Quality Assurance and Calibration Methodss

Question 1

define quality assurance

Answer 1

focusing on the product and identifying defects. involves regulating the quality of samples, and using replicate measurements

EMPHASIS IS ON PROCESS

Question 2

what is the quality assurance process?

Answer 2

1. define objective: why is this important, how can it be used?
2. set specifications: accuracy, precision, repeatability, reproducibility, sample, cost, location, selectivity, sensitivity, LOD, LOQ, blanks, quality control
3. asses: asses to see if data collected fits within the specified operational limits, SOP’s

Question 3

define repeatability

Answer 3

the ability for an individual to reproduce the same procedure in the same lab to get the same results (you doing it again)

Question 4

define reprodicibility

Answer 4

ability for other people in different labs to do the same procedure and get same results

Question 5

define selectivity

Answer 5

being able to identify analyte from other species

Question 6

define sensitivity

Answer 6

being able to detect and reliably measure changes in analyte concentration

Question 7

define limit of detection (LOD)

Answer 7

smallest amount of analyte that can be used to distinguish from blank

Question 8

define limit of quantification (LOQ)

Answer 8

smallest amount of analyte that can be measured with accuracy

Question 9

what are the 3 kinds of blank that you can use in a lab?

Answer 9

method: all components, except the analyte, gone through all prep steps
reagent: same as method but hasn’t gone through the prep
field: similar to method but it has been exposed to same environment that sample was retrieved from, used for systemic errors

Question 10

what are standard operating procedures (SOP’s)?

Answer 10

they outline what steps should be taken in analysis and how documentation should be done to achieve the same results

Question 11

define calibration curve

Answer 11

a plot that related an experimentally measured property to know analyte concentrations. creating a set of standard solutions that are separate from the sample.

Question 12

what are the 4 steps in creating a calibration curve?

Answer 12

1. create set of standard with the range of 0-150% concentration expected from unknown sample
2. measure a blank and the responses of the samples
3. plot a graph that measures response vs. concentration of the analyte
4. find the best straight line and use formulas to find the needed info

Question 13

what is the equation for the line of regression?

Answer 13

measured response (y) = m x quantity of analyte (x) + b

quanity of unknown = measured response - b / m

Question 14

define standard addition

Answer 14

this is used to determine the concentration of a substrate (analyte) in an unknown sample. a known amount of analyte is added to an unknown. Know the relations with the formula

Standard, Substrate added, accounts for Systemic error

Question 15

define internal standards

Answer 15

known amounts of another compound is added to an unknown solution and it accounts for random errors. uses a response factor, which is different from the standard addition.

Question 16

define the matrix effect

Answer 16

when compounds in the sample, outside of analyte, affect the slope of the calibration curve