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4/5/2005 PID Analyzers, LLC 1
Determination of Oxygenates & BTX in
Beverage Grade CO2Dr. Jack Driscoll & Jennifer Driscoll
PID Analyzers, LLCcopyright 2004-2005 PID Analyzers
Paper # 130Paper # 130--1 Pittsburgh Conference,1 Pittsburgh Conference,
Orlando, FL; Feb. 28, 2005 (8:30 AM) ;Orlando, FL; Feb. 28, 2005 (8:30 AM) ; RmRm S220CS220C
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Abstract Abstract Last year, we (1) presented a method for the analysis of BTX at low ppb levels in beveragegrade CO2. In this paper, we describe a method for volatile oxgenates and demonstrate that itcan be combined with the previous BTX (1) method to perform multifunctional analyteanalyses. The photoionization detector (PID) has been improved to provide the sensitivity andppb detection limits required by the industry. The 301-B now has multiple valve switching
capability and multiple autozeros to smooth the baseline when columns are switched in or out.With these changes and system optimizations, we have achieved some complex separations atppb levels with a minimum of operator time or training required.
The following method on the 301-B was developed for the analysis of ppb levels of oxygenates(acetaldehyde, methanol & dimethyl ether) in beverage grade carbon dioxide. The detectionlimits required were 100 ppb for acetaldehyde and dimethyl ether.
The analysis can be automated via a PLC that controls the 301-B (start, calibrate, print report).An optional operating system is Windows XP. If the 301 GC is part of the plant network, thesystem can be operated from any PC on the network. Of course the system has passwords.The detection limit for this analysis was <100 ppb (acetaldehyde), & <50 ppb (dimethylether) for a direct injection with no concentration of the sample. The analysis time for thismulticomponent analysis was < 10 minutes.
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Driscoll, JN & J. Driscoll, “Detection of ppb Levels of BTX in Beverage Grade CO2”, Paper # 1700-1100P, Pitt. Conf. on Anal. Chem., Chicago, IL, March 2004
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Presentation Objectives Presentation Objectives
A new Method has been developed for use withthe Model 301-B to analyze both oxygenates and
BTX at the same time. This involved the following:
•A second column (PLOT) was added toseparate acetaldehyde and dimethyl
ether from the CO2 and the BTX
A 4 port switching valve was used for columnselection
In addition, a number of improvements have beenmade in the original 301-B instrumentation
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What are the improvements? What are the improvements?
USB based ADC System
Touch screen Color VGA display Windows XP Operating System
(embedded) with PW Chromatography
Software Detectors- PID improved New outputs- Modbus
Easier to expand features through USB
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Floppy, USB Disk…NoUSB Peripherals
YesNoNetworkCapability
WindowsSpecialOperating Sys
YesNoWindows XP(Embedded)
YesNoPlug & Play
40 Gbyte HDvarysvarysMemory
500 MHz, 100 MHz BusvarysvarysSpeed
301-B PC BasedOther GCs uP
Comparison of uP and PC Based Process GCs
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Model 301 Model 301-- B B
mousemouse
USB PortUSB Port
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Rear View of Model 301Rear View of Model 301--BB
RelaysRelays
Fluidics I/OFluidics I/O
PCPC
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GC Signal SchematicGC Signal Schematic
PCPCRS232RS232
KeyboardKeyboard
Digital I/ODigital I/O-- valvesvalvesDigital I/O AlarmsDigital I/O Alarms
DiagnosticsDiagnostics
DAC to 4DAC to 4--2020 mAmA
ADC 16 bitADC 16 bit
DisplayDisplay
Time clock, data calc & storage on hard driveTime clock, data calc & storage on hard drive
DetectorDetector
AMPAMP
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301 301 - - B GC Fluidics B GC Fluidics
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Photoionization Detector Photoionization Detector
R + hν = R + + e-
where
R= molecule hν = a photon with an
energy > IP of R
R+
= positive ion e- = electron
Process Process
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PID Characteristics PID Characteristics
Linear dynamic range > 5 x107
Detection limit <0.5 ppb benzene Non destructive; other detectors can be run in-series
Sensitivity increases as the carbon number increases(carbon counter)
For 10.2 eV lamp, responds to carbon aliphaticcompounds > C4, all olefins and all aromatics
The PID also responds to inorganic compounds such asH2S, NH3, Br2, I2, PH3, AsH3, e.g. any compound with anionization potential of < 10.6 eV
The PID is more sensitive than the FID; >200 x moresensitive for aromatics, 80 times for olefins, & 30 times for
alkanes > C6 Non destructive detector; other detectors can be run
downstream Concentration sensitive detector
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301 301 - - B Process GC B Process GC
Analytical Column Mode for Specific Detection
Six detectors to choose from: SpecificSpecific to UniversalUniversal
Minimum Maintainance
Data Processing of Concentrations
X (Div. 1) or Z purge (Div. 2)
Outdoor Locations-
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Optimization Parameters for Process Optimization Parameters for Process
GC GC ’ ’ s s
Pre columnPre column- to remove heavies, polar or non
polar species, protect analytical column Inject timeInject time- can be varied to remove heavier
species
DetectorDetector- Selectivity- HNU has 6 detectors tochoose from;PID lamp energy can be varied
Packed and capillary columns can be mixed
BackflushingBackflushing to remove heavies; foreflushingforeflushingto remove light compounds, heart cuttingheart cutting toremove a compound during the run
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4/5/2005 PID Analyzers, LLC 14MethodMethod
OnOn--screen keyboardscreen keyboard
PID 10.6PID 10.6 eVeV
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4/5/2005 PID Analyzers, LLC 15CalibrationCalibration
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4/5/2005 PID Analyzers, LLC 16Detector ParametersDetector Parameters
PID 10.6PID 10.6 eVeV-- 3 ppb3 ppb
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4/5/2005 PID Analyzers, LLC 175 ppb BTX5 ppb BTX
PID 10.2PID 10.2 eVeV
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Low Level Linearity of Benzene & Ethyl Benzene
y = 972.99x - 16.272
R2
= 0.9999 y = 389.31x - 8.112
R2
= 0.9999
0
5000
10000
15000
20000
25000
0 5 10 15 20 25ppb Benzene/Ethyl Benzene
P e a k C o u n t s
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Cal Curve for Oxygenates in CO2
DME (upper)
y = 0.1788x + 25.546
R2
= 0.9973
y = 0.4923x + 73.813
R2
= 0.9955
0
500
1000
1500
2000
2500
3000
0 1000 2000 3000 4000 5000 6000
ppm Acetaldehyde/DME
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3030--50 ppb50 ppbdimethyldimethyl etherether
5050--100 ppb100 ppbacetaldehydeacetaldehyde
< 10 ppb< 10 ppbalkanesalkanes
<5 ppb<5 ppbalkenesalkenes
< 0.5 ppb< 0.5 ppbaromaticsaromatics
Detection LimitsDetection Limits
5 x 10exp75 x 10exp7Dynamic RangeDynamic Range
YYAromaticsAromatics
YYAlkenesAlkenes
YYC5+C5+ alkanesalkanes
NNC1C1--C4C4 alkanesalkanes
SpeciesSpecies
PIDPID
PID Characteristics
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4/5/2005 PID Analyzers, LLC 22
Summary Summary The instrument is PC based with considerable
expansion capability including LAN, RF modem,USB and additional sensors
The system is fully automatic and is controlled by aPLC
The reproducibility [coefficient of variation= 100(std.dev./mean)] at 50 ppm benzene is 1.5%; and at 5ppb- 5%
The detection limit for benzene with nopreconcentration is < 0.5 ppb; acetaldehyde <50
ppb & DME < 20 ppb BTX and oxygenates can be analyzed & detected
wth the same Analyzer