Determination of organic contaminants by the Grob closed‐loop‐stripping technique

A modified Grob closed-loop-stripping device is currently being used to concentrate organic contaminants from drinking water. The identification and quantification of organic contaminants at the nanogran per litre (part-per-trillion) level are accomplished by a computerized glass capillary gas chromatography-mass spectrometry system. Applications of closed-loop-stripping analysis (CLSA) for monitoring water by water utilities, for studying the use and effects of alternative disinfectants in drinking water, and for providing data on the removal of organic contaminants from water by granular activated carbon (GAC) treatment are discussed. An attempt to validate the method using statistical computations is also included. The exposure evaluation branch of the USEPA’s health effects research laboratory (HERL) in Cincinnati, Ohio, is responsible for validating sensitive methods for measuring organic contaminants in drinking water, principally in support of epidemiological studies. Its method of choice at this time is Grob closed-loop-stripping analysis (CLSA). In 1973 in Zurich, Switzerland, Grab’ reported on CLSA for the measurement of semivolatile, intermediate molecular weight organics in drinking water at the rig/L (ppt) level. Later, in 1974, Bellar’ I reported his purge-and-trap method (Bellar VOA) for the analysis of purgeable volatile organics at the pg/L (ppb) level. Water analysis laboratories in the United States quickly adopted the Bellar VOA method”-6 using packed gas chromatograph (GC) columns, whereas Western European laboratories adopted the Grob CLSA method, which uses wallcoated-open-tubular (WCOT) glass capillary gas chromatography (GC)‘. The primary reason for the slow adoption of Grob CLSA in this country was the slow acceptance of state-of-the-art WCOT glass capillary column technology and hardware by US manufacturers. That one US company held the exclusive patent rights to manufacture WCOT capillary columns did not help in this regard, and US laboratories now lag behind their Western European counterparts in the use of (GC) for the separation of environmental pollutants. It is unfortunate that this technological gap in gas chromatography has delayed validation of Grob CLSA by US laboratories. CLSA has great potential as a monitoring tool for water utilities. Current studies on the use and effects of alternative disinfectants in drinking water and research on the removal of organic contaminants from water by granular activated carbon (GAC) need a sensitive and