PRINCIPLE

  1. In normal ICP operation, the probe is in the sample being analyzed. With this configuration, there is an approximate 17 second period after the analysis is completed that the sample is still being pumped through the instrument. By using the instrument command language to control the instrument, it is possible to take advantage of this 17 second period and significantly improve the speed of analysis with no loss in sensitivity or accuracy.
  2. In the resultant system, the position of the probe is one sample behind the sample being analyzed. Since the instrument software will not recognize sample n–1, the automatic sequencing of sample numbers and checking of limits for check standards and quality control samples can not be used. It is therefore necessary to manually check these samples for limits in order to determine data acceptability.

EQUIPMENT

  1. Thermo Jarrell–Ash Model 61E ICP
  2. Thermo Jarrell–Ash Autosampler 300
  3. 48 position rectangular sample racks

ICP PARAMETERS

  1. Sample Time: 21 seconds
  2. Sample Rate: 171/hour
  3. Sample uptake time: 19 seconds
  4. Units: lbs/acre
  5. Integration Time: 4.0 seconds
  6. Flush Time: 0 seconds
  7. Background Correction: No
  8. Blank Correction: No
  9. Torch Gas: High Flow
  10. Auxiliary Gas Flow: Low (0.5L/min)
  11. Nebulizer Flow(L/min): 0.651 (adjustable)
  12. Approximate RF Power(W): 950
  13. Analysis Pump Rate: 50–130 RPM (adjustable)
  14. Flush Pump Rate: 50–130 RPM (adjustable)
  15. Pump Tubing Type: Tygon–Red
  16. Purge: On

ICP WAVELENGTHS

  1. P 1782
  2. K 7664
  3. Ca 3179
  4. Mg 2790
  5. Zn 2138
  6. Mn 2576

STANDARDS

  1. Stock Solutions: Use certified, NIST traceable single element plasma grade standards.
    1. P 1000 ppm
    2. K 1000 ppm
    3. Ca 1000 ppm
    4. Ca 10,000 ppm
    5. Mg 1000 ppm
    6. Mn 1000 ppm
    7. Zn 1000 ppm
    8. Zn 100 ppm
  2. Instrument Calibration Standards: Pipet the designated mL of stock solution into a 1 liter volumetric flask. Dilute to volume with deionized water and mix well.
    1. SOL 1 standard

      Final Instrument

      Stock Concentration Readout

      Element Solution mL ppm lbs/acre
      P 1000 ppm 1 1 8
      K 1000 ppm 6 6 48
      Ca 1000 ppm 15 15 120
      Mg 1000 ppm 5 5 40
      Mn 1000 ppm 1 1 8
      Zn 100 ppm 2 0.2 1.6
    2. SOL 3 standard

      Final Instrument

      Stock Concentration Readout

      Element Solution mL ppm lbs/acre
      P 1000 ppm 40 40 320
      K 1000 ppm 20 20 160
      Ca 10,000 ppm 15 150 1200
      Mg 1000 ppm 20 20 160
      Mn 1000 ppm 20 20 160
      Zn 1000 ppm 5 5 40

PRELIMINARY ICP STARTUP PROCEDURE

  1. Turn on the following:
    1. Exhaust fan
    2. Water pump
    3. Computer
    4. Video screen
    5. Printer
  2. Engage the pump platens
  3. Set the two flow meters of the right side of the torch compartment to mid range.

ANALYSIS OF SOILS USING THE SOIL180 COMMAND FILE

  1. Initiate the plasma
    1. Using the mouse, click on the thermospec icon.
    2. Using the arrow keys, go to SETUP on the thermospec menu and select PLASMA CONTROL PANEL, press ENTER.
    3. Press F1 (startup).
    4. Press F9 (continue) – the plasma will ignite in approximately 90 seconds.
    5. Press ESC in order to return to the thermospec menu.
  2. Select method
    1. Using the arrow keys, go to OPERATION on the thermospec menu and select ANALYSIS, press ENTER.
    2. Type SOIL180 at the ENTER METHOD NAME prompt, press ENTER – the computer will automatically set the ICP parameters for SOIL180 method.
    3. Allow the instrument to warm up for 30 minutes before beginning analyses.
  3. Initiate the autosampler
    1. Turn the autosampler on.
    2. If the auto sampler is already on, turn it off and then on again.
    3. Type IARA, press ENTER
    4. If a red message box appears, press ENTER and repeat step 3c.
  4. Set sample uptake time
    1. Go to DEVELOPMENT on the main menu. Select METHODS, press ENTER.
    2. Type SOIL180 at the ENTER METHOD NAME prompt.
    3. Press F6 (plasma info)
    4. Using the arrow keys, go to ANALYSIS PUMP RATE (RPM)
    5. Set the pump rate according to the following formula (present pump rate × present uptake time) ÷ 19 = new pump rate.
    6. Set the FLUSH PUMP RATE to equal the ANALYSIS PUMP RATE.
    7. Press F9 (done/keep) twice in order to accept the method changes and return to the main menu.
  5. Standardization and sample analysis
    1. Place a SOL 1 low calibration standard in position #10 of the L shaped rack.
    2. Place a SOL 3 high calibration standard in position #11 of the L shaped rack.
    3. Place the poured up rectangular sample rack in the proper position on the autosampler.
    4. Repeat step 2 in order to select SOIL180 method
    5. Type XC"SOIL180" at the COMMAND prompt, press ENTER.
    6. Respond to the screen prompts and type the number of samples, first sample #, and set identification. The first sample # must be followed by a period. After each entry press ENTER.
    7. Standardization and analysis of the set will begin after the last ENTER is pressed.
  6. Quality control
    1. At the end of the analysis of each soil set, from the DAILY menu, click on REPORTS and then click on SOIL. Using the mouse, scroll to the QC data. Inspect the data to insure that it meets all QC criteria.
    2. After the last soil set has been analyzed, from the DAILY menu click on REPORTS, then click on SOIL, then click on PRINT. The printer will print all of the days data including the quality control samples in a condensed form.
    3. File the sample data and place the QC data in the notebook provided.
  7. Operating notes
    1. Steps 1 (Initiate Plasma), 3 (Initiate Autosampler), and 4 (Set sample uptake rate) are done at the beginning of the day and do not need to be repeated.
    2. Step 3 (Initiate Autosampler) can only be done after a method has been selected (Step 2).
    3. Step 4 should be omitted if the sample uptake time is 19 seconds.
    4. If the new pump rate calculated in section 4e is outside the range of 70–130 rpm, replace the red tygon pump tube.

DATA TRANSFER

  1. Using the mouse click on DAILY.
  2. Transfer good data to data processing (done once a day after the last soil set hasbeen analyzed).
    1. From the DAILY menu, using the mouse, under PUTDATA, click on SOIL
  3. Delete bad data if necessary (done on a single set because of failure to meet quality control criteria).
    1. Using the mouse click on EDIT
    2. Simultaneously press ALT and L
    3. Use the arrow keys to highlight the data to be deleted, press DELETE.
    4. Simultaneously press ALT and W – the computer will display WRITE SUCCESSFUL.
    5. Simultaneously press ALT and X in order to complete the deletion.

QUALITY CONTROL

  1. CHECK SOIL SAMPLE:
    1. The values for all elements must lie within limits established by the extension chemist.
  2. CALIBRATION CHECKS
    1. SOL 1 low calibration standard – values should be within 8% of the known values.
    2. SOL 3 high calibration standard – values should be within 8% of the known values.
  3. REDIP SAMPLES
    1. If the average of the two analyses for any element is equal to or more than 100 lbs/acre, the results should agree within 20%, according to the following formula:
      (value 1 – value 2) ÷ average value × 100
      where value 1 is the higher value
    2. If the average of the two analysis for any element is less than 100 lbs/acre, the values should agree within 15 lbs/acre.
    3. If the criteria in steps 3a and 3b are not met for two or more of the elements, for either of the redipped samples, the set must be redipped and analyzed again.
  4. STOCK SOLUTIONS
    1. The extension chemist is responsible for procuring, assigning bottle numbers, and maintaining certificates of analysis for each of the stock solutions.

INSTRUMENT SHUTDOWN

  1. Using the arrow keys, go to SETUP on the main menu and select PLASMA CONTROL PANEL, press ENTER.
  2. Press F7 (shutdown) – the plasma will shut down in approximately 30 seconds.
  3. Turn off the following:
    1. Exhaust fan
    2. Water pump
    3. Computer
    4. Video Screen
    5. Printer
  4. Disengage the pump platens.
  5. Turn the flow meter closest to the front of the instrument off.
  6. Reduce the flow rate of the flow meter closest to the rear of the instrument to a tenth of full scale.

REFERENCES

  1. Isaac, R. A. and W. C. Johnson. 1983. High speed analysis of agricultural samples using inductively coupled plasma–atomic emission spectroscopy. Spectrochemica Acta. 38B: 277–282.
  2. Munter, R. C. and R. A. Grande. 1981. Plant tissue and soil extract analysis by ICP–atomic emission spectroscopy. In R.M. Barnes (ed). Developments In Atomic Plasma Analysis. 653–672.
  3. Soltanpour, P. N. and S. M. Workman. 1981. Use of inductively–coupled plasma spectroscopy for the simultaneous determination of macro– and micronutrients in NH4HCO3–DPTA extracts of soils. In R. M. Barnes (ed). Developments In Atomic Plasma Analysis. 673–680.