Fast determination of trace elements in organic fertilizers using a cup-horn reactor for ultrasound-assisted extraction and fast sequential flame atomic absorption spectrometry

• Published in: Talanta (Oxford) Vol. 119; pp. 232 - 239
• Main Authors: Teixeira, Leonel Silva, Vieira, Heulla Pereira, Windmöller, Cláudia Carvalhinho, Nascentes, Clésia Cristina
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-02-2014
• Subjects: Chromium; Copper; Extraction; Fast determination; Fertilizers; Fertilizers - analysis; FS FAAS; Limit of Detection; Low cost; Manganese; Metals; Microwaves; Nickel; Organic Chemicals - analysis; Organic fertilizers; Reference Standards; Reproducibility of Results; Spectrophotometry, Atomic - methods; Trace Elements - analysis; Ultrasonic extraction; Ultrasonics; Wastes; Organic fertilizers; Fast determination; FS FAAS; Metals; Ultrasonic extraction; Low cost
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2013.11.018

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 120mg of the sample was added to a 500µL volume of an acid mixture (HNO3/HCl/HF, 5:3:3, v/v/v). After a few minutes, 500µL of deionized water was added and eight samples were simultaneously sonicated for 10min 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.
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•Fast and accurate green method to determine metals in organic fertilizers.•Ultrasound-assisted extraction in cup-horn sonoreactor has high analytical frequency.•After method optimization, an adequate analytical performance was obtained.•Efficiency of ultrasound-assisted extraction was comparable to microwave digestion.•Proposed method can be employed for organic fertilizers quality control.