分散固相萃取结合超高效液相色谱-串联高分辨质谱法快速测定羊乳中磺胺类药物

目的 建立基于多孔石墨烯复合多壁碳纳米管纳米材料(MWCNTs@PG)的分散固相萃取结合超高效液相色谱串联高分辨质谱的羊乳中10种磺胺类药物快速分析方法。方法 样品经QuEChERS处理,分散固相萃取后采用C₁₈色谱柱分离,正离子模式下高分辨数据依赖采集。研究了吸附剂种类、pH、洗脱溶剂种类、吸附剂用量、洗脱溶剂体积、吸附时间对磺胺提取效率与检测准确性的影响。结果 10种磺胺物质在各自的线性范围相关系数均大于0.99,检出限为0.01~0.25 μg/kg,回收率和精密度分别为75%~109%和0.6%~9.3%。结论 基于MWCNTs@PG分散固相萃取对羊乳中磺胺药物有较高的回收率和净化效果,超高效液相色谱串联高分辨质谱可实现快速分离、准确定性和精准定量,适合于复杂基质中兽药残留的快速准确分析。     

Qu ECHERS-LC-MS/MS法测定牛奶中喹诺酮类药物

建立分散固相萃取-超高效液相色谱串联质谱同时测定牛奶中12种喹诺酮类药物残留的方法。牛奶样品中喹诺酮类药物经酸化乙腈提取,分散固相萃取净化,电喷雾离子源-三重四级杆串联质谱对喹诺酮类药物进行测定。12种喹诺酮类药物在5～200 ng/mL质量浓度范围内,其回归标准曲线方程的相关系数r为0.996 4～0.999 9。对空白牛奶添加5, 20和50μg/kg 3种浓度的喹诺酮类标准品,回收率为78.7%～96.3%,相对标准偏差(n=6)为1.99%～10.09%,方法检出限在1μg/kg以下。使用该方法对唐山本地牛奶样品进行检测,未发现有喹诺酮类药物检出。     

微柱固相萃取结合气相色谱-质谱法分析茶叶中有机氯农药

研制了碳纳米管微柱,建立了测定有机氯类农药的微柱固相萃取气相色谱-质谱法。样品泵入多壁碳纳米管微柱,8种有机氯类农药吸附保留到微柱,引入甲醇洗脱,气质联用选择离子监测方式检测洗脱液中有机氯类农药。考察了影响微柱固相萃取有机氯类农药的各种因素,包括样品流速、样品体积、洗脱剂种类、洗脱剂体积和碳纳米用量等。建立的方法适用于茶叶水提液中8种有机氯类农药分析,检出限0.015～0.25μg/kg。加标样品回收率74.5%～107.2%,相对标准偏差小于12%。     

基质固相分散-液相色谱法测定柑桔中唑螨酯残留

为优化唑螨酯在柑桔中残留分析方法,采用基质固相分散萃取、HPLC检测,结果表明:柑桔样品中唑螨酯适于基质固相分散萃取,以氧化铝作为分散剂,乙酸乙酯为洗脱剂,淋出液过氧化铝柱净化后HPLC测定,最低检出浓度为0.0625mg/kg,当桔皮、桔肉样品中添加浓度为0.1～1.0mg/kg时,方法的回收率在81.9%～96.3%之间,相对标准偏差为3.73%～7.54%,满足残留分析的要求。     

多壁碳纳米管分散固相萃取结合LC-MS-MS测定鸡肉中金刚烷胺

建立了采用多壁碳纳米管为吸附剂的分散固相萃取净化、液相色谱串联质谱测定鸡肉中金刚烷胺残留量的方法。鸡肉样品经乙酸乙腈提取后,调节pH值至11,加入75 mg多壁碳纳米管进行分散固相萃取,被吸附的药物经5.0%甲酸溶液:甲醇(5∶5,V/V)洗脱,洗脱液过滤膜后直接进样分析。采用Acquity UPLC BEH C18色谱柱分离,以0.1%甲酸水溶液和甲醇作为流动相作梯度洗脱,电喷雾正电子(ESI+)模式电离,多反应监测模式检测,内标法校准进行定量。金刚烷胺在0.05~5.0μg/L质量浓度范围内呈良好的线性,线性相关系数均大于0.99,鸡肉样品中最低定量限为0.50μg/kg。鸡肉样品中添加0.5~1.0μg/kg金刚烷胺的回收率在97.8%~103.6%之间,相对标准偏差均小于10%。     

分散固相萃取-液相色谱串联质谱法快速测定牛奶中利福昔明残留量

目的建立分散固相萃取-液相色谱串联质谱法快速测定牛奶中利福昔明残留的分析方法。方法牛奶样品用乙腈提取,提取液采用分散固相萃取(dispersive solid phase extraction,DSPE)净化,采用超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandem mass spectrometry, UPLC-MS/MS)在多反应正离子监测模式下进行监测。以离子对m/z 786.3/151.0进行定性分析、m/z 786.3/754.4进行基质校准外标法定量分析。结果方法的检出限(limit of detection, LOD)和定量限(limit of quantitation, LOQ)分别为0.2μg/kg和0.6μg/kg。方法基质标准曲线线性方程为Y=159.27X+8.25, r~2=0.9998, 4个浓度水平加标回收率在77.1%～102%之间,批内相对标准偏差为2.4%～7.1%,批间相对标准偏差为3.9%～6.2%。结论方法简便、快速、准确,可用于牛奶样品中利福昔明的药物残留快速确证检测分析。     

多壁碳纳米管分散固相萃取净化在测定水产品中3 种微囊藻毒素的应用及与固相萃取法的比较

建立多壁碳纳米管净化-超高效液相色谱-串联质谱法对水产品中3?种微囊藻毒素残留量的测定方法。水产品用80%甲醇溶液提取,经多壁碳纳米管净化后,采用电喷雾正离子多反应监测模式进行分析。对不同性质碳纳米管进行考察,并对净化条件进行优化。将优化后的分散固相萃取条件与采用HLB柱固相萃取的净化方式进行比较,两者在1～50?μg/L范围内呈现良好的线性,线性相关系数均大于0.99,3?种微囊藻毒素的检出限为0.1～0.2?μg/kg。在不同浓度水平下进行加标实验,平均回收率在88.7%～95.5%之间,相对标准偏差不大于4.2%。该方法适用于水产品中微囊藻毒素的痕量检测。     

脂质去除分散固相萃取-气相色谱-串联质谱测定鸡蛋中62 种农药残留

采用脂质去除分散固相萃取进行前处理建立鸡蛋中62 种农药残留筛查的气相色谱-串联质谱（gas chromatography-tandem mass spectrometry,GC-MS/MS）检测方法。经过条件优化后,样品用10 mL 1%乙酸-乙腈和5 mL水提取,提取液经氯化钠盐析后取有机相,最后将有机相转移至增强型脂质去除（EMR-Lipid）分散固相萃取净化管中净化并高速离心,GC-MS/MS测定,外标法定量。62 种农药在5～400 μg/L范围之间线性关系良好,相关系数（R）在0.95以上,其中59 种农药的检出限为0.5～5.0 μg/kg,定量限为1.0～20.0 μg/kg。鸡蛋中62 种农药使用EMR-Lipid分散固相萃取净化管去除脂质后的回收率和重复性结果都优于直接经过固相萃取净化管的结果,添加量为100 μg/kg时,98.4%的农药平均加标回收率为70.7%～117.2%,相对标准偏差为0.3%～10.9%。基质效应研究表明,62 种农药中仅20 种农药为弱基质效应,检测结果均需要通过基质标准溶液进行校正。该方法成功应用于实际样品分析。     

固相萃取-气相色谱串联质谱法检测牛奶中41种农药残留

目的 建立固相萃取-气相色谱串联质谱法（SPE-GC-MS/MS）同时测定牛奶中41种农药残留分析方法。方法 采用固相萃取方法对样品进行前处理。样品经乙腈提取、盐析后,提取液经Captiva EMR-Lipid固相萃取柱净化后上机测定。用气相色谱-三重四极杆串联质谱仪进行多农残检测。结果 41种农药在50～1000 ng/ml之间呈良好的线性关系,相关系数r均大于0.99。在0.02,0.1,0.2 mg/kg加标水平下,41种农药的平均回收率为60.6%～110.6%,相对标准偏差（RSD）为1.3%～16.6%(n=6)。结论 该方法选择性好,操作简单安全,快速准确,适用于牛奶中多种农药残留的测定。     

分散固相萃取净化离子色谱-串联质谱测定茶叶中高氯酸盐

目的 建立分散固相萃取净化离子色谱-串联质谱法测定茶叶中高氯酸盐的含量。方法 样品经80 ℃超纯水浸泡提取30 min, 定性滤纸过滤, 滤液采用分散固相萃取技术, 以多壁碳纳米管和N-丙基乙二胺键合固相吸附剂吸附提取液中的杂质, 待测样品由离子色谱-串联质谱法测定, 内标法定量。结果 高氯酸盐浓度0.02~10.00 μg/L有良好的线性关系, 相关系数r2为0.9998, 检出限为0.6 μg/kg, 定量限为2.0 μg/kg, 加标回收率为80.1%~99.2%, 相对标准偏差为3.89%~7.68% (n=6)。对市场上随机购买的茶叶样品进行测定, 样品的含量为0.15~0.72 mg/kg。结论 该方法简便、可靠、稳定、灵敏度高, 可用于茶叶中高氯酸盐快速检测。     

Determination of Six Paraben Residues in Fresh-cut Vegetables Using QuEChERS with Multi-walled Carbon Nanotubes and High-Performance Liquid Chromatography–Tandem Mass Spectrometry

In this study, an optimized QuEChERS sample preparation method was developed to analyze residues of six parabens: methyl-, ethyl-, n-propyl-, isopropyl-, n-butyl-, and isobutylparaben in five fresh-cut vegetables (potato, broccoli, carrot, celery, and cabbage) with high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Homogenized samples were extracted using acetonitrile, and the extracts were cleaned with the novel sorbent multi-walled carbon nanotubes (MWCNTs). MWCNTs provided 84–94% removal of chlorophyll and lower matrix effects (MEs) compared to commonly used primary-secondary-amine (PSA) sorbent. Selected parabens were separated by HPLC with isocratic elution using acetonitrile and 0.1% (v/v) formic acid solution and determined by triple quadrupole MS/MS. The method validation results showed that recoveries were at 70–120% with RSDs <20%. Calibration curves showed linear responses of six parabens with R ² > 0.99. Fifty fresh-cut vegetable samples from different farmer markets in Beijing, China were collected to measure the paraben residues, and only one sample was tested positive with methylparaben concentration at 81 μg/kg.     

纤维素基柔性压力传感器及其性能表征

利用3-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)对多壁碳纳米管(MWCNTs)进行改性,通过水浴成型制备形状可逆的纤维素/MWCNTs空间导电网络并用作柔性压力传感器;利用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)、X射线衍射仪(XRD)对压力传感器的性能进行表征,探讨了MPS改性MWCNTs的结合牢度及该压力传感器的力学性能和灵敏度。结果表明,MPS改性MWCNTs可均匀分散在纤维素基材表面,使得传感器结构中羟基和C—H单元增多,但对基材的结晶结构影响不显著;含10 wt%MPS改性MWCNTs的压力传感器经20次洗涤后的电阻值较洗涤前仅提高了7.7%,导电性能略微降低;当应变量为55%、MPS改性MWCNTs含量由1 wt%增至10 wt%时,压力传感器所需应力提高了180.3%,达87.2 kPa;压力传感器的灵敏度总体随着MPS改性MWCNTs含量的增加而提高,当MPS改性MWCNTs含量为10 wt%时,外界压强从0提高至30 kPa会使压力传感器电阻值降低63.2%。     

基于ZIF-8@Ag/MWCNTs的绿原酸电化学传感器的构建及应用

构建了用于定量分析绿原酸的ZIF-8@Ag/MWCNTs电化学传感器。Ag纳米粒子具有良好的导电性和电催化能力,而ZIF-8优秀的比表面积能有效的分散Ag纳米粒子,因此在室温合成ZIF-8后,在ZIF-8表面原位还原Ag+制备ZIF-8@Ag复合材料。然后,以MWCNTs作为基底材料,复合ZIF-8@Ag获得修饰工作电极,获得高灵敏度的电化学传感器用于绿原酸的测定。通过循环伏安法（CV）、电化学阻抗谱（EIS）和差分脉冲伏安法（DPV）,探讨了ZIF-8@Ag/MWCNTs/GCE的电化学传感性能。在优化的实验条件下,绿原酸标准品浓度在5×10-8 mol/L~1×10-5 mol/L范围内与氧化峰电流具有良好的线性关系,检出限为1.36×10-8 mol/L（S/N=3）。探究了修饰电极的抗干扰性、重复性和再现性,结果表明电极抗干扰能力较强,重复性及再现性表现良好。用于实际样品绿咖啡豆稀释液的检测时,加标回收率在96.34%~103.34%。该方法简便、可靠,可用于绿原酸及绿原酸实际样品的快速定量分析。     

Electrochemical detection of carbamate pesticides in fruit and vegetables with a biosensor based on acetylcholinesterase immobilised on a composite of polyaniline-carbon nanotubes

A sensitive electrochemical acetylcholinesterase (AChE) biosensor was successfully developed on polyaniline (PANI) and multi-walled carbon nanotubes (MWCNTs) core-shell modified glassy carbon electrode (GC), and used to detect carbamate pesticides in fruit and vegetables (apple, broccoli and cabbage). The pesticide biosensors were applied in the detection of carbaryl and methomyl pesticides in food samples using chronoamperometry (CA). The GC/MWCNT/PANI/AChE biosensor exhibited detection limits of 1.4 and 0.95μmolL(-1), respectively, for carbaryl and methomyl. These detection limits were below the allowable concentrations set by Brazilian regulation standards for the samples in which these pesticides were analysed. Reproducibility and repeatability values of 2.6% and 3.2%, respectively, were obtained in the conventional procedure. The proposed biosensor was successfully applied in the determination of carbamate pesticides in cabbage, broccoli and apple samples without any spiking procedure. The obtained results were in full agreement with those from the HPLC procedure.     

Rapid analysis of phthalates in beverage and alcoholic samples by multi-walled carbon nanotubes/silica reinforced hollow fibre-solid phase microextraction

A novel procedure based on multi-walled carbon nanotubes (MWCNTs)/silica reinforced hollow fibre solid-phase microextraction combined with gas chromatography–mass spectrometry has been developed to analyse trace phthalate acid esters in beverage and alcoholic samples. Because of their excellent adsorption capability towards hydrophobic compounds, functionalized MWCNTs, acting as solid-phase sorbent, were co-deposited with silica particles in the pores of polypropylene hollow fibre through a layer-by-layer self-assembly technique. The parameters influencing the extraction efficiency, such as pH values and ionic strength of sample solution, extraction time, temperature and desorption solvent were optimised. Recoveries for phthalates at spiking levels in different matrices were satisfactory (between 68% and 115%). Moreover, the results were further confirmed by comparing them with those obtained using a solvent extraction method according to the national standard of China.     

Optimized method for simultaneous determination of catechin, gallic acid, and methylxanthine compounds in chocolate using RP-HPLC

The simultaneous determination of catechins, gallic acid, and three methylxanthine compounds was determined in chocolate extract by reversed-phase HPLC. An isocratic HPLC procedure using Hypersil-ODS column with methanol three distilled water-formic acid (48.75:200.5:0.75, v/v/v) as a mobile phase was used and the HPLC profiles of 11 chocolate products were obtained. (-)- Epicatechin, (-)-epigallocatechin gallate, levels were very high whereas (+)-catechin, (-)-epigallocatechin and (-)-epicatechin gallate were lower values. Gallic acid was predominant compounds with extremely high levels in all chocolate samples. The content of three methylxanthine, theobromine, theophylline and caffeine was quantified with this procedure. Caffein amounts were low in all samples, while theobromine levels were high in milk and dark chocolates. Theophylline was at trace levels in some chocolates and could not be detected in some samples. This method was reliable, reproducible and objective for quantitative identification of flavanols and alkaloid compounds in the chocolate industry.     

Molecular Analysis of the Polymeric Glutenins with Gliadin‐Like Characteristics That Were Produced by Acid Dispersion of Wheat Gluten

We had earlier shown that the dispersion of wheat gluten in acetic acid solution conferred gliadin‐like characteristics to the polymeric glutenins. To elucidate the molecular behavior of its polymeric glutenins, the characteristics of gluten powder prepared from dispersions with various types of acid were investigated in this study. Mixograph measurements showed that the acid‐treated gluten powders, regardless of the type of acid, had dough properties markedly weakened in both resistance and elasticity properties, as though gliadin was supplemented. The polymeric glutenins extracted with 70% ethanol increased greatly in all acid‐treated gluten powders. Size exclusion HPLC and SDS‐PAGE indicated that the behavior of polymeric glutenins due to acid treatment was attributed to their subunit composition rich in high molecular weight glutenin subunit (HMW‐GS) and not their molecular size. The gluten prepared with the addition of NaCl in acid dispersion had properties similar to those of the control gluten. The results suggest that ionic repulsion induced by acid dispersion made the polymeric glutenins rich in HMW‐GS disaggregate, and therefore, act like gliadins.     

Electrochemical Determination of Vitamin B-12 in Food Samples by Poly(2,2′-(1,4-phenylenedivinylene) Bis-8 hydroxyquinaldine)/Multi-Walled Carbon Nanotube-Modified Glassy Carbon Electrode

Poly(2,2′-(1,4-phenylenedivinylene) bis-8-hydroxyquinaldine)/multi-walled carbon nanotube-modified glassy carbon electrode (poly(PBHQ)/MWCNTs/GCE) was developed and applied for the electrochemical estimation of vitamin B-12 (VB-12). Compared to multi-walled carbon nanotube-modified glassy carbon electrode, well-defined redox peaks were observed in phosphate buffer solution at pH 2.5. In contrast with the ill-defined redox peaks observed with unmodified glassy carbon electrode surfaces. The poly(2,2′-(1,4-phenylenedivinylene) bis-8-hydroxyquinaldine-based electrode displayed a good linear range of 0.1 to 10 μM VB-12 with a low detection limit of 0.01 μM. To further study the practical applicability of the proposed sensing procedure, the estimation of real samples was employed with satisfactory consequences. In addition, MWCNTs were used as sorbent for solid phase extraction (SPE) of vitamin B-12 from cereal food samples. Solid phase extraction parameters, such as the amount of MWCNTs, sample volume, pH, and type and amount of the eluent, were optimized.     

柱前衍生化高效液相色谱法测定生物样本中短链脂肪酸及乳酸含量

建立一种适用于同时测定肠内容物、血清等生物样品中短链脂肪酸（short-chain fatty acids，SCFAs）及乳酸含量的方法。使用气相色谱法、高效液相色谱法、柱前衍生化高效液相色谱法检测小鼠粪便中SCFAs及乳酸含量并进行对比分析；对建立的柱前衍生化高效液相色谱法进行方法学评价，并将其应用于肠内容物、血清等生物样品的分析。结果表明：气相色谱法可快速检测乙酸、丙酸、丁酸、戊酸，但不能同时检测乳酸；高效液相色谱法杂峰多，检测乙酸含量误差大，准确度不高；柱前衍生化高效液相色谱法检测范围广，可同时检测肠内容物与血清中乳酸及5 种SCFAs的含量，样品色谱图杂峰少，各组分分离度高，方法准确度高，各组分测定的变异系数均不高于8.87%。在同时检测肠内容物与血清等生物样品中SCFAs及乳酸含量方面，相比于气相色谱法和高效液相色谱法，柱前衍生化高效液相色谱法更具技术优势，更能有效满足当前迅猛发展的微生物组学、代谢组学的复杂样品中对SCFAs及乳酸含量准确分析的应用需求。