样品预处理与实时直接分析质谱的联用技术及应用

近年来,与实时直接分析质谱(DART-MS)相结合的样品预处理技术发展迅速,使得对复杂生物、环境、法医学、食品、个体小生物以及单细胞样品中的分析物进行直接分析成为可能。然而固体基质内部分析物检测困难、痕量分析物检测性能不佳已成为限制DART-MS进一步发展的关键问题。针对这些问题,多年来,研究人员在不同领域对样品预处理与质谱联用进行了多种尝试。该文以固相萃取(SPE)、分散固相萃取(DSPE)、搅拌棒吸附萃取(SBSE)、固相微萃取(SPME)、机械化学提取(MCE)和微波提取(MAE)等样品预处理技术为例,对不同研究领域中样品预处理技术与DART-MS联用的研究成果进行了综述,并对未来的发展趋势进行了展望。希望该综述能为开发与DART-MS联用的新型样品处理技术提供参考和帮助。     

沙土中5种神经性毒剂降解产物的实时直接分析-质谱法快速检测

建立了实时直接分析离子源-质谱（DART-MS）快速检测沙土中5种神经性毒剂降解产物的方法。方法在0.03～10 mg/L范围内线性关系良好，检出限为0.03～0.1 mg/kg, 5种神经性毒剂降解产物在沙土中的回收率均不低于71.8%，相对标准偏差（RSD）不超过11%。利用建立的DART-MS定性方法分析了禁止化学武器组织（OPCW）的PT48次环境样品水平考试盲样样品，根据获得的母离子和碎片离子的高分辨质谱（HRMS）数据及MS/HRMS质谱碎裂特征，鉴定出所有适合DART-MS分析的化学毒剂相关化合物，与OPCW发布的配样清单一致。     

不同石斛枫斗中酚酸类活性成分的比较及杓唇石斛素和石斛酚含量的测定

建立了基于液相色谱-离子阱飞行时间串联质谱(LC-IT-TOF MS/MS)的酚酸类分析方法,对6种共18批次的石斛枫斗药材中的酚类化合物进行了研究,其中18种酚酸类化合物得到初步定性。在共有化合物中选择杓唇石斛素和石斛酚作为质量控制的目标化合物。在此基础上,采用响应面法(RSM)确定了提取溶剂为60%甲醇、提取时间为65 min的超声提取杓唇石斛素和石斛酚的最佳条件,建立了石斛枫斗中杓唇石斛素、石斛酚的高效液相色谱(HPLC)含量测定方法。定量线性优于0.999 8,检出限(LOD)分别为0.18 mg/L和0.09 mg/L,重复性的相对标准偏差(RSD)小于3%,加标回收率均值分别为97.1%和101.4%。这些结果表明本研究建立的方法可用于石斛枫斗药材中酚酸类化学成分研究及质量控制。     

实时直接分析质谱法快速鉴别天然驱蚊产品中的人工添加剂

采用DART-MS(实时直接分析质谱法)建立了一种简单快速测定人工合成驱蚊化合物如DEET(避蚊胺)、BAAPE(驱蚊酯)等的方法.在常温常压下,无需对天然驱蚊产品进行任何预处理,通过比对标准品的质谱信号离子,即可快速鉴别出天然驱蚊产品中的人工添加剂.该方法大大缩短了分析时间,并且具有原位、准确且高通量的优点.     

实时直接分析-串联质谱法测定葡萄酒中赭曲霉毒素A

建立了葡萄酒中赭曲霉毒素A的实时直接分析-串联质谱(DART-MS/MS)方法。前处理采用乙酸乙酯提取,二甲基十八碳硅烷粉(ODS)粉分散固相萃取净化,采用DART-MS/MS检测,同位素稀释内标法定量。结果表明:在1.0、2.0、10μg/kg 3个加标水平下,回收率为88.7%~105.7%,RSD为8.5%~12.8%,定量限为0.5μg/kg。该方法具有简单、快速、灵敏度高等特点,能满足葡萄酒中赭曲霉毒素A检测的要求。     

实时直接分析-串联质谱法快速筛查火锅底料、牛肉面汤及调味料中罂粟壳生物碱

建立了采用实时直接分析-串联质谱(DART-MS/MS)对火锅底料、牛肉面汤及调味料中5种非法添加的罂粟壳生物碱进行快速筛查的方法。样品经乙腈提取净化后,在离子化温度为300℃、栅极电压为150 V、进样速率为0.8 m m/s的DART离子源正离子模式条件下进样,以电喷雾离子源正离子多反应监测(MRM)模式进行检测,实现了样品经简单预处理后使用DART-MS/MS进行检测的新方法。该方法简便、快速,能满足大批量非法添加样品的快速筛查分析要求。     

实时直接分析质谱在农药检测中的应用

实时直接分析(Direct analysis in real time,DART)作为一种原位电离技术发展迅猛,其与质谱联用已成为热门的分析技术并广泛应用于法庭科学领域,如食品安全、爆炸物检测、毒物毒品分析和药物分析等方面。目前农药的常规检测方法已非常成熟,但引入原位电离-质谱联用技术可以拓宽检测范围,缩短检测时限。该文从实时直接分析质谱(DART-MS)技术的工作原理、检测条件优化及其在农药检测方面的应用进行综述,并对DART-MS的应用前景进行了展望。     

电喷雾离子源中样品离子化能量转移理论的初探

电喷雾离子源（electrospray ionization,ESI）不仅可以用于小分子的检测,也能够用于蛋白质、多肽等大分子的研究。本文通过对离子化过程的系统分析,提出了基于能量最低原理的离子化过程能量转移理论。样品分子在由液相转移到气相形成离子化气体的过程中受到静电力、分子间的范德华力等多种力的作用。样品的离子化是多种力共同作用的结果,在不同的离子化阶段,不同形式的力的作用也不尽相同。电荷在样品表面蒸发和多电荷离子的形成之间存在竞争。对不同结构的分子,分子形态、构象改变导致的两相间转移Gibbs自由能变化不同,可能导致离子蒸发、大分子形成多电荷离子、产生链弹射等行为。离子化能量转移理论不仅能够对已有的3种理论加以简化统一,也可以说明溶剂、电解质离子等在离子化过程中的作用,为优化不同结构与形态样品的质谱检测、了解离子化的真实过程提供了一种可能的依据。     

人参多糖部分酸水解物的HPLC-ESI-QTOF-MS分析

本文采用酸水解方式,获得人参多糖的部分水解产物,通过高效液相色谱-电喷雾电离高分辨飞行时间质谱(HPLC-ESI-QTOF-MS)对人参多糖部分酸水解产物进行分析,建立人参多糖糖谱研究的方法。同时结合几种标准二糖的MS和MS/MS分析,建立依靠质谱分析确定多糖糖苷键类型的方法。研究结果确定了5种糖苷键链接类型在MS/MS中的断裂规律,并发现人参多糖的糖苷键链接类型为1,3糖苷键和1,4糖苷键。本文研究方法,具有简单快速、稳定性好、准确度高等优点,为中草药的指纹性糖谱研究提供了新的借鉴方法。     

实时直接分析-四极杆飞行时间质谱法快速鉴别油茶籽油真伪

建立了实时直接分析-四极杆飞行时间质谱(DART-QTOF-MS)技术结合化学计量学分析快速鉴别油茶籽油的方法。4种食用油(油茶籽油、菜籽油、花生油和大豆油)用甲醇-异丙醇(50∶50,含5 mmol/L乙酸铵)稀释后经实时直接分析离子源解吸电离,在正离子模式下以TOF MS和信息依赖采集模式获得质谱数据,对4种食用油的质谱图进行了初步鉴定,并采用化学计量学建立主成分分析(PCA)和正交偏最小二乘法-判别分析(OPLS-DA)模型,以实现数据可视化和油茶籽油的快速鉴别。结果表明,4种食用油的质谱图存在明显差异,主要为甘油三酯(TAG)氨加合离子［TAG+NH4］+(m/z 850~1 100)、甘油二酯(DAG)氨加合离子［DAG+NH4］+(m/z 600~700)和DART源内碎片离子,共检出20种甘油三酯和6种甘油二酯。进一步采用化学计量学对4种植物油指纹图谱进行分析,发现该方法可准确鉴别和预测油茶籽油、菜籽油、花生油和大豆油,具有前处理简单、分析速度快、操作方便和准确可靠等优点,可用于油茶籽油的鉴别研究。     

Rapid screening for synthetic antidiabetic drug adulteration in herbal dietary supplements using direct analysis in real time mass spectrometry

Adulteration of herbal supplements with synthetic drugs is illegal. A rapid and reliable method which utilizes direct analysis in real time mass spectrometry (DART-MS) was developed for the identification of seven synthetic antidiabetic drugs used as adulterants in herbal dietary supplements. The supplement sample was simply extracted with methanol/water by manually shaking several times and directly analyzed using DART-MS. The presence of synthetic drug adulterants was confirmed through the accurate m/z values and MS/MS data obtained via quadruple time of flight mass spectrometry (QTOF MS). Parameters for the DART source were systematically optimized, and the limits of detection (LODs) in herbal supplement matrices were measured. This method was successfully applied to examine five commercial herbal dietary supplements, and two of them proved to be adulterated with metformin without labeling.     

A novel and rapid HPGPC-based strategy for quality control of saccharide-dominant herbal materials: Dendrobium officinale,a case study

Qualitative and quantitative characterization of natural saccharides, especially polysaccharides, in herb materials remains a challenge due to their complicated structures and high macromolecular masses. Currently available methods involve time-consuming and complicated operations, and present poor specificity. Here, a novel and rapid high-performance gel permeation chromatography (HPGPC)-based approach is described for quality assessment of saccharide-dominant herbal materials by simultaneous qualitative and quantitative analysis of saccharide components. Dendrobium officinale, one of the rarest tonic herbs worldwide, was employed as the model herb in this study. First, a HPGPC fingerprint based on the molecular weight distribution of its carbohydrate components was established for qualitative identification of D. officinale. Then, HPGPC-guided dominant holistic polysaccharide marker was separated using ultra-filtration followed by HPGPC determination for quantitative evaluation of D. officinale. The experimental results suggest that this method is more efficient, stable, and convenient compared with the currently available methods for authentication and quality evaluation of D. officinale, and we expect the method will have similar advantages when used for quality control of other saccharide-dominant herbal materials and products. Graphical Abstract

The characteristic HPGPC fingerprint of Dendrobium officinale compared with other confused Dendrobium species     

Rapid identification of traditional Chinese herbal medicine by direct analysis in real time (DART) mass spectrometry

Direct analysis in real time-mass spectrometry (DART-MS) was employed as a novel fast method to identify traditional Chinese herbal medicine (TCHM). In order to obtain high quality mass spectra, the ionization temperature was optimized for every kind of sample. With minimal or no sample pretreatment, major TCHM components, including alkaloids, flavonoids and some ginsenosides, were directly detected within several seconds, while thirteen ginsenosides need derivatization to get good mass spectra. Pseudoginsenoside F11, compound K, protopanaxatriol (PPT) and protopanaxadiol (PPD), for the first time were detected without derivatization. Among five of eight tested Chinese herbal medicines, Rhizoma Corydalis, Bulbus Fritillariae Thunbergii, Arecae Semen, Ramulus Uncariae Cum Uncis and Scutellariae Radix, were first time identified by DART-MS. In addition, the ionization mechanisms of major herbal components, alkaloids, flavonoids and ginsenosides, were discussed in detail. Our results demonstrated that DART-MS could provide a rapid, reliable and environmental friendly method for the rapid identification of TCHM, and may be applicable to other plants.     

不同产地金线莲根茎和叶中多糖含量对比

考察了不同产地金线莲根茎和叶中多糖含量。应用超声辅助法和微波-超声协同萃取法提取金线莲根茎和叶中多糖,用苯酚-硫酸法测定其含量。微波-超声协同萃取法提取优于超声辅助法提取,金线莲根茎部的多糖含量高于叶中多糖含量,福建华安产金线莲多糖含量最高。金线莲中多糖含量为0.8509%～6.400%,具有开发药用的价值。     

Rapid Analysis of Ingredients in Cream Using Ultrasonic Mist–Direct Analysis in Real-Time Time-of-Flight Mass Spectrometry

A novel method for the simultaneous detection of ingredients in pharmaceutical applications such as creams and lotions was developed. An ultrasonic atomizer has been used to produce a mist containing ingredients. The analyte molecules in the mist can be ionized by using direct analysis in real time (DART) at lower temperature than traditionally used, and we thus solved the problem of normal DART-MS measurement using a high-temperature gas. Thereby, molecular-related ions of heat-unstable components and nonvolatile components became detectable. The deprotonated molecular ion of glycyrrhizic acid (m/z 821), which is unstable at high temperatures, was detected without pyrolysis by ultrasonic mist–DART-MS using unheated helium gas, although it was not detected by normal DART-MS using heated helium gas. The cationized molecular ions of derivatives of polyethylene glycol fatty acid monoesters, which are nonvolatile compounds, were also detected as m/z peaks observed from 800 to 2300. Although the protonated molecular ion of tocopherol acetate was not detected in ionization by ultrasonic mist, it was detected by ultrasonic mist–DART-MS even in the emulsion. It was not necessary to dissolve a sample completely to detect its ions. This method enabled us to obtain the composition of pharmaceutical applications simply and rapidly.

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Graphical Abstract ?

     

Structural properties and antioxidant activities of polysaccharides isolated from sunflower meal after oil extraction

Making full use of sunflower seeds, including oil and the polysaccharides extracted from the meals which oil has been extracted, is one way to enhance their industrial value. Such meals contain abundant polysaccharides; however, the application of polysaccharides isolated from sunflower remaining meals after oil extraction has not been investigated. In this study, polysaccharides were isolated by alkali from sunflower meals after different oil extraction processes, and their structural properties and antioxidant activities were compared. The results indicated that these polysaccharides displayed significant variability in monosaccharide composition and molecular weight. Differences in structural properties could result in differences in functional antioxidant properties. The polysaccharide (SPHE-1) obtained from the meals after traditional hexane extraction exhibited the best antioxidant activities, including DPPH free radical-scavenging assay and hydroxyl radical scavenging activity among all the polysaccharide fractions. The research provides valuable information for making efficient use of sunflower seeds in the food industry.     

复合酶法提取大蒜多糖及其抗氧化活性研究

用复合酶法对大蒜多糖的提取工艺进行研究,并考察了不同浓度沉淀多糖的抗氧化活性;以多糖提取得率为指标,苯酚-硫酸法测定多糖的总糖含量,采用正交实验确定纤维素酶、木瓜蛋白酶和果胶酶的最佳配比,然后在单因素试验的基础上,采用正交实验优化复合酶提取大蒜多糖的最佳工艺;分别用羟基自由基(·OH)和1-二苯基-2-苦基肼基(DPP...     

Determination of organic UV filters in water by stir bar sorptive extraction and direct analysis in real-time mass spectrometry

A screening method for analyzing environmental waters contaminated with UV filters using direct analysis in real-time mass spectrometry (DART-MS) was developed. To demonstrate the suitability of DART-MS a test set of seven organic UV filters, namely benzophenone-3 (BP-3), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), 4-t-butyl-4′-methoxydibenzoylmethane (BM-DBM), homomethyl salicylate (HMS), 2-(ethylhexyl) salicylate (EHS), octocrylene (OC), and 4-methylbenzylidene camphor (4-MBC), was defined. In the first step, standard solutions of the analytes prepared in methanol were investigated in order to determine optimum parameters for the DART-MS. Because of the very low concentrations of UV filters expected in environmental water samples, a pre-concentration step using stir bar sorptive extraction was performed. DART-MS allows the direct, simple and rapid semi-quantitative analysis of the analytes enriched on the surface of the polydimethylsiloxane-coated stir bars. The optimized method provided calibration curves with correlation coefficients R > 0.959, repeatability from 5% (for 4-MBC) to 30% (for BM-DBM) relative standard deviation and limits of detection lower than 40 ng L⁻¹ for all analytes. Finally, real lake water samples from locations with typical leisure activities were analyzed. Results obtained with the developed DART-MS method were cross-checked by confirmatory analysis using thermodesorption gas chromatography mass spectrometry (TD-GC-MS). Thereby, it could be demonstrated that both analytical methods provide comparable concentrations for the UV filters in the lake water samples.     

An overview on the application of ultrasound in extraction,separation and purification of plant polysaccharides

In view of the recent emphasis on non-conventional chemistry, application of ultrasound in isolation of plant polysaccharides represents a viable alternative to traditional extraction processes. This review presents an extensive literature survey of ultrasound-assisted extraction of polysaccharides from different plant materials, particularly herbal plants and secondary agricultural plant sources. Targeted, multistep methods were applied with respect to differences in the types of polysaccharides and their location in plant cell walls. The effectiveness of the methods was evaluated according to yield and properties of the isolated polysaccharides in comparison to classical extraction methods. Substantial shortening of extraction time, reduction of reagent consumption and/or extraction temperature are the most important advantages of the ultrasonic treatment. In combination with sequential extraction steps using different solvents, sonication was shown to be effective in separation and/or purification of polysaccharides. The disadvantages of the sonication treatment, such as degradation and compositional changes of the polysaccharide preparations are discussed as well.