Ultrasound-assisted analysis of total carbohydrates in environmental and food samples.

Analytical methods to determine total carbohydrates in environmental and food samples usually require a preliminary chemical hydrolytic procedure to convert polysaccharides into monosaccharides prior to detection by colorimetric or chromatographic techniques. In this paper, an alternative hydrolytic procedure is presented. The method for hydrolysis of polysaccharides is based on the application of ultrasound at room temperature. The advantages of the method proposed here are reduced time required for analysis (4-5 h) and the improvement of the analytical accuracy due to the absence of the most common reactions of oxidation. The proposed method was applied to the determination of total carbohydrates in several environmental samples (seawater and marine mucilage) and starchy food samples. Results for total carbohydrate obtained using the ultrasound procedure for hydrolysis of samples agreed with those found when applying other published procedures.     

Layered nanocomposite of zinc sulfide covered reduced graphene oxide and their implications for electrocatalytic applications

Herein, we have synthesized zinc sulfide nanospheres (ZnS NPs) encapsulated on reduced graphene oxide (RGO) hybrid by an ultrasonic bath (50 kHz/60 W). The physical and structural properties of ZnS NPs@RGO hybrid were analyzed by TEM, XRD, EIS and EDS. As-prepared ZnS NPs@RGO hybrid was applied towards the electrochemical determination of caffeic acid (CA) in various food samples. The ZnS NPs@RGO hybrid modified electrode (GCE) exhibited an excellent electrocatalytic performance towards caffeic acid detection and determination, when compared to other modified electrodes. Therefore, the electrochemical sensing performance of the fabricated and nanocomposite modified electrode was significantly improved owing to the synergistic effect of ZnS NPs and RGO catalyst. Furthermore, the hybrid materials provide highly active electro-sites as well as rapid electron transport pathways. The proposed electrochemical caffeic acid sensor produces a wide linear range of 0.015–671.7 µM with a nanomolar level detection limit (3.29 nM). In addition, the real sample analysis of the proposed sensor has applied to the determination of caffeic acid in various food samples.     

Mn(Ⅱ)-5-Br-PADAP共沉淀-火焰原子吸收光谱法测定虾、贝样中的镉

提出了一种测量痕量重金属镉的新方法。该方法创新性地以Mn(Ⅱ)作为载体离子,以2-(5-溴-2-吡啶偶氮)-5-二乙氨基苯酚(5-Br-PADAP)作为共沉淀剂,共沉淀分离富集虾、贝样品中的镉,同时采用火焰原子吸收法进行测定。重点探讨了共沉淀剂加入量、载体离子加入量、pH值、共沉淀时间、共存离子的干扰等因素对共沉淀分离富集效果的影响, 从而确定了Mn(Ⅱ)-5-Br-PADAP共沉淀分离富集测定镉的最佳共沉淀条件。实验结果表明,当pH 7且大量干扰离子存在的条件下,Mn(Ⅱ)-5-Br-PADAP体系对镉有良好的共沉淀分离富集效果,很好地克服了基体干扰。共沉淀体系中镉含量在0.1～1.0 mg·L-1范围内时镉含量与吸光度呈线性关系。该方法的灵敏度为0.147(mg·L-1)-1,精密度为0.73%,对镉的检出限(3σ)为4.27 μg ·L-1。食品样品比较复杂,对其中痕量重金属含量的测定必须经过消化、分离富集等一系列预处理过程才能得到最准确地答案。所以通过对比直接用火焰原子吸收法与应用本方法测定样品中镉含量的区别,进一步说明了Mn(Ⅱ)-5-Br-PADAP体系对样品中重金属镉有很好的分离富集效果。根据该方法,采用标准加入法测得干贝样品中镉的含量为1.85 mg·kg-1,干虾样品中镉的含量为1.74 mg·kg-1,基本符合国际食品法典委员会的标准。为了证明该方法的可靠性与真实性,做了加标回收实验,结果显示干虾干贝样品中镉的加标回收率范围为99.9%～100.3%,相对标准偏差为0.15%～0.83%。用Mn(Ⅱ)-5-Br-PADAP共沉淀分离富集样品中的痕量镉具有重现性好、准确度高、简单快速等的优点,分析结果令人满意。     

流动注射-氢化物发生-气相化学发光法测定环境样品中的总砷

采用流动注射-氢化物发生-气相化学发光法,建立了一种快速简便测定环境样品中微量砷的新方法。土壤样品、地表水样经消解后,加入抗坏血酸和硫脲,将5价砷还原为3价后,以0.6mol/L硫酸为载液,与1.5%硼氢化钠反应,生成的胂化氢由气液分离器分离后,在反应室里与臭氧反应,产生的化学发光信号由光电倍增管检测。该法线性范围宽(1—500μg/L),检出限为0.15μg/L,相对标准偏差为0.77%(20μg/L,n=11),采样速度为50样/h。应用于环境样品中总砷的测定,结果与氢化物发生原子吸收法一致。     

催化热解-AAS测定环境水及土壤样品中的总汞

建立催化热解-AAS测定环境水及土壤样品中总汞的方法。采用DMA80型直接测汞仪测定水样及土壤中总汞含量,并采用有证标准物质验证方法的准确度、精密度。方法的线性范围为:低浓度系列0.01—0.3μg/mL,线性方程y=0.0116x+0.0012,R2=0.9997;高浓度系列0.50—4.00μg/mL,线性方程y=0.001x+0.0034,R2=0.9996,RSD为1.1%—1.3%。催化热解-AAS测定环境水及土壤样品中的总汞含量,方法简便,灵敏度高,适合环境水及土壤样品中总汞的测定。     

基于显微拉曼光谱的稀酸预处理马尾松细胞壁解构机理研究

稀酸预处理可打破木质纤维原料天然抗降解屏障,提高后续酶解和发酵效率,从而使其更高效地转化为生物燃料,然而在亚细胞水平上纤维细胞壁的解构机理仍有待深入研究。采用共聚焦显微拉曼光谱技术与主成分聚类分析法结合,研究了稀酸预处理前后马尾松细胞壁区域化学变化特点。结果表明,累计贡献率高达94.61%的第一与第二主成分空间中光谱样本散点呈现规律性分布;聚类分析可准确提取细胞壁不同形态区域平均拉曼光谱。结合拉曼成像分析发现,细胞角隅木质化程度高,含有较多木质素,次生壁木质化程度低,含有较多碳水化合物。稀酸预处理导致马尾松细胞壁发生了不均一解构,其致密空间结构被破坏,次生壁中碳水化合物典型特征峰2 890 cm-1处信号强度降低了26.9%,表明碳水化合物从该区域大量脱除;碳水化合物在复合胞间层少量脱除,而细胞角隅则出现了其轻微富集。木素在稀酸预处理后发生了重新分布,细胞角隅区拉曼信号显著增强。碳水化合物(主要为半纤维素)的溶出及木质素的重新分布削弱了生物质原料的抗降解性,有利于后续酶解糖化。该研究不仅提供了一种快速、高效的纤维细胞壁区域化学分析方法,还为林木生物质高值转化的研究奠定了重要的理论基础。     

Fabrication of diarylide yellow pigments/modified SiO2 core-shell hybrid composite particles for electrophoretic displays

Diarylide yellow pigments/modified SiO₂ core-shell hybrid composite particles were fabricated via a newly developed two-step procedure. The surface of diarylide yellow pigments was coated with SiO₂ by the hydrolysis of Na₂SiO₃. The obtained particles were then modified with in situ generated 3-aminopropylsilanetriol or succinic acid to form composite particles containing amino or carboxyl groups. The FT-IR spectra, TGA and TEM showed that the particles had a core-shell structure, the SEM suggested that the surface morphology of the composite particles was smooth, and the XPS and zeta potential measurement indicated that the composite particles had a high charge load. The obtained composite particles have been applied as electrophoretic particles in the electronic paper, which demonstrated that the newly developed procedure is an effective way to produce various organic/inorganic composite particles used for electrophoretic displays.     

ICP-AES测定青海三江源地区水中Be、Pb、Cd等对人体有害元素的含量

电感耦合等离子体发射光谱法（ICP-AES）为具有干扰水平低,精密度好,线性分析范围宽和同时多元素分析能力强的特点,已广泛应用于水质、环境、生物样品、食品、临床分析、地质样品、金属材料等的测定。本文利用ICP-AES同时测定水中的Be、Pb、Cd、Cu和Cr这5种元素,方法简便、快速,结果令人满意。     

近红外反射光谱快速测定玉米DDGS营养成分的研究

试验探讨了近红外反射光谱测定玉米DDGS的8项重要营养成分,包括水分、蛋白、粗脂肪、粗灰分、总磷、中性洗涤纤维、酸性洗涤纤维、粗纤维的可行性.从国内18个工厂采集93个玉米DDGS样品,使用偏最小二乘法,采取15种不同的导数和去散射光谱预处理方法建立近红外模型.在光谱预处理中,二阶导数产生了较好的预测效果.使用70个与...     

微波等离子体原子发射光谱分析膨润土中总砷的研究

膨润土是由比例为2∶1的Si—O四面体和Al—O八面体交替组成具有层状结构的硅酸盐天然黏土矿物,膨润土的多孔结构、化学组成、可交换离子类型以及较小的晶体尺寸,赋予了膨润土具有化学活性表面积大、阳离子交换容量大以及孔隙率高的独特性能,广泛应用于石化、冶金、食品、医药和环保等各个领域。在膨润土的开发利用过程中,其所含元素As可能通过迁移对人体健康构成潜在风险。采用硝酸-盐酸-氢氟酸对膨润土进行微波消解,加入高氯酸在电热板上对消解溶液继续进行低温消解,利用微波等离子体原子发射光谱（MP-AES）联用多模式样品引入系统（MSIS）测定膨润土中总As含量。采用25%（w/v）碘化钾为预还原溶液对As的形态进行预还原,将As（Ⅴ）还原为As（Ⅲ）,利用硼氢化钠/氢氧化钠在MSIS中将As（Ⅲ）转变为气态氢化物（AsH₃）,通过优化MP-AES的最佳观测位置和雾化气流量,获得最佳分析性能,选择188.979 nm为As的分析波长避开了谱线重叠干扰,使用快速线性干扰校正（FLIC）模型校正了背景干扰,选择261.542 nm为内标元素Lu的分析波长校正了基体效应。As的检出限（LOD）为0.41 μg·L-1,通过测定国家标准参考物质对分析方法进行评价,As的测定值与标准参考物质的认定值一致,相对标准偏差（RSD）≤2.80%,验证了方法的准确性好,精密度高。对来自中国不同产地的12个膨润土的分析显示,所有样品中总As的浓度相对较低（As的平均含量在3.51～12.6 mg·kg-1之间）,按照中华人民共和国国家标准GB 2760—2014食品安全国家标准食品添加剂膨润土中规定的总As浓度限量标准,所有膨润土样品中的As含量均没有超标。采用大气氮气为等离子体气的MP-AES降低了运行成本,提高了分析效率,为膨润土的质量控制提供了可靠的方法,具有运行安全稳定、操作简单快速、适用性强等优点。     

固载化离子液体富集-流动注射分光光度法测定废水中痕量汞

以表面浸渍固载有疏水性室温离子液体—1-己基-3-甲基咪唑六氟磷酸盐(1-hexyl-3-methylimidazolium hexafluorophosphate,[C₆mim]PF₆)的Amberlite XAD-7大孔树脂为固相萃取微柱的吸附剂,建立了微柱在线富集和流动注射-分光光度法测定废水中痕量游离态汞的新方法。在酸性介质中和十六烷基三甲基溴化铵(CTMAB)存在下,Hg2+与双硫腙反应生成红色的中性配合物可被微柱有效地定量富集。在优化的实验条件下,方法的线性范围为0.35～50 μg·L-1 Hg2+,检出限为0.067 μg·L-1 Hg2+。进样体积为50 mL时,Hg2+的富集因数为25倍。对环境水质汞标准样品(GSBZ50016-90)和加标废水样品的测定,回收率在99%～103%。     

Hydrolysis of Microcrystalline Cellulose to Produce Fermentable Monosaccharides by Plasma Acid

Plasma acid was obtained by treating distilled water with a dielectric barrier discharge (DBD) at atmospheric pressure. The tentative relationship between discharge conditions and pH value of the plasma acid was investigated. In order to optimize the hydrolysis conditions of microcrystalline cellulose with the plasma acid, an orthogonal experiment was carried out and the colorimetric determination of 3,5-dinitro-salicylic acid was applied to measure the concentration of total reduced sugar (TRS). The results showed that the pH value of the plasma acid was related to the discharge time. The acidity of the plasma acid was maintained for several hours and then faded gradually. The microcrystalline cellulose was hydrolyzed effectively by the plasma acid and the optimal hydrolysis conditions were as follows: pH 1.42 of the plasma acid, hydrolysis temperature of 80°C and hydrolysis time of 60 min. Under these conditions, the microcrystalline cellulose with polymerization degree of 200–300 was hydrolyzed completely to produce monosaccharides, including xylose and glucose with the mole ratio of 1:35, as shown by high-performance liquid chromatography (HPLC) analysis. Moreover, the hydrolysis of luffa cellulose with polymerization degree of 500–600 was also carried out. The luffa cellulose was hydrolyzed completely to produce monosaccharides including xylose, mannose and glucose with mole ratio of 6.7:1:218. Therefore, it could be concluded that the main hydrolysis product of both types of cellulose was glucose. The glucose yield of microcrystalline cellulose was 46%, whereas for luffa cellulose it was 41%. This method was an environmentally friendly and effective method to hydrolyze cellulose.     

高效液相色谱法测定食品中的富马酸二甲酯

乙酸乙酯作提取剂 ,检测波长 2 30 nm,流动相采用甲醇 -水 (4∶ 6 )的乙酸钠 -冰乙酸 -四丁基溴化铵溶液 ,高效液相色谱测定月饼、面包样品中富马酸二甲酯。优化不同性质样品的提取条件及测定的流动相。不同样品的富马酸二甲酯的回收率在 93%— 95 %之间 ,在 0— 2 5 0 .0 μg/ m L校准曲线的回归方程为 y=0 .0 0 4 5 2 x 0 .0 0 5 2 3,相关系数 r=0 .9995 ,相对标准偏差小于 1.6 %。本法简单、快速、准确 ,可用于各种食品中的富马酸二甲酯的日常检测。     

阻抑动力学分光光度法测定痕量碘

研究了在稀磷酸介质中,痕量碘离子对亚硝酸根催化溴酸钾氧化甲基红的阻抑作用,建立了测定痕量碘离子的阻抑动力学光度分析的新方法。测定碘离子的线性范围为0—35μg/50mL,检出限为7.5×10^-9g/mL。已用于食品中痕量碘的测定,结果满意。     

Synthesis of glycyrrhetinic acid by hydrolysis of licorice root extract in subcritical water

A procedure for the synthesis of glycyrrhetinic acid (glycyrrhyzic acid aglicone) by hydrolysis of licorice root extract in subcritical water was developed. The procedure was shown to be more effective than conventional hydrolysis. Glycyrrhetinic acid was identified and its concentration in the product determined by high-performance liquid chromatography. A ¹³C NMR spectroscopic study confirmed that glycyrrhetinic acid obtained in subcritical water had a β configuration at the C₁₈ atom.     

A novel strategy for producing nano-particles from date seeds and enhancing their phenolic content and antioxidant properties using ultrasound-assisted extraction: A multivariate based optimization study

Date seeds from the date palm fruit are considered as a waste and they are known to contain several bioactive compounds. Producing nanoparticles from the date seeds can enhances their effectiveness and their utilization as novel functional food ingredients. In this study, date seed nanoparticles (DSNPs) synthesized using acid (HCl) hydrolysis method (HCl concentration of 38% and hydrolysis time of 4 days) was found to have particle size between 50 and 150 nm. The obtained DSNPs were characterized by measuring particle size and particle charge (Zetasizer), morphology using scanning electron microscope (SEM), and determination of the functional groups using fourier-transform infrared spectroscopy (FTIR). DSNPs were further treated with green extraction technology [ultrasound-assisted extraction (UAE)] using water-based and methanol-based solvent for optimizing the extraction of the bioactive compounds by implementing response surface methodology (RSM). The UAE of DSNPs were analysed for set of responses including total phenolic content (TPC), total flavonoid content (TFC), 1,1-diphenyl-2-picrlthydrazyl (DPPH) radical scavenging activity, ferric ion reducing antioxidant power (FRAP), and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity. Three-factor and four-factor Box-Behnken design (BBD) of three models (Synthesis of DSNPs, UAE with water, and UAE with methanol) was performed. The results showed that in UAE of DSNPs using water-based solvent, the key independent factors effecting the TPC and TFC and antioxidant activities were S:L ratio (40:1 mg/ml) and treatment time (9 min). Whereas the methanol-based UAE of DSNPs was mostly affected by US amplitude/power (90%) and methanol concentration (80%). All models were further optimized using response optimizer in Minitab and the generated predicted values were very comparable to the actual obtained results which confirm the significance and validity of all RSM models used. The phenolic compounds identified from DSNPs consisted mainly of 3,4-Dihydroxy benzoic acid, ferulic acid, and p-coumaric acid. The present study demonstrated a successful method for synthesising DSNPs as well as documented the optimum UAE conditions to maximize the extraction of polyphenolic compounds from DSNPs and enhancing their antioxidant activities to be used in food application.     

石墨炉原子吸收光谱法测定海藻制品中的砷

应用石墨炉原子吸收光谱技术建立了在海藻制品中测定总砷和三价无机砷的方法,为开展海藻制品中无机砷的监测和食品安全风险评估提供准确的检测方法。采用湿法消解和微波消解为测定总砷的前处理方式,9m ol/L盐酸浸泡后乙酸丁酯萃取和纯水反萃取作为海藻制品中三价无机砷的提取方式,分别利用塞曼扣背景和氘灯扣背景的石墨炉原子吸收光谱法测定总砷和三价无机砷。塞曼扣背景测定砷的线性范围为3.0—60μg/L,定量限(LOQ)为2.9μg/L,精密度为3.6%,回收率为90%—102%;氘灯扣背景测定砷的线性范围为4.0—80μg/L,定量限(LOQ)为3.6μg/L,精密度为4.1%,回收率为88%—109%。本法对三价无机砷的提取方法简便实用、提取效率高。原子吸收光谱法的两种背景校正方式测定总砷及三价无机砷的结果准确可靠。为基层实验室开展食品中总砷以及三价无机砷的测定提供实用、可靠的分析方法。     

火焰原子吸收法间接测定混凝土外加剂中的微量Cl-

火焰原子吸收法以其灵敏度高、选择性好等优点而广泛应用于各种基体中微量金属元素的测定 ,而不用于直接测定Cl- 。本文提出了采用火焰原子吸收法间接测定混凝土外加剂中微量Cl- 的方法 ,在待测液中加入过量的Ag 标液 ,通过测定与Cl- 定量反应后剩余的Ag 量从而换算出Cl- 的含量 ,本法进行了测定最佳酸度试验、精密度试验、在样品中加入Cl- 标准溶液回收试验 ,回收率为 96 %～ 10 4 %。经过实际样品测定 ,证明该方法具有样品预处理手续简单、测定周期短、干扰小等优点 ,最适合于测定基体较为复杂的混凝土外加剂中的微量Cl- 。称取样品 0 0 5～ 2g ,溶解后 ,用硝酸调节酸度 ,加入与之对应的Ag 标准溶液 ,放置 2h过滤后即可测定 ,所用仪器为澳大利亚GBC90 2型原子吸收光谱仪。     

Sensitive Determination of Carbohydrates by Fluorimetric Method with Ce(IV) and Sodium Triphosphate

A new simple and sensitive fluorimetric method for the determination of carbohydrates is described. The method is based on the reaction between carbohydrates and Ce(IV) in the presence of sulfuric acid. All the reductive carbohydrates can be detected indirectly by the fluorescence of Ce(III) produced. The addition of sodium triphate enhances the sensitivity of the method by more than 10-folds. Under optimum conditions, an excellent linear relationship was obtained between the fluorescence intensity and the concentration of carbohydrates. The limits of detection lie in the range of 9.3 x 10(-10) - 1.3 x 10(-9) mol/L. As compared to the normal fluorimetric method, the proposed method is faster and more sensitive.     

环境样品中痕量铝的现代光度分析研究新进展

论文综述和评论了近年来环境样品中痕量铝的光度分析研究新进展。重点论述了现代光度分析法测定环境样品中铝的研究新进展 ,内容包括 :胶束增溶分光光度法、双波长分光光度法、导数分光光度法、催化光度法、固相光度法、流动注射光度法。对普通光度法和胶束增溶光度法的反应体系、测定条件、摩尔吸收系数 (ε)或检出限、线性范围及其应用进行了归纳总结 ,评述了各种光度法测定的优劣 ,展望了光度法测定痕量铝的发展前景