Exploring Chemical Analysis: Quality Assurance and Calibration Methods Flashcards


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Definitions and formulas.
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1

What is the definition of an assessment?

In quality assurance, the process of (1) collecting data to show that analytical procedures are operating within specified limits and (2) verifying that final results meet use objectives.

2

What is the definition of a calibration check?

In a series of analytical measurements, a calibration check is an analysis of a solution formulated by the analyst to contain a known concentration of analyte. It is the analyst’s own check that procedures and instruments are functioning correctly

3

What is the definition of a control chart?

A graph in which successive observations of a process are recorded to determine whether the process is within specified control limits.

4

What is the definition of a detection limit?

The smallest quantity of analyte that is “significantly different” from a blank. The detection limit is often taken as the mean signal for blanks plus three times the standard deviation of a low- concentration sample. Also called lower limit of detection

5

What is the definition of a dynamic range?

The range of analyte concentration over which a change in concentration gives a change in detector response. ie oncentration range over which there is measurable response

6

What is the definition of a field blank ?

A blank sample exposed to the environment at the sample collection site and transported in the same manner as other samples between the lab and the field

7

What is the definition of an internal standard?

A known quantity of a compound other than analyte added to a solution containing an unknown quantity of analyte. The concentration of analyte is then measured relative to that of the internal standard.

8

What is the definition of a linear range?

The concentration range over which the change in detector response is proportional to the change in analyte concentration. ie concentration range over which calibration curve is linear

9

What is the definition of a lower limit of quantitation?

Smallest amount of analyte that can be measured with reasonable accuracy. Usually taken as 10 times the standard deviation of a low-concentration sample.

10

What is the definition of a matrix?

The medium containing analyte (that is, everything in a sample other than the analyte). For many analyses, it is important that standards be prepared in the same matrix as the unknown

11

What is the definition of a matrix effect?

A change in analytical signal caused by anything in the sample other than analyte.

12

What is the definition of a method blank?

A sample without deliberately added analyte. The method blank is taken through all steps of a chemical analysis, including sample preparation. See also reagent blank

13

What is the definition of a method validation?

The process of proving that an analytical method is acceptable for its intended purpose

14

What is the definition of a performance test sample?

In a series of analytical measurements, a performance test sample is inserted to see whether the procedure gives correct results when the analyst does not know the right answer. The performance test sample is formulated by someone other than the analyst to contain a known concentration of analyte. Also called a quality control sample or blind sample

15

What is the definition of a quality assurance?

Practices that demonstrate the reliability of analytical data.

16

What is the definition of a range?

The difference between the highest and lowest values in a set of data. Also called spread. With respect to an analytical method, range is the concentration interval over which linearity, accuracy, and precision are all acceptable.

17

What is the definition of a reagent blank?

A solution prepared from all of the reagents except analyte. The blank measures the response of the analytical method to impurities in the reagents or any other effects caused by any component other than the analyte. A reagent blank is similar to a method blank, but it has not been subjected to all sample preparation procedures.

18

What is the definition of a reporting limit?

Concentration below which regulations dictate that an analyte is reported as “not detected.” The reporting limit is typically set 5 to 10 times higher than the detection limit

19

What is the definition of a response factor, F?

The relative response of a detector to analyte (X) and internal standard (S): (signal from X)/[X] = F(signal from S)/[S]. Once you have measured F with a standard mixture, you can use it to find [X] in an unknown if you know [S] and the quotient (signal from X)/ (signal from S

20

What is the definition of a robustness?

The ability of an analytical method to be unaffected by small changes in operating conditions.

21

What is the definition of a selectivity?

The capability of an analytical method to distinguish analyte from other species in the sample. Also called specificity.

22

What is the definition of a sensitivity?

The magnitude of instrument response per unit change in concentration of analyte

23

What is the definition of a specifications?

In quality assurance, specifications are written statements describing how good analytical results need to be and what precautions are required in an analytical method

24

What is the definition of a spike?

Addition of a known compound (usually at a known concentration) to an unknown. In isotope dilution mass spectrometry, the spike is the added, unusual isotope. Spike is a noun and a verb. Also called a fortification.

25

What is the definition of a standard addition?

A technique in which an analytical signal due to an unknown is first measured. Then a known quantity of analyte is added, and the increase in signal is recorded. From the response, it is possible to calculate what quantity of analyte was in the unknown.

26

What is the definition of an use objectives?

In quality assurance, use objectives are a written statement of how results will be used. Use objectives are required before specifications can be written for the method

27

What is raw data?

are individual measurements, such as peak areas from a chromatogram or volumes from a buret. ie individual measurements.

28

What is treated data?

are concentrations or amounts found by applying a calibration procedure to the raw data.