CIH Analytical Chemistry

Question 1

What is a lab blank?

Answer 1

Samples that have not been sent tot he field. Used for laboratory quality control (negative control). NIOSH recommends analyzing 6 media blanks from the same sample lot.

Question 2

What is a field blank?

Answer 2

Sample media taken to the field, but not exposed.

Unexposed sampling media not taken to the field or shipped, but carried through the complete sample preparation and analytical procedure. Also known as a method blank.

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

When should field pumps be calibrated?

Answer 6

Before and after usage

Question 7

What is a primary standard?

Answer 7

Direct measurement of volume (sample pump, pilot tube, bubble meter)

Question 8

What is a secondary standard?

Answer 8

Calibration device calibrated against primary standard (rotameter)

Question 9

What is the limit of detection?

Answer 9

The LOC is the lowest concentration detected by a laboratory instrument. Generally, it’s 3x the instrument noise level (S/N > 3)

Question 10

What is the limit of quantification?

Answer 10

Lowest concentration quantifiable in the lab.

Question 11

Formula for concentration

Answer 11

concentration = mass / volume

Question 12

What is minimum airflow?

Answer 12

The minimum volume of air needed to ensure a measurable sample. Must have some idea of actual airborne concentration. Can use a threshold that you are interested in detecting.

Question 13

What are NIOSH sampling statistics rule of thumb?

Answer 13

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

Question 13

What are different laboratory analytical methods to measure fibers?

Answer 13

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

Question 14

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 14

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 15

Another name for lab blank

Answer 15

media blank

Question 16

PCM

Answer 16

• Phase contrast microscopy (pretty cheap microscopy)
• PCM does not differentiate between asbestos and other fibers.

Question 17

PLM

Answer 17

Polarized light microscopy. Only works for bulk samples. PLM Only really works for friable asbestos.

Question 18

TEM

Answer 18

• Transmission electron microscopy (terribly expensive microscopy)
• Necessary for asbestos clear out samples

Question 19

High performance liquid chromatography - what substances is it used for

Answer 19

PCBs, herbicides, insecticides, phthalates, isocyanates

Way to remember: P for pesticides, PCBs, phthalates

Question 20

What is high performance liquid chromatography?

Answer 20

Similar to gas chromatography except the carrier medium is a liquid. Contaminant must be in a soluble mobile phase

Question 21

What is ion chromatography?

Answer 21

A form of liquid chromatography that used ion-exchange resins to separate atomic or molecular ions based on their interaction with the resin

Question 22

What can ion chromatography be used on?

Answer 22

IONS. Can be used for anion and cationic species, ions of alkali and alkaline earth metals, inorganic compounds, and alehydes

Question 23

What law does UV absorbance follow?

Answer 23

Beer-lambert law

Question 24

How does UV absorbance work?

Answer 24

The amount of light absorbed is proportional to the concentration of the absorbing material

Question 25

What is a fluorescence detector?

Answer 25

Measures the emission of light by fluorescing elements. Light source raises energy of electrons that decay emitting light alt longer wavelengths

Question 26

What law does fluorescence detector use?

Answer 26

Beer-lambert law