EQUIPMENT

1. Thermo Jarrell-Ash Model 61E ICP
2. Thermo Jarrell-Ash Autosampler 300
3. Rectangular autosampler trays
4. 30 mL porcelain crucibles
5. Muffle furnace
6. Hot plate

REAGENTS

1. 25% HCl
   1. Add 250 mL hydrochloric acid to a 1 liter volumetric flask containing 600 mL deionized water. Dilute to volume with deionized water and mix well.

STANDARDS

1. Stock Solutions - Use 1000 ppm, certified, NIST traceable plasma grade standards.
2. Instrument Calibration Standards
   1. FED1 - Pipet the designated amounts of 1000 ppm standard into a 1 liter volumetric flask. Add 5 mL of nitric acid. Dilute to volume with deionized water and mix well.

      Element	Stock Solution mL	Final Concentration ppm	Instrument Readout %
      P	10	10	0.25
      K	20	20	0.50
      Ca	10	10	0.25
      Mg	10	10	0.25

   2. FED2 - Pipet the designated amounts of stock solution into a 1 liter volumetric flask. Dilute to volume with deionized water and mix well.

      Element	Stock Solution mL	Final Concentration ppm	Instrument Readout %
      P	40	40	1.00
      K	60	60	1.50
      Ca	150	150	3.75
      Mg	60	60	1.50
      			ppm
      Mn	1	1	250
      Fe	1	1	250
      Al	1	1	250
      B	1	1	250
      Cu	1	1	250
      Zn	1	1	250
      Na	1	10	2500

      \

DIGESTION PROCEDURE

1. Weigh 1.00 g of feed sample into a 30 mL porcelain crucible.
2. Ash in a muffle furnace for 4 hours an 500 degrees C.
3. Remove the sample from the furnace and let cool.
4. Wet the sample with 10 drops of deionized water.
5. Add 10 mL of 25% hydrochloric acid and swirl for 30 seconds.
6. Place a watch glass over the crucible and put on a hot plate heated to 120 degrees C.
7. Boil the sample gently for 10 minutes.
8. Remove the crucible from the hot plate and let cool.
9. Using a funnel, transfer the solution into a 250 mL volumetric flask.
10. Dilute to volume with deionized water and mix well.

REFERENCE

1. AOAC Official Method 968.08Da in Official Methods of Analysis of AOAC International. 16th edition. chapter 4. p. 23.