Analytical Techniques and Measureme

Question 1

Regions in Electromagnetic Spectrum: Ultraviolet light, Visible light, Infrared

absorbance wavelengths

Answer 1

Ultraviolet light < 400 nm
Visible light 400-700 nm
Infrared > 700 nm

Question 2

Planck’s formula for energy: E = hν

Answer 2

E = energy, h = Planck’s constant, ν = frequency

Question 3

Relationship between wavelength (λ) and energy (E)

Answer 3

Inversely related

E = hc/λ, where h is Planck’s constant, c is the speed of light

Question 4

Beer-Lambert’s Law relationship

Answer 4

Directly proportional

A = abc
ɛ = molar absorptivity; b = path length; c = concentration

Question 5

To compute the absorbance value given the % transmittance:

Answer 5

A =2 -log %T

Question 6

To determine the concentration of an unknown analyte:

Answer 6

c = A / (ɛ × b)

Abs of sample / (A STD x STD known)

Question 7

Blank used in Spectrophotometry

Answer 7

Distilled water, reagent, or sample to subtract absorbances not due to analyte

Question 8

Corrects absorbance caused by reagent color

Answer 8

Reagent blank

Question 9

Subtracts absorbance from hemolysis, icterus, turbidity, or drug interference

Answer 9

Sample blank

Question 10

Substance of known purity and concentration used to determine unknown analyte concentration

Answer 10

Standard solution

Question 11

Contains various analyte concentrations to monitor analytical performance

Answer 11

Control solution

Question 12

Characteristics of Control solution

Answer 12

Commutable, stable, no matrix effects, spanning clinically important range

Question 13

Values provided by manufacturer

Answer 13

Assayed control

Question 14

Values determined by the laboratory

Answer 14

Unassayed control

Question 15

Checked using didymium glass or holmium oxide, directly proportional to Beer’s Law.

Answer 15

Wavelength accuracy

Question 16

Done using glass filters and solutions that have known absorbance values.

Answer 16

Absorbance check

Question 17

Change in concentration resulting in a straight-line calibration curve, related to Beer’s Law.

Answer 17

Linearity

Question 18

Any wavelength outside the band of interest, detected using sharp cut-off filters.

Answer 18

Stray light

Question 19

Sources include extraneous room light, light dispersed by a darkened lamp envelope, deteriorated optics, scratches on optical surfaces, dust particles in the light path, higher order spectra produced by diffraction gratings.

Answer 19

Sources of stray light

Question 20

Provides polychromatic light which the sample will modify or attenuate by absorption.

Answer 20

Light source

Question 21

UV light source; commonly used in the UV region.

Answer 21

Deuterium/Hydrogen

Question 22

UV-visible light source.

Answer 22

Xenon/Mercury

Question 23

Visible to near infrared light source.

Answer 23

Tungsten; LASER

Question 24

Prevents stray light from entering the monochromator system.

Answer 24

Entrance slit

Question 25

Effects of stray light includes

Answer 25

absorbance error and loss of linearity

Question 26

Isolates a portion of the spectrum emitted by the source and focuses it on the sample.

Answer 26

Monochromator

Question 27

Continuous, non-linear spectrum; better separation of high-frequency light.

Answer 27

Prism

Question 28

Continuous, linear spectrum; uniform separation of wavelengths; most common.

Answer 28

Diffraction gratings

Question 29

Controls the bandpass; allows only a narrow fraction of the spectrum to reach the cuvette.

Answer 29

Exit slit

Question 30

Range of wavelengths transmitted, calculated as width at more than half the maximum transmittance.

Answer 30

Bandpass

Question 31

Sample cell; may be round or square.

Answer 31

Cuvette

Question 32

Material used for UV and IR measurement.

Answer 32

Quartz/Fused silica

Question 33

Material used for UV to visible measurements.

Answer 33

Plastic

Question 34

Material used for visible measurements only.

Answer 34

Glass

Question 35

Converts the transmitted light energy into an equivalent amount of electrical energy.

Answer 35

Photodetector

Question 36

Simple photodetector type.

Answer 36

Barrier layer cell

Question 37

Requires an external voltage source for operation (photodetector)

Answer 37

Phototube

Question 38

Photodetector with excellent linearity.

Answer 38

Photodiode

Question 39

Most commonly used and most sensitive photodetector; amplifies light signal.

Answer 39

Photomultiplier tube

Question 40

Processes the electrical signal, performs mathematical operations, and displays the output.

Answer 40

Readout device

Question 41

Formula used to process and display absorbance:

Answer 41

Absorbance readout formula: A = 2 - log(% transmittance)

Question 42

Designed to compensate for variations in intensity of the light source by splitting the light beam.

Answer 42

Double-beam spectrophotometry

Question 43

Type of double-beam spectrophotometry where a beam splitter directs one portion of light to the sample cuvette and the other to the reference cuvette.

Answer 43

Double-beam-in-space

Question 44

Type of double-beam spectrophotometry where a chopper rotates continuously and strikes one cuvette at a time.

Answer 44

Double-beam-in-time

Question 45

Measurement of light emission caused by a chemical, biochemical, or electrochemical reaction, not by photo illumination.

Answer 45

Luminometry

Question 46

Emission of light caused by oxidation of organic compounds catalyzed by an enzyme, a metal, or hemin.

Answer 46

Chemiluminescence

Question 47

A special form of chemiluminescence where an enzyme-catalyzed chemical reaction produces light emission and involves the use of natural substrates.

Answer 47

Bioluminescence

Question 48

Emission of light caused by a reaction generated electrochemically on the surface of an electrode.

Answer 48

Electrochemiluminescence

Question 49

Detection of scintillations (flashes of light) using a PM tube and counting electrical impulses.

Answer 49

Scintillation Counting

Question 50

Type of scintillation counting used for detecting gamma radiation (I125 and I131).

Answer 50

Crystal scintillation (gamma counter)

Question 51

Type of scintillation counting used for detecting beta radiation (H3 and C14).

Answer 51

Liquid scintillation (Beta counter)

Question 52

Involves fragmentation and ionization of molecules, followed by separation of ions by mass-to-charge ratio.

Answer 52

Mass Spectrometry

Question 53

Mass spectrometry technique that uses MALDI for analyzing proteins and other large molecules.

Answer 53

MALDI TOF MS

Question 54

Mass spectrometry technique that combines gas chromatography with mass spectrometry for separating and analyzing compounds.

Answer 54

GCMS or HPLC-MS

Question 55

Mass spectrometry technique that uses multiple stages of mass spectrometry for detailed analysis.

Answer 55

Tandem MS (MS/MS)

Question 56

A quantitative method for determining the amount of an analyte based on isotope dilution.

Answer 56

IDMS

Question 57

Non-destructive method for determining the structure of organic compounds, used in lipoprotein particle measurements.

Answer 57

Nuclear Magnetic Resonance (NMR) Spectroscopy

Question 58

Approach where specimens are pumped through a continuous tubing system at the same rate and subjected to the same analytical reactions; can result in carry-over problems.

Answer 58

Continuous flow

Question 59

Automation method using centrifugal force to transfer liquids into separate cuvets for measurement, capable of batch analysis.

Answer 59

Centrifugal analysis

Question 60

Automation method that places each sample and accompanying reagents in separate containers, allowing for batch analysis, random access, or stat capabilities.

Answer 60

Discrete analysis

Question 61

Analyzer configuration where specimens enter the analytical process one after another, and results are produced in the same order as specimens.

Answer 61

Sequential analysis

Question 62

Analyzer configuration where all specimens are subjected to a series of analytical processes simultaneously, in parallel.

Answer 62

Parallel analysis

Question 63

Analyzer configuration that groups many specimens in the same analytical session for analysis, handling a large number of specimens in one run.

Answer 63

Batch analysis

Question 64

Analyzer configuration that allows each specimen to be analyzed for a different set of tests and can analyze stat specimens out of sequence as needed.

Answer 64

Random-access analysis

Question 65

Type of analyzer that requires reagents to be provided in a unique container or format by the manufacturer.

Answer 65

Closed-system analyzer

Question 66

Type of analyzer that allows operators to change parameters and use reagents from various suppliers.

Answer 66

Open-system analyzer

Question 67

Testing device with advantages of reduced turnaround time and electronic documentation of testing.

Answer 67

Point of Care Testing (POCT) Devices

Question 68

Most commonly used POCT device that uses enzymatic methods coupled with photometric or electrochemical detection but should not be used to diagnose diabetes mellitus.

Answer 68

Blood glucose monitors (glucometers)

Question 69

SMA, Technicon is an example of

Answer 69

Continuous flow

Question 70

Cobas-Bio (Roche) is an example of

Answer 70

Centrifugal analysis

Question 71

OCD Vitros 350, Beckman Unicel DXC, Dupont ACA, Abbott Architect, Cobas 6000, Siemens Vista are examples of

Answer 71

Discrete analysis

Question 72

Point of Care Testing (POCT) Devices

Answer 72

Blood glucose monitors (glucometers)