# Acids, Inorganic (7903)

​This method is considered historical and its use is no longer recommended. Please see the ‘Applicability’ Section for additional information. Revised: 15 July 2015.
ACIDS, INORGANIC
(1) HF; (2) HCl; (3) H3PO4;
(4) HBr; (5) HNO3; (6) H2SO4 METHOD: 7903, Issue 2
MW: Table 1
7903
CAS: Table 1
EVALUATION: FULL
OSHA : Table 1 NIOSH: Table 1 ACGIH: Table 1
Issue 1: 15 February 1984 Issue 2: 15 August 1994
PROPERTIES: Table 1
SYNONYMS: (1) hydrofluoric acid; hydrogen fluoride
(2) hydrochloric acid; hydrogen chloride
(3) phosphoric acid; ortho-phosphoric acid; meta-phosphoric acid
(4) hydrobromic acid; hydrogen bromide
MEASUREMENT
SAMPLER: SOLID SORBENT TUBE (washed silica gel, 400 mg/200 mg with glass fiber filter plug)
TECHNIQUE:
ION CHROMATOGRAPHY
ANALYTE:
F, Cl, PO4 3-, Br, NO3, SO42-
IC
FLOW RATE: 0.2 to 0.5 L/min
DESORPTION:
3L 100 L
10 mL 1.7 mM NaHCO3/1.8 mM Na2CO3
INJECTION LOOP VOLUME: 50 μL
HI ST OR
SHIPMENT: routine
SAMPLE STABILITY: stable at least 21 days @ 25 °C [1] BLANKS:
(5) nitric acid; aqua fortis (6) sulfuric acid; oil of vitriol
AL
SAMPLING
VOL-MIN: -MAX:
RTECS: Table 1
ELUENT:
1.7 mM NaHCO3/1.8 mM Na2CO3; 3 mL/min
COLUMNS:
HPIC-AS4A anion separator, HPIC-AG4A guard, anion micro membrane suppressor [2]
2 to 10 field blanks per set ACCURACY
RANGE STUDIED:
see EVALUATION OF METHOD
BIAS:
see EVALUATION OF METHOD
OVERALL PRECISION ( SˆrT ):
see EVALUATION OF METHOD
ACCURACY:
± 12 to ± 23%
CONDUCTIVITY SETTING: 10 μS full scale RANGE:
see EVALUATION OF METHOD
ESTIMATED LOD: see EVALUATION OF METHOD PRECISION (
S r ):
see EVALUATION OF METHOD
APPLICABILITY: This method should no longer be used and has been replaced by NIOSH methods 7906, 7907, & 7908. The replacement methods (7906, 7907, & 7908) allow for the collection of inhalable fractions of acid aerosols by means of a prefilter and can provide for lower limits of detection for acid gases and vapors due to higher sampling flow rates. The working range is ca. 0.01 to 5 mg/m3 for a 50-L air sample (see EVALUATION OF METHOD). This method measures the total concentration of six airborne anions. The corresponding acids may be collected on a single sampler and determined simultaneously. Formic acid has been determined by this method [3]. INTERFERENCES: Particulate salts of all the acids will give a positive interference. Chlorine or hypochlorite ion interfere with chloride determination and bromine interferes with bromide. Silica gel will collect ca. 30% of the free Cl2 and Br2 in an atmosphere [4]. Acetate, formate and propionate have elution times similar to F- and Cl-. If these anions are present, use a weak eluent (e.g., 5 mM Na2B4O7) for greater resolution. OTHER METHODS: This is P&CAM 339 in a revised format [5]. Alternate methods are NIOSH 7902 for fluoride [6] and P&CAM 268 for sulfate [7].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​ACIDS, INORGANIC: METHOD 7903, Issue 2, dated 15 August 1994 - Page 2 of 6
EQUIPMENT:
1. NaHCO3, reagent grade 2. Na2CO3, reagent grade 3. Distilled, deionized water, filtered through 0.45-μm membrane filter 4. Eluent: bicarbonate/carbonate buffer solution (1.7 mM NaHCO3/1.8 mM Na2CO3). Dissolve 0.5712 g NaHCO3 and 0.7631 g Na2CO3 in 4 L filtered deionized water 5. Calibration stock solutions, 1 mg/mL (as the anion). Dissolve salt in filtered deionized water a. Fluoride: 0.2210 g NaF/100 mL b. Chloride: 0.2103 g KCl/100 mL c. Phosphate: 0.1433 g KH2PO4/100 mL d. Bromide: 0.1288 g NaBr/100 mL e. Nitrate: 0.1371 g NaNO3/100 mL f. Sulfate: 0.1814 g K2SO4/100 mL
ST OR
IC
1. Sampler: glass tube, 11 cm x 7-mm OD, containing a 400-mg front section and 200mg backup section of washed silica gel, flamesealed ends with plastic caps. Front section is retained with a glass fiber filter plug. Urethane plugs separate and retain the backup section. Tubes are commercially available or may be prepared according to APPENDIX. 2. Personal sampling pump, 0.2 to 0.5 L/min,with flexible connecting tubing 3. Ion chromatograph, HPIC-AG4A anion separator and HPIC-AG4A anion micro membrane suppressor, conductivity detector, integrator and strip chart recorder. 4. Waterbath: hotplate with beaker of boiling water 5. Centrifuge tubes, 15-mL, graduated, plastic, with caps* 6. Syringes, 10-mL, polyethylene with luer tip 7. Filters, luer tip, with membrane filter, 13-mm, 0.8-μm pore size 8. Micropipettes, disposable tips 9. Volumetric flasks, 50- and 100-mL* 10. Laboratory timer 11. Bottles, polyethylene, 100-mL 12. Auto sampler vials (optional)
AL
REAGENTS:
detergent, rinse thoroughly with deionized water, to minimize anion blank values.
SPECIAL PRECAUTIONS:  Acids, particularly HF, are extremely corrosive to skin, eyes, and mucous membranes. HF will attack glass. Plastic labware is recommended. SAMPLING:
HI
1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break ends of sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. 3. Sample at an accurately known flow rate between 0.2 and 0.5 L/min for a total sample size of 3 to 100 L. NOTE: Do not exceed 0.3 L/min when sampling for HF. SAMPLE PREPARATION: 4. Score sampler with a file in front of primary sorbent section. 5. Break sampler at score line. Transfer glass fiber filter plug and front sorbent section to a 15-mL graduated centrifuge tube.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​ACIDS, INORGANIC: METHOD 7903, Issue 2, dated 15 August 1994 - Page 3 of 6
NOTE: Particulate salts of the volatile acids (HCl, HB, HF, and HNO3), if present in the air sample, will collect on the glass fiber filter plug. To estimate the concentration these salts, analyze the plug separately from the front sorbent section. 6. Place backup sorbent section in separate centrifuge tube. Discard urethane plugs. 7. Add 6 to 8 mL eluent to each centrifuge tube. Heat in boiling waterbath for 10 min. NOTE: Eluent used for desorption should be from same batch as the eluent used in the chromatograph to avoid carbonate/bicarbonate peaks near F- and Cl-. 8. Allow to cool, dilute to 10.0-mL volume with eluent. 9. Cap the centrifuge tube and shake vigorously. 10. Pour sample into 10-mL plastic syringe fitted with in-line filter. CALIBRATION AND QUALITY CONTROL:
IC
AL
11. Calibrate daily with at least six working standards covering the range 0.001 to 0.3 mg of each anion per sample. a. Add known aliquots of calibration stock solution to eluent in 50-mL volumetric flasks and dilute to the mark. b. Store working standards in tightly-capped polyethylene bottles. Prepare fresh working standards weekly. c. Analyze working standards together with samples and blanks (steps 12 through 14). d. Prepare a calibration graph for each anion [peak height (mm or μS) vs. concentration (μg per sample)].
ST OR
MEASUREMENT:
12. Set ion chromatograph to conditions given on page 7903-1, according to manufacturer’s instructions. 13. Inject 50-μL sample aliquot. For manual operation, inject 2 to 3 mL of sample from filter/syringe to ensure complete rinse of sample loop. NOTE: All samples, eluents and water flowing through the IC must be filtered to avoid plugging system valves or columns. 14. Measure peak height. NOTE: If sample peak height exceeds linear calibration range, dilute with eluent, reanalyze and apply the appropriate dilution factor in calculations. CALCULATIONS:
H
15. Determine the mass, μg, of anion found in the sample front (Wf ) and back (Wb) sorbent sections, and in the average media blank front (Bf ) and back (Bb) sorbent sections. 16. Calculate concentration, C, of acid in the air volume sampled, V (L):
C=
((Wf + Wb ) − (Bf + Bb ))F V
, mg/m3
where: F (conversion factor from anion to acid) = 1.053 for HF; 1.028 for HCl; 1.032 for H3PO4; 1.012 for HBr; 1.016 for HNO3; and 1.021 for H2SO4.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​ACIDS, INORGANIC: METHOD 7903, Issue 2, dated 15 August 1994 - Page 4 of 6
EVALUATION OF METHOD: The method was evaluated for hydrochloric, hydrobromic, nitric, phosphoric and sulfuric acids by laboratory generation of mixed acids [1]. Data for the individual analytes are:  Range Studied (mg/m ) 0.35 - 6 0.14 - 14 0.5 - 2 2 - 20 1 - 10 0.5 - 2
(%) 0.7 0.3 -0.9 2.0 2.0 2.4
Measurement Precision ( Sr ) 0.053 0.025 0.029 0.056 0.018 0.028
Accuracy (%) ±23.4 ±11.9 ±19.7 ±16.5 ±18.7 ±19.4
Estimated LOD [2] (µg per sample) 0.7 0.6 2.0 0.9 0.7 0.9
AL
Acid HF [8] HCl [9] H3PO4 [1] HBr [1] HNO3 [1] H2SO4 [1]
3
(µg/ sample) 0.5 - 200 0.5 - 200 3 - 100 3 - 960 3 - 500 3 - 100
Overall Precision ( SˆrT ) 0.116 0.059 0.096 0.074 0.085 0.087
IC
The method was field-evaluated at two electroplating facilities using side-by-side silica gel tubes and bubblers. The method was evaluated for hydrofluoric acid in 1983 using the silica gel tubes and impingers [8]. Recovery based on impinger collection was 106% with Sˆ of 0.116. The capacity of the rT silica gel sampler for HF was 820 µg. This is equivalent to an 8-h sample at two to three times the OSHA PEL. Samples were stable for at least 21 days at 25 °C. Updated analytical columns have been used by NIOSH for analytical sequences [2]. REFERENCES:
HI
ST OR
[1] Cassinelli, M. E. and D. G. Taylor. Airborne Inorganic Acids, ACS Symposium Series 149, 137-152 (1981). [2] DataChem, Inc. NIOSH Analytical Sequences #7546, #7357, and #7594 (unpublished, 1992). [3] DataChem Laboratories, NIOSH Sequence #7923-C,D (unpublished, Jan. 25, 1994). [4] Cassinelli, M.E. “Development of a Solid Sorbent Monitoring Method for Chlorine and Bromine in Air with Determination by Ion Chromatography.” Appl. Occup . Environ . Hyg. 6:215-226 (1991) [5] NIOSH Manual of Analytical Methods, 2nd. ed., V. 7, P&CAM 339, U.S. Department of Health and Human Services, (NIOSH) Publication No. 82-100 (1982). [6] NIOSH [1994] NIOSH Manual of analytical methods (NMAM). 4th ed. Eller P.M., Cassinelli, M. E., eds. Method NIOSH 7902, Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113 [www.cdc.gov/niosh/nmam/]. [7] NIOSH Manual of Analytical Methods, 2nd. ed., V. 5, P&CAM 268, U.S. Department of Health and Human Services, (NIOSH) Publication No. 82-100 (1982). [8] Cassinelli, M. E. “Laboratory Evaluation of Silica Gel Sorbent Tubes for Sampling Hydrogen Fluoride,” Am. Ind. Hyg. Assoc . J., 47(4) :219-224 (1986). [9] Cassinelli, M. E. and P. M. Eller. Ion Chromatographic Determination of Hydrogen Chloride, Abstract No. 150, American Industrial Hygiene Conference, Chicago, IL (1979). METHOD WRITTEN BY: Mary Ellen Cassinelli, NIOSH/DPSE.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​H
CAS, RTECS 7664-39-3 HF (20.01) MW7875000 7647-01-0, HCl (36.46) MW4025000 H3PO4 7664-38-2, (97.99) TB6300000 HBr 10035-10-6, (80.92) MW3850000 HNO3 7697-37-2, (63.01) QU5775000 H2SO4 7664-93-9, (98.08) W55600000
Acid and M.W.
1 mg/ m3
2 ppm
C5 ppm 1 mg/ m3 3 ppm
OSHA 3 ppm
TABLE 1. GENERAL INFORMATION.
1.491
2 ppm; STEL 4 ppm 1 mg/m3*, STEL 3 mg/m3
liquid
gas
Physical State gas
2 ppm; 2.58 STEL 4 ppm 1 mg/m3; (aerosol) STEL 3 mg/m3
-42.0
-88.5
21.0
-114.8
MP, (°C) -83.1
83
-66.8
260
-85.0
BP, (°C) 19.5
PROPERTIES
liquid
3.0
290
AL
liquid
gas
IC
1 mg/m3, 1 mg/m3, (aerosol) 3 STEL 3 mg/m STEL 3 mg/m3 C 3 ppm C 3 ppm 3.31
C 5 ppm
ACGIH C 3 ppm
3
mg/m = 1 ppm @ NTP 0.818
ST OR
NIOSH 3 ppm; 6 ppm STEL C 5 ppm
EXPOSURE LIMITS
1.84
1.50
2.16
1.7
1.194
Sp. Gr (liq.) 0.987
<0.0001 (<0.001)
0.39 (2.9)
>101 (>760)
0.0038 (0.03)
>101 (760)
VP @ 20 °C kPa (mm Hg) >101 (>760)
ACIDS, INORGANIC: METHOD 7903, Issue 2, dated 15 August 1994 - Page 5 of 6
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition ​ACIDS, INORGANIC: METHOD 7903, Issue 2, dated 15 August 1994 - Page 6 of 6
APPENDIX: SAMPLING TUBE PREPARATION Silica gel cleaning procedure: Add 500 to 600 mL deionized water, slowly and with stirring, to ca. 200 mL volume of silica gel in 1-L beaker. When exothermal reaction has subsided, heat in boiling waterbath for ca. 30 min with occasional stirring. Decant and rinse four to five times with deionized water. Repeat cleaning procedure and dry overnight in 100 °C oven until free flowing. If blank of silica gel shows impurities upon analysis by ion chromatography, repeat cleaning procedure.
HI
ST OR
IC
AL
Silica gel tubes: Pack glass tubes, 7-mm OD, 4.8-mm ID, 11 cm long, with 400 mg of 20/40 mesh washed silica gel in front section and 200 mg backup section. Use urethane foam plugs between sorbent sections and at back end. Hold front section in place with 6-mm diameter, 1-mm thick glass fiber filter plug (Gelman 66088).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition