Methods to be Reviewed by OMB in 2016

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Table 2015.18C. Calibration criteria for “direct-available” P and “soluble” K by ICP-OES
Element ID Wavelength, nma Calibration range, μg/mL Standards used (see Table 2015.18A)Curve fit Spectral deconvolution
P 177.434 (1) 0 to 100 Blank, 1, 2, 3, 4 Linear None
P 177.434 (2) 100 to 500 4, 5, 6, 7, 8, 9 Linear None
P 178.222 (1) 0 to 100 Blank, 1, 2, 3, 4 Linear None
P 178.222 (2) 100 to 500 4, 5, 6, 7, 8, 9 Linear None
P 213.618 (1) 0 to 100 Blank, 1, 2, 3, 4 Linear Cu 213.598
P 213.618 (2) 100 to 500 4, 5, 6, 7, 8, 9 Linear Cu 213.598
P 214.914 (1) 0 to 100 Blank, 1, 2, 3, 4 Linear Cu 214.898
P 214.914 (2) 100 to 500 4, 5, 6, 7, 8, 9 Linear Cu 214.898
K 766.485 (1) 0 to 126 Blank, 1, 2, 3, 4 Quadratic None
K 766.485 (2) 50 to 379 3, 4, 5, 6, 7 Quadratic None
K 769.897 126 to 505 4, 5, 6, 7, 8 Quadratic Interference LiNO3
K 404.721 505 to 1046 8, 9, 10, 11, 12 Quadratic None
a (1) and (2) distinguish between the same wavelength used to cover two separate concentration ranges.
Table 2015.18D. Final ICP-OES conditions utilized for citrate-EDTA-soluble P and K validation
Factor Setting
Power, kW 1.45
Plasma flow, L/min 19.5
Auxiliary flow, L/min 2.25
Nebulizer pressure, L/min 0.7
Nebulizer type Seaspray
Spray chamber Cyclonic
Sample pump tube Black/black
Buffer/internal standard pump tube Gray/gray
CsCl ionic buffer concn, M 0.018
Internal standard and concn, µg/mL 10
Buffer matrix 4% nitric acid
Exposure length, s 10
Number of exposures 3
Rinse time, s 35
Total analysis time, min 2
Candidates for 2016 Method of the Year
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