Appendix A - Volatile Organics Equipment
1990-1993 The analytical system consists of a Perkin Elmer ATD-50 sample desorber interfaced to a Hewlett Packard 5890 GC with 5970B MSD and PASCAL Chemstation. The GC column is an SGE 60M BP-1 .25mm ID with .5 um coating.
1994-1998 The analytical system was upgraded to a Perkin Elmer ATD-400 desorber. HP software was upgraded to MS-DOS software versions but still operating the 5970B MSD.
The following pages are drawings of the VOTS field sampler and the Perkin Elmer sample tube.
The Perkin Elmer sample tubes are custom packed as shown on page A-3. The O-ring sealed storage caps as shipped by the manufacturer are replaced with Swagelock 1/4" brass nuts and caps using teflon ferrules. This change-over significantly reduced the average amount of contaminants in the field blanks. The standard storage cap is not an effective seal for routine shipping and handling.
The problem of passive sampling after the sample set-up and before pickup by the field staff is addressed by a simple modification of the analytical end cap used in the ATD-50 system.
The spring that seals the stainless steel ball against the O-ring is removed. This modified cap is attached to the sampling tube while in the sampler. When the sample is being taken, the power of the vacuum pump pulls the sample past the ball. When the pump is off, the ball is resting on the O-ring, effectively sealing the end of the tube.
This procedure was tested and the tubes proved to be substantially unchanged for up to 100 hours of passive exposure.
1999-2000 Entech model 7000 autosampler and cryotrap injector with Finnigan Magnum Ion Trap GC/MS
2000 Entech model 7000 with Varian Saturn io trap GC/MS
Ion Trap GC/MS systems increased the sensitivity for the target compounds about 10 fold. The system is also run in full scan mode so no ambient data is lost as in a quadrapole MS system in selective ion mode. This increased sensitivity allowed us to reduce the sample size and thus reduce the unfavorable effects of high humidity in the ambient samples.
