# Bracket Standard Recovery

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I'm attempting to create a CF for bracket standard recovery during HPLC runs, the calculation (as outlined in our SOP's) is as follows:

% Recovery =[|A-B| x 2/ (A+B)] x 100

Where:

A:        Mean area response of standard prior to the samples

B:        Mean area response of standard after the samples

Is this field possible to create ? i cant seem to have any luck here .

• edited February 2020
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How many times are your standards injected, both before and after samples? Also how many sets of standards are run in a typical run? Do you quantitate all your samples off the one calibration curve or do you do bracket recovery with overlap i.e. S0101 and S0201 used to quantify U0101...then S0201 and S0301 used to quantify U0201..etc?
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its usually two injections of standard between samples ( with the exception of the first set of suitability standards which is 6 injections)
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Ok thanks and how many bracket sets do you run per set of samples? Is it all the one curve or do you set up standards to bracket as sliding with overlap as per my last post?
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The bracket sets vary anywhere from one set of brackets up to 10+ at times. we generally use  one curve  ( the six suitability standard injections) to quantitative unknowns
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That's tricky because I cant think of a label system which wont affect the order in which you run the standards, the label for "after" is going to overlap with the next set of samples and be the "before". I would advise you to set up a Peak, Enum CF on Standards only, Use as Field and pick your max amount of standards run, for example 20. Label them S1 to S20. The formula then becomes ENUM(EQ(Label,"S1"),EQ(Label,"S2"),...up to EQ(Label,"S20")). For the first label translation table (position 0), enter N/A. For the second argument (EQ(Label,"S2") enter a formula in translation table: (((ABS(S1.%..AVE(Area)-S2.%..AVE(Area)))*2)/((S1.%..AVE(Area)+S2.%..AVE(Area))))*100 (fc). Its important to add a space and then (fc) in order for this field to be translated. Then for EQ(Label,"S3"), the formula becomes: (((ABS(S2.%..AVE(Area)-S3.%..AVE(Area)))*2)/((S2.%..AVE(Area)+S3.%..AVE(Area))))*100 (fc). And so on...a quick way to create these formulas is to type the first one out on Notepad then paste it into the other translations, editing it to change label, ie S3, S4 etc.

Long winded I know but I cant see another way of doing this.