Validation of the cumulative or replicate NAA method for the determination of trace elements in biological materials

Evaluation of the potential of peas (Pisum sativum L.) to be used in selenium biofortification programs under Mediterranean conditions

Selenium (Se), which has antioxidant, anticancer, and antiviral properties, is an essential micronutrient for humans and animals. This micronutrient is found in high quantity in legumes. Peas have an ever-increasing importance in Spain, and to increase their nutritional value, two foliar Se fertilizers: sodium selenate and sodium selenite, at five different rates: 0, 10, 20, 40, 80 g ha(-1), were studied during the 2010/2011 crop season on semiarid Mediterranean conditions. Sodium selenate was much more effectively taken up by plants compared to sodium selenite. There was a strong linear relationship between the total Se content and Se rate in both sodium selenate and selenite. For each gram of Se fertilization as either sodium selenate or sodium selenite, the increase of total Se concentration in the grain was 148 and 19 μg Se kg(-1) dry weight, respectively. Ingestion of 100 g of peas previously fertilized with 10 g of sodium selenate per hectare would result in an intake of 179 μg of Se. This is almost 90 % of the daily recommended dose needed to reduce the chance of some cancers and about 179 % of the minimum concentration required to prevent Se deficiency diseases in animals. The pea has shown to have a strong ability to uptake and accumulate Se under Mediterranean conditions; therefore, this would make it a very strong candidate for inclusion in biofortification programs aiming to increase Se in the food chain.

Quantification of urinary chorionic gonadotropin in spontaneous abortion of pre-clinically recognized pregnancy: method development and analytical validation

Determination of environmental impacts on reproductive health and specifically on the incidence of early spontaneous abortion requires accurate estimates of the latter. This negative reproductive outcome can be detected by the pattern of elevation and decline of human chorionic gonadotropin (hCG) levels near and shortly beyond the expected time of implantation, requiring daily biomonitoring of hCG levels during the relevant period of the menstrual cycle. Prospective pregnancy studies to assess effects of potentially toxic exposures on human reproductive outcomes can involve up to three menstrual cycles and a huge number of samples in each, for the quantification of the inherently very low hCG levels usually can be determined only in serum. The invasive nature of blood collection, the number of samples needed for the development of prospective studies, and the lack of quantitative methods for the determination of low hCG levels in urine point to the need for collecting urine rather than blood and make it imperative to develop suitable quantitative methods for biomonitoring of very low levels of hCG in urine. This paper describes the development and validation procedures of an automated solid-phase two-site chemiluminescent immunometric assay for the quantification of urinary hCG in early pregnancy and early pregnancy loss. For the validation, both undiluted and diluted urine and control samples have been prepared. From the results, it can be concluded that the assay has a calibration range that extends to 5000 mIU/ml, with a detection limit of approximately 1.2 mIU/ml, practically identical to that found by the IMMULITE 2000 manufacturer's validation study. The intra- and inter-assay precision ranges up to a maximum of around 7%, meaning that the practical limit for functional sensitivity can be established as low as 10%. This means that the immunoassay from DPC can identify, with relatively high confidence, non-pregnant women and the typical "rise and fall" pattern of early pregnancy loss through analysis of urine samples. Results also lead to the conclusion that there is a very good agreement between expected and observed urinary hCG levels indicative of good immunoassay accuracy for the studied range of hCG concentrations. In terms of analyte stability, it can be concluded that urinary hCG is stable under the expected conditions required for ongoing investigations that include temperatures of 2-8 degrees C for up to 48 h and temperatures of around -20 degrees C for longer periods that can extend to over 3 months.