Page:NIOSH Manual of Analytical Methods - 7904.pdf/1

 CYANIDES, aerosol and gas

HCN and salts

MW: 27.03 (HCN); 65.11 (KCN)

METHOD: 7904, Issue 2

CAS: 74-90-8 (HCN); 151-50-8 (KCN) EVALUATION: FULL

OSHA : 11 mg/m 3; skin (HCN) 5 mg/m 3; skin (cyanides, as CN -) NIOSH: C 5 mg/m 3/10 min (as CN -) ACGIH: C 11 mg/m 3; skin (HCN); 5 mg/m 3; skin (cyanides, as CN)

7904

RTECS: MW6825000 (HCN); TS8750000 (KCN) Issue 1: 15 February 1984 Issue 2: 15 August 1994

PROPERTIES: HCN: gas, BP 26 °C; VP 620 mm Hg 20 °C; vapor density 0.94 (air = 1); KCN: solid, d 1.52 g/mL, MP 634 °C

SYNONYMS: HCN: hydrocyanic acid, prussic acid, formonitrile, cyanides.

SAMPLING SAMPLER:

MEASUREMENT

FILTER + BUBBLER (0.8-µm PVC membrane + 15 mL 0.1 N KOH) [1]

TECHNIQUE:

ION-SPECIFIC ELECTRODE

ANALYTE:

cyanide ion (CN -)

FLOW RATE:

0.5 to 1 L/min

EXTRACT FILTER:

VOL-MIN: -MAX:

10 L @ 0.5 mg/m 3 (as CN -) 180 L @ 11 mg/m 3 (as CN -)

RINSE BUBBLER:

SHIPMENT:

routine MEASURE:

SAMPLE STABILITY:

analyze within 5 days; particulate on filter may liberate HCN gas [2]

mV reading of cyanide ion electrode vs. reference electrode

CALIBRATION:

solutions of KCN in 0.1 N KOH

2 to 10 field blanks per set

RANGE:

0.05 to 2 mg CN -

ESTIMATED LOD:

2.5 µg CN - [2]

PRECISION (Sr):

0.043 (HCN) [3]; 0.038 (KCN) [2]

BLANKS:

ACCURACY RANGE STUDIED:

5 to 21 mg/m 3 (HCN) [3]; 2.6 to 10 mg/m 3 (KCN) [2]

BIAS:

- 7.6%

ˆ ): OVERALL PRECISION (S rT

0.062 (HCN) [3]; 0.103 (KCN) [2]

ACCURACY:

± 20.0%

25 mL 0.1 N KOH; 30 min

2 mL 0.1 N KOH; dilute to 25 mL with 0.1 N KOH

APPLICABILITY: The working range (as CN -) is 0.5 to 15 mg/m 3 for a 90-L air sample or 5 to 20 mg/m 3 for a 10-L air sample.

INTERFERENCES: Sulfide, chloride, iodide, bromide, cadmium, zinc, silver, nickel, cuprous iron and mercury interfere. In humid atmospheres, some particulate cyanide collected on the filter will liberate hydrogen cyanide which will be trapped in th e bubbler [2]. The method cannot distinguish between HCN formed in this manner and HCN originally present in air.

OTHER METHODS: This method combines and replaces Methods S288 [4], S250 [5], and P&CAM 116 [6]. Method 6010 (Hydrogen Cyanide) uses a soda lime tube as sampler, with colorimetric measurement.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94