Evaluation of metal ions in rice samples: extraction and direct determination by ICP OES

Abstract

Foi desenvolvido um método de extração de íons de metais presentes em amostras de arroz, usando solução amoniacal de EDTA (ácido etilenodiamino tetraacético), pH ≥ 10, como agente extrator, sob as seguintes condições otimizadas: 0,20 g de amostra de arroz e 5,00 mL da solução amoniacal de EDTA, com 5 min de tempo de exposição em ultrassom. Usando condições robustas de ICP OES (espectrometria de emissão atômica por plasma acoplado indutivamente), foi possível analisar a solução extraída, obtendo-se valores de recuperação acima de 90% para a maioria dos elementos estudados (P, K, Mg, Ca, Zn, Mn, Cu e Mo) com RSD < 5%. Os resultados mostraram concordância com aqueles obtidos por extração assistida por microondas e para o material de referência certificado de farinha de arroz (NIST SRM 1568a). Os limites de detecção do método ficaram no intervalo de 0,007 mg kg -1 (Mn) -48,68 mg kg -1 (K), mostrando uma detectabilidade adequada para a determinação das espécies de interesse. A análise das diversas amostras indicou que o arroz brasileiro integral contém teores mais elevados dos constituintes estudados, seguido pelo arroz parboilizado e o arroz agulhinha.A method for extraction of metal ions present in rice samples using ammoniacal EDTA solution, pH ≥ 10, as extractor agent is proposed under the following optimized conditions: 0.20 g of rice sample and 5.00 mL of ammoniacal EDTA (ethylenediaminetetraacetic acid) solution, with 5 min of ultrasound exposure time. Using robust ICP OES (inductively coupled plasma atomic emission spectrometry) conditions, direct analysis of the extraction solution was allowed, and the recovery values obtained were above 90% for most of the studied elements (P, K, Mg, Ca, Zn, Mn, Cu and Mo) with RSD < 5%. The results were in good agreement with those obtained by microwaveassisted extraction and for the reference material of rice flour (NIST SRM 1568a). The limits of detection of method were in the range of 0.007 mg kg -1 (Mn) -48.68 mg kg -1 (K), showing adequate detectability for the determination of the analytes. The analysis of different samples indicated that Brazilian "integral" rice contains higher contents of the constituents studied, followed by "parboiled" rice, and the "agulhinha" rice a long and thin grain type. Keywords: rice samples, ethylenediaminetetraacetic acid, elemental determination, ICP OES IntroductionRice (Oryza sativa L.), actually represents one of the most important foodstuffs in the world; it is the basic dietary product for more than a thousand millions of human beings. Approximately 90% of rice produced in all the world is cultivated and consumed at the Asia. However, the Latin America occupies the second place in production and the third place in relation of rice consumption. Within this context, Brazil is considered one of the biggest rice manufacturer, and its consumption is estimated about 74-76 kg per habitant per year.1 Despite of great national consume, the knowledge about Brazilian rice nutritional composition, taking into account the identification of in...

Toxic and micronutrient elements in organic, brown and polished rice in Brazil

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Understanding interaction effect of arbuscular mycorrhizal fungi in rice under elevated carbon dioxide conditions

“…Determination of nitrogen concentration was done following the modified Kjeldahl method , AP determination using the vanadomolybdo phosphoric acid method, and available potassium determination by the flame photometer method . Contents of zinc, manganese, and copper content in grain were determined using inductively coupled plasma‐optical emission spectrometry and expressed as parts per million dry‐grain weight. The agronomic parameters monitored included the number of tillers, panicles, panicle weight, grains per panicle and GY recorded as per standard methods .…”

Aqueous Phase Extraction as Sample Preparation Procedure for Sodium Determination in Infant Foods

“…The extraction techniques for the quantitation of metal species can be an interesting and efficient alternative sample preparation procedure compared to the traditional methods. 15 Notably, the use of aqueous phase extraction as a sample preparation procedure for the determination of the concentration of water-soluble metal species, such as Na, may contribute to the decrease in the use of toxic chemical reagents and generation of residues and, furthermore, be compatible with detection by instrumental and classical analytical techniques. Some authors have already used this procedure for quantification of metals in foods.…”