. Amino acid analysis is one of the most important technologies in life-science research. Amino acids are the basic building blocks of human proteins. Except for a few aromatic amino acids, most amino acids have weak UV absorption, so direct detection with a UV detector has low sensitivity and strong interference. In recent peptide-drug research, amino acid composition analysis (Amino Acid Composition Analysis, AACA) has become an indispensable core step. For example, amino acid sequence verification is essential because the biological activity of peptide drugs depends strongly on their amino acid sequence and composition.
By analyzing amino acid composition, researchers can verify whether a synthesized peptide matches the target sequence and avoid functional failure caused by synthesis errors such as missing amino acids, substitutions, or unexpected modifications. For amino acid structural characterization, when combined with mass spectrometry (MS) and chromatographic techniques such as HPLC-CAD, amino acid composition analysis can help interpret the molecular structures of complex peptides, including peptides containing non-natural amino acids or post-translational modifications, and ensure that they meet design requirements. Direct non-derivatized detection of 17 amino acids by charged aerosol detection (CAD) combined with high-performance liquid chromatography (HPLC) shows significant technical advantages.
Compared with traditional methods, this technique eliminates cumbersome derivatization steps and avoids sensitivity fluctuations and quantitative bias caused by unstable derivatization reagents, side reactions, or diverse products. The universal detection principle of CAD gives high-sensitivity response to nonvolatile and weak-UV-absorbing compounds such as amino acids, enabling accurate detection without relying on modification of specific functional groups. This method simplifies sample preparation, shortens analysis time, reduces the use of toxic reagents, and aligns with green chemistry. Its wide dynamic range and good linearity also support simultaneous quantitative analysis of multiple amino acids in complex matrices such as biological fluids and food samples, making it especially suitable for rapid screening and quality control in high-throughput laboratories. Studies confirm that the method performs well in retention-time stability, repeatability, and recovery, providing an efficient and reliable analytical solution for life sciences, clinical diagnosis, and the food industry. This article uses reversed-phase HPLC combined with the Instrumax charged aerosol detector (CAD) to directly determine 17 amino acids. The method is fast, simple, accurate, highly sensitive, repeatable, and linear, providing strong technical support for amino acid testing and peptide-drug research. Click to view full text