A high-efficiency cross-flow micronebulizer for inductively coupled plasma mass spectrometry

A pneumatically driven, high-efficiency cross-flow micronebulizer (HECFMN) is introduced for inductively coupled plasma (ICP) spectrometries. The HECFMN uses a smaller nozzle orifice for nebulizer gas (75 microm in diameter) and a replaceable and adjustable fused-silica capillary for sample uptake. The HECFMN is optimally operated over a wide range of sample uptake rate (5-120 microL/min) at a rf power of 1100 W and nebulizer gas flow rates of 0.8-1.0 L/min when a 50 microm i.d. by 150 microm o.d. capillary is used. The aerosol quality is qualitatively examined in a simple manner, and the transport efficiencies are determined by direct filter collection. Compared with conventional cross-flow nebulizers (CFNs), the HECFMN produces much smaller and more uniform droplets and thus provides much higher analyte transport efficiencies (generally 24-95%) at the sample uptake rates of 5-100 microL/min. Several analytical performance indexes are acquired using an Ar ICPMS system. The sensitivities and detection limits measured with the HECFMN at 50 microL/min sample uptake rate are comparable to or improved over those obtained with a conventional CFN consuming 1 mL/min sample, and the precisions with the HECFMN (typically 1.1-1.7% RSDs) are slightly better than those with the CFN (1.6-2.3% RSDs). The ratios of refractory oxide ion-to-singly charged ion (CeO+/Ce+) are typically in the range from 0.7 to 3.3% for the sample uptake rates of 5-100 microL/min. The free aspiration rate of the HECFMN is 8.9 microL/min for distilled deionized water at the nebulizer gas flow rate of 1.0 L/min without any effect of pressure. The features of the HECFMN suggest good potential for HECFMN use in interfacing ICPMS with capillary electrophoresis and microcolumn high-performance liquid chromatography.