SPME/GC-MS鉴别沉香真伪方法研究

采用固相微萃取/气相色谱-质谱联用(SPME/GC-MS)对沉香的成分进行研究,建立以特征成分鉴别沉香真伪的方法。通过SPME富集沉香的气味成分,GC-MS测定其化学组成,确定天然沉香的6种特征成分,并通过面积归一化确定特征成分在气味成分中的相对含量;通过沉香样品中气味成分的种类及其相对含量与天然沉香特征成分对比,判断沉香的真伪。SPME/GC-MS法具有样品用量小、操作简便快速、检测灵敏度高、特征性强、结果准确可靠的特点,适用于沉香气味成分的分析及真伪鉴别,且不破坏沉香收藏品的整体结构,已成功用于沉香药材及其工艺品等的真伪鉴别。     

固相萃取-气相色谱法检测血清中有机氯农药残留的研究

建立了血清中DDTs和BHCs共8种有机氯农药残留的固相萃取-气相色谱检测方法。样品经超声酸化沉淀蛋白后,采用正己烷-丙酮(9∶1)经Cleanert ODS C18N固相萃取小柱提取,Florisil固相萃取小柱净化,氮气吹干,以500μL正己烷定容,气相色谱-电子捕获检测器(GC-ECD)进行定量分析。结果表明,方法的线性范围2~200 ng/m L,相关系数(r)为0.996 4~0.999 0,检出限(LOD)为0.1~0.9 ng/m L,定量下限(LOQ)为0.4~3.0 ng/m L。8种农药的回收率为80.5%~112.7%,相对标准偏差(RSD)为2.1%~7.9%。该方法具有较高的准确度和精密度,适用于血清样品中痕量有机氯农药的检测。     

盘式固相萃取–超高效液相色谱–串联质谱法快速测定环境水样中3种微囊藻毒素

建立盘式固相萃取–超高效液相色谱–串联质谱(UPLC–MS–MS)快速测定环境水样中3种微囊藻毒素(MCs)的方法。环境水样经过盘式固相萃取柱净化,采用Waters BEH C_(18)色谱小柱,以乙腈–0.2%甲酸水溶液为流动相,梯度洗脱分离后,UPLC–MS–MS多级监测正离子模式下外标法进行定性定量分析。3种微囊藻毒素在0.05~10.0μg/L范围内呈现良好线性关系,相关系数均大于0.999 4,方法检出限为0.02 ng/L。对同一环境样品进行0.1,1.0,5.0μg/L 3种浓度的加标回收试验,平均回收率为82.8%~108.8%,测定结果的相对标准偏差为2.1%~10.1%(n=6)。该方法快速、灵敏、准确,可有效应用于环境水样中微囊藻毒素的监测。     

Determination of aromatic amines in environmental water samples using solid-phase extraction modified with sodium dodecyl sulphate and micellar liquid chromatography

Extraction and determination of seven aromatic amines in environmental water samples were performed with solid-phase extraction (SPE) and micellar liquid chromatography (MLC) using experimental design. Extraction of aromatic amines was carried out with a C₁₈ cartridge modified with sodium dodecyl sulphate (SDS). The washing solution and elution solvent for extraction of aromatic amines were aqueous solution containing 5% (v/v) acetonitrile and 5% (v/v) acetone and 3 mL methanol, respectively. The chemometrics approach was applied for the separation optimisation of these compounds using MLC. Different mobile phase compositions were used for modelling based on retention times to obtain the best separation using central composite design. The optimum mobile phase composition for separation and determination of analytes in water samples was 69 mM SDS, 9% v/v 1-propanol and pH = 6.4. Recoveries were between 84.8–93.5% with relative standard deviation (RSD) less than 5.8% (n = 5). Limits of detection and linear range were 1–4.5 and 3.1–125.0 µg/L, respectively. The proposed method was applied to determine the aromatic amines in real samples (river and well waters). Amount of 4-nitroaniline and 3-nitroaniline in river water sample were 2.15 and 1.91 µg/L, respectively.     

Multi-wall carbon nanotubes chemically modified silica microcolumn preconcentration/separation combined with inductively coupled plasma optical emission spectrometry for the determination of trace elements in environmental waters

A novel adsorbent of multi-wall carbon nanotubes (MWCNTs) chemically modified silica (MWCNTs-silica) was synthesised and employed as the adsorbent material for solid-phase extraction (SPE) of trace Zn(II), Cu(II), Cd(II), Cr(III), V(V) and As(V) in environmental water samples followed by inductively coupled plasma optical emission spectrometry detection. This material inherits the advantages of nanomaterial MWCNTs and conventional silica with dual functional groups (–NH₂ and –COOH), and avoid the problem of nanomaterial in SPE, such as high pressure. The factors affecting the separation and preconcentration of target elements such as pH, sample flow rate and volume, eluent concentration and volume were investigated. Under the optimised conditions, the detection limits for Zn(II), Cu(II), Cd(II), Cr(III), V(V) and As(V) were 0.27, 0.11, 0.45, 0.91, 0.55 and 0.67 μg L^?1 with the relative standard deviations of 3.1, 5.9, 4.1, 4.0, 7.3 and 8.6% (c = 10 μg L^?1, n = 7), respectively. The adsorption capacity of MWCNTs-silica was 26.6, 70.0, 13.8, 58.0, 20.0 and 20.0 mg g^?1 for Zn(II), Cu(II), Cd(II), Cr(III), V(V) and As(V), respectively, and the prepared adsorbent could be reused more than 100 times. In order to validate the developed method, two certified reference materials of GSBZ50009-88 and GSBZ 50029-94 environmental waters were analysed and the determined values were in good agreement with the certified values. The developed method has been applied to the determination of trace elements in environmental water samples with satisfactory results.     

A One‐Pot Chemically Cleavable Bis‐Linker Tether Strategy for the Synthesis of Heterodimeric Peptides

Heterodimeric peptides linked by disulfide bonds are attractive drug targets. However, their chemical assembly can be tedious, time‐consuming, and low yielding. Inspired by the cellular synthesis of pro‐insulin in which the two constituent peptide chains are expressed as a single‐chain precursor separated by a connecting C‐peptide, we have developed a novel chemically cleavable bis‐linker tether which allows the convenient assembly of two peptide chains as a single “pro”‐peptide on the same solid support. Following the peptide cleavage and post‐synthetic modifications, this bis‐linker tether can be removed in one‐step by chemical means. This method was used to synthesize a drug delivery‐cargo conjugate, TAT‐PKCi peptide, and a two‐disulfide bridged heterodimeric peptide, thionin (7‐19)‐(24‐32R), a thionin analogue. To our knowledge, this is the first report of a one‐pot chemically cleavable bis‐linker strategy for the facile synthesis of cross‐bridged two‐chain peptides.     

Site‐Targeted Interfacial Solid‐Phase Chemistry: Surface Functionalization of Organic Monolayers via Chemical Transformations Locally Induced at the Boundary between Two Solids

Effective control of chemistry at interfaces is of fundamental importance for the advancement of methods of surface functionalization and patterning that are at the basis of many scientific and technological applications. A conceptually new type of interfacial chemical transformations has been discovered, confined to the contact surface between two solid materials, which may be induced by exposure to X‐rays, electrons or UV light, or by the application of electrical bias. One of the reacting solids is a removable thin film coating that acts as a reagent/catalyst in the chemical modification of the solid surface on which it is applied. Given the diversity of thin film coatings that may be used as solid reagents/catalysts and the lateral confinement options provided by the use of irradiation masks, conductive AFM probes or stamps, and electron beams in such solid‐phase reactions, this approach is suitable for precise targeting of different desired chemical modifications to predefined surface sites spanning the macro‐ to nanoscale.     

Coding in 2D: Using Intentional Dispersity to Enhance the Information Capacity of Sequence‐Coded Polymer Barcodes

A 2D approach was studied for the design of polymer‐based molecular barcodes. Uniform oligo(alkoxyamine amide)s, containing a monomer‐coded binary message, were synthesized by orthogonal solid‐phase chemistry. Sets of oligomers with different chain‐lengths were prepared. The physical mixture of these uniform oligomers leads to an intentional dispersity (1st dimension fingerprint), which is measured by electrospray mass spectrometry. Furthermore, the monomer sequence of each component of the mass distribution can be analyzed by tandem mass spectrometry (2nd dimension sequencing). By summing the sequence information of all components, a binary message can be read. A 4‐bytes extended ASCII‐coded message was written on a set of six uniform oligomers. Alternatively, a 3‐bytes sequence was written on a set of five oligomers. In both cases, the coded binary information was recovered.     

Total Chemical Synthesis of an Intra‐A‐Chain Cystathionine Human Insulin Analogue with Enhanced Thermal Stability

Despite recent advances in the treatment of diabetes mellitus, storage of insulin formulations at 4 °C is still necessary to minimize chemical degradation. This is problematic in tropical regions where reliable refrigeration is not ubiquitous. Some degradation byproducts are caused by disulfide shuffling of cystine that leads to covalently bonded oligomers. Consequently we examined the utility of the non‐reducible cystine isostere, cystathionine, within the A‐chain. Reported herein is an efficient method for forming this mimic using simple monomeric building blocks. The intra‐A‐chain cystathionine insulin analogue was obtained in good overall yield, chemically characterized and demonstrated to possess native binding affinity for the insulin receptor isoform B. It was also shown to possess significantly enhanced thermal stability indicating potential application to next‐generation insulin analogues.     

Optimization of ultrasound-assisted dispersive solid-phase microextraction based on nanoparticles followed by spectrophotometry for the simultaneous determination of dyes using experimental design

A simple, low cost and ultrasensitive method for the simultaneous preconcentration and determination of trace amount of auramine-O and malachite green in aqueous media following accumulation on novel and lower toxicity nanomaterials by ultrasound-assisted dispersive solid phase micro-extraction (UA-DSPME) procedure combined with spectrophotometric has been described. The Mn doped ZnS nanoparticles loaded on activated carbon were characterized by Field emission scanning electron microscopy (FE-SEM), particle size distribution, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analyses and subsequently were used as green and efficient material for dyes accumulation. Contribution of experimental variables such as ultrasonic time, ultrasonic temperature, adsorbent mass, vortex time, ionic strength, pH and elution volume were optimized through experimental design, and while the preconcentrated analytes were efficiently eluted by acetone. Preliminary Plackett–Burman design was applied for selection of most significant factors and giving useful information about their main and interaction part of significant variables like ultrasonic time, adsorbent mass, elution volume and pH were obtained by central composite design combined with response surface analysis and optimum experimental conditions was set at pH of 8.0, 1.2 mg of adsorbent, 150 μL eluent and 3.7 min sonication. Under optimized conditions, the average recoveries (five replicates) for two dyes (spiked at 500.0 ng mL⁻¹) changes in the range of 92.80–97.70% with acceptable RSD% less than 4.0% over a linear range of 3.0–5000.0 ng mL⁻¹ for the AO and MG in water samples with regression coefficients (R²) of 0.9975 and 0.9977, respectively. Acceptable limits of detection of 0.91 and 0.61 ng mL⁻¹ for AO and MG, respectively and high accuracy and repeatability are unique advantages of present method to improve the figures of merit for their accurate determination at trace level in complicated materials.