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Sequential injection analysis of the novel lipophilic amino acid thiol N-acetylcysteine ethyl ester (NACET) with spectrophotometric detection

N-Acetylcysteine ethyl ester (NACET) is a novel lipophilic cell-permeable cysteine derivative with an unusual pharmacokinetic feature and remarkable antioxidant potential. According to the reported data, NACET has the potential to substitute its congener N-acetylcysteine (NAC) as a mucolytic agent, as a paracetamol antidote and as a glutathione-related antioxidant. Therefore, herein we propose a sequential injection analysis (SIA) method for the determination of NACET. The developed and validated method is based on a redox reaction, where NACET reduces Cu(II)-neocuproine to a yellow-colored Cu(I)-neocuproine, with maximum absorbance at 458 nm. Cheminert® M50 pump (VICI Valco), a syringe-free stepper motor driven pump, was used for liquid handling. A 10-port selection valve model C25-3180D with a multiposition actuator control module EMHCA-CE (VICI Valco) was used in conjuction with the M series pump. In this flow experiment, sandwich sampling method was conducted by aspirating 150 μL of reagent, Cu(II)-neocuproine (c = 1×10-3 mol L-1), followed by 250 μL of the NACET sample and finally another 100 μL of the reagent into the holding coil. The stacked zones were immediately propelled to the spectrophotometric detector at a flow rate of 4000 μL min-1. Linear response of the detector was recorded as a function of time with a frequency of 5 s-1. Linearity was obtained in the concentration range of 4×10-6 – 3×10-4 mol L-1. The detection limit was found to be 1.2×10-6 mol L-1. Precision (expressed as relative standard deviation) obtained by measuring ten replicates of 8×10-6 and 4×10-5 mol L-1 NACET solutions were found to be 3.1% and 1.9%, respectively. Frequency of analysis was 60 sample injections per hour.

Sequential injection analysis; N-acetylcysteine ethyl ester (NACET); spectrophotometric detection

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