Combustion generated nanomaterials: online characterization via an ICP-MS based technique. Part I: calibration strategy with a TGA

The coupling between a scanning mobility particle sizer (SMPS) and an inductively coupled mass spectrometry (ICP-MS) was in the past shown to obtain simultaneous size-resolved and elemental information on nanoparticles, using a rotating disc diluter (RDD) as conditioning and dilution system. A calibration strategy for the hyphenated RDD-SMPS-ICP-MS setup is presented here. Evaporation experiments of ZnCl2 powder were performed at four different temperatures, using a TGA as an aerosol source to correlate linearly the weight in loss of the TGA with the averaged ICP-MS intensities measured in transient mode. The calibration curve of Zn showed a good correlation factor (R-2 = 0.9985) and a sensitivity of 20.95 x 10(3) counts ng(-1). The LoD (limit of detection) of the method was estimated to be approximate to 32 ng cm(-3), once the total dilution of the whole setup is considered. A second set of experiments was performed, where ZnO and CaCl(2)2H(2)O powders were used as reactants to generate ZnCl2 particles. The output data of the two instruments were treated and appropriately converted, to allow a direct and quantitative comparison between the performances of SMPS and ICP-MS. The ICP-MS signal of Zn was quantified by using the external calibration performed with the coupling of a TGA with an ICP-MS, while the SMPS volume data used two general assumptions, namely spherical morphology and bulk density of ZnCl2. Additional TEM analysis performed on the size-selected ZnCl2 particles allowed to check their morphology. The proposed calibration strategy of the ICP-MS signals enables to evaluate the SMPS quantification procedure.