3. Sometimes dissolving EDTA can be a slow process. Addition of
some NaOH for pH adjustment while dissolving EDTA will
help it dissolve completely.
4. In case only a small amount of material is available (i.e., below
3–4 g) sample homogenization will be better performed with a
homogenizer for low volume samples such as a Retsch Mixer
Mill MM400 with grinding jars and balls, taking care to precool them with liquid nitrogen.
5. When automated SPME injection is performed, vials should be
sealed with silicone septa. Harder materials in the septum can
produce fiber damage. Additionally, a thin PTFE film in the
inner side of the septum is recommended to prevent sample
contamination.
6. The gas GC injection port should have a specific liner for
SPME (i.e., SPME liner 0.75 mm  6.35  78.5 for Agilent
GCs IP Deact., RESTEK). Standard injection liners have a
higher internal volume and will produce wider peaks and
poor chromatographic resolution, particularly in the region at
the beginning of the chromatogram.
7. In case a Fiber Conditioning Module is not available, the fiber
can be cleaned by remaining an extended time (i.e. 5 min) in
the GC injection port.
8. A manual juicer rather than automated or press type extractors
is highly recommended to prevent contamination with essential oils from the flavedo.
9. Samples should not be stored at higher temperature such as
À20
C, because the volatile profile, including the apocarotenoids, would show a quick evolution along the time of storage.
10. Volatile compounds in the juice are not stable. Therefore,
samples must be thawed immediately before analysis.
11. Volatile compounds are low molecular weight molecules, most
often under 220 amu. When using a quadrupole detector, a
narrow m/z scan range (as the one indicated in this method)
provides either better peak shape (more points per peak) or
higher sensitivity.
12. Criteria for the selection of the m/z of the ion used for integration are adequate abundance of the signal and specificity
with the coeluting peaks. Depending on the volatile profile of
each set of samples, some of the peaks might be integrated
better with a different m/z ion than those proposed in Tables 1
and 2. Therefore, the ions indicated in the table should be
taken as a first choice and further optimized for the type of
matrix under study if necessary.
13. The use of an external standard such as the sample admixture is
essential to correct for variations in detector sensitivity and
Plant Volatile Apocarotenoids
173
some NaOH for pH adjustment while dissolving EDTA will
help it dissolve completely.
4. In case only a small amount of material is available (i.e., below
3–4 g) sample homogenization will be better performed with a
homogenizer for low volume samples such as a Retsch Mixer
Mill MM400 with grinding jars and balls, taking care to precool them with liquid nitrogen.
5. When automated SPME injection is performed, vials should be
sealed with silicone septa. Harder materials in the septum can
produce fiber damage. Additionally, a thin PTFE film in the
inner side of the septum is recommended to prevent sample
contamination.
6. The gas GC injection port should have a specific liner for
SPME (i.e., SPME liner 0.75 mm  6.35  78.5 for Agilent
GCs IP Deact., RESTEK). Standard injection liners have a
higher internal volume and will produce wider peaks and
poor chromatographic resolution, particularly in the region at
the beginning of the chromatogram.
7. In case a Fiber Conditioning Module is not available, the fiber
can be cleaned by remaining an extended time (i.e. 5 min) in
the GC injection port.
8. A manual juicer rather than automated or press type extractors
is highly recommended to prevent contamination with essential oils from the flavedo.
9. Samples should not be stored at higher temperature such as
À20
C, because the volatile profile, including the apocarotenoids, would show a quick evolution along the time of storage.
10. Volatile compounds in the juice are not stable. Therefore,
samples must be thawed immediately before analysis.
11. Volatile compounds are low molecular weight molecules, most
often under 220 amu. When using a quadrupole detector, a
narrow m/z scan range (as the one indicated in this method)
provides either better peak shape (more points per peak) or
higher sensitivity.
12. Criteria for the selection of the m/z of the ion used for integration are adequate abundance of the signal and specificity
with the coeluting peaks. Depending on the volatile profile of
each set of samples, some of the peaks might be integrated
better with a different m/z ion than those proposed in Tables 1
and 2. Therefore, the ions indicated in the table should be
taken as a first choice and further optimized for the type of
matrix under study if necessary.
13. The use of an external standard such as the sample admixture is
essential to correct for variations in detector sensitivity and
Plant Volatile Apocarotenoids
173