losses that could be expected under actual use conditions. The data showed a mean recovery of 96-97% of the VCM. Analytical System Because of the inadequacy of the NIOSH-recommended SE-30 gas chromatographic column, we have chosen to use a Durapak (Carbowax 400 on Porasil) packing. The use of Durapak requires a low inlet pressure which results in only minor baseline disruption during sample injection with the gas-injection valve. Sample loops of up to 5.0 ml can be used with out significant loss of resolution. We have found nominal analysis times of between 3 and 5 min to yield more than adequate resolution and results with relative precisions (95% confi dence level, single injection) of ±3% at the 1.0-ppm level and ±11% at the 0.25-ppm level. Since the precision in creases as 1/square root of the number of injections, we routinely inject each sample two or more times. This sys tem can detect less than 0.03-ppm concentrations of VCM in air. Several valving configurations have been developed by other laboratories which incorporate the function of col umn backflush and injection, and cut-
and-backflush and injection in a single automated valve. These valves mini mize the time necessary to clean the GC column of constituents from the air sample having longer retention times than VCM. A cut-and-backflush system presently in use by many labo ratories incorporates a precolumn of Durapak («-octane on Porasil) with porous polymer and a short analytical column of porous polymer. An auto mated 10-port valve is used (12). In conclusion, the industries which use VCM for resin production and ΡVC for fabrication of finished vinyl products were faced with developing, field proving, and installing a com plete VCM personnel monitor system in a short time. Sampling and analysis guidelines supplied by NIOSH were not adequate for the goals of our pro gram, thus necessitating extensive method adaptation and development. The method outlined above represents a viable analytical approach for an in dustrial setting. The long-range goal for determining worker exposure to VCM must be, however, the utilization of continuous monitors. These VCM monitors must have the capability of correlating vari able ambient air VCM concentrations with the results of corresponding per sonnel monitoring samples.
References (1) H. Falk, J. L. Creech, Jr., C. W. Heath, Jr., Μ Ν. Johnson, and M. M. Key, J. Am. Med. Assoc, 230, 59 (1974). (2) "Threshold Limit Values for Chemical Substances in Workroom Air Adopted by ACGIH," American Council of Govern mental Industrial Hygienists, Cincinnati, Ohio, 1973. (3) G. Clack, Job Saf. Health, 3, 4 (1975). (4) Fed. Regist., 39,194 (1974). (5) "NIOSH Manual of Analytical Meth ods," U.S. HEW 75-121, pp 178,1-178, 9, 1974. (6) A. A. Allemang, L. W. Severs, and L. K. Skory, "Monitoring Personnel Exposed to Vinyl Chloride and Other Chlorinated Solvent Vapors in an Industrial Work Environment," American Industrial Hy giene Conference, Minneapolis, Minn., June 4, 1975. (7) R. T. Maykoski and C. Jacks, "Review of Various Air Sampling Methods for Solvent Vapors," NTIS AD-752-525, 1970. (8) F. J. Schuette, Atmos. Environ., 1, 515 (1967). (9) "Methods of Air Sampling and Analy sis," Interscience Committee, American Public Health Assoc, pp 7-8,138, Wash ington, D.C., 1972. (10) F. B. Higgins, Jr., "Sampling for Gas and Vapors," in "Source Sampling of At mospheric Contaminants, Symp. Proc," H. G. McAdie, Ed., Chem. Inst. Canada, Ottawa, Canada, 1971. (11) R. E. Dilgren, Shell Chemical Co., An alytical Method HC-604-74, 1971. (12) F. Zado, Western-Electric Co., Prince ton, N.J., personal communication. This system is not marketed by Western-Elec tric Co.
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