PREFINAL LABORATORY L1: TRACE ELEMENTS Flashcards
This technique for elemental analysis is widely used because of its sensitivity, wide range of elements covered, and relative freedom from interference
Inductively Coupled Plasma Mass Spectrometry (ICP-
MS)
3 most important components of atomic emission spectrophotometer (AES)
- source
- monochromator
- detector
For spectral dispersion of the radiation and separation of
the analytical line from other radiation. A wavelength selecting device of AES.
monochromator
Used in AES so sample is atomized at a sufficient
temperature to produce an excited-state species.
source
A component in AES that permits measurement of radiation
intensity
detector
The liquid sample that contains the element of interest is vaporized, converting it into _______ and delivered into the source.
aerosol
Why is the intensity of emitted radiation used for quantitative analysis of elements?
Because the intensity of the emitted
radiation is correlated to the concentration of the analyte, thus a basis for quantitation.
Currently, the most commonly used sources in AES
flame and inductively coupled plasma
Typical fuel gases in AES
hydrogen and acetylene
Oxidant gases in AES
air, oxygen, and nitrous oxide
In AES, where are the gases combined?
mixing chamber
A sample is also introduced into the mixing chamber using
what device which converts liquid into a fine spray?
nebulizer
What elemental analysis technique is capable of much
higher temperature compared to AES?
Inductively Coupled Plasma Atomic
Emission Spectroscopy (ICP-AES)
Analytical procedure for the quantitative determination of
elements through the absorption of optical radiation by
free atoms in the gas phase
atomic absorption spectroscopy (AAS)
AAS measures elements through absorption of optical radiation by free atoms in what phase?
gas phase
Typical radiation sources for AAS
- hollow cathode
lamps (HCLs) - electrodeless discharge lamps
(EDLs)
Ideal radiation source of AAS
hollow cathode
lamps (HCLs)
Radiation source of AAS that is used for volatile elements
electrodeless discharge lamps (EDLs)
4 most important components of AA spectrophotometer
- radiation (light) source
- atomizer
- monochromator
- detector
Through this AAS component, atoms of the element of interest in the sample are formed
atomizer
AAS component used for spectral dispersion of the radiation and separation of the analytical line from other radiation
monochromator
AAS component that permits measurement of intensity
detector
AAS component that emits the spectrum of the analyte element
radiation (light) source
Most common sources in AAS
- flame (FAAS)
- graphite furnace (GFAAS)
Graphite furnace (GFAAS) is also called as
flameless or
electrothermal AAS
Elements that FAAS measures
copper, iron, and zinc
Elements that flameless AA measures
selenium and cadmium
Tubes used in GFAAS. Most commonly used atomizer.
graphite tubes
Graphite tubes are made of and coated with
high-purity polycrystalline
electrographite and coated with pyrolytic
graphite
Why is graphite tube used
because it can be heated to a high temperature
by an electrical current
Common problem in AAS
analyte volatility depends on the molecular form of the analyte and the
sample’s matrix
Analyte volatility depends on the molecular form of the analyte and the
sample’s matrix. This limitation can be overcome through what substance?
Chemical modifiers
Examples of chemical modifiers
- palladium nitrate
- magnesium nitrate
- a mixture of both
Chemical modifiers are frequently added to?
samples, calibrators, and controls
3 important components of Inductively Coupled Plasma Mass Spectroscopy (ICP-MS)
(1) ion source
(2) mass analyzer
(3) ion detector
ICP-MS measures what ratio of the selected analyte ions?
mass-to-charge ratio
What is mass-charge ratio?
molecular
mass divided by ionic charge [m/z]
In ICP, it refers to an ionized gas (almost always argon), in which a certain proportion of electrons are free
plasma
In ICP-MS, this generates high temperatures, and dries and then vaporizes the droplets
produced by the nebulizer.
argon
The ICP-MS torches consist of how many concentric quartz tubes
3
Concentric quartz tubes are surrounded by a coil carrying a
radiofrequency (RF) power
In which tube in the torch, carries the argon (Ar) that forms the plasma?
The middle tube of the torch
Quantitative analysis for clinical samples is best performed with the use of
an internal standard
Usually
a solution of an uncommon element (such as yttrium) that
is different than the target element.
internal standard
A spectral interference, that generally result from a spectral overlap with the spectrum of the target analyte.
spectroscopic
A type of interference which involve the bulk physical properties of the sample to be analyzed.
nonspectroscopic
In nonspectroscopic interference, the properties of significance are?
- viscosity
- presence of easily ionized elements (EIE)
- presence of carbon
Anything that could interfere with atomization of the
sample could be classified as a spectral/nonspectral(?)
interference
nonspectral
Certain molecular species may have broad absorption spectra that may overlap the line spectra
of the elements of interest, leading to false elevations
of the target element concentrations.
This spectral interference can occur in what quantitative determination?
Atomic Absorption Spectroscopy (AAS)
In what quantitative determination, can spectral interference stem from:
- polyatomic species whose m/z may overlap the m/z of the target analyte
- nearby elements in the periodic table
- doubly charged ions
?
Inductively Coupled Plasma - Mass Spectroscopy (ICP-MS)
This correction in the AAS spectral interference relies on shifting the atomic spectral lines by the application of a magnetic field
Zeeman background collection
Arsenic predominant natural sources
- volcanoes
- weathering
of minerals
Main use of organic arsenic
wood preservative
T/F: Arsenic has various known function in human physiology
F (it has no known function)
Main routes of exposure of arsenic
- ingestion of arsenic-containing foods
- water and beverages
- inhalation of contaminated water
Arsenic is commonly found in what food
fish and seafood
Arsenic nontoxic organic forms
arsenobetaine and arsenocholine
Arsenic nontoxic organic forms like arsenobetaine and arsenocholine are cleared rapidly within how many days?
1-2 days
Main arsenic species in seafood and is the common cause for increased total arsenic
concentration in urine
Arsenobetaine
Toxic inorganic forms of arsenic
- Pentavalent [As(V)]
- Trivalent (As(III)]
- Methylated forms
- monomethyl arsine (MMA)
- dimethylarsine (DMA)
Arsenic methylated forms are formed by hepatic metabolism, and is less/more(?) toxic than As(C) & As(III)
less toxic
Methylated inorganic forms are eliminated slowly, within how many weeks?
1-3 weeks
What is the Biological Exposure Index for the sum of inorganic
and methylated metabolites of arsenic?
35 ug/L
Species of arsenic that is highly toxic
inorganic species
Species of arsenic that is intermediate in toxicity
methylated species
Species of arsenic that is relatively nontoxic
organic species
Most common poisons in human history
White powder of arsenic trioxide
Arsenic lethal dose
0.12-0.3g
How many grams of arsenic can produce toxic symptoms when ingested
0.01-0.05
Laboratory evaluation of arsenic status is primarily measured using what quantitative determination methods?
- ICP-MS
- GFAAS
- HGAAS
During acute exposure of arsenic, the preferred sample is
urine
During very recent exposure of arsenic (<24hrs), this sample may be helpful
serum (serum arsenic testing)
During chronic or post exposures (>3weeks), analysis of these samples may be useful
hairs or nails
A soft, bluish-white metal; easily cut with a knife
Cadmium
