Millbrook, United Kingdom
Millbrook, United Kingdom

Time filter

Source Type

Quintana R.,Materia Nova | Quintana R.,University of Mons | Quintana R.,Institute of Materials Research and Engineering of Singapore | Persenaire O.,Materia Nova | And 8 more authors.
Polymer Degradation and Stability | Year: 2013

Cellulose acetate (CA) with a degree of substitution (DS) of 2.5 has been plasticized using eco-friendly plasticizers such as triacetin, tripropionin, triethyl citrate, tributyl citrate, tributyl 2-acetyl citrate and poly(ethylene glycol) of low molecular weight. Thermo-mechanical properties and hydrophilicity of the modified CA have been measured and correlated with the content and nature of the plasticizer used and compared with unplasticized CA. The increase in toughening and the change in the hydrophilicity by the plasticization were evaluated in terms of aging and weathering stability under accelerated conditions. Samples were exposed to UV-degradation with water spray periods. The treated samples were removed periodically and characterized by several analytical techniques. The results are discussed with particular emphasis toward the effects of plasticization on enhancement of the degradation rate of CA. The plasticization of CA triggered an increase of the weight loss between 50 and 90%, where low molecular weight plasticizers were shown to be more effective. A right balance between hydrophilicity and plasticization efficiency (reduction of Tg) is needed to increase the degradation rate of CA. © 2013 Elsevier Ltd. All rights reserved.


Taebunpakul S.,LCG Group | Taebunpakul S.,Imperial College London | Liu C.,Group Randnter | Wright C.,Group Randnter | And 4 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2011

The efficiency of a sequential extraction procedure (leaching with water followed by extraction with driselase and sodium dodecylsulfate) was investigated for quantitative As speciation in cut tobacco by HPLC-ICP-MS. The total As concentration and size-exclusion HPLC-ICP-MS profiles obtained for the extracts were used to select optimal extraction conditions as a trade-off between As extraction efficiency and preservation of compound identity. Leaching the cut tobacco (taken from 3R4F Kentucky research reference cigarettes) with water by either sonication in a water bath for 2 h or microwave-assisted extraction (MAE) at 50 W (50 °C) for only 10 min enabled approximately 42% of the total As in the solid to be extracted. Using anion-exchange HPLC with ICP-MS detection, 89% of the total water-soluble As was, for the first time, reported to be present as inorganic As. The instrumental limits of detection (3σ criterion) obtained for arsenite and arsenate by anion-exchange HPLC-ICP-MS were 10 and 50 ng kg-1 As, respectively. Using this hyphenated method, the presence of DMA and MMA as minor As species in the water-soluble fraction could also be detected. Complementary cation-exchange HPLC-ICP-MS analysis of unspiked extracts and extracts spiked with As standards pointed to the presence of arsenate (as a major As species) and DMA and MMA (as a minor As species). Interestingly, recent XANES results revealed that the cut tobacco contained almost exclusively As(v). Successive extractions with driselase and sodium dodecylsulfate (SDS) on the solid residue led to further extraction of approximately 13% and 8%, respectively, of As from the solid cut tobacco. The total As concentration in a homogenate of cut tobacco (from 3R4F Kentucky reference cigarettes) was found to be 318 ± 9 ng g-1 As (precision as SD, n = 3), as determined by microwave acid digestion followed by collision reaction cell ICP-MS (He mode) with standard addition calibration. The developed hyphenated MS methodology was used to study the speciation of As in water-soluble extracts of 3R4F mainstream smoke. These extracts were, for the first time, found to contain arsenite (As(iii)), arsenate (As(v)) and an unidentified As-containing species. XANES analysis also reported a mixture of As(v) and As(iii) in mainstream cigarette smoke condensate. The reduction of As(v) to As(iii) during dynamic cigarette smoke formation can be explained by the overall smoke redox properties associated with the cigarette combustion process. © 2011 The Royal Society of Chemistry.


Cuello S.,LCG Group | Entwisle J.,LCG Group | Benning J.,Group Randnter | Liu C.,Group Randnter | And 4 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2016

Speciation data for chromium in tobacco products, as obtained by complementary HPLC-ICP-MS and synchrotron-based X-ray Absorption Near-Edge Structure spectroscopy (XANES), are presented for the first time. Non-denaturing extraction conditions were investigated to avoid Cr species redox inter-conversion before analysis of extracts using HPLC-ICP-MS. Methodology based on HPLC-ICP-MS, which is compatible with the extraction conditions, was developed for separation and detection of inorganic Cr species such as Cr(iii) and Cr(vi) in aqueous standard solutions. The instrumental limits of detection (3σ criterion) obtained for Cr(iii) and Cr(vi) were 0.12 and 0.08 ng g-1 Cr, respectively. The total Cr extracted from 3R4F cut tobacco with water was around 10% of the total Cr in the solid (1949 ± 171 ng g-1 of Cr on a dry weight basis), with 75% of the aqueous Cr associated with species of molecular mass > 3 kDa. Cr(iii) was the main identified species in the tobacco extracts using HPLC-ICP-MS, whilst Cr(vi) could not be detected. In situ XANES analysis revealed that the cut tobacco from 3R4F reference cigarettes contained only Cr(iii). Following leaching with water, leaching with sodium dodecylsulfate (SDS) on the solid residue led to extraction of a further 10% of the Cr contained in the solid tobacco. The total Cr data obtained by ICP-MS for HNO3 and HNO3/HF acid digests of 3R4F cut tobacco suggested that additional 12% of the total Cr in the solid appears to be associated with silicates, which are known to occur naturally in tobacco products. Although Cr species could not be detected in water leachates from 3R4F smoke condensates using the HPLC-ICP-MS method developed here, XANES measurements identified Cr(iii) as the main Cr species present in cigarette smoke condensate, with no detectable Cr(vi). HPLC-ICP-MS data obtained for smoke condensates from cigarettes spiked with Cr(iii) before smoke collection revealed that Cr(iii) is the main Cr species in present the water soluble fraction of the condensate. Spiking experiments demonstrated that Cr(vi) was highly unstable in trapped smoke condensate. In this work no evidence was observed for the presence of Cr(vi) in mainstream smoke generated from 3R4F cigarettes. © The Royal Society of Chemistry 2016.

Loading Group Randnter collaborators
Loading Group Randnter collaborators