EQUIPMENT

1. Thermo Jarrell-Ash Model 61E ICP
2. Thermo Jarrell-Ash Autosampler 300
3. 48 position rectangular sample racks
4. 20X150 mm test tubes

REAGENT

1. Acetic Acid: CH₃COOH
2. Nitric Acid: HNO₃

STANDARDS

1. Stock Solutions: Use certified, NIST traceable plasma grade standards.
2. Instrument Calibration Standards:
   1. Petiole1 - Pipet the designated volumes of stock solution into a 1 liter volumetric flask. Add 5 mL nitric acid. Dilute to volume with deionized water and mix well.

      Element	Stock Solution Concentration ppm	Stock Solution mL	Final Concentration ppm	Instrument Readout
      P	1000	1	1	200 ppm
      K	10000	6	60	1.20 %
      Ca	1000	15	15	3000 ppm
      Mg	1000	5	5	0.10 %
      Zn	100	2	0.2	40 ppm
      Mn	1000	1	1	200 ppm

   2. Petiole2 - Pipet the designated volumes of stock solution into a 1 liter volumetric flask, Add 5 mL nitric acid. Dilute to volume with deionized water and mix well.

      Element	Stock Solution Concentration ppm	Stock Solution mL	Final Concentration ppm	Instrument Readout
      P	1000	40	40	8000 ppm
      K	10000	20	200	4.00 %
      Ca	10000	15	150	30,000 ppm
      Mg	1000	60	60	1.20 %
      Zn	1000	5	5	1000 ppm
      Mn	1000	20	20	4000 ppm

EXTRACTING SOLUTION

1. 2% Acetic Acid
   1. Add 20 mL acetic acid to a 1 liter volumetric flask containing 600 mL deionized water. Dilute to volume with deionized water and mix well.

EXTRACTION PROCEDURE

1. Weigh 0.100 g cotton petiole into a 20X150 mm test tube.
2. Reweigh each eighth sample and place at the end of the set.
3. Add 20 mL of 2% acetic acid.
4. Shake on a reciprocal shaker for 15 minutes at high speed (250 oscillations per minute)
5. Filter using Whatman #1 paper.

ICP PROCEDURE

1. Follow the manufacturer's instructions in order to initiate the plasma and the autosampler
2. Select PETIOLE from the methods menu.
3. Setup an autosampler table for the set being analyzed.
4. Analyze the samples using the autosampler table.

QUALITY CONTROL

1. Analyze the Petiole2 standard immediately following calibration.
   1. All values must be within 2% of the known values.
2. Analyze the Petiole2 standard immediately following the last client sample.
   1. All values must be within 8% or the known values.

3. Duplicate Samples
   1. The difference between the two values may not vary more than 20 % from the average of the two values.

REFERENCE

1. Baker, A. S., 1971. A simplified method for determining acetic acid soluble phosphorus in plant tissue. Comm. in Soil Sci. and Plant Anal. 2(3):195-200.