Study On Novel Laser Induced Breakdown Spectroscopy Methods For Detection Of Dairy Quality And Safety

The quality and safety of dairy products,which is directly related to human health,has always been one of the focuses of great concern to the whole society.The expensive equipment,complicated operation,and low detection efficiency combined to limit the applications of traditional detection technologies in practical screening of dairy products at the level of tens of millions of tons efficiently.Therefore,the development of novel and efficient detection methods of dairy product quality and safety is essentially necessary.Among enormous detection technologies,laser-induced breakdown spectroscopy(LIBS)has excellent development potential in the quality and safety detection of dairy products,because of its unique advantages such as short detection time,multi-element simultaneous detection and simple operation.However,the quantitative analysis accuracy of LIBS technology is unsatisfied because of the low sensitivity and matrix interference.In this thesis,LIBS technology and chemometrics methods are combined to detect the quality and safety of dairy products,and the corresponding sample pretreatment methods were developed.Thus,the sensitivity of LIBS technology to detect dairy products was significantly improved.The work of this thesis is divided into the following two parts:In this thesis,taking Cd,Cu,and Pb as the typical analysis element,LIBS technology was applied for the quantitative analysis of heavy metal in milk.The displacement reaction was introduced to the sample pretreatment,and the heavy metal elements in milk were enriched on the surface of magnesium alloy.To further improve the accuracy of LIBS quantitative analysis,the random frog algorithm was used to extract the intrinsic signal of heavy metals from the complex LIBS spectrum accurately,which improves the detection sensitivity of Cd,Cu,Pb significantly.The satisfactory results showed that the detection limits of Cd,Cu,and Pb were 0.173 ppm,0.216 ppm,and 0.234 ppm,respectively,and their R~2are reaching 0.97.A new method for quantitative analysis of lactoferrin and other nutritional enhancers in infant milk powder based on LIBS was also developed.The method combines the sample pretreatment technology and LIBS spectroscopy.In sample pretreatment,the lactoferrin was saturated by using divalent iron ions.The free ions were removed by water solubility and other proteins were removed according to the different isoelectric point.On this basis,LIBS was used to detect the content of iron in the sample,and a quantitative calibration model was established.The detection limit was 0.160 mg/g,and the spiked recovery rate was between 89.3%and 106.3%.The satisfactory results show this method can effectively meet the detection of lactoferrin in infant milk powder in the market.