5 How to Introduce a Standard A separate run of the same compoundSpike all samples with a reference material that does not interfereAVOID USING A REFERENCE GAS PULSE AS YOUR STANDARD!!!!!!!
6 Identical TreatmentThe reference and sample should be measured in the same wayThe reference and sample should be the same compound (or class of compound)3) The reference and sample should be as similar in composition and concentration as possible
38 Electronic Flow Controller Most new GC’s have themGreat for split/splitless injectorsDifficult for 6-port valvesBe mindful of the two types:Mass flow controllerElectronic pressure controller (calculates flow)
39 Mechanical Pressure Regulator Common on older GC’sSet the head pressure on the columnFlow varies depending on the column tempOperates by adjusting the tension on a diaphragm
40 Mechanical Flow Controller Common on older GC’sMaintain a constant flowVary the head pressure as column temp changesNeedle valveCombo Valve from Valco
41 Mechanical Flow Controller samplecolumnwasteHePressure gauge shows column head pressureRises as you go through Temp ramp (constant flow)Pressure drops to zero for a leakPressure increases to inlet pressure for a plug
42 Handling Gas SamplesCanisters or bombsTeflon baggiesWheaton bottles
51 Chromatographic Issues Air PeakMasses 48, 49, 50
52 Part 3: Combustion and Pyrolysis Converting your peaks to H2 and CO2
53 Combustion A good resource: Performance and Optimization of a Combustion Interface for Isotope Ratio Monitoring Gas Chromatography/Mass SpectrometryDawn A. Merritt, Katherine H. Freeman, Margaret P. Ricci, Stephen A. Studley, J. M. HayesAnal. Chem., 1995, 67(14), pp 2461–2473
54 Combustion Ceramic Tube 0.5 mm ID Alumina (inert, gas impermeable) Metal wiresmm diameter- Copper or nickel- Platinum3) Oxygen
55 Combustion Input capillary should be inserted 1cm Capillary Tubing from GCZV FittingZV FittingAlumina TubeWireInput capillary should be inserted 1cmWires need to be centered in the hot zoneApprox 15cm in a 30cm tube
57 What Metal? Copper/Platinum Trouble with methane - 3 Cu and 1 Pt wire Nickel/Platinum- 3 Ni and 1 Pt wire°C3) Copper/Nickel/Platinum°CTrouble with methaneHolds on to oxygen longerLonger lifeHigher TemperatureHybrid
59 Oxidation Periodic Reoxidation Can run out of O2 - 100% O2 - Backflush 2) Oxygen Bleed- Trickle in 1% O2 in He- Always OnCan run out of O2Can’t use for a whileConstantly regeneratingNever run outDifficult to balance
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