Study On The Applications Of Novel Pretreatment Technologies Of Dyes In Environmental Water And Food Samples

Colority is frequently used to roughly evaluate the pollution levels of dyes in environmental water according to present water quality standards in China.Due to that no concentration limits and relevant standard methods exist for the routine detection and monitoring of dyes,it is difficult to clear the types and levels of dyes in environmental water and thus provide the basis for target-oriented governance policies related to water pollution.The food safety problems triggered by dyes illegally added into food are emerging one after another.The current methods for the determination of illegal dyes in food mostly focus on weak polar Sudan dyes and have a limited variety of analytes.Thus the realization of simultaneous determination of different kinds of illegal dyes in food is a realistic requirement for food safety.In this manner,high performance sample preparation is considered as the key technique in the determination of forbidden dyes,especially for ionic dyes.Aiming at probing into the problem,in this study,we prepared polypyrrole nanofibers mat as absorbent and established polypyrrole nanofibers mat-based solid phase extraction(SPE)technique coupled with high-performance liquid chromatography analysis methods of ionic dyes in environmental water and foods.The feasibility was verified by the application of this method in the determination of dyes in a variety of real samples and the comparison with literature methods and the National Standard Methods.The experimental contents are as follows:1.Based on the properties of analytes,nanofibers mat with suitable molecular structures and morphological characteristics was prepared by electrospinning coupled with chemical oxidative polymerization.Several elements,including template materials,reaction duration and doping ions,were checked to explore their effects on the morphology and extraction performance of polypyrrole nanofibers mat.The package rates of polypyrrole,the diameter of fibers and the recovery were used as quality control indexes to guarantee the stability and operability of the nanofibers mat preparation,providing the basis for the polypyrrole nanofibers mat from laboratory to practical application.2.A high-throughput polypyrrole nanofibers mat-based solid phase extraction coupled with high performance liquid chromatography with diode array detector(HPLC-DAD)for the determination of dyes in water samples,including sulphonated azo dyes-acid yellow 9,acid orange and metanil yellow from environmental water and cationic dyes-auramine O,chrysoidine and rhodamine B from wastewater,was established and applied in real samples in order to evaluate the water polution arising from dyes.3.An efficient sample preparation method for simultaneous extraction of four kinds of yellow ionic illegal dyes from food samples was established.After freeze purification,the samples extractant with simple dilution could be concentrated and purified by SPE for HPLC-DAD analysis,which provided a methodoligical basis for determination of illegal dyes in foods.The optimal nanofibers mat as SPE adsorbent was optimized by orthogonal design from five types of nanofibers mat,including PA6 NFsM,PPy/PAN NFsM,PTS-PPy/PAN NFsM,NH2-PAN NFsM and COOH-PAN NFsM.After that,the optimization of SPE conditions was achieved through response surface methodology.The newly established method based on NFsM was evaluated by the comparison with literature methods and the National Standard Method.Then the proposed method was applied in the determination of target forbidden dyes in croakers,bean products and chilli products samples.Besides,the results were compared with those from standard method to verify the feasibility of proposed method and provide the basis for the detection of forbidden dyes in foods samples.The result obtained from the study of SPE based on polypyrrole nanofibers mat as absorbent showed that only a few milligrams nanofibers mat was sufficient for the extraction,which made the volume of desorption solvent reduced greatly,just about a few hundred microliters.The nanofibers mat presented good analytical performance,which satisfied the demand of determining analytes in samples accurately and precisely.At the same time it overcomes the shortcomings of routine extraction methods,such as large consumption of organic solvent,longtime treatment and poor purifying effect in the methods of liquid-liquid extraction and conventional solid-phase extraction.With the advantages of high sensitivity,good repeatability,simple operation and weak disturbance,the method is in conformity with the trend of the Green Cemistry.