5. Forensic Chemistry and Toxicology

Quantitative Analysis — Quiz

Test your understanding of quantitative analysis with 5 practice questions.

Practice Questions

Question 1

Which primary advantage does an internal standard calibration approach offer over an external calibration approach?

Question 2

In a standard addition calibration, if the slope of the standard addition plot is 20\\% lower than that of the external calibration plot, this indicates what matrix effect?

Question 3

For a forensic method with a blank standard deviation $\sigma_{blank}=0.05\,\mathrm{mg/L}$ and a calibration slope $S=1000\,\mathrm{counts/(mg/L)}$, what is the limit of quantitation LOQ if defined as $\mathrm{LOQ}=\frac{10\,\sigma_{blank}}{S}$?

Question 4

Given independent uncertainty components $u_1=0.04\,\mathrm{mg/L}$, $u_2=0.03\,\mathrm{mg/L}$, and $u_3=0.02\,\mathrm{mg/L}$, what is the expanded uncertainty $U$ at approximately 95\\% confidence using a coverage factor $k=2$?

Question 5

A mid-level calibration check standard of nominal concentration $10\,\mathrm{mg/L}$ yields a back-calculated concentration of $9.6\,\mathrm{mg/L}$. What is the percent recovery, and is it acceptable if the acceptance criterion is 90\\%–110\\%?