RESUMEN
Sodium in vacuum gas oils (VGOs), even at trace levels, produces corrosion by-products in the refinery pipelines and it is a significant catalyst poison, especially for those from atmospheric or vacuum distillation units, thus its concentration in middle-distillate petroleum products needs to be controlled. In addition, sodium contamination was an issue in this study, as sodium might be present even in the dust floating in the air. The use of an ultrapure sodium-free water and the disposal of a clean and dust-free room were the key to be successful on the development of this method. Different sample preparation methods were studied as sample preparation optimisation was an important step in this study. Dry ashing by different processes, wet acid digestion with different acid mixtures, wet acid microwave-assisted digestion, and dilution with a proper solvent were tried to find the appropriate sample preparation method. An accurate and precise method for the determination of sodium in vacuum gas oils (VGOs) by ICP-OES at trace levels has been developed by ashing the sample with a new piece of equipment designed and created by the Instituto de Tecnología Cerámica (ITC), that permits to calcine the sample in one hour and avoids analyte losses or analyte contamination. The quantification limit achieved by the whole sodium determination method is lower than 1â¯mgâ¯kg-1, which allows it to be used as control method in the petrochemical industry.
RESUMEN
OBJECTIVE: Recently it has been pointed out that inflammation and infections caused by germs such as Chlamydia pneumoniae are independent cardiovascular risk factors for the general population, but information about these relationships in dialysis patients is scarce. This work was done to analyze the association of C-reactive protein (CRP) and IgG anti-Chlamydia pneumoniae antibodies (anti-Chlp-IgG) as independent cardiovascular risk factors in incident patients on continuous ambulatory peritoneal dialysis (CAPD). DESIGN: Single-cohort, prospective observational study. SETTING: Three CAPD centers from the Instituto Mexicano del Seguro Social, and one from the Instituto de Seguridad y Servicios Sociales de los Trabajadores del Estado, Mexico. PATIENTS: A cohort of 75 adult incident patients on CAPD, without clinical signs of congestive heart failure, coronary heart disease, or peripheral arterial insufficiency. No restrictions for age, gender, or cause of renal failure were applied. PRIMARY OUTCOME: Mortality. METHODS: Demographic variables, body composition by electrical bioimpedance, serum glucose, urea, creatinine, lipids, homocysteine, nutritional markers (albumin, prealbumin, and transferrin), CRP, and anti-Chlp-IgG were measured and registered at the time of the first admission. When a patient died, the cause of death was determined by review of the clinical chart. RESULTS: Mean follow-up time was 10.25 patient-months. There were 14 cardiovascular deaths. CRP was positive (> 10 mg/L) in 64% of the patients, and anti-Chlp-IgG in 64%; 29% of the patients were positive for both markers. The relative risk for cardiovascular mortality was 6.23 for patients positive for either CRP or anti-Chlp-IgG, and increased to 9.52 when both markers were positive. Multivariate analysis revealed that CRP and anti-Chlp-IgG were stronger cardiovascular death predictors than age, diabetes, and nutritional status. CONCLUSION: These data suggest that inflammation and the presence of Chlamydia pneumoniae infections are important predictors of cardiovascular death in patients on CAPD.