Use of Sep-Pak C18 cartridges to clean up free amino acids from coniferous needles

Reversed-phase Sep-Pak C₁₈ cartridges were investigated to evaluate their ability to purify free amino acids extracted from jack pine (Pinus banksiana Lamb.) and white spruce Picea glauca (Moench) Voss] needle tissue samples for HPLC analysis. Twenty-one amino acids from a standard only and amino acids from conifer needles with added standard were eluted through Sep-Pak C₁₈ cartridges. An average recovery of 98% was found for all standard amino acids. Using norleucine as an internal standard, recovery for all amino acids except alanine and methionine averaged 104% for jack pine and 97% for white spruce tissue. Alanine co-chromatographed with an unknown peak and recovery appeared to exceed 130%. Methionine, with less than 33% recovery, was probably degraded during the extraction and purification procedures. Aside from alanine and methionine, Sep-Pak C₁₈ cartridges appear to be a faster and more effective method for purifying conifer foliage extracts prior to amino acid analysis than the traditional ion-exchange column purification method.