6. AOACSPIFANMethods-2018Awards

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qualitative cis/trans C18:1 FAME isomers standard mixture solution, D ( k ). The resolution is sufficient when resolution (R) criteria is equivalent or higher than 1.00 (Figure 2012.13C ). The following two examples report applicable conditions for a correct separation of cis and trans with different GC injectors. (b)  Example 1. —Split injection mode. ( 1 )  Column. —100 m length × 0.25 mm id, 0.2 μm film thickness, fused silica capillary column. ( 2 )  Stationary phase .—Cyanopropyl-polysiloxane or equivalent polarity. ( 3 )  Carrier gas type. —Helium. ( 4 )  Column head carrier gas pressure. —225 KPa (175–225 KPa). ( 5 )  Split flow .—25.5 mL/min. ( 6 )  Split ratio. —10:1. ( 9 )  Oven temperature program. —Initial temperature of 60°C, maintained for 5 min, raised at a rate of 15°C/min up to 165°C, maintained at this temperature for 1 min, and then raised at a rate of 2°C/min up to 225°C for 20 min. ( 10 )  Amount of sample injected. —1.0 μL. ( 7 )  Injector temperature. —250°C. ( 8 )  Detector temperature. —275°C.

An example of the GC profile obtained with these conditions is reported in Figure 2012.13A . (c)  Example 2.— On-column injection mode. ( 1 )  Column .—100 m length × 0.25 mm id, 0.2 μm film thickness, fused silica capillary column. ( 2 )  Stationary phase .—Cyanopropyl-polysiloxane or equivalent polarity. ( 3 )  Carrier gas type. —Hydrogen. ( 4 )  Column head carrier gas pressure. —210 KPa (175–225 KPa). ( 7 )  Oven temperature program .—Initial temperature of 60°C, maintained for 5 min, raised at a rate of 15°C/min up to 165°C, maintained at this temperature for 1 min, and then raised at a rate of 2°C/min up to 225°C for 17 min. ( 8 )  Amount of sample injected. —1.0 μL. An example of the GC profile obtained with these conditions is reported in Figure 2012.13B . (d)  Resolution between C18:1 trans and cis . —Inject into the gas chromatograph 1.0 μL calibrating solution, D ( k ). Determine peak width at half height and distance between the left of the ( 5 )  Injector temperature. —Cold. ( 6 )  Detector temperature. —275°C.

Figure 2012.13C. Example of a GC chromatogram (i.e., with insufficient and sufficient resolution for C18:1 trans ).