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Formula milk element quantification
2020-04-25 22:52:41   


The application of the high sensitivity X-ray fluorescence spectrometry for the detection of the nutritional elements of the infant formula milk powder.


一、 Overview

     Minerals in the infant formula milk powder, such as calcium, iron, zinc, manganese, copper, phosphorus, potassium, iodine and other nutrients, are important substances to maintain normal life activities and are conducive to the health and intellectual development of the infants. But if the infants ingest too many or too few mineral elements, it will harm the health of the infants.

       The manufacturers of the formula milk powder need to quickly detect the concentration of the nutrient elements to meet the purpose of the quality control. The customs supervision of the import and export, as well as the domestic market supervision, need to quickly and quantitatively detect the concentration of the nutrient elements in the formula milk powder. The detection methods of the mineral elements in the milk powder are the atomic absorption method, ultraviolet spectrophotometry, etc. These detection methods have some problems such as the complex pretreatment of the samples, long detection cycle, and loss of the elements during the pretreatment. The ultraviolet spectrophotometry for the inorganic elements such as phosphorus and chlorine is also relatively complicated. These analysis methods are difficult to meet the needs of the rapid detection of the minerals and other nutrients in the formula milk powder. Therefore, the method with the ability to quickly detect nutrient elements in the formula milk powder is the practical demand for the industry.

       The high-sensitivity X-ray fluorescence spectrometry such as PHECDA series adopts the technology of the monochromatic focusing excitation to realize the ultra-low detection limits of the elements. Meanwhile the advanced fast fundamental parameters method (Fast FP) can quantitatively detect the nutrient elements of the formula milk powder in the absence of the standard samples. This method has the characteristics of the simple sample preparation and fast detection speed, which can meet the requirements of the rapid detection of the multiple mineral elements in milk powder.



二、 The pretreatment of the samples


Three kinds of the formula milk powder from the different countries
(Australia:Augood、Netherlands:kabrita、Newzerland:a2milk)


•  The preparation of the samples:




三、 Experimental datas
•  LOD

                                   Table 1: LOD of the elements in milk powder matrix by PHECDA-PRO
                                                             unit:mg/kg
elements K Ca Cu Zn Fe Mn Cl P I Se
LOD 5.0 6.0 0.5 0.2 1.2 0.28 34 333 0.37 0.15
 
note:analysis time 400s,LOD=3*SD(7 numbers). 

         The high-sensitivity X-ray fluorescence spectrometry such as PHECDA-PRO has the lower detection limit, which can meet the requirements of the quantitative detection for the trace mineral elements in the formula milk powder.


•  Accuracy

       The accuracy comparison of the elements for the imported milk powder from three different origins is provided. The marked value of each element content are provided by the formula table of the purchased milk powder.
 
Table 2: Accuracy comparison of the elements in the formula milk powder
                                                                                                                                                                unit:mg/kg
Name Elements Fe Cu Zn Mn P(%) Cl(%) K(%) Ca(%) I Se
Augood Marked value 74 3.5 50 0.49 0.454 0.64 0.835 0.81 0.98 ——
Test value 73.19 4.57 48.72 0.50 0.50 0.63 0.83 0.81 1.46 ——
Relative deviation -1.1% 30.5% -2.6% 1.4% 10.4% -1.2% -0.2% -0.3% 49.0%  
kabrita Marked value 38 3.31 32 0.32 0.3 0.482 0.592 0.438 0.89 0.14
Test value 47.62 4.18 37.48 0.40 0.44 0.46 0.48 0.46 1.12 0.06
Relative deviation 25.3% 26.3% 17.1% 26.4% 46.8% -3.6% -19.1% 4.8% 26.0% -54.8%
a2milk Marked value 55 3.65 51 3.2 0.26 0.34 0.54 0.39 0.7 0.183
Test value 51.70 4.01 48.04 3.47 0.31 0.42 0.47 0.35 0.71 0.12
Relative deviation -6.0% 10.0% -5.8% 8.6% 18.4% 23.0% -13.8% -10.6% 1.7% -36.2%
Note: The marked value is given by the table of the milk powder, and the test value is calculated by the fast FP algorithm

           The accuracy analysis results of three kinds of the formula milk powder indicate that the relative deviations of the elements such as Fe, Cu, Zn, Mn, P, Cl, K, and Ca are basically within 20%. The concentration of I and Se is extremely low (below 1mg/kg) The deviation is slightly larger.

           In addition, the test value is calculated by Fast FP algorithm without any correction. If there is the correction by few standard samples, the accuracy will be improved.



•  Repeatability
Table 3 :The repeatability results of the elements of the Augood milk powder
                                                                                                                                                                                                                               unit:mg/kg
  磷(%) 氯(%) 钾(%) 钙(%) 一世
标价 74 3.5 50 0.49 0.454 0.64 0.835 0.81 0.98
样品一 72.12 4.62 48.68 0.476 0.531 0.638 0.817 0.825 1.58
样品二 76.00 4.72 49.68 0.43 0.517 0.618 0.865 0.799 1.35
样品三 74.17 4.2 48.41 0.405 0.483 0.621 0.847 0.801 1.41
样本四 71.96 4.72 49.13 0.609 0.469 0.650 0.834 0.822 1.62
样品五 72.55 4.61 48.51 0.548 0.506 0.630 0.839 0.790 1.55
样品六 72.35 4.53 47.89 0.514 0.500 0.636 0.797 0.806 1.25
平均 73.19 4.57 48.72 0.50 0.50 0.63 0.83 0.81 1.46
         相对偏差              -1.1%             30.5%        -2.6%         1.4%          10.4%          -1.2%          -0.2%          -0.3%          49.0%    
RSD 2.2% 4.2% 1.3% 15.3% 4.5% 1.9% 2.8% 1.7% 10.0%

note: The samples from the same bottle of the milk powder for 6 times respectively. test time: 400s/per
 
       The results of the repeatability showed that the PHECDA-PRO has good repeatability, and the concentrations of the mineral elements in the Augood milk powder are average.


四、 Application solutions
       The solution for the rapid detection of the nutritional elements in the formula milk powder: High sensitivity X-ray fluorescence spectrometer and the fast fundamental parameters method


•  High sensitivity X-ray fluorescence spectrometer(HS XRF®
       The monochromatic wavelength excitation XRF with the hyperboloid curved crystal as the core can greatly reduce the background of the scattered rays, improving the signal-to-noise ratio of the element fluorescence intensity. The limit of detection of the elements can meet the requirements of the accuracy for the nutrient elements in the formula milk powder;
•  Advanced fast fundamental parameters method(Fast FP®
       The fast fundamental parameters method can automatically deduct the baseline and match the background. At the same time, it can automatically identify and calculate various interference of the spectrum lines. The deviation caused by the calculation can be corrected through a small number of the standard samples and obtain accurate quantitative values of the elements;


The following figures are the fitting spectrum of various elements in milk powder on the different energy:





五、 Advantages

•  Quantitative analysis
      The high-sensitivity X-ray fluorescence spectrometers such as PHECDA-PRO series have extremely low limits of the detection. The rapid fundamental parameters method eliminates the differences of the matrix and interference of the spectral lines to obtain more accurate quantitative analysis;

•  Simple pretreatment for the samples
      The preparation of the samples does not require many complicated pretreatment, reducing the errors caused by the complex pretreatment;

•  Easy to operate
      The operation procedures of the apparatus are simple and easy to learn, so the analysts are easy to learn and operate;

•  The portability for the Mobile
     PHECDA-PRO have the excellent portability for the mobile. They have not stringent requirements on the detection environment, and have the strong environmental adaptability;

•  Batch testing
     PPHECDA-HE are equipped with the 30-bit automatic sampling device to meet the needs of the laboratory batch testing.





Conclusions

The PHECDA-PRO series HS XRF spectrometers demonstrated very low limits of the detection and the FAST FP® method eliminated or minimized the matrix effects and the interference of the spectral lines. The results obtained without calibration standards demonstrated very good results compared with the product label results.
 
The simple steps of the sample preparation significantly reduced sample analysis time and the analytical errors. It makes this technique a powerful tool for the purposes of production line real-time quality control.
 
The portability of the PHECDA-PRO series plus the strong environmental adaptability enables operator to use the instrument at anytime and anywhere to meet the business requirements of different industries. 
 
PPHECDA-HE series are equipped with the 30-position autosampler which meets batch analysis requirements in a commercial laboratory.
 
The most important feature is that the FAST FP® method can quantitate trace, minor and major elements without calibration standards for many other matrices such as soils, foods, agricultural produces, pharmaceutical products, industrial wastes, waste water, air filters, and liquid samples such as oils.