68 Model 5380 PFPD Operator’s Manual
Rev. 3.1
Minimizing Quenching
1. Inject the smallest possible sample size that provides sufficient sensitivity.
2. Use the 3-mm combustor.
3. Increase Air 1 flow rate until the sulfur response is reduced by a factor of
about 2 (or at least 1.2).
4. Set the Gate Start at 5 ms and the Gate Stop at 12–15 ms. Quenching mostly
affects the longer delayed emission.
5. Use a semipolar column that separates critical pairs such as thiophene and
benzene or methylthiophene and toluene. This column needs to have a thick
film to reduce column saturation and good separation. For gasoline analysis, a
column such as Rtx-35 with 1-µ film and 0.25-mm I.D. (or equivalent) is
recommended. For gas analysis such as COS in propylene, use the silica
PLOT column from Chrompack with 4-µ PLOT film and 0.32-mm I.D.
Detecting Phosphorus and Sulfur
Simultaneously
1. Install optical filter UV34 (Part #310623). (See “Replacing the Optical
Components” in Chapter 6.)
2. Decide which element sensitivity is more important to determine the combus-
tor and optimal gas flow rate. (For information on choosing the appropriate
combustor, contact the Customer Service Department at 1-800-336-1911 or
1-409-690-1711.)
3. Install the appropriate combustor (see “Installing the Combustor and Reas-
sembling the PFPD” in Chapter 3) and set the optimal gas flow rate (see
“Optimizing the Combustor Flow (Sulfur)” in this chapter) for the select
element sensitivity. Note that the 2-mm combustor reduces or increases the
detectivity of the element by less than a factor of two compared with the 3-
mm combustor.
4. Using the GC’s electronic keyboard, set the PFPD temperature to 300°C. The
higher temperature will favor phosphorus, but it is needed for equimolar
phosphorus response. A lower temperature will increase the sulfur detectivity.
5. From WinPulse, set the gate start to 5 ms and the gate stop to 24.9 ms.
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