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Chapter 5: Q5P (page 114)

What is the difference between a calibration check and a performance test sample?

Short Answer

Expert verified

In a calibration check, the samples are made by the analysts; thus, the concentrations of the analyte being analyzed is known by the analysts. On the other hand, performance test samples (a.k.a. blind samples, quality control samples) are samples that have unknown concentrations to the analysts, because somebody else has prepared them.

Step by step solution

01

The Calibration Check and Performance Test

Calibration Check:

A calibration check is a study of a solution formulated by the analyst for a known concentration of analyte.

It is the analyst's specific form that instruments and procedures are functioning correctly.

Performance test:

When he or she don't know the right answer the performance test is the used to examine the sample is an analysis of a solution formulated by someone other than analyst to contain a known concentration of analyte.

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Most popular questions from this chapter

Standard addition graph. Tooth enamel consists mainly of the mineral calcium hydroxyapatite,C10PA46OH2. Trace elements in teeth of archeological specimens provide anthropologists with clues about diet and diseases of ancient people. Students at Hamline University used atomic absorption spectroscopy to measure strontium in enamel from extracted wisdom teeth. Solutions were prepared with a constant total volume of 10.0mLcontaining role="math" localid="1667792217398" 0.750mgof dissolved tooth enamel plus variable concentrations of added Sr.

(a) Find the concentration of Sr and its uncertainty in therole="math" localid="1667792593357" 10-mLsample solution in parts per billion =ng/mL.

(b) Find the concentration of Sr in tooth enamel in parts per million =μgg.

(c) If the standard addition intercept is the major source of uncertainty, find the uncertainty in the concentration of Sr in tooth enamel in parts per million.

(d) Find the 95%confidence interval for Sr in tooth enamel.

What is a blank and what is its purpose? Distinguish method blank, reagent blank, and field blank.

How is a control chart used? State six indications that a process is going out of control.

Standard addition graph. Students performed an experiment like that in Figure 5-7 in which each flask contained 25.00mLof serum, varying additions of 2.640MNaCIstandard, and a total volume of 50.00mL.


(a) Prepare a standard addition graph and find [Na+]in the serum.

(b) Find the standard deviation and 95%confidence interval for [Na+].

Detection limit. In spectrophotometry, we measure the concentration of an analyte by its absorbance of light. A low-concentration sample was prepared and nine replicate measurements gave absorbances of 0.0047,0.0054,0.0062,0.0060,0.0046,0.0056,0.0052,0.0044, and 0.0058. Nine reagent blanks gave values of 0.0006,0.0012, 0.0022,0.0005,0.0016,0.0008,0.0017,0.0010, and 0.0011.

a) Find the absorbance detection limit with equation 5-3.

b) The calibration curve is a graph of absorbance versus concentration. Absorbance is a dimensionless quantity. The slope of the calibration curve is m=2.24x104M-1Find the concentration detection limit with Equation 5-5.

(c) Find the lower limit of quantitation with Equation 5-6.
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