AOAC OMB Final Action Recommendation (December 2019)-2016.14

2016.14 (Jan. 2019) FOS-03 MLT Report FOR ERP USE ONLY DO NOT DISTRIBUTE

I. Chromatographic Conditions (using PA20) If using a CarboPac PA1 column (or equivalent), skip this section and go to section J. The HPAEC-PAD system is equipped with a CarboPac PA20 (3 × 150 mm, 6.5 µm) analytical column, or equivalent. The column is held at 30 °C and the injection volume is 25 µL. Sodium hydroxide (300 mM) is added post-column (before the PAD detector) at a flow rate of 0.2 mL/min, using a T-piece and a 125-µL reaction coil (or equivalent). Fructose and glucose are separated using the gradient described in Table 2016.14C . Carbohydrates are detected by pulsed amperometry using a gold working electrode and Ag/AgCl reference electrode, and an appropriate waveform for the detection of carbohydrates. An example of a suitable waveform is given in Table 2016.14D .

Table 2016.14C. HPAEC-PAD gradient for PA20 analytical column (or equivalent)

Flow rate, mL/min

600 mM NaOH, % A

Water, % B

30 mM NaOH, % C

Time, min

0.0

0.5 0.5 0.5 0.5 0.5 0.5

0 0

80 80

20 20

17.0 17.1 27.0 27.1 33.0

100 100

0 0

0 0

0 0

80 80

20 20

Table 2016.14D. Example of quadruple waveform for carbohydrate detection Time, s Voltage, V Gain region 0.00 + 0.10 Off 0.20 + 0.10 On 0.40 + 0.10 Off 0.41 - 2.00 Off 0.42 - 2.00 Off 0.43 + 0.60 Off 0.44 - 0.10 Off 0.50 -0.10 Off