Analytical Methods Flashcards by Denisse Paderes

Spectrometry

Spectrophotometry, AAS, MS

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Luminescence

Fluorescence & Chemiluminescence

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Electromagnetic methods

Electrophoresis, Potentiometry & Amperometry

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Chromatography

Gas, Liquid, Thin-layer

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Photons of energy traveling in waves

Electromagnetic radiation

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E = hv

Planck’s formula

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Transmitted via electromagnetic waves that are characterized by their frequency & wavelength

Energy

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Distance between 2 successive peaks

Wavelength

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Number of vibrations of wave motion per second

Frequency

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400-700nm

Visible spectrum

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<400nm

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> 700nm

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Most common light source in visible & near-IF

Incandescent tungsten/tungsten-iodide lamp

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Light source used for UV

Deuterium & mercury arc

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Type of monochromator: A wide band of radiant energy & have decreased transmittance of the selected wavelength

Colored glass filter

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Type of monochromator: Principle of constructive interference of waves

Interference filters

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Type of monochromator: Narrow beam of light focused on a prism is refracted as it enters the denser glass

Simple glass prism

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Type of monochromator: Most commonly used; wavelengths bend as they pass a sharp corner

Diffraction gratings

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The presence of an intense static magnetic field will cause the wavelength of the emitted radiation to split into several components

Zeeman effect

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It is checked by didymium filter or cobalt chloride or potassium dichromate

Wavelength accuracy

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It is checked with quartz mercury arc lamp/transmission standards

UV spectro

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It’s checked by running different concentration of the same solution

Photometric linearity

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It’s checked with Nickel sulfate at 510nm

Photometric accuracy

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It detects baseline drift

Baseline stability

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Difference between the maximum wavelengths, excitation & emitted fluorescence

Stokes shift

The total range of wavelengths transmitted

Bandpass

The most commonly used photodetector

Photomultiplier tube (PMT)

Measures light at a multitude of wavelengths - detect less amount of light

Photodiode

Corrects absorbance caused by the color of the reagents

Reagent blank

Measures absorbance of the sample & reagent in the absence of the end product

Sample blank

It measures light emitted by a single atom burned in a flame

Flame Emission Photometry (FEP)

Internal standard used in FEP

Lithium/Cesium

It measures light absorbed by atoms dissociated by heat

Atomic Absorption Spectrophotometry

It is used to convert ions to atoms

Atomizer (Nebulizer/Graphite furnace)

It is added to samples in AAS to form stable complexes with phosphate

Lanthanum or strontium chloride

Most frequently used sources of excitation radiant energy in Fluorometry

Gas discharge lamps (mercury & xenon arc)

Most commonly used in filter fluorometers

Mercury vapor lamps

Large particles scattering light predominantly in the forward direction

Mie scatter

Small particles scattering light in all directions with maximum scatter forward & backward

Rayleigh scatter

It is used to determine the accuracy of reference & indicator electrodes, the stability of standard solution & the potentials of liquid junctions

Hydrogen electrode

E = I x R

Ohm's law

Opposing force to flow of electrons (in ohms)

Resistance

Electrical charge (in coulombs/second; measured in amperes

Current

The movement of buffer ions & solvent relative to the fixed support

Electroendosmosis/Endosmosis

Measuring electrical potential in voltage; follows the Nernst equation

Potentiometry

Measuring aspects of current, including rate of electron flow; often used in titration of ions; follows Faraday's law

Coulometry

Measuring current in amperes/current flow produced by an oxidation reaction

Amperometry

Measuring current at an electrode using a specific voltage generated at another electrode

Voltammetry

Measurement of current flowing as electrons are formed in an oxidation-reduction system

Osmometry

Reference electrode commonly used in potentiometry

Calomel

Frequently used electrode in potentiometry but disadvantage is it's slow to reach a new stable voltage; unstable above 80C

Mercury/Mercurous chloride

Another frequently used electrode in potentiometry; used for increased temperature up to 275C

Ag/AgCl

3 major ISE types

Inter metal, metal electrode & membrane electrode

Dioctylphenyl phosphonate

Calcium ISE

Valinomycin

Potassium ISE

Organic ionophore = monensin (from Streptomyces spp.)

Sodium ISE

Measured as tCO2

HCO3- ISE

Affect the charge of ampholytes

ph & ionic strength

Fundamental concept in Capillary Electrophoresis

Electro-osmotic flow (EOF)

Bulk flow of liquid toward the cathode upon application of an electric field & it is superimposed on electromagnetic migration

Electro-osmotic flow (EOF)

Type of chromatography: based on competition between sample & mobile phase

Adsorption/Liquid-solid chromatography

Type of chromatography: based on relative solubility

Partition/ Liquid-liquid chromatography

Elution strength of mobile phase is constant throughout the separation

Electron ionization

2 types of ionization for LC-MS

Electrospray Ionization (ESI) & Atmospheric Pressure Chemical Ionization (APCI)

Type of ionization: Passing the LC effluent through a capillary to which a voltage has been applied

ESI

Type of ionization: droplets aren't charged & the source contains a heated vaporizer to allow rapid desolvation of the drops

Atmospheric Pressure Chemical Ionization (APCI)

Allows only ions of a single selected m/z value to pass through the analyzer to the detector

Quadrupole MS

Specific masses can be selected to monitor a few target analytes

Selected Ion Monitoring (SIM)

It can also measure vit. D, testosterone & immunosuppresant drugs; can detect multiple analytes in one run

LC-MS

Separates solutes in the sample based on their solubility in the 2 phases as well as different electrical charges

Ion Exchange Chromatography

The relative distance of migration from the point of application

Retention factor (Rf)

It is based on fragmentation & ionization of molecules using a suitable sources of energy

Mass Spectroscopy

It separates molecules by migration through a pH gradient

Isoelectric focusing

Emission of light is created from a chemical or electrochemical reaction & not from absorption of electromagnetic energy

Chemiluminsecence

A 1 mOsm/kg has a freezing point depression of?

0.00186 C

Blood plasma (285 mOsm/kg) has a freezing point of?

-0.53 C

It is the measurement of differences in current at a constant voltage; follows Ilkovic equation

Polarography

LASER stands for:

Light Amplification by Stimulated Emission Radiation