Spray Chambers and Desolvation Devices

Chilled/cooled spray chambers and desolvation devices are becoming more and more common in ICP-MS, primarily to cut down on the amount of liquid entering 

Water-Cooled and Peetier-Cooeed Spray Chambers 

---

There are several drawbacks to ultrasonic nebulizer/desolvation systems. Precision is typically somewhat poorer (1% to 3% relative standard deviation) than for pneumatic nebulizers (0.5% to 1.0% relative standard deviation) and washout times are often longer (60 to 90 sec compared to 20 to 30 sec for a pneumatic nebulizer/spray chamber without desolvation). Furthermore, chemical matrix effects are dependent on the amount of concomitant species that enter the ICP per second. Therefore, use of any sample introduction device that increases the amount of sample entering the plasma per second also naturally leads to more severe matrix effects when the sample contains high concentrations of concomitant species. 

Alternative Sample Introduction Techniques Nonstandard sampling accessories like laser ablation systems, flow injection analyzers, electrothermal vaporizers, cooled spray chambers, desolvation equipment, direct injection nebulizers, and automated sample delivery systans and dilu-tors are considered critical to enhancing the practical capabilities of the technique. Their use has increased significantly over the past few years as ICP-MS is being asked to solve more and more diverse application problems. This chapter reflects the increased interest in sampling accessories, especially in the area of specialized sample introduction and desolvation devices to reduce the impact of conunon interferences. 

The most simple desolvation system that can be used is a thermostated spray chamber. With this device the extent of the aerosol solvent evaporation is reduced by working at low temperatures. As a result, the plasma vapour solvent load decreases. A drawback of the thermostated chambers is that the analyte transport efficiency decreases, which can lead to a reduction in the sensitivity. Two-step desolvation systems can also be used to improve the sensitivity and remove... 

The thermospray device produces a wide dispersion of droplet sizes and transfers much of sample solution in unit time to the plasma flame. Therefore, it is essential to remove as great a proportion of the bigger droplets and solvent as possible to avoid compromising the flame performance. Consequently, the thermospray device usually requires both spray and desolvation chambers, especially for analyte solutions in organic solvents. 

Thermospray nebulizers are somewhat expensive but can be used on-line to a liquid chromatographic column. About 10% of sample solution is transferred to the plasma flame. The overall performance of the thermospray device compares well with pneumatic and ultrasonic sprays. When used with microbore liquid chromatographic columns, which produce only about 100 pl/min of eluant, the need for spray and desolvation chambers is reduced, and detection sensitivities similar to those of the ultrasonic devices can be attained both are some 20 times better than the sensitivities routinely found in pneumatic nebulizers. 

In this device the liquid sample is sprayed into a heated spray chamber, where the nebulizer gas transfers the aerosol through the membrane desolvator. An argon flow removes the solvent vapour from the exterior of the membrane. If compared to conventional pneumatic nebulizers, this system enhances analyte transport efficiency and limits solvent loading to the plasma. Oxide and hydride polyatomic ion interferences are significantly reduced, improving the detection limits by an order of magnitude. 

---