AOAC OMB Final Action Recommendation (December 2019)-2016.14
2016.14 (October 2019) – FOS-03 METHOD
FOR ERP USE ONLY DO NOT DISTRIBUTE
(m) Sodium chloride solution (1 M) for graphitized carbon SPE column .—Into a 100-mL volumetric flask
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weigh 5.8 g NaCl and dissolve with 90 mL of water. Make up to the mark with water. Stable for 6
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months at room temperature.
(n) Elute solution for graphitized carbon SPE column (TFA 0.05 % in acetonitrile 25 % (v/v)) .—Into a
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100-mL volumetric flask, add 25 mL of acetonitrile and 50 μL of TFA. Make up to the mark with
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water. Stable for 6 months at room temperature.
E.
Mobile Phase Preparation (Using CarboPac PA20 column or Equivalent)
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If using a CarboPac PA1 column (or equivalent), skip this section and go directly to section F . 158
(a) Mobile phase A for CarboPac PA20, sodium hydroxide solution (600 mM).— Into an eluent bottle,
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introduce 970 mL of water C(a) and degas with helium for 20 min. Add (using a single-use plastic
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pipette) 31.2 mL of 50 % (w/w) NaOH solution C(j) . Degas with helium for 20 min and protect the
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eluent from exposure to carbon dioxide until, and during use by suitable means (e.g. by keeping
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under a blanket of helium). Stable for 1 week at room temperature.
(b) Mobile phase B for CarboPac PA20, deionised water resistivity ≥18 MΩ.— Into an eluent bottle,
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introduce 2000 mL of water C(a) and degas with helium for 20 min. Thereafter protect the eluent
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from exposure to carbon dioxide until, and during use by suitable means (e.g. by keeping under a
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blanket of helium). Stable for 4 days at room temperature.
(c) Mobile phase C for CarboPac PA20, sodium hydroxide solution (30 mM).— Into an eluent bottle,
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introduce 1000 mL of water C(a) and degas with helium for 20 min. Add (using a single-use plastic
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pipette) 1.6 mL of 50 % (w/w) NaOH solution C(j) . Degas with helium for 20 min and protect the
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eluent from exposure to carbon dioxide until, and during use by suitable means (e.g. by keeping
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under a blanket of helium). Stable for 1 week at room temperature.
(d) Post-column addition reagent, sodium hydroxide solution (300 mM).— Into an eluent bottle,
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introduce 985 mL of water C(a) and add (using a single-use plastic pipette) 15.6 mL of 50 % (w/w)
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