Development and validation of spectrophotometric method of determination of N-acety- L-cysteine ethyl ester using sequential injection analysis : master thesis

Korištenjem slijedne analize injektiranjem uz spektrofotometrijski detektor optimizirana je i vrednovana nova metoda određivanja N-acetil-L-cistein etil estera (NACET). Temelji se na redoks reakciji u kojoj NACET sudjeluje kao reducens pri čemu nastaje ljubičasto obojeni [Cu(BCA)2]+ kompleks koji pokazuje apsorpcijski maksimum pri = 562 nm. Univarijantnom metodom odabrani su optimalni parametri protočnog sustava koji omogućuju pouzdano -6određiv-a1nje NACET-a uz -1jednostrano injektiranje reagensa u koncentracijskom području od 8,0 × 10 mol L do 1,0 × 10-4 mol L te uz dvostrano injektiranje reagensa u koncentracijskom području od 6,0 × 10-6 mol L-1 do 1,0 × 10-4 mol L-1. Linearno dinamičko područje je uz jednostrano injektiranje reagensa definirano jednadžbom: y = 3483,4x + 0,0063, uz koeficijent linearne regresije R2 = 0,9900, dok je uz dvostr2ano injektiranje reagensa definirano jednadžbom: y = 3879,8x --10,0045, uz koeficijent linerane regr6esije R-1 = 0,9994. Određene su granica dokazivanja (2,22 × 10-6 mol L ) i granic-a6 određivanja (7,46 × 10- mol L ) za određiva6nje NAC-ET-a uz jednostrano te granica dokazivanja (1,60 × 10 mol L-1) i granica određivanja (5,34 × 10- mol L 1) za određivanje NACET-a uz dvostrano injektiranje reagensa. Ponovljivost signala ima relativno standardno odstupanje od 2,51 % uz jednostrano injektiran reagens te 1,66 % uz dvostrano injektiran reagens. Utvrđeno je i da naizmjeničnim injektiranjem otopina standarda koje su sadržavale različite koncentracije NACET-a ne dolazi do prenošenja signala, bez obzira na analizirane koncentracije NACET-a. Navedeno se odnosi na određivanje NACET-a uz jednostrano te uz dvostrano injektiranje reagensa. Tvari koje se uobičajeno nalaze u sastavu farmaceutskih pripravaka ne interferiraju.A novel sequential injection spectrophotometric method for the determination of N-acetyl-L- cysteine ethyl ester (NACET) was developed and validated. The method is based on a redox re+action in which the reduction of [Cu(BCA)2]2+ complex by NACET occurs forming a violet [Cu(BCA)2] complex with absorption maximum at = 562 nm. Univariate method was used to select optimal parameters of the flow system for a successfull and reliable determination of NACET by standard sampling in the concentration range of the selected analyte of 8.0 × 10-6 mol L--61 to 1.0-× 10-4 mol L-1 and by-1sandwich sampling in the concentration range of the selected analyte of 6.0 × 10 mol L 1 to 1.0 × 102-4 mol L . Linear dynamic range obtained 2by standard and sandwich sampling was y = 3483.4x + 0.0063 (R = 0,9900) and y = 3879.8x-6- 0.0045 (R = 0,9994) respecti1vely. Limit of detection and limit of quantification were found to be 2.22 × 10 mol L-1 and 7.46 × 10-6 mol L- for standard sam1pling. For sandwich sampling limit of detection and limit of quantification were found to be 1.60 × 10-6 mol L- and 5.34 × 10-6 mol L-1. The reproducibility or precision of the method was evaluated by examining the relative standard deviation which was 2.51 % for standard and 1.66 % for sandwich sampling. The obtained results are considered to be satisfactory. Injection of standard solutions containing different concentrations of NACET did not cause signal carryover for standard and sandwich sampling. Comonly present compounds that acompany similar thiols in their pharmaceautical preparations did not show an interfering effect