ESTABLISHMENT OF ISOMERIC COMPOSITION OF INSECTICIDAL CYPERMETHRIN SUBSTANCE BY RP-HPLC

The determination of cypermethrin, one of the most sought pyrethroid insecticides having a wide range of activities, by isocratic RP-HPLC is considered. The analysis of substances (technical products) with different content of both the geometrical (cis-, trans-) and optical (zetacypermethrin and alfacypermethrin) isomers of cypermethrin was carried out. Information about the content of the most active forms of cis- allows evaluating the effectiveness of the biological substance based only on RP-HPLC data, which in turn can be a decisive factor in the of the substance assessment supplier / manufacturer or ready commercial products. The optimum concentration range for determining the geometric isomers of cypermethrin in the working solution is from 0.2 to 1.0 mg/ml. The substance detection limit in working solutions/washings is 0.005 mg/ml.

A Study on Physical Performance for Poly(L-lactic acid) in Addition to Layered Strontium Phenylphosphonate

The organic-inorganic hybrid layered strontium phenylphosphonate (SrP) was synthesized by using strontium chloride and phenylphosphinic acid. And the influence of layered SrP on the crystallization behavior and thermal stability of poly(L-lactic acid) (PLLA) was investigated through DSC, XRD, and TGA. Both DSC and XRD results demonstrated that layered SrP had the powerful accelerated ability for PLLA crystallization, and in the range of studied concentration, 0.7 wt%–1 wt% is the optimum concentration range to achieve rapid crystallization of PLLA. Meantime, as a result, the increase of cooling rate in nonisothermal crystallization procedure seriously affected the crystallization accelerated efficiency of SrP. Thermal stability measurement showed that layered SrP could cause the onset decomposition temperature of PLLA to decrease, but the thermal decomposition behavior of PLLA hardly depended on the SrP concentration.

Quantum Dots CdSe/ZnS-Loaded Poly(D,L-Lactide-Co-Glycolide) Nanoparticles: Physicochemical Characterization and Application

This paper described and characterized the quantum dots (QDs) with/without the polymeric PLGA applied in MC3T3E-1 delivery. Neat QDs were treated with various solvents, temperatures, exposure time and concentration to evaluate their stability and efficacy. We found that the intensity degree of fluorescence spectra (QDs) in different solvents follows the order: ether > THF > acetone > chloroform > methanol. Importantly, the QDs become inactive after 8-hr dissolution in the solvents of ether, THF or chloroform. According to this result, acetone and methanol are ideal solvents for QDs. The optimum concentration range of QDs in acetone is 5 to 10 mg/mL. We found that no obvious difference of fluorescence intensity was detected in QDs stored respectively at 4 °C, 24 °C and 44 °C (8-hour). When QDs were exposed to UV light (312 nm) for 2 hr, serious decay of fluorescence intensity was observed. In order to extend the application of QDs in medical areas, we encapsulated them in individual biocompatible poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles for in-vitro imaging of endocytosis in MC3T3E-1 cells. We demonstrated that the polymeric PLGA have the ability to permeate the cells for cellular internalization; the endocytotic activity could be enhanced by the polymeric QDs-encapsulated PLGA.

Spectrophotometric Estimation of Cefuroxime and Ceftazidime in Bulk and in Dosage Forms

Three simple, accurate and sensitive spectrophotometric methods (A, B and C) for the determination of cefuroxime and ceftazidime in bulk samples and in dosage forms are described. They are based on the reaction with nitrous acid forming a nitroso derivatives which can be measured at λmax 350 and 355 nm for cefuroxime (I) and ceftazidime (II), respectively (method A) or by oxidation of drug I or II with an excess of freshly prepared hypobromite and the residual hypobromite was treated with sodium fluorescein at the optimum experimental conditions and measured at λmax at 517 nm (method B). Method C is based on the formation of tris (0-phenanthroline) iron(II) complex (ferroin) upon the oxidation of the studied drug I or II with an iron (III)-o-phenanthroline mixture in acetate buffer solution of pH 3.6 and measuring at λmax 509 nm. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 0.2 – 6.0, 0.2 – 3.2 and 0.1 – 5.6 μg ml−1 for methods A, B and C, respectively. The apparent molar absorptivity, Sandell sensitivity, detection and quantitation limits were calculated. For more accurate results, Ringbom optimum concentration range was 0.2 – 5.6 μg ml−1. The validity of the proposed methods was tested by analysing dosage forms containing the studied drugs I and II. The relative standard deviations were ≤ 1.25% with recoveries 98.6 – 101.4% .

A Study on UV Filter Chemicals from Annex VII of European Union Directive 76/768/EEC, in the In Vitro 3T3 NRU Phototoxicity Test

In 1996, the Scientific Committee on Cosmetology of DGXXIV of the European Commission asked the European Centre for the Validation of Alternative Methods to test eight UV filter chemicals from the 1995 edition of Annex VII of Directive 76/768/EEC in a blind trial in the in vitro 3T3 cell neutral red uptake phototoxicity (3T3 NRU PT) test, which had been scientifically validated between 1992 and 1996. Since all the UV filter chemicals on the positive list of EU Directive 76/768/EEC have been shown not to be phototoxic in vivo in humans under use conditions, only negative effects would be expected in the 3T3 NRU PT test. To balance the number of positive and negative chemicals, ten phototoxic and ten non-phototoxic chemicals were tested under blind conditions in four laboratories. Moreover, to assess the optimum concentration range for testing, information was provided on appropriate solvents and on the solubility of the coded chemicals. In this study, the phototoxic potential of test chemicals was evaluated in a prediction model in which either the Photoirritation Factor (PIF) or the Mean Photo Effect (MPE) were determined. The results obtained with both PIF and MPE were highly reproducible in the four laboratories, and the correlation between in vitro and in vivo data was almost perfect. All the phototoxic test chemicals provided a positive result at concentrations of 1μg/ml, while nine of the ten non-phototoxic chemicals gave clear negative results, even at the highest test concentrations. One of the UV filter chemicals gave positive results in three of the four laboratories only at concentrations greater than 100μg/ml; the other laboratory correctly identified all 20 of the test chemicals. An analysis of the impact that exposure concentrations had on the performance of the test revealed that the optimum concentration range in the 3T3 NRU PT test for determining the phototoxic potential of chemicals is between 0.1μg/ml and 10μg/ml, and that false positive results can be obtained at concentrations greater than 100μg/ml. Therefore, the positive results obtained with some of the UV filter chemicals only at concentrations greater than 100μg/ml do not indicate a phototoxic potential in vivo. When this information was taken into account during calculation of the overall predictivity of the 3T3 NRU PT test in the present study, an almost perfect correlation of in vitro versus in vivo results was obtained (between 95% and 100%), when either PIF or MPE were used to predict the phototoxic potential. The management team and participants therefore conclude that the 3T3 NRU PT test is a valid test for correctly assessing the phototoxic potential of UV filter chemicals, if the defined concentration limits are taken into account.

An immobilized-enzyme flow-enthalpimetric analyzer: application to glucose determination by direct phosphorylation catalyzed by hexokinase.

A novel flow-enthalpimetric analyzer is described and its use demonstrated by an analysis in which glucose is determined by its hexokinase-catalyzed phosphorylation reaction. The method depends on measurement of the temperature differential across a column packed with glass-supported immoblized enzyme. Sample volumes of 120 mul can be used to obtain a calibration curve that is linear up to 25 mmol of glucose per liter. A precision (within-day) of 5% is generally observed in the optimum concentration range where glucose is quantitatively phosphorylated. Results by the technique correlate reasonably with those by the o-toluidine and the hexokinase/glucose-6-phosphate dehydrogenase methods: Other sugars--including fructose, glucosamine, and mannose--will interfere; galactose does not. The technique is amenable to both routine and emergency analyses.

Induction of sporangia in Phytophthora cinnamomi by a substance from bacteria and soil

Production of sporangia of Phytophthora cinnamomi on agar–mycelial disks in a mineral salts solution was induced by extracts of a soil pseudomonad. Acetone extracts of soil and of mixed populations of microorganisms from soil solution also stimulated the formation of these asexual reproductive structures. Active extracts stimulated sporangium production in aqueous dilutions as high as 10−9. Some extracts of the bacterium were less active at dilutions above or below a certain optimum concentration range. The unidentified, active substance was characterized as a nonvolatile, polar, heat-stable compound that is soluble in water and several organic solvents. Salts of Ca, Mg, K, and Fe in the suspending medium favored a limited production of sporangia in the absence of active substance, and abundant sporangia in its presence. Ca2+was essential for maximum response. The substance was detected by bioassay on paper and thin-layer chromatograms, and it was obtained partially purified.

Study of sugars with cysteine – sulfuric acid reagents

A modified procedure for the use of the cysteine – sulfuric acid reagent for the determination of monosaccharide has been devised. The procedure utilizes a 9-ml volume of H2O:H2SO4 at a ratio of 1:7 which results in a rapid nonspecific method for the determination of pentoses, hexoses, and hexuronic acids in simple solutions. α-Substituted cysteines are compared to cysteine hydrochloride as color reagents. The accuracy of the modified procedure is about ± 2% in the optimum concentration range. The time required for a complete analysis is about 1 h for pentoses and hexuronic acids and 30 min for hexoses.