•
•
DETector Engineering
&
Technology, inc.
486
NorthWiget Lane
DET REPORT
Walnut Creek,CA
94598·2408
USA
Phone:
925-937-4203;
FAX:
925-937-7581
No.63 JUNE
2011
e-mail:
1.) ELIMINATENPDPHOSPHORUSPEAK TAILINGWITHA BLACK
CERAMIC IONSOURCE (BEAD) FROMDET.
2.) DIFFERENCESBETWEEN CERAMICANDGLASS NPD IONSOURCES.
3.) SCIENCEOFTHE NPD.
4.) LIFETIMECONSIDERATIONS FORNPD IONSOURCES.
1.) ELIMINATE NPDPHOSPHORUSPEAK TAILINGWITHA BLACKCERAMIC
IONSOURCE (BEAD) FROMDET.
Years ago, Phosphorus peak tailing was awell know Figure 2 demonstrates that peak tailing results in a
characteristic of NP detectors. In 1997, DET very long term recovery of the detector baseline to a
announced the development of a durable NPD ion
source with a Black Ceramic coating specifically
formulated to eliminate the P tailing, while still
maintaining excellent P detectivity (e.g., 70 fgP/sec).
That Black Ceramic ion source is currently available
direct from DET, or as an NPD option from Agilent,
ThermoScientific, SRI Instruments, and several other
GC manufacturers.
In recent years there has been increasing use of a so
called "Bios" glass NPD bead , and that has re
introduced the problem of tailing P peaks. Figure 1
demonstrates how detection of trace level peaks U1,
U2, and U3 is obscured when they elute shortly after
large tailing P peaks .
P tailing - resolving
NP
peaks U1, U2, U3
TID-2
ceramic
N
P
Bios glass
N
c
Figure 1.NP=2ngMethyl Parathion, P=4ng Malathion.
stable level, and that is an important downtime
consideration when waiting for baseline stabilization
before injecting the next sample.
DET TID-2 Black Ceramic Ion Source
background
at32 pAlmV
chemistry
Ignite
at 2.88A
1,..------..
N.L
/
solvent
sample
responSl
background
at '024 pAlmV
at 32pAlmV
P
NP
1
Agllent " BLOS " Glass Bead
32 pAlmV
'024 pAlmV
32 pPJmV
p
NP
N
)
solvent
N - Azobenzene. NP • Methyl Parathion, P - Malathion
Figure
2.
Expanded display sensitivity before and after
elution ofsamplecomponents.Agilent6890NPDhardware
withDETCurrentSupplyfor ionsourcepower. Ionsource
heating currentinitiallyincreased tomagnitude required for
NP chemistry ignition. 3ng Azobenzene, 3ng Methyl
Parathion, and6ngMalathion sample injected. SensitiVity
changed aftersolventelutiontoshowpeak responses.
1
Website :
E-nmail :
TelNo : 03 9762 2034 . . . inAUSTRALIA
