Instrumental Analysis ACS Exam with Complete Solutions
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Instrumental Analysis ACS
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Instrumental Analysis ACS
Instrumental Analysis ACS Exam with Complete SolutionsInstrumental Analysis ACS Exam with Complete SolutionsInstrumental Analysis ACS Exam with Complete Solutions
Four Levels of Analytical Methodology - ANSWER-1. Technique- any chemical or physical principle we can use to study an analyte
2. Meth...
Instrumental Analysis ACS Exam with
Complete Solutions
Four Levels of Analytical Methodology - ANSWER-1. Technique- any chemical or
physical principle we can use to study an analyte
2. Method- application of a technique for a specific analyte in a specific matrix
3. Procedure- set of written directions telling us how to apply a method to a particular
sample
4. Protocol- set of stringent guidelines specifying a procedure that must be followed if an
agency is to accept the results
Domains of Data - ANSWER-1. non-electrical
2. electrical
Non-electrical Domains of Data - ANSWER-mass, length, volume, etc.
Electrical Domains of Data - ANSWER-Analog, digital, signal transduction, voltage,
current, etc.
Signal Transduction - ANSWER-Converting phys/chem info to an electrical signal, or
reverse process
Analog - ANSWER-Signal varies continuously and the magnitude of the signal is
followed in a continuous manner in the circuit or device (seismograph)
Digital - ANSWER-Magnitude of signal determined one instant in time, interpreted into a
series of bits, then the bits are manipulated/stored digital circuits in the instrument
Detector - ANSWER-Device that indicated a change in an environmental variable (P, T,
light level)
Transducer - ANSWER-Device that changes electrical to nonelectrical data or reverse
Quantifying Instrument Performance - ANSWER-1. Precision
2. Bias/accuracy
3. LOD (Limit of Detection)
4. LOQ (Limit of Quant.)
5. DR (Dynamic Range)
6. Sensitivity
7, Selectivity
, Precision - ANSWER-Standard deviation, average, relative standard deviation, standard
deviation of mean, variance
Bias - ANSWER-Presence of a systematic or determinate error in a measurement.
Determined by testing method on a known ref. material
Detection Limit - ANSWER-Min. conc. of an analyte that can be detected by an
instrument. Signal must be greater than the random noise (SD) of the blank. LOD =
3xSD
Dynamic Range - ANSWER-Range of conc. that the method can handle.
DR = LOL - LOQ
How are analytes excited? - ANSWER-1. e- bombardment (very high E, 70 eV EI)
2. Particle bombardment (lower E, 0-10 eV CI)
3. Electrical current or heat
4. EM radiation
5. Some exothermic chemical rxns
Continuum Spectra - ANSWER-When heated, all solids emit "blackbody radiation"
which depends on the temp. at which you hold the object, not the composition (lower
wavelengths with higher temp)
Atomic absorption - ANSWER-Spectra contain simple, clear lines, and most transitions
are with the valence electrons
Sensitivity - ANSWER-Ability to discriminate between small changes in analyte conc.
Many methods depend on a linear calibration curve, so sensitivity of the method
depends on slope of curve and SD (noise)
Selectivity - ANSWER-Degree to which the method is free from interference from other
components in the sample. Matrix dec. sel. inc.
Reflection of Radiation - ANSWER-When radiation passes at an angle through an
interface between two media it can reflect energy. Depends on the RI's of the two media
and the angle of the radiation on the interface.
Photoelectric effect - ANSWER-The emission of electrons from a material when light of
certain frequencies shines on the surface of the material.
Dark Current - ANSWER-Some current even when cathode and anode have same
potential; light gives enough E to get to anode and make current.
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