Semivolatiles Analysis Using Split Injection
Semivolatile calibrations on this column dimension often range from 1.0 to over 100 ng/µL; however, a 0.25 mm ID column usually experiences peak overload as the mass on column approaches 10 ng. As shown in Figure 1, isobars that elute close together-such as benzo[b]fluoranthene and benzo[k]fluoranthene-quickly become unquantifiable as mass on column increases. Under split conditions, the resolution requirement (50% valley) is met for all nine calibration standards, and the peak apices shift less than 0.04 min, indicating only minor peak overload. Conversely, under splitless conditions, the three highest concentration calibration standards fail the resolution criterion. The peak fronting and resulting overlap from column overload make it impossible to generate a linear calibration including these points. Additionally, the peak apex of benzo[b]fluoranthene shifts more than 0.2 min, which could result in an erroneous compound identification.