A green analytical procedure for determination of copper and iron in plant materials after cloud point extraction

Abstract

Um procedimento analítico limpo baseado em extração em ponto nuvem é descrito para a determinação de cobre e ferro em materiais vegetais. Após a digestão da amostra em frascos fechados em forno de microondas, empregando mistura oxidante diluída (HNO 3 + H 2 O 2 ), os íons metálicos foram simultaneamente extraídos como complexos hidrofóbicos formados com 1,2-tiazolilazo-2-naftol (TAN) usando Triton X-114 como agente extrator. Íons cobre e ferro foram determinados por espectrometria de absorção atômica com chama (FAAS) e ferro também por espectrofotometria de absorção molecular UV-Vis. Nas medidas por FAAS, os limites de detecção (99,7% de confiança) foram estimados em 1 e 10 µg L -1 para cobre e ferro, respectivamente. Respostas lineares para ambos os analitos foram observadas no intervalo de 25-200 µg L -1 . O fator de enriquecimento foi estimado em 30, com extração quantitativa dos complexos avaliada por medidas na solução sobrenadante remanescente após extração. Para a determinação de ferro por espectrofotometria UV-Vis, o limite de detecção (99,7% de confiança) foi estimado em 1 µg L -1 , com resposta linear entre 6 e 60 µg L -1 . A exatidão do procedimento foi avaliada pela determinação dos metais em materiais de referência certificados e os resultados foram concordantes com os valores certificados no nível de confiança de 95%. O consumo de reagentes foi de 1 mL HNO 3 , 1,1 mL H 2 O 2 , 50 mg Triton X-114 e 150 µg TAN por determinação.A green analytical procedure exploiting cloud point extraction for determination of copper and iron in plant materials is presented. After sample digestion with a diluted oxidant mixture (HNO 3 + H 2 O 2 ) in a closed vessel microwave oven, metal ions were simultaneously extracted as hydrophobic complexes formed with 1,2-tiazolylazo-2-naphthol (TAN) using Triton X-114 as extracting agent. Copper and iron were determined by flame atomic absorption spectrometry (FAAS) and iron also by UV-Vis spectrophotometry. For FAAS, the detection limits (99.7% confidence level) were estimated as 1 and 10 µg L -1 for copper and iron, respectively. Linear responses for both analytes were observed in the 25-200 mg L -1 range. The enrichment factors were estimated as 30 for both analytes and the extraction was quantitative, as evaluated by measurements in the supernatant solution remaining after extraction. For iron determination by UV-Vis spectrophotometry, the detection limit was estimated as 1 mg L -1 , with linear response within 6 and 60 mg L -1 . The accuracy of the procedure was evaluated by determination of the metals in certified reference materials and the results agreed with the certified values at the 95% confidence level. In the whole procedure, the reagent consumption was 1 mL HNO 3 , 1.1 mL H 2 O 2 , 50 mg Triton X-114 and 150 mg TAN per determination.Keywords: green analytical chemistry, cloud point extraction, FAAS, spectrophotometry, plant materials, copper, iron IntroductionCopper and iron are important for plant nutrition, being classified as essential micronutrients and usual...

An overview of the Brazilian contributions to Green Analytical Chemistry

“…Apart from the use of chemical modifiers and the gases produced during atomization in some techniques, the main source of waste generation in atomic spectrometry is the sample preparation because most of the approaches require solid samples to be converted to solutions. however, as previously discussed, there are several alternatives for greener sample decomposition and spectrometric techniques usually demands mARIANA R. GAmA et al (Silva et al 2010). Other question to concern in relation to atomic spectrometry is the need for high power suppliers as lower energy consumption is also a goal of GAC.…”

Old and New Flavors of Flame (Furnace) Atomic Absorption Spectrometry

“…In this context and due to characteristics such as simplicity, low cost, efficiency, use of less toxic reagents, and production of low volumes of residues, CPE has become one of the most popular extraction/preconcentration methods in FAAS determinations [141][142][143][144][145][146][147][148][149][150]. Introduced in 1978 by Watanabe and Tanaka [151], CPE is based on the property of some surface-active agents (surfactants or detergents) of being able to aggregate in aqueous solution to form colloidal-sized clusters known as micelles.…”

“…By carefully changing the solution conditions, for example, temperature, pressure, or ionic strength, the surfactant molecules become large aggregates (surfactant-rich phase) which can dissolve metal complexes and are eventually separated from the bulk aqueous solution (surfactantpoor phase) [152][153][154]. Probably due to characteristics such as low toxicity, versatility, and typically low cloud point temperatures, nonionic surfactants are by far the most used in CPE methods [141][142][143][144][145][146][147][148][149][150]. Among those, the most popular is α-[p-(1,1,3,3-tetramethylbutyl)phenyl]-ωhydroxylpolyoxyethylene (Triton X-114), with a cloud point temperature in the 23-25 • C range and a CMC of 0.17-0.30 mmol/L [152].…”

Mixed Micellar Cloud Point Extraction and Spectrophotometric Determination of Iron(II) Using 1,10-Phenanthroline: Effect of Sodium Nitroprusside on Extraction Efficiency

“…Previously, CPE has been successfully applied to the extraction of inorganic analytes, where the metals form complexes with ligands such as APDC (ammonium pyrrolidinedithiocarbamate) [11,12], 5-Br-PADAP (2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol) [13], ECR (eriochrome cyanine R) [3], TAN (1-(2-thiazolylazo)-2-naphthol) [14,15], PHBI (2-phenyl-1H-benzo[d]imidazole) [16] and NR (neutral red) [4]. In the present work 1,10-phenanthroline has been used for the extraction of Fe 2+ .…”