COuld someone please EXPLAIN the steps? You are tasked with determining the conc
ID: 533531 • Letter: C
Question
COuld someone please EXPLAIN the steps?
You are tasked with determining the concentration of aflatoxin B1 in a sample of suspect milk. There are two problems with directly measuring absorption of these samples: aflatoxin B1 does not readily absorb in the visible region;milk has a lot of components, making itoptically opaque. A recent report showed that gold nanoparticles bind tightly to the toxin, forming a complex that readily absorbs 550 nm photons. Use the following information to determine the concentration of toxin B1 in the milk sample.Explanation / Answer
In order to find the concentration of aflatoxin, first, we have to calculate the extinction coefficient of the gold nanoparticle-aflatoxin at 550 nm. This can be calculated from the rate of change in absorbance with the concentration of aflatoxin. From the given data it is clear that gold nanoparticle-aflatoxin readily absorbs at 550 nm (absorbance got increased from 0.65 to 0.89 ) and it is also given that aflatoxin B1 does not absorb in the visible region.
extinction coefficient = 0.24/(0.5*5) = 0.096 (ng/mL)-1 (pathlength of the cuvette)-1
Milk sample with aflatoxin B1 shows an absorption of 0.65.
using Beer-Lamberts law we can calculate the concentration of aflatoxin B1 in the sample.
absorbance = extinction coefficient * pathlength of the cuvette * concentration of the sample (Let us take path length as 1. Since we are using the same cuvette for both the measurements, it will not affect our result)
0.65 = 0.096 * 1* concentration of the sample
or concentration of the sample = 0.65/0.096 = 6.77 ng/mL
The solution used to measure absorbance has 50 mL it contains 6.77 ng/mL. basically, this came from 25 mL milk thus the milk has double concentration. 13.54 ng/mL