Strategies For Selecting Air Sampling Methods

2011 AIHA-Florida Section Spring Conference

Course Outline

• What are we going to sample for

• Sampling media

• Active sampling, diffusive samplers, direct read instruments

Learning Objectives

• Use information on the MSDS to develop a practical step-by-step exposure assessment strategy to identify potential chemical exposures in the workplace and indoor air

• Determine the exposures when the information on the MSDS doesn’t cover the employee exposures

• Navigate the maze of sampling media possible to use for exposure assessment, and discuss the different ones available

• Differentiate between active and passive sampling including advantages and disadvantages of both type of media, and when they can and cannot be used

Getting Started: What Information Do We Need?

• What are we going to sample for?

• How are we going to sample?

– What analytical method?

– Active, passive, direct reading?

– What kind of media?

– How long? – What volume?

• Who will analyze the samples?

• What detection limit do we need?

If You Don't Know Where You

Are Going, Any Road Will Take

You There. Lewis Carroll, "Alice in

Wonderland"

What Are We Going to Sample for?

• Use information in old exposure reports

• Material safety data sheets (MSDS)

• Inventory data

• Multiple chemical profile analysis

– Mini can

– VOC profile

– Aldehyde profile

– Metals profile

• Direct reading instruments / detector tubes

What are we going to sample for?

MSDS Sheets

Chemical Name

CAS #

OELs

Inventory Data

Chemical Usage

Product Names

Old Reports

Past Exposures

Sampling Methods

Laboratory

Chemical Profiles

Mini Can

Organic Profile

Direct Read Instruments

Multi RAE

Detector Tubes

Miran SapphIRe

What Information Can We Find In An MSDS

• MSD sheets must list the hazardous chemicals (CAS #) that are found in a product in quantities of 1% or greater

• Or greater than 0.1% if the chemical is a carcinogen

• The MSDS does not have to list the amount of the hazardous

chemical present in the product.

Standard MSDS Information

• Product name • Incompatibilities • Hazardous ingredients

and exposure limits • Required personal

protective equipment (PPE)

• Health hazards • Exposure symptoms:

chemical routes of entry • Fire, explosion and

reactivity hazards

• Manufacturer • Precautions for safe

handling, storage and use

• Chemical characteristics • Disposal methods • Spill or leak procedures • Transportation

requirements • Regulatory reporting

requirements

• First aid procedures

Sources for MSDS Sheets

• Manufacturer or vendor

• Commercial pay-for-service databases

• Major chemical manufacturers or providers

What Is a CAS Number ?

• Stands for “chemical abstracts services” registry number

• A unique identifier that tells you methyl ethyl ketone and 2-butanone are the same compound

• Use CAS numbers when ever possible to avoid miss

identification of chemicals.

Ok, Let’s Say You Have Looked at All of These Sources, and You Still Can’t Discover What Chemicals You Are Looking for. What Do You Do Now?

Spock, this atmosphere

is highly toxic. Beam us out of

Here!

Exposure Profiles

What Are Exposure Profiles?

• Multiple chemical compounds that can be analyzed by a single analytical method

– GC, GC/MS, ICP/MS, IC

• And collected on a single type of media

– Charcoal, filter, treated media, canister

• And desorbed by a single method

– CS2, acid, thermal, etc

IAQ Organic Vapors – Minican

OSHA PV2120

Information You Can Get From A Minican

• Sub ppm levels of 63 volatile organics by GC/MS – OSHA pv2120 – Quantitative analysis – 5 ppb LOD for most compounds

• Library search for tentative identification compounds (115 K

spectral entries) – Estimated concentration only – Qualitative identification

• Sampling times from grab to 24 hrs.

Limitations-when Not To Use a Minican

• Dust

• Total hydrocarbons

– Gasoline, stoddard solvent, fuel oil

• Semi-volatile compounds

• Concentrations higher than 1 ppm

• Spills, confined spaces, head spaces

• Polymers

• Mercaptans, H2S

• MW less than 35

• Stack samples

Volatile Organic Profile - GC

• Modification of OSHA 7

• Some modifications use a “universal solvent”

– Increases recovery of polar compounds

• Dual 60 meter capillary columns

– 2nd polar column for confirmation

• 2 ug limit of detection

• Can be used with multiple charcoal media types

– Passive monitors

– Large and small charcoal tubes

When Should The Organic Profile Be Used?

• Concentration higher than 1 ppm

• Spills, confined spaces, head spaces

• Total hydrocarbons

– Gasoline, stoddard solvent, fuel oil

• Stack samples

• Whenever higher exposures are suspected

• Identification of unknown vocs ? ? ?

When Not to Use the GC/FID Organic Profile

• Complex hydrocarbon mixtures

• If you have no idea what you are looking for – totally unknown matrix

• Very low sub ppm levels

Inorganic Acids - NIOSH 7903

HF Hydrofluoric

Acid

HCl Hydrochloric

Acid

H3PO4

Phosphoric Acid

HBr Hydrobromic

Acid

H2SO4

Sulfuric Acid

Inorganic Acids - Sampling

• Collection media - washed silica gel

• Sampling rate - 0.2 - 0.5 lpm

• Max sample volume - 100 liters

• Analytical method - ion chromatography

Aldehyde Profile NIOSH 2016

Diisocyanate Profile OSHA 42 & 47

Isocheck

Polynuclear Aromatic Compounds

NIOSH 5506

ICPAES Inductively Coupled Plasma

Atomic Emission Spectroscopy

Atoms in the plasma emit light (photons) with characteristic wavelengths for each element. This light is recorded by one or more optical spectrometers and when calibrated against standards the technique provides a quantitative analysis of the original sample.

ICP-MS

• ICP-MS is an acronym for inductively-coupled plasma mass spectrometry

• Plasma : a state of matter containing electrons and ionized atoms

• These ions can then be separated according to mass, using a quadrupole analyzer, and detected, multiplied, and counted

• The principle of mass spectrometry is the separation and

counting of ions on the basis of their mass/charge ratio

Advantages of ICP/MS

• Provides excellent selectivity and sensitivity ten to ten thousand times lower than with conventional ICP and flame atomic absorption (AAS) techniques

• For most elements, detection limits are comparable to, or lower than, those attainable using graphite furnace AAS

• Produces a much wider dynamic range, isotope specific capability, and analysis on a cost-effective, simultaneous multi-elemental basis

• Spectral interference is greatly reduced compared to ICP-OES

Direct Reading Instruments and Detector

Tubes

• Be aware of positive and negative interference's for you analyte

• New instrumentation comes on the market every year

• Use only as a screening tool - limitations before use

• Always check results with validated air sampling methods

Multirae Plus PGM-50

• Industrial hygiene work

• Emergency response

• Confined space entry

• Measures up to 5 gases

– Simultaneously

• CO, H2S, O2, LEL, PID

Menu of Interchangeable Multirae Sensors

NH3

CO

HCN

H2S

NO

NO2

SO2

Cl2

Ammonia

Cyanide

Hydrogen Sulfide

Nitric Oxide

Nitrogen Dioxide

Sulfur Dioxide

Chlorine

Carbon Monoxide

Different Organic Chemicals Have Different Ionization

Potentials

• So we can differentiate between chemicals by changing lamp energies

• Benzene has an IP of 9.2 ev

• Isopropyl alcohol has an IP of 10.15 ev

• If we use an IP of say 9.5 we will measure benzene but

not isopropyl alcohol even when both are present

PID Characteristics

Sensitivity increases as the carbon number increases

10.2 ev lamp responds to > C4, olefins, all aromatics

And inorganics H2S, NH3, Br2, PH3, AsH3 9.5 ev lamp has higher response for aromatics, less for aliphatics

11.7 ev lamp greater for halogenated compounds, methanol, formaldehyde

Detector Tubes

• Detector tubes are designed to analyze samples of air and gases

•

• Sealed glass tubes are filled with a reagent specifically sensitive to a target gas

• If the target gas is present in an air sample drawn through the tube, a color change will occur in the tube’s

reagent layer.

Miran Sapphire

Miran Sapphire

• Uses infra red spectroscopy detection

• Industrial hygiene applications

• Emergency response analysis

• Indoor quality studies

• Fume hood containment analysis

• Data logging capability

• Portable

Miran Thermomatch

• Identifies unknown airborne chemicals

• Stores infra red absorption data

• Downloads data to PC

• Performs library correlation of 150 chemicals

• Lists most appropriate matches

Sampling Media

What is a Diffusive Sampler?

It is an air-sampling device that samples at rates controlled by molecular diffusion of gases and vapors through a membrane and a static air layer without

the use of a sampling pump

Advantages of Diffusive Sampling

• Convenient, no sampling pump

• Small and intrinsically safe

• Can be used by relatively untrained personnel

• Promoted as equivalent, alternative, supplemental to active sampling

Disadvantages of Passive Monitors

• Sampling rates are fixed by sampler geometry

• Sampling rates affected by face velocity

• Method validation is expensive

• Sampling rates are low compared to active sampling methods

• Only works for gases and vapors

Applications of Diffusive Sampling

• Not the “be all, end all” • Best applications are moderate to semi-volatile organic substances • Use OSHA web site (osha.gov) to find OSHA tested applications

Attendant to Diffusive Sampling

• Every different chemical substance has a different sampling rate for every different brand diffusive sampler

• Accurate sampling rates can only be determined through laboratory work

• Using estimated sampling rates is like using a sampling pump that has not been calibrated

When Using Diffusive Samplers Remember…

• They begin to sample immediately when packaging materials are

opened

• They continue to sample until resealed in packaging materials

• Report sampling site temperature and pressure

Active Sampling Media Advantages

• Flexible sampling rates

– User chooses sampling rate

• Wide variety of sampling media

– Dozens of media types available

• Simultaneous use of two or more media types

– Splitters

• Wide range of analytes

– Vapors, dust, aerosols, metals

Active Sampling Media - Disadvantages

• Labor intensive - limits number of samples taken

– Require some kind of pump

– Require pre and post calibration checks

• Subject to pump failures

– Batteries and pumps are subject to failure & fluctuation

• Pumps are heavy and noisy

– Especially high volume pumps

• Pumps are expensive

– Can cost over $1,000 per pump

• Pumps require regular maintenance

– Requires training and is time consuming

• Workers don’t like wearing pumps

Types of Active Sampling Media

• Charcoal

• Silica gel

• Tenax

• Xad

Charcoal

• Classic sampling medium

• Used for volatile organic compounds

• OSHA 7 / NIOSH 1500

• Carbon disulfide is desorption solvent of choice

• Number of passive samplers use charcoal

Tenax

• Polystyrene based polymer

• High surface area

• Very unreactive

• Compounds with boiling points between 50 and 200 C

• Very good for thermal or solvent desorption

Silica Gel

• Used for very polar compounds

– Alcohols, organic acids, amines

• Treated with derivatizing agents for reactive compounds

– Aldehydes, ammonia, cyanoacrylate, anhydrides

XAD

• Polystyrene/divinylbenzene copolymer

• Used for:

– Poly aromatic hydrocarbons(PNA)

– Chlorinated pesticides

• Treated with:

– HMP (2-hydroxymethyl piperidine) - aldehydes

– NITC (naphthylisothiocyanate) - amines

Questions ????

Contact Information: Ed Stuber - 877-549-0546 Estuber@galsonlabs.com