Page:NIOSH Manual of Analytical Methods - 6600.pdf/1

 NITROUS OXIDE

N2O

MW: 44.01

METHOD: 6600, Issue 2

CAS: 10024-97-2

6600

RTECS: QX1350000

EVALUATION: FULL

OSHA : no standard NIOSH: 25 ppm ACGIH: 50 ppm (1 ppm = 1.80 mg/m 3 @ NTP)

Issue 1: 15 February 1984 Issue 2: 15 August 1994

PROPERTIES: gas; BP -88.46 °C; d = 1.53 (air =1)

SYNONYMS: hyponitrous acid anhydride; laughing gas.

SAMPLING SAMPLER:

AMBIENT AIR OR BAG SAMPLE

VOL-MIN: -MAX:

at least 2 spectrophotometer cell volumes no maximum volume

MEASUREMENT TECHNIQUE:

LONG-PATHLENGTH PORTABLE INFRARED SPECTROPHOTOMETER (FIELD READOUT)

ANALYTE:

nitrous oxide

SAMPLE STABILITY:

bag samples stable 2 h @ 25 °C

OPERATION:

according to manufacturer's instructions

BLANKS:

use uncontaminated air

ANALYTICAL WAVELENGTH:

4.48 µm

ACCURACY RANGE STUDIED:

10 to 1000 ppm

BIAS:

none known

PATHLENGTH:

0.5 m to 40 m (function of desired concentration range)

CALIBRATION:

closed-loop dilution of N 2O

RANGE:

10 ppm to > 1% N 2O in air

ESTIMATED LOD: ca. 1 ppm N 2O @ 10-m pathlength; varies with pressure and instrument PRECISION (Sr):

0.01 [1] (within-instrument)

ˆ ): 0.013 [1] OVERALL PRECISION (S rT (between-instrument) ACCURACY:

± 2.5%

APPLICABILITY: The working range of this method is 10 ppm (v/v) to more than 1% (v/v) N 2O. This method may be used for the sequential determination of two or more analyses by changing the analytical wavelength and pathlength.

INTERFERENCES: In common application (i.e., hospital, dental or veterinary operatory), there are no identified interferences.

OTHER METHODS: The criteria document on waste anesthetic gases [2] also describes an infrared method.

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