Coupling of ion pair ultrasound assisted-cloud point extraction to microvolume UV-Vis spectrophotometry for speciation analysis of ionic NO2-,NO3-and total NO2-/NO3-without and with reduction in the selected beverage and food matrices

Olgac E., GÜRKAN R.

FOOD ADDITIVES AND CONTAMINANTS PART A-CHEMISTRY ANALYSIS CONTROL EXPOSURE & RISK ASSESSMENT, cilt.37, ss.1811-1830, 2020 (SCI İndekslerine Giren Dergi) identifier identifier identifier

  • Cilt numarası: 37 Konu: 11
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1080/19440049.2020.1811402
  • Sayfa Sayıları: ss.1811-1830


This study proposes a simple, low-cost, easy to use, fast, accurate and reliable ultrasound assisted-cloud point extraction (UA-CPE) method for the enrichment and speciation analysis of low levels of ionic NO2-, NO(3)(-)and total NO2-/NO(3)(-)without and with reduction by micro-volume UV-vis spectrophotometry. The method relies on the reaction of NO(2)(-)with excess iodide at pH 5.5 to form triiodide, and then the extraction of the oxidation product formed by charge transfer into micellar phase of Triton X-114 using cationic redox-sensitive phenazine dye, neutral red (NRH+) as ion-pairing in absence and presence of 1.5 mL of 1.0 x 10(-3)mol L(-1)Br(-)ions. The main variables affecting extraction efficiency were studied and optimised in detail. Under the optimal conditions, the calibration curves in solvent were linear over the ranges of 5-100 and 100-1280 mu g L(-1)with a detection limit of 1.32 mu g L(-1)while the matrix-matched calibration curves prepared from sample extracts were linear over the ranges of 5-125 and 125-1350 mu g L(-1)with a detection limit ranging from 1.15 to 1.50 mu g L(-1)for sample matrices. From pre-concentration of 25-mL sample, pre-concentration and sensitivity enhancement folds of 62.5 and 76.5 were obtained. The accuracy/precision studies after spiking were performed, and observed to be in range of 96.5-99.6% and 1.9-5.7% (15, 75 and 250 mu g L-1, n: 5). The speciation analysis of ionic NO2-, NO(3)(-)and total NO2-/NO(3)(-)was performed from artificially prepared binary mixtures after reduction with a mixture of Zn and NaCl in acidic media. The free NO(3)(-)contents of samples were calculated from difference between free NO(2)(-)and total NO2-/NO(3)(-)contents. After validation by analysis of a certified sample, the method was successfully applied to the speciation analysis of the beverage, cured meat, vegetable and milk samples. After pre-treatment with two sample preparation steps, it was observed that the results obtained were also compatible with each other, statistically validating the method.