Direct solid sampling by flame atomic absorption spectrometry: determination of manganese in coal samples

Abstract

Um novo sistema para análise direta de amostras sólidas por espectrometria de absorção atômica com chama é proposto como alternativa para a determinação de elementos traço em carvão. Para a demonstração do potencial do procedimento a determinação de manganês foi investigada. Amostras de carvão foram moídas e pesadas diretamente em recipientes de polietileno e transportadas na forma de um aerossol seco até uma cela de quartzo posicionada entre o feixe óptico e a base do queimador. Sinais transientes foram totalmente integrados em 1 segundo. A influência das condições operacionais sobre os sinais foi estudada. Sinais de fundo foram sempre baixos e uma massa característica de 1,9 ng Mn foi encontrada. Os resultados foram considerados satisfatórios com respeito à exatidão (entre 97,5 e 103,2%) e precisão (RSD melhor que 6%). O sistema proposto é simples e pode ser facilmente adaptado a espectrômetros comerciais, permitindo a análise de mais de 80 amostras por hora.A new device for the direct solid analysis by flame atomic absorption spectrometry was investigated as an alternative technique for the determination of trace elements in coal. The potential application of the proposed procedure for the determination of manganese was investigated. Ground coal test samples were weighed directly into polyethylene vials and carried as a dry aerosol to a slotted quartz vaporization cell placed between the flame burner and optical path. The transient signals obtained were totally integrated in 1 second. The effect of operating conditions on the analytical signal was investigated. Background signals were always low and a Mn characteristic mass of 1.9 ng was found. Results were considered satisfactory regarding to both accuracy (between 97.5 and 103.2%) and precision (RSD better than 6%). The proposed system is simple and can be easily adapted to any conventional atomic absorption spectrometers allowing the analysis of more than 80 test samples in an hour.

A Glimpse of Recent Developments in Brazilian Analytical Chemistry

“…The same technique was successfully applied for direct solid analysis of many analytes in coal samples, such as recently demonstrated for lead (Borges et al 2006a). An interesting strategy also based in direct solid sampling using conventional flame AAS was proposed by Flores et al (2004b) for manganese determination in coal samples. The main aspect of this work was the use of a simple and effective lab-made device for solid analysis.…”

Atomic spectrometry update. Environmental analysis

“…Under these conditions, a detection limit of 0.46% Fe 2 O 3 in the solid was achieved with a throughput of 10 samples per hour. Flores and co-workers 233 proposed a procedure involving direct analysis of solids by FAAS for the determination of Mn in coals. Ground coal samples were carried as a dry aerosol to a slotted quartz vaporisation cell placed between the flame burner and spectrometer.…”

“…For this they employed a modified version of a method originally developed by Thirlwall et al 255 The correction of the tail contribution under each peak was based on the tail shape measurements on monisotopic ion beams, rather than the usual half-mass zeros baseline estimation. A 236 U- 233 U double spike was used to correct for mass bias. Sample introduction was via a microconcentric, desolvating nebuliser, which allowed precise 234 U/ 238 U ratios to be determined on a minimum of 200 ng U, with a 234 U signal of approximately 4-5 mV being monitored for 50 measurement cycles of 5 s each.…”

Determination of Cd in blood by microwave-induced combustion coupled to flame furnace atomic absorption spectrometry

“…17 On the other hand, some works have demonstrated the feasibility of using solid sampling flame atomic absorption spectrometry (SoS-FAAS) for trace analysis. 7,[18][19][20][21] In these works, a conventional air/ acetylene flame was used as atomizer and samples were weighed directly into a small polyethylene vial connected to a glass chamber. Air was used to transport ground samples as dry aerosol to a T-shaped quartz cell positioned above the burner in the optical path of spectrometer.…”

“…In spite of good accuracy and relatively low LODs had been obtained with this system a limitation related to the small sample mass that could be introduced into the atomizer was reported. 7,[18][19][20][21] To overcome this problem, solid samples were introduced as pellets into a quartz cell for analysis by FAAS. 22 With this system, samples up to 7 mg could be weighed into a small paper capsules and introduced into a quartz cell heated by an air/acetylene flame and LOD as low as 0.23 mg g -1 was obtained for cadmium determination.…”