气相色谱-质谱法分析啤酒中酒花香气成分

利用顶空固相微萃取-气相色谱质谱技术(HS-SPME/GC-MS)建立了定量分析啤酒中19种源自酒花的微量香气成分的方法。研究了不同萃取头、萃取时间、萃取温度对萃取效果的影响,最终确定HS-SPME最佳萃取条件为采用PDMS萃取头对啤酒样品在50℃下萃取60 min。在最佳萃取条件下,采用啤酒为基体以减少基体干扰,建立标准曲线,随后在SIM模式下以萜品烯-4-醇为内标定量测定了啤酒中酒花香气物质的含量。19种物质的回收率在81.2%～116.8%之间,相对标准偏差(RSD)低于9.8%,在5个加标浓度下,R2大于0.99。相比于传统方法,本方法所需样品量少、灵敏度高、操作过程简便,能准确的检测出啤酒中酒花香气物质的含量。     

High extraction efficiency fiber coated with calix[4] open-chain crown ether for solid-phase microextraction of polar aromatic and aliphatic compounds

The calix[4] open-chain crown ether, 5,11,17,23-tetra-tert-butyl-25,27-di(2-allyloxyethoxyl)-26,28-dihydroxycalix[4]arene was synthesized and used for preparation of solid-phase microextraction (SPME) fibers of enhanced extraction efficiency. The new SPME coating made from calix[4] open-chain crown ether and hydroxyl-terminated silicone oil was developed with the aid of vinyltriethoxylsilane as bridge using sol-gel method and cross-linking technology. The efficiency of the novel fiber in the extraction of polar aromatic and aliphatic compounds, such as phenols, alcohols, and volatile fatty acids, was also investigated. Due to the introduction of the polar open-chain crown ether in calix[4]arene molecules, the calix[4] open-chain crown ether fiber showed much better selectivity and sensitivity to these polar compounds in comparison with calix[4]arene fiber. It also had superior extraction efficiency when compared to commercial poly(dimethylsiloxane)-divinylbenzene and polyacrylate fibers. Parts per billion to parts per trillion level detection limits were achieved for most of the analytes through SPME in conjunction with GC and flame ionization detector. The linear ranges were two to four orders of magnitude, and the RSD values were below 7% for all analytes. The novel fiber was applied to determine volatile alcohols and fatty acids in wine samples. The volatile-free wine prepared in this work was used to assure similar chemical environment for analytes in both calibration solutions and in real wine samples, thus compensating for possible matrix interferences. The established internal standard method using 4-methyl-2-pentanol as internal standard showed satisfactory accuracy and precision.     

On-line monitoring of continuous beer fermentation process using automatic membrane inlet mass spectrometric system

A fully automatic membrane inlet mass spectrometric (MIMS) on-line instrumentation for the analysis of aroma compounds in continuous beer fermentation processes was constructed and tested. The instrumentation includes automatic filtration of the sample stream, flushing of all tubing between samples and pH control. The calibration standards can be measured periodically. The instrumentation has also an extra sample line that can be used for off-line sample collection or it can be connected to another on-line method. Detection limits for ethanol, acetic acid and eight organic beer aroma compounds were from μg l⁻¹ to low mg l⁻¹ levels and the standard deviations were less than 3.4%. The method has a good repeatability and linearity in the measurement range. Response times are shorter than or equal to 3 min for all compounds except for ethyl caproate, which has a response time of 8 min. In beer aroma compound analysis a good agreement between MIMS and static headspace gas chromatographic (HSGC) measurements was found. The effects of different matrix compounds commonly present in the fermentation media on the MIMS response to acetaldehyde, ethyl acetate and ethanol were studied. Addition of yeast did not have any effect on the MIMS response of ethanol or ethyl acetate. Sugars, glucose and xylose, increased the MIMS response of all studied analytes only slightly, whereas salts, ammonium chloride, ammonium nitrate and sodium chloride, increased the MIMS response of all three studied compounds prominently. The system was used for on-line monitoring of continuous beer fermentation with immobilised yeast. The results show that with MIMS it is possible to monitor the changes in the continuous process as well as delays in the two-phase process.     

Headspace solid-phase microextraction combined with mass spectrometry as a powerful analytical tool for profiling the terpenoid metabolomic pattern of hop-essential oil derived from Saaz variety

Hop (Humulus lupulus L., Cannabaceae family) is prized for its essential oil contents, used in beer production and, more recently, in biological and pharmacological applications. In this work, a method involving headspace solid-phase microextraction and gas chromatography-mass spectrometry was developed and optimized to establish the terpenoid (monoterpenes and sesquiterpenes) metabolomic pattern of hop-essential oil derived from Saaz variety as a mean to explore this matrix as a powerful biological source for newer, more selective, biodegradable and naturally produced antimicrobial and antioxidant compounds. Different parameters affecting terpenoid metabolites extraction by headspace solid-phase microextraction were considered and optimized: type of fiber coatings, extraction temperature, extraction time, ionic strength, and sample agitation. In the optimized method, analytes were extracted for 30 min at 40°C in the sample headspace with a 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane coating fiber. The methodology allowed the identification of a total of 27 terpenoid metabolites, representing 92.5% of the total Saaz hop-essential oil volatile terpenoid composition. The headspace composition was dominated by monoterpenes (56.1%, 13 compounds), sesquiterpenes (34.9%, 10), oxygenated monoterpenes (1.41%, 3), and hemiterpenes (0.04%, 1) some of which can probably contribute to the hop of Saaz variety aroma. Mass spectrometry analysis revealed that the main metabolites are the monoterpene β-myrcene (53.0 ± 1.1% of the total volatile fraction), and the cyclic sesquiterpenes, α-humulene (16.6 ± 0.8%), and β-caryophyllene (14.7 ± 0.4%), which together represent about 80% of the total volatile fraction from the hop-essential oil. These findings suggest that this matrix can be explored as a powerful biosource of terpenoid metabolites.     

Elimination of matrix effects for headspace solid-phase microextraction of important volatile compounds in red wine using a novel coating

In this paper, hydroxy-terminated silicone oil-butyl methacrylate-divinylbenzene (OH-TSO-BMA-DVB) copolymer was first synthesized and used as stationary phase with the aid of γ-methacryloxypropyltrimethoxylsilane (KH-570) as bridge in solid-phase microextraction (SPME) using sol–gel method and cross-linking technique. It has high extraction efficiency for both polar alcohols and fatty acids and nonpolar esters in comparison with commercial PDMS, PDMS-DVB and PA fibers. A simple and sensitive headspace SPME-gas chromatography (HS-SPME-GC) method using the novel fiber was presented for the simultaneous analysis of both polar alcohols and fatty acids and nonpolar esters in wine. To check the matrix effects, various model wine matrices, including distilled water; 11.5% ethanol/water (v/v) solution; a concentrated synthetic wine; a ‘volatile-free’ wine and a real wine were investigated in detail. Matrix effects were compensated for by using internal standard method and selecting the ‘volatile-free’ wine as working standard. The method presented in this study showed satisfactory linearity, precision, detection limits and accuracy. The recoveries obtained ranged from 85.87 to 104.2%, and the relative standard deviation values were below 9%. The results obtained indicated that the present method is a validated and accurate procedure for the simultaneous determination of both polar and nonpolar aroma compounds in wine.     

Preparation and application of in-fibre internal standardization solid-phase microextraction

The in-fibre standardization method is a novel approach that has been developed for field sampling/sample preparation, in which an internal standard is pre-loaded onto a solid-phase microextraction (SPME) fibre for calibration of the extraction of target analytes in field samples. The same method can also be used for in-vial sample analysis. In this study, different techniques to load the standard to a non-porous SPME fibre were investigated. It was found that the appropriateness of the technique depends on the physical properties of the standards that are used for the analysis. Headspace extraction of the standard dissolved in pumping oil works well for volatile compounds. Conversely, headspace extraction of the pure standard is an effective approach for semi-volatile compounds. For compounds with low volatility, a syringe-fibre transfer method and direct extraction of the standard dissolved in a solvent exhibited a good reproducibility (<5% RSD). The main advantage of the approaches investigated in this study is that the standard generation vials can be reused for hundreds of analyses without exhibiting significant loss. Moreover, most of the standard loading processes studied can be performed automatically, which is efficient and precise. Finally, the standard loading technique and in-fibre standardization method were applied to a complex matrix (milk) and the results illustrated that the matrix effect can be effectively compensated for with this approach.     

Development of headspace solid-phase microextraction-gas chromatography-mass spectrometry methodology for analysis of terpenoids in Madeira wines

A dynamic headspace solid-phase microextraction methodology was developed for analysis of varietal aroma compounds in must and Madeira wine samples, a spirit wine with an ethanol content of 18% (v/v). The factors with influence in the headspace solid-phase microextraction efficiency such as: fibre coating, extraction time and temperature, pH, ionic strength, ethanol content, desorption time and temperature, were optimised and the method validated. The best results were obtained for a 85 μm polyacrylate fibre, with a 60 min headspace for must and 120 min for wine samples, in a 2.4 ml sample at 40 °C with 30% of NaCl. The extract is injected in the splitless mode in a GC-MS Varian system, Saturn III, and separated on a Stabilwax capillary column. The linear dynamic range of the method covers the normal range of occurrence of analytes in wine with typical r² between 0.985 (β-ionone) and 0.998 (linalool) for musts and between 0.980 (α-terpineol) and 0.999 (linalool) for must and wine samples, respectively. For must samples the reproducibility ranges from 2.5% (citronellol) to 14.4% (nerolidol) (as R.S.D.), and from 4.8% (citronellol) to 14.2% (nerolidol) for wine samples. The analysis of spiked samples has shown that matrix effects do not significantly affect method performance. Limits of detection obtained are in low μg l⁻¹ range for all compounds analysed in this study.     

高通量固相萃取-超高效液相色谱-串联质谱法测定人尿中8种环境酚类内分泌干扰物

建立了人尿中8种环境酚类化合物的96孔板固相萃取-超高效液相色谱-串联质谱(96-well SPE LC-MS/MS)检测方法,其中包括7种双酚类化合物和三氯生。尿样解冻到室温,经β-葡萄糖醛酸苷肽酶/芳基磺酸酯酶37 ℃过夜酶解。实验比较了3种96孔板固相萃取柱和不同淋洗条件对人尿样的净化效果和目标化合物的回收率。结果显示,采用Oasis HLB 96孔板(60 mg)对样品进行萃取和用30%(v/v)乙腈水溶液进行淋洗净化的纯化效果最好。纯化后目标物用甲醇溶液洗脱,经氮气吹干,用0.5 mL甲醇-水(1∶1, v/v)溶液定容,目标化合物用UPLC-MS/MS进行检测。比较了2种分析柱(C₁₈和T3分析柱)以及不同的有机流动相对分离样品中目标物的影响。结果显示,以BEH C₁₈(100 mm×2.1 mm, 1.7 μm)作为分析柱,乙腈/水作为流动相,以流速0.3 mL/min梯度洗脱时,目标物的分离效果最好。质谱条件选择串联质谱负离子电喷雾(ESI^-)多反应监测模式(MRM)进行检测。对样品的基质效应进行评估发现,双酚A、双酚F、双酚S、双酚B和双酚AF的绝对基质效应为3.47%~15.32%,不需要补偿措施;四氯双酚A、四溴双酚A和三氯生的绝对基质效应分别是49.58%(中等基质效应)、71.99%和86.93%(强基质效应),均需要补偿效应。因此,该方法采用了一一对应的同位素内标法抵消基质效应。用6份实际尿样基质评估相对基质效应,8种内标的峰面积的相对标准偏差为3.63%~9.06%,说明相对基质效应稳定。在优化条件下,双酚A和双酚AF在0.50~50 μg/L内、四氯双酚A和双酚S在0.05~50 μg/L内、双酚F和四溴双酚A在0.01~50 μg/L内、双酚B在1.00~50 μg/L内、三氯生在5.00~200 μg/L内线性关系良好,相关系数大于0.9995。方法检出限为0.002~1.09 μg/L,定量限为0.007~3.63 μg/L。3个加标水平的加标回收率为81.0%~101.9%,日内精密度为0.4%~19.4%,日间精密度为2.5%~17.8%。应用该方法对2019-2020年采集的北京地区64份尿样进行测定,结果发现8种目标分析物中,除双酚B和双酚AF未检出外,其余均有检出,其中双酚A和双酚S的检出率最高,分别为100%和96.9%。三氯生、四溴双酚A、四氯双酚A和双酚F的检出率分别为57.8%、46.9%、23.4%和21.9%。尿样中8种目标物含量的中位值以降序排列分别为1.44 μg/L(三氯生)、0.69 μg/L(双酚A)、0.086 μg/L(双酚S)、0.0032 μg/L(四溴双酚A)、0.00050 μg/L (四氯双酚A)、0.00 μg/L(双酚F、双酚B和双酚AF)。以上尿样检测结果显示,北京市居民存在普遍的环境酚类化合物暴露,值得关注。该方法操作简单,定量准确,样品需求量小,有机试剂消耗少,适合大批量样本的测定。     

Matrix solid-phase dispersion extraction of organophosphorous pesticides from beeswax

Beeswax is a complex mixture of lipophilic compounds and other components such as aliphatic alcohols and carotenoids. Then, extraction and clean-up for pesticide analysis in beeswax is a challenge. In this work, a multiresidue method for the analysis of dichlorvos (DCV), diazinon, malathion, methyl parathion and coumaphos (CMF) in beeswax was developed. The proposed approach is based on matrix solid-phase dispersion extraction. The adsorbent for sample clean-up was studied and a simplex-centroid cubic statistical design was applied to evaluate pure solvents and their binary and ternary mixtures to elute the analytes. Finally, Florisil and ethyl acetate were chosen as solid support and eluting solvent, respectively. After extraction, pesticides were separated and detected by gas chromatography/mass spectrometry. The method achieved acceptable recoveries (70–85%; except for DCV, 24–38%) with relative standard deviations below 5%. The repeatability of the method was lower than 8% and interday variability was below 12%. The limit of detection (LOD) for the analytes varies between 0.2 and 2.6 µg?kg^?1 and limit of quantification from 0.93 to 8.8 µg?kg^?1. LOD reached for CMF was below the maximum residue limit allowed by the legislation of the United States and Canada.     

Matrix solid-phase dispersion extraction of carbadox and olaquindox in feed followed by hydrophilic interaction ultra-high-pressure liquid chromatographic analysis

A new method involving matrix solid-phase dispersion (MSPD) extraction and hydrophilic interaction ultra-high-pressure liquid chromatography (HILIC-UHPLC) with photodiode array detection was developed for the determination of carbadox and olaquindox in feed. Separation of carbadox and olaquindox was achieved within 1 min on the 1.7 microm Acquity UPLC BEH HILIC column by using isocratic elution with a mobile phase consisting of 10 mmol L(-1) ammonium acetate in acetonitrile-water (95:5, v/v) at a flow rate of 0.5 mL min(-1). Optimization of MSPD extraction parameters, such as type of solid sorbent and elution solvent were carried out. Optimal conditions selected for MSPD extraction were: 0.25 g of feed sample, 0.5 g of octadecylsilica as solid sorbent and 10 mL of acetonitrile-methanol (8:2, v/v) as eluting solvent. Both analytes provided average recoveries from spiked feed samples ranging from 89.1 to 98.4% with relative standard deviations less than 10%. Obtained performance characteristics are comparable to those achieved by liquid-liquid extraction-HPLC with the advantages of being simpler and significantly faster.     

Determination of beer aroma compounds using headspace solid-phase microcolumn extraction

A rapid sampling technique for the analysis of beer aroma compounds is described. The headspace (10 ml) is passed through the microcolumn filled with 5 mg of Tenax TA and thermally desorbed in a modified GC inlet (modification is described). Eight compounds (from acetaldehyde to 2-phenylethanol) in four beer samples were analyzed. The correlation coefficients (r²), repeatability (RSD) and limits of detection (LOD) were 0.9973-0.9994, 2.1-6.9% and 0.00002-0.13 mg/l, respectively. The methodology can be useful for routine beer sample analysis.     

Preparation and characteristics of high pH-resistant sol-gel alumina-based hybrid organic-inorganic coating for solid-phase microextraction of polar compounds

A novel alumina-based hybrid organic-inorganic sol-gel coating was first developed for solid-phase microextraction (SPME) from a highly reactive alkoxide precursor, aluminum sec-butoxide, and a sol-gel-active organic polymer hydroxyl-terminated polydimethylsiloxane (OH-TSO). The underlying mechanism was discussed and confirmed by IR spectra. The porous surface structure of the sol-gel coating was revealed by scanning electron microscopy. A detailed investigation was conducted to evaluate the remarked performance of the newly developed sol-gel alumina-OH-TSO hybrid materials. In stark contrast to the sol-gel silica-based coating, the alumina-based coating demonstrated excellent pH stability. In addition, good thermal resistance and coating preparation reproducibility are also its outstanding performance. As compared to silica-based hybrids material, the ligand exchange ability of alumina makes it structurally superior extraction sorbents for polar compounds, such as fatty acids, phenols, alcohols, aldehydes and amines. Practical applicability of the prepared alumina-OH-TSO fiber was demonstrated through the analysis of volatile alcohols and fatty acids in beer. The recoveries obtained ranged from 85.7 to 104% and the relative standard deviation values for all analytes were below 9%.     

Simultaneous determination of traces of pyrethroids, organochlorines and other main plant protection agents in agricultural soils by headspace solid-phase microextraction-gas chromatography

A solvent-free and simple method based on headspace solid-phase microextraction (HS-SPME) was developed in order to determine simultaneously 36 common pesticides and breakdown products (mostly pyrethroids and organochlorine compounds) in soil. The analysis was carried out by gas chromatography with micro-electron-capture detection (GC-microECD). As far as we know, this is the first study about the SPME of pyrethroid insecticides from soil. Factors such as extraction temperature, matrix modification by addition of water, salt addition (% NaCl) and fiber coating were considered in the optimization of the HS-SPME. To this end, a 3 x 2(3-1) fractional factorial design was performed. The results showed that temperature and fiber coating were the most significant variables affecting extraction efficiency. A suitable sensitivity for all investigated compounds was achieved at 100 degrees C by extracting soil samples wetted with 0.5 mL of ultrapure water (0% NaCl) employing a polyacrylate (PA) coating fiber. Using the recommended extraction conditions with GC-microECD, a linear calibration could be achieved over a range of two orders of magnitude for both groups of analytes. Limits of detection (LODS) at the sub-ng g(-1) level were attained and relative standard deviations (RSDs) were found to be lower than 14% for both groups of pesticides. Matrix effects were investigated by the analysis of different soil samples fortified with the target compounds. The method accuracy was assessed and good recovery values (>70%, in most cases) were obtained. The method was also validated with a certified reference material (RTC-CRM818-050), which was quantified using a standard addition protocol. Finally, the proposed HS-SPME-GC-microECD methodology was further applied to the screening of environmental soil samples for the presence of the target pesticides.     

Determination of sulphur compounds in beer using headspace solid-phase microextraction and gas chromatographic analysis with pulsed flame photometric detection

A simple and sensitive method for the analysis of volatile and semi-volatile sulphur compounds in beer at trace levels was developed using headspace solid-phase microextraction (SPME) and gas chromatography with pulsed flame photometric detection. Different SPME fibres were tested and a Carboxen-polydimethylsiloxane coated fibre was found to be the most appropriate. The adsorption and desorption conditions were optimised. The effect of ethanol concentration in the sample on the extraction of analytes was examined. A 60 m non-polar capillary column preceded by a 10 m length of a polar column was found to be capable of separating a wide range of C1-C6 sulphur compounds. The pulsed flame photometric detector enabled increased sensitivity to be obtained over previous methods, such as dynamic headspace followed by conventional flame photometric detection or sulphur chemiluminescent detection, with high sulphur selectivity. Two sulphur compounds, 2-methyl-1-butanethiol and 3-methylthiophene, were identified in beer for the first time.     

Development of a rapid method based on solid-phase extraction and liquid chromatography with ultraviolet absorbance detection for the determination of polyphenols in alcohol-free beers

An analytical method based on solid-phase extraction (SPE) and followed by liquid chromatographic separation and ultraviolet detection (HPLC-UV) is proposed for the determination of 10 phenolic compounds which participate on beer stability and sensory properties in alcohol-free beers. Acetonitrile was found to be the most appropriate solvent for the elution of polyphenolic compounds adsorbed on C18 cartridges. The performance of the method was assessed by the evaluation of parameters such as absolute recovery (generally higher than 60%), repeatability (lower than 10%), linearity (r2 higher than 0.993) and limits of quantitation (ranging from 1 to 37 microg/L); no matrix effects were observed. The polyphenol content of different Spanish alcohol-free beers is presented. Five phenolic compounds such as protocatechuic, p-coumaric, ferulic, caffeic acids, and (+)-catechin were identified at levels lower than 10 mg/L.     

Optimisation of a complete method for the analysis of volatiles involved in the flavour stability of beer by solid-phase microextraction in combination with gas chromatography and mass spectrometry

Headspace solid-phase microextraction combined with gas chromatography and mass spectrometry was used for the quantification of 32 volatiles which represent the typical chemical reactions that can occur during beer ageing. Detection was accomplished by employing on-fibre derivatisation using o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and normal HS-SPME extraction. The procedures were optimised for SPME fibre selection, PFBHA loading temperature and time, extraction temperature and time, and effect of salt addition. Interference of matrix effects was overcome by calibrating according to the standard addition method and by using internal standards. Afterwards, the method was validated successfully and was applied to study the flavour stability of different beer types.     

Determination of volatile compounds in grape distillates by solid-phase extraction and gas chromatography

Solid-phase extraction (SPE) procedure on octadecylsilica (C18) was developed for accumulation of volatile compounds from grape distillates. The procedure was optimised for final analysis by capillary gas chromatography. At mass concentrations in model solutions ranging from 0.1 to 50 mg/l solid-phase extraction recoveries of all analytes ranged from 69% for 2-phenylethanol to 102% for capric acid, with RSD values from 2 to 9%. SPE recoveries of internal standards to be added in the sample solution prior to extraction, higher alcohols 2-ethyl-1-hexanol and 1-undecanol, were 97 and 93%, respectively, with RSD values of 3%. Detection limits of analyzed compounds in model solutions ranged from 0.011 mg/l for isoamyl acetate to 0.037 mg/l for caproic acid. Method efficiency was tested in relation to acetic acid content, volume fraction of ethanol and possible matrix effects. A significant influence of matrix on SPE efficiency for geraniol, cis-2-hexen-1-ol and cis-3-hexen-1-ol was detected. For the same reason, 2-phenylethanol could not be determined by developed SPE method in samples of grape distillates. The developed solid-phase extraction method was successfully applied to determine the differences in volatile compound content in different grape distillates produced by the distillation of crushed, pressed and fermented grapes.     

Improved procedure for the the determination of rofecoxib in human plasma involving 96-well solid-phase extraction and fluorescence detection

An improved assay for the determination of rofecoxib in human plasma samples is described. The analyte and an internal standard were extracted from the plasma matrix using solid-phase extraction in the 96-well format with an Empore C8-SD extraction plate. The analytes are chromatographed on a Waters Symmetry C18 analytical column (3.5 microm, 50x4.6 mm) with a mobile phase consisting of acetonitrile-water (35:65, v/v). Analyte detection was via fluorescence following post-column photochemical derivatization. Eight point calibration curves over the concentration range of 0.5-80 ng/ml yielded a linear response when a 1/y weighted linear regression model was employed. Based on the replicate analyses (n=5) of spiked standards, the within-day assay precision was better than 8% RSD at all points on the calibration curve, within-day accuracy was within 6% of nominal at all standard concentrations. The between-run precision and accuracy of the assay, as calculated from the results of the analysis of quality control samples, was better than 7% RSD and within 5% of nominal. Assay throughput was improved by a factor of three as compared to previously described methods. The method was partially automated using a combination of a Packard Multi-Probe liquid handling system and a TomTec Quadra 96 workstation.     

超高效液相色谱-串联质谱法检测麦汁和啤酒中的麦香风味物质

应用超高效液相色谱-串联质谱(UPLC-MS/MS)技术定量检测了啤酒和麦汁中的2,5-二甲基-4-羟基-3(2H)-呋喃酮(DMHF)、2(或5)-乙基-5(或2)-甲基-4-羟基-3(2H)-呋喃酮(EMHF)和2-乙酰吡咯(2-AP)3种麦香风味物质。使用C₁₈固相萃取柱净化样品。采用ACQUITY UPLC HSS T3色谱柱(50 mm×2.1 mm, 1.8 μm)分离,以0.1%(v/v)甲酸水溶液和0.01%(v/v)甲酸乙腈溶液为流动相进行梯度洗脱。结合这3种化合物的保留时间,在正离子模式下,采用多反应监测(MRM)技术进行定量检测。当质量浓度低于1000 μ g/L时,校准曲线的线性良好(R²>0.999)。方法的加标回收率在74.3%~86.7%之间,相对标准偏差(RSD,n=6)在4.8%~7.3%之间。由于酵母发酵时会生成DMHF和EMHF,导致啤酒中这两种物质的含量明显高于麦汁。某些品类啤酒如印度淡色爱尔啤酒(IPA),通常含有较高的麦香风味物质。该法样品处理简单,选择性好,且灵敏、准确、重现性好,可用于啤酒生产的过程控制。     

固相萃取-高效液相色谱-质谱联用法同时测定食品中9种人工合成甜味剂

建立了固相萃取-高效液相色谱-串联质谱快速检测食品中安赛蜜、糖精钠、甜蜜素、三氯蔗糖、阿斯巴甜、阿力甜、纽甜、甘素及新橙皮甙二氢查尔酮等9种人工合成甜味剂的方法。样品中的甜味剂经三乙胺缓冲溶液（pH 4.5）提取，采用亲水亲脂平衡填料固相萃取柱净化，经Phenomenex Knietex^® F5色谱柱（100 mm×2.1 mm，2.6 μm）分离，以0.1%（v/v）甲酸-5 mmol/L甲酸铵溶液和甲醇为流动相，进行梯度洗脱，以电喷雾离子源正负离子切换多反应监测（MRM）模式进行质谱检测。采用内标法定量，进一步降低样品基质效应的影响。结果表明：本方法在去除样品基质干扰方面取得良好效果，9种甜味剂的检出限和定量限分别在2~30 μg/L和6~100 μg/L之间，在各自的线性范围内线性关系良好（相关系数r²>0.999）。9种甜味剂空白样品在3个水平下的加标回收率在86.3%~106.3%之间，相对标准偏差（RSD）在1.2%~5.9%之间。本方法快捷、高效、准确可靠，可用于复杂食品基质中9种人工合成甜味剂的快速检测。