Cobalt as chemical modifier to improve chromium sensitivity and minimize matrix effects in tungsten coil atomic emission spectrometry

Autor(es)

Silva, Sidnei G. ^[1] ; Donati, George L. ^[2] ; Santos, Luana N. ^[1] ; Jones, Bradley T. ^[2] ; Nobrega, Joaquim A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Carlos, Dept Chem, Grp Appl Instrumental Anal, BR-13560970 Sao Carlos, SP - Brazil

^[2] Wake Forest Univ, Dept Chem, Winston Salem, NC 27109 - USA

• Tipo de documento: Artigo Científico
• Fonte: Analytica Chimica Acta; v. 780, p. 7-12, MAY 30 2013.
• Citações Web of Science: 5

Resumo

Cobalt is used as chemical modifier to improve sensitivity and minimize matrix effects in Cr determinations by tungsten coil atomic emission spectrometry (WCAES). The atomizer is a tungsten filament extracted from microscope light bulbs. A solid-state power supply and a handheld CCD-based spectrometer are also used in the instrumental setup. In the presence of 1000 mg L-1 Co, WCAES limit of detection for Cr (lambda=425.4 nm) is calculated as 0.070 mg L-1; a 10-fold improvement compared to determinations without Co modifier. The mechanism involved in such signal enhancement is similar to the one observed in ICP OES and ICP-MS determinations of As and Se in the presence of C. Cobalt increases the population of Cr+ by charge transfer reactions. In a second step, Cr+/e(-) recombination takes place, which results in a larger population of excited-state Cr atoms. This alternative excitation route is energetically more efficient than heat transfer from atomizer and gas phase to analyte atoms. A linear dynamic range of 0.25-10 mg L-1 and repeatability of 3.8% (RSD, n = 10) for a 2.0 mg L-1 Cr solution are obtained with this strategy. The modifier high concentration also contributes to improving accuracy due to a matrix-matching effect. The method was applied to a certified reference material of Dogfish Muscle (DORM-2) and no statistically significant difference was observed between determined and certified Cr values at a 95% confidence level. Spike experiments with bottled water samples resulted in recoveries between 93% and 112%. (C) 2013 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 10/50238-5 - Determinacao de fosforo, enxofre e silicio em biodiesel usando espectrometro de massa acoplado ao plasma induzido com interface de colisao e reacao
• Beneficiário: George Luis Donati
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 11/13288-7 - Desenvolvimento de sistemas de vaporização e atomização empregando radiação no infravermelho e filamento de tungstênio
• Beneficiário: Sidnei Gonçalves da Silva
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 07/51448-0 - Construcao e aplicacao analitica de espectrometro de emissao atomica com atomizacao eletrotermica em filamento de tungstenio.
• Beneficiário: Joaquim de Araújo Nóbrega
• Modalidade de apoio: Auxílio à Pesquisa - Regular