Fundamentals of Sample Preparation for Environmental Analysis - Fundamentals of Environmental Sampling and Analysis - page 179

Table 7.1 Comparison of sample preparation techniques for SVOCs and VOCs

Extraction Extraction Solvent EPA

method Application Cost time usage Simplicity method

Purge & trap VOCs (L/S) High 30 min None No 5030, 5035

Headspace VOCs (L/S) Low 30 min None Yes 3810, 5021

LLE SVOCs, NVOCs (L) Low 1 h 500 mL Yes 3510/3520

SPE SVOCs, NVOCs (L) Medium 30 min 100 mL Yes 3535

SPME VOCs, SVOCs, Low 30 min None Yes None

NVOCs (L)

Soxhlet/ SVOCs, NVOCs (S) Low 4-24 h 250/50 mL Yes 3540/3541

Soxtec
Ultrasonic SVOCs, NVOCs (S) Medium 10 min 200 mL Yes 3550

SFE SVOCs, NVOCs (S/L) High 30 min 20 mL No 3560/3561

PFE (ASE) SVOCs, NVOCs (S) High 15 min 25 mL No 3545

LLE: liquid-liquid extraction; SPE: solid phase extraction; SPME: solid phase microextraction;
SFE: supercritical fluid extraction; PFE: pressured fluid extraction; ASE: accelerated solvent extraction.
VOCs: volatile organic compounds; SVOCs: semivolatile organic compounds; NVOCs: nonvolatile organic
compounds. L: liquid samples; S: solid samples.

but many of them come with a higher price tag. In laboratories processing a
large number of samples, these automated methods may be preferred because of
areductioninlabors.

7.4 POST-EXTRACTION CLEAN-UP OF ORGANIC
COMPOUNDS

''Cleanup'' is to remove interfering chemicals from the sample while keeping
target analyte(s) in the sample matrices prior to instrumental analysis. Simply
put, cleanup is to remove as much garbage as possible from complex sample
matrices. Cleanup is critical to the analysis of trace analyte of interest (ppm - ppt
or lower), because the analyte is often masked by high background concentration
of various types of organics and the removal is essential for further analyses by
instruments. Cleanup will also avoid the rapid deterioration of expensive
capillary GC columns and instrument downtime caused by cleaning and
rebuilding of detectors and ion sources. Many of the cleanup procedures are
performed after extraction.

7.4.1 Theories and Operation Principles of Various
Clean-up Methods

There are several cleanup techniques available for environmental analysis. They can
be used individually or in various combinations, depending on the extent and nature
of the co-extractive chemicals.