Headquarters U.S. Air Force I n t e g r i t y - S e r v i c e - E x c e l l e n c e Direct Sampling Ion TrapMass Spectrometry Rob R. Smith Oak Ridge National Laboratory March 9, 2002 1
Description of the Technology Available Modules MS Interface Applications Example Results Conclusions Outline
Description of the Technology • Direct Sampling Ion Trap Mass Spectrometry (DSITMS) is the direct introduction of samples into an ion trap mass spectrometer. Ion trap mass spectrometers provide both high sensitivity and selectivity, the capability of operating in several detection modes (EI, CI, MSn), and simple, sturdy construction which is particularly amenable for field use. A variety of sampling modules have been developed for field use with DSITMS. DSITMS has been utilized for ten years in the field by ORNL.
Purge Module • The soil/water purge module is capable of processing up to 15 (40 mL) sample/hr. in the field or laboratory with Limits-of-Detection (LODs) in the high ppt to low ppb range.
Air Module • The air module is used for analysis of analytes in gases such as ambient air, stack gases, and soil gases. LODs are typically in the low to mid ppbv range for most VOCs.
Thermal Desorption Module • The thermal desorption module is used for the analysis of gas samples concentrated on sorbent cartridges or desorption of analytes of interest from soils or other solids. Analysis time is typically 3 to 5 minutes, with LODs in the low ng to high pg range.
In Situ Water Monitor • The in situ water monitor is composed of an outer tube which acts as a reservoir for gases, an inner tube which forms a pump and which contains the gas/water interface, and a small gas conducting tube which supplies a gas, usually helium, to the inner tube. The ISWM is connected to the mass spectrometer via a sampling umbilical.
Hydrosparge • Cone penetrometry is a technique involving deployment of sampling probes into the ground by a hydraulic ram mounted in a specially designed vehicle. The HydropunchTM is one such probe which permits sampling of groundwater at specified intervals. DSITMS-ISWM has been used extensively with this technology.
Membrane Interface Probe • Another probe used extensively with cone penetrometry is the membrane interface probe (MIP). Contaminants diffuse across a heated membrane interface and are swept up in a carrier gas stream which carries them to the surface and the DSITMS for analysis.
Old Style Interface • The old DSITMS interface design held about 10 inches of 0.1 mm I.D. fused silica capillary which functioned only as a critical orifice.
New Style Interface • This new DSITMS interface design is capable of holding more than 10 m of fused silica capillary on a spool which permits it to be used as a gc (with proper modifications) as well as a critical orifice.
DSITMS Compatible Samples Water: Discrete samples (40 ml vials) Bulk samples (groundwater wells) Process streams Soil: Discrete samples (40 ml vials) Solvent extracts Soil gas Air: Real-time direct monitoring Gas bags / canisters Sorbent tubes
Typical DSITMS LOD’s • VOCs in water: 0.1 - 1 ppb • VOCs in soil: 5 - 50 ug/kg • VOCs in air: 10 - 100 ppbv • Sorbent tubes: 100 - 1,000 pg (single analyte) • VOCs by MIP: 0.1 - 0.5 ppm
Field Applications • Rapid screening for VOCs (water, soil, soil gas) • Quantification of target VOCs (water, soil, air) • Petroleum fuels (BTEX , TPH and fuel type) • Targeted SVOCs (PCBs, pesticides) • Optimization of remediation technologies • Real-time air monitoring • Process monitoring • Emissions monitoring
Laboratory Applications • Rapid screening for method 8260 VOCs • Quantification of target VOCs (proposed meth 8265) • Petroleum fuels (BTEX , TPH and fuel type) • Outgassing of industrial products • Targeted SVOCs (PCBs, pesticides, CW agents)
Proposed EPA Method 8265 A method for use of DSITMS in analysis of gas, soil, and water samples has been developed and submitted to EPA and is being reviewed for inclusion into SW-846. The provisional method number is 8265. A number of studies have been conducted comparing samples analyzed by DSITMS with those analyzed by standard laboratory methods such as Method 8260 (gc/ms). DSITMS has compared quite well, generally with more accurate results for P/E samples than those from the standard method. The following results are a sample of some of the comparison studies done in both the laboratory and the field.
Applicable to Air, Water, and Soil Useful for qualitative or quantitative analyses Very fast results Cost efficient Regulatory acceptance in progress DSITMS technology is being commercialized Conclusions Oak Ridge National Laboratory