Page:NIOSH Manual of Analytical Methods - 7906.pdf/1

 PARTICULATE FLUORIDES and HYDROFLUORIC ACID by Ion Chromatography MW:	F-, 18.998 (HF, 20.01) METHOD:  7906, Issue 2

CAS (HF): 7664-39-3

RTECS: (HF) MW7875000

EVALUATION: FULL

U. S. OELs OSHA :	 	    2.5 mg/m3 (fluorides); 3 ppm (HF) NIOSH: 2.5 mg/m3 (fluorides); 3 ppm (HF), STEL (HF): 6 ppm Other OELs:   [1,2]

7906

Issue 2:	 20 May 2014 Issue 1:	 15 August 1994

HF: gas; mp = -83.1 °C; bp = 19.5 °C; sp. gr. 0.987; VP = 783 mm Hg (104.4 kPa). Fluoride salts liberate HF vapor in the presence of acids.

SYNONYMS: Hydrogen fluoride; hydrofluoric acid;    Sodium fluoride (CAS #7681-49-4) SAMPLING SAMPLER:	 PRE-FILTER, cellulose nitrate, 0.8 µm pore size, 37-mm diameter, + TREATED FILTER, cellulose nitrate impregnated with Na2CO3, 0.8 µm pore size, 37-mm diameter, separated by a chemically inert spacer

MEASUREMENT TECHNIQUE:

ION CHROMATOGRAPHY (IC) with conductivity detection

ANALYTE:

Fluoride ion (F-)

EXTRACTION:

Aqueous solution of sodium carbonate / sodium hydrogen carbonate

FLOW RATE:	 1 to 2 L/min VOL-MIN: -MAX:

15 L 1000 L

INJECTION VOLUME:

50 µL

SHIPMENT:	 4 °C

ELUENT:

SAMPLE STABILITY:	 Stable for at least 14 days (fluorides) / 28 days (HF) if stored at @ 20 °C for 7 days and 4 °C thereafter [1]

8 mM Na2CO3 / 1 mM NaHCO3 flow rate 1.0 mL/min

COLUMNS:

Pre-column, anion-exchange column and suppressor column

BLANKS:

CALIBRATION RANGE:

3 minimum field blanks per set ACCURACY*

RANGE STUDIED:	 0.04 to 5.9 mg/m3 (fluorides); 0.30 to 6 ppm (HF)

F-; 0.4 to 8.0 mg/L [3,5]

ESTIMATED LOD: 0.1 mg/L / 0.009 mg/m3 (120 L air volume; as F-) [3] PRECISION ( S ): Fluorides, 0.033; HF, 0.056 [3] r

BIAS*:

Negligible [3]

OVERALL PRECISION*( SˆrT ):	 Fluorides, 0.074; HF, 0.125 [5,6] EXPANDED UNCERTAINTY*:	 less than 20% for F-; less than 22% for HF [4,5]

rather than the traditional NIOSH accuracy criterion. APPLICABILITY:
 * Accuracy calculations were determined using reference 4

The working range is (at least) 0.1 to 8 mg/sample for a 250 Liter air sample.

INTERFERENCES: Co-sampled formate and acetate compounds in the work environment can cause a positive interference; thus detection by ion selective electrodes is a suitable alternative if airborne formate and acetate are expected. Cations that form insoluble fluorides, such as Ca2+, Fe3+, and Al3+ can cause negative interferences. Recovery of gaseous HF is reduced at high humidity.

NIOSH Manual of Analytical Methods (NMAM), Fifth Edition