Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

food toxicants and analysis > Quality Assurance > Flashcards

Quality Assurance Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards
1
Q

What are different internal standards that can be used? (3)

A
  1. Same substance, but mass-labeled (or somehow different)
  2. Different substance (chemically similar)
  3. Same substance (spiking)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

standard solutions have a known ____ and ____.

A

purity; concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a stock standard?

A

standard of HIGH CONCENTRATION, long storage life

- used to prepare working standards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

A calibration curve is ____ _____ while spiking is ____ _____.

A

external calibration; internal calibration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When would a standard be determined to be expired?

A

The measurements of that standard differ from a newer standard by more than 10% (SANCO)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

The storage condition of standards will affect:

A

stability/shelf life

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

True/False: stock standards are used for spiking, calibration, and comparison with samples during analysis

A

False; stock standards used to prepare working standards for that purpose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

the linear relationship established by running standards should be:

A

a non-weighted regression curve (all points carry equal weight, do not force through intercept, etc)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the blank used for, in preparing an external calibration curve?

A

Subtract signal of blank from signal for each calibration point (correction)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How should the spacing and range of the standards be done, according to IUPAC?

A

spacing: depends on precision level required; should be evenly spaced
range: should be 0 to 150% of expected test result

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How should calibration samples be run?

A

Random order

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

According to IUPAC, what is the minimum number of standards needed for a calibration curve?

A

5 (excluding 0)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are residuals an indicator of?

A

Whether the calibration curve is acceptable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The residuals should be in what sort of distribution? What if this is not the case?

A

Randomly distributed around zero (regression curve of residuals is straight line y=0)
if TREND exists: problem with method, need to reexamine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

List the steps of preparing an external calibration curve

A
  1. Prepare blank + standard samples (need triplicates)
  2. run in random order
  3. Calculate mean and SD for each point, correct using blank
  4. Graph and establish regression curve of best fit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are residuals?

A

Difference between MEASURED value and CALCULATED value (using calibration curve)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the “linear range” of a signal on a calibration curve?

A

the concentration range at which SIGNAL INTENSITY is directly proportional to concentration (linear relationship)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

(the blank signal + 3SD)/slope is the:

A

LOD

19
Q

What is IDL? What is MDL?

A

IDL: instrument detection limit
MDL: Method detection limit

20
Q

True/False: A good instrument should have a high LOD

A

False: a higher LOD means that it cannot detect lower concentrations confidently

21
Q

Differentiate IDL and MDL:

A

IDL: instrument limit, expressed as amount injected in machine for analysis; instrument blanks are run (only through machine)
MDL: for entire procedure, expressed as concentration in food matrix intially; procedural blanks are run (taken through all steps of procedure)

22
Q

What is LOQ? Define it.

A

limit of quantification
smallest level that can be quantified with acceptable precision/accuracy

10SD from concentration in procedural blank

23
Q

What is LOD? Define it.

what is the criteria?

A

Limit of Detection
smallest level that produces a SIGNIFICANTLY DIFFERENT signal from the background noise/blank
(can be distinguished/detected)

3SD from response obtained on blanks

24
Q

If the result is below the LOD, what do you do?

A

report as below LOD

25
Q

Procedural blanks are also known as:

A

matrix blanks

26
Q

Why might calibration curves prepared using standard samples be inaccurate for comparison with a food sample?

A

Matrix effect; calibration curve does not correspond to signal obtained from food sample

27
Q

Spiking is known as the:

A

standard addition method

28
Q

What do you report if the result is above LOD but below LOQ?

A

signal is sufficient to indicate presence (detectable), but not enough to be quantified.
Report as BELOW LOQ

29
Q

Can a result be above the LOQ but not the LOD?

A

No. LOD < LOQ

30
Q

How can the matrix affect the analysis results?

A

Increase or decrease signal, give higher or lower concentrations than actual amounts

31
Q

You can only report the level of the analyte if the result was above both the ____ and the ____.

A

LOD, LOQ

32
Q

The spiking solution added should be: (2)

A
  • small amount (assume volume stays constant)

- highly concentrated (so can add small amount)

33
Q

What is the standard addition method?

A

Add KNOWN AMOUNTS of standard solution (same as analyte) to sample -> measure response before/after each addition (x, x+1, x+2, x+3…) -> establish curve, determine original amount (x)

Or, can separate sample into many SUBSAMPLES, add increasing amounts to each

34
Q

What is the internal standard method?

A

Adding fixed amount of ANOTHER CHEMICAL to sample

35
Q

The ____ is the same over a range of concentrations, which is used in internal standard calculations.

A

RF (response factor)

36
Q

The substance added in the internal standard method should: (2)

A

have similar chemical properties

Not interfere with analyte analysis

37
Q

The internal standard method aims to deal with: (3)

A

Matrix effect
Injection variability
Analyte loss

38
Q

What is used as an IS in ICP-MS?

A

rare elements (Yttrium, Rhodium, Indium, Scandium)

39
Q

What could we use as an IS in GC-MS or LC-MS?

A

Mass labelled surrogate

40
Q

what is the response factor?

A

ratio of (signal A/IS) / (concentration A/IS)

41
Q

“Trueness” is also known as ____. How do you assess it? (4)

A

Recovery

  1. Comparison of results with known standard (certified ref material)
  2. Compare results with those from a method that works, has little error
  3. compare with results from interlaboratory tests
  4. spiking samples (based on blanks or positive blanks)
42
Q

Where can you source certified materials in Canada? In the US?

A

Canada: NRC Certified Reference Materials
US: NIST

43
Q

What is mass labelling?

A

Using a modified version of the compound, with C13 or deuterium instead of normal C or H (molecule will have different molecular mass, so can be differentiated from original)

food toxicants and analysis (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions