TB_ Sampling and Sample Preparation

Question 1

Sampling type that eliminates questions of bias in selection
a. composite
b. stratified
c. systematic
d. random

Answer 1

d. random

Question 2

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

Answer 2

c. separatory funnel

Question 3

Mixtures of liquids and solids are usually separated prior analysis by
a. filtering
b.decanting
c. centrifuging
d. All of the above

Answer 3

d. All of the above

Question 4

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

Answer 4

d. All of the above

Question 5

. 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

Answer 5

b. Fusion technique

Question 6

Reliability of the results decreases with a decrease in the level or concentration of the:
a. matrix
b. analyte
c. reactant
d. product

Answer 6

b. analyte

Question 7

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

Answer 7

d. All of the above

Question 8

Primary sample preparation method for organics
a. Sonication
b. Acid-digestion
c. Extraction
d. All of the above

Answer 8

c. Extraction

Question 9

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

Answer 9

d. All of the above

Question 10

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

Answer 10

c. Glass and plastic

Question 11

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

Answer 11

d. All of the above

Question 12

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

Answer 12

a. Magnetic stirrer

Question 13

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

Answer 13

c. 6 months

Question 14

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

Answer 14

c. laboratory sample

Question 15

A change in the analytical signal caused by anything in the sample other than analyte.
a. matrix effect
b. interference
c. absorbance
d. transmittance

Answer 15

a. matrix effect

Question 16

Medium containing analyte.
a. reactant
b. matrix
c. solute
d. reference material

Answer 16

b. matrix

Question 17

The total error of an analytical result is the sum of
a. sampling
b. sample preparation
c. analytical errors
d. All of the above

Answer 17

d. All of the above

Question 18

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

Answer 18

a. 28 days

Question 19

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

Answer 19

d. All of the above

Question 20

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

Answer 20

a. Soxhlet extraction

Question 21

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

Answer 21

b. aqueous

Question 22

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

Answer 22

b. analyte

Question 23

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

Answer 23

c. sampling

Question 24

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

Answer 24

a. methodology

Question 25

Locating the adulterated portion of the lot for sampling is an example of
a. random sampling
b. selective sampling
c. composite sampling
d. stratified sampling

Answer 25

b. selective sampling

Question 26

Homogenization during sample preparation can be achieved using mechanical devices (e.g.,
grinders, mixers, slicers, blenders), enzymatic methods (e.g., proteases, cellulases, lipases) or
chemical methods (e.g., strong acids, strong bases, detergents).
a. mechanical devices (mixers, blenders, etc.)
b enzymatic methods
c. chemical methods
d. All of the above

Answer 26

d. All of the above

Question 27

Glass container is not suitable for
a. inorganic trace analyses
b. oil and grease determination
c. microbiological analyses
d. all of the above

Answer 27

a. inorganic trace analyses

Question 28

To increase/decrease analyte concentration, pre-concentration is needed for almost all trace
analysis, ________ is used for the analysis of highly contaminated samples so the concentration
falls within the calibration range.
a. centrifugation
b. separation
c. dilution
d. none of the above

Answer 28

c. dilution

Question 29

Chemical derivatization is used to increase or decrease volatility for _________ analysis
a. AAS
b. GC and HPLC
c. PCR
d. none of the above

Answer 29

b. GC and HPLC

Question 30

Acid digestion via hot-plate digestion or microwave-assisted is one way of sample preparation
in the analysis of
a. Total metal
b. Bioactive compounds
c. Alcohols
d. Sugars

Answer 30

b. Bioactive compounds

Question 31

GFAA (Graphite Furnace Atomic Absorption) do not use HCl since Cl- interferes. Diluted
______ acid is used.
a. Phosphoric Acid
b. Acetic acid
c. Nitric Acid
d. Sulfuric Acid

Answer 31

c. Nitric Acid

Question 32

Partitioning of analytes between water phase and organic phase
a. Liquid-liquid extraction
b. Soli phase extraction
c. Ultrasonic extraction
d. Pressured Fluid Extraction (PFE)

Answer 32

a. Liquid-liquid extraction