Page:NIOSH Manual of Analytical Methods - 3704.pdf/5

 PERCHLOROETHYLENE (portable GC) in exhaled breath and air: METHOD 3704, Issue 1, dated 15 January 1998 - Page 5 of 5

APPENDIX The volume of liquid perchloroethylene needed to createa calibration standard, if a commercial standard is not utilized, can be calculated as follows:

Vl

ppm

MW

L

SpGr

MV

106

In the above equations: ppm = parts per million, by volume, of perchloroethylene MW = molecular weight of perchloroethylene MV = molar volume (this value if 24.45 L at 25oC and 760mm Hg, but should be corrected if temperature or pressure vary significantly from these values. Vl = volume of liquid perchloroethylene, in mL L = volume of air in bag, in liters SpGr = specific gravity of perchloroethylene, in g/mL 3 Concentrations in ppm can be converted to mg/m as follows:

mg/m3 =

(ppm) (M W) ______________ = (M V)

(ppm) (166) ____________ (24.45)

=

(ppm) x 6.8

Perchloroethylene RT = 167 sec

FIGURE 1 - Typical chromatogram obtained from the analysis of exhaled breath containing approximately 1.3 ppm perchloroethylene. Peak number 3 shows area of 598.1 mVs at a retention time of 167.4 sec. This is compared with a calibration curve in which a 1 ppm perchloroethylene standard produced a mean peak area of 452 mVs at a retention time of 167 sec.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition