pCBSA is determined using LC-MS/MS.  Water samples are injected directly onto the LC-MS/MS.  The instrument is calibrated from 5 to 500 ug/L.  An MDL of 0.6 ug/L was obtained, therefore a reporting limit of 2 ug/L has been adopted.

The chromatography is performed on an anion exchange column with an eluent composed of dilute potassium hydroxide in methanol - water.  The eluent is passed through an anion suppressor (Dionex) prior to the MS.

Ionization is accomplished using an electrospray interface (Varain 1200L LC-MS/MS).  The instrument was operated in the MS/MS mode, detecting negative ions.

For a quotation...

The fragmentations monitored include:

1. in the first quadrupole, only the parent molecular ions are allowed to pass, m/z 191 and 193
2. collisional dissociation is conducted in the second quadrupole pressurized with argon
3. in the third quadrupole, four fragmentations are monitored: m/z 191 => 127 and 193 => 129,  corresponding to loss of SO₂ and m/z 191 => 80 and 193 => 80, corresponding to loss chlorophenyl

For more information click on LC-MS/MS.  Other applications include: Perchlorate and Warfarin.