Reference method to measure releases of lead in particulate from stationary sources: chapter 4


2.1 Principle

Particulate matter collected in various sections of the sampling train is first weighed and then digested under reflux in aqua regia. The extracted lead is measured by flame atomic absorption spectrophotometry at 283 nm.

2.2 Accuracy and Precision (Analytical) for Lead Analysis

The accuracy of the analytical method depends to some extent on the quantity of the particulate matter collected, particularly in the case of low mass loadings where filter handling losses in the order of 5 mg may be significant. Otherwise, the estimated analytical accuracy is ± 3% with a precision value of less than 2% coefficient of variation.

2.3 Detection Limit of Lead

For a sample volume of 2.8 normal cubic metres (100 normal cubic feet) the detection limit for lead collected on glass fibre filters is approximately 50 μg/m3.

2.4 Interferences

A very limited number of inorganic ions (e.g., sulphate and phosphate) which form insoluble lead compounds have been found to interfere when present in large molar excesses over lead. The addition of EDTA has been shown to remove such interferences.

2.5 Apparatus

Analytical Balance
160-g capacity, capable of measurement to within 0.1 mg.

Top-loading Balance
1200-g capacity, capable of measurement to the nearest 0.1 g.

Atomic Absorption Spectrophotometer
With hollow cathode lead lamp and burner for air-acetylene flame.

Extraction Flasks
125 mL Erlenmeyer flasks with 24/40 ground glass joint.

Reflux Condensers
With 24/40 ground glass joint to fit Erlenmeyer flasks.

Hotplates

Glass Filtering Funnels
55 mm top ID, short stem.

Filter Paper
Whatman 541 or equivalent.

Graduated Cylinder
100 mL.

Volumetric Flasks
100 and 500 mL.

Pipettes
2,4,6,8 and 10 mL.

2.6 Reagents and Materials

Distilled or Deionized Water

Anti-bumping Granules

Aqua Regia
Mix one part of concentrated nitric acid (HNO 3) with three parts of concentrated hydrochloric acid (HCl) both reagent grade. Prepare no more than the amount needed (i.e., 250 to 500 mL).

Stock Lead Standard
100 μg/mL. Dissolve 0.1598 g of reagent-grade lead nitrate Pb(NO 3) 2 in about 700 mL of distilled water. Add 20 mL of concentrated nitric acid (HNO 3) and dilute to 1 L.

Working Lead Standards
  1. Lead Solution Standards
    Pipette aliquots of 2,4,6,8 and 10 mL of the stock lead standard solution into five, 100-mL volumetric flasks. Add 2 mL of aqua regia to each and dilute to volume with distilled or deionized water. A reagent blank is prepared by diluting 3 mL of aqua regia to volume in a 100-mL volumetric flask.
  2. Filter Sample StandardsPlace a glass fibre filter selected from the same lot as that used for the sampling program into each of a series of five, 125-mL Erlenmeyer flasks. Add to each flask 20 mL of aqua regia or alternatively, 7 mL of concentrated HNO3, 21 mL of concentrated HCl and 20 mL of deionized water. Attach the reflux condenser. Reflux for two hours, rinse the condenser with a small quantity of deionized water and remove the flask. Filter the contents of each flask into separate 500-mL volumetric flasks and dilute to volume. Using an appropriate mechanical pipettor, pipette a 20-mL aliquot of the filter blank solution into each of a series of five, 100-mL volumetric flasks. Pipette (separately) 2,4,6,8 and 10 mL of the 100 μg/mL stock lead standard into the five flasks. Add 2 mL of aqua regia to each volumetric flask and dilute to volume.

2.7 Procedures

All analyses shall be performed in a clean laboratory equipped with a fume hood. The relative humidity of the room in which weighing is performed should be maintained at below 50%.

Lead solution standards are used for calibration unless stated otherwise.

2.7.1 Container No. 1 (Filter)

Transfer the filter and any loose particulate matter and filter material from the sample container to a tared weighing dish. Desiccate the sample to a constant weight (see note in Section 1.4.1) and record the result to the nearest 0.1 mg on the Particulate Analytical Data Sheet (Figure 4). Transfer the filter and particulate matter to a 125-mL Erlenmeyer flask. Rinse the petri dish with 20 mL of distilled water and add the rinse water through a short-stem funnel to the flask. Add a small quantity of anti-bumping granules and 25 mL of aqua regia. Attach the reflux condenser, reflux for two hours and rinse the condenser with distilled or deionized water. Filter the flask contents while still hot into a 500-mL volumetric flask and dilute to volume with distilled water. Filter sample standards are used for calibration.

Figure 4: Particulate Analytical Data Sheet

Particulate Analytical Data Sheet

A 10- to 50-fold dilution of the solution may be required to determine lead in the linear working range (1 to 10 μg/mL) of the spectrophotometer. Where such dilutions are made, the solution should be acidified to 2% aqua regia content. Record the weight of lead found on the Lead Analytical Data Sheet (Figure 5).

Figure 5: Lead Analytical Data Sheet

Lead Analytical Data Sheet

2.7.2 Container No. 2 (Nozzle, Probe, Liner, Cyclone, and Front-half of Filter Holder Washings)

Note the liquid level in the container (see Section 1.5.2) and determine if leakage occurred during transport. If there is a loss of sample, the test is invalid. Allow the acetone wash to evaporate in the container to a volume of approximately 30 mL before transferring the contents with several acetone rinses to a tared 125-mL Erlenmeyer flask. Evaporate to dryness at room temperature and pressure and desiccate to a constant weight (see note in Section 1.4.1). Record the weight to the nearest 0.1 mg on the Particulate Analytical Data Sheet (Figure 4). Add 20 mL of water to the flask and 25 mL of aqua regia. Attach the reflux condenser, reflux for two hours and rinse the condenser with distilled or deionized water. Filter the contents (while hot) into a 500-mL volumetric flask. Dilute to volume and prepare such dilutions from this solution as may be required to measure lead in the linear working range of the spectrophotometer. Diluted solutions should be acidified to 2% aqua regia content. Record the weight of lead found on the Lead Analytical Data Sheet (Figure 5).

2.7.3 Container No. 3 (Acetone Blank)

Note the liquid level and determine if leakage occurred during transport. Measure the volume of the acetone blank to the nearest 1 mL and enter the value on the Particulate Analytical Data Sheet (Figure 4). Place the solution in a small tared beaker. Evaporate the solution to dryness at room pressure and temperature (or at an elevated temperature using a steam bath). Desiccate the acetone blank sample to a constant weight (see note in Section 1.4.1). Enter the results to the nearest 0.1 mg on the Particulate Analytical Data Sheet.

2.7.4 Container No. 4 (Impinger Solution)

Note the liquid level and determine if leakage occurred during transport. Measure the volume of the solution to the nearest mL and enter the value on the Particulate Analytical Data Sheet (Figure 4). If chemical analysis of the impinger liquid is required by regulations, the combined first and second impinger contents are filtered through a Whatman 541 filter paper. The filtrate is then analyzed directly by flame atomic absorption spectrophotometry. The Whatman filter is transferred to a 125-mL Erlenmeyer flask. Add 20 mL of distilled water and 25 mL of aqua regia and a small quantity of anti-bumping granules. Reflux for two hours and rinse the condenser with distilled water. Filter the flask contents while still hot into a 500-mL volumetric flask and dilute to volume with distilled or deionized water. Prepare such dilutions from this solution as may be required to measure lead in the linear working range of the spectrophotometer. Diluted samples should be acidified to 2% aqua regia content. Record the weight of lead found in the impinger catch on the Lead Analytical Data Sheet (Figure 5).

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