Page:NIOSH Manual of Analytical Methods - 7701.pdf/1

 LEAD BY PORTABLE ULTRASONIC EXTRACTION/ASV Pb

MW: 207.19 (Pb) 223.19 (PbO)

CAS: 7439-92-1 (Pb) 1317-36-8 (PbO)

METHOD: 7701, Issue 2

RTECS: OF7525000 (Pb) OG1750000 (PbO)

EVALUATION: FULL

OSHA : 0.05 mg/m3 NIOSH: 0.05 mg/m3 ACGIH: 0.05 mg/m3

7701

PROPERTIES:

Issue 1: 15 January 1998 Issue 2: 15 March 2003 soft metal: d 11.3 g/cm3 @ 20 °C; MP 327.5 o C, BP1740 °C; valences 2+, 4+ in salts

SYNONYMS: elemental lead, lead compounds (except alkyl lead)

SAMPLING

MEASUREMENT

SAMPLER:

FILTER (37-mm, 0.8-:m pore, mixed cellulose ester membrane)

FLOW RATE:

1 to 4 L/min

VOL-MIN: -MAX:

20 L @ 0.05 mg/m3 1500 L

SHIPMENT:

Routine

SAMPLE STABILITY:

Stable

FIELD BLANKS:

Minimum of 2 field blanks per set

TECHNIQUE:

PORTABLE ANODIC STRIPPING VOLTAMMETRY

ANALYTE:

Lead

EXTRACTION:

10% HNO3, 10 mL; ultrasonication

ANALYSIS ALIQUOT VOL.:

0.1 to 5 mL

DEPOSITION POTENTIAL:

-0.8 V to -1.0 V vs. Ag/AgCl

ANODIC SWEEP:

REFERENCE ELECTRODE:

Deposition potential to 0.0 V vs. Ag/AgCl sweep rate variable [1,2]

Ag/AgCl or calomel

ACCURACY 3

RANGE STUDIED: 0.025 to 0.150 mg/m (as Pb) (based on Pb mass loadings) [4] BIAS:

None identified in laboratory studies[3-5] <10% in field study [6]

OVERALL PRECISION ( Ö r T ): 0.087 (screen-printed electrodes); 0.094 (Hg film on glassy carbon electrodes) [4] ACCURACY:

± 17.2 % (disposable electrodes); ± 19.3 % (renewable electrodes) [4]

WORKING ELECTRODE:

SUPPORTING ELECTROLYTE:

Mercury film on glassy carbon or screenprinted

Mixture of NaCl/NaOH or KCl/KOH, L-ascorbic acid

CALIBRATION:

Pb2 + in 5% HNO3

RANGE:

0.31 to >1000 :g Pb per sample [3,4]

ESTIMATED LOD: 0.09 :g per sample [3] PRECISION ( þ r ):

0.068 @ 60 :g (as Pb) per sample [3]

APPLICABILITY: The working range is (at least) 0.20 to 5.00 mg/m3 (as Pb) for a 120-L air sample. Lead determination by ultrasonic extraction/ASV method is applicable to the on-site, field-based determination of lead in air filter samples, and also may be used for laboratory-based air filter sample preparation and analysis. INTERFERENCES: Thallium is a known interference, but its presence is unlikely in the vast majority of samples. Extremely high concentrations of copper may cause a positive bias. Surfactants can poison electrode surfaces, so if the presence of surfactants is suspected they must be eliminated during sample preparation [7,8] OTHER METHODS: Laboratory-based methods include atomic spectrometric methods following concentrated acid hotplate digestion: NIOSH methods 7082 (flame AAS), 7105 (graphite furnace AAS), and 7300 (ICP-AES). ASTM standards based on NIOSH methods for sample collection, preparation and analysis have been published [9].

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition