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Instrumental Analysis > Test 1 > Flashcards

Test 1 Flashcards

1
Q

measurement

A

assigning a value to a physical quantity based on a standard

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2
Q

data domains

A

the ways that information can be encoded in an object or via a signal throughout the measurement process

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3
Q

error types

A

random, systemic (consistently lower or higher), human (bias)

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4
Q

what measurement represents precision

A

standard deviation, = random error

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5
Q

calibration sensitivity

A

slope of the detection line

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6
Q

analytical sensitivity

A

slope over standard deviation

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7
Q

ppm=

A

mg/L

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8
Q

ppb=

A

ug/L

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9
Q

flow of information in an instrument

A

stimulus (from device)> sample > response> transducer > some data domain> information processor> readout (usually a computer)

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10
Q

analog quantities are measured

A

by magnitude (electrical current, etc) over time

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11
Q

transducer

A

interconverts info from electrical to nonelectrical domains

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12
Q

input transducer

A

transducer that takes info from nonelectric to electric domains

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13
Q

detector

A

mechanical, electrical, or chemical detector to show change in temp, pressure, electricity, radiation, ion conc, *smoke detector

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14
Q

readout device

A

transducer that converts from electric to nonelectric domains

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15
Q

sensor

A

monitors a specific chemical species and changes reversibly in response to a change. has recognition>transducer>readout *glucose sensor

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16
Q

how to select instrumentation

A

consider required accuracy, amount of sample, concentration range, interference, physical and chemical properties, and number of samples to be processed

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17
Q

pop. mean and SD

A

u and sigma

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18
Q

sample mean and sd

A

x bar and s

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19
Q

normal distribution

A

1s: 68.3%, 2s: 95.45%, 3s: 99.73%

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20
Q

least square assumption

A

error in y > error in x

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21
Q

bias (gamma)

A

calculated as y= u - xbar (pop. - sample). = system error

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22
Q

accuracy calculation

A

comparing sample mean and pop. mean (bias calculation)

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23
Q

LOD equation

A

C = (3Sbl/m)

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24
Q

selectivity eq (general anal chem)

A

S = maCa + mbCb +……

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25
Q

selectivity coefficient (for interfering spp in sensors)

A

k(b,a) = mb/ma (closer to 0 is better)

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26
Q

dynamic range

A

which concs have reliable results, located btwn the LOQ and LOL

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27
Q

type 1 error

A

false positive

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28
Q

type 2 error

A

false negative

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29
Q

LOQ

A

limit of quantitation, above in measurements have 5% standard error

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30
Q

degree of freedom

A

n-2 because we need 2 of the points just to make a line

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31
Q

degree of freedom in sample mean

A

n-1 bc the mean occupies one number

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32
Q

Cdl

A

=3Sbl/m (the conc at the DL is 3 SD of the blank out)

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33
Q

standard deviation units

A

same as the mean

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34
Q

relative error

A

(Cmeasured - Creal)/Creal

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35
Q

thermal/Johnson noise

A

charge carriers in resistors, capacitators, (anything with resistance) cause random error corresponding to the bandwidth and temperature. - frequency independent

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36
Q

shot noise

A

quantized particles (whole numbers) cross a junction, cause random noise, frequency independent. can be dec with bandwidth change.

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37
Q

flicker noise

A

aka 1/f noise, inversely proportional to frequency

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38
Q

environmental noise

A

frequency dependent bc it is at specific frequencies, non-fundamental, things like EM waves from radio

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39
Q

S/N

A

signal to noise ratio is set equal to mean signal/standard deviation also = 1/RSD

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40
Q

non-random noise

A

systemic error in measurement equipment causes high or low interference

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41
Q

fundamental noise

A

noise due to uncertainty principle etc or factors of physical instrumentation

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42
Q

noise reducing hardware

A

grounding/shielding, difference/instrument amplifier, analog filter, modulation

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43
Q

noise reduction in measurement

A

take the same measurement many many times using S/N=sqrt(n)(Sx/Nx) for desired ratio

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44
Q

n in noise/signal

A

the number of measurements conducted

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45
Q

S/N at which signal is indiscernible

A

S/N =3

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46
Q

conjugate quantities

A

when one is measure precisely it is impossible to measure the other precisely ie. position and speed, creates fundamental noise

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47
Q

white noise

A

aka gaussian noise, any frequency independent noise (thermal, shot)

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48
Q

A/C frequency (in US)

A

60 Hz

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49
Q

chemical noise

A

variations in chemicals (ie batches of the same soln vary by 0.1%)

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50
Q

rising time

A

time interval it takes between 10% and 90% power of an electrical signal when activated

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51
Q

Poisson process

A

used to measure probability of something discrete (ie e- for shot noise) P= (lambda^k(e^-lambda))/k!

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52
Q

bandpass filter

A

filters out high and low ranges leaving some middle range of signal

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53
Q

high-pass filters

A

filter out long wavelengths

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54
Q

low-pass filters

A

filter out short wavelengths, often used for DC, thermal and shot noise

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55
Q

grounding and shielding

A

physically prevent electronic interference by surrounding with grounded conductive material which attracts signal to make it not be noise.

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56
Q

modulation

A

used for DC or low frequency signal, as 1/f noise is high, and then high pass filter can be used and it can be returned to og frequency with reduced noise. example: mechanic chopper

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57
Q

ensemble averaging

A

higher n to approach true value thru averaging

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58
Q

central limit theorem

A

more measurements approach normal distribution, with the center being the “true” value

59
Q

adding values with associated noise

A

S(n) (+-) Nsqrt(n), and averaging this way shows how noise gets smaller

60
Q

electric domain types

A

digital, analog, time

61
Q

LOQ equation

A

C = (10Sbl/m)

62
Q

quantitation

A

connecting concepts of measurement/calculation

63
Q

difference/instrument amplifier

A

used instead of a normal amplifier when the signal is read so there is less noise. (difference cancels parts in common, instrument is second choice and reduces common noise with extra pieces). used for low signal in noisy environment

64
Q

when the selectivity eq takes the form s = m(Ca + KCb …..) the term in parenthesis is..

A

the value measured by the instrument

65
Q

Huygens

A

there are waves and wavelets - wave nature of light

66
Q

energy of a photon =

A

hv, v = freq

67
Q

Thomas Young

A

slit diffraction - it it diffracts it must be a wave (light)

68
Q

wave number

A

number associated with a reciprocal wavelength in 1/cm

69
Q

diffraction distance equation

A

wavelength = line segment BC*DE/(nOE), n = number of bands, where BC is distance between two entrance slits, OE is the horizontal distance between the slits and the far wall, and DE is the distance between the band and the part of the wall horizontal to the entrances.

70
Q

transmission

A

speed of light changes based on medium

71
Q

refractive index eq

A

engi = c/v (v is velocity). it is the ratio of the speed of light to the speed of light in the material ie how much slower it is

72
Q

conserving energy in different media

A

c must change bc lambda = c/v and v cannot change

73
Q

dispersion

A

variation in refraction index throughout a substance

74
Q

dispersion of a substance eq

A

D = engi(lambda)

75
Q

anomalous dispersion

A

sharp drop in dispersion graph due to shift in engi from absorption at a certain wavelength for the substance

76
Q

speed and density

A

due to refraction, more dense objects dec. speed.

77
Q

metamaterials

A

have negative ri (reflective index), the light direction flips

78
Q

speed and refraction/reflection

A

reflection can have a negative speed, refraction cannot (they are vectors)

79
Q

angle of incidence is equal to..

A

angle of reflection

80
Q

reflection eq

A

Ir/Io = (eng2-eng1)^2/(eng2+eng1)^2, where Ir is intensity of reflected beam and Io is initial intensity

81
Q

boundary

A

change between media (b to a = a to b)

82
Q

black body

A

ideal physical object that is opaque, non-reflective, absorbs all EM waves

83
Q

black body radiation

A

= thermal/cavity radiation. what surrounds a body (black body( at eq with its environment

84
Q

photoelectric effect equation

A

E = hv = KE - work function

85
Q

matter wave function

A

de Broglie, 1923, lambda = h/p (p is momentum)

86
Q

hamiltonian and eigenvalues

A

measures of energy correspond to a hamiltonian operator and an eigenvalue

87
Q

Compton scattering

A

inelastic scattering of light by a free moving charged particle like e-

88
Q

Thomson scattering

A

Elastic scattering of light by a free moving charged particle like e-

89
Q

inelastic scattering

A

energy of photons is changed

90
Q

UV and visible light cause..

A

e- transitions/excitation, emission of light

91
Q

infrared light causes..

A

atoms to vibrate

92
Q

microwave radiation causes..

A

atoms to rotate

93
Q

spectroscopy components in order

A

source of radiation, sample (in container), wavelength selector, radiation detector, photoelectric transducer, signal processor, signal readout

94
Q

types of radiation sources

A

continuum, line, laser

95
Q

continuum radiation source

A

changes in intensity slowly as a function of lambda

96
Q

line radiation source

A

emits a limited number of lines or bands of radiation

97
Q

laser radiation source

A

emits narrow, monochromatic, coherent, intense beam

98
Q

source of noise in radiation for spectrometry

A

the fluctuation in radiation

99
Q

narrow bandwidth is important bc

A

it gets you a linear relationship between concentration and signal

100
Q

effective bandwidth

A

the width halfway up the peak

101
Q

types of optical filters

A

long pass, short pass, bandpass, interference, absorption

102
Q

long pass filter

A

transmission of >400 nm

103
Q

short pass filter

A

transmission of <600 nm

104
Q

bandpass filter

A

shows a large portion in the middle, around 100 nm range

105
Q

interference filter

A

uses constructive interference, has dielectric layer and reflective part. wavelengths are usually UV to IR, eff bandwidths are 1.5% of the wavelength

106
Q

absorption filter

A

absorb bandwidths maybe 30-250 nm

107
Q

monochromators

A

can use grating or prism to direct a spec lambda out the exit

108
Q

1 angstrom =

A

0.1 nm

109
Q

Snell’s law

A

sin (angle of incidence)/sin(angle of refraction) = eng2/eng1 = v1/v2

110
Q

refractive index

A

measure of how much a medium interferes with radiation

111
Q

coherent radiation

A

sources have identical freq and phase relationships over time. necessary if you want to create a diffraction pattern

112
Q

work function

A

constant that shows the min. electron binding energy in a substance

113
Q

photoelectric effect

A

photoelectrons can be emitted from a substance when a specific wavelength of light / photons hit it

114
Q

phosphorescence

A

light emitted by electrons going down in energy level but delayed after the initial energy input

115
Q

resonance florescence

A

when emitted light has the same frequency as the beam used to excite the e-

116
Q

stokes shift

A

shift down in energy between excitation beam and fluorescence due to the energy released by vibration of the e-

117
Q

conserving energy in change of medium eq

A

speed = lambda1/freq1 = lambda2/freq2

118
Q

does speed of light change

A

yes, it does, and wavelength does, so freq can stay constant

119
Q

interference filter equation

A

lambda = 2t(eng)/n (n is order, t is thickness) OR 2dn (d = thickness, n = 1)

120
Q

grating: angular dispersion eq

A

n/dcos(r) where r = reflection angle, d = distance of 1 slit, n = order of diffraction

121
Q

grating: linear dispersion eq

A

focal length*(n/dcos(r)), where r = reflection angle, d = distance of 1 slit, n = order of diffraction

122
Q

reciprocal linear dispersion eq

A

d/nf ..where d = distance of 1 slit, n = order of diffraction, f = focal length

123
Q

resolving power of 2 freqs eqs

A

lamba hat = avg of 2 lambdas, over delta lambda = diff btwn the 2.

124
Q

effective bandwidth eq

A

(lambda2-lambda1)/2 = half the distance

125
Q

how to get slit width

A

lambda(eff)=w(D^-1) (effective bandwidth and reciprocal linear dispersion)

126
Q

resolving power eq

A

R = nN where n is diffraction order, N is # of slits that have light on them

127
Q

1 einstein

A

1 mol photons

128
Q

bandwidth and slit width

A

bandwidth= the distance btwn lambdas that is the width of the beam, eff bandwidth is what actually comes out (1/2 distance), and that is the slit width. we want smaller signals so we want smaller bandwidth but this sacrifices time

129
Q

data domain categories

A

physical/chemical, digital, analog, time

130
Q

digital data domains

A

number, parallel, serial, count

131
Q

analog data domains

A

current, voltage, charge

132
Q

time data domains

A

phase, freq, pulse width(ie rising time)

133
Q

focal length

A

how far light travels btwn diffraction and target

134
Q

radiation detectors work by..

A

transforming radiation energy to electrical signal

135
Q

information conducted in stages of spectrophotometry

A

intensity of beam, concentration of analyte, electrical charge, computation, then readout

136
Q

prop of error for multiplication/ division

A

the square root of the sum of the % errors (both squared) = the % of the result - multiply by the result to get the actual error

137
Q

radiation detector types

A

photon detectors or thermal detectors (only IR)

138
Q

electric signal eq

A

S (signal) = kP + kd (kd = dark constant, k = calibration sensitivity, P= power of the radiation)

139
Q

photomultiplier

A

photon detector where signal is amplified by a series of plates

140
Q

signal processor in spectrophotometer

A

amplifies electrical signals from transducer, converts them from analog to digital

141
Q

fiber optics

A

can be used to transmit electricity 100s of meters

142
Q

prop of error adding and subtracting

A

square root of the sum of the squares of the errors

143
Q

error in analytical processes

A

every stage has an associated error

Instrumental Analysis (4 decks)

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