z isomers in ketimines based of p-dibenzoylobenzene with aniline and 2,6-dimethylaniline by infrared spectroscopy

The reaction of aniline with p-dibenzoylobenzene (K1) can lead to Z/Z, Z/E and E/E isomers however the only Z/Z and E/E were formed. At room temperature these isomers may be separated, thus the corresponding FTIR spectra could be recorded. The observed bands were assigned and temperature investigations were lead to monitor the structural changes during heating Z and E forms of K1 from 20 to 240 degrees C. FTIR spectroscopy showed that the bigger changes of the Z form was observed with an increase of temperature. Similar experience was lead with the ketimine synthesized from 2,6-dimethylaniline and p-dibenzoylobenzene (K2) investigated as a mixture of isomers.     

Selection of new chromogenic substrates of serine proteinases using combinatorial chemistry methods

Chemical synthesis, physicochemical characterization and kinetic investigations of a tetrapeptide library of chromogenic substrates containing the amide of 5-amino-2-nitrobenzoic acid (Anb(5,2)-NH(2)) at their C-termini are reported. Anb(5,2)-NH(2) served as a chromophore released upon enzymatic action. The library consisting of 9567 peptides was synthesized using the portioning-mixing method and was screened against bovine a-chymotrypsin and human leukocyte elastase in solution applying an iterative approach. The selected chromogenic substrates were resynthesized and further modified at their N- and C-termini. Finally, two sequences, Z-Phe-Ala-Thr-Tyr-Anb(5,2)-NH(2) and Z-Phe-Phe-Pro-Val-Anb(5,2)-NH(2), were obtained as highly specific substrates for bovine alpha-chymotrypsin and human leukocyte elastase, respectively. The method of synthesis and selection of chromogenic substrates of serine proteinases described herein is straightforward and can be applied to design substrates for other proteases.     

Amidoxime polymers - copper complexes

The aminolysis of nitrile groups in macroporous acrylonitrile-divinylbenzene copolymers leads to amphoteric ion exchange resins with 1.0 - 3.3 mmol/g amidoxime groups content. The starting copolymers were synthesized from the same monomer mixture, but the composition of diluents used were different. The resulting polymers with amidoxime groups have different sorption of Cu(II) ions, the highest values between 1.3 and 3.5 mmol/g at pH 5. EPR and IR spectra were used to indicate the formation of the complexes between Cu(II) ions and amidoxime polymers. On the basis of the EPR parameters structure of complexes formed at different pH and Cu(II) concentration was postulated.     

Steroidal glycosides from Veronica chamaedrys L. Part I. The structures of chamaedrosides C, C1, C2, E, E1 and E2

Two new spirostane glycosides, chamaedrosides C (1) and C1 (2), two new furostane glycosides, chamaedrosides E (4) and E1 (5), and two new furospirostane glycosides, chamaedrosides C2 (3) and E2 (6), have been isolated from Veronica chamaedrys L. plants. Their structures were determined on the basis of chemical evidence and extensive spectroscopic methods, including 1D- and 2D-NMR experiments, as well as MS analysis. The given compounds have been found for the first time.     

Multiscale analysis of water uptake and erosion in biodegradable polyarylates

The role of hydration in degradation and erosion of materials, especially biomaterials used in scaffolds and implants, was investigated by studying the distribution of water at length scales from 0.1 nm to 0.1 mm using Raman spectroscopy, small-angle neutron scattering (SANS), Raman confocal imaging, and scanning electron microscopy (SEM). The measurements were demonstrated using l-tyrosine derived polyarylates. Bound- and free- water were characterized using their respective signatures in the Raman spectra. In the presence of deuterium oxide (D₂O), H-D exchange occurred at the amide carbonyl but was not detected at the ester carbonyl. Water appeared to be present in the polymer even in regions where there was little evidence for NH to ND exchange. SANS showed that water is not uniformly dispersed in the polymer matrix. The distribution of water can be described as mass fractals in polymers with low water content (∼5 wt%), and surface fractals in polymers with larger water content (15-60 wt%). These fluctuations in the density of water distribution are presumed to be the precursors of the ∼20 μm water pockets seen by Raman confocal imaging, and also give rise to the 10-50 μm porous network seen in SEM. The surfaces of these polymers appeared to resist erosion while the core of the films continued to erode to form a porous structure. This could be due to differences in either the density of the polymer or the solvent environment in the bulk vs. the surface, or a combination of these two factors. There was no correlation between the rate of degradation and the amount of water uptake in these polymers, and this suggests that it is the bound water and not the total amount of water that contributes to hydrolytic degradation.     

Measurement of bisphenol A, bisphenol A ß-D-glucuronide, genistein, and genistein 4'-ß-D-glucuronide via SPE and HPLC-MS/MS

Bisphenol A (BPA) is a synthetic industrial reactant used in the production of polycarbonate plastics, and genistein is a natural phytoestrogen abundant in the soybean. Current studies investigating the endocrine-disrupting effects of concomitant exposures to BPA and genistein have warranted the development of an analytical method for the simultaneous measurement of BPA and genistein, as well as their primary metabolites, bisphenol A ?-d-glucuronide (BPA gluc) and genistein 4′-?-d-glucuronide (genistein gluc), respectively. All four analytes were extracted from rat plasma via solid phase extraction (SPE). Three SPE cartridges and four elution schemes were tested. Plasma extraction using Bond Elut Plexa cartridges with sequential addition of ethyl acetate, methanol, and acetonitrile yielded optimal average recoveries of 98.1 ± 1.8% BPA, 94.9 ± 8.0% genistein, 91.4 ± 6.1% BPA gluc, and 103 ± 6.1% genistein gluc. Identification and quantification of the four analytes were performed by a validated HPLC-MS/MS method using electrospray ionization and selective reaction monitoring. This novel analytical method should be applicable to the measurement of BPA, genistein, BPA gluc, and genistein gluc in urine, cultures, and tissue following in vivo exposures. While reports of the determination of BPA and genistein independently exist, the simultaneous optimized extraction and detection of BPA, genistein, BPA gluc, and genistein gluc have not previously been reported.