Amino acid analysis is performed on Beckman Instruments Models 6300 and 7300 dedicated amino acid analyzers. These instruments incorporates 10cm cation exchange columns, four sequential lithium-based eluents, and lithium hydroxide for column regeneration. Absorbence is measured at 440 and 570 nm following post-column color development by Ninhydrin reagent at 131 degrees C. Data acquisition and management is accomplished with a computer running Beckman System Gold 8.10 chromatography software. Beckman reference solutions fulfill standardization requirements.
Glucosaminic acid is added to the sample as the internal standard.
Since consistency in pH and molarity of the eluents are primary in reproducibility, all reagents are purchased directly from commercial manufacturers rather than being formulated in house. Although within-lot reproducibility of the Ninhydrin coloring reagent is excellent, we periodically recalibrate the peak areas of the amino acids standards for each bottle of Ninhydrin used. We have spent years refining the classical ion-exchange post column Ninhydrin method of amino acid analysis for optimum accuracy, precision, and efficiency. Even though this classical method requires extra time and costly reagents and instrumentation, we have determined that the alternative methods commercially available cannot achieve the level of precision that we demand in serving our clients needs. Because various matrices require different amino acid profiles, we offer analysis tailored to a wide variety of materials.