Worldwide Solutions - February 2008 - (Page 8) GERSTEL Solutions Worldwide Application Total Ion Chromatogram (A) and detail between 1.0 and 3.0 minutes (B) of the HS-SPME-GC/MS analysis of ten grams of apple sauce / compote. For a list of compounds, see table. Mass spectrum at tR = 2.002 min (A) and NIST spectrum of 2-Methyl-1-butylacetate (B). The RIC used a 6890 GC coupled with a 5975 MSD, both from Agilent Technologies, for fast GC analysis of apple flavor compounds. The GC was equipped with a GERSTEL MACH module providing fast separations and fast cool-down. Sample preparation was performed automatically using the GERSTEL MultiPurpose Sampler. The MPS was also used to introduce the analytes to the GC inlet GERSTEL Cooled Injection System (CIS). The picture shows the newer model 7890 GC with a dual MACH module. Peak number Compound 1 Hexane Butanol 2 3 Propylacetate 4 Hexanal 5 Butylacetate 6 2-Hexenal 7 1-Hexanol 8 2-Methyl-1-butylacetate 9 Butylpropanoate 10 Pentylbutanoate 11 Butylbutanoate 12 Hexylacetate 13 2-Methyl-butylbutanoate 14 Hexylpropanoate 15 Hexylbutanoate 16 Estragole 17 Hexyl-2-methylbutanoate 18 Hexylhexanoate 19 Butylbenzoate alpha-Farnesene 20 RT [min] 1.159 1.481 1.646 1.814 1.869 1.926 1.989 2.002 2.045 2.057 2.192 2.218 2.266 2.341 2.445 2.464 2.500 2.652 2.663 2.804 SD [min] 0.000 0.001 0.001 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.000 0.000 0.000 0.000 Peak [w 1/2 min] 0.010 0.013 0.014 0.007 0.007 0.005 0.005 0.005 0.005 0.005 0.005 0.006 0.005 0.006 0.006 0.006 0.006 0.006 0.006 0.008 Selected identified flavor compounds from a ten gram apple sauce sample, determined by HS-SPME-GC/MS. The analysis was repeated in triplicate, the standard deviation (SD) of the retention times was always below 0.001 min. column inside the MACH module was a 10 metre, 100 µm i.d., DB 1 MS column with a film thickness of 1 µm. The column outlet was connected to the MSD via a 50 cm long, 100 µm i.d. deactivated fused silica capillary that was also kept inside the GC oven at 250 °C. Both Transfer capillaries were connected to the column using zero-dead-volume connectors. Flavor profiling in three minutes with a GC cycle time of only 4.5 minutes The MACH module was operated with the following temperature program: Initial temperature: 25 °C, rate 50 °C/ min to 105 °C, held for 0 minutes. Rate 2: 250 °C/min to the final temperature of 250 °C, held for 30 seconds. The transfer capillaries were kept at a constant temperature of 250 °C. The MSD Ion Source and Quadrupole temperatures were set to 230 and 150 °C respectively. The MSD was operated in fast scan mode between m/z 33 and 300. The data acquisition rate was set to 21 Hz. Unlike the classical GC oven, the MACH module cools within seconds, ensuring that the cycle time can be kept to only a few short minutes. “The complete apple flavor profile was available after three minutes and the GC/MS system was generally ready for the next analysis after 4.5 minutes”, the RIC scientists reported. The peak width at half heigth (w1/2) was within the range from 0.010 to 0.014 minutes, equal to around 600 to 780 milliseconds for most of the volatile organic compounds (VOCs) such as hexane, butanol and propylacetate. Peak widths (w1/2) for all other compounds were between 0.005 and 0.007 minutes, equal to from 300 to 420 milliseconds. The narrowst peaks had a peak width of around 0.01 minutes at base line. At the set scan rate, more than ten points were taken across the peak, enabling reliable quantitation. For more information: AppNote 8/2006, „Fast Screening of Apple Flavor Compounds by SPME in Combination with Fast Capillary GC–MS using a Modular Accelerated Column Heater (MACH) and Quadrupole Mass Spectrometric Detector (qMSD)“ , http://www.gerstel.com/p-gc-an-2006-08.pdf GERSTEL Solutions Worldwide – February 2008 8 http://www.gerstel.com/p-gc-an-2006-08.pdf
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