Gas Chromatography-triple Quadrupole Mass Spectrometry Research Articles

Effects of micellar casein concentrate purity and milk fat on sulfur/eggy flavor in ultrapasteurized milk-based beverages

Our objectives were to determine the level of milk-derived whey protein (MDWP) removal necessary to achieve no detectable sulfur/eggy flavor in ultrapasteurized fat-free micellar casein concentrate (MCC) beverages (6.5% protein) and in the same beverages containing 1 and 2% milk fat. Micellar casein concentrate with 95% MDWP removal was produced from skim milk (50°C) with a 3×, 3-stage ceramic microfiltration (MF) process using 0.1-µm pore size graded permeability membranes (n = 3). In experiment 1, MCC-based beverages at about 6.5% (wt/wt) true protein were formulated at a fat content of 0.15% fat (wt/wt) at 4 different levels of MDWP removal percentages (95.2%, 91.0%, 83.2%, and 69.3%). In experiment 2, a similar series of beverages at 3 MDWP removal percentages (95.2%, 83.2%, and 69.3%) with 0.1, 1, and 2% fat content were produced. The purity (or completeness of removal of whey protein by MF) of MCC was determined by the Kjeldahl method and sodium dodecyl sulfate (SDS)-PAGE. Sensory properties of beverages were documented by descriptive sensory analysis, and volatile sulfur compounds were evaluated using solid-phase microextraction followed by gas chromatography-triple quadrupole mass spectrometry. The purity of MCC measured by the Kjeldahl method (casein as a percentage of true protein) was higher after thermal treatment than before, whereas MCC purity evaluated by SDS-PAGE was unchanged by heat treatment. The purity of MCC had an effect on the flavor profile of thermally processed beverages at 6.5% protein made with fresh liquid MCC. No sulfur/eggy flavor was detected in MCC beverages when 95% of the MDWP was removed (MCC purity about 93 to 94%) from skim milk by microfiltration at 0.1, 1, and 2% fat. As the fat content of 6.5% protein beverages produced with MCC increased, sulfur/eggy flavor intensity and hydrogen sulfide concentration decreased. However, the effect of increasing milk fat on reducing sulfur/eggy flavor in MCC-based beverages at 6.5% protein was less than that of increasing MDWP removal from MCC. Sulfur off-flavors in neutral-pH dairy protein beverages can be mitigated by use of high-purity MCC or by incorporation of fat in the beverage, or both.

Analysis of six aromatic amines in the mainstream smoke of tobacco products

Aromatic amines are a class of carcinogenic compounds in tobacco smoke that are listed on the FDA list of harmful and potentially harmful constituents (HPHCs). A method using solid-phase microextraction-coupled to gas chromatography-triple quadrupole mass spectrometry (SPME headspace GC–MS/MS) was developed and validated for the quantitative determination of six aromatic amines, including 1-aminonaphthalene (1-AN), 2-aminonaphthalene (2-AN), 3-aminobiphenyl (3-ABP), 4-aminobiphenyl (4-ABP), o-toluidine (o-TOL), and o-anisidine (o-ANI), in the mainstream smoke of cigarettes, cigars, and heated tobacco products. The method developed here combines high sensitivity with simple sample preparation and has demonstrated satisfactory linearity for all six aromatic amines with correlation coefficients greater than 0.9994. The limits of detection range and the limits of quantitation range were 12–96 pg/mL and 41–320 pg/mL, respectively. Their recoveries and coefficients of variation (CV%) were 90–112% and 2.1–6.6%, respectively. The new SPME headspace GC/MS/MS method has been successfully applied to measure the contents of the six aromatic amines in the mainstream smoke of cigarettes, cigars, and heated tobacco products.

The effect of flash vacuum cooling on the flavor of ultrapasteurized milk

Ultrapasteurization (UP) extends the shelf life of milk. Direct steam injection (DSI) is commonly used for UP because milk is quickly heated and cooled. During this process, steam is directly injected into milk and removed by a vacuum cooler. Consumers do not prefer the flavor of DSI-UP milk compared with traditional high temperature short time (HTST) milk due to the higher cooked and eggy flavors of DSI-UP milk. The objective of this research was to characterize the effect of the vacuum cooler on the flavor of DSI-UP milk. Raw skim milk was pasteurized at 140°C for 2.3 s by DSI and homogenized at 20.7 MPa. By using a liquid sample port, steam-infused pasteurized milk was sampled after heating but before reaching the vacuum chamber. A septum was installed in the vacuum chamber to allow sampling of the removed volatiles by solid-phase microextraction (SPME) fiber followed by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) combined with a sulfur-selective flame photometric detector. Steam-infused milk and vacuum-cooled milk diluted to the same solids contents were evaluated by descriptive sensory analysis and volatile compound analysis. The entire experiment was replicated 3 times. Milks cooled by the vacuum cooler were lower in sweet aromatic, sulfur/eggy, and cooked flavors than milk sampled before the vacuum cooler. Volatile compounds removed by the vacuum cooler included the sweet aromatic flavor contributors furaneol, maltol, furfural, sotolon, 2-heptanone, γ-dodecalactone, γ-decalactone, and δ-decalactone, as well as the cooked and sulfur/eggy contributors hydrogen sulfide and dimethyl sulfide. The vacuum cooler applied during DSI-UP of milk is effective at removing steam and cooling UP milk, but this process may also remove important flavor compounds from fluid milk.

Breastfeeding during infancy and consumption of fish and dairy products are associated with chlorinated persistent organic pollutants in serum from Swedish adolescents

BackgroundFood is considered the predominant source of human exposure to chlorinated and brominated persistent organic pollutants (POPs). Exposure and potential sources of these compounds are less studied in adolescents. We aimed to investigate blood serum levels of chlorinated and brominated POPs in Swedish adolescents and to investigate associations with breastfeeding and food consumption. MethodsA national representative sample of adolescents (three age groups with mean age of 12, 15 and 18 years) (N=1096) were recruited between September 2016 and May 2017 in the study Riksmaten adolescents 2016-17. Diet was assessed using a web-based 24-h dietary recall method and frequency questions. Chlorinated POPs (including ten polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), dichlorodiphenyldichloroethylene (p,p'-DDE)) and three polybrominated diphenylethers (PBDEs) were analysed in blood serum using gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) analysis. Associations between breastfeeding duration during infancy and consumption of five food groups (i.e. fish and shellfish, dairy products, eggs, meat, fats and oils) and serum POP concentrations were investigated. ResultsHCB, p,p'-DDE, and CB118, 138, 153, 170, 180 and 187 were detected in most samples while the other analysed POPs were below limit of quantification in ≥60% of the samples. Longer breastfeeding time was associated with higher concentrations of p,p'-DDE, CB118, and CB138-187 (i.e. sum of CB138, 153, 170, 180, 187). Consumption of fish and shellfish was positively associated with concentrations of HCB and CB118. Consumption of dairy products was positively associated with concentrations of HCB and CB138-187. Egg consumption was positively associated with p,p'-DDE. ConclusionSerum concentrations of HCB, p,p'-DDE and PCBs in Swedish adolescents are comparable to concentrations in other European adolescent populations. Breastfeeding, fish, dairy products, and eggs are probable sources of chlorinated POP exposure in Swedish adolescents.

A new headspace solid-phase microextraction coupled with gas chromatography-tandem mass spectrometry method for the simultaneous quantification of 21 microbial volatile organic compounds in urine and blood

Mold growth can cause the development of several metabolites including microbial volatile organic compounds (mVOCs). These latter may be considered as potential biomarkers of fungal presence and have been detected in human biological matrices such as urine and blood. Exposure to molds and their metabolites (e.g., mVOCs, mycotoxins) in occupational settings, is responsible for several health effects. Thus, this exposure cannot be neglected and must be evaluated. Herein, a method has been developed to quantify 21 mVOCs in urine and human blood by headspace solid phase micro-extraction (HS-SPME) coupled with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). The parameters influencing the extraction process, such as the type of fiber, the incubation and extraction time and temperature and the desorption time, have been optimized to ensure better mVOCs extraction. The developed method showed good linearity over the concentration range of the compounds (R2 ˃ 0.995) for all the mVOCs in all the matrices. The low limits of detection (LOD) ranging from 0.7 to 417 ng/L in urine and from 1 to 507 ng/L in blood, make the developed methods sensitive and effective for biomonitoring of exposure at low levels. Recoveries, at low and high concentrations, were between 87% and 120% in urine and between 83% and 118% in blood. The repeatability and the intermediate precision in terms of coefficients of variation (CV%) was lower than 13% and 8.58% respectively for all compounds in all matrices. These values show satisfactory accuracy and precision of the developed method. Thus, this practical, simple, and sensitive method is well suited for the simultaneous quantification of target mVOCs.

Effects of Processing Method Changes in Main Volatile Compounds of Qixue Shuangbu Prescription by Needle Trap Device Coupled with Gas Chromatography-Triple Quadrupole Mass Spectrometry.

Qixue Shuangbu Prescription (QSP) has been widely applied in the treatment of chronic heart failure (CHF). Previous clinical studies have found that the efficacy of processed QSP was significantly enhanced in the treatment of CHF. We have identified and analyzed the nonvolatile components before and after processing of QSP, and predicted the mechanism of synergistic effect after processing in the treatment of CHF. However, the synergistic mechanism of processed QSP caused by the difference of volatile components was still unclear. In this study, we developed a method of needle trap device coupled with gas chromatography-triple quadrupole mass spectrometry to elucidate the difference of volatile components between crude and processed QSP. The established method has been used to identify 104 volatile compounds in crude and processed QSP. The results of multivariate data showed 38 differential compounds were screened as potential markers, which would further explain the mechanism of processing synergistic effect of processed QSP. This study successfully developed the method to elucidate its processing mechanism based on the difference of volatile compositions between crude and processed QSP for the first time, and it would provide a novel analytical strategy for the impacts of different processing methods on main volatile compounds in traditional Chinese medicine.

Simultaneous determination of 11 volatile perfluorinated compound precursors in textiles using gas chromatography-triple quadrupole mass spectrometry

以甲醇为提取溶剂,超声辅助提取纺织品中的全氟化合物前体物,建立了一种气相色谱-三重四极杆质谱(GC-MS/MS)法同时测定纺织品中11种挥发性全氟化合物前体物:4种氟调聚物醇(FTOHs)、3种氟调聚丙烯酸酯(FTAs)、2种全氟辛基磺酰胺(FOSAs)和2种全氟辛基磺酰胺乙醇(FOSEs)。考察了超声提取溶剂、提取温度和提取时间对提取效率的影响,最终确定用甲醇为提取溶剂,70 ℃下超声提取60 min,目标物经VF-WAXms毛细管柱(30 m×0.25 mm×0.25 μm)程序升温分离,GC-MS/MS多反应监测(MRM)模式检测,外标法定量。实验结果表明:11种挥发性全氟化合物前体物在10~500 μg/L范围内线性关系良好,相关系数(r)均不低于0.9984;以信噪比为3计算,检出限(LOD)为0.002~0.04 mg/kg;以信噪比为10计算,定量限(LOQ)为0.006~0.1 mg/kg;不同材质纺织品中,11种挥发性全氟化合物前体物在高、中、低3个添加水平下的回收率为73.2%~117.2%,相对标准偏差(RSD)为0.1%~9.4%(n=6)。该方法前处理简单,定性、定量准确,灵敏度高,重现性好,可有效用于纺织品中11种挥发性全氟化合物前体物的同时检测。实际样品分析发现,当前全氟化合物前体物已被应用于纺织品整理当中。该方法的建立对我国纺织品中全氟化合物前体物风险物质的管控和检测标准的制定具有一定的理论和现实意义。

Quantitative Determination of p-Cymene, Thymol, Neryl Acetate, and β-Caryophyllene in Different Growth Periods and Parts of Eupatorium fortunei Turcz. by GC-MS/MS.

Eupatorium fortunei Turcz. is a widely used Chinese herbal medicine in China. In this study, a gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) method was developed and validated to simultaneously determine the contents of p-cymene, thymol, neryl acetate, and β-caryophyllene in roots, stems, and leaves of Eupatorium fortunei Turcz. harvested at different growth periods. All four constituents could be detected in leaves, three could be detected in stems except β-caryophyllene, and only thymol could be detected in roots. The order of the total contents of four constituents in different parts was leaves > stems > roots. It indicated that the leaves could be the proper medicinal parts of Eupatorium fortunei Turcz. The content of four constituents in leaves varied a lot among different growth periods and showed an M-shaped change trend with the growth of Eupatorium fortunei Turcz. The four constituents accumulated to the highest values in early July followed by mid-September. Accordingly, the best harvest time of Eupatorium fortunei Turcz. is early July and mid-September.

Quantification of nitrogen markers in crude oils using gas chromatography-triple quadrupole mass spectrometry

This study presents optimization and validation of a novel gas chromatography-triple quadrupole mass spectrometry (GC–MS/MS) method for the determination of nitrogen-containing heterocyclic aromatic compounds assumed to be geochemistry markers in crude oils. Parameters for the operation of tandem mode MS/MS, i.e., precursor and product ions and collision energy (CE), were optimized, and an MS/MS instrument was used to provide multiple reaction monitoring (MRM) data. Matrix effects were evaluated, and matrix-matched calibration was used for quantification. The method was validated under optimal conditions, and all analytical parameters demonstrated satisfactory results. Indeed, the linearity (R2) in the tested calibration range was ≥ 0.99 for all compounds. Limits of detection ranged from 0.0014 to 0.0383 μg mL−1, and the limits of quantitation of the target compounds were in the range 0.0042 to 0.1275 μg mL−1. Average recoveries of the analytes were between 78.6% and 117%, with intraday and interday precisions lower than 9.4% and 19.5%, respectively, for all N-markers at spiking levels of 0.01, 0.1 and 0.5 µg mL−1. The method was successfully applied to eight crude oil samples for geochemical evaluation of maturity, migration and depositional ambient conditions without preliminary fractionation steps. The results indicated that the GC–MS/MS method is promising for fast, easy and efficient quantitative analysis of N-markers in crude oils, and it minimizes sample preparation time and solvent consumption.

Simultaneous determination of tetra-, penta- and hexachlorobutadienes in shellfish by gas chromatography-triple quadrupole mass spectrometry

Polychloro-1,3-butadienes (polyCBDs) are attracting increasing concern due to their high toxicity. However, research on multiple polyCBDs in aquatic biota is still extremely limited. In this study, a sensitive method for simultaneous determination of nine polyCBD (Cl4–Cl6) congeners, including six tetrachlorobutadiene (TeCBD) isomers, two pentachlorobutadiene (PeCBD) isomers, and hexachlorobutadiene (HCBD), in shellfish was developed based on accelerated solvent extraction (ASE), solid-phase extraction (SPE) clean-up and gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Low method limits of detection (MDLs) in the range 0.03–0.21 ng/g dry weight for target analytes with satisfactory recoveries (47.7 %–70.6 %) were achieved. The valid method was then applied to analyze nine polyCBDs congeners in 42 shellfish and 11 fish samples collected from markets in eight coastal cities, China. Trace HCBD was detected in 14 samples, while TeCBDs and PeCBDs were under the MDLs in all the samples, indicating little contamination of these pollutants in the marketed shellfish and fish in China. Multiple polyCBDs especially TeCBDs and PeCBDs were firstly involved in the proposed method and investigation here, which lay the groundwork for future research on the environmental behavior and exposure risks of polyCBDs in aquatic biotas.

Determination of hydrazine in prednisolone by derivatization-gas chromatography-triple quadrupole mass spectrometry

泼尼松龙是一种广泛用于临床治疗的肾上腺糖皮质激素药物,其中联氨的残留会直接影响用药安全,但目前国内外还没有出台相应的法律法规和标准来管控药物中联氨的残留限值。联氨具有强极性和强还原性,理化性质很不稳定,易被氧化,又因缺少发色团,相对分子质量太小,检测起来难度很大,需引入一种衍生化试剂,降低其极性,生成相对分子质量较大且理化性质稳定的衍生产物。该研究通过优化衍生化试剂、色谱-质谱条件、溶剂体系和衍生化条件,建立了衍生化-气相色谱-三重四极杆质谱法(GC-MS/MS)测定泼尼松龙中联氨残留的方法,并进行了方法学验证,结果满意。称取1 g泼尼松龙样品置于10 mL具塞离心管中,加入稀释溶剂(甲醇-二氯甲烷(14:23, v/v))至刻度线,涡旋振荡至样品完全溶解后,吸取100 μL置于进样小瓶中,再加入丙酮900 μL,涡旋振荡混匀,样品在丙酮-稀释溶剂(9:1, v/v)中同时完成稀释和衍生化反应后,再经GC-MS/MS检测分析。该研究的衍生化反应无需在添加冰乙酸和超声条件下进行,也无需再添加其他试剂进行萃取操作,联氨与丙酮可瞬间发生衍生化反应,直接实现泼尼松龙中联氨的快速测定。结果表明,联氨在1~12 μg/L范围内线性关系良好,线性相关系数(r2)为0.9999;检出限、定量限分别为0.03和0.10 mg/kg;进样精密度(relative standard deviation, RSD)为1.10%。加标回收率和重复性良好,加标水平分别为1、6、12 μg/L时的回收率为96.15%~96.46%,对应的RSD值为1.77%~2.12%。中间精密度良好,不同时间、不同人员在同一台仪器上测定结果的RSD值为1.77%。方法耐用性良好,通过改变色谱条件来研究检测结果受影响程度大小,在原条件、初始柱温±5 ℃、升温速率±2 ℃/min、柱流量±0.1 mL/min的条件下分别对加标6 μg/L的样品溶液中的联氨含量进行检测,检测结果的RSD值为2.58%。应用建立的方法测定泼尼松龙市售标准品和某药企提供的9个不同批次的泼尼松龙样品,均未检出联氨。该方法操作简便、准确可靠、灵敏度高、选择性好,可用于泼尼松龙中联氨的检测。

Modified dispersive solid-phase extraction and cleanup followed by GC-MS/MS analysis to quantify ultraviolet filters and synthetic musk compounds in soil samples.

A simple method for the analysis of 13 synthetic musk compounds and six ultraviolet filters in soil samples was developed using a modified dispersive solid-phase methodology known as "Quick, Easy, Cheap, Effective, Rugged and Safe," followed by gas chromatography-triple quadrupole mass spectrometry. The methodology was validated by assessing linearity ranges, detection limits, precision, and accuracy. The method detection limit ranged between 0.01 and 10.00ng/g dry weight and accuracy from 81 to 122%. A good precision was achieved, with relative standard deviation <10%. The applicability of the methodology was tested using different types of soils. Both synthetic musks and ultraviolet filters were detected in all soil samples. The most frequently detected compounds were benzophenone, octocrylene, 2-ethylhexyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-methoxycinnamate, and galaxolide. Higher levels were detected for benzophenone (maximum value of 158ng/g dry weight) and octocrylene (137ng/g dry weight). In comparison with conventional techniques, this method uses lower amounts of solvents and sorbents, producing less waste ("greener" technique) and comparable performances. In addition, it presents as main advantages the simplicity, speed (short extraction/cleaning time), low cost, and minimum handling of extracts, which can minimize the possibility of samples cross-contamination.

Determination of 118 pesticide residues in dried wolfberry by gas chromatography-triple quadrupole mass spectrometry in dynamic multiple reaction monitoring mode

枸杞中丰富的营养物质深受广大消费者喜爱,但也极易受到病虫侵害,农药残留问题引起了人们的广泛关注。基质干扰是微量分析的一个难点,高灵敏度和高选择性的色谱-串联质谱技术是复杂基质中微量分析强有力的工具,动态扫描监测模式的优越性逐渐取代传统的多反应监测扫描模式,简便、快速、省时的QuEChERS前处理方法已被广泛应用于食品的农药残留检测中。采用改良QuEChERS法结合动态多反应监测模式(dMRM),建立了同时检测枸杞干果中118种农药残留的气相色谱-三重四极杆质谱分析方法。实验比较了不同加水量、提取溶剂、提取过程中温度提取条件,以及无水硫酸镁吸水剂、乙二胺-N-丙基硅烷化硅胶PSA、十八烷基硅烷键合硅胶C18净化填料添加量时农药的回收率,确定出最优前处理方法。结果表明,5 g样品经10 mL超纯水复水,用10 mL乙腈浸提,于-18 ℃冷冻10 min后,用缓冲体系盐包提取后,经800 mg无水硫酸镁、150 mg PSA、150 mg C18混合填料净化,基质匹配外标法定量。118种农药在一定范围内线性关系良好,相关系数R2≥0.9923,检出限和定量限分别为0.006~28.344 μg/kg和0.021~94.480 μg/kg, 4个添加水平的回收率为64.97%~126.21%, RSDs均小于19%(n=6)。基质效应考察结果表明,82%的农药呈现为基质增强效应,其他为基质抑制效应;9%的农药表现为强基质效应,其他为中等或弱基质效应;采用基质匹配标准曲线校正,可有效降低基质效应的影响。应用建立的方法测定10批枸杞样品,全部样品有农药检出,共检出农药22种。该方法操作简便快速,准确可靠,适用于枸杞干果中农药多残留的日常检测和快速筛查。

Metabolic profiling of 19 amino acids in triptolide-induced liver injured rats by gas chromatography-triple quadrupole mass spectrometry.

The liver is an important organ for amino acid metabolism, and its damage can be reflected in the changes of amino acid level in the body. Triptolide (TP) has broad anti-inflammatory and anti-tumor activities, but its clinical application is limited due to hepatotoxicity. In this work, a simple, accurate and sensitive gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS/MS) method was developed and validated for evaluating the serum levels of amino acids from control and TP-induced liver injured rats, and chemometric analysis was employed for amino acid metabolic profiles analysis. It was found that 11 amino acids showed significant changes after TP administration, and they were mainly involved in 5 metabolic pathways that are phenylalanine, tyrosine and tryptophan biosynthesis, alanine, aspartate and glutamate metabolism, glutamine and glutamate metabolism, phenylalanine metabolism and arginine biosynthesis. Five amino acids including tyrosine, glutamine, glutamic acid, tryptophan and alanine were identified as biomarkers of TP hepatotoxicity by further analysis. These results indicated that the novel amino acid metabolic profiling study based on the GC-QqQ-MS/MS provided not only exact concentrations of serum amino acids, but also a prospective methodology for evaluation of chemically induced liver injury.

Determination of multi-pesticide residues in vegetable products using a “reduced-scale” Quechers method and flow-modulated comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry

The aim of the present research was the development of an analytical method for the determination of multi-pesticide residues (88 target analytes) in four vegetable products (tomatoes, cucumbers, sweet red peppers and iceberg lettuce) using a “reduced-scale” QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction method and flow-modulated comprehensive two-dimensional gas chromatography-triple quadrupole mass spectrometry. In particular, the suitability of flow modulation [with relatively high second-dimension gas flow conditions (8 mL min−1)] for trace analyte determination was evaluated.The samples were prepared according to the QuEChERS procedure as reported by the official European Union method, namely EN 15662:2018, based on the use of 3 g of vegetable product. Matrix-matched calibration processes were carried out for all the samples. The figures-of-merit determined were recovery, linearity, precision, limits of detection (LoDs), and limits of quantification (LoQs). Specifically, recoveries were in the 53-160% range, regression coefficients were between 0.9156 and 0.9999, the LoDs were in the 0.1-6.3 μg kg−1 range, the LoQs were in the 3.0-21.0 μg kg−1 range, and coefficients of variation were between 1 and 28% (at the 50 μg kg−1 level).

Hydrophilic interaction liquid chromatography for removal of pesticide residues in ginseng extracts

亲水作用液相色谱法(HILIC)是一种用于改善强极性物质的保留和分离选择性的方法,广泛应用于药物分析、代谢组学、蛋白质组学等领域。该文利用农药分子与皂苷成分在HILIC上的保留行为差异,开发了一种农药残留脱除方法。以市售高纯人参提取物为例,该文评价了农药分子和人参皂苷在亲水色谱柱上的保留行为,并考察了上样量、淋洗体积、上样体积等因素对农残脱除效果的影响。实验结果证明:7种人参皂苷由于糖链上的羟基与亲水色谱固定相上的羧基形成氢键作用而具有较强保留,而农药分子由于亲水性较差且相对分子质量较小,保留很弱,从而一步实现了7种人参皂苷的富集与14种农残的脱除。在优化所得的最佳脱除工艺条件下,最终制备得到的人参总皂苷样品中,总皂苷的含量由59.87%提高到69.61%;总皂苷的回收率为94.4%;通过气相色谱-三重四极杆质谱(GC-MS/MS)对样品中的农残进行定量检测,发现原人参提取物中14种农残均得到了有效脱除,其中5种含量降至0.05 mg/kg以下,9种完全脱除。本研究是亲水色谱在中药提取物中农残脱除领域的应用,为天然产物的精制提供了一种新的技术手段,该技术对人参提取物中的农残脱除率高、人参总皂苷回收率高且安全、高效、无污染,为高品质人参提取物的研制提供了新的思路。

Determination of organic sulfur markers in crude oils by gas chromatography triple quadrupole mass spectrometry

Organic sulfur compounds, such as benzothiophene and dibenzothiophene, are present in crude oils, and specific isomers of these classes are known to be geochemical markers of maturity, lithology and biodegradation. Thus, knowledge of the individual concentrations of these target molecules enables us to characterize petroleum basins for better exploration. In this work, a simple and effective gas chromatography–triple quadrupole mass spectrometry method without preliminary fractionation was developed and validated for the determination of 14 organic sulfur compounds assumed to be geochemical markers for crude oils. The research was focused on the optimization of a highly selective GC-based analytical strategy using triple quadrupole MS in multiple reaction monitoring. Sample preparation was carried out by simple dilution in DCM. The method was validated, and the following parameters were expressed in terms of intraday precision: linearity, limit of detection, accuracy and precision. The limit of detection ranged from 0.005 μg mL−1 (benzothiophene) to 0.159 μg mL−1 (benzonaphthothiophene). Intraday assay precision was lower than 20% in all cases. Recoveries ranged from 78.2% (1,4-dimethyldibenzothiophene) to 117% (2,4,7-trimethyldibenzothiophene). After validation, the procedure was successfully applied to the determination of S-markers in 8 crude oil samples, and the method was determined to be precise, accurate, and suitable. Diagnostic ratios based on benzothiophenes to dibenzothiphenes were applied as tools to evaluate maturity, biodegradation and depositional ambient conditions. A cross-plot of methyldibenzothiophene versus dimethyldibenzophene ratio was utilized to classify oils according to their maturity.

Change of benzo(a)pyrene during frying and its groove binding to calf thymus DNA

Benzo[a]pyrene (BaP), a prototype of polycyclic aromatic hydrocarbons (PAHs) with potential mutagenicity, toxicity and carcinogenicity, is ubiquitous in deep-fried foods. Herein, the changes in eight specific PAHs (PAH8) concentration in sunflower oil during frying were investigated by gas chromatography-triple quadrupole-mass spectrometry (GC-QqQ-MS). PAH8 concentrations in sunflower oil were 23.92–27.82 μg kg−1 and increased with increasing frying time. The detected BaP levels were 3.64–4.00 μg kg−1, exceeding the upper limit (2 μg kg−1) set by European Union (EU), though below the limiting value (10 μg kg−1) in China. The interaction between BaP and calf thymus DNA (ctDNA) was explored through various spectroscopic methods and molecular docking. Melting studies, denaturation experiments, ionic strength effects and viscosity measurements indicated that BaP interacted with ctDNA primarily via groove binding as evidenced by circular dichroism analysis and molecular docking. Further gel electrophoresis assays suggested that DNA was damaged at high levels of BaP.

A Validated Method for Quantification of Fatty Acids Incorporated in Human Plasma Phospholipids by Gas Chromatography-Triple Quadrupole Mass Spectrometry.

Fatty acids (FA) are important mediators of health maintenance and disease risk. Optimal quantification assays of FA in high and low abundance as well the identification of 13C-labeled tracers to monitor FA metabolism are of major interest. The article on hand reports about the development and validation of a gas chromatography (GC)–triple quadrupole mass selective detection (GC-TQMS) method for absolute quantification of FA in human plasma phospholipids (hpPL). The quantification of the calibration solution by GC–flame ionization detection (GC-FID), with the introduction of a correction factor, allows the direct comparison of individual FA concentrations in hpPL by GC-TQMS. Specificity, sensitivity, and reproducibility are achieved by optimized chromatographic separation and employment of GC-TQMS. The inter-method comparison between GC-FID and GC-TQMS concentrations revealed good comparability for 27 FA. A full validation has been performed with linearity over 4 magnitudes, a limit of detection of 0.18–38.3 fmol on column, a recovery of 83.6–109.6%, and intraday and interday precision data meeting the criteria of EMA and FDA guidelines. The method includes the absolute quantification of 58 positional and geometrical (cis/trans) isomeric FA in hpPL in the concentration range of 1–3000 nmol/mL, covering also low abundant positional cis/trans isomers. Results obtained from both methods are highly comparable, and selectivity and sensitivity are improved by using GC-TQMS. Additionally, we show here that calculation of 13C-labeled C16:0 tracer/tracee ratios in hpPL in human isotope enrichment studies is possible.

Accurate and ultrasensitive determination of 72 parent and halogenated polycyclic aromatic hydrocarbons in a variety of environmental samples via gas chromatography–triple quadrupole mass spectrometry

Polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (XPAHs) are ubiquitous in various environmental media. Analytical problems, however, make it difficult to accurately determine their concentrations. To develop a satisfactory analytical method suitable for a diversity of PAHs and XPAHs in multiple environmental samples, we evaluated three commercial analytical columns (DB-5MS, Select PAH, and Rxi-PAH) for better chromatographic separation and optimized the analytical conditions for gas chromatography–triple quadrupole mass spectrometry (GC-MS/MS). Comparison of the abilities of the columns to separate peaks revealed that the Rxi-PAH was the best column for both PAH and XPAH analyses. Optimization of analytical conditions for GC-MS/MS resulted in sensitivities for PAHs and XPAHs that were 4.2-fold–2600-fold higher than the sensitivities of GC-high-resolution MS (GC-HRMS) (an example of a traditional analytical method). Although there were no statistically significant differences between the instrumental detection limits (IDLs) of PAHs and XPAHs measured by GC-HRMS, the IDLs of XPAHs were significantly lower than those of PAHs when measured by GC-MS/MS. This difference could be attributed to the unique ionization patterns of XPAHs in the GC-MS/MS analysis, which suppressed background noise and increased the analytical sensitivity. Analyses of PAHs and XPAHs in grilled chicken, vehicle exhaust, sea sediment, ambient air, and indoor dust via the analytical method optimized in this study revealed that the proposed method was sufficiently sensitive, comprehensive, and versatile for risk assessment purposes, and could eliminate interferences associated with the co-elution of target PAHs and XPAHs.