4. The detection limit in our method of quantification for serotonin is at 1.763pg. We must inject a volume of 20µl. What minimum sample concentration can we measure?
From the setup we know that we can detect 1.763pg 5HT in 20µl. Concentrations are given as weight per volume, so in this example we are provided with a concentration and we just need to calculate the molarity of this concentration. Recall the definition of molar concentrations. We need to calculate how much substance there would be in 1 liter of this concentrations. To do this we can:
|
1.763pg 5-HT |
20µl |
|
8.815pg 5-HT |
100µl |
|
88.15pg 5-HT |
1ml |
|
88.15ng 5-HT |
1l |
1 liter of this concentration would contain 88.15ng of 5-HT
176.3ng / liter makes a 1 nM (i.e. a 1x10<sup>-9</sup>M) solution. 88.15ng is half of that so if we use a 20µl sample loop on our HPLC we can measure down to 0.5 x 10<sup>-9</sup>M solutions.
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