A Discovery C18 (Supelco, Bellefonte, PA, USA) column
(250 mm × 4.6 mm i.d.) fully-end-capped, with spherical
shaped 5-m particles and with carbon load 12% (3mol m−2)
was used together with a C18 (25 mm × 4.6 mm i.d., 5m) guard
column (Supelco). A C18 column was used as the most common
column type, available in every routine laboratory.
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