Evaluation of the analytical performances of a valve-based droplet direct injection system by inductively coupled plasma-atomic emission spectrometry

Abstract

We have developed a sample introduction system using a magnetic valve type dispenser, named “droplet direct injection nebulizer (D-DIN)”. In the case of the D-DIN, sample solution is directly injected as a single droplet or a series of droplets into the plasma. The droplet volume can be controlled across a wide range of droplet size from 700 pL (110 μm) to 100 nL (580 μm) by changing the inner diameter of the nozzle tip, back pressure and valve open time. The D-DIN system additionally enables direct injection of cells contained in a droplet into the plasma. In this study, the droplet system was optimized, and droplet characterization and analytical performances by emission profiles were investigated. When the emission intensities of 15 nL-volume droplets were measured by side-on observation, the detection limits of Na, Mg and Sr were 20.3 pg (1.35 μg mL⁻¹), 56.5 pg (3.77 μg mL⁻¹) and 20.6 pg (1.37 μg mL⁻¹), respectively. Finally, a single droplet containing yeast cells was directly introduced into ICP and the emission profile of Na was measured with a satisfactory signal to noise ratio.