顶空固相微萃取气相色谱法测定浓海水中的氯酚

建立浓海水中氯酚的顶空固相微萃取气相色谱法检测方法。采用顶空固相微萃取对海水淡化排放的浓海水样品中2,4,6-三氯酚(2,4,6-TCP)和五氯酚(PCP)进行分离富集,气相色谱-电子捕获检测器(μECD)测定浓海水样品中2,4,6-TCP和PCP的含量。讨论了萃取时间、萃取温度、水样盐度等实验条件对富集效率的影响,确定了萃取时间为40 min,萃取温度为60℃。2,4,6-TCP,PCP的质量浓度在0.500~20.0μg/L范围内与其色谱峰面积呈良好的线性关系,线性相关系数均大于0.999,2,4,6-TCP和PCP的检出限(2S/N)分别为0.055,0.128μg/L,测定结果的相对标准偏差为3.65%~11.4%(n=6),加标回收率为73.5%~119.0%。该方法快速,灵敏度高,适合于浓海水中氯酚的分析。     

固相微萃取气相色谱法测定饮料中山梨酸和苯甲酸

采用溶胶凝胶聚甲基苯基乙烯基硅氧烷萃取头萃取饮料中山梨酸和苯甲酸,用直接固相微萃取与气相色谱联用进行测定,通过试验确定了萃取时间、酸度等萃取条件。山梨酸和苯甲酸的浓度在0.2～40μg/mL范围内与色谱峰面积呈良好的线性关系,相关系数分别为0.9988,0.9989,检出限分别为0.0332,0.00320μg/mL,饮料样品和加标样品测定结果的相对标准偏差为4.18%～7.03%(n=3),两个添加水平的加标回收率为80.5%～96.5%。该方法灵敏度比传统的液–液萃取气相色谱法高。     

自制丙烯酸酯类共聚物固相微萃取/气相色谱对水中农药残留的分析

合成了一种丙烯酸酯类共聚物并将其作为固相微萃取涂层,使用微量进样器自制了固相微萃取装置,并用该装置萃取分析了水体中4种农药（异稻瘟净、乙草胺、赤死蜱、除草醚）,对影响分析灵敏度的各种实验因素进行了优化。在优化条件下4种农药标准样品质量浓度在1～1000μg/L内与色谱峰面积呈良好的线性关系（r=0．992～0．997）,检出限为7．62～13．96ng／L。结果表明,自制的固相微萃取头对水样中4种农药残留具有良好的分离富集效果。     

纳米碳纤维涂层固相微萃取探头的制备及性能分析

采用纳米碳纤维(CNF)作为固相涂层制备了固相微萃取探头(SPME)并进行了评价.该涂层对苯系物(BTX)富集能力强,最高使用温度可达260℃,250℃解析条件下使用50次以上涂层无脱落现象.与活性碳涂层相比,尽管萃取量略小,但其解析时间仅为活性炭的60%,具有更高的精密度和准确度.对BrIX固相微萃取.气相色谱分析结果表明,样品质量浓度在0.1～38.7μg/L范围内与色谱峰面积呈良好线性关系(r=0.9891～0.9940),相对标准偏差为3.9%～5.3%,方法的检出限为2.5×10~(-3)μg/L.     

人体腋窝气味的固相微萃取GC-MS分析

采用固相微萃取顶空进样技术和气相色谱-质谱法对人体的腋窝气味进行了分析，探讨了腋窝气味样品的采样方法和分析条件；利用70μm乙烯二醇-二乙烯基苯共聚物(CW-DVB)萃取头对43个人体腋窝气味样品进行了分析，一般获得98～105个色谱峰，检出了36个化合物；发现人体腋窝气味是由脂肪酸、酯、醇、胺、酮等物质组成，多次分析同一个体气味样品的色谱图有较好的相似性；从总的取样及分析结果看，利用固相微萃取顶空进样气相色谱-质谱技术在人体气味的分析研究中有着较好的应用前景。     

固相微萃取/气相色谱-质谱联用法测定橡胶密封材料中N-亚硝胺

建立了固相微萃取/气相色谱-质谱联用法(SPME/GC-MS)测定橡胶密封材料中N-亚硝基-N-甲基苯胺(NMPh A)、N-亚硝基-N-乙基苯胺(NEPh A)和N-亚硝基二苯基胺(NDPhe A)3种N-亚硝胺化合物含量的方法。样品参考国标GB/T 24153-2009进行预处理后,采用固相微萃取进行提取,对影响固相微萃取效率的纤维涂覆种类、萃取时间、搅拌速度和萃取温度等条件进行优化。在优化条件下,方法的线性范围为5~500μg/L,相关系数(r)均大于0.99,检出限为0.5μg/kg,回收率为77%~92%,相对标准偏差(RSD,n=6)为3.8%~7.7%。     

二氧化硅/聚苯乙烯复合微球的制备及作为固相萃取填料的研究

以分散聚合法制备了二氧化硅/聚苯乙烯单分散复合微球,以红外光谱、透射电镜(TEM)、扫描电镜(SEM)等手段对其进行了表征。以合成的二氧化硅/聚苯乙烯作为固相萃取填料制作固相萃取小柱。通过固相萃取与液相色谱联用,测定了水中邻硝基酚、间硝基酚、对硝基酚和辛基酚、壬基酚,考察了固相萃取条件对固相萃取柱性能的影响,选择了最佳的色谱分离条件。结果表明,自制固相萃取小柱对水中硝基酚、烷基酚的萃取率高,与HPLC联用测定结果重现性好,邻硝基酚、间硝基酚、对硝基酚、辛基酚、壬基酚的最低检出限分别为0.90、0.72、0.62、0.38和0.41μg/L。     

溶胶-凝胶富勒烯固相微萃取-气相色谱法测定塑料水浸泡液中多种邻苯二甲酸二酯

利用新型溶胶-凝胶富勒烯涂层,结合顶空固相微萃取-气相色谱法-FID检测,对PVC塑料制品在水溶液浸泡液中的12种邻苯二甲酸二酯进行了分析和测定,其检出限为0.097～3.646 μg/L;回收率为87.9%～107%;RSD<8%.对12种邻苯二甲酸二酯类增塑剂的固相微萃取条件和色谱条件进行了优化,并与商用固相微萃取聚二甲基硅氧烷(PDMS)探头的性能进行了比较.本方法应用于PVC玩具及PVC餐垫样品的分析,结果令人满意.     

固相微萃取-气相色谱-质谱联用分析水中的痕量扑草净

研究了固相微萃取－气相色谱－质谱联用测定水中扑草净的方法，采用聚丙烯酸酯（PA）萃取头，对影响固相微萃取萃取效率的萃取时间、搅拌速度、pH值以及盐度等进行了优化。在优化实验条件下，方法线性范围在0．1mg/mL-1000ng/mL之间，检出限为1．5ng/L。用该法分析了合成井水、自来水和湖水样品，回收率在85．4％－89．1％之间，相对标准偏差在1．8％－5．2％之间。本方法适合于水中痕量扑草净的分析。     

顶空-固相微萃取-气相色谱法检测可可麦汁中吡嗪类化合物

建立了顶空-固相微萃取(HS-SPME)-气相色谱快速测定可可麦汁中3种吡嗪类物质(2,5-二甲基吡嗪、2,3,5-三甲基吡嗪和2,3,5,6-四甲基吡嗪)的方法.选择不同的固相微萃取头对萃取温度和时间进行优化,所得最佳萃取条件为:在60℃下,采用75 μm CAR/PDMS萃取头对麦汁样品萃取40 min.本方法的检出限(S/N=3)为0.023～ 0.056 μg/L,线性范围1～500 mg/L;相对标准偏差为3.6％～6.4％;回收率为95.4％～102.7％.本方法应用于样品检测,发现可可麦汁中吡嗪的浓度与原料中可可粉的添加量正相关,显示了很好灵敏性.     

Preparation, morphologies and properties for flat sheet PPESK ultrafiltration membranes

Flat sheet poly(phthalazinone ether sulfone ketone) (PPESK) ultrafiltration membranes were prepared. The effects of PPESK concentration, solvents, additives and exposing time on the structure and performance of PPESK ultrafiltration membranes were investigated in more detail. The optimal preparation conditions were: 12 wt.% PPESK, NMP/DMAc mixed solvent (mass ratio = 1), 8 wt.% polyethylene glycol 400 (PEG400), 2.5 wt.% LiCl and 5 s exposing time. Under these conditions, the pure water flux and the rejection of γ-globulins were 1139L/m² h and 93.7% at the operation pressure of 0.1 MPa, respectively.

Scanning electron microscope (SEM) micrographs showed that spongy structure could be formed while finger-like structure could be suppressed due to the longer exposing time or higher LiCl concentration.     

Grafting of Acrylamide On 1, 1, 2, 2-Tetra-Chloroethane Preswelled Polyethylene Terephthalate) Films Using Azobisisobutyronitrile Initiator

Abstract

Graft polymerization of acrylamide (AAm) on 1, 1, 2, 2 tetrachloro-ethane (TCE) preswelled poly(ethylene terephthalate) (PET) films were performed with chemical initiation method using asobisiso-butyronitrile (AIBN) initiator. Temperature was found to have a greater effect on the swelling then the swelling time. Variation of the graft yield with polymerization temperature, time, AIBN concentration, AAm concentration, AIBN and AAm inclusion times were investigated. The optimum temperature for grafting was found to be 70°CC. The graft yield was observed to increase with polymerization time, AAm concentration, initiator and monomer diffusion time up to a saturation graft yield and then leveled off. An increase in AIBN concentration first enhanced the percent grafting then showed a decrease. The addition of some salts (Ni²⁺, Cr³⁺, Co²⁺, Cu²⁺) on the rate of grafting was also investigated. From the temperature dependence of the initial rate of grafting, the overall activation energy was found to be 4. 1 kcal/mol and relevant rate equation have been derived. The effect of grafting on film propities, such as water absorption capacity, intrinsic viscosity were determined. Grafted films were characterized by FTIR spectros-copy and scanning electron microscopy (SEM).     

Urine drug testing for opioids,cocaine, and metabolites by direct injection liquid chromatography/tandem mass spectrometry

A sensitive and specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the simultaneous quantification of opioids, cocaine, and metabolites in urine was developed and validated. A 10-microL aliquot of urine was injected directly onto the LC/MS/MS system. The lack of sample preparation substantially reduced total analysis time. Separation was performed by reversed-phase chromatography with gradient elution for all analytes in 26 min. Atmospheric pressure chemical ionization (APCI) was a rugged and efficient ionization technique for basic drugs. Identification and quantification was based on selected reaction monitoring (SRM). Calibration, with deuterated internal standards, was performed by linear regression analysis (weighting factor 1/x). Limits of quantitation (LOQ) were established between 10-100 ng/mL and linearity was obtained up to a maximum of 10 000 ng/mL with an average correlation coefficient (R(2)) > 0.99. Analytical validation criteria for specificity, precision, accuracy, dilution integrity, matrix effect, and stability were fulfilled. The method proved to be simple and time efficient, and was applicable for illicit drug use monitoring and methadone treatment compliance in clinical research projects at the National Institute on Drug Abuse (NIDA).     

Preparation and application of carbon nanotubes/poly(o‐toluidine) composite fibers for the headspace solid‐phase microextraction of benzene,toluene, ethylbenzene,and xylenes

A novel nanocomposite coating of poly(o‐toluidine) and oxidized multiwalled CNTs (MWCNTs, where CNTs is carbon nanotubes) was electrochemically prepared on a stainless‐steel wire. The applicability of the fiber was assessed for the headspace solid‐phase microextraction of benzene, toluene, ethylbenzene, and xylenes in aqueous samples followed by GC with flame ionization detection. In order to obtain an adherent and stable composite coating, several experimental parameters related to the coating process, such as polymerization potential and time, and the concentration of o‐toluidine and oxidized MWCNTs were optimized. The combination of MWCNTs and polymer in a nanocomposite form presents desirable opportunities to produce materials for new applications. The effects of various parameters on the efficiency of the headspace solid‐phase microextraction process, such as desorption temperature and time, extraction temperature and time, and ionic strength were also investigated. At the optimum conditions, LODs were 0.03–0.06 μg/L. The method showed linearity in the range of 0.5–300 μg/L with coefficients of determination >0.99. The intraday and interday RSDs obtained at a 5 μg/L concentration level (n = 5) using a single fiber were 1.2–5.2 and 3.2–7.5%, respectively. The fiber‐to‐fiber RSD (%; n = 3) at 5 μg/L was 6.1–9.2%.     

Antifluorite-type lithium chromium oxide nitrides: synthesis, structure, order, and electrochemical properties

Antifluorite-type lithium chromium oxide nitrides were prepared by solid-state reaction of Li(3)N, Li(2)O, and Cr(2)N. Depending on the reaction time and starting Li/Cr and O/Cr ratios, either an ordered or a disordered phase (or mixtures of both) is obtained. The formation of the former is favored by short reaction times and low Cr/O ratios whereas the formation of the latter is favored by higher Cr/O ratios and longer reaction times. The two phases were characterized, and the first one was confirmed to be the already reported Li(14)Cr(2)N(8)O phase, whereas the stoichiometry of the second is Li(10)CrN(4)O(2). Interestingly, even if both contain cationic vacancies in the structure, electrochemical lithium intercalation could only be achieved for Li(10)CrN(4)O(2). This phase exhibits a reversible capacity of 160 mAh/g very stable upon cycling. Bond valence and first-principles DFT calculations were carried out to understand the absence of lithium insertion in Li(14)Cr(2)N(8)O. Li-Li repulsion and destabilization of the tetrahedral CrN(4) units induced by occupation of the potential sites, as well as the absence of energetically favorable pathways for transport of the ions to these sites, are suggested to be the reasons.     

Walnut Oil Nanoemulsion: Optimization of the Emulsion Capacity,Cloudiness, Density,and Surface Tension

Response surface methodology (RSM) in conjunction with central composite rotatable design (CCRD) was employed to find out the influence of preparation properties of walnut oil/water nanoemulsion namely ultrasonic time (5–15 minutes), walnut oil content (4–10% w/w) and concentration ratio of Span 80 to Tween 80 (K ₀, 0.55–0.80) on response variables including emulsion capacity, cloudiness, density and surface tension. The calculated regression models with high value of coefficient of determination (0.910–0.973) and insignificant lack of fit test indicated satisfactory agreement of empirical models with experimental observations. The results revealed linear term of walnut oil concentration was the most significant (p < 0.05) parameter on the all responses. The overall optimum region to achieve the ideal characteristics was ultrasonic time of 11.74 minutes, walnut oil content of 4.00% (w/w) and K ₀ of 0.80.     

Phytochemical Characterization,In Vitro Anti-Inflammatory,Anti-Diabetic,and Cytotoxic Activities of the Edible Aromatic Plant; Pulicaria jaubertii

Pulicaria jaubertii is a medicinal herb that alleviates inflammations and fever. Chromatographic separation, phytochemical characterization, and in vitro biological activities of the plant n-hexane extract were conducted for the first time in this study. Six compounds were isolated for the first time from the n-hexane fraction of Pulicaria jaubertii aerial parts and were identified on the bases of NMR and MS analyses as pseudo-taraxaterol (1), pseudo-taraxasterol acetate (2), 3β-acetoxytaraxaster-20-en-30-aldehyde (3), calenduladiol-3-O-palmitate (4), stigmasterol (5), and α-tocospiro B (6). Compound (6) was a rare tocopherol-related compound and was isolated for the first time from family Asteraceae, while compound (3) was isolated for the first time from genus Pulicaria. The total alcoholic extract and n-hexane fraction were tested for their anti-inflammatory, antidiabetic, and cytotoxic activities. The n-hexane fraction has dose dependent red blood cells (RBCs) membrane stabilization and inhibition of histamine release activities with IC₅₀: 60.8 and 72.9 µg/mL, respectively. As antidiabetic activity, the alcoholic extract exerted the most inhibition on the activity of yeast α-glucosidase, with an IC₅₀: 76.8 µg/mL. The n-hexane fraction showed cytotoxic activity against hepatocarcinoma (HepG-2), breast carcinoma (MCF-7), and prostate carcinoma (PC-3) cell lines with IC₅₀: 51.8, 90.8 and 62.2 µg/mL, respectively. In conclusion, the anti-inflammatory effect of Pulicaria jaubertii might be attributed to the triterpenoid constituents of the n-hexane extract of the plant.     

Multiresidue screening of pesticides in foods using retention time locking, GC-AED, database search, and GC/MS identification

Fruit and vegetable extracts were screened for over 400 pesticides by gas chromatography with atomic emission detection (GC-AED) and an experimental database. A technique called retention time locking was used to match GC-AED and GC with mass spectrometry (MS) retention times to those of the database. Samples were analyzed for sulfur, nitrogen, phosphorus, and chlorine by GC-AED. Possible pesticides were suggested by database search and identified by GC/MS. Forty-four pesticide standards were analyzed to determine the precision of retention time matching and the accuracy of the database search. Analytical retention times matched database retention times within 0.32 min. Using elemental criteria, the database search identified the correct compound for 41 of 44 pesticide standards. For blind spikes of fruit and vegetable extracts, the database suggested 22 of 26 spiked pesticides as matches. Nineteen were identified by GC/MS. The combination of retention time locking, GC-AED, database search, and GC/MS can be a powerful tool for identifying pesticides in a complex matrix.     

Self-sustaining hybrid electrode prepared from polyaniline,carbon nanotubes,and carbon fibers: morphological,structural, and electrochemical analyses

The self-sustaining hybrid electrode was prepared via chemical polymerization of aniline in acid medium containing dispersed carbon nanotubes (CNT), using carbon fiber (CF) as conducting substrate. The ternary composites called PAni/CNT/CF were characterized in order to evaluate their morphologies, structures, and thermal properties. The influence of the polyaniline (PAni) layer in the ternary composite properties was studied considering different deposition times on CF samples (30, 60, and 90 min). The ternary composite morphologies were observed by scanning electron microscopy while thermal structural analyses were obtained using thermogravimetric measurements. The structural features were analyzed by Raman scattering spectroscopy and Fourier transform infrared spectroscopy (FTIR). The possible interactions between PAni and CNT were discussed on the basis of Raman and FTIR spectra. These spectroscopic analyses also confirmed that the PAni present in the composite is in the emeraldine (ES) salt form. Furthermore, the ternary composites were also evaluated by electrochemical measurements such as cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) techniques. The results showed good charge storage capacity for ternary composites, in particular, for PAni/CNT/CF obtained with 90 min of deposition time, which exhibited specific capacitance of around 500 F g^?1. Therefore, this electrode was selected to build a prototype of type I supercapacitor. This device presented specific capacitance of around 143 F g^?1 after 3200 charge/discharge cycles.     

Synthesis of variable-aspect-ratio, single-crystalline ZnO nanostructures

Variable-aspect-ratio (length/diameter), one-dimensional (1-D) ZnO nanostructures (nanorods and nanowires) were prepared in alcohol/water solution by reacting a Zn2+ precursor with an organic weak base, tetramethylammonium hydroxide (Me4NOH). The effect of the experimental parameters (temperature, base concentration, reaction time, and water content) on nucleation, growth, and the final morphology of the ZnO nanostructures was investigated. The low-temperature syntheses (75-150 degrees C) yielded aspect ratios of the 1-D ZnO nanostructures that depended on the water content. The individual ZnO nanorods and nanowires were determined to be perfect, single crystals with their c axes as the primary growth direction.