Page:NIOSH Manual of Analytical Methods - 7401.pdf/1

 ALKALINE DUSTS

NaOH, KOH, LiOH, (NaOH) and basic salts

MW : 40.00 (NaOH); 56.11 (KOH) 23.95 (LiOH)

METHOD: 7401, Issue 2

CAS: 1310-73-2

RTECS: WB490000

1310-58-3 1310-65-2

EVALUATION: FULL

OSHA : 2 mg/m 3 (NaOH) NIOSH: C 2 mg/m 3/15 min (NaOH); Group I Pesticide ACGIH: C 2 mg/m 3 (NaOH)

7401

TT2100000 (KOH) OJ6307070 (LiOH) Issue 1: 15 February 1984 Issue 2: 15 August 1994

PROPERTIES: basic, hygroscopic, caustic solids and aerosols; VP not significant

SYNONYMS: alkali; caustic soda; lye; sodium hydroxide; potassium hydroxide

SAMPLING SAMPLER:

FILTER (1-µm PTFE membrane)

MEASUREMENT TECHNIQUE:

ACID-BASE TITRATION

ANALYTE:

OH - (alkalinity)

EXTRACTION:

5.00 mL 0.01 N HCl, 15 min under nitrogen with stirring

TITRATION:

0.01 N NaOH under nitrogen, endpoint by pH electrode

CALIBRATION:

0.01 N NaOH standardized with 0.01 N HCl

RANGE:

0.14 to 1.9 mg (as NaOH) per sample [1]

FLOW RATE: 1 to 4 L/min VOL-MIN: -MAX:

70 L @ 2 mg/m 3 1000 L

SHIPMENT:

routine

SAMPLE STABILITY:

at least 7 days @ 25 °C [1,2]

BLANKS:

2 to 10 field blanks per set

ESTIMATED LOD: 0.03 mg per sample (as NaOH) [1] (7 x 10 -4 moles of alkalinity) ACCURACY RANGE STUDIED:

0.76 to 3.9 mg/m 3 [1] (360-L samples)

BIAS:

5.6%

PRECISION (Sr):

0.033 @ 0.38 to 1.5 mg NaOH per sample [1]

ˆ ): 0.062 [1] OVERALL PRECISION (S rT ACCURACY:

± 16.2%

APPLICABILITY: The working range is 0.4 to 5.4 mg/m 3 for a 360-L air sample. The method measures total alkalinity of alkali hydroxides, carbonates, borates, silicates, phosphates, and other basic salts, expressed as equivalents of NaOH.

INTERFERENCES: Carbon dioxide in the air may react with alkali on the filter to produce carbonates but does not interfere when titrated. The carbonates will produce the equivalent amount of strong alkali that was consumed on the filter [1]. Acid a erosols may neutralize the sample, if present, producing a negative interference.

OTHER METHODS: This revises Methods S381 [2] and P&CAM 241 [3].

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94