LEAD in DUST WIPES by Chemical Spot Test
9105
(Colorimetric Screening Method) Pb
MW: 207.19
METHOD: 9105, Issue1
CAS: 7439-92-1
RTECS: OF7525000
EVALUATION: PARTIAL
OSHA: no PEL NIOSH: no REL ACGIH: no TLV
PROPERTIES:
Issue 1: 15 March 2003 3
soft metal; d 11.3 g/cm ; MP 327.5 o C valences +2, +4 in salts
SYNONYMS: Elemental lead and lead compounds except alkyl lead
SAMPLING
MEASUREMENT TECHNIQUE:
CHEMICAL SPOT TEST, Rhodizonatebased solution or spot test kit applied to wipe sample [2]
Human skin (e.g., hands) or non-dermal surfaces (e.g., floors, walls, furniture)
ANALYTE:
Rhodizonate complex of lead
SAMPLE STABILITY:
Stable
POSITIVE INDICATOR:
BLANKS:
At least 5% of samples, min. of 2 per batch
SAMPLER:
WIPE, meeting the specifications of ASTM E1792 [1].
SAMPLE:
RESPONSE: ACCURACY RANGE STUDIED:
<0.01 to >1,000 µg Pb per wipe
BIAS:
Not applicable
OVERALL PRECISION ( Ö r T ):
Not applicable
ACCURACY:
Observed color change on wipe from yellow/orange to pink/red (under acidic conditions) [2,3] The method is ordinarily positive for the presence of lead in the range of 5 15 :g/sample, upwards to and exceeding milligram amounts [3,4].
Response may differ for different wipe materials, different matrices and different rhodizonate solutions.
APPLICABILITY: This is a qualitative, colorimetric screening method, designed for field use. The method was designed as a handwipe method for human skin, but is also applicable to various non-dermal surfaces including floors, walls, furniture, etc. A characteristic color change on the wipe (i.e., from yellow/ orange to pink/ red hues) indicates the presence of lead. By estimating the performance parameters for a given wipe/rhodizonate solution combination, the performance characteristics can be evaluated [5]. If quantitative results are needed, lead in the wipe samples can be measured on-site using a modification of NIOSH method 7701, or in a fixed-site laboratory using NIOSH methods 7082, 7105, 7300, or equivalent.
INTERFERENCES: Tl+ , Ag+ , Cd2 + , Ba2 + , and Sn2 + also form colored compounds with rhodizonate ion, but with less sensitivity than that of Pb2 + , and only the lead-rhodizonate complex gives the characteristic pink or red color [3]. Interferences from the wipe medium, e.g., surfactants, are possible.
OTHER METHODS: Laboratory methods for the determination of lead in dust wipes include modifications of NIOSH methods 7082 (Lead by Flame AAS), 7105 (Lead by Graphite Furnace AAS), 7300 (Elements by ACP), and 7701 (Lead by Portable ASV).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD IN DU ST W IPES: M ETH OD 9105, Issue 1, dated 1 5 Ma rch 2003 - Page 2 of 3 REAGENTS:
EQUIPMENT:
1.
1. Plastic pump spray bottles (fine spray preferred) with a capacity of at least 125 mL. 2. W ipes for sample collection, meeting the spe cifications o f AS TM E17 92 [1]. 3. Safety glasses or goggles. 4. Gloves, vinyl disposable or powderless latex gloves. 5. Scintillation vials, plastic screw top con tainers or plastic centrifuge tubes.
2.
3.
Vinegar (e.g., 5% ace tic acid as w hite vineg ar) or 1% nitric acid (v/v).* So dium or p ota ss ium rho dizo nate s alt (rhodizonic acid). NOT E: Rhodizonate solutions may degrade quickly over time. Solutions should be prepared fresh daily and kept refrigerated. Distilled or deionized water.
NOTE:
Com mercial kits are available.
- See SPECIAL PRECAUTIONS
SPE CIAL PR ECAU TIO NS: If 1% nitric acid is used, use common sense safety precautions when handling the solution (e.g., wear vinyl gloves, safety glasses/goggles, and avoid contact with clothing and exp osed sk in).
SAMPLING: Dermal surfaces (e.g., hands): 1. For workplace dermal sampling, tear open a wipe packet and without touching the wipe, offer the wipe to the employee to be evaluated. 2. Instru ct the em ployee to rem ove the wipe fro m the pack et, and un fold it. 3. Instruct the person to wipe the palms first, then the top surfaces of both sides of his or her hands (using normal hand washing pres sure). Tell the em ployee to wipe using the same side of the wipe, and to continue wiping his/her hands for a period of not less than 30 seconds. Other (non-dermal) surfaces: 4. Obtain wipe samples in accordance with ASTM E1728 [6], or use the following modification. a. W ith gloved hands, open a wipe packet and unfold the wipe. b. W ipe a delineated (known) area of the surface, being sure to cover the entire area thoroug hly. W ipe across the surface using repeated horizontal motions. c. Then wipe the same surface again using the same side of the wipe for sam pling, and w ipe at a right angle to the first wiping motion. d. Don a new pair of clean gloves for successive wipe samples.
SAMPLE PREPARATION: NOTE: The following procedure is written for sodium rhodizonate, and can be amend ed us ing potassium rhod izonate. Also , com m ercial spot test k its may be used to test for lead on wipe samples in lieu of the procedure described below, but sk in contac t with the rea gents should be avoided. 5. Prepare a solution of rhod izonic acid us ing the sod ium rhod izonate powder. Dissolve a pre-weighed portion of 0.135 grams (135 mg) in 105 cc of very cold water (~2 oC). This is the indicator solution. The indicator solution should turn an orange color when mixed. 6. Place a quantity of the indicator solution into one of the spray bottles, label the bottle: #2 or lead indicator solution. Refrigerate the remaining solution. 7. Fill another spray bottle with household vinegar or mak e up a 1% (v/v) nitric acid solution, label that bottle #1 or lead extraction solution. NOTE 1: The indicator solution will remain active for 2-3 days (if kept cold). After a time the indicator solution will begin to turn color (pale yellow) and lose viability, at which time a new solution NIOSH Manual of Analytical Methods (NMAM), Fourth Edition LEAD IN DU ST W IPES: M ETH OD 9105, Issue 1, dated 1 5 Ma rch 2003 - Page 3 of 3
8. 9. 10. 11.
must be m ixed. A new indicato r solution should be prepared at least daily, especially if not refrigerated at a very low temperature (approaching 0 oC). The lead disclosing solution should be k ept cold where pos sible (e .g., rec om m end to use a sm all cooler for field storage of indicator solution). NOT E 2: Alternative solutions and test indicato rs m ay be used, and this can alter the sen sitivity and selectivity of the test for lead. Place sample (wipe) on clean surface. Spray with 3 pumps of bottle #1 (vinegar) extraction solution. Spray wipe with 2 pum ps of bottle #2 (indicator solution). If sample turns red, lead is present. If no color change, sample is considered negative. NOT E 3: For quantitative analysis, see Method 7300 for ICP.
EVALUATION OF METHOD: The method has been evaluated preliminarily using ASTM E17 92 [1] wipes spiked with certified reference materials (CRMs), and has been found to give a positive response for at least ten micrograms of lead per wipe. The m ethod has also been subjected to limited field testing, and shows a positive response for at least a few tens of m icrogram s of lead per wipe. Extrem ely heavy soiling on the wipe could interfere with visualization of the red c olor chan ge d ue to dark ening of th e wipe, but the pink or red hues should still be visible around the area of the heaviest soiling, provided lead is present. Difficult matrices (e.g., dust wipes containing paint chips) may require leaching in dilute nitric acid before spot testing. Persons with color blindness may not be able to detect the pink or red hues characteristic of this spot test method.
REFERENCES: [1] ASTM [2002]. ASTM E1792-02, Standard specification for wipe sampling materials for lead in surface dus t. In: Annual Book of ASTM Standards, Vol. 04.11. W est Conshohocken, PA: American Society for Testing and Materials. [2] Es sw ein EJ, Boeniger M, Ashley K [2001]. Handwipe disclosing method for the presence of lead. U.S. Patent No. 6,248,593. [3] Feigel F, Anger V [1972]. Spot Tests in Inorganic An alysis. Am sterdam : Elsevier, pp. 282-287, 564-566, 569. [4] Ashley K, Fischbach TJ, Song R [1996]. Evaluation of a chemical spot test kit for the detection of airborne particulate lead in th e wo rkp lace. Am . Ind. H yg. Assoc . J. 57:161-165. [5] Song R, S chle cht PC, Ashley K [2001]. Field screening test methods — Performance criteria and perform anc e ch arac teristics . J. Ha zard. M ater. 83:29-39. [6] ASTM [2002]. ASTM E 1728-02, Standard practice for field collection of settled dust samples using wipe sampling methods for lead determ ination. In: Annual Book of ASTM Standards, Vol. 04.11. W est Conshohocken, PA: American Society for Testing and Materials.
METHOD WRITTEN BY: Eric J . Ess wein, NIO SH /DS HE FS , and Kevin Ashley, NIO SH /DA RT .
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition