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
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