FRTR Field Sampling and Analysis Technologies Reference Guide

6 SAMPLE ANALYSIS TOOLS for VOCs, SVOCS, and PESTICIDES

6.2 EX-SITU ANALYSIS

6.2.7 Mass Spectrometry

Use:

Determines the masses of atoms or molecules found in a solid, liquid, or gas. Often used in combination with gas chromatography (see 6.2.8)

See 9.1.2 for use with explosives.

Description:

A mass spectrometer produces charged particles (ions) from the chemical substances that are to be analyzed and then uses electric and magnetic fields to measure the mass (weight) of the charged particles. Distinctive mass/charge ratios allow for identification of compounds, while the magnitude of ion currents at various mass settings is related to concentration. Major components of the mass spectrometer include (1) the inlet system, (2) the ion source, (3) the electrostatic accelerating system, and (4) the detector and readout system that gives a mass spectrum recording the numbers of different ions.

When a sample is introduced into the mass spectrometer, electron bombardment causes the parent molecule to lose an electron and form a positive ion. Some of the parent ions also are fragmented into characteristic daughter ions. All of the ions are accelerated, separated, and focused on an ion detector by means of either a magnetic field or a quadrupole mass analyzer. Using microgram quantities of pure materials, the mass spectrometer yields information about the molecular weight and presence of other atoms within the molecule, such as nitrogen, oxygen, and halogens. The most favorable routes for decomposition provide the most intense peaks in the mass spectrum. High-resolution spectra contain so much data that computers are used for molecular structure analysis and acquisition of data in a form easily assimilated by the operator.

Analytes:

1. Non-Halogenated VOCs	2. Non-Halogenated SVOCs	3. Halogenated VOCs
4. Halogenated SVOCs	5. PAHs	6. Pesticides/Herbicides

Media:

Soil/Sediment	Water	Gas/Air
Requires extraction to liquid or gas phase	Requires extraction to liquid or gas phase	BETTER

Selectivity:	Technique measures the specific contaminant directly. Mass spectrometry has very good specificity in a noncomplex matrix; however, it has poor resolution in complex mixtures (can be overcome by using GC/MS).
Susceptibility to Interference:	Medium.
Detection Limits :	10-100 ppm (soil); 0.5-10 ppm (water).
Turnaround Time per Sample:	Hours.

Applicable To:

Screen/Identify	Characterize Concentration/Extent	Cleanup Performance	Long-Term Monitoring
ADEQUATE	BETTER	BETTER	ADEQUATE

Quantitative Data Capability:	Produces semi-quantitative data.
Technology Status:	Commercially available technology with moderate field experience.
Certification/Verification:	Technology has not participated in CalEPA certification and/or CSCT verification program.
Relative Cost per Analysis:	Most expensive.

Limitations:

Bulky requiring high vacuum pumps and a large amount of power.
Due to the complexity of the instrumentation, setup time can be long.
Calibration procedures are more time consuming than for GC.
Sensitivity and resolution for field instruments is not as good as that achieved by laboratory instruments.
May not detect certain semi-volatile compounds such as benzopyrenes.
Poor resolution in complex sample mixture.
Maximum analyte molecular weight of 400 due to requirement for volatilizing sample.

ASTM Standards:

D 5790 - 95

Measurement of Purgeable Organic Compounds in Water by Capillary Column GC/MS.

(Multiple ASTM Standards exist for specific contaminants in a variety of matrices).

Sample Access/Collection Matrix

Sample Analysis Matrix

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