Increasing the instrumental throughput of gas chromatography method using multiple injections in a single experimental run: application in determination of friedelan-3-ol and friedelin in Maytenus ilicifolia.

The aim of this study was to develop a separation method using multiple injections in a single experimental run (MISER) employing gas chromatography with flame ionization detection (GC-FID) for the first time, without instrument modification, to increase the instrumental throughput. The method was applied to the determination of the triterpenes friedelan-3-ol and friedelin in a plant extract obtained from Maytenus ilicifolia leaves. The column used in the chromatography system was a ZB-50 (30 m × 0.25 mm × 0.15 μm) with 50% phenyl-50% methyl-polysiloxane. The samples (1.0 μL) were injected using the split mode (1:90), with the injector at 280 °C and FID detector at 320 °C. The column temperature was programmed to isothermal mode at 300°C. Helium was used as the carrier gas with a constant flow of 1.5 mL min(-1). It was possible to perform three injections in the same run using the MISER method. An increase in the instrumental throughput by a factor of around 2.6 was observed when the use of multiple injections was compared with the single injection method. This method showed good linearity for both analytes with R(2)>0.99 and the values for the limit of detection were 0.24 mg L(-1) and 0.44 mg L(-1), for friedelan-3-ol and friedelin, respectively. Furthermore, the values for the limits of quantification were 0.79 mg L(-1) for friedelan-3-ol and 1.16 mg L(-1) for friedelin. The proposed method has potential for other GC applications, allowing an increase in the instrumental throughput of the methods by applying this separation technique.