Detection And Analysis Of Characteristics Of Edible Oils Viaftir Sprctroscopy Using Infrared Quartz Cuvette

The quality of edible oil is affected by many factors,and its quality is closely related to human health.Traditional methods of edible oil quality determination involve a great number of organic solvents that are highly toxic,carcinogenic,and polluted to the environment.Pretreatment of samples is cumbersome and time-consuming.With the development of technology and detection instruments,many instruments which are fast,sensitive and visual have been widely used in detection of edible oil quality because of its simplicity,low consumption,high efficiency,non-destructiveness,high accuracy and sensitivity,such as spectrophotometer and chromatography methods.Quartz cuvetteas a common accessory of samples collection is widely used in different instruments to load sample solutions,such as ultraviolet-visible light and near-infrared spectrophotometers.It can provide accurate and suitable optical path lengths during the detection process.In this thesis,several vegetable oils for daily consumption were used as research objects.Infrared quartz cuvette was used as accessories for spectral collection.Infrared spectra of samples were collected in the range of 6000–400 cm^–1.The rapid quantitative methods of peroxide value,acid value and iodine value of edible oil were developed by FTIR based on infrared quartz cuvette.The main contents and conclusions were as follows:?1?FTIR spectra of edible oils were collected with infrared quartz cuvette which is a common spectral accessory.Using triphenyl phosphorus oxide?TPPO?as internal standard and carbon tetrachloride?CCl₄?as diluent,to establish FTIR based on the infrared quartz cuvette?IQC-FTIR?dilution method.In order to simplify the sample preparation and the spectral optical path correction process,explore and establish a dilution calibration method.The results shown that the characteristic absorption peak at 5680 cm^-1 is correlated with the characteristic absorption peak(3147 cm^-1)of TPPO.Based on this,sample dilution modeland the optical path calibration method were established.It can avoid the use of internal standards and the sample can be diluted at 6:1-13 1 randomlyfor sample preparation.The correlation coefficients of spectral dilution calibration and validation models were 0.9913 and 0.9956,and the standard deviations were 0.0077 and 0.0937,respectively.It shown that the spectral calibration method can simplify the sample preparation.The process is simple and easy to operate and provide a spectral processing method for establishing a rapid detection technology for edible oil quality indicators.?2?Combined with the dilution method,establishment of IQC-FTIR method for determination of peroxide value of edible oil.FTIR spectra of samples were collected from6000-400cm^-1.The spectra were calibrated by spectral dilution calibration.The optimum spectral wavenumber band,the optimum spectral pretreatment method and the optimized model were selected to establish a quantitative method combined with partial least squares?PLS?.The established method was validated by titration method.The results shown that the model was the best accurate after first derivative treatment in the range of 3763 cm^-1-3260cm^-1.Correction model correlation coefficient?R?and root mean square error?RMSEC?were 0.9908 and 0.6950,respectively.Model validation,blind sample validation and precision analysis showed that IQC-FTIR method was faster and more accurate than traditional titration method.?3?Establishment of IQC-FTIR method for determination of acid value of edible oil.FTIR spectra of samples with different acid values in the range of 6000-400 cm^-1 were collected and calibrated by spectral dilution calibration model.The optimum spectral wavenumber band,the optimum spectral pretreatment method and the optimized model were selected to establish a quantitative analysis and calibration model combined with PLS.The model was validated by titration method.The results shown that the PLS calibration model was the best for R and RMSEC in the wavelength range of 3603 cm^-1-3250 cm^-1 after first derivative treatment,which were 0.9967 and 0.1350,respectively.Calibration validation,blind sample validation and precision analysis shown that IQC-FTIR method,which was used to quantitative acid value was fast,green and accurate.?4?A method for determination of iodine value of edible oil by IQC-FTIR method was established.FTIR spectra of samples with different iodine values in the range of 6000-400cm^-1 were collected and calibrated by spectral dilution calibration model.The optimum spectral wavenumber band,the optimum spectral pretreatment method and the optimized model were selected to establish a quantitative analysis and calibration model combined with PLS.The model was validated by titration method.The results show that the PLS calibration model is the best for R and RMSEC in the range of 3053-2607 cm^-1 wavelength after standard orthogonal transformation and first derivative processing,which are 0.9967 and0.1350,respectively.Calibration validation,blind sample verification and precision analysis shown that IQC-FTIR method was used to detect iodine value instead of titration method.