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