Improved nanonebulizer design for the coupling of nanoHPLC with ICP-MS

Abstract

A novel nanonebulizer (nDS-200e) with extended liquid flow rate range was developed for ICP-MS sample introduction from 50 to 4000 nL min⁻¹. The new device has a distinctly improved design compared to the first prototype (P. Giusti, R. Lobinski, J. Szpunar and D. Schaumlöffel, Anal. Chem., 2006, 78, 965).¹ The robust construction using a very thin polyimide-coated nebulizer capillary (i.d. 20 µm and o.d. 90 µm) was less prone to clogging and did not provoke a high back pressure. An erbium standard solution was used for nebulizer testing. Sample introduction was stable demonstrated by low relative standard deviations (RSDs) between 2 and 4% of the ¹⁶⁶Er signal for flow rates above 200 nL min⁻¹. Different nebulizer and single-pass spray chamber geometries were tested and the addition of a make-up gas was investigated. The optimal make-up gas flow was 10% (0.11 L min⁻¹) of the total gas flow through the spray chamber but led only to a small, not very significant, intensity increase of about 5%. Hence, make-up gas addition is not mandatory for nanoflow nebulisation. The nanonebulizer combined with a single-pass spray chamber was successfully used as multifunctional interface for sheathless and sheath flow nanoHPLC–ICP-MS coupling, including the postcolumn addition of an internal standard. The operation of the coupling was demonstrated with a model sample containing a lutetium labelled peptide (Met-Leu-Phe).