Hydrogen Cyanide (6017)
HYDROGEN CYANIDE HCN
MW: 27.03
METHOD: 6017, Issue 1
6017
CAS: 74-90-8
RTECS: MW6825000
EVALUATION: PARTIAL
OSHA: 10 ppm (skim) NIOSH: STEL 4.7 ppm ACGIH: C 10 ppm (skin) (1 ppm = 1.105 mg/m3
Issue 1: 15 March 2003
PROPERTIES: gas; BP 26 ºC; vapor density 0.93 (air = 1.00); d(liq) 0.69 g/mL @ 20 ºC; VP 82.7 kPa (620 mm Hg) @ 20 ºC; explosive range 5 to 40% v/v in air
SYNONYMS: hydrocyanic acid, prussic acid, formonitrile
SAMPLING SAMPLER:
SOLID SORBENT TUBE (soda lime, 600 mg/200 mg) + glass fiber filter, 5-mm
FLOW RATE:
0.05 to 0.2 L/min
VOL-MIN: -MAX:
2 L @ 5 ppm 90 L
SHIPMENT:
routine
SAMPLE STABILITY:
at least 2 weeks @ 25 °C [1]
BLANKS:
2 to 10 field blanks per set
MEASUREMENT TECHNIQUE:
ION CHROMATOGRAPHY (IC) / DC AMPEROMETRY
ANALYTE:
CN!
DESORPTION:
10 mL deionized water; agitate; let stand 60 min
INJECTION LOOP VOLUME: 50 :L
ACCURACY RANGE STUDIED:
not determined
BIAS:
not determined
OVERALL PRECISION (Ö r T ):
not determined
ACCURACY:
not determined
ELUENT:
0.5 M NaAc 0.1 M NaOH 0.5% ethylenediamine
COLUMNS:
HPIC-AS7 or equivalent anion separator, HPIC-AG7 or equivalent anion micro guard
DETECTOR:
0.0 V applied Ag0 vs. AgCl reference
CALIBRATION:
standard solutions of KCN in 0.1 N NaOH
RANGE:
10 to 300 µg CN– per sample [2]
ESTIMATED LOD: 1 µg CN– per sample [2] PRECISION ( þ r ):
0.041
APPLICABILITY: The working range is 0.3 to 235 ppm (0.3 to 260 mg/m3 ) for a 3-L air sample. This method is applicable to STEL measurements. Particulate cyanides are trapped by the initial glass fiber membrane disk. This method is more sensitive and subject to fewer interferences than NIOSH Method 7904, which uses ion-specific electrode analysis [3].
INTERFERENCES: A high concentration of hydrogen sulfide gives a negative interference. Any component with the same retention time as cyanide will interfere.
OTHER METHODS: This method is based on NIOSH 6010 which uses the same collection procedure with a VISIBLE ABSORPTION detection system [4]. The method has been adapted for use with a Technicon Autoanalyzer [5]. NIOSH Method 7904 uses an ion-specific electrode for measurement and has been used to determine HCN in firefighting environments [6].
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition HYD RO GE N C YAN IDE: ME TH OD 6017, Issue 1, dated 1 5 Ma rch 2003 - Page 2 of 5 REAGENTS:
EQUIPMENT:
1. 2. 3. 4. 5.
1.
6. 7. 8.
9.
Potass ium cyanide, rea gen t grad e.* Sodium acetate trihydrate, A.C.S. grade. Ethylenediamine, 99%. Sodium hydroxide (Na OH ), reag ent grade .* Sodium lime (CaO + 5 to20% NaO H), reagent grade (Aldrich #26,643-4, or equivalent). Crush and sieve to 10/35 mesh. Store in capped conta iner.* W ater, deionized or distilled. Sodium hydroxide solution, 0.1 N.* Calibration stock solution. 1 mg/mL CN -: Dissolve 0.125 g KCN in 0.1 N NaOH in a 50-mL volumetric flask. Dilute to mark with 0.1 N NaOH. Standardize by titration with standard AgNO 3 solution (see APPE ND IX). Eluent, 0.5 M sod ium ace tate, 0.1 M N aO H, 0.5% ethylenediamine: Dissolve 60 g sodium acetate + 4 g NaOH pellets in 800 mL H 2O. Add 5 mL ethylenediamine. Bring to 1 L with distilled water.
- See SPECIAL PRECAUTIONS
2. 3. 4. 5.
6. 7. 8. 9. 10. 11. 12. 13.
Sam pler: Glass tube, 9 cm long, 7-mm OD, 5-mm ID, with plastic caps, containing two sections (front = 600 mg; back = 200 mg) granular soda lime 10/35 mesh, separated and contained with silanized glass wool plugs, with a 5-mm diameter glass fiber filter disk placed before the plug on the inlet side (SKC , Inc. 226-28, or equivalent). Personal sampling pump, 0.05 to 0.2 L/min, with flex ible conne cting tubing. DIONEX DX-500 or equivalent ion chromatograph. DIONEX ED-40 or equivalent electrochem ical detector. DIO NE X or equ ivalent a m pero m etry cell with silver working electrode and silver chloride reference. DION EX A S7 colum n with AG7 guard colum n or e quiva lent. Autosam pler. Autosampler vials. Vials, 15- to 20-mL, for sample preparation. In-line filters, 0.45-µm. Micropipettors with disposable tips. Flasks, volumetric, 25-, 50-, 100-, 1000-mL, with stoppers Pipettes, transfer, disposable.
SPECIAL PRECAUTIONS: HC N gas and cyanide particu late s are highly toxic and m ay be fa tal if swallowed, inhaled, or absorbed through the skin [7]. Soda lime and NaO H are very caustic [7]. Use gloves and a fume hood when handling these chemicals.
SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break end s of s am pler im m ediately before sa m pling. Attach sam pler to p ersona l sam pling pum p with flexible tubing. 3. Sam ple at a n ac curately kn own flow ra te betwee n 0.05 an d 0.2 L/m in for a total sam ple size of 0.6 to 90 L. 4. Ca p tube. Pa ck sec urely for shipm ent.
SAMPLE PREPARATION: 5. Score each sampler with a file. Break sampler at score line. 6. Transfer front and back sorbent sections to separate vials. Discard glass wool plugs separating and retaining sorbent sections. NOTE: An estimate of particulate cyanide may be obtained by analyzing the initial glass fiber filter disk as follows; however, no evaluation data are available for particulate cyanides determined in this m anner: a. Trans fer the glass fiber disk a nd glass woo l plug im m ediately behind it at the tube inlet to a third vial. b. Ad d 10.0 m L 0.1 N Na OH to each vial. c. Proceed with step 8. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition HYD RO GE N C YAN IDE: ME TH OD 6017, Issue 1, dated 1 5 Ma rch 2003 - Page 3 of 5 7. Add 10.0 mL deionized-distilled water to each vial containing a sorbent section and cap. 8. Allow to stand 60 minutes, with occasional agitation. Transfer to a 10-mL plastic syringe fitted with an in-line 0.45-µm filter. Collect the filtrate in a clean vial. (If samples are allowed to stand for a period of time filtration m ay not be ne ces sary.)
CALIBRATION AND QUALITY CONTRO L: 9. Calibrate daily with at least six working standards over the range 1 to 250 µg CN - per sample. a. Prepare a working standard solution, 1.00 µg/mL CN -, by diluting 100 µL of calibration stock solution to 100 mL with 0.1 N NaOH. b. Pip et 0.5-, 1.0 0-, 1.5 0-, 2.0 0-, and 2.50 -m L of the workin g stan dard solution into 25-m L volum etric flasks to produce 0.5-, 1.00-, 1.50-, 2.00-, and 2.50-µg CN - standards c. Analyze together with field sam ples and blank s (steps 12 throug h 14). d. Prepare calibration graph (peak height in nA vs. µg CN -). 10. Determine desorption efficiency (DE) at least once for each lot of soda lime used for sampling. Prepare at least three tubes at each of five levels plus three media blanks. a. Rem ove and disca rd back sorbent sec tion of a blank sam pler. b. Inject a known amount of calibration stock solution directly onto the soda lime with a microliter syringe. c. Ca p an d allow to stand o vern ight. d. Desorb (steps 5 through 8) and analyze together with working standards and blanks (steps 12 through 14). e. Prepare a graph of DE vs. µg CN - recovered. 11. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and D E graph are in control.
MEASUREMENT: 12. Set ion chromatograph according to manufacturer’s instructions to conditions given on page 6017-1. 13. Injec t 50-µ L sa m ple aliqu ot. Fo r m anu al ope ration, inject 2 to 3 m L of s am ple fro m 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. Me asu re pe ak heigh t. NOTE: If sam ple peak height ex ceeds linear calibration ran ge, dilute w ith eluent, reanalyze a nd apply the appropriate dilution factor in calculations.
CALCULATIONS: 15. Calculate the mass, µg, of CN - in an a liquot analyzed . App ly the app ropriate aliquot fac tor to calculate the mass, µg, of CN - in the original 10-mL solution. 16. Determine the mass, µg CN- (corrected for DE ), found in the sam ple front (W f) and back (W b) sorbent sections and in the averag e m edia blank front (B f) and back (B b) sorbent sections. If W b > W f/10, report breakthrough and possible sample loss. 17. Calculate conce ntration, C, of HCN in the air volume sam pled V(L).
where 1.039 = conversion factor, CN ! to HCN NOTE: :g/L / m g/m 3
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition HYD RO GE N C YAN IDE: ME TH OD 6017, Issue 1, dated 1 5 Ma rch 2003 - Page 4 of 5
EVALUATION OF METHOD: Only the analytical procedure was evaluated for this method. The sampler, the soda lime tube, was evaluated for NIOS H m ethod 6010 by sam pling the test atmosph eres of H CN generated from a com pressed m ixture of HCN in nitrogen [1]. The range of HC N conc entra tion wa s eq uivalen t to 2 to 15 m g/m 3 for a 3-L air sample. Twenty-two samples collected at 0.2 L/min for 15 minutes indicated overall precision Ö rT of 0 .07 6 with nearly 100% recovery. Breakthrough occurred after 40 minutes of sampling at a flow rate of 0.2 L/min at an HCN concentration of 148 m g/m 3. Sample tubes spiked with solutions of KCN and analyzed after storage indicated that the samples of cyanide ions were stable on the tube for at leas t 2 week s. Analysis of 22 tubes which were spiked with KCN standard solutions in the range 10 to 50 µg indicated a recovery of nearly 100% with a pooled precision of 0.041. Desorption efficiency may be poor, below 10 µg CN ! [6]. This ion ch rom atog raph ic (IC) proc edu re for the determination CN- was developed by W isconsin Occupational He alth Labortory (W OH L) in 1997 [2]. Desorption, quantifiable limit, and linear range were investigated and found com para ble to m ethod 6010 . W OH L also dem onstated that recovery below 10 :g was questionable.
REFERENCES: [1] W illiamson, George [1988]. Method Development Protocol and Backup Data Report on Hydrogen Cyan ide; Internal N IOS H/M RS B R epo rt. NIO SH (Un pub lished ) . [2] Dobson L, Popp D, Reichmann L [1997]. Development of an Automated, Pyridine-Free Method for Aeroso l Cyanide Com pounds and Hydroge n Cyanide. Unpu blished paper. [3] NIOSH [1994]. Cyanides, aerosol and gas: Method 7904. In: Eller PM, Cassinelli ME, eds. NIOSH Ma nua l of Analytical Metho ds, 4 th ed. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 94-113. [4] NIOSH [1994], Hydrogen Cyanide: Method 6010. In: Eller PM, Cassinelli ME, eds. NIOSH M anual of Analytical Metho ds, 4 th ed. Cincinnati, O H: U.S. De partm ent of He alth and H um an Servic es, Pu blic He alth Service, Cente rs for Diseas e Contro l and P reve ntion, N ationa l Institute fo r Occu pation al Safety and Health, DHHS (NIOSH) Publication No. 94-113. [5] DataC hem Laboratories [1990]. NIOS H Se quenc e #6837 -K, Unpub l. (Marc h 21, 1990). [6] W illiamson, George [1988]. Analysis of Air Samples on Project 166 (Firesmoke) on HCN; Sequence NIOS H/MR SB-636 6A. NIO SH.(U npublished). [7] NIOSH [1988]. NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards [1981]. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 88119. [8] DataC hem Laboratories [1990]. User C heck , NIOSH Seque nce #68 37-J, (Marc h 19,Unp ublished ).
METHOD WRITTEN BY: LeR oy Do bso n, W isconsin Oc cup ationa l Hea lth Lab orato ry, Madison, W I.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition HYD RO GE N C YAN IDE: ME TH OD 6017, Issue 1, dated 1 5 Ma rch 2003 - Page 5 of 5
APPENDIX: STANDARDIZATION OF CALIBRATION STOCK SOLUTION Titrate an aliquot of the cyanide standard stock solution (Reagent 12) with standard silver nitrate (AgNO 3) solution. The end point is the first formation of a white precipitate, Ag[Ag(CN) 2]. Calculate the cyanide concentration with the following equation: M c = 52.04 V a (M a/V c) W here:
Mc = Va = Ma = Vc =
cyanide concen tration (m g/m L). volume (m L) of standard silver nitrate solution. concentration (moles/L) of standard silver nitrate solution. volume (m L) of calibration stock solution titrated.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition