Preparation of Collagen‐Glycosaminoglycan Sponges with Open Surface Porous Structures Using Ice Particulate Template Method

Funnel‐like sponges of collagen incorporated with glycosaminoglycan (GAG) were prepared by freeze‐drying using ice particulates as templates. The funnel‐like collagen‐GAG sponges showed similar porous structures to those of funnel‐like collagen sponges. The funnel‐like collagen‐GAG and collagen sponges have one top surface layer and one bulk porous layer. The large, top surface pores were determined by ice particulates that were used as templates, and the inner bulk pores were determined by freezing temperature. The funnel‐like pore structures facilitated homogenous cell distribution, improved cell viability, and resulted in homogenous tissue formation. Incorporation of GAG increased the mechanical property and cell viability of collagen sponges.

     

Renewable agricultural fibers as reinforcing fillers in plastics

Thermal properties such as melting and crystallization are important aspects in understanding the morphology and its contribution to the physical properties of semicrystalline polymers, such as polypropylene. The inclusion of fillers, which are small particles dispersed in the continuous polymer phase, often complicates the predictability of these properties by acting as nucleating agents or defect origins. This paper discusses the creation and use of empirical models based on experimental data for predicting and optimizing the thermal properties of agricultural filler-polypropylene (AgFiller-PP) composites, including peak melting temperature (T _m), peak crystallization temperature (T _c) and percent of crystallinity (X _c). Experiments were performed using differential scanning calorimetry (DSC) to gather data necessary for building appropriate prediction models. Finally, additional experiments were carried out to test the prediction results generated by the models.     

Determination of metals, metalloids and non-volatile ions in airborne particulate matter by a new two-step sequential leaching procedure Part A: Experimental design and optimisation

The optimisation of a micro-analytical two-step sequential leaching procedure for the determination of non-volatile ions (NO₃⁻, SO₄²⁻, Cl⁻, Na⁺, Mg²⁺, NH₄⁺ and Ca²⁺) and of 17 elements (Al, As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, S, Se, V, Zn, Sb, Si and Ti) in two fractions—extract and residue—on the same sample of air particulate matter is described. The two-step method was tested on the SRM NIST 1648 for equivalence with two reference methods, the EMEP procedure for ions extraction and the EN 12341 standard for the elemental determination of the PM₁₀ and is suitable for application to small sample amounts (less than 1 mg of particulate matter is needed), i.e. those collected by daily low volume filter-sampling. Performance times of the procedure were optimised to meet the target of routine application for large scale monitoring samples. A single ultrasonic-assisted extraction of air particulate matter is performed in 0.01 M acetate buffer at pH 4.5, followed by IC ions analysis and ICP-OES elemental analysis of the extract and by ICP-OES elemental analysis of the mineralized residue after dissolution by microwave-assisted digestion with a HNO₃/H₂O₂ mixture. Using a pH buffered extracting solvent was preferred to water or diluted acid solutions to improve the reproducibility of metals extraction with respect to existing leaching methods; the influence of pH, nature and concentration of the buffer solution and extraction time on analytes concentration in the extract is discussed. Values of ions extraction and elements recoveries resulted fairly equivalent with those obtained by the reference methods. The study was also extended to some non-certified elements (Mg, S, Sb, Si and Ti) for their environmental significance. Elements recoveries were obtained as sum of the extract and residue fractions and were comparable with those obtained by direct dissolution. Standard deviations were within 10% for almost all detected ions and elements.     

Development of an analytical approach for determination of total arsenic and arsenic (III) in airborne particulate matter by slurry sampling and HG-FAAS

Slurry sampling (SS) with hydride generation atomic absorption spectrometry (HG-AAS) was used to analyze 3 particulate matter samples collected in the Bananeira Village, Brazil, in 2005. The relative standard deviation (RSD), used to assess the precision, was lower than 4.8%. The accuracy of this method was confirmed by the analysis of certified atmospheric particulate matter urban dust reference material SRM 1649a. This method (SS/HG-AAS) was used to determine total arsenic and arsenic (III) in three particulate matter samples. In these samples, the total arsenic concentrations varied from 3.8 to 20.0 ng m^− 3, while As (III) concentrations varied from 2.7 to 10.5 ng m^− 3. All samples were also analyzed using acid digestion in digest block with cold finger and detection for HG-AAS. A paired t-test demonstrated no significant difference (95% CL) between the results obtained using these two sample preparation procedures. The limit of quantification, calculated considering the mass of particulate matter collected on every filter, was 0.6 ng m^− 3 for As total and 1.0 ng m^− 3 for As (III).     

Determination of Pb in airborne particulate matter with a heavy matrix of silicon by SR-ETAAS

A study is undertaken to monitor Pb levels in airborne particulate matter collected on ash-free glass-fibre filters from urban and industrial areas of Argentina by electrothermal atomic absorption spectrometry with self-reversal background correction. For this sample with a heavy matrix of silicon, a simple acid treatment with aqua regia and HF is proposed aimed to minimize contamination and reduce sample treatment steps. Ultrasonic agitation was employed for sample homogenization. To overcome the problem of the high amounts of Si, main analytical variables including acid pretreatment conditions, temperature program of the graphite furnace and spectroscopic conditions were carefully studied and optimized. Continuum source and self-reversal methods for background correction were compared in order to avoid non-specific and spectral interferences due to the matrix. After optimization, synthetic acid solutions of Pb were employed for calibration. Calibration was linear within the range 1–40 µg L^{− 1} (correlation coefficient of 0.9995) when the 283.3 analytical line was used. Using optimized conditions limits of detection (3σ) of 0.6 µg L^{− 1} were achieved. The repeatability between injections (S_r%) was evaluated and was better than 4.2%. The precision (%RSD) for Pb determination in a single sample was estimated by analyzing three strips of the same filter. In all cases the RSD was better than 6.9%. For checking accuracy, an aliquot of a Standard Reference Material (NIST 2709, San Joaquin Soil) was subject to the same sample treatment and included in the overall analytical process. This method was successfully applied to the determination of Pb in airborne particulate matter collected in Buenos Aires city.     

Development and validation of a high‐performance liquid chromatography method for the simultaneous determination of aspirin and folic acid from nano‐particulate systems

Attention has shifted from the treatment of colorectal cancer (CRC) to chemoprevention using aspirin and folic acid as agents capable of preventing the onset of colon cancer. However, no sensitive analytical method exists to simultaneously quantify the two drugs when released from polymer‐based nanoparticles. Thus, a rapid, highly sensitive method of high‐performance liquid chromatography analysis to simultaneously detect low quantities of aspirin (hydrolyzed to salicylic acid, the active moiety) and folic acid released from biodegradable polylactide‐co‐glycolide (PLGA) copolymer nanoparticles was developed. Analysis was done on a reversed‐phase C₁₈ column using a photodiode array detector at wavelengths of 233 nm (salicylic acid) and 277 nm (folic acid). The mobile phase consisted of acetonitrile–0.1% trifluoroacetic acid mixture programmed for a 30 min gradient elution analysis. In the range of 0.1–100 μg/mL, the assay showed good linearity for salicylic acid (R² = 0.9996) and folic acid (R² = 0.9998). The method demonstrated good reproducibility, intra‐ and inter‐day precision and accuracy (99.67, 100.1%) and low values of detection (0.03, 0.01 μg/mL) and quantitation (0.1 and 0.05 μg/mL) for salicylic acid and folic acid, respectively. The suitability of the method was demonstrated by simultaneously determining salicylic acid and folic acid released from PLGA nanoparticles. Copyright © 2009 John Wiley & Sons, Ltd.     

A study of uniformity of elements deposition on glass fiber filters after collection of airborne particulate matter (PM-10), using a high-volume sampler

A study was conducted to evaluate the homogeneity of the distribution of metals and metalloids deposited on glass fiber filters collected using a high-volume sampler equipped with a PM-10 sampling head. The airborne particulate matter (APM)-loaded glass fiber filters (with an active surface of about 500 cm²) were weighed and then each filter was cut in five small discs of 6.5 cm of diameter. Each disk was mineralized by acid-assisted microwave (MW) digestion using a mixture of nitric, perchloric and hydrofluoric acids. Analysis was performed by axial view inductively coupled plasma optical emission spectrometry (ICP OES) and the elements considered were: Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Ti and V. The validation of the procedure was performed by the analysis of the standard reference material NIST 1648, urban particulate matter. As a way of comparing the possible variability in trace elements distribution in a particular filter, the mean concentration for each element over the five positions (discs) was calculated and each element concentration was normalized to this mean value. Scatter plots of the normalized concentrations were examined for all elements and all sub-samples. We considered that an element was homogeneously distributed if its normalized concentrations in the 45 sub-samples were within ±15% of the mean value ranging between 0.85 and 1.15. The study demonstrated that the 12 elements tested showed different distribution pattern. Aluminium, Cu and V showed the most homogeneous pattern while Cd and Ni exhibited the largest departures from the mean value in 13 out of the 45 discs analyzed. No preferential deposition was noticed in any sub-sample.     

Evaluation of the acetate buffer attack of a sequential extraction scheme for marine particulate metal speciation studies by scanning electron microscopy with energy dispersive X-ray analysis

Scanning electron microscopy, with energy dispersive X-ray analysis (SEM-EDX), has been used to evaluate and possibly optimize, the first step (acetate buffer attack for exchangeable and carbonatic fractions) of a sequential selective extraction scheme. The extraction has been performed on two different particulates, a certified reference plankton and a real marine suspended particulate, using an increased acetate concentration and various solid/extractant ratios. SEM-EDX has been performed on the non treated particulates and on the residues after the attack, and the results related to the spectroscopic analyses of the extracts, allowed us to verify that even if efficiency has been optimized, the procedure still suffers of a lack of selectivity. Nevertheless, SEM data were helpful to put forward some interesting speciation hypothesis, that would have been certainly different, and probably wrong, if based on analyses of the extracts only.     

Detection of PAH of molecular weight between 300 and 402 in airborne particulate matter by fused silica capillary GC and GC/MS

Gas chromatography (GC), low-voltage mass spectrometry (LV MS), and gas chromatography/mass spectrometry (GC/MS) have been used for detecting polycyclic aromatic hydrocarbons (PAH) of molecular weight between 300 and 402 in airborne particulate matter. Nearly 200 high molecular PAH separated by fused silica capillary columns could be characterized by their El mass spectra. The lack of reference substances precluded further structure elucidation.     

Synthesis of Hydrophilic and Hydrophobic High Surface Area Xerogels at pHs Below Silica Iso-electric Point

The synthesis of hydrophilic and hydrophobic high surface area (up to 1087 m²/cc) silica xerogels at pHs below 2 is demonstrated in this work. High surface area xerogels exhibit extremely fine microstructural features and fast gelation times (less than one hour). Contrary to conventional generalization that xerogels synthesized at low pH are polymeric, it is demonstrated that particulate xerogels can also be synthesized at pHs below 2. These xerogels are synthesized by the addition of large amounts of NH₄OH and have relatively lower surface areas. The particulate nature of these xerogels is indicated by their opacity and from their coarse microstructural features as observed by TEM.