Question

Eight absorbance readings from replicate caffeine samples with a concentration approximately three times the estimated detection limit are 0.123 9,0.1098, 0.118 2, 0.115 0, 0.121 9,0.125 1, 0.119 9, and 0.109 9. The average absorbance of eight reagent blanks is 0.018 2. The slope of the calibration curve for higher concentrations is 0.590 mM!. What is the detection limit?

Answer 1

The standard deviation is 0.0064 mM and the detection limit is 0.0348 mM.

It looks like you've provided the calculations for determining the detection limit of a method, specifically for caffeine samples.

The formula you've provided is a common approach to calculate the detection limit based on the standard deviation of blank absorbance readings.

Let me summarize the information you've given:

Standard Deviation of Blank Absorbance:

Standard Deviation = 0.0064 mM

Blank Absorbance:

Blank Absorbance is not explicitly provided in your information. If you have this value, you'll use it in the calculation.

Detection Limit:

Detection Limit = 3× Standard Deviation + Blank Absorbance 3×Standard Deviation + Blank Absorbance

Detection Limit = 3×0.0064 +Blank Absorbance 3×0.0064+Blank Absorbance

You mentioned the detection limit is 0.0348 mM.

If you have the blank absorbance value, you can substitute it into the formula to calculate the detection limit.

If not, you may need to check your data or experiments to obtain the blank absorbance.