CIH Analytical Chemistry

Question 1

What is a lab blank?

Answer 1

• Have not been sent to the field
• Used for laboratory quality control (negative control)

Question 2

What is a field blank?

Answer 2

• Sample media taken to the field, but not exposed

Question 3

How many field blanks should you use when sampling?

Answer 3

2 field blanks per 10 samples with a max of 10 field blanks

Question 4

How many lab blanks does NIOSH recommend analyzing in one sample lot?

Answer 4

6

Question 5

What is the NIOSH recommendation on the total blanks (media + field) associated with 16 field samples?

Answer 5

10

Question 6

What is a blind spiked sample?

Answer 6

Samples spiked with a known quantity of a contaminant (positive controls). Used to verify the lab is providing accurate results.

Question 6

Examples of primary calibration standards

Answer 6

Pitot tube
Spirometer
Mariotti bottle
Bubble meter

Question 7

Examples of secondary calibration standards

Answer 7

Rotameter, critical orifice, wet test meter

Question 8

What is the limit of detection?

Answer 8

• lowest concentration detected by a laboratory instrument
• 3x the instrument noise level (S/N > 3)

Question 9

What is the limit of quantification?

Answer 9

Lowest concentration quantifiable in the lab

LOQ means the smallest amount of a substance we can accurately measure. It’s like saying, “I see it, and I know exactly how much is there.”

LOQ > LOD

Question 10

What are NIOSH sampling statistics rule of thumb?

Answer 10

≥ 6 samples required for valid estimate of confidence interval around the mean.
> 11 samples required to estimate variance.

Question 10

What are different laboratory analytical methods to measure fibers?

Answer 10

• Phase contrast microscopy (PCM)
• Polarized light microscopy (PLM)
• Electron microscopy
• Scanning electron microscopy (SEM)
• Transmission electron microscopy (TEM)

Question 11

A new sampling and analytical method was developed for chemical “x” in air. During testing, the new method measured an airborne concentration of “x” of 513 ppm, while the standard reference method measured a “true” concentration of 440 ppm. What is the bias of the new method?

Answer 11

K = 513/440 = 1.17

Bias is defined as the ratio of the measured value to the true value:
K = Cm/Ct
Where:
K = bias (dimensionless)
Cm = measured concentration
Ct = true concentration

Question 12

Another name for lab blank

Answer 12

media blank

Question 13

Substances used on mixed cellulose ester filters

Answer 13

Metals, asbestos, and oil mist (MAO)

Question 14

Substances used on glass fiber filters

Answer 14

• polynuclear aromatics (PNAs) and polycyclic aromatic hydrocarbons (PAH)
• coal tar pitch volatiles (CTPV)
• pesticides
• oil mist

Question 15

Substances used on PVC filters

Answer 15

Used for total weights (PVC filters don’t collect water). Silica, nuisance dusts, chromic acid

Question 16

Substances used on teflon filters

Answer 16

Benzidine
Warfarin
Anthrax
SARS
Polytetrafluoroethylene (PTFE)
Naphthalene (PNA)

Question 17

There are two kinds of passive monitors. Name the mechanism of operation

Answer 17

Diffusion and permeation

Question 18

Another name for a field blank

Answer 18

Method blank

Question 19

How much breakthrough is allowed in solid sorbent active sampling?

Answer 19

10%

Question 20

What is the most common adsorbent? (aka solid sorbent)

Answer 20

Activated charcoal