Applicationof QuEChERS Techniquefor The Analysis And Confirmation Of Harmful Pollutants In Food

Food matrix is very complex and the content level of harmful substances in food is too low to be accurately detected.Therefore,appropriate extraction,enrichment and purification methods should be adopted in the sample pretreatment for harmful substances determination in food.QuEChERS purification technology is widely accepted in the advantages of ‘‘quick,easy,cheap,effective,rugged and safe”.In this study,QuEChERS purification techniquecombined with ultra-high performance liquid chromatography/tandem mass spectrometry(UPLC-MS/MS)and gas chromatography-mass spectrometry GC-MS)were adopted to determine quaternary ammonium compounds,N-nitrosamines and organophosphate esters in various foods.Three novel methods besed on the QuEChERS-based purification and UPLC-MS/MS or GC-MS were established to detect six quaternary ammonium compounds in dairy products,six N-nitrosamines in soy sauces and nine organophosphate esters in milk.The major contents and results were summarized as follows:(1)A robust method based on QuEChERS technique coupled with ultra-high performance liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS)was developed for the simultaneous determination of four bisphenol compounds in milk powder.A two-step extraction method,direct extraction with acetonitrile followed by salting outacetonitrile extraction,was adopted in the extraction of target analytes in milk powder.After that,the extraction solution was concentrated and subsequently purified by QuEChERS technique.4 target analytes were separated on a Phenomenex kinetex C18 column,detected by MS/MS under multiple reaction monitoring and quantified by an internal standard method.The method was validated in terms of the sensitivity,linearity,recovery and precision,and matrix effect.The results indicated that favorable linear relations(r>0.99)were obtained for all analytes at their respective concentration ranges and their limits of quantification were in the range of 0.15–0.35 mg/kg.The mean recoveries were calculated at three spiked levels and the values were found between 80.7 %and 112 %with relative standard deviation ranging from 4.7-10.1% and the inter-day precision ranging from 8.4-12.1%.The developed method is accurate and rapid and suitable for the simultaneous determination of bisphenols in milk powder and other dairy products.(2)A novel method was established to identify nine organophosphate esters in milk using UPLC-MS/MS.Samples were dissolved in water,and added in isotope internal standard.Then the target analytes were extraced from samples with acetonitrile containing0.5%formic acid by vortex and ultrasound,and purified by QuEChERS technique,finally separated with a Phenomenex kinetex PFP column,employing acetonitrile-0.1% formic acid as the mobile phase in a gradient elution mode,and detection with tandem mass spectrometry under ESI at positive and multiple reaction monitoring(MRM)mode.The targets were qualitatively confirmed by retention time and abundance ratio of daughter ions,and quantified by isotope internal standard.Under the optimized conditions,the method detection limits(MLODs)of the targets were ranged from 0.2 to 0.5 ?g/kg,and the linear range were 1.0-200 ?g/L with the correlation coefficients greater than 0.998.The average recoveries ranged from 73.5% to 110.2%,and within-day precisions in a range of 3.9-8.9%when three levels of standard were spiked into milk.At the middle spiked level,the inter-day precisions were less than 11%.The developed method is simple,sensitivity and accuracy,and it is competent for the detection of nine organophosphate esters in milk.(3)A sensitive and rapid method was established for the determination of six N-nitrosamines(NAs)in soy sauces using QuEChERS clean-up and isotope dilution-GC-MS.The samples were firstly extracted by ethyl acetate,then the extracting solution was concentrated by slow nitrogen gas blowing and subsequently purified using QuEChERS method.All of the samples were separated by INNOWAX capillary chromatographic column,and detected by selected ion monitoring(SIM)mode of GC-MS and quantified by isotope internal standard method.Under the optimized condition,the specificity of this method was favorable,matrix effects of target analytes in two kinds of soy sauces(light and dark soy sauce)can be ignored.The linear range was 2.0-200 ?g/L for six analytes with the correlation coefficients greater than 0.9994.The limits of detection(LODs)and the limits of quantitation(LOQs)of the method were 0.4-0.9 ?g/kg and1.2-3.0 ?g/kg,respectively.The average recoveries of six N-nitrosamines at three spiked levels in negative soy sauce were within 80.2%-112%,with relative standard deviation(RSD,n = 6)of 2.5%-6.8%.The method was simple,rapid,with good-repeatability,and successfully applied to analyse thirty soy sauces and N-nitrosopiperidine(NPIP)was detected in one sample.