QA/QC

Question 1

define quality assurance

Answer 1

the guarantee that the quality of a product is actually what is claimed on the basis of the quality controll applied in creating that product

not meant to protect against failures of quality control

consists of all planned activities implemented within the quality system that can be demonstrated to provide confidence that a pdt will fulfill requirements

Question 2

define quality control

Answer 2

maintenance and statement of the quality of a product specifically that it meets or exceeds some minimum standard based on known and testable criteria

consists of operational techniques to fulfill requirements for quality

Question 3

for are sources of published or standardized methods for selecting an analytical procedure?

Answer 3

AOAC
ISO standards
IUPAC

Question 4

what does AOAC stand for?

Answer 4

official methods of analysis

Question 5

the use of a standard method is not a guarantee a lab generates quality assured data

T/F?

Answer 5

true.

a lab needs to prove initially and continuously its ability to analyze food chemicals

Question 6

what are 2 methods of validation?

Answer 6

1) initial method validation

2) continuous method performance (routine analysis)

Question 7

describe initial method validation

Answer 7

initial performances proving the capacity of the lab to analyze a specific set of chemicals in specific matrices

Question 8

describe continuous method performance (routine analysis)

Answer 8

procedures and dataset demonstrating the capacity of the lab to continuously produce analyses with a high condense

Question 9

what does ESI stand for?

Answer 9

electrospray ionization

Question 10

what relationship between the analytical signal and concentration is preferred?

Answer 10

linear

Question 11

what must be done if the response between analytical signal and concentration is non-linear?

Answer 11

assess linearity

residual = obs value - predicted value

Question 12

when is linearity validated?

Answer 12

1) residuals (% of the value) do not exceed predefined criteria
2) residuals are randomly distributed in the plot residues vs calibration level

Question 13

what is the equation of residue?

Answer 13

Residue = (observed value - predicted value)/predicted value x 100

Question 14

what shape does a R=0.99 relationship have?

Answer 14

linear

Question 15

define LOD

Answer 15

limit of detection

the smallest amount/conc of analyte in the test sample that can be reliably distinguished with significance from the background/blank

Question 16

what is IDL?

what is MDL?

Answer 16

IDL = instrument detection limit

MDL: method detection limit

Question 17

how can LOD be determined?

Answer 17

1) 3 x standard dev of the conc in a matrix blank

2) matrix blank fortiied with analyte close to this limit

Question 18

if x < LOD, what does this mean? how do you report this?

Answer 18

signal not sig diff from background or blanks

report as below LOD

Question 19

if LOD < x < LOQ, what does this mean? how do you report this?

Answer 19

signal is significantly higher than the background or blanks, but level not high enough to provide accuracy on the value

result repoted as below LOQ

Question 20

if LOQ < x, what does this mean? how do you report this?

Answer 20

level is high enough to ensure some degree of accuracy on the value

exact value is reported

Question 21

how can trueness be assessed?

Answer 21

1) analysis of certified reference material
2) use of a reference method with little or no systematic error
3) use of the method when participating in interlab tests

Question 22

what is the equation of trueness?

equation of bias?

Answer 22

trueness % = measure conc / true conc x 100

bias % = (measured value - true value ) / true value x 100

Question 23

how is the recovery of a method assessed?

Answer 23

from spiking of samples

recovery % = (Xspiked - Xunspiked) / amount of added analyte x 100

Question 24

define repeatability

define reproducibility

Answer 24

repeatability: closeness of agreement between independent results obtained with the same method on identical test material under the SAME conditions
reproducibility: closeness of agreement between independent results obtained with the same method on identical test material but under DIFFERENT conditions