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CHEM201 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

what is a batch analysis?

A

many specimens are grouped in the same analytical session aka being tested for the same one thing (glucose levels)

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2
Q

what is carryover?

A

transport of a quantity of analyte or reagent from one specimen reaction into and contaminating the next one

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3
Q

what is continuous flow analysis?

A

analysis where each specimen in a batch passes through the same continuous stream at the same rate and subjected to the same analytical reaction

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4
Q

random access analysis is:
a) most common configuration of an automated analyzer
b) analysis is performed on a collection of specimens sequentially
c) each specimen is analyzed from a different selection of tests
d) all of the above

A

all of the above

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5
Q

what are multiple and single channel analysis?

A

multiple: each specimen is tested for multiple things, thus a set of results is obtained (CBC)
single: each specimen is only tested for one analyte, and one test result per specimen

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6
Q

single channel analysis is similar to ______, multiple channel analysis is similar to _______

A

batch analysis; random access analysis

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7
Q

if the wavelength is long, the frequency will be ____ and if the wavelength is short, the frequency will be ______

A

low; high

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8
Q

does 300nm or 1200nm have a higher energy?

A

300nm; has shorter wavelength higher frequency

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9
Q

are UV waaves longer or shorter than visible waves? are they higher or lower?

A

shorter and higher energ

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10
Q

T/F DNA and protein do not absorb UV light because they are uncoloured

A

F, they still do because of the molecular makeup

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11
Q

spectrophotometer is a device that measures

A

the amount of light energy a solutuon absorbds/transmits

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12
Q

T/F the amount of transmitted energy is always less than the amount of incident energy

A

T

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13
Q

what formulas can be used for absorbance?

A

A = 2-log(%T)
A= -log(T in decimal)

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14
Q

as absorbance increases, that means that transmittance ____

A

decreases; inverse relationship

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15
Q

how would you calculate % transmittance if you were given absorbance?

A

%T = 100x 10^(-Abs)

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16
Q

the wavelength at which any give solute exhibits the max abs usually provides the best
a) precision
b) accuracy
c) sensitivity
d) specificity
e) more than 1

A

e) sensetivity and specificity

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17
Q

what is molar absorptivity?

A

how much light will be absorped by 1cm of a 1M solution

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18
Q

T/F we always use the maximum absorbance wavelength for every method

A

F, we try but need to be mindful of interference

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19
Q

what are the limitations of beers law?

A
  1. incident light must be monochromatic
  2. solvent absorption is insignificant compared to solute (colourless)
  3. solute [] is within linear limits
  4. no optical interferences (dust, crack)
  5. calibrate and check for quality!
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20
Q

T/F you should always force your line through zero

A

false! it would create a bias

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21
Q

what are things to watch for when deciding what light source to use for a spec?

A

how much heat it puts off, the temperature it reaches, the stability of light source (no flicker)

22
Q

how is a light beam split into its component wavelengths in a spec?

A

prism, filter or gratings

23
Q

would filter, prism, grating be more precise?

A

diffraction grating

23
Q

what is the purpose of fiber optics?

A

to allow closer positioning within the spec to minimize the footprint of the instrument

24
Q

which of the following is not meant for spec in the UV region?
a) quartz
b) silicate glass
c) specialized plastics
d) fused silica cuvetttes

A

b) silicate glass

25
Q

what nm can silicate glasses be used for?

A

350-2000nm

26
Q

what do photodetectors do?

A

convert light energy into electrical signal to give a readable number

27
Q

what is a photomultiplier tube (PMT)?

A

example of most used photodetector that has a very rapid response time

28
Q

what is a linear photoiode array?

A

less popular detector, more simple version

29
Q

what is a band pass?

A

range of wavelength(s) transmitted by the monochromater for any desired wavelength

30
Q

would you want a band pass that is lower or higher?

A

you want a lower band pass because it gives you a more specific wavelength

31
Q

what is false regarding photometric accuracy?
a) uses filters or solns w/ exact known abs at specific wavelength
b) must be insensitive to bandpass or spec config
c) ensures that spec is measuring abs accurately
d) ensures that selected wavelength on spec corresponds to actual wavelength being transmitted

A

d) ensures that selected wavelength on spec corresponds to actual wavelength being transmitted

32
Q

what does photometric linearity ensure?

A

that it is following beers law; amount of energy absorbed vs instrument readout should be linear in the anticipated range

33
Q

which is not a common source of error in a spec relating to photometric linearity?
a) keeping the lid closed when it runs
b) faulty detector
c) improper wavelength
d) stray light

A

a) keeping the lid closed when it runs

34
Q

what is false regarding stray light?
a) is any light that reaches the detector that did not go through the sample
b) may increase with time due to aging of optical components and cause drift/trends
c) has no effect on the standard curve linearity
d) may falsely contribute to transmittance reading

A

c) has no effect on the standard curve linearity

35
Q

what are the 4 quality processes in spec?

A
  1. wavelength accuracy
  2. photometric accuracy
  3. photometric linearity
  4. stray light
36
Q

which of the following may cause interferences in spec?
a) hemolysis
b) icteric
c) lipemia
d) drugs
e) all of the above

A

all of the above

37
Q

T/F if hemolysis is due to collection, this is an invitro interference

A

T

38
Q

what is a chemical interference in spec?

A

relative to [] of interferent, best to remove if possible
(use wavelength for least interference)

39
Q

which of the following is not a corrective measure for spec interferences?
a) blanks
b) diluting the patient sample
c) multiple wavelength readings
d) kinetic methods

A

b) diluting the patient sample

40
Q

how and when are blanks used as corrective measures?

A

if you cant correct interference bc its invivo, use a specimen blank. this blanks colour of specimen off

41
Q

which is true regarding corrective methods?
a) only done when need to
b) done during every run
c) multiple wavelength readings is done with every sample
d) kinetic methods are used for critical samples

A

a) only done when need to

42
Q

how does multiple wavelength reading work? give an example

A

bichromatic measuring at two wavelengths or at a high peak away from other interferences

e.g. bilirubin has 2 peaks, one with interference w/ hemolysis so you run on both, then only run on the one where bilirubin is only detected

43
Q

how does kinetic method work?

A

reading over time to choose optimum expression of analyte, see when/where it shows up

44
Q

give an example of a lab method that uses reflectance photometry

A

urine dipstick reading in machine

45
Q

T/F reflectance photometry is linear

A

F, needs math to relate [] to reflectance

46
Q

what is fluorimetry?

A

measurement of emitted light, accurate and very sensitive

47
Q

what is the stoke’s shift?

A

difference in wavelength from excitation to emitted

48
Q

when does fluorescence occur?

A

when a molecule absorbs a photon of radiant energy at one wavelength and reemits photons of light at a longer less energy wavelength

49
Q

which of the following is true regarding components for fluorometers?
a) DNA and Ab are commonly measured this way
b) spectrofluorometers have 2 spectral monochromators
c) higher energy emitted radiation passes through excitation monochromator to isolate the fluorescent peak
d) may use filters to restrict wavelengths
e) two or more of the above

A

e) everything is true!

CHEM201 (5 decks)

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