A rapid High Performance Liquid Chromatographic (HPLC) method for the simultaneous determination of seven UV filters found in sunscreen and cosmetics

A rapid High Performance Liquid Chromatographic (HPLC) method was developed for the simultaneous determination of seven Ultra Violet (UV) filters most commonly found in cosmetics and sunscreen. The object of the method development was to provide a reliable rapid method, that would simultaneously separate a combination of the UV Filters, most commonly found in cosmetics and sunscreen products, utilizing a minimum of environmentally friendly solvents. The compounds separated were: benzophenone 3 (BZ3), methylbenzildene camphor (MBC), octyl dimethyl PABA (ODP), octocrylene (OCR), octyl methoxycinnamate (OMC), butyl – methoxydibenzoylmethane (BDM) and octyl salicylate (OS). An adjusted mobile phase consisting of ethanol and 1% acetic acid, combined with a Thermo Hypersil C₁₈ BDS 3 micron column resulted in a method, which allowed the analysis of the seven compounds in seven minutes. The proposed method was validated utilising the International Congress on Harmonisation (ICH) and the Food and Drug Administration (FDA) guidelines. All parameters examined were found to be well within the stated guidelines.     

Nitric oxide synthase in human placenta and umbilical cord from normal, intrauterine growth-retarded and pre-eclamptic pregnancies

1. It has been suggested that a deficiency of nitric oxide (NO) may explain many of the pathophysiological features of pre-eclampsia (PE) and intra-uterine (foetal) growth retardation (IUGR). To elucidate further the role of NO in the pathophysiology of pregnancy we have determined the relative amount and activity of NO synthase (NOS) in first trimester and normal-term placental tissues, as well as in the placenta and umbilical cord in pregnancies complicated by PE and IUGR, using NG-nitro-L-[2,3,4,5(-3)H]-arginine ([3H]-L-NOARG) binding, quantitative in vitro autoradiography, [3H]-arginine to [3H]-citrulline conversion and Western blotting. 2. Specific, high affinity (KD = 38 nM) [3H]-L-NOARG binding was demonstrated in the villous trophoblast of normal-term placentae. Binding was calcium-independent, stereoselective and exhibited a rank order of inhibition by NOS inhibitors and substrate (L-NOARG > or = L-NMMA > or = 7-NI > L-NAME > L-Arg > or = L-NIO > ADMA). 3. [3H]-L-NOARG binding density and NOS activity were both significantly greater in placental tissues from first trimester and PE or IUGR complicated pregnancies compared to normal-term placentae. 4. Western blotting, using an endothelial NOS peptide antiserum, demonstrated a approximately 140 KDa protein band in placental extracts and indicated that the amount of immunoreactive material was significantly greater in first trimester compared to normal-term placentae. 5. Specific [3H]-L-NOARG binding was also localized to the endothelial lining of umbilical arteries and veins, binding density being greater in the artery than the vein. [3H]-L-NOARG binding to the umbilical artery endothelium was significantly lower in PE and IUGR complicated pregnancies compared to normal-term controls. 6. The role of trophoblast-derived NO in human placental pathophysiology remains to be established, but differences in the amount of placental [3H]-L-NOARG binding, NOS activity and immunoreactive material indicate that expression of NOS in the villous trophoblast falls during pregnancy. Conversely, the apparent reduction in NOS in the umbilical artery endothelium in PE and IUGR complicated pregnancies may be indicative of endothelial dysfunction.     

An analysis of the effects of sample size on classification performance of a histogram based cluster analysis procedure

A non-parametric unsupervised program was developed to identify clusters in multidimensional data by mode analysis using histograms. An implicit assumption in the histogram approach is that a relatively large number of samples is required to insure an accurate classification. Tests with randomly generated data show that the assumption is not true, i.e. a small number of samples does not necessarily result in a poor classification, nor does a relatively large number of samples guarantee the best classification. The histogram classifier was compared to two parametric classifiers, maximum likelihood and K-means clustering. Results from timing the classifiers show that, although the parametric classifiers are more efficient for a small number of samples, the histogram approach uses less CPU time for a large number of samples.     

A method for reproducibly preparing synthetic nanopores for resistive-pulse biosensors

There is increasing interest in using nanopores in synthetic membranes as resistive‐pulse sensors for biomedical analytes. Analytes detected with prototype artificial‐nanopore biosensors include drugs, DNA, proteins, and viruses. This field is, however, currently in its infancy. A key question that must be addressed in order for such sensors to progress from an interesting laboratory experiment to practical devices is: Can the artificial‐nanopore sensing element be reproducibly prepared? We have been evaluating sensors that employ a conically shaped nanopore prepared by the track‐etch method as the sensor element. We describe here a new two‐step pore‐etching procedure that allows for good reproducibility in nanopore fabrication. In addition, we describe a simple mathematical model that allows us to predict the characteristics of the pore produced given the experimental parameters of the two‐step etch. This method and model constitute important steps toward developing practical, real‐world, artificial‐nanopore biosensors.     

Estimation of organic biocide leaching rate using a modified cavity jump diffusion model

Estimation of biocide lifetime in marine antifouling coatings is of great use to improve and develop technologies. An existing model simulating the diffusion of molecules in polymer networks below glass transition temperature was employed to estimate leaching. This model was modified to allow for swelling due to water uptake and to permit evaluation of copolymer binders as well as homopolymers. This enabled prediction of biocide diffusion coefficients in polymeric coatings of various binder types, including pMMA, a pMMA/butylacrylate binder containing rosin, and a trityl copolymer, using usnic acid as a ‘model’ biocide. For comparison with modelling results, coatings fomulated using each binder type were also submitted to static and dynamic seawater immersion. Fluorescence microscopy techniques were used to quantify biocide leaching from these coatings relative to unimmersed coatings. Agreement of the modified diffusion model with experimental data was good for pMMA, reasonable for the rosin-based binder, and poor for the trityl binder. Comparison of predicted and experimental biocide profiles in the binder demonstrated deviation from the expected Fickian mechanism for the pMMA binder, despite the accurate rate prediction. This work demonstrates a first approach to predicting organic biocide diffusion, and highlights the areas for future attention.     

Observations on the Reactivity of Pyrotechnic Compositions containing potassium chlorate and thiourea

An explosion occurred recently during the operation of a grinder that had been used to process potassium chlorate and then thiourea. As part of our investigation of this accident we determined the mechanical sensitiveness of mixtures containing these components and showed that they can be very sensitive to both impact and friction stimuli. Thermo-analytical studies indicate that the binary mixture can react at up to 200°C below the melting point of the oxidizer; the exothermic process is characterized by a high reaction energy. Temperatures of ignition of the mixtures were less than 155°C, whereas the individual components gave no ignition below 400°C.