The ability to analyze ultratrace levels of organic pollutants in water has been limited, in part, by the concentration technique. Closed-loop stripping analysis (CLSA) (6040 B) allows organic compounds of intermediate volatility and molecular weight (ranging from heavier volatiles to lighter polynuclear aromatic hydrocarbons) to be extracted from water and concentrated, permitting quantitative and semiquantitative analysis (depending on compound) at nanogram-per-liter levels. These extracts can be analyzed using a gas chromatograph (GC) connected to one of several detectors. This method describes a CLSA technique coupled with gas chromatographic/mass spectrometric (GC/MS) analysis for trace organic compounds, applicable for testing both treated and natural waters.
The purge and trap technique (6040 C), applicable to both water and wastewater, can concentrate volatile organic compounds by bubbling an inert gas through a sample, collecting it in a sorbent trap, and then desorbing the compound for analysis. The extract may be analyzed by GC or GC/MS methods.
Solid-phase microextraction (SPME) techniques for taste- and odor-causing compounds (6040 D and E) are more rapid than 6040 B and use much smaller samples, while achieving similar sensitivity. SPME techniques can be performed using two MS modes. SPME coupled with GC/MS using electron impact in the selected ion monitoring mode is presented in 6040 D. SPME coupled with GC/MS in the chemical ionization (CI) mode with methanol as the reagent gas is presented in 6040 E.