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Model 5380 PFPD Operator’s Manual
Rev. 3.1
Maximizing Phosphorus to Carbon Selectivity
To maximize the PFPD’s selectivity for phosphorus over carbon, the following
steps are necessary:
1. Use an optical filter in the PMT assembly that is optimal for detecting phos-
phorus (see Appendix A).
2. Optimize for phosphorus response as described in “Maximizing Phosphorus
Response.”
3. To increase selectivity between the phosphorus and hydrocarbon emissions,
increase the Gate A start time relative to that shown in Figure 5.4 (i.e.,
increase the Gate A Start Time in the Gate Parameters screen to 4–6 ms or
more) to minimize hydrocarbon and phosphorus response overlap.
Maximizing Sulfur to Carbon Selectivity
To maximize the PFPD’s selectivity for sulfur over carbon, the following steps are
necessary:
1. Ensure that the carbon concentration is not so high that it quenches the sulfur
response. Quenching can be observed by a “collapsing” (i.e., reduction in
emission lifetime) of the sulfur emission during coelution with hydrocarbon
concentrations. If the carbon flow rate exceeds 10–100 ng/sec, reduce it by
splitting the sample.
2. Use an optical filter in the PMT assembly that is optimal for detecting sulfur
(see Appendix A).
3. Optimize the PFPD for sulfur response as described in “Maximizing Sulfur
Response.”
4. Increase the gate delay relative to that shown in Figure 5.5 (i.e., increase the
Gate A Start Time in the Gate Parameters screen to 6–8 ms) to minimize
the hydrocarbon and sulfur response overlap. Due to the long time domain of
the sulfur emission, a correctly delayed gate can virtually eliminate carbon
interferences without using dual gate techniques.
Summary of Contents for 5380
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