Midterm

Question 1

Define what is meant by system (under study) (3)

Answer 1

• it has the analyte about which information is to be obtained
• the info of the analyte is inherent in the physical and/or chemical characteristics of the analyte
• the info obtained can be interpreted, manipulated and/or used as required by the analyst

Question 2

Define analytical instrument (2)

Answer 2

• it is what is used to get info about the analyte (from the system) – can be seen as a device that communicated ino from the analyte to the analyst
• to get info analyte has to be stimulated somehow (ex. with electromagnetic, electrical, mechanical, and/or nuclear energy) to get a response from analyte

Question 3

What are data domains?

Answer 3

• various modes of encoding information
• used to make a classification scheme to analyze and explain the measurement process
• used to examine the flow of info inherent in the physical and chemical characteristics of the analyte to a readout

Question 4

Give examples of data domains

Answer 4

meter pointer, chart recorder, digital device

Question 5

What are the two main classifications of data domains?

Answer 5

1. non-electrical

2. electrical

Question 6

What measurements do electrical domains have

Answer 6

analog (current, voltage, charge), time (frequency, pulse width, phase), digital (count, serial, parallel)

Question 7

What measurements do non-electrical domains have?

Answer 7

physical and chemical (mass, length, temp, colour), scale position, number (digital measurement)

Question 8

What is the measurement

Answer 8

• final numerical result as some function of the relevant physical or chemical property being measured
• can be represented as a series of inter-domain conversions
• beings and ends in the non-electrical domain

Question 9

How can the measurement be in the electrical domain?

Answer 9

• can be encoded through an input transducer

Question 10

What is the out-put transducer

Answer 10

the read-out device that converts data in the electrical domain to the non-electrical domain

Question 11

Define transfer functions of the transducers

Answer 11

• mathematical relationships between the input transducer and the electrical signal and the out-put

Question 12

Define detector

Answer 12

mechanical, electrical or chemical device that identifies, indicates, or records a change in a variable of the system

Question 13

Define transducer

Answer 13

• specific to devices that convert info in non-chemical domain to info in electrical domain and vice versa
• a read-out device (ex. graph, pointer on a meter)
• converts info in electrical domain to a domain that can be perceived and understood by analyst

Question 14

Define sensor

Answer 14

• device capable of monitoring chemical species continuously and reversibly
• has a transducer with a substance that responds to physical or chemical characteristic of analyte

Question 15

What information is required for selecting an analytical method (name 5 of 11)

Answer 15

• accuracy
• amount of sample available
• concentration range of samples
• possible interferences due to contaminants
• phys and chem properties of the sample matrix
• number of samples to be analysed
• time for analysis
• ease and convenience of method
• knowledge and skill required
• cost and availability of equipment
• cost analysis

Question 16

What is instrumentation selection based on?

Answer 16

• if the instrument will do the task and give the info required as determined by the figures of merit of the instrument

Question 17

What are the figures of merit (total 6)

Answer 17

1. precision
2. bias
3. sensitivity
4. concentration range
5. detection limit
6. selectivity

Question 18

Define the figure of merit, precision

Answer 18

• measure of the random error as defined by the absolute and relative standard deviations std dev of the mean, coefficient of variation and variance

Question 19

Define the figure of merit, bias

Answer 19

absolute and relative determinate (systematic) error

Question 20

Define the figure of merit, sensitivity

Answer 20

calibration and analytical sensitivity

Question 21

Define the figure of merit, detection limit

Answer 21

blank plus three times the std dev of a blank (many definitions)

Question 22

Define the figure of merit, concentration range

Answer 22

limit of quantitation (LOQ) to limit of linearity (LOL)

Question 23

Define the figure of merit, selectivity

Answer 23

coefficient of selectivity

Question 24

What is meant by spectroscopy

Answer 24

• referring to “optical” spectroscopy
• involves energy changes in matter (atoms, ions, molecules) due to absorption, emission, fluorescence, reflection, scattering, etc of electromagnetic radiation
• can be considered the study of eectromagnetic radiation

Question 25

What is included in the spectroscopic category?

Answer 25

gamma ray, x-ray, UV/VIS, IR, microwave, electron spin, NMR, radio wave

Question 26

Why is mass spectroscopy NOT an optical spectroscopic method?

Answer 26

because it involves the interaction of electrons and ions with matter and the separation and detection of the resulting fragmentation ions and/or molecular ions results in spectra showing peaks for various components

Question 27

Define spectrophotometer

Question 28

Define spectrometer

Question 29

Define spectrograph

Question 30

Define spectroscope

Question 31

Explain what happens to electrons in the "normal" state

Answer 31

- electrons are in the lowest molecular orbitals | - molecule said to be in ground state aka sate with the lowest energy

Question 32

Explain what is meant by "excited state" of electrons

Answer 32

- when electrons gain energy (thermal energy, electromagnetic radiation), electron gets promoted to a higher molecular orbital - the valence electrons of molecule are in higher molecular orbital

Question 33

Explain quantized energy and the rules of quantum mechanics

Answer 33

- the molecular orbitals

Question 34

What is the nature of emr/What is emr?

Answer 34

- radiant energy/energy emitted by hot bodies like sun, electric bulb - has properties of both particles (called photons/ quanta) and waves