A new miniaturized microextraction HS-LPME-OIP procedure for ammonium determination based on Nessler's method

Abstract A recently proposed combination of headspace liquid-phase microextraction with an optical immersion probe (HS-LPME-OIP) was adapted for the spectrophotometric determination ammonium. The developed method is based on conversion ammonium ions to ammonia in a 0.15 M sodium hydroxide solution, followed by absorption 200 µL Nessler's reagent solution preliminary diluted distilled water (1:16.7). extracting phase, which OIP immersed, placed into vial fixed above sample hermetically sealed vessel. analytical signal monitored 30 min at 400 nm. duration analysis can be flexibly adjusted and, if necessary, reduced 5 min. level permissible concentrations some interfering substances, including calcium, magnesium, iron and organic compounds, significantly reduced. LOD equal 0.20 mg L −1 , linear calibration range from 0.70 15 . RSD ranged 2.5 5.2%. successfully applied natural waters, fertilizers CRM samples. Graphical abstract