Page:NIOSH Manual of Analytical Methods - 7907.pdf/1

 VOLATILE ACIDS by Ion Chromatography

7907

(Hydrogen Chloride, Hydrogen Bromide, Nitric Acid) Formulae:

HCl; HBr; HNO3

METHOD:  7907, Issue 1

MW: Table 1	 CAS:	 Table 1 EVALUATION:  FULL PROPERTIES:

U.S. OELs OSHA :	 		 Table 2 NIOSH:			  Table 2 Other OELs:  [1,2]

SYNONYMS:	 HCl: Hydrochloric acid, salt acid, muriatic acid;

SAMPLER:

Two (2) FILTERS in series separated with a chemically inert spacer: (1) pre-filter: 37-mm diameter quartz fiber filter; (2) sampling filter: 37-mm diameter quartz fiber filter impregnated with 500 µl Na2CO3 solution (1 M)

FLOW RATE: 2 L/min VOL-MIN: -MAX:

30 L 600 L

SAMPLE STABILITY: BLANKS:

Stable for 1 week @ 20 °C and 4 °C thereafter to at least 28 days [3]

RANGE STUDIED:

HCl: 0.04 to 1.6 mg/sample; HBr: 0.03 to 2.3 mg/sample; HNO3: 0.04 to 1.5 mg/sample

BIAS*:

Negligible [4]

OVERALL PRECISION ( SˆrT )*: HCl, 0.06; HBr, 0.06; HNO3, 0.07 [4] EXPANDED UNCERTAINTY*:

HNO3: azotic acid

TECHNIQUE:

ION CHROMATOGRAPHY (IC) with conductivity detection

ANALYTES:

Chloride (Cl-), bromide (Br -) and nitrate (NO3-) ion

EXTRACTION:

Aqueous solution of sodium carbonate / sodium hydrogen carbonate 25 µL

ELUENT:

3.1 mM Na2CO3 / 0.35 mM NaHCO3, flow rate 1.5 mL/min

COLUMNS:

Pre-column, anion-exchange column and suppressor column

3 blanks minimum per set ACCURACY*

Table 3

MEASUREMENT

INJECTION VOLUME:

SHIPMENT: Routine

Table 1

Issue 1:  20 May 2014

HBr: Hydrobromic acid;

SAMPLING

RTECS:

CALIBRATION RANGE: ESTIMATED LOD:

Chloride, bromide and nitrate at 0.4 mg/ mL to 4 mg/mL 0.003 mg/sample for all three acids; or 0.0012 mg/m3 for a 240 L air volume [4]

PRECISION ( Sr ):	 0.01 for all three acids [3]

Less than 12% for HCl and HBr; less than 14 % for HNO3 [3,5]

rather than the traditional NIOSH accuracy criterion. APPLICABILITY:
 * Accuracy calculations were determined using reference 5

The working range is (at least) 0.01 to 2.0 mg/sample for a 240 Liter air sample [3,4].

INTERFERENCES: Inorganic acids can react with co-sampled particulate matter on the pre-filter, leading to low results. One such example is in the galvanizing industry, where the presence of zinc oxide can be a major confounding factor in the measurement of HCl. Potentially interfering particulate chlorides and nitrates removed by the pre-filter can react with the sampled acids and liberate HCl and HNO3 that is subsequently collected on the sampling filter, leading to high results [6].

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition