Objective: To develop a method using existing quality control equipment for the quantification of amino acids in an infusion preparation.

Background: Amino acid infusion, in particular L-Arginine (L-Arg) and L-Lysine (L-Lys), plays a critical role in Nuclear Medicine therapy using ¹⁷⁷Lu octreotate. The urinary clearance of ¹⁷⁷Lu octreotate from plasma is rapid, imparting a high absorbed radiation dose to the kidneys. Co-infusion of L-Arg/L-Lys amino acid mixtures has a marked reno-protective effect, reducing the risk of therapy-related renal failure. This "blocking" effect is dependant upon the quantity of the amino acid infused (25 g/L L-Arg and 25 g/L L-lys) and hence patient safety demands that the infusion be tested to ensure correct amino acid concentration.

Method: The High Performance Liquid Chromatography (HPLC) system employed was that used routinely for [¹⁸F]FDG quality control. This system includes a CarboPac PA10 column (Dionex) and a HPLC pump (Shimadzu) equipped with an electrochemical detector (Antec-Leyden) operated in the pulsed mode with a gold working electrode. The mobile phase consists of 100 mM NaOH and is delivered isocratically at 1 mL/min.

Results: Baseline resolution of the two amino acids is achieved with retention times of approximately 2 and 3 minutes. The high sensitivity of the detector dictated the dilution of samples with water before injection. Calibration curves yielded linear plots with good reproducibility.

Conclusion: A method was developed for the rapid analysis of L-Arg/L-Lys amino acid infusion using the same system employed for [¹⁸F]FDG quality control.