Analytical Methods For Diesel Particulate Matter(DPM)

Igor Levin

OHAO - Fall Symposium

October 24th 2013 Toronto, Ontario

Acknowledgements

• Occupational Hygiene Association of Ontario.

• CANMET, Sudbury Laboratory.

• Sunset Laboratory Inc.

• National Research Council of Canada.

• Concord Analytical coworkers.

Analytical Services since 1997

• Respirable Quartz on Ag membrane filters by XRD

(Equivalent to NIOSH 7500).

• Metals by ICP (NIOSH 7300).

• Diesel Particulate Matter (NIOSH 5040).

Accredited by Canadian Association for Laboratory Accreditation (CALA)

to ISO 17025 for specific tests including NIOSH 5040.

Diesel Particulate Matter (DPM) is a complex aggregate of solid and liquid

material. Its origin is carbonaceous particles generated in the engine cylinder

during combustion. The primary carbon particles form larger agglomerates and

combine with several other, both organic and inorganic, components of diesel

exhaust. Generally , DPM is divided into three basic fractions.

The actual composition of DPM will depend on the particular engine and its

load and speed conditions. “Wet” particulates can contain up to 60% of the

hydrocarbon fraction (SOF), while “dry ” particulates are comprised mostly of

dry carbon.

DPM

Solids Dry carbon particles, commonly known as

soot.

SOF Heavy hydrocarbons

adsorbed and condensed on the carbon particles, called

Soluble Organic Fraction.

SO4 Sulfate fraction, hydrated sulfuric

acid.

Available DPM Analytical Methods

Respirable Combustible Dust (RCD) – Gravimetric

Thermal-Optical Carbon Analysis (NIOSH 5040)

Respirable Combustible Dust (RCD) Analysis

Sampling:

• Filter media: 25mm, 0.8 micron Silver Membrane filter.

• Flow Rate: 1.7 L/min

• Cyclone

Respirable Combustible Dust (RCD) Analysis

• Sampled filter is weighed and dust weight is determined.

• Filter is transferred to a metal tray.

• Tray is placed in muffle furnace at 400₀C for minimum 90 minutes. The ashing temperature and the catalytic action of the silver membrane filter combine to make the carbon-based dust react with Oxygen.

• The mass loss on ashing is considered to be the mass of RCD.

• Limit of Detection: 0.05 mg

Respirable Combustible Dust (RCD) Analysis

Advantages

• Simple • Economical • Resp. Quartz and RCD can be

done on the same filter.

Disadvantages

• Non Selective • Inadequate for compliance

monitoring at lower limits of exposure.

• Carbon based mineral dust interference.

• Sulfide minerals dusts interference.

• Problems with DPM overloaded filters.

Thermal-Optical Carbon Analysis (NIOSH 5040)

• Principle of Analysis: Two-phase heating of sample

with measurement of combustion gases.

• Low Limit of Detection:

– OC = 0.002 mg – EC = 0.002 mg

Equipment: Lab OC-EC Aerosol Analyzer by Sunset Laboratory Inc.

Description Tissuquartz Filters Filter Media Pure Quartz, no binder

Typical Thickness 432 μm

Typical Filter Weight 508 mg/cm2

Typical Water Flow Rate 0.35 bar (35kPa, 5 psi) 220 mL/min/cm2

Typical Air Flow Rate 0.7 bar ( 70 kPa, 10 psi) 73 mL/min/cm2

Maximum Operating Temperature - Air 1093 ₀C (2000 ₀F)

Typical Aerosol Retention ** 99.90 %

PH in Boiled water Extract 6.5 – 7.5

**Following ASTM D 2986-95A 0.3μm (DOP) at 32 L/min/100cm2 filter media.

Filter media for DPM sampling

Support pad choices (as per NIOSH 5040)

Cellulose: High OC blanks Stainless steel screen: Expensive, Potential OC

contamination during cleaning.

Pre-fired 37mm quartz fiber

filter: Low OC blanks, 0.006-0.014 mg.

Pre-fired quartz fiber filter, 37 mm, in a standard three piece holder.

Diesel Particulate Matter Cassette with Precision-jeweled Impactor.

• Screens out respirable particles > 1.0 µm.

Particles less than 1.0 µm are collected

on the filter.

• Filter diameter: 37mm

• Sampled area diameter : 32 mm

• Sampled area: 8.04 cm2

Collection of submicron particulates only eliminates mineral dusts interference

Source: http://www.cdc.gov/niosh/mining/UserFiles/workshops/dieselelko2007/3a-Petrie.pdf

Filter diameter: 37 mm Sampled area diameter : 33mm Sampled area: 8.55 cm2

Single punch : 1.5 cm2

2nd Punch

Filters are arranged in order of an increasing concentration of Elemental Carbon (EC) < 0.002mg – 0.278 mg

Schematic of thermal-optical instrument (V= valve) for determination of OC and EC in diesel particulate exhaust and other carbonaceous aerosols.

Instrument Calibration

10 μL of 1% or 0.5% of Sucrose (sugar) solution is deposited on a pre-fired

1.5 cm2 quartz fiber punch and dried for 10 minutes under a heating lamp.

NIOSH 5040 Protocol

Mode Temperature (₀C) Time (s) He 310 80 He 475 60 He 615 60 He 870 90

He / O2 550 35 He / O2 625 45 He / O2 700 45 He / O2 775 45 He / O2 850 45 He / O2 890 110

Total Time = 615

Thermogram of Sucrose Standard 42.10 μg OC

He 2% O2 / He

Calculated Results For Sucrose Standard 42.10 μg OC

OC/ EC Split Point for Sucrose Standard 42.10 μg OC

He 2 % O2 / He

OC/EC Split Point

Thermogram Of The Sample Containing Organic, Elemental & Carbonate Carbon

He 2% O2 / He

Calculated Results for a sample Containing Organic, Elemental & Carbonate Carbon

Standard Operating Procedure

• Wipe all the tools and Aluminum foil pad with Acetone.

• Turn on the instrument computer.

• Initiate Instrument software.

• Set Gas flows

• Light FID detector and wait 10 minutes.

• Load Five blank 1.5cm2 punches into the oven.

• Run “Clean” program .

“Clean” program

• Place four pre-fired punches on

the standards tray Aluminum pad. • Pipette two 10 μL aliquots of

each 1% and 0.5% of Sucrose solutions (42.10 μg and 21.05 μg of OC respectively).

• Dry punches under a heating lamp for 10 minutes.

Standard Operating Procedure

• Analyze blank punch using NIOSH

5040 protocol.

• Analyze 42.10 μg Spike

• Analyze samples

Standard Operating Procedure

Quality Control

• Daily QC checks

– Analyze cleaned blank punch. – Run alternatively 10μL of 0.5% and 1% Sucrose QC spikes every 8-10

samples. • Replicate Samples

– One replicate sample is analyzed for every 10 samples • Linearity Check

– Every six months Spikes of 10μL of 2%, 1%, 0.5% and 0.25% Sucrose are tested.

• Dextrose QC spike – New Sucrose reagent is tested with Dextrose solution to verify the

integrity of the reagent. • Annually Round Robin 47 mm filter is analyzed by CASL, CANMET & Sunset

Laboratory.

Uncertainty

Parameter associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measurant

(OC/EC /TC).

About 400 pairs of data that had been taken over an extensive period of time were analyzed by the method, kindly supplied by Dr. Paski to CANMET laboratory. The data were divided into ranges, as shown in the table on the following slide.

The uncertainties given by the instrument software provided by the manufacturer are: 0.2 μg /cm2 ± 5% for OC/EC and 0.3 μg /cm2 ± 5% for TC.

Uncertainty summary for 400 pairs of Analyzed filters

U- rel. at 95% confidence levels.

Range (μg/ cm2) Range (mg) Organic Carbon

(OC) U-rel. %

Elemental Carbon (EC)

U-rel. %

Total Carbon (TC)

U-rel. % 0.6 to 1.0 0.005 - 0.009 22 18 23

1 to 2 0.009 - 0.017 22 18 18

2 to 5 0.017 - 0.043 16 12 14

5 to 10 0.043 - 0.086 19 6 13

10 to 20 0.086 - 0.171 15 8 11

20 to 50 0.171 - 0.428 18 5 12

>50 > 0.428 _ _ 3

Filter diameter: 37 mm Sampled area diameter : 33mm Sampled area: 8.55 cm2

Issues

• Unknown filter media

• Wet filters

• Loose dust material

• Low instrument load

• DPM Overloaded filters

– Laser Radiation is almost fully absorbed by the EC. Split point can not be

determined accurately if the concentration of EC is greater than 25– 35

μg/cm2 (equivalent to 0.214 - 0.299 mg of EC on a 37 mm filter).

NRC System for the absolute calibration of black

carbon mass concentration measurement instruments

• The SAE E-31 Aircraft

Exhaust Emissions Measurement Committee has specified an instrument calibration methodology and schedule whereby NIOSH 5040 EC measurements are used to calibrate BC mass concentration instruments.

• NIOSH 5040 analysis performed by Concord Analytical Services.

CALIBRATION STABILITY/REPEATIBILITY

• One LII 300 instrument was calibrated by Missouri University of Science and Technology against NIOSH 5040 EC during a previous measurement campaign. The calibration results are shown below.

• Excellent agreement with calibrations performed by a different team and using a different NIOSH 5040 analysis provider

• No observable drift in the calibration over the one year period between the first and last calibration.

A-PRIDE 4 Pre-Test Correction Factor: 0.802

A-PRIDE 4 Post-Test Correction Factor: 0.798

8540 Keele Street, Unit 38 Concord, Ontario L4K 2N2

Canada Tel: 905-660-5171 Fax: 905-660-9474

Email: contact@concordanalytical.com www.concordanalytical.com