Lead by Portable Ultrasonic Extraction/ASV (7701)
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 LEAD by ULTRASONIC EXTRACTION/ASV: METHOD 7701, Issue 2, dated 15 March 2003 - Page 2 of 4 REAGENTS:
EQUIPMENT:
1.
1. Sam pler: Mixed cellulose ester filter, 0.8-:m pore size, 37-mm diameter, in cassette filter holder. 2. Personal sampling pump, 1 to 4 L/m in, with flexible connecting tubing. 3. Field-portable anodic stripping voltam m eter. 4. D i sp os ab l e o r r e ne wa ble v o l t a m m e t r y electrodes. 5. Ultrasonic bath, 50 watts m inimum power. 6. Power source for ultrasonic bath. 7. Pla stic centrifuge tubes, 50-mL, with screw caps. 8. Te st tube rac k (s ize to fit in ultras onic bath). 9. Plastic sam ple cell container. 10. Mechanical pipets (class A equivalent), 0.1-mL to 10-mL, as needed. 11. Pipet tips for mechanical pipets. 12. Forceps 13. Bottles, polyethylene, 100- to 1000-mL. 14. Vo lum etric flasks, 100-mL (for preparatory lab work). 15. Plastic rods.
2. 3.
4.
5.
6. 7.
Nitric acid,* 10% (v/v) (Prepared from concentrated nitric acid, reagent grade; spectrosc opic grade if trace analysis). Distilled or deionized water (ASTM Type I or better [10]). Calibration stock solution, 1000 :g/m L Pb . Comm ercial standard, or dissolve 1.00 g Pb metal in minimum of 10 mL of 50% HCl and dilute to 1 L with 1% (v/v) HCl. Store in a polyethylene bottle. Stable for at least one year. Su pporting electrolyte : Aq ueous inert sa lt mixture such as 2.5 M NaCl and 0.25 M Na OH * (reagen t grad e or e quiva lent) [3,4 ]. Dissolved oxygen scavenger such as 0.25 M L-ascorbic acid (tissue culture grade or equ ivalent) [3,4]. Mercuric nitrate (reagent grade), if required (for Hg film electrodes). Certified Reference Materials (CRM s) for lead, prim ary or s econdary.
- See SPECIAL PRECAUTIONS
NOTE: Clean all glassw are and reu sable plasticware with diluted nitric acid and rinse thoroughly with distilled or deionized water before use.
SPE CIAL PR ECAU TIO NS: Nitric acid and sodium hydroxide are irritants and m ay burn skin. Perform extractions in a well-ventilated area. W ear gloves and eye protection.
SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in the line. 2. Sample at an accurately known flow rate between 1 and 4 L/min for up to 8 h for a total sample size of 20 to 150 0 L fo r TW A m eas urem ents . Do n ot excee d a filter loa ding of ca . 2 m g total dust.
SAMPLE PREPARATION: 3. Open the cassette filter holders and, with forceps, transfer the samples and b lank s to separate 50-m L centrifuge tubes. Push the filters to the bottom of the tubes with plastic rods. 4. Add 10 mL of 10% HNO 3 and cap the centrifuge tubes. 5. Place centrifuge tubes in ultrasonic bath, and agitate at room tem perature for at least 30 min. NOT E 1: The water level in the bath should be above the level of liquid within the centrifuge tubes. NOTE 2: Proper performance of the ultrasonic bath should be demonstrated before use. This can be accomplished by checking recoveries of lead from performance evaluation materials. 6. Shake tubes for 5 to 10 sec, and allow to settle.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD by ULTRASONIC EXTRACTION/ASV: METHOD 7701, Issue 2, dated 15 March 2003 - Page 3 of 4 CALIBRATION AND QUALITY CONTRO L: 7. Prior to field work, prepare a series of working standards covering the range 0.25 to 20 :g/mL Pb. a. Add aliquots of calibration stock solution to 100-mL volumetric flasks, and dilute to volume with 10% HNO 3. Sto re and transport the working sta ndards in polyeth ylene bottle s, a nd pre pare fresh week ly. b. Analyze the working standard s together with the blanks and sam ples (steps 11 through 14). c. Prepare a calibration graph of instrumental response vs. lead concentration (:g/m L Pb). NOTE: Some portable instruments read concentration d irectly. Calibrate acco rding to manufacturer’s directions. 8. Analyze at least one stan dard for every 20 sam ples to check for instrumen t drift (steps 11 through 14). 9. Check recoveries with at least one spiked media blank per 20 samples (one per batch minimum ). Use certified reference materials to substantiate recoveries. Use method of standard additions to check for matrix effects or interferences. 10. Check for lead contamination by analyzing at least one reagent and one media blank per 20 samples (m inimum of one per ba tch)(steps 11 through 14).
MEASUREMENT: 11. Set instrument parameters as specified by the manufacturer, or use conditions specified on page 7701-1. NOTE: If renewable electrodes are used, clean the glassy carbo n electrode and de posit a fresh m ercury film prior to conducting analyses. 12. Transfer sample aliquot (1 to 5 mL) to analytical cell, and dilute with 10% HNO 3, if necessary. NOT E: High concentrations of lead may require analysis of diluted analyte solutions. 13. Add supporting electrolyte and oxygen scavenger to sample cell. Ensure final volume of the cell is 5 mL (disposable electrodes) or 10 m L (renewab le electrodes) by diluting with distilled or deionized water. 14. Me asu re lead co nten t of the sam ple aliqu ot (:g/sam ple or :g/m L), an d rec ord th e res ult. NOTE 1: For renewable electrodes, rinse and drain electrochemical sample cell at least three tim es w ith distilled or de ionized wate r betw een sam ple runs. For disposable electrodes, us e a fresh plastic sam ple cell container for each sample analyzed. NO TE 2: If the m eas ured value is abo ve the linear ra nge of the standard s, dilute w ith 10% HNO 3, reanalyze, and apply the appropriate dilution factor in the calculations.
CALCULATIONS: 15. Using measured lead contents, calculate the corresponding concentrations (:g/mL) of lead in the original extra cted sam ple, C s, and average m edia blank , C b, from the calibration graph. NOT E: Be sure to account for dilution factors. 16. Using solution volum es (m L) of the sam ples, V s, and m edia blank s, V b, calcu late the con cen tration, C (m g/m 3), of lead in the air volume sa m pled, V (L):
NO TE : :g/mL / m g/m 3
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD by ULTRASONIC EXTRACTION/ASV: METHOD 7701, Issue 2, dated 15 March 2003 - Page 4 of 4 EVALUATION OF METHOD: This method was evaluated with lead aerosol samples generated in the laboratory (40 to 80 :g Pb per filter) [3], and with air particulate samples collected from workplaces where abrasive blasting of leaded paint on highway bridges was being conducted [4]. For the latter, lead loadings cover the range from below the detection limit of 0.09 :g Pb per filter to loadings in excess of 1500 :g Pb per filter [4 ]. The method also has been evaluated with performance evaluation materials and by interlaboratory testing [35]. Lead recoveries from Certified Reference Materials (CRM s) were found to be quantitative ($90%) and equivalent to recoveries obtained using confirmatory analytical methods (NIOSH 7082, 7105, and 7300 [11]).
REFERENCES: [1] Wang J [1985]. Stripping analysis. New York: VCH Publishers. [2] Wang J [1996]. Electrochemical preconcentration . In: Kissinger PT , Heinem an W R, Ed s. Laboratory Techniques in Electroanalytical Chemistry. 2nd ed. New York: Marcel Dekker. [3] Ashley K [1995]. Ultrasonic extraction and field-portable anodic stripping voltammetry of lead from environmental samples. Electroanalysis 7: 1189-1192. [4] Ashley K, Mapp KJ, Millson M [1998]. Ultrasonic extraction and field-portable anodic stripping voltammetry for the determination of lead in workplace air samples. AIHAJ 59:671-679. [5] Ashley K, Song R, Esche CA, Schlecht PC, Baron PC, Wise TJ [1999].Ultrasonic extraction and portable anodic stripping voltammetric measurement of lead in paint, dust wipes, soil, and air: An interlaboratory evaluation. J. Environ. M onit. 1:459-464. [6] Sussell A, Ashley K [2002]. Field measurement of lead in workplace air and paint chip samples by ultrasonic extraction and portable anodic stripping . J. Environ. Monit. 4:156-161. [7] Ashley K [1994 ]. Electroanalytical applications in occupational and environmental health. Electroanalysis 6:805-820. [8] Ashley K, W ise TJ, Mercado W , Parry DB [2001]. Ultrasonic extraction and portable anodic stripping voltam m etric m eas urem ent of lead in dus t wipe s am ples. J. Ha zard. M ater. 83:41-50. [9] ASTM [2003]. Standard Nos. E1613, E1741, E1775, E1979, E2051. In: Annual Book of ASTM Standards, Vol. 04.11. W . Conshohocken, PA: American Society for Testing and Materials. [10] ASTM [2003]. Standard No. D1193: Specification for reagent water. In: Annual Book of ASTM Standards, Vol. 11.01. W . Conshohocken, PA: American Society for Testing and Materials. [11] NIOSH [1994]. Lead: Method 7082, Lead by GFAAS: Method 7105, Elements: Method 7300. In: Eller PM, Cassinelli M E, E ds. NIOSH Manual of A nalytica l Meth ods (NMAM ). 4th ed. C incinnati, OH: National Institute for Occupational Safety and Health.
METHOD REVISED BY: Kevin Ashley, Ph.D., NIOSH/DART.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition