Varian SpectrAA 200
Atomic Absorption Spectrophotometer with
Graphite Furnace Atomization		 GFAAS1.jpg (17631 bytes)

Instrument Components:

    The SpectrAA is a state-of-the art computer-controlled instrument, providing automation to most steps of the analysis.   It is important, however, not to understand the components of the instrument to ensure successful operation and reliable results.

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 The figure at left illustrates the autosampler and graphite furnace components of the SpectrAA.  Click on a letter for a brief description of each component.

The yellow arrow in the figure shows the path of light left to right from the source, through the furnace and to the detector.

A. Furnace Assembly

Proper alignment of the graphite furnace in the assembly is plays a major role in the quality of the results obtained in a GFAAS experiment.  The assembly itself is water cooled (cooling water must be turned on prior to use) and employs an inert gas such as argon to flush material from the furnace after each measurement (argon must also be turned on prior to use).  Once properly aligned, measurements are automated and can be very reproducible.

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B. Source Carousel

Since we are interested in exciting specific atomic lines in the sample, AA requires a photon source with a wavelength corresponding to these narrow atomic lines.  Typical sources for AA are Hollow Cathode Lamps (labeled A in the photo).  Our instrument can house four separate lamps, each of which is specific to one  or two atoms.  It is important that the carousel is oriented so the lamp that corresponds to the element of interest is active.

This compartment also holds a deuterium lamp (labeled B), that is used for background correction.

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C. Autosampler and Sample Carousel

The sample carousel can hold up to 50 samples, in addition to standard and blank solutions for use in an analysis.  Each sample (contained in a small sample vial), is individually accessible with the sampling arm through the Varian software.

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D. Sampling Arm and Capillary

Transfer of a user-selected volume of sample from the sample carousel to the furnace is accomplished using this motor-driven arm.  Using a syringe pump, microliter-sized samples are drawn into the capillary and carefully deposited onto the flat bottom of the furnace.  Proper care and feeding of the capillary is critical for accurate sample transfer.  The photo shows the sample arm in position to deliver a sample to the furnace..

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E. Capillary Drain Tube

To help keep the sample capillary tube clean, it is periodically flushed with a dilute solution of trace-metal grade nitric acid.  A reservoir for this solution is screwed onto the bottom of the autosampler.

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F. Sample Carousel Cover

This plastic cover should be placed on top of the sample carousel to help minimize exposure to particulates and other possible contaminants.  The cover is "keyed" so that it only fits in one orientation.

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