A capillary electrophoresis model was modified to include the effect of laminar flow. Experimental results using inorganic ions with a wide range of mobilities were compared to model predictions. The effect of laminar flow rate on analysis time, peak widths, peak asymmetry, and electrophoretic resolution is discussed. The laminar flow rate in the electrophoresis capillary was controlled by regulating the sheath flow rate in a concentric nebulizer interface. Laminar flow in the direction of the detector allows the analysis of positive, neutral, and negative species, all in one electrophoretic run, in less than 2 min.
A pneumatic, high-efficiency nebulizer (HEN), consuming only 50 mL of sample per minute, produced detection limits for most lines that were within a factor of 3 of those exhibited by commonly used pneumatic nebulizers that use 1.0 mL of sample per minute. Detection limits were within a factor of 8 for all lines observed, despite the 20 times smaller sample consumption rate for the HEN compared to commonly used nebulizers. The aerosol properties were measured and related to the observed vertical emission profiles, Ar emission intensities, and ion to atom emission intensity ratios. The aerosol properties and plasma excitation conditions were used to understand the origins
An instrument to obtain optical emission and laser-induced fluorescence images of atom or ion clouds, each produced from isolated, monodisperse droplets of sample in an inductively coupled plasma, is described. An excimer laser pumped dye laser is used to produce a large (28-mm × 24-mm) beam for saturated fluorescence from atoms or ions throughout a large portion of the ICP. An intensified charge-coupled device (ICCD) detects optical emission or laser induced fluorescence snapshot images at the focal plane of an aberration-corrected slitless spectrograph. Images produced from a single laser pulse can be detected. Double-exposure emission images with 1-μs gate times can be acquired to monitor the movement of atom or ion clouds produced from a single droplet of sample solution. Variations in the number of atoms or ions produced as a function of time (or height) in the plasma can be monitored. Excitation in the plasma can be assessed from ratios of emission to fluorescence intensities.
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