Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM K55.a, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2009/2010. Eleven national measurement institutes and the BIPM participated. Participants were required to assign the mass fraction of estradiol present as the main component in the comparison sample (CCQM-K55.a) which consisted of a bulk estradiol hemihydrate material obtained from a commercial supplier that had been extensively but not exhaustively dried prior to sub-division into the units supplied for the comparison.Estradiol was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of organic compounds of medium structural complexity [molar mass range 300–500 Da] and low polarity (pKOW < −2) for which related structure impurities can be quantified by capillary gas phase chromatography (GC) or by high performance liquid chromatography (LC).The majority of participants used a mass balance approach to determine the estradiol content. The key comparison reference value (KCRV) for estradiol in CCQM-K55.a was assigned by combination of KCRVs assigned by consensus from participant results for each orthogonal impurity class. This allowed participants to demonstrate the efficacy (or otherwise) of their implementation of the mass balance approach and to demonstrate that their assigned value for the main component agreed with the KCRV through use of internally consistent contributing methods.The KCRV for the estradiol content of the material was 984.3 mg/g with a combined standard uncertainty of 0.42 mg/g. The individual participant results showed that a relative expanded uncertainty for the purity assignment of 0.2% is a reasonable estimate of the best achievable result by an individual laboratory for a material of this complexity available in this amount at this level of purity. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 0.2% to 0.8%.The review of results that were biased from the KCRV showed that two major analytical challenges are posed by the material: the measurement of its water content and controlling for related substance artefact formation during the analysis process. The results displaying a positive bias relative to the KCRV (overestimation of estradiol content) were due to underestimation of the water content of the material, while those with a negative bias (underestimation of estradiol) overestimated the total related substance impurities through a failure to detect and control for artefact formation arising from in situ oxidative dimerization of estradiol in neutral solution prior to analysis. There was however good agreement between all participants in the identification and the quantification of the individual related structure impurities actually present in the sample.The comparison also demonstrated the utility of high-field 1H NMR for both qu...

Under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM) a key comparison, CCQM K55.c, was coordinated by the Bureau International des Poids et Mesures (BIPM) in 2012. Twenty National Measurement Institutes or Designated Institutes and the BIPM participated. Participants were required to assign the mass fraction of valine present as the main component in the comparison sample for CCQM-K55.c. The comparison samples were prepared from analytical grade L-valine purchased from a commercial supplier and used as provided without further treatment or purification.Valine was selected to be representative of the performance of a laboratory's measurement capability for the purity assignment of organic compounds of low structural complexity [molecular weight range 100–300] and high polarity (pKOW > −2).The KCRV for the valine content of the material was 992.0 mg/g with a combined standard uncertainty of 0.3 mg/g. The key comparison reference value (KCRV) was assigned by combination of KCRVs assigned from participant results for each orthogonal impurity class. The relative expanded uncertainties reported by laboratories having results consistent with the KCRV ranged from 1 mg/g to 6 mg/g when using mass balance based approaches alone, 2 mg/g to 7 mg/g using quantitative 1H NMR (qNMR) based approaches and from 1 mg/g to 2.5 mg/g when a result obtained by a mass balance method was combined with a separate qNMR result.The material provided several analytical challenges. In addition to the need to identify and quantify various related amino acid impurities including leucine, isoleucine, alanine and α-amino butyrate, care was required to select appropriate conditions for performing Karl Fischer titration assay for water content to avoid bias due to in situ formation of water by self-condensation under the assay conditions. It also proved to be a challenging compound for purity assignment by qNMR techniques.There was overall excellent agreement between participants in the identification and the quantification of the total and individual related structure impurities, water content, residual solvent and total non-volatile content of the sample. Appropriate technical justifications were developed to rationalise observed discrepancies in the limited cases where methodology differences led to inconsistent results.The comparison demonstrated that to perform a qNMR purity assignment the selection of appropriate parameters and an understanding of their potential influence on the assigned value is critical for reliable implementation of the method, particularly when one or more of the peaks to be quantified consist of complex multiplet signals.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIP...

No abstract

e aim of this work is to present an integrated process for the remediation of soils contaminated with o,o-dimethyl o-(pnitrophenyl)phosphorothioate, known as methyl parathion (MP), by surfactant-enhanced soil washing and treatment of the produced wastewaters in an aerobic-submerged bio lter. Soils containing approximately 0.4 and 13 mg/kg of MP were washed using anionic, nonionic, zwitterionic, and natural surfactants. Between 63 and 98% of the initial concentrations of MP were removed. Wastewater produced from soil washing with the addition of a natural biosurfactant, locust bean gum [0.01% (w/w)], was used for the experiments in an aerobic-submerged bio lter in which MP concentration decreased from an initial value of 0.78 mg/L up to a value of 0.05 mg/L in 6 days, indicating the feasibility of the treatment proposed.

RESUMEN: La encefalopatía por hipoxia es causa de discapacidad y requiere de nuevas estrategias terapéuticas. El pirofosfato de tiamina (PPT) es un cofactor esencial de enzimas fundamentales en el metabolismo de la glucosa, cuya disminución puede conducir a la falla en la síntesis de ATP y a la muerte celular. El objetivo de este estudio fue determinar si la administración de PPT, puede reducir el daño celular en un modelo de hipoxia neonatal en ratas. Animales de 11 días de edad fueron tratados con PPT (130 mg/kg) en dosis única o solución salina, una hora antes del protocolo de hipoxia o al término de ésta. Los cerebros fueron colectados para la evaluación del daño celular. Además, se tomaron muestras sanguíneas para evaluar los indicadores gasométricos de presión de dióxido de carbono (PaCO 2) y de oxígeno (PaO 2) en sangre arterial y pH. Los resultados muestran que la administración de PPT previa a la inducción de hipoxia, reduce el daño celular y restablece los indicadores gasométricos. Estos datos indican que el uso de PPT reduce el daño inducido por la hipoxia en animales neonatos. PALABRAS CLAVE: Pirofosfato de tiamina; Hipoxia; Daño celular; Gasometría hemática. INTRODUCCIÓN Con una incidencia de entre 1 y 6 por 1000 recién nacidos vivos (Ferriero, 2004) la hipoxia es causa importante de morbimortalidad cuando ocurre en la etapa neonatal. Las secuelas más importantes asociadas son: parálisis cerebral, discapacidad cognoscitiva y epilepsia (Delivoria-Papadopoulos & Mishra, 1998).