Question

Low concentrations of Ni-EDTA near the detection limit gave the following counts in a mass spectral measurement: 100., 160., 160., 184, 172,120., 196, 139, 156, 175. Ten measurements of a blank had a mean of 45 counts. A sample containing 1.00 µM Ni-EDTA gave 1797 counts.

(a) Find the mean.
counts

(b) Find the standard deviation.
counts

(c) Estimate the detection limit for Ni-EDTA.
counts
M

Answer 1

In the following table are the data for the average and the standard devation

Counts	Blank	Count-Blank
100	45	55
160	45	115
160	45	115
184	45	139
172	45	127
120	45	75
196	45	151
139	45	94
156	45	111
175	45	130
	Average	111.2
	Standard Devation	29.352

For the detection limit, You can calculate the concentration in the samples using the concentration of the kown sample:

	1uM	1797 counts
Detection limit	0.063 uM	111.2 counts (from the mean)