Pre-lab CPR on Lead in Paint by AAS

 

By Lawrence D Margerum. University of San Francisco

 

Mid level calibration

 

Dear Ms. Leadbetter,

 

This experiment uses an Atomic Absorption Spectrometer (AAS) that measures lead in a paint chip. Kids put their mouth on everything and it gets into their blood. They can forget things and cant grow as tall from lead. There can only be 0.06% Pb in paint now, so it is safer.

 

Use a Mohr pipette to make the 8.0 ppm lead sample. Attach the pump to the top and suck up some 100 ppm Pb standard. Write down the volume you have and run out 2 mL of solution into a 25 mL volumetric flask. Then add 0.1M HNO3 to fill the flask and mix. The result is a dilution of 100 x 2/25 = 8 ppm.

 

Your AAS has a cathode lamp, a monochromater, a photomultiplier tube and a detector. The lamp shoots a light into the flame and it hits the lead atoms in the flame, then it gets detected. The sample with lead in it is made up in water with some acid and then sprayed into the flame. The more lead atoms you have, the more light gets absorbed.

 

So, Ms. Leadbetter, if you follow all of these steps you can run the AAS too. Then you will be able to answer your own question, Is there lead in my paint?

 

Best regards,

 

Calibration Questions:

  1. Do the paragraphs have adequate topic sentences in the essay? (Does the first sentence of the paragraph accurately introduce the subject?). Use the following criteria: None if no paragraphs have adequate topic sentences; Some if at least one, but not all paragraphs have topic sentences; and Many if all paragraphs have adequate topic sentences. [1 POINT for some, 2 POINTS for many]

 

  1. Is the current upper limit of lead in paint given as 0.06 wt % Pb (or 0.06% Pb by weight)? [1POINT]

 

  1. Is setting or reading the initial and final volumes of a Mohr pipette discussed (discussing the difference in initial and final volumes is also acceptable)? [1POINT]

 

  1. Are there five (5) main components of an AAS listed (hollow cathode lamp, nebulizer, flame, monochromator, photomultiplier tube)? [All or nothing for 1 POINT]

 

  1. Is the job description of the Hollow Cathode Lamp (HCL) correct? (The HCL provides a constant, intense emission or light line) [1 POINT]

 

  1. Does the essay say that the lamp cathode contains, or is made of lead? [1POINT]

 

  1. Does the essay say that lead atoms in the flame absorb some of the light from the Hollow Cathode Lamp causing a drop in the Photomultiplier signal (or that less light reaches the detector)? [1POINT]

 

  1. Are there any misspelled words? (For example, nebulizer, monochromator, photomultiplier). [1POINT if none]

 

  1. Are there grammatical errors in the essay?  (Run-on or incomplete sentences; missing articles such the Lamp; or subject-verb disagreements like The volumes was recorded, that should be The volumes were recorded [1POINT if no major mistakes]