Perkin Elmer AAnalyst 100 Atomic Absorption Spectrometer: Operating Procedure

I) Principle

The Perkin Elmer AAnalyst 100 system consists of a high efficiency burner system with a Universal GemTip nebulizer and an atomic absorption spectrometer.  The burner system provides the thermal energy necessary to dissociate the chemical compounds, providing free analyte atoms so that atomic absorption occurs.  The spectrometer measures the amount of light absorbed at a specific wavelength using a hollow cathode lamp as the primary light source, a monochromator and a detector.  A deuterium arc lamp corrects for background absorbance caused by non-atomic species in the atom cloud.

II) Instrument Setup

A) Empty waste container to mark.  Add deionized water to drain tubing to ensure that water is present in the drain system float assembly.

B) Drain moisture from air compressor.

1) Unplug compressor.

 

2) Reduce compressor pressure to nearly zero by opening the pressure release valve and the drain plug located at the bottom of the tank.

 

3) Close pressure release valve and drain plug.

 

4) Plug in compressor to restart the motor.

C) Install the appropriate Hollow Cathode Lamp for the analyte to be analyzed.

D) Power AAnalyst 100 and printer ON.

E) Ensure that instrument is in AA mode.

F) Recall Method to be analyzed.

G) Ensure that the correct Default Conditions are entered.

H) Align the Hollow Cathode Lamp.

1) Press Energy.

 

2) Press Energy a second time if the bar needs to be brought on scale.

 

3) Adjust the vertical and horizontal lamp adjustment screws to obtain maximum energy.

 

I) Store Method changes in Parameter Entry, Option, Store and #.

 

J) Adjust Burner height.

 

1) Place a white sheet of paper behind the burner to confirm the location of the light beam.

 

2) Lower the burner head below the light beam with the vertical adjustment knob.

 

3) Press Cont (Continuous) to display an absorbance value.

 

4) Press A/Z to Autozero.

 

5) Raise the burner head with the vertical adjustment knob until the display indicates a slight absorbance (0.002).  Slowly lower the head until the display returns to zero. Lower the head an additional quarter turn to complete the adjustment.

 

K) Ignite flame.

 

1) Turn Fume Hood switch ON.

 

2) Open air compressor valve. Set pressure to 50 to 65 psi.

 

3) Open acetylene gas cylinder valve. Set output pressure to 12 to 14 psi.  Replace cylinder when pressure falls to 85 psi to prevent valve and tubing damage from the presence of acetone.

 

4) Press Gases On/Off. Adjust oxidant flow to 4 Units.

 

5) Press Gases On/Off. Adjust acetylene gas flow to 2 Units.

 

6) Press Flame On/Off to turn flame on.

Note: Do not directly view the lamp or flame without protective ultraviolet radiation eyewear.

 

L) Aspirate deionized water through the burner head several minutes.

 

M) Adjust Burner Position and Nebulizer.

 

1) Aspirate a standard with a signal of approximately 0.2 absorbance units.

 

2) Obtain maximum burner position absorbance by rotating the horizontal and rotational adjustment knobs.

 

3) Loosen the nebulizer locking ring by turning it clockwise.  Slowly turn the nebulizer adjustment knob to obtain maximum absorbance. Lock the knob in place with the locking ring.

Note: An element, such as Magnesium, which is at a wavelength where gases do not absorb is optimal for adjusting the Burner and Nebulizer.

 

N) Allow 30 minutes to warm-up flame and lamp.

III) Calibration Procedure

A) Calibrate with standards that bracket the sample concentrations.

 

B) Enter ------ for Std1 in the Default Conditions to obtain absorbance units for each standard.  Construct a data regression curve on a computer spreadsheet. Use standard concentrations as the X axis and absorbances as the Y axis.

 

C) Enter Standard Concentration Values in the Default Conditions to calculate an AAnalyst 100 standard curve.

 

1) Enter the concentration of the lowest standard for STD1 using significant digits.

 

2) Enter the concentrations of the other standards of the calibration curve in ascending order and the concentration of the reslope standard.

 

3) Autozero with the blank before each standard.

 

4) Aspirate Standard 1, press 0 Calibrate to clear the previous curve. Aspirate the standards in numerical order.

Press standard number and calibrate for each standard.

 

5) Press Print to print the graph and correlation coefficient.

 

6) Rerun one or all standards, if necessary.  To rerun Standard 3, aspirate standard and press 3 Calibrate.

 

7) Reslope the standard curve by pressing Reslope after aspirating the designated reslope standard.

 

D) The correlation coefficient should be greater than or equal to 0.990.

 

E) Check the calibration curve for drift, accuracy and precision with standards and controls every 20 samples.

 

IV) Analysis Procedure

 

A) Autozero with the blank before and after each standard, control and sample.

 

B) Aspirate sample and press Read. Wait until Read light goes out.  Record absorbance or concentration value.  Record the five replicate standard deviation.  Rerun the sample if the standard deviation is greater than 10% of the sample result.

 

V) Instrument Shutdown

 

A) Aspirate 5 % concentrated hydrochloric acid (HCl) for 5 minutes and deionized water for 10 minutes to clean the burner head.  Remove the capillary tube from the water.

 

B) Press Flame On/Off to turn off flame.

 

C) Close air compressor valve.

 

D) Close acetylene cylinder valve.

 

E) Press Gases On/Off three times to bleed the acetylene gas from the lines.  The cylinder pressure should drop to zero.

 

F) Power OFF the AAnalyst 100, the printer and the fume hood.