Analysis Of Chelate Of Glycine Trace Element Mixing Sulfate Based On Middle Infrared Spectroscopy

Glycine trace element chelate is an important feed additive.As a product with high selling price and high benefit,the chelate of glycine trace element mixed with cheap sulfate is a serious problem.The lack of rapid and effective identification and screening methods is a risk factor for feed quality and safety.Mid-infrared Spectroscopy?Mid Infrared Spectroscopy,MIRS?has a wide application,convenient operation,rapid test and of good repeatability.In this study,we analyzed and compared the mid-infrared spectral characteristics of the glycinate iron chelate,glycinate zinc chelate,glycinate copper chelate,glycinate manganese chelate and their sulfate mixed samples,and constructed a qualitative discriminant model and a quantitative analysis model for adulteration identification by partial least squares method and other chemometrics,providing a way for the rapid screening of glycinate trace element chelate mixed samples.The results also laid a methodological foundation for the further improvement of the middle infrared spectroscopy method for the determination of amino acid trace element chelates.The main innovative achievements of this paper are as follows:?1?With the chelate of glycine trace elements?iron,zinc,copper and manganese?,sulfate?iron,zinc,copper and manganese?and 1%?90%mixed samples as the research objects,the mid-infrared spectra of the KBr tablet samples in the range of 4000?400 cm-1 were obtained by using the Fourier transform near-infrared system.The characteristic absorption peaks of the four glycine trace element chelates were all located in the 1600?500 cm-1 band,and the absorption peaks of the metal-oxygen stretching vibration were mainly distributed around 520 cm-1.Compared with the chelates of glycine trace elements,the absorption peaks of the four kinds of sulfates were all less,but they all had the same absorption peaks near 1100 cm-1 and 610 cm-1,corresponding to the characteristic absorption of sulfate and metal-oxygen,respectively.The spectral trend of the four glycine trace element chelates and the mixed samples is basically the same,and the spectrograms of the four glycine trace element chelates all have great overlap and similarity.In addition,with the increase of the mixing concentration,the intensity of the absorption peaks of the four glycine trace element chelates in the band of 1650?1200cm-1 becomes lower and lower,while the absorption peaks of sulfate and metal-oxygen become more and more higher.?2?Based on partial least squares discriminant method,this paper constructs the four kinds of trace elements glycine chelate discriminant model:the qualitative identification the mixing of the spectral range of 1300?1000 cm-1 spectrum using normalized,smooth and first derivative pretreatment,glycine chelate qualitative discriminant model validation set discriminant sensitivity was 100.0%,the accuracy is 99.6%.The spectra of 2000?1300 cm-1 were pretreated with standard normal change,smoothing and first derivative.In the qualitative discriminant model of glycine zinc chelate,the discriminant sensitivity and accuracy of the verification set were 97.7%and 96.8%respectively.Standard normal change,smoothing and second derivative pretreatment were used for spectra in the spectral range of 1800?1300cm^-1.In the qualitative discriminant model of glycine copper chelate,the discriminant sensitivity of the verification set was 96.2%and the accuracy was 97.3%.Multiple scattering correction,smoothing and first derivative pretreatment were used for the spectrum range of 1300?1000 cm^-1.In the qualitative discriminant model of glycine manganese chelate,the discriminant sensitivity of the verification set was97.2%and the accuracy was 94.3%.?3?Based on the partial least squares regression analysis,this paper constructs the four kinds of trace elements glycine chelate identification model of quantitative analysis of mixed:glycine iron chelate content of mixed forecasting model validation set decision coefficient is 0.88,the root mean square prediction error is 0.38,the optimal spectral preprocessing for normalization,smooth and first derivative combination,the optimal spectral range is 1300?1000 cm^-1;The validation set determination coefficient of the prediction model for the content of glycine zinc chelate was 0.87,and the prediction root-mean-square error was 0.62.The optimal spectral pretreatment was the combination of standard normal change,smoothing and second derivative.The optimal spectral range was 2000?1300 cm-1;The validation set determination coefficient of the prediction model for the content of glycine copper chelate was 0.86,and the prediction root-mean-square error was 0.71.The optimal spectral pretreatment was the combination of standard normal change,smoothing and second derivative,and the optimal spectral range was 1800?1300 cm-1;The validation set determination coefficient of the prediction model for the content of glycine manganese chelate was 0.83,and the prediction root mean square error was 0.79.The optimal spectral preprocessing was multiple scattering correction,smoothing and the combination of second derivatives,and the optimal spectral range was 1300?1000 cm-1.