Determination of metal impurities in carbon nanotubes by direct solid sampling electrothermal atomic absorption spectrometry

Abstract

soluções aquosas e massa máxima de amostra. Para comparação dos resultados as amostras foram analisadas por espectrometria de massa com plasma indutivamente acoplado (ICP-MS) e espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) após decomposição por via úmida em sistema de alta pressão assistida por micro-ondas e também por combustão iniciada por micro-ondas. Não foram observadas diferenças significativas entre os resultados obtidos pelo método proposto e pelas outras técnicas. A exatidão também foi avaliada por comparação com resultados de análise por ativação neutrônica (NAA). A calibração foi possível com soluções de referência aquosas. Os sinais de fundo foram sempre inferiores a 0,02 (altura de pico) e o uso de modificador químico não foi necessário. O método proposto possibilitou a determinação de todos os analitos, com menores limites de detecção quando comparados com as outras técnicas.Metal impurities (Al, Cd, Co, Cr, Cu, Mg, Mn and Pb) were determined in carbon nanotubes (CNTs) by direct solid sampling electrothermal atomic absorption spectrometry (DSS-ET AAS, deuterium lamp background corrector). Parameters as pyrolysis and atomization temperatures, use of Pd as chemical modifier, feasibility of calibration using aqueous standard solutions and maximum sample mass were investigated. Results obtained by the proposed method were compared with those obtained by neutron activation analysis (NAA) and also by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP OES) after high-pressure microwave assisted wet digestion and microwave-induced combustion methods. No significant differences were observed between the results obtained by DSS-ET AAS, ICP-MS and ICP OES after both digestion methods and also by NAA. Calibration was performed using aqueous standards. Background signals were always lower than 0.02 (peak height) and no chemical modifier was used. The proposed method allowed the determination of all elements in CNTs with lower limits of detection in comparison with other techniques.Keywords: carbon nanotubes, metal impurities, solid sampling, electrothermal atomic absorption spectrometry IntroductionSince the advent of nanotechnology the development of new materials with a wide range of special properties has been performed for very different applications in almost all technological fields. With the discovery of carbon nanotubes (CNTs) by Iijima, 1 this new class of nanomaterials provided unique chemical, mechanical and electronic properties. In recent years, carbon nanotubes have received a growing interest in several fields as materials industry, electronics, medicine and also in analytical applications. [2][3][4][5][6][7] Carbon nanotubes can be described as a kind of graphite structure which is based on benzene-type hexagonal rings of carbon atoms, rolled up in a nanoscale tube (diameter ranging from a few tenths to tens of nanometers). This nanomaterial can be defined as a single-wall carbon nanotube (SWCNT) ...

Comparison of sample digestion techniques for the determination of trace and residual catalyst metal content in single-wall carbon nanotubes by inductively coupled plasma mass spectrometry

“…Results are presented as a mean ± SD deviation based on 4 replicate measurements. Additionally, data generated by NAA [29] are presented as these represent the "gold standard" by which all other results are compared since NAA is not compromised by the need to ensure digestion and recovery of the analytes and has a long and distinguished track record of proven performance [4,6,7,12]. Unfortunately, Pb is not accessible by NAA and comparative data generated by SS-CS-GF-AAS were used instead.…”

“…Although the MIC technique has earlier been reported to be, it has some limitations when applied to matrices having a high content of inorganic material. Despite earlier publications purporting to demonstrate successful methodologies for the complete digestion of SWCNTs [4,5,7,8,11,12,29], it is clear that the quality of the material may influence the effectiveness of this process and the analyst must exercise caution in the interpretation of the results. Although sample combustion via a low pressure oxygen cold plasma ashing procedure has not been investigated, this approach may alleviate many of the issues raised [32] but at the expense of throughput since these devices are typically limited to oxidation rates of 5-10 mg/h of carbon.…”

“…As a complimentary approach to NAA, solid sampling graphite furnace atomic absorption with a continuum source (SS-CS-GF-AAS) [11,12] has also been utilized, as no sample preparation is required. However, small subsamples (several mg) may raise issues regarding homogeneity and data quality, and care must be taken with calibration to ensure complete atomization of the sample.…”

Ionic liquid-assisted multiwalled carbon nanotube-dispersive micro-solid phase extraction for sensitive determination of inorganic As species in garlic samples by electrothermal atomic absorption spectrometry

“…In previous works on thermal analysis, decomposition temperatures of MWCNTs were between 500°C and 700°C under an air atmosphere with carbon dioxide as the main decomposition product [16]. Likewise, in a temperature furnace program used for determination of metal impurities by DSS-ETAAS, pyrolysis temperatures were in the range of 600°C and 1500°C at a heating rate of 50°C s − 1 and holding time of 30 s [17]. Therefore, based on the thermal behavior of MWCNTs, pyrolysis temperature was optimized.…”

Photochemical vapor generation for removing nickel impurities from carbon nanotubes and its real-time monitoring by atomic fluorescence spectrometry

“…Consequently, the metal impurities are inherently present in CNT products. Many characterization techniques have been applied for the purity evaluation of CNTs [2], such as scanning and transmission electron microscopy (SEM and TEM), thermogravimetric analysis (TGA) and Raman spectroscopy as well as near-infrared (NIR) spectroscopy; and some quantitative analytical methods have also been developed for the analysis of metal impurities in CNTs [3][4][5][6][7][8].…”