TB_ Sampling and Sample Preparation Flashcards
Sampling type that eliminates questions of bias in selection
a. composite
b. stratified
c. systematic
d. random
d. random
When aqueous and nonaqueous liquids are combined, they usually form an immiscible mixture,
such as oil and water.
A ________ helps in separating the liquids into two samples.
a. pipet
b. beaker
c. separatory funnel
d. rotary evaporator
c. separatory funnel
Mixtures of liquids and solids are usually separated prior analysis by
a. filtering
b.decanting
c. centrifuging
d. All of the above
d. All of the above
Pre-treatment of solid samples prior analysis.
a. Leaching and extraction of soluble components
b. Filtering of mixtures of solids, liquids and gases to leave particulate (solid) matter
c. Grinding
d. All of the above
d. All of the above
. In the decomposition and dissolution of solids during sample preparation, which of the following is
expensive and often the last resort?
a. Acid treatment using oxidation
b. Fusion technique
c. Dissolution using ultrasound appropriate solvent
d. Simple dissolution
b. Fusion technique
Reliability of the results decreases with a decrease in the level or concentration of the:
a. matrix
b. analyte
c. reactant
d. product
b. analyte
Properties of nitric acid making it the preferred acid for digesting samples for the analysis of
metals
a. acts as a strong acid
b. as an oxidizing agent
c. does not form insoluble compounds with metals/nonmetals
d. All of the above
d. All of the above
Primary sample preparation method for organics
a. Sonication
b. Acid-digestion
c. Extraction
d. All of the above
c. Extraction
Possible sources of contamination during sample preparation include:
a. Reagents (tracers)
b.Glassware/equipment
c. Cross-contamination between high- and low-activity samples
d. All of the above
d. All of the above
Containers that should not be used for dry ashing because the elevated temperatures
exceed the melting point of these materials
a. zirconium
b. platinum
c. Glass and plastic
d. porcelain
c. Glass and plastic
The size of the sample taken for analysis depends on the concentration of the
a. analyte
b. equipment to be used
c. specific tests
d. All of the above
d. All of the above
Equipment commonly used to homogenize the contents of an open beaker.
a. Magnetic stirrer
b V-blenders
c. Ball and rod mills
d. tube rotator
a. Magnetic stirrer
The maximum holding time for acid preserved samples that will be subjected to determination of
metals is
a. 3 months
b. 1 week
c. 6 months
d. 48 hours
c. 6 months
A fraction of the sample actually used in the final laboratory analysis.
a. composite sample
b. sub-sample
c. laboratory sample
d. a, b and c
c. laboratory sample
A change in the analytical signal caused by anything in the sample other than analyte.
a. matrix effect
b. interference
c. absorbance
d. transmittance
a. matrix effect
Medium containing analyte.
a. reactant
b. matrix
c. solute
d. reference material
b. matrix
The total error of an analytical result is the sum of
a. sampling
b. sample preparation
c. analytical errors
d. All of the above
d. All of the above
The holding time for samples for metal determination preserved using nitric acid, 4 mL of dilute
3:1 is
a. 28 days
b. 2 weeks
c. 3 days
d. 1 year
a. 28 days
When samples cannot be dried because they decompose at the temperatures necessary to drive off the
water, the samples can be analyzed as
a. wet basis
b. dry basis
c. received basis
d. All of the above
d. All of the above
Organic components in solid samples are extracted from the matrix by continuously washing
the solid with a volatile solvent in a specialized piece of glassware
a. Soxhlet extraction
b. Ultrasonic extraction
c. Filtration
d. Rotary evaporation
a. Soxhlet extraction
In liquid-liquid extraction, it is often necessary to determine which liquid is aqueous and which
liquid is nonaqueous. To test the liquids, add a drop of water to the top layer. If the drop dissolves
in the top layer, the top layer is
a. nonaqueous
b. aqueous
c. miscible
d. denser
b. aqueous
It is important to discard containers that are scratched or abraded on their interior surfaces. The
internal surface area of a container, whether used for sample preparation or storage, may cause
loss of
a. matrix
b. analyte
c. weight
d. ash
b. analyte
Process by which a sample population is reduced in size to an amount of homogeneous material
that can be conveniently handled in the lab in which the composition is representative of the
population.
a. selection
b monitoring
c. sampling
d. segregation
c. sampling
As a general rule, the error in sampling and the sample preparation portion of an analytical
procedure is considerably higher than that in the
a. methodology
b treatment
c. preservation
d. subsampling
a. methodology
