Chirality groups of maps and hypermaps

Although the phenomenon of chirality appears in many investigations of maps and hypermaps, no detailed study of chirality seems to have been carried out. Chirality of maps and hypermaps is not merely a binary invariant but can be quantified by two new invariants—the chirality group and the chirality index, the latter being the size of the chirality group. A detailed investigation of the chirality groups of orientably regular maps and hypermaps will be the main objective of this paper. The most extreme type of chirality arises when the chirality group coincides with the monodromy group. Such hypermaps are called totally chiral. Examples of these are constructed by considering appropriate “asymmetric” pairs of generators of certain non-abelian simple groups. We also show that every finite abelian group is the chirality group of some hypermap, whereas many non-abelian groups, including symmetric and dihedral groups, cannot arise as chirality groups. M. Škoviera supported in part by APVT grant 51-027604 and by VEGA grant 1/3022/06.     

Incidence of Fusarium Mycotoxins in Wheat and Maize from Albania

In this study, ten Fusarium toxins were analysed in wheat and maize commodities from Albania. In total, 71 samples of wheat and 45 samples of maize were collected from different producing regions. The analytical procedure consisted of a simple one-step sample extraction followed by the determination of toxins using liquid chromatography coupled with tandem mass spectrometry. Fusarium toxins were found in 23% of the analysed wheat samples and in 78% of maize samples. In maize samples, most often fumonisins B₁ (FB1) and B₂ (FB2) were found. They were present in 76% of samples. They were detected in all positive samples except in one with concentrations ranging from 59.9 to 16,970 μg/kg. The sum of FB1 and FB2 exceeded the EU maximum permitted level (4000 μg/kg) in 31% of maize samples. In wheat samples, the only detected Fusarium mycotoxin was deoxynivalenol (DON), present in 23% of samples. In one sample with the concentration of 1916 μg/kg, the EU maximum permitted level (1250 μg/kg) was exceeded. This is the first report on the presence of Fusarium toxins in wheat and maize grains cultivated in Albania.     

Determination of three major triterpenoids in epicuticular wax of cabbage (Brassica oleracea L.) by high-performance liquid chromatography with UV and mass spectrometric detection

Lupeol, together with alpha- and beta-amyrins in smaller quantities, has been found for the first time in the epicuticular wax of white cabbage (Brassica oleracea L. convar. capitata (L.) Alef. var. alba DC) leaf surface extract. The three triterpenoids were identified by a new high-performance liquid chromatographic (HPLC) method with UV and mass spectrometric (MS) detection using atmospheric pressure chemical ionization (APCI). All three isomeric compounds gave a parent ion peak at m/z 409 [M+H-18](+) and the relative intensities of some characteristic fragment ion peaks in tandem mass spectrometric (MS-MS) spectra of this parent ion enabled differentiation between the isomers. An additional peak at m/z 439 [M+H](+), which could be oleanonic or ursonic aldehyde, was detected by HPLC-APCI-MS. Saponification of cabbage leaf surface extract with 20% NaOH in methanol at 65 degrees C for 2h had no influence on lupeol, or alpha- or beta-amyrins, but lead to the formation of three additional compounds, which were not identified.     

Separation of eight selected flavan-3-ols on cellulose thin-layer chromatographic plates

The potential of microcristaline cellulose as sorbent in the separation of eight compounds: (+)-catechin (C), (-)-epicatechin (EC), (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), (-)-epigallocatechin gallate (EGCg), procyanidin B1 and procyanidin B2 was studied. Cellulose HPTLC plates prewashed in water (not necessary, when water was used as developing solvent) and dried with a hair dryer, bandwise application and development in horizontal developing chamber (sandwich configuration) gave the best results. Detection was performed using vanillin-H3PO4 reagent. Four new developing solvent systems were proposed: water, 1-propanol-water (20:80, v/v), 1-propanol-water-acetic acid (4:2:1, v/v) and 1-propanol-water-acetic acid (20:80:1, v/v), and at least two of them were needed for the differentiation between all eight compounds. Surprisingly, water enabled the separation of epimers C from EC and GC from EGC, as well as the dimers procianidin B1 and B2. Additionally, C, EGC, B1 and B2 were separated from all the other compounds. The best choice for developing solvent is given for each of the studied compounds. The best separation of the five main catechins (EC, GC, EGC, ECg, EGCg) present in green tea extract was achieved using 1-propanol-water-acetic acid (20:80:1, v/v). The chromatograms of oak bark extract developed in solvents with higher water content (1-propanol-water (1:4, v/v) and 1-propanol-water-acetic acid (20:80:1, v/v)) showed less bands than chromatograms developed in solvents with higher organic modifier content (e.g. 1-propanol-water-acetic acid (4:2:1, v/v)). It was proved that such behavior was due to the presence of procyanidins beside the main component catechin.     

On chirality groups and regular coverings of regular oriented hypermaps

We prove that if the Walsh bipartite map M = W (ℋ) of a regular oriented hypermap ℋ is also orientably regular then both M and ℋ have the same chirality group, the covering core of M (the smallest regular map covering M) is the Walsh bipartite map of the covering core of ℋ and the closure cover of M (the greatest regular map covered by M) is the Walsh bipartite map of the closure cover of ℋ. We apply these results to the family of toroidal chiral hypermaps (3, 3, 3) _b,c = W ⁻¹{6, 3} _b,c induced by the family of toroidal bipartite maps {6, 3} _b,c .     

Allergen microarrays on high-sensitivity silicon slides

We have recently introduced a silicon substrate for high-sensitivity microarrays, coated with a functional polymer named copoly(DMA-NAS-MAPS). The silicon dioxide thickness has been optimized to produce a fluorescence intensification due to the optical constructive interference between the incident and reflected lights of the fluorescent radiation. The polymeric coating efficiently suppresses aspecific interaction, making the low background a distinctive feature of these slides. Here, we used the new silicon microarray substrate for allergy diagnosis, in the detection of specific IgE in serum samples of subjects with sensitizations to inhalant allergens. We compared the performance of silicon versus glass substrates. Reproducibility data were measured. Moreover, receiver-operating characteristic (ROC) curves were plotted to discriminate between the allergy and no allergy status in 30 well-characterized serum samples. We found that reproducibility of the microarray on glass supports was not different from available data on allergen arrays, whereas the reproducibility on the silicon substrate was consistently better than on glass. Moreover, silicon significantly enhanced the performance of the allergen microarray as compared to glass in accurately identifying allergic patients spanning a wide range of specific IgE titers to the considered allergens.     

Development and validation of a high-performance thin-layer chromatographic method for determination of ofloxacin residues on pharmaceutical equipment surfaces

An HPTLC method with densitometric quantification using fluorescence at 313 nm was developed and validated for the determination of ofloxacin residue in controlling pharmaceutical equipment cleanliness. Simulated samples at a residue level of 1 mg/m2 were prepared by spreading the calculated amount of ofloxacin solution on 1, 5, and 10 dm2 stainless steel surfaces. After evaporation of the solvent, the residue was removed by two ethanol wetted cotton swabs, which were thereafter extracted with the mixture of ethanol and Na2EDTA-water solution at pH 11 for 15 min with sonication. The extract and standards were applied on HPTLC silica gel 60 plates and then developed in a horizontal developing chamber from both sides using ethanol-conc. ammonia (4+1, v/v) as the mobile phase. The mean recovery (n=6) at 1 mg/m2 from 1, 5, and 10 dm2 was 95.3, 88.6, and 89.7% with the CV values 3.78, 4.41, and 4.97%, respectively. The absolute detection limit was 0.6 ng and the quantitation limit was 2 ng, but it was shown that these can be improved by immersion of the developed plate into a solution of liquid paraffin-n-hexane (1+2, v/v) to approximately 0.25 and 0.9 ng, respectively. The LOD of the method using detection without paraffin-n-hexane was 3, 0.6, and 0.3 microg/m2 by swabbing 1, 5, and 10 dm2, respectively. The method can be applied to routine control of pharmaceutical equipment cleanliness by sampling from stainless steel surface areas of 1 to 10 dm2 with acceptable residue limit/surface of 1 mg/m2.     

Determination of risperidone and 9‐Hydroxyrisperidone using HPLC,in plasma of children and adolescents with emotional and behavioural disorders

A simple, rapid, selective, accurate and precise method is described for the determination of risperidone and its active metabolite, 9‐hydroxyrisperidone, in plasma using a chemical derivative of risperidone (methyl‐risperidone) as the internal standard. The sample workup involved a single‐step extraction of 1 mL plasma, buffered to pH 10, with heptane–isoamyl alcohol (98:2 v/v), then evaporation of the heptane phase and reconstitution of the residue in mobile phase. HPLC separation was carried out at on C₁₈ column using a mobile phase of 0.05 m dipotassium hydrogen orthophosphate (containing 0.3% v/v triethylamine) adjusted to pH 3.7 with orthophosphoric acid (700 mL), and acetonitrile (300 mL). Flow rate was 0.6 mL/min and the detection wavelength was 280 nm. Retention times were 2.6, 3.7 and 5.8 min for 9‐hydroxy risperidone, risperidone and the internal standard, respectively. Linearity in spiked plasma was demonstrated from 2 to 100 ng/mL for both risperidone and 9‐hydroxyrisperidone (r ≥ 0.999). Total imprecision was less than 13% (determined as co‐efficient of variation) and the inaccuracy was less than 12% at spiked concentrations of 5 and 80 ng/mL. The limit of detection, determined as three times the baseline noise, was 1.5 ng/mL. Clinical application of the assay was demonstrated for analysis of post‐dose (0.55–4.0 mg/day) samples from 28 paediatric patients (aged 6.9–17.9 years) who were taking risperidone orally for behavioural and emotional disorders. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of sucrose esters--insecticides from the surface of tobacco plant leaves

Sucrose esters from the surface of leaves of Nicotiana tabacum L. have been shown to possess interesting biological activities. We developed a simple and effective method for their analysis using HPTLC silica gel plates, n-hexane-ethyl acetate (1:3, v/v) as developing solvent and aniline-diphenylamine as a detection reagent. Off-line TLC-MS was also used for the detection and identification of the compounds. Solutions containing sucrose esters upon alkaline hydrolysis give sucrose, which is used for indirect estimation by TLC of the sucrose ester content. The method is applicable for the screening for sucrose esters in plant extracts. The extract obtained from the surface of green leaves of oriental tobacco type Prilep P-23 contains sucrose esters and is effective against Myzus persicae (Sulzer) in laboratory and field experiments.