Midterm Flashcards
Define what is meant by system (under study) (3)
- 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
Define analytical instrument (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
What are data domains?
- 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
Give examples of data domains
meter pointer, chart recorder, digital device
What are the two main classifications of data domains?
- non-electrical
2. electrical
What measurements do electrical domains have
analog (current, voltage, charge), time (frequency, pulse width, phase), digital (count, serial, parallel)
What measurements do non-electrical domains have?
physical and chemical (mass, length, temp, colour), scale position, number (digital measurement)
What is the measurement
- 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
How can the measurement be in the electrical domain?
- can be encoded through an input transducer
What is the out-put transducer
the read-out device that converts data in the electrical domain to the non-electrical domain
Define transfer functions of the transducers
- mathematical relationships between the input transducer and the electrical signal and the out-put
Define detector
mechanical, electrical or chemical device that identifies, indicates, or records a change in a variable of the system
Define transducer
- 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
Define sensor
- device capable of monitoring chemical species continuously and reversibly
- has a transducer with a substance that responds to physical or chemical characteristic of analyte
What information is required for selecting an analytical method (name 5 of 11)
- 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
What is instrumentation selection based on?
- if the instrument will do the task and give the info required as determined by the figures of merit of the instrument
What are the figures of merit (total 6)
- precision
- bias
- sensitivity
- concentration range
- detection limit
- selectivity
Define the figure of merit, precision
- measure of the random error as defined by the absolute and relative standard deviations std dev of the mean, coefficient of variation and variance
Define the figure of merit, bias
absolute and relative determinate (systematic) error
Define the figure of merit, sensitivity
calibration and analytical sensitivity
Define the figure of merit, detection limit
blank plus three times the std dev of a blank (many definitions)
Define the figure of merit, concentration range
limit of quantitation (LOQ) to limit of linearity (LOL)
Define the figure of merit, selectivity
coefficient of selectivity
What is meant by spectroscopy
- 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
What is included in the spectroscopic category?
gamma ray, x-ray, UV/VIS, IR, microwave, electron spin, NMR, radio wave
Why is mass spectroscopy NOT an optical spectroscopic method?
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
Define spectrophotometer
Define spectrometer
Define spectrograph
Define spectroscope
Explain what happens to electrons in the “normal” state
- electrons are in the lowest molecular orbitals
- molecule said to be in ground state aka sate with the lowest energy
Explain what is meant by “excited state” of electrons
- 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
Explain quantized energy and the rules of quantum mechanics
- the molecular orbitals
What is the nature of emr/What is emr?
- radiant energy/energy emitted by hot bodies like sun, electric bulb
- has properties of both particles (called photons/ quanta) and waves
