Coupled solid phase extraction-supercritical fluid extraction on-line gas chromatography of explosives from water

A method has been developed for the quantitative extraction of nitrotoluenes (2,6-dinitrotoluene, 2,4-dinitrotoluene, and trinitrotoluene) from water. Three types of solid sorbents were investigated: two 47 mm Empore disks™ - octadecylsilane (C18) and styrene-divinylbenzene (SDVB); and one Bakerbond spe*™ Phenyl stationary phase. The phenyl sorbent yielded the highest recoveries. The average SPE recoveries for spike standards ranged from 80 to 95 percent for Millipore water and 55 to 95 percent from well and surface water in the low ppb and ppt levels. After the nitrotoluenes were trapped on the solid sorbents they were quantitatively eluted by first doping the bed with toluene and then extracting with supercritical carbon dioxide. Doping with toluene was found to increase the rate of extraction. The extracts were analyzed off-line via GC-ECD using an internal standard. Extraction losses are due to analyte break through, and not from poor SFE recoveries. This demonstrates that supercritical fluid extraction is a suitable elution technique for analytes trapped on solid phase extraction (SPE) cartridges. A method has also been developed and evaluated for the direct on-line coupling of SPE to GC. SPE-SFE-GC-ECD analysis eliminates off-line collection and subsequent handling of hazardous materials. SFE is an ideal means of directly coupling SPE to GC, since carbon dioxide is a gas at ambient temperatures and pressures and thus easily removed. One potential problem for SPE-SFE on-line GC is the presence of residual water trapped on the active sites of the bonded silica sorbent. The presence of water can interfere with the cryogenic trapping of the analytes on the capillary GC column. The water becomes ice at cryogenic temperatures and in large quantities blocks the GC column. This problem has been avoided by using a split injection interface previously described by Hawthorne. The quantitative reproducibility of this interface will be investigated for nanogram quantities of nitroaromatics.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1992

Author dc:creator

• Slack, Gregory C.

Chair dc:contributor.committeechair

• McNair, Harold M.

Committee members dc:contributor.committeemember

• Taylor, Larry T.
• Glanville, James O.
• Long, Gary L.
• Merola, Joseph S.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-05042006-164508

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/37685