Methods to be Reviewed by OMB in 2016

(a)

Extraction solution

.—0.2% citric acid [w/v, 40 g/20 L deionized (DI) water].

(b) Polyester fiber (available in fabric or craft stores).

(d) Cupric sulfate solution stabilizer (20 g CuSO4 5H2O/L 1 + 1 HCl).

(e) Calibration standard, 500 mg N/L, matrix-matched to the

liquid extracts for AOAC

993.13

(f) Matrix-matched (–7 + 9 mesh IBDU) internal reference material.

(f) 2% HCl/DI water solution for cleanup of equipment and

tubing.

E. Sample Preparation of Granular Materials

(a)

Homogeneous or blended materials (coated N-P-Ks, granulations, or blends)

.—Reduce via

gated riffle splitter (Jones Micro-Splitter SP-171X; Gilson Co., Inc., Lewis Center, OH) to 30.0 ± 1.0

g unground test portion. Place 3 (±0.2) g fiber 2–3 cm above the bottom of column (do not pack),

and insert PTFE rod (ThermoFisher Scientific, Pittsburgh, PA). Using powder funnel, add test

portion, and place 3 (±0.2) g fiber near top of column below O-ring, but not directly on top of

test portion. Ensure no test portion or fibers foul O-ring seals.

(b)

Pellets, spikes, briquettes, etc

.—If larger than 2.5 cm, crack, crush, or break to yield pieces

as large as possible that fit column (<2.5 cm). Use largest pieces equaling 30.0 ± 1.0 g, and weigh

to ±.01 g. Place 3 (±0.2) g fiber approximately 2–3 cm above bottom of column (do not pack),

insert polyethylene rod, add test portion, place 3 (±0.2) g fiber near top of column, but not on top

of test portion. Ensure no fibers foul O-ring seals.

F. Extraction

Extraction sequence (examples in parenthesis)—

Day 1

.—

Extraction 1

.—2 h at 25°C (e.g., Mon. 9:00 am– 11:00 am).

Extraction 2

.—2 h at

50°C. Begin 1 h following extraction 1 (e.g., Mon. 12:00 pm–2:00 pm).

Extraction 3

.—20 h at

55°C. Begin 1 h following extraction 2 (e.g., Mon. 3:00 pm– 11:00 am Tues.).

Day 2

.—

Extraction 4

.—50 h at 60°C. Begin 1 h following extraction 3 (e.g., Tues. 12:00 pm–2:00

pm Thurs.).

Day 4

.—

Extraction 5 (if needed).—

94 h at 60°C complete extraction 4 (e.g., Thurs. 3:00 pm).

Begin extraction 5 one hour following extraction 4 (e.g., Thurs. 4:00 pm–2:00 pmMon.).

Candidates for 2016 Method of the Year

212