Relative Standard Deviations Of Peak Areas Research Articles

Automated capillary liquid chromatography for high sensitivity amino acid monitoring

AbstractAn automated method for determination of trace level amino acids in 2‐μL samples using on‐column sample preconcentration, gradient elution on 50‐μm inner diameter (i.d.) capillary columns packed with 5‐μm reversed‐phase particles, and electrochemical detection is described. The 50‐μm i.d. capillary columns were efficiently coupled directly to an autosampler without increasing zone dispersion by preconcentrating derivatized amino acids at the head of the capillary column and minimizing gradient dwell volume. Using this system, the relative standard deviations (RSDs) of retention time for a 16 component amino acid mixture were between 0.2 and 0.8%. Using an automated microinjection method, as little as 0.3 μL of derivatized sample was consumed to perform a 0.25‐μL injection with peak area RSDs of 3.0‐8.4%, allowing conservation of a majority of the derivatized sample for future analysis. Precision was improved to peak area RSDs of 1.8–4.1% when consuming 1.0 μL of sample per injection. Detection limits were <0.2 nM for most amino acids. The linear solvent strength theory was used to optimize the gradient and allowed resolution of 15 amino acids in 13 min. The final gradient separation was demonstrated to be selective for the neurotransmitter amino acids in the presence of 44 primary amines commonly found in physiological samples. The system was used to characterize amino acid secretion from single pancreatic islets of Langerhans under different physiological conditions with 2 min of temporal resolution. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 24–32, 2001

Optimization of a capillary electrophoresis–electrospray mass spectrometry method for the quantitation of the 20 natural amino acids in childrens blood

This paper describes useful information on the capillary electrophoresis–electrospray ionization mass spectroscopy (CE–ESIMS) interfacing for the analysis of amino acids (AAs) in standard mixtures and in child plasma blood serum. The developed procedure allows quantitation of the 20 natural AAs, in a single run, without any derivatization. Limits of detection as low as 3–20 μmol/l (5–30 pg injected) per analyte were obtained with an efficiency of about 100 000 plates and a peak area relative standard deviation below 4%.

Comparison of ninhydrin and o-phthalaldehyde post-column detection techniques for high-performance liquid chromatography of free amino acids

A comparative study of two post-column derivatization techniques for amino acid determination has been completed. Using conventional high-performance liquid chromatography, amino acids were separated on either sodium- or lithium-form, polystyrene-based, strong cation exchangers, then derivatized with either o-phthalaldehyde or ninhydrin. Amino acid detection limits with o-phthalaldehyde are near 5 pmoles for primary amines and 100 pmoles for secondary amines such as proline. Detection limits with ninhydrin are near 100 pmoles. The o-phthalaldehyde system should be the system chosen whenever detection of secondary amino acids is unimportant. Retention time reproducibility averaged 1–4% relative standard deviation for both systems with a median peak area relative standard deviation of 3%. A substantial benefit of amino acid determination by high-performance liquid chromatography is the ease with which one can apply this type of chromatography to solve other separation problems.