Methods to be Reviewed by OMB in 2016

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riffling down to collect an approximate 100 g subsample. The entire 100 g subsample is ground
[Alternative A, A (h )] to pass a 0.75 mm mesh screen. The ground analytical sample is placed
into a 1 qt (0.946 L) glass jar and mixed by careful rotation and inversion. Use a coring device or
spoon to transfer sufficient mass to fill a 3 oz (90 mL) glass jar approximately half full. For liquid
materials, shake the laboratory sample vigorously to ensure thorough mixing, and then pour
sufficient volume into a 3 oz. (90 mL) glass jar to fill it approximately half full. Test portions for
analyses are taken from the 3 oz (90 mL) jar after inverting and rotating the jar to ensure
contents are thoroughly mixed. Other validated sample preparation techniques that result in a
representative and homogeneous test portion are also acceptable.
E. Extraction
Weigh a 0.5 ± 0.01 g prepared fertilizer test portion (Alternative A, D) and completely
transferred to a 250 mL wide-mouth class A volumetric flask. Dispense 100 mL of 65 ± 2°C
preheated citrate– EDTA extraction solution [Alternative A, B ( m)] into each flask and insert a
rubber stopper. Shake test solutions in a 65 ± 2°C preheated water bath set to approximately
200 reciprocations per minute for exactly 60 min; then remove from the water bath, allow to
cool to room temperature (20 to 25°C), bring to volume with deionized (or equivalent) water,
stopper, and mix. Filter any test solution containing suspended debris using P and K free filters.
Due to a very limited shelf life, analyze test solutions within 16 h of extraction.
F. ICP Conditions
The optimal instrument conditions identified during method validation of citrate–EDTA-
soluble P and K are listed in Table 2015.18D. Monitor rinse time and buffer concentration
closely as they are sensitive to change (1).
ICP-OES differ in their design and options, so minor adjustment to the conditions listed in Table
2015.18D may be necessary; however, any adjustments to these conditions must be
performance based and validated. Special attention should be paid to the recovery of
phosphorus in fertilizer concentrates such as MESZ TM (40% P2O5), DAP (46% P2O5) and MAP
(50% or 52% P2O 5) since these materials pose the greatest need for optimal instrument
performance.
G. Calculations (Alternative A)
Candidates for 2016 Method of the Year
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