Fast GC Using Minibore Fused Silica Capillary Columns Introduction ...

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Split Injection• Inlet Liner• TemperatureIn a split injection, the choice of inlet liner and initial temperature will affect peak shape, response,and resolution the most.Inlet Liner Volume Effect4mm ID Liner, 90°C Initial TemperatureFragrance Analysis on Rtx-Wax 10m x .10mm IDx .20um dfA typical fragrance analysis on a conventionalcolumn (0.32mm ID) under optimal conditions (4mmID inlet liner and 75°C initial temperature) exhibitsan analysis time of more than 70 minutes and theseparation of vanillin and musk xylol is not achieved.When only changing to a 0.10mm ID column, the analysis time was reduced to 10 minutes.However, poor peak shape and poor recovery of the early eluting peaks also resulted.Optimized Liner Volume1mm ID Liner, 90°C Initial TemperatureFragrance Analysis on Rtx-Wax 10m x .10mm IDx .20umdfBy optimizing the inlet liner (1mm ID), not only didthe analysis time reproduce (10 minutes) but the peakshape of the early eluters also improved. However,recovery of the early eluting peaks is not yet acceptable.Optimized Inlet Liner and Temp.Program1mm ID Liner, 55°C Initial Temp.Fragrance Analysis on Rtx-Wax 10m x .10mm IDx .20um dfWhen the inlet liner (1 mm ID) and the entiretemperature program are optimized (55°C initialtemperature), full recovery and excellent peak shapeof early eluters were attained as well as reduced analysis time (18 minutes) and 80% resolution ofvanillin and musk xylol.Splitless Injection• Inlet Liner• Inlet Pressure• ContaminationIn splitless injection, inlet liner, inlet pressure and sample cleanliness must be considered.
Optimized Liner and PressureProgramRtx-5 10m X0.10mm ID x 0.10µm df1mm ID inlet linerThis chromatogram illustrates a splitless PAHanalysis on a 10m, 0.10mm ID, 0.10µm Rtx®-5using an optimized inlet liner and inlet pressure.Conventional Liner ConstantPressureRtx-5 10m x 0.10mm ID X 0.10µm df2mm ID inlet linerWhen a 2mm ID inlet liner was used, highmolecular weight discrimination occurred.Optimized Liner ConstantPressureRtx-5 10m X0.10mm ID x 0.10µm df1mm ID inlet linerBy changing to a 1mm ID inlet liner, highmolecular weight discrimination was eliminated.However, this change caused peak splitting of theearly eluting compounds. The peak splitting waseliminated completely when pressure programming was applied in place of constant pressure.Sample cleanliness is another important factor to take into consideration when using miniborecolumns. Because the surface area of the 0.10mm ID columns is much lower than a conventionalcolumn, contamination will occur more rapidly when dirty samples are injected. This means that0.25 or 0.32 mm ID columns will be more rugged and require less maintenance for dirty samplesthan minibore columns. Whenever possible, samples containing non-volatile residue should beavoided. If dirty samples are a must, extensive column and injection port maintenance is required.Otherwise, loss of resolution, ghost peaks, and a high background signal will result.Detector• Increased make up gas• Increased S/N with high speed <strong>GC</strong>• <strong>Fast</strong>er scanning ratesDetector ConsiderationsDetector design and flows must be optimized when using minibore columns. Make up gas flowsmay need to be increased to minimize detector dead volume and compensate for the lower columnflow rates.
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Fast GC Using Minibore Fused Silica Capillary Columns Introduction ...

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