Analytical nebulizer

The general term nebulizer refers to an apparatus that converts liquids into a fine mist. Nozzles also convert liquids into a fine mist, but do so by pressure through small holes. Nebulizers generally use gas flows to deliver the mist. The most common form of nebulizers are medical appliances such as asthma inhalers or paint spray cans. Analytical nebulizers are a special category in that their purpose is to deliver a fine mist to spectrometric instruments for elemental analysis. They are necessary parts of inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and atomic absorption spectroscopy (AAS).

Analytical nebulizers are used in trace element analysis. This type of work plays an important role in areas of pharmaceutical and clinical study, biological, environmental and agricultural assessment and petroleum testing. They also have nuclear applications.

Most analytical pneumatic nebulizers use the same essential principle (induction) to atomize the liquid: When gas at a higher pressure exits from a small hole (the orifice) into gas at a lower pressure, it forms a gas jet into the lower pressure zone, and pushes the lower pressure gas away from the orifice. This creates a current in the lower pressure gas zone, and draws some of the lower pressure gas into the higher pressure gas jet. At the orifice, the draw of the lower pressure gas creates considerable suction, the extent depending on the differential pressures, the size of the orifice, and the shape of the orifice and surrounding apparatus. In all pneumatic induction nebulizers, the suction near the orifice is utilized to draw the liquid into the gas jet. The liquid is broken into small droplets in the process.

Present induction pneumatic nebulizer designs fit into 5 categories: 1. Concentric: Liquid flow surrounded by a Gas flow or Gas flow surrounded by a Liquid flow; 2. Cross Flow: Gas flow at right angles to the Liquid flow; 3. Entrained: Gas and Liquid mixed in the system and emitted as a combined flow. 4. Babington and V Groove: Liquid is spread over a surface to decrease the surface tension, and passed over a gas orifice; 5. Parallel Path: Liquid is delivered beside a gas orifice and induction pulls the liquid into the gas stream.

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