Separation, Enrichment And Determination Of Azo-dyes In Food By Buoyant Adsorbents Based On Hollow Glass Beads

Sample pretreatment is very important for sample analysis.It not only consumes the vast majority of time?70%⁸0%?of the whole analysis process,but also directly affects the accuracy,precision and detection limit of the analysis.Therefore,developing more efficient,rapid and convenient sample pretreatment methods is a hotspot and bottleneck in the field of analytical chemistry.Dispersive solid phase extraction?d-SPE?is one of the most important sample pretreatment technique and magnetic separation is the most effective separation technique for complex samples.But the surface modification process of magnetic materials is tedious and the chemical properties are unstable.Based on this,two kinds of buoyant d-SPE adsorbents were prepared by using low-density hollow glass beads?HGMs?,and they can be easily separated from the matrix only by flotation after adsorbing dyes in solution.Therefore,the synthesized d-SPE adsorbents were applied to the separation,enrichment and detection of two dyes.The main researches are as follows:Firstly,the buoyant d-SPE adsorbent HGMs/KH-831 was prepared by modification of the surface of HGMs with n-octyl trimethoxysilane for the separation,preconcentration and detection of Sudan III.The adsorbent was characterized by scanning electron microscopy?SEM?,thermogravimetric analysis?TGA?and infrared spectrometer?IR?.It showed good stability and adsorption ability,and could selectively adsorb Sudan III by hydrophobic action due to the non-polar octyl on the surface of adsorbent.During the process of enrichment,the adsorbent could be easily separated from sample solution only by flotation after the adsorption of Sudan III because of the low density of HGMs.The adsorbed Sudan III can be eluted by ethanol and consequently determined by colorimetric method.The experimental conditions such as adsorption time,temperature,pH value and adsorbents'dosage were optimized,and the adsorption kinetic and thermodynamic of the buoyant adsorbent for Sudan III were investigated.Finally,a spectrophotometry for the determination of Sudan III was established with linear range of 0.10⁴.00 mg/L?R²>0.999?and detection limit of 0.048 mg/L under the optimum conditions.The proposed method was successfully employed to detect Sudan III in pepper products with acceptable recoveries of spikes?90.7%¹02.0%?.In addition,the adsorbent could be reused due to its high efficiency in the enrichment of Sudan III after desorption.The results indicated that HGMs/KH-831had a potential application prospect in the enrichment and detection of organic contaminants with weak polarity.A buoyant ALG/3-APTS/HGMs composite extraction adsorbent for enrichment and detection of anionic dye-amaranth was prepared by surface modification of HGMs using3-aminopropyltrimethoxysilane?3-APTS?and coated with sodium alginate.Infrared spectra showed that the surface of the adsorbent contained abundant azyl and could selectively adsorb anionic dye amaranth after protonated under acidic conditions.The adsorbent could be easily separated only by flotation after the adsorption of amaranth for the low density of HGMs,and then the amaranth can be eluted by Na₂SO₄ solution followed by colorimetric detection.After optimizing the experimental conditions,the adsorption kinetic and thermodynamic of the adsorbent for amaranth were investigated.Finally,a colorimetric method for the determination of amaranth was established.This method showed a linear calibration plot over the amaranth range of 0.020².00 mg/L?R²>0.998?and the detection limit was 0.0021 mg/L under the optimum conditions.The proposed method was also successfully employed to detect amaranth in beverage with acceptable recoveries of spikes?97.9%¹05.9%?.The results indicated that the spectrophotometry based on the buoyant composite adsorbent could be applied to the determination of anionic colorants in real samples.