OMB Meeting Book_9-11-14

retention time should be 11 to 13 min (depending on the type of switching valve used and the individual analytical column). ( a ) Concentration of working standards .

Table 2011.18B. PAD settings with gold electrode Analog

range

1 uC

Detector program: Dionex ICS3000 or ICS 5000PED t, s

E,V

C = W  1/0.05  1/10  A /V  A /V

E, V

0.0

0.00

W

1 1

2 2

= W  2  A /V  A /V

0.0 +0.10 + 0. 01 0 0.40 +0.10 0.41 -2.00 0. 52 0

1 1

2 2

0. 4251 + 02 . 80 0

where C

is the concentration of the working standard solution in

W

0. 5943 +0. 86 0

1 2 the dilution volume of the working standard in milliliters; A is the aliquot of working standard used, in milliliters, if applicable; and is the dilution volume of the working standard in milliliters, if a pplicable. ( b ) Preparation of standard curve.— For each working standard concentration, average the peak areas or heights from each two consecutive sets of standards. Prepare a standard curve by performing linear least squares (regression) on the concentrations versus the averaged peak areas or heights. A standard curve must have a correlation of at least 0.999 to be considered acceptable for sample calculations. At each working standard level, the peak areas or heights of standards injected before and after a set of samples must not increase or decrease by more than 7%. ( c ) Calculation of myo-inositol in samples and controls .—The concentration of myo-inositol in a prepared sample or control is extrapolated from the standard curve prepared above. From the diluted, prepared sample concentration, the product concentration can be calculated: where C is the concentration of myo-inositol in the product sample or control in milligrams per kilogram; C is the concentration of myo-inositol in the prepared sample or control in milligrams per liter; D is the dilution volume in milliliters; and S is the sample weight in grams. Note : For each set of samples, the control result must be within 3 standard deviations of the control mean. p d 1 p d 1 A milligrams per liter; W is the weight, in milligrams, of myo-inositol standard weighed; 0.05 is the dilution volume of the stock standard in liters; 1/10 is the intermediate standard dilution (10 to 100 mL); is the aliquot of intermediate standard used, in milliliters; V is 1 V 2 C = (C  D )/S

0. 6044 –0. 71 0

0. 85 0

–0. 71 0

Integration period

0. 23 0–0. 54 0

s

Detector program: Dionex ED 50 with special gold electrode cell SP4270

t, s

E, V

Delete this table. Obsolete

0.0

+0.05

0.2

+0.05

0.4

+0.05

0.41

+0.75

0.6

+0.75

0.61

–0.15

1.0

–0.15

Integration period 0.20–0.40 s

set of standards has been injected, a control sample and up to 14 samples can be injected before another set of standards should be injected. ( 4 ) System shutdown.— After all samples and standards have been analyzed, inject one vial of water to clean out the autosampler needle and tubing. Store the analytical columns in mobile phase [0.12% (30 mM) sodium hydroxide]. Turn off the electrochemical cell. Flush the pump heads with water to remove sodiumhydroxide. Before calculating myo-inositol concentrations in samples, compare the myo-inositol standard peaks with the myo-inositol sample peaks and confirm that there are not any interfering compounds and that the myo-inositol sample peak areas or heights are within the range of the myo-inositol standard peak areas or heights. The concentration of myo-inositol cannot be calculated if there are interferences or if the separation is poor. The myo-inositol F. Calculations

G. Validation Data Note: SLV and MLT data from the ERP checklist will be added to this section. Data tables will be added by September 19.

References: J. AOAC Int . 95 , 937(2012); AOAC SMPR 2011.007, J. AOAC Int . 95 , 295(2012)

© 2012 AOAC INTERNATIONAL