6. AOACSPIFANMethods-2018Awards

262

Standard

TRP Stock Sol.

Int. Std. Stock

Very Low

0.2 mL

0.5 mL

LOW

1.0 mL

0.5 mL

MID

5.0 mL

0.5 mL

HIGH

10.0 mL

0.5 mL

Add 12.0 mL of methanol to each of the flasks containing the standard/internal standard mixtures, and bring to volume with Laboratory Water. Transfers diluted standards to autosampler vials as needed and freeze the balance in plastic bottles for later use. Storage: keep frozen. Expiration date: 6 months.

g) Mobile Phase: (18:82, Methanol: 0.05 M Buffer, pH 2.3)

Dissolve 6.9 ± 0.1 grams of sodium phosphate monobasic and quantitatively transfer with water to a beaker containing approximately 900 mL of Milli-Q water. Add 2.0 mL of concentrated phosphoric acid (85%) with a class “A” volumetric pipet while stirring. This should adjust the pH to 2.3. Transfer to a 1 liter volumetric flask and dilute to volume with water. Filter the buffer solution through a 0.45 micron filter. Transfer about 500 mL of the filtered buffer into a 1 liter volumetric flask. Add 180 mL of Methanol and swirl to mix. Allow to degas, then dilute to volume with more filtered buffer. Discard excess buffer. Mix flask contents thoroughly and transfer to a 1 liter HPLC system reagent reservoir.

Storage: Room temperature. Expiration date: Six (6) weeks (in capped bottle). Volumes and weight may be varied proportionately for larger yield.

h) Column Rinse Solution:

Prepare a maintenance solution of approximately 25% methanol in water to use as a system rinse following each analysis run. Change maintenance solutions a minimum of every 3 months.

E. Sample Preparation

a) Set heating unit to 50°C prior to experiment. b) Using an analytical balance, tare a 50 mL centrifuge tube.

c) Weigh liquid samples and reconstituted powders directly into tarred centrifuge tubes using a disposable transfer pipette. For non-reconstituted powder samples weigh into a tarred tube with a spatula. Record weights.