Producing large quantities of high quality minitubers at low cost is essential for an economically viable supply of seed potatoes. Here we systematize the technical and economic aspects of aeroponics and provide a benchmark comparison of this technology with other mini-tuber production systems as developed in Latin America: conventional, semi-hydroponics, and fiber-cement tiles technology. Research methodologies included: 3-year registration of cash flows and production registers of aeroponics, economic and technical surveys, in-depth inquiry with managers of technologies. Results show that aeroponics as promoted by

Recebido em 23/4/08; aceito em 3/2/09; publicado na web em 7/5/09 COMPARISON OF QUANTIFICATION METHODS IN GAS CHROMATOGRAPHY: AN EXPERIMENT FOR CHEMISTRY COURSES. This article describes an experiment designed to teach quantitative determination in gas chromatography (GC) in Organic and Analytical Chemistry practical classes. The experiment consisted of extracting and analyzing eugenol from clove seeds to perform a quantitative approach aimed at comparing results obtained by external and internal calibration procedures. Therefore, this experiment proved to be very effective tool to enhance students awareness on the need to understand different types of calibration in GC and on how to avoid common experimental errors, and to find the best ways to eliminate their interference during the quantitative analysis phase.Keywords: GC; quantitative analysis; teaching. INTRODUÇÃOA cromatografia gasosa é um tópico apresentado nos cursos de Química, tanto nas disciplinas de Química Analítica como de Química Orgânica. No primeiro caso, a cromatografia gasosa é mostrada na maioria das vezes como uma ferramenta analítica quantitativa, uma vez que o cromatógrafo está ligado a um detector capaz de responder a um determinado composto de maneira proporcional a sua concentração. 1,2 No caso da Química Orgânica, um enfoque maior é dado ao aspecto qualitativo e de separação de misturas, embora a sua utilização em termos quantitativos também ocorra. A cromatografia gasosa é normalmente utilizada como ferramenta analítica nos laboratórios de Química Orgânica durante o curso de graduação. 3 Os livros de Química Orgânica, entretanto, raramente trazem teorias sobre o assunto, apenas ressaltando um dos detectores utilizados que é o espectrômetro de massas. 4 A difusão e o desenvolvimento da cromatografia gasosa se deram por seu potencial para realizar análises quantitativas com velocidade e rapidez na determinação de compostos orgânicos presentes em concentrações relativamente baixas em diferentes tipos de amostras. As matrizes complexas normalmente sofrem diferentes processos de extração e o composto de interesse pode ser então quantificado através desta técnica, que passa assim a ter grande importância na pesquisa científica básica e nas suas aplicações na indústria.O método direto para análises cromatográficas quantitativas envolve a preparação de uma série de soluções-padrão de composições próximas à concentração do analito na amostra, com o objetivo de realizar uma calibração externa. Os cromatogramas dos padrões são então obtidos, e as alturas ou as áreas dos picos terminam lançados em um gráfico em função da concentração. Idealmente a curva obtida deve ser uma reta que passa pela origem e a concentração da amostra é obtida a partir da equação desta reta. 5 Porém, algumas vezes se obtêm curvas com coeficientes lineares positivos ou negativos, cabendo ao analista a realização de um tratamento criterioso dos dados da curva. As fontes mais importantes de erros analíticos através do uso deste método são as incertezas no volume da amostra e...

Potato is the most important crop in Peru and late blight is the main disease affecting the crop. However, new varieties that are resistant to late blight often lack other traits that farmers and consumers prefer. Using participatory varietal selection, this study seeks to identify clones with high potential to become varieties with resistance to late blight but also feature a high marketable tuber yield and other preferred agronomic traits. During 2016–2017, 36 clones previously selected for high levels of resistance to late blight from population B developed by the International Potato Center, and three varieties used as controls (INIA 302 Amarilis moderately resistant, INIA303 Canchan and Yungay susceptible to late blight), were evaluated in five Peruvian locations. At harvest, five clones were selected based on (i) evaluations made by farmers through Participatory Varietal Selection, (ii) analysis of mixed models and Best Linear Unbiased Predictors for tuber yield, (iii) low glycoalkaloid content in tubers, and (iv) good organoleptic quality. These clones were evaluated again during 2017–2018 in four locations. Resistance to late blight and good marketable tuber yields were identified as the most important criteria for the selection of a new potato variety. The clones CIP308488.92, CIP308495.227 and CIP308478.59 were selected as promising clones having resistance to late blight and tuber yield superior to the local varieties, INIA-303 Canchan, Yungay, as well as good organoleptic quality and low glycoalkaloid content. These clones can be suggested for variety release in similar agroecological environments.

The contamination of food by heavy metals in areas irrigated with contaminated water is of great concern due to the potential risk to human health. To assess the potential risk of Pb to children's health from consumption of cow's milk in an area of the Mantaro Valley during 2018. Fifty-one children exposed to Pb and eight samples of raw cow's milk were selected. Pb concentrations were analyzed with the atomic absorption spectrometer. The mean Pb content in milk was 0.236 ± 0.057 mg.kg-1 , which exceeded the limits allowed by the Codex Alimentarius. The estimated daily intake of lead was 5.9 x 10-3 mg.kg-1 day-1 ; the estimated risk index (HQ) was below one, which represents a low risk for children. The cancer risk was below 1.0 x 10-4. It is therefore concluded that there is no significant risk to children's health from consumption of cow's milk.

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