EQUIPMENT

1. Atomic Absorption Spectrophotometer
2. Autosampler
3. Hollow Cathode lamps or electrodeless discharge lamps

STANDARDS

1. Stock Solutions: Use NIST traceable single element atomic absorption grade standards.

   K	1000 ppm
   Ca	1000 ppm
   Mg	1000 ppm
   Zn	100 ppm
   Mn	1000 ppm

2. Instrument Calibration Standards: Pipet the designated aliquots of stock solution into 1 liter volumetric flasks. Dilute to volume with deionized water and mix well.
   1. Potassium:

      Standard #	Stock Solution mL	Final Concentration ppm	Instrument Readout lbs/acre
      1	6	6	48
      2	10	10	80
      3	30	30	240
      4	50	50	400

   2. Calcium:

      Standard #	Stock Solution mL	Final Concentration ppm	Instrument Readout lbs/acre
      1	30	30	240
      2	60	60	480
      3	90	90	720
      4	150	150	1200

   3. Magnesium:

      Standard #	Stock Solution mL	Final Concentration ppm	Instrument Readout lbs/acre
      1	5	5	40
      2	15	15	120
      3	30	30	240
      4	50	50	400

   4. Zinc:

      Standard #	Stock Solution mL	Final Concentration ppm	Instrument Readout lbs/acre
      1	2	0.20	1.6
      2	5	0.50	4.0
      3	10	1.00	8.0
      4	20	2.00	16.0

   5. Manganese:

      Standard #	Stock Solution mL	Final Concentration ppm	Instrument Readout lbs/acre
      1	2	2	16
      2	5	5	40
      3	10	10	80
      4	20	20	120

PROCEDURE

1. Rotate the burner head 45^o to the incident light beam for all analysis.
2. Use a nitrous oxide burner head for calcium analysis.
3. Follow the procedures given in the instrument manual in order to set the proper lamp current and light the flame.
4. Calibrate the instrument using the instrument calibration standards, following the procedures given in the instrument manual.
5. Analyze the Mehlich I extracts on the atomic absorption spectrophotometer.
6. Analyze samples, quality control sample, calibration checks and redipped samples in the same order as that given for the ICP Soil 180 method for extractable P, K, Ca, Mg, Zn, and Mn, page 10.

QUALITY CONTROL

Use the same quality control parameters as those given for the ICP method for extractable P, K, Ca, Mg, Zn, and Mn, page 16.

NOTES

1. K, Mg, Zn, and Mn are analyzed using an air-acetylene flame.
2. Ca is analyzed using a nitrous oxide-acetylene flame.
3. Multi-element hollow cathode lamps are acceptable.
4. Electrodeless discharge lamps are available only as single element lamps.

REFERENCE

1. Isaac, R.A. and J. O. Kerber.1971. Atomic Absorption and Flame Photometry: Technique and Uses in Soil, Plant and Water Analysis. In L. M. Walsh (ed) Instrumental Methods of Analysis of Soils and Plant Tissue. Soil Sci. Soc. Amer., Madison, Wisconsin, pp17-37.