title: Fast determination of trace elements in organic fertilizers using a cup-horn reactor for ultrasound-assisted extraction and fast sequential flame atomic absorption spectrometry.
abstract: A fast and accurate method based on ultrasound-assisted extraction in a cup-horn sonoreactor was developed to determine the total content of Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in organic fertilizers by fast sequential flame atomic absorption spectrometry (FS FAAS). Multivariate optimization was used to establish the optimal conditions for the extraction procedure. An aliquot containing approximately 120 mg of the sample was added to a 500 µL volume of an acid mixture (HNO3/HCl/HF, 5:3:3, v/v/v). After a few minutes, 500 µL of deionized water was added and eight samples were simultaneously sonicated for 10 min at 50% amplitude, allowing a sample throughput of 32 extractions per hour. The performance of the method was evaluated with a certified reference material of sewage sludge (CRM 029). The precision, expressed as the relative standard deviation, ranged from 0.58% to 5.6%. The recoveries of analytes were found to 100%, 109%, 96%, 92%, 101%, 104% and 102% for Cd, Cr, Cu, Mn, Ni, Pb and Zn, respectively. The linearity, limit of detection and limit of quantification were calculated and the values obtained were adequate for the quality control of organic fertilizers. The method was applied to the analysis of several commercial organic fertilizers and organic wastes used as fertilizers, and the results were compared with those obtained using the microwave digestion procedure. A good agreement was found between the results obtained by microwave and ultrasound procedures with recoveries ranging from 80.4% to 117%. Two organic waste samples were not in accordance with the Brazilian legislation regarding the acceptable levels of contaminants.
authors.affiliation: Instituto de Ciências Exatas, Departamento de Química, Universidade Federal de Minas Gerais, Avenida Presidente Antônio Carlos, 6627, Pampulha, PO Box 702, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Leonel Silva
authors.initials: LS
authors.lastname: Teixeira
authors.affiliation: Laboratório de Química Agropecuária, Instituto Mineiro de Agropecuária (IMA), BR 040, Km 527, CEP 32145-900, Contagem, Minas Gerais, Brazil.
authors.forename: Heulla Pereira
authors.initials: HP
authors.lastname: Vieira
authors.affiliation: Instituto de Ciências Exatas, Departamento de Química, Universidade Federal de Minas Gerais, Avenida Presidente Antônio Carlos, 6627, Pampulha, PO Box 702, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Cláudia Carvalhinho
authors.initials: CC
authors.lastname: Windmöller
authors.affiliation: Instituto de Ciências Exatas, Departamento de Química, Universidade Federal de Minas Gerais, Avenida Presidente Antônio Carlos, 6627, Pampulha, PO Box 702, CEP 31270-901, Belo Horizonte, Minas Gerais, Brazil. Electronic address: clesia@qui.ufmg.br.
authors.forename: Clésia Cristina
authors.initials: CC
authors.lastname: Nascentes
mesh_terms: D005308:Fertilizers / Q000032:analysis*; D057230:Limit of Detection; D009930:Organic Chemicals / Q000032:analysis*; D012015:Reference Standards; D015203:Reproducibility of Results; D013054:Spectrophotometry, Atomic / Q000379:methods*; D014131:Trace Elements / Q000032:analysis*; D014465:Ultrasonics
chemical_list: D005308:Fertilizers; D009930:Organic Chemicals; D014131:Trace Elements
keywords: FS FAAS; Fast determination; Low cost; Metals; Organic fertilizers; Ultrasonic extraction