Page:NIOSH Manual of Analytical Methods - 9105.pdf/1

 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