RA-4300A High Blanks

RA-4300A High Blanks

The following are the possible causes of high blank values: 
  1. Contaminated reagent or deionized water 
  2. Contaminated reagent bottle or DI bottle 
  3. Contamination inside the instrument 
  4. Rise in the concentration of mercury in the atmosphere (air)
 Carry out the following steps in order to narrow down the cause of the contamination.
 
1.  Measure DI water using normal method settings.  Leave the Stannous at the default amount.
      
      If the blank value is OK, then one of the digestion reagents, not the stannous, and/or the environment are contaminated,       go to step 5.

      If the blank value is still high the problem is with the DI water, stannous chloride, or the cap, proceed to step 2.
 
2.  If the result in Step 1 is not good then empty the DI water from the tube and measure the stannous chloride by filling the test tube with 1 mL of stannous chloride (no DI water) and run the test tube using the same method settings in step 1. 

      If the blank value is good, the problem is the DI water.

      If the blank value is still high, the problem is with the stannous, the cap, the reaction tubing going to the detector, the
      condenser, or the detector, proceed to Step 3.

3.  If the result is not good after step 2, keep the contents in the sample tube, reduce the stannous reagent amount in the software method to "0.0", and rerun the same test tube and solution using the modified method.

      If the blank is good, then it is confirmed that the stannous chloride reagent and the pump tube for the stannous are 
      contaminated. 

      If the blank value is still high, the problem is with the cap, tubing going to the detector, condensor, or the       detector.  Follow each of these procedures to clean the system:

            *Clean the glass dehumidifier in the same solution and at the same time as cleaning the flowcell

4. After reassembling everything; rerun the same tube and solution from step 3.  If the blank is still high it is recommended to       buy a Preventative Maintenance Kit and replace all parts and tubing in the kit.  An AGS Service Technician can perform this       for you as well, to schedule a service visit email support@agssci.com.

5.  If the blank level was Good in Step 1 then it is likely contamination in one of the digestion reagents.  To find out which one, put .5 mL of each reagent in their own individiual sample tubes and put on the autosampler to run as samples.  Change the method to inject .5 mL of Stannous.  The contaminated reagent(s) will produce a peak.

6.  If Step 5 produces no peaks then the contamination is coming from the room air.

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