Determination of silicon and aluminum in silicon carbide nanocrystals by high-resolution continuum source graphite furnace atomic absorption spectrometry

• HR-CS-GFAAS conditions were studied for determining Al and Si in nano-SiC solutions.
• Pyrolysis and atomization curves were recorded with various chemical modifiers.
• Pd–Mg(NO3)2 modifier was the best for Si, while no modifier is needed for Al.
• Vaporization and atomization of various Al-compounds were studied.
• A two-way atomization was identified for Al, but single path for Si.

The determination of Al contaminant and the main component Si in silicon carbide (SiC) nanocrystals with the size-distribution of 1–8 nm dispersed in an aqueous solution was developed using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS). The vaporization/atomization processes were investigated in a transversally heated graphite atomizer by evaporating solution samples of Al and Si preserved in various media (HCl, HNO3). For Si, the best results were obtained by applying a mixture of 5 µg Pd plus 5 µg Mg, whereas for Al, 10 µg Mg (each as nitrate solution) was dispensed with the samples, but the results obtained without modifier were found to be better. This way a maximum pyrolysis temperature of 1200 °C for Si and 1300 °C for Al could be used, and the optimum (compromise) atomization temperature was 2400 °C for both analytes. The Si and Al contents of different sized SiC nanocrystals, dispersed in aqueous solutions, were determined against aqueous (external) calibration standards. The correlation coefficients (R values) of the calibrations were found to be 0.9963 for Si and 0.9991 for Al. The upper limit of the linear calibration range was 2 mg/l Si and 0.25 mg/l Al. The limit of detection was 3 µg/l for Si and 0.5 µg/l for Al. The characteristic mass (m0) was calculated to be 389 pg Si and 6.4 pg Al. The Si and Al content in the solution samples were found to be in the range of 1.0–1.7 mg/l and 0.1–0.25 mg/l, respectively.

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