液相微萃取/离子色谱测定牛奶中的氨

以水为微滴萃取溶剂,采用顶空液相微萃取/离子色谱检测了牛奶中的氨.优化了顶空液相微萃取的实验条件:pH=12,萃取温度为35 ℃,萃取时间为15 min,搅拌速率为800 r/min,萃取溶剂体积为5 μL.测定氨的线性范围为10 ～300 μg·L-1(R2=0.998),检出限达1.8 μg·L-1,回收率为92% ～105%.     

顶空液相微萃取/气相色谱-质谱对中药枳壳中有机挥发物的快速分析

建立了顶空液相微萃取/气相色谱-质谱联用测定中药枳壳中有机挥发物的方法.在顶空液相微萃取实验条件优化的基础上,确定了最佳实验条件:以正辛烷作为有机萃取剂,体积为2 μL,样品用量为0.3 g,液滴距离样品表面0.8 cm处,萃取8 min后直接进样.与固相微萃取/气相色谱-质谱法相比,顶空液相微萃取法定性了30种成分,固相微萃取法定性了24种成分,顶空液相微萃取法操作简单、快速,实验结果灵敏度更高,且萃取效率高,重复性好,可用于中药枳壳中有机挥发物的快速分析.     

微波辅助-顶空液相微萃取/高效液相色谱分析水样中的邻硝基苯酚

建立了基于微波辅助-顶空液相微萃取在线联用、高效液相色谱法测定水样中邻硝基苯酚的分析方法。采用L16(45)正交实验设计对影响萃取的各种因素,如萃取有机溶剂、微波辐射功率、萃取时间、离子强度、样品液体积,进行了优化。优化后萃取条件为,以乙酸丁酯作为萃取溶剂,功率和时间分别为100W和12min条件下,离子强度为0的样品溶液体积为20mL。在优化萃取条件下,邻硝基苯酚的检出限LOD(S/N=3)为0.94μg/L,萃取富集倍数为30,实际水样的加标回收率为85.2%。理论分析和实验结果表明,微波辅助-顶空液相微萃取在线联用方法具有简便、快速、高效、节省溶剂、选择性好、应用范围广的特点。     

微波辅助-顶空液相微萃取在线联用-高效液相色谱法测定环境水样中的敌敌畏

基于微波辅助-顶空液相微萃取联用(MAE-HS-LPME)这一样品前处理方法,采用高效液相色谱法(HPLC)对水样中的敌敌畏残留量进行了测定。对影响萃取的因素如萃取剂、微波辐射功率、萃取时间、离子强度和样品基质的pH值等进行了考察。萃取条件为: 选用二甲苯作萃取剂,萃取时间为15 min,微波辐射功率300 W,NaCl含量为5%,pH为2.5。在最佳条件下,敌敌畏的检出限(信噪比为3时)为0.96 μg/L,定量限(信噪比为10时)为3.20 μg/L,萃取富集倍数为54,实际水样的加标回收率为87.4%～103%。与传统的前处理方法相比,本方法具有简便、快速、高效、节省溶剂、选择性好、应用范围广的特点。     

水中氯苯类污染物的顶空液相微萃取 GC-MS法测定

研究了用顶空液相微萃取GC-MS法测定水中的痕量氯苯类有机污染物。通过实验选择正辛醇为萃取剂,考察了萃取剂的体积、萃取温度、萃取时间、搅拌速度、样品顶空体积以及盐效应等对萃取的影响。在最佳萃取和测定条件下,方法的线性范围为0.1~800μg/L,检出限(S/N=3)为0.05~0.1μg/L。用本方法测定了实际样品及回收率,结果满意。     

水中挥发性有机物分析前处理技术研究进展

环境水体中挥发性有机物(VOCs)的种类繁多,含量在(ng/L～μg/L)范围内。本文总结了2003年以来测定水样中VOCs的8种前处理技术,包括顶空单液滴微萃取(HS-SDME)、中空纤维液相微萃取(HF-LPME)、分散液液微萃取(DLLME)、顶空固相微萃取(HS-SPME)、搅拌棒吸附萃取(SBSE)、静态顶空(HS)、吹扫捕集法(P&T)和针式毛细管吸附阱(INCAT)的进展情况。比较了它们的优缺点,并展望了VOCs的分析方法。     

顶空液相微萃取-胶束电动毛细管色谱分析药品中酯类防腐剂

建立了在同一根毛细管上实施萃取剂定容、微液滴悬挂、富集液注入和胶束电动毛细管色谱分析的一体化顶空液相微萃取#胶束电动毛细管色谱联用技术,并将其用于药品中对羟基苯甲酸酯类防腐剂的分析。将二甲亚砜-甲苯(1∶4,V/V)混合萃取剂(避免接触皮肤)用压力充满容积约1μL的分离毛细管,再从毛细管末端用压力将含150mmol/L十二烷基硫酸钠的20mmol/L硼砂缓冲液(pH9.3)充满毛细管,同时推出萃取剂,使溶剂微液滴悬挂于毛细管进样端;在加入8mL样品溶液(含0.3g/mL NaCl)的14mL样品瓶中,以90℃顶空萃取30min;高差10cm进样20s后,进行胶束电动毛细管色谱分析。对羟基苯甲酸甲、乙和丙酯的富集倍数为25～86,检出限为0.01～0.05mg/L,回收率为92.2%～107%。此联用技术可有效富集中性分析物,消除样品基体干扰,适用于复杂基体样品内中性分析物的毛细管电泳分析。     

聚苯乙烯-丙烯酸丁酯固相微萃取新型吸附质的研究与应用

实验以丙烯酸丁酯和苯乙烯为单体 ,过氧化苯甲酰为引发剂 ,醋酸丁酯和甲苯作混合溶剂 ,溶剂用量与单体混合物的体积相同。采用溶液聚合的方法合成了一种新型固相微萃取吸附质 (苯乙烯 -丙烯酸丁酯共聚物 ) ,研究了此聚合物作为固相微萃取吸附质的性能。用顶空萃取法对水中低级芳烃化合物进行了萃取实验 ,考察了此高聚物涂层的热稳定性及单体比例与萃取率的关系。将自制涂层与PDMS涂层对低级芳烃化合物萃取量进行了比较 ,反映了苯乙烯 丙烯酸丁酯聚合物涂层的特点。     

离子液体顶空液相微萃取富集苯系物

以水不互溶的离子液体1-丁基-3-甲基咪唑的六氟磷酸盐作为顶空液相微萃取的萃取剂,能够从水溶液中有效地萃取苯系物。当萃取时间为30min时,富集倍数在19～50之间。     

顶空液相微萃取-气相色谱质谱法快速测定饮料中苯和甲苯

建立了顶空液相微萃取-气相色谱质谱法测定饮料中苯和甲苯的方法。在对顶空液相微萃取(head-space liquid-phase microextraction,HS-LPME)实验条件优化的基础上,确定了最佳实验条件:以1.6μL正辛醇作为有机萃取剂,在萃取温度为50℃、萃取时间为5min,搅拌速度为750r/min,液滴离萃取瓶瓶塞2.0cm的条件下,萃取4.00mLNaCl含量为4.00mol/L的样品水溶液,取0.4μL的有机萃取剂直接进样。实验结果表明,苯和甲苯的富集倍数分别为94和191,方法检出限分别为0.090μg/L和0.093μg/L,线性范围为0.5～60μg/L(r>0.999)。将该方法应用于饮料中苯和甲苯的测定,回收率为93.6%和98.0%,相对标准偏差(RSD)为3.94%和2.69%。方法简单、快速且成本低、可信度高,适用于饮料和水样中苯和甲苯的快速分析。     

Ultra-sensitive determination of cadmium in rice and water by UV-vis spectrophotometry after single drop microextraction

In this work, a new method based on single drop microextraction (SDME) preconcentration using tetrachloromethane (CCl(4)) as extraction solvent was proposed for the spectrophotometric determination of cadmium in rice and water samples. The influence factors relevant to SDME, such as type and volume of extractant, stirring rate and time, dithizone concentration, pH, drop volume and instrumental conditions were studied systematically. Under the optimal conditions, the limit of detection (LOD) was 0.5 ng L(-1), with sensitivity enhancement factor (EF) of 128. The different maximum absorption wavelength caused by the different extraction acidity compared with some conventional works and the enhancement effect of acetone (dilution solvent) for the spectrophotometric determination were the two key factors of the high EF and sensitivity. The proposed method was applied to the determination of rice and water samples with satisfactory analytical results. The proposed method was simple, rapid, cost-efficient and sensitive.     

Drop extraction preconcentration of organochlorine and aromatic impurities with carbon tetrachloride

A drop version of the extraction preconcentration of organochlorine and aromatic impurities from water is developed. One microliter of carbon tetrachloride is used as an extractant. The distribution and preconcentration coefficients of impurities are determined. Factors affecting the stability of the extractant drop are studied. The limits for the gas-chromatographic detection of the impurities with their drop preconcentration are (2–5) × 10^?5 mg/L.     

Temperature-controlled headspace liquid-phase microextraction device using volatile solvents

A novel temperature-controlled headspace liquid-phase microextraction (TC-HS-LPME) device was established in which volatile solvents could be used as extractant. In this device, a PTFE vial cap with a cylindrical cavity was used as the holder of the extraction solvent. Up to 40 μl of extraction solvent could be suspended in the cavity over the headspace of aqueous sample in the vial. A cooling system based on thermoelectric cooler (TEC) was used to lower the temperature of extractant in PTFE vial cap to reduce the loss of volatile solvent during extraction process and increase the extraction efficiency. The selection of solvents for HS-LPME was then extended to volatile solvents, such as dichloromethane, ethyl acetate and acetone. The use of volatile extraction solvents instead of semi-volatile solvent reduced the interference of the large solvent peak to the analytes peaks, and enhanced the compatibility of HS-LPME with gas chromatograph (GC). Moreover, the use of larger volume of extractant solvent increases the extraction capacity and the injection volume of GC after extraction, thus improving detection limits. Several critical parameters of this technique were investigated by using chlorobenzenes (CBs) as the model analytes. High enrichment factors (498–915), low limits of detection (0.004–0.008 μg/L) and precision (3.93–5.27%) were obtained by using TC-HS-LPME/GC-FID. Relative recoveries for real samples were more than 83%.     

Solute-induced dissolution of hydrophobic ionic liquids in water

Significant solubilization of ostensibly water-immiscible ionic liquids (ILs) in acidic aqueous phases is induced by the presence of any of a variety of neutral extractants, the apparent result of the formation of the protonated form of the extractant and its subsequent exchange for the cationic component of the IL. The extent of this solubilization is shown to diminish with increasing hydrophobicity of the IL cation and decreasing extractant basicity. These observations raise concerns as to the viability of ILs as “drop in replacements” for traditional organic solvents in the solvent extraction of metal ions.     

Determination of organophosphorus pesticides in water samples by single drop microextraction and gas chromatography-flame photometric detector

In this paper we have developed single drop microextraction (SDME) with modified 1.00 microl microsyringe, followed by gas chromatography with flame photometric detector (GC-FPD) for determination of 13 organophosphorus pesticides (OPPs) in water samples. By using a 1.00 microl microsyringe the repeatability of drop volume and injection were improved, because of using maximum volume of microsyringe and no dead volume. On the other hand, the modification of needle tip caused increasing cross section of needle tip and increasing adhesion force between needle tip and drop, thereby increasing drop stability and achieving a higher stirrer speed (up to 1700 rpm). The method used 0.9 microl of carbon tetrachloride as extractant solvent, 40 min extraction time, stirring at 1300 rpm and no salt addition. The enrichment factor of this method ranged from 540 to 830. The linear ranges were 0.01-100 microg/l (four orders of magnitude) and limits of detection were 0.001-0.005 microg/l for most of analyte. The relative standard deviation (RSD%) for 2 microg/l of OPPs in water by using internal standard was in the range 1.1-8.6% (n = 5). The recoveries of OPPs from farm water at spiking level of 1.0 microg/l were 91-104%.     

Analysis of cesium extracting solvent using GCMS and HPLC

A high-level waste (HLW) remediation process scheduled to begin in 2007 at the Savannah River Site is the Modular Caustic Side Solvent Extraction (CSSX) Unit (MCU). The MCU will use a hydrocarbon solvent (diluent) containing a cesium extractant, a calix[4]arene compound, to extract radioactive cesium from caustic HLW. The resulting decontaminated HLW waste or raffinate will be processed into grout at the Saltstone Production Facility (SPF). The cesium containing CSSX stream will undergo washing with dilute nitric acid followed by stripping of the cesium nitrate into a very dilute nitric acid or the strip effluent stream and the CSSX solvent will be recycled. The Defense Waste Processing Facility (DWPF) will receive the strip effluent stream and immobilize the cesium into borosilicate glass. Excess CSSX solvent carryover from the MCU creates a potential flammability problem during DWPF processing. Bench-scale DWPF process testing was performed with simulated waste to determine the fate of the CSSX solvent components. A simple high performance liquid chromatography (HPLC) method was developed to identify the modifier (which is used to increase Cs extraction and extractant solubility) and extractant within the DWPF process. The diluent and triocytlamine (which is used to suppress impurity effect and ion-pair disassociation) were determined using gas chromatography mass spectroscopy (GCMS). To close the organic balance, two types of sample preparation methods were needed. One involved extracting aqueous samples with methylene chloride or hexane, and the second was capturing the off gas of the DWPF process using carbon tubes and rinsing the tubes with carbon disulfide for analysis. This paper addresses the development of the analytical methods and the bench-scale simulated waste study results.     

Sensitive determination of free benzophenone-3 in human urine samples based on an ionic liquid as extractant phase in single-drop microextraction prior to liquid chromatography analysis

Benzophenone-3 (BZ3), one of the compounds most commonly used as UV filter in cosmetic products, can be absorbed through the skin into the human body, since it can be found at trace levels in urine from users of cosmetic products that contain BZ3. Moreover, different undesirable effects have been attributed to this compound. Thus, sensitive analytical methods to monitor urinary excretion of this compound should be developed. This paper presents a selective and sensitive methodology for BZ3 determination at ultratrace levels in human urine samples. The methodology is based on a novel microextraction technique, known as single-drop microextraction (SDME). An ionic liquid (IL) has been used as extractant phase instead of an organic solvent. After the microextraction process, the extractant phase was injected into a liquid chromatography system. The variables of interest in the SDME process were optimized using a multivariate optimization approach. A Plackett-Burman design for screening and a circumscribed central composite design for optimizing the significant variables were applied. Ionic strength, extraction time, stirring speed, pH, ionic liquid type, drop volume and sample volume were the variables studied. The optimum experimental conditions found were: sodium chloride concentration, 13% (w/v); extraction time, 25 min; stirring speed, 900 rpm; pH, 2; ionic liquid type, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)MIM][PF(6)]); drop volume, 5 microL; and sample volume, 10 mL. The proposed method requires a standard addition calibration approach, and it has been successfully employed to determine free BZ3 in urine samples coming from human volunteers who applied a sunscreen cosmetic containing this UV filter. The limit of detection was in the order of 1.3 ng mL(-1) and repeatability of the method, expressed as relative standard deviation, was 6% (n=8).     

Novel mode of liquid‐phase microextraction: A magnetic stirrer as the extractant phase holder

In the present study, a novel configuration of liquid‐phase microextraction was proposed, in which a magnetic stirrer with a groove was used as the extractant phase holder. It was termed as magnetic stirrer liquid‐phase microextraction. In this way, the stability of the organic solvent was much improved under high stirring speed; the extraction efficiency was enhanced due to the enormously enlarged contact area between the organic solvent and aqueous phase. The extraction performance of the magnetic stirrer liquid‐phase microextraction was studied using chlorobenzenes as the probe analytes. A wide linearity range (20 pg/mL to 200 ng/mL) with a satisfactory linearity coefficient (r² > 0.998) was obtained. Limits of detection ranged from 9.0 to 12.0 pg/mL. Good reproducibility was achieved with intra‐ and inter‐day relative standard deviations <4.8%. The proposed magnetic stirrer liquid‐phase microextraction was simple, environmentally friendly and efficient; compared to single‐drop microextraction, it had obvious advantages in terms of reproducibility and extraction efficiency. It is a promising miniaturized liquid‐phase technology for real applications.     

Barrier film protected, and mixed solvent optimized micro-scale membrane extraction of methyl carbamate pesticides

Hollow fiber based microextraction has emerged as an effective alternative to conventional preconcentration techniques. The loss of the extractant solvent through the membrane has been an important issue, and dip-coating with a barrier film is a method for stabilizing the acceptor. Typically, only one solvent is used to serve as the extractant, which limits the range of compounds that can be analyzed simultaneously. Mixing solvents in varying proportions can increase the range of compounds enriched. This paper reports the optimization of the microextraction system by implementing a barrier film to reduce solvent loss, in conjunction with the use of mixed solvents to enrich a broader spectrum of analytes. A group of five carbamate pesticides were studied here. The detection limits were at ppb levels and the enrichment was as high as 1600 times depending upon the solvent. R2 and %RSD ranged from 0.9501 to 0.9991 and 1.90 and 9.53, respectively.     

悬浮固化分散液液微萃取-毛细管电泳法测定水中磺酰脲类除草剂

建立了悬浮固化分散液液微萃取-毛细管电泳法同时测定水中磺酰脲类除草剂残留的方法。以十二醇为萃取剂、甲醇为分散剂,采用悬浮固化分散液液微萃取技术对水样进行分离提取,并结合毛细管电泳法进行测定。该方法可以有效提取、分离、检测水中残留的微量苯磺隆、吡嘧磺隆、苄嘧磺隆等9种磺酰脲类除草剂,各待测物在10.0~1000 μg/L范围内线性关系良好,相关系数r≥0.992,方法检出限为2.40~7.50 μg/L,方法精密度为6.55%~13.9%。将该方法用于实际水样的测定,取得了较满意的结果,加标回收率为82.0%~104%。该方法简便快速,适合水中磺酰脲类除草剂的同时测定。