Rapid analysis of organic and amino acids by capillary electrophoresis: application to glutamine and arginine contents in an ornamental shrub

Soluble nitrogen-containing compounds in plant extracts are often measured using chromatographic techniques that require not only previous derivatisat ion and a long analysis time, but are also costly. Two rapid methods were d eveloped for analysing NO3-, organic, and amino acids by capillary electrop horesis (CE). A mixture of NO3-, organic, and amino acids was separated wit hin 7 min, directly from a plant extract with good repeatability and linear ity. An alternative method, requiring the previous purification of a plant extract on resin, improved the identification of amino acids in samples wit h numerous peaks and a low amino acid content. These two methods were used to evaluate the soluble nitrogen-containing compounds in an ornamental shru b (Ligustrum ovalifolium) subjected to three fertigation timetables. Argini ne and glutamine were the main compounds observed in the plants during N re distribution. Their contents increased dramatically in autumn. In December, arginine followed an increasing gradient from the roots to the trunk and d ecreased from the lower to the upper parts of stems. The more fertilisation the plants received, the higher the arginine content. Glutamine content wa s lowest in the three treatments. In March, arginine and glutamine contents returned to their minimal values.