Utilization of ultraviolet‐visible spectrophotometry in conjunction with wrapper method and correlated component regression for nitrite prediction outside the Beer–Lambert domain

The determination of nitrite concentration is crucial due to its toxicity. A novel model has been developed to accurately determine nitrite concentration within the non‐linear range, utilizing the Zambelli method. Previously, techniques for measure nitrite concentration were primarily restricted to the linear range. This new method employs UV‐Visible absorption spectra and correlated component regression (CCR) to determine nitrite concentration within the range of 0.27–11.34 ppm. A wavelength selection strategy in conjunction with partial least squares (PLS) was implemented prior to applying CCR. The spectral data underwent pre‐processing using standard normal variant (SNV) and Savitzky Golay (SG) techniques, and a backward selection (BS) strategy with PLS was applied to select wavelengths. The 15 most sensitive wavelengths, determined through the RMSE_CV criterion, were utilized to create a PLS model within the range 377–497 nm, resulting in a model with R²_C = 0.9999 and R²_CV = 0.9999, RMSE_C = 0.006, RMSE_CV = 0.027. A CCR model was then established using the 15selected wavelengths and nitrite concentration. The results yielded strong correlation between predicted and measured nitrite values with R²_C = 0.9996, RMSE_C = 4.7491 E‐15, RMSE_CV = 0.0004, and MAPE = 0.68%. The method has been validated through an accuracy profile, which demonstrates that 80% of future results will fall within the 10% acceptability limit within the validation range of 1.30–8.83 mg/L.