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