Chapter 5: Q2P (page 114)
What are the three parts of quality assurance? What questions are asked in each part and what actions are taken in each part?
The three parts of quality assurance are objectives, specifications and assessment.
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Olympic athletes are tested to see if they are using illegal performance-enhancing drugs. Suppose that urine samples are taken and analyzed and the rate of false positive results is 1 %. Suppose also that it is too expensive to refine the method to reduce the rate of false positive results. We do not want to accuse innocent people of using illegal drugs. What can you do to reduce the rate of false accusations even though the test always has a false positive rate of 1 %?
Correlation coefficient and Excel graphing. Synthetic
data are given below for a calibration curve in which random Gaussian
noise with a standard deviation ofwas superimposed on
y values for the equation
. This exercise shows that
a high value of
does not guarantee that data quality is excellent.
(a)Enter concentration in column A and signal in column B of a
spreadsheet. Prepare an XY Scatter chart of signal versus concentration
without a line as described in Section
. Use LINEST
(Section 4-7) to find the least-squares parameters including
.
(b)Now insert the Trendline by following instructions on page 88.
In the Options window used to select the Trendline, select Display
Equation and Display R-Squared. Verify that Trendline and LINEST
give identical results.
(c)Add confidence interval y error bars following the instructions
at the end of Section 4-9. The
confidence interval is 6tsy,
where
comes from LINEST and Studentโs tcomes from Table 4-4
forconfidence and
degrees of freedom. Also, compute
t with the statement .
What is a blank and what is its purpose? Distinguish method blank, reagent blank, and field blank.
1.00 mL of blood serum was diluted to 25.00 mL in each flask of a standard addition experiment like Figure 5-7 to measure a hormone with a molecular mass of 373 g/mol. The x-intercept of the graph was 4.2 ppb (parts per billion). Find the concentration of hormone in the serum and express your answer in ppb and molarity. Assume that the density of serum and all solutions is close to 1.00 g/mL
Chloroform is an internal standard in the determination of the pesticide DDT in a polarographic analysis in which each compound is reduced at an electrode surface. A mixture containing chloroform andDDT gave signals offor chloroform andfor DDT. An unknown solutioncontaining DDT was placed in avolumetric flask andof chloroform (FM 119.39, densitywere added. After dilution to the mark with solvent, polarographic signals of andwere observed for the chloroform and DDT, respectively. Find the concentration of DDT in the unknown.
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