Aerosol diagnostics and inductively coupled plasma mass spectrometry with demountable concentric nebulizers

Abstract

A demountable concentric nebulizer (DCN) is evaluated for inductively coupled plasma mass spectrometry (ICPMS). This nebulizer operates at conditions similar to a commercial pneumatic nebulizer used in ICP spectrometries, but is easily fabricated and is considerably less expensive. Key aerosol diagnostics data, and analytical figures of merit are presented for the DCN used in ICPMS. The DCN produces a better quality primary aerosol when using inner capillaries of smaller diameters. At a solution uptake rate of about 500 µL min⁻¹ and a nebulizer gas flow rate of 1.0 L min⁻¹, the Sauter mean diameter (D_3,2) of the primary aerosol of the DCN is 7 µm and 14 µm for solution capillaries having an i.d. of 95 µm (DCN-1) and 190 µm (DCN-2), respectively. Based on the cumulative mass percent data, nearly 70% of the total mass of the droplets produced by DCN-1, under the above conditions, is composed of droplets having sizes less than 10 µm. The D_3,2 of the tertiary aerosol of DCN-1, under the same operating conditions, is reduced to 5 and 3 µm when the nebulizer is coupled to a Scott-type and a cyclonic spray chamber, respectively. The tertiary aerosol of the DCNs studied does not show substantially different D_3,2 values, particularly when the cyclonic spray chamber is used. Under optimum conditions, detection limits, sensitivities, and precision for the DCN compare favorably with a commercially available crossflow nebulizer. The accuracy and precision of the DCN in ICPMS measurements are demonstrated using two standard reference materials: SRM 1643c (Trace Elements in Water), and SRM 1570 (Trace Elements in Spinach).