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### Topic: Limit of Detection  (Read 656 times)

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#### ubcdumbass

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##### Limit of Detection
« on: February 09, 2019, 05:04:28 PM »
(3)An assay method has a simple linear calibration: S = 0.50[A] –2.00, where S is the measured signal(arbitrary units)and [A] is the concentration of analyte in units of micromolar. A blank sample is measured five times and an average signal of 0.50 ±0.50(± one standard deviation) is obtained. What is the limit of detection for the method?

The answer is 8.0 uM. Unsure why as LOD= Smb + zo, wherein the textbook it says z is assumed to be 3 when no other assumptions can be made. (is this true?)
That would give 2.0uM

Could somebody run me through this? Thank you

#### mjc123

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##### Re: Limit of Detection
« Reply #1 on: February 11, 2019, 05:24:45 AM »
Your formula would give 2.0 signal units. Put this into your calibration equation, and you get [A] = 8.0 µM.
« Last Edit: February 11, 2019, 08:32:55 AM by mjc123 »