顶空-气相色谱法测定天然胡萝卜素中的 溶剂残留量

目的建立顶空-气相色谱法测定天然胡萝卜素中的残留溶剂量。方法样品经N,N-二甲基乙酰胺溶解,经顶空进样,采用HP-INNOWAX毛细管柱分离,氢火焰离子化检测器检测,以外标法定量。结果在0~1000 mg/kg浓度范围内,正己烷、丙酮、甲醇、异丙醇和乙醇5种残留溶剂呈良好的线性关系,相关系数均大于0.995。各有机溶剂残留量的检出限为0.4~4.3 mg/kg;在15、20和40 mg/kg 3个水平的加标量时,加标回收率在85%~110%范围,相对标准偏差均小于3%(n=6),满足检测要求。结论该方法操作简便、定量准确,能满足天然胡萝卜素中残留溶剂量的检测需要。     

X-射线荧光光谱法快速测定谷物碾磨加工品中的重金属

目的 本研究利用X-射线荧光光谱法原理建立了一种谷物碾磨加工品中铅、总砷、镉、铬、总汞的快速检测方法。方法 选择谷物碾磨加工品中小麦粉典型基质,制备成含有一定量5种重金属标准样品,利用标准样品对检测时样品的粒径、装样质量、装样压力等检测条件进行优化,并对检测方法线性范围、定量限、精密度、重复性、稳定性等方法学进行考察。结果 检测方法中铅、总砷、镉定量限为0.1mg/kg,铬定量限为0.5mg/kg,总汞定量限为0.05mg/kg;线性范围铅、总砷、镉约为0.1mg/kg~2mg/kg,铬约为0.5mg/kg~9mg/kg,总汞约为0.05mg/kg~2mg/kg,线性相关系数(R2)均大于0.99;方法精密度、重复性、稳定性相对偏差均小于15%,对X-射线荧光光谱法与国检测结果进行比较,相对误差小于15%。结论 本研究建立的方法简便、快捷、准确性高,适宜对谷物碾磨加工品中5种重金属进行快速检测。     

UHPLC‐ESI‐MS/MS for the Quantification of Eight Major Gingerols and Shogaols in Ginger Products: Effects of Ionization Polarity and Mobile Phase Modifier on the Sensitivity

We developed and validated an improved ultra high performance liquid chromatography (UHPLC)‐electrospray ionization (ESI)‐tandem mass spectrometry (MS/MS) method for the fast separation and quantification of 8 major gingerols and shogaols (4‐, 6‐, 8‐, 10‐, and 12‐gingerols, and 6‐, 8‐, and 10‐shogaols) in gingerol products. The ionization polarity and mobile phase modifier greatly affected the mass ion profiles and sensitivity of the analytes. A mobile phase modifier of 0.05 mM ammonium formate dramatically decreased the sodium adduct ions and greatly increased the protonated ions of the gingerols and shogaols. Positive ion UHPLC‐MS/MS with the ammonium formate in mobile phase showed greatly higher (4.5‐ to 15.7‐fold) sensitivities than negative ion UHPLC. The positive ion UHPLC‐MS/MS method showed excellent linearities (r² > 0.999), low limits of detection (LOD = 2.5 to 8.2 pg), high accuracy and precision, and no considerable matrix effect. Baseline separation of the 8 target compounds was achieved in 1 min by the UHPLC with a short C18 core‐shell column. The method was successfully applied to analyze the compounds in fresh and dried powdered gingers, and dietary supplements. The total contents of the major compounds in the fresh gingers, dried powdered gingers, and dietary supplements were in the range of 1114 to 1478, 4380 to 11324, and 2915 to 29998 mg/kg, respectively. There was about 10‐fold variation of the content in the dietary supplements with the commercial brands. This represents the 1st report on the ionization polarity and mobile phase modifier on the sensitivity of gingerols and shogaols in LC‐mass spectrometry. Furthermore, the established method provided great improvement in chromatographic separation of the target gingerols.     

Simultaneous Determination of Dimethenamid,Saflufenacil and their Metabolites in Maize Using a Modified QuEChERS Method and Liquid Chromatography-Tandem Mass Spectrometry

Hydrophilic metabolites of pesticides in food and the environment are seldom analyzed due to the lack of suitable analytical methods. In the present study, a single-run analytical method was developed to determine dimethenamid, saflufenacil and their five metabolites in maize grain and plant. A good linearity was achieved for the matrix-matched calibration curves of the seven analytes with r²?≥?0.9991. The average recoveries of dimethenamid, saflufenacil and their metabolites in maize grain and plant were 70.1–113.8% with inter-day relative standard deviations ≤?21.5%. The limits of detection and quantification for the two herbicides and their metabolites were in the ranges of 0.008–1.4 μg/kg and 0.027–4.7 μg/kg, respectively, in two matrices. The limits of quantification for dimethenamid and saflufenacil in maize grain were below the maximum residue limits proposed by Codex (10 μg/kg). The results from field trials demonstrated the method effective and reliable for monitoring of the target residues in maize.     

Determination of flavour compounds in beer using stir‐bar sorptive extraction and solid‐phase microextraction

The analysis of volatile compounds in beer is important for quality control in the brewing industry. In this study, stir‐bar sorptive extraction (SBSE) and solid‐phase microextraction (SPME), two solvent‐less enrichment techniques, were applied in combination with gas chromatography flame ionization detection (GC/FID) for the determination of four flavour compounds (isoamyl acetate, ethyl hexanoate, benzaldehyde, myrcene) in beer. Limits of detection, linearity and repeatability of both methods were determined using standard ethanol solutions, while accuracy was determined by conducting recovery tests on commercial beer samples. Both methods were characterized by high linearity (r > 0.996) and repeatability (RSD = 1.76–10.66%). When both methods were compared, higher recoveries were obtained by SBSE, with limits of detection 1.8–2.8 times lower compared with SPME. In the analysis of commercial beer samples using both methods, SBSE analysis resulted in higher recoveries, therefore demonstrating promise for the analysis of beer volatiles. Copyright © 2015 The Institute of Brewing & Distilling     

The Occurrence of Beer Spoilage Lactic Acid Bacteria in Craft Beer Production

Beer is one of the world's most ancient and widely consumed fermented alcoholic beverages produced with water, malted cereal grains (generally barley and wheat), hops, and yeast. Beer is considered an unfavorable substrate of growth for many microorganisms, however, there are a limited number of bacteria and yeasts, which are capable of growth and may spoil beer especially if it is not pasteurized or sterile‐filtered as craft beer. The aim of this research study was to track beer spoilage lactic acid bacteria (LAB) inside a brewery and during the craft beer production process. To that end, indoor air and work surface samples, collected in the brewery under study, together with commercial active dry yeasts, exhausted yeasts, yeast pellet (obtained after mature beer centrifugation), and spoiled beers were analyzed through culture‐dependent methods and PCR‐DGGE in order to identify the contaminant LAB species and the source of contamination. Lactobacillus brevis was detected in a spoiled beer and in a commercial active dry yeast. Other LAB species and bacteria ascribed to Staphylococcus sp., Enterobaceriaceae, and Acetobacter sp. were found in the brewery. In conclusion, the PCR‐DGGE technique coupled with the culture‐dependent method was found to be a useful tool for identifying the beer spoilage bacteria and the source of contamination. The analyses carried out on raw materials, by‐products, final products, and the brewery were useful for implementing a sanitization plan to be adopted in the production plant.     

Mycotoxins produced by Fusarium genus in maize: determination by screening and confirmatory methods based on liquid chromatography tandem mass spectrometry

A confirmatory method for fusariotoxin analysis in maize meal, based on liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), was developed, and compared with a previously published screening method, based on the same technique. By eluting selectively from a Carbograph-4 clean-up cartridge trichothecenes, fumonisins and macrocyclic lactones, and optimizing LC–MS/MS conditions for every chemical class, a sensitive and reliable determination was performed. Method quantification limits for confirmatory and screening methods were in the range 0.001–0.019 mg/kg and 0.003–0.125 mg/kg, respectively.     

Determination of 5-methoxypsoralen in suntan cosmetics

A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5-alpha-cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type. By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.     

Quantitative Analysis of 10 Mycotoxins in Wheat Flour by Ultrahigh Performance Liquid Chromatography‐Tandem Mass Spectrometry with a Modified QuEChERS Strategy

A simple and sensitive analytical method for quantitative analysis of 10 mycotoxins was developed and validated by a combination of modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure with ultrahigh performance liquid chromatography‐tandem mass spectrometry (UHPLC‐MS/MS). Sample preparation involved QuEChERS with dispersive solid phase extraction for clean‐up, and analysis was performed by reversed‐phase UHPLC‐MS/MS using electrospray negative ionization and multiple reaction monitoring. Under optimized conditions, the calibration curves displayed good linear relationships with all coefficients of determinations (r²) higher than 0.998. The limits of quantification for all target mycotoxins were lower than 7 μg/kg. Trueness and precision for the analytes were 70% to 116% average recoveries and 2% to 13% relative standard deviations (RSDs). The validated method was used to analyze 46 wheat flour samples for the targeted mycotoxins. The method can be used as a rapid and robust tool for screening mycotoxin in cereal products.     

Validation of a HS-SPME-GC Method for Determining Higher Fatty Esters and Oak Lactones in White Rums

Higher fatty esters and oak lactones are the main components of white rum aroma and furthermore, they have an important sensorial impact in these distilled alcoholic beverages. A method for analyzing these volatile compounds was validated. It involves a separation and concentration step using headspace solid-phase microextraction (HS-SPME) and determination by capillary gas chromatography using flame ionization detection. The method showed a good within-day (RSD?<?3 %) and between-day precision (RSD?<?5 %). The calibration curves were linear at the tested ranges (R?>?0.99) and the limits of detection and quantification were 0.001–0.018 and 0.003–0.054 mg L^?1 (12 %?v/v alcohol), respectively. Good recoveries were obtained (98.6–100.3 %). The method is suitable for the quality control of higher fatty esters and oak lactones in white rums.     

Simultaneous Determination of Fluoxastrobin and Tebuconazole in Cucumber and Soil Based on Solid-Phase Extraction and LC-MS/MS Method

Based on aqueous acetonitrile extraction (AAE) and solid-phase extraction (SPE) pretreatments, an analytical method was first introduced for the simultaneous determination of E/Z-fluoxastrobins and tebuconazole in cucumber and soil. The method validation obtained satisfactory results in terms of linearity, matrix effect (? 17.7–2.9%), fortified recovery (78.4–108.0%), precision (1.1–11.9%), and sensitivity (the limits of quantification were 5 μg/kg). During application of the method, the recommended method was used to estimate the dissipation and residues of fluoxastrobin and tebuconazole in cucumber and soil in field tests. The results showed that the half-lives of fluoxastrobin and tebuconazole were 6.5–8.3 days in cucumber and 11.6–12.2 days in soil. In the terminal residue experiment, the residues of fluoxastrobin and tebuconazole were 33–389 and 35–522 μg/kg in cucumber, respectively. Referencing the maximum residue limits (MRLs) of fluoxastrobin (0.5 mg/kg, US Environmental Protection Agency) and tebuconazole (1.0 mg/kg, China), 1 day is recommended as the preharvest interval for the application of fluoxastrobin and tebuconazole in cucumber.     

固相萃取-高效液相色谱法测定猪肉与鸡肉中替米考星、泰乐菌素残留量

建立了高效液相色谱法(HPLC)测定猪肉与鸡肉中替米考星、泰乐菌素残留量的检测方法.样品用乙腈提取,C18固相萃取小柱净化,采用高效液相色谱分离,二极管阵列检测器(PDA)检测,外标法定量.结果表明:标准校准曲线在30～1000μg/L的范围内呈良好线性关系,相关系数r＞0.999.样品中替米考星、泰乐菌素的添加水平分别为0.05、0.10、0.15mg/kg时,样品加标回收率为72.7％～90.8％,变异系数在2.6％～8.3％之间,替米考星和泰乐菌素方法检出限30μg/kg,定量限为50μg/kg.本法简便、快速、定量准确、精密度高,适用于猪肉和鸡肉中替米考星与泰乐菌素残留量的检测.     

固相萃取柱净化-气相色谱法定量测定食用植物油中饱和烃类矿物油

目的以自制硫酸硅胶和10%硝酸银硅胶填料分层装填的复合固相萃取柱为净化手段,建立一种测定食用植物油中饱和烃类矿物油的分析方法。方法样品经正己烷提取,固相萃取柱净化,氮吹浓缩,然后经DB-1石英毛细管色谱柱分离,采用气相色谱-火焰离子化检测器检测,外标法定量。结果考察了填料类型、填料用量、洗脱体积等因素对提取效率的影响。在优化的条件下,饱和烃类矿物油检测的线性范围为5.0~500.0mg/L,相关系数r~2=0.9991,方法检出限为3.0 mg/kg,定量限为10.0 mg/kg。样品在10.0、20.0、50.0 mg/kg 3个水平下的加标回收率为93.2%~103.7%,相对标准偏差为3.97%~5.33%(n=6)。结论该法操作简单、快速、准确度高,检出限能满足对食用植物油中饱和烃类矿物油残留的检测要求,且使用常规分析仪器、分析成本低,值得推广应用。     

超高效液相色谱-串联质谱法检测婴儿米粉中11种有机磷阻燃剂

采用超高效液相色谱-串联质谱技术,建立婴儿米粉中11种有机磷阻燃剂的检测方法。样品用0.5%甲酸乙腈溶液超声提取,提取液经分散固相萃取吸附剂净化,聚四氟乙烯滤膜过滤后上机检测,5 mmol/L甲酸铵的水溶液和乙腈为流动相梯度洗脱,目标化合物在ACQUITY UPLC? BEH C₁₈ 色谱柱（100 mm×2.1 mm,1.7 μm）上实现分离,在电喷雾正离子扫描模式下进行多反应监测（MRM）,外标法定量。通过优化色谱条件,11种有机磷阻燃剂均达到了基线分离。11种有机磷阻燃剂在0.5~100 μg/L（磷酸三辛酯0.05~10 μg/L）范围内线性关系良好,相关系数r均大于0.994。检出限（3S/N）为0.003~0.926 μg/kg,定量限（10S/N）为0.01~2.78 μg/kg。婴儿米粉中低、中、高3个添加浓度水平的加标回收率为63.2%~113.4%,相对标准偏差（n=6）均小于10%。运用建立的方法分析了4种婴儿米粉,磷酸三苯酯的检出率高达100%,其中一份米粉检出了磷酸三正丁酯和磷酸三（2-氯丙基）酯。该方法简单可靠、灵敏度高、重现性好,覆盖的有机磷阻燃剂种类多,适用于婴儿米粉中痕量有机磷阻燃剂的检测。     

Bestimmung von 5-Methoxypsoralen in Sonnenschutzmitteln

Zusammenfassung Es wird eine Methode zur Bestimmung von 5-Methoxypsoralen in Sonnenschutzmitteln beschrieben. Nach säulenchromatographischer Reinigung wird der Extrakt mittels zweidimensionaler Dünnschichtchromatographie untersucht. Bei positiven Befunden wird das 5-Methoxypsoralen capillar-gaschromatographisch unter Verwendung von 5--Cholestan als innerem Standard quantitativ bestimmt. Die Ergebnisse werden durch Gaschromatographie-Massenspektrometrie (GC-MS) abgesichert. Die Wiederfindungsrate beträgt bei Kosmetika vom Emulsionstyp 70% und bei Sonnenölpräparaten 90%. Die Nachweisgrenze liegt je nach Probenart, zwischen 0,1 und 0,5 mg/kg.Mit dieser Methode wurden in 6 von 21 untersuchten Sonnenschutzmitteln bis zu 28 mg 5-Methoxypsoralen/kg nachgewiesen.

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Determination of 5-methoxypsoralene in suntan-cosmetics

Summary A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5--cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type.By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.

     

多壁碳纳米管QuEChERS-气相色谱法测定茶叶中23 种有机磷农药残留量

建立测定茶叶中23 种有机磷农药残留量的气相色谱检测方法。茶叶样品经丙酮提取后,采用QuEChERS方法前处理,以N-丙基乙二胺（N-propyl ethylenediamine,PSA）、多壁碳纳米管（multi walled carbon nanotubes,MWCNTs）吸附提取液中的干扰组分,净化液经气相色谱测定,基质外标法定量。采用本实验建立的方法,在0.02～1.00?μg/mL范围内,23?种有机磷的线性关系良好,相关系数r大于0.986?5,方法检出限为0.01～0.02?mg/kg,定量限为0.03～0.06?mg/kg。在0.05、0.50、1.00?mg/kg三个添加量的平均加标回收率为81.8%～107.2%,相对标准偏差为1.2%～7.2%。与传统的QuEChERS相比,该方法具有操作简单、快速、试剂用量少、回收率高、准确性强等特点,适合于茶叶中23?种有机磷农药残留量的测定。     

基于液相色谱-气相色谱联用测定巧克力中的饱和烃与芳香烃矿物油

建立基于液相色谱-气相色谱（on-line liquid chromatography-gas chromatography,LC-GC）联用测定巧克力中饱和烃（mineral oil saturated hydrocarbons,MOSH）和芳香烃矿物油（mineral oil aromatic hydrocarbons,MOAH）的方法。该方法以正己烷于60 ℃超声提取20 min,取上清液以硅胶除去脂肪,以间氯过氧苯甲酸与烯烃进行环氧化反应,最后以LC-GC联用技术分离测定,其中LC用于保留油脂和烯烃环氧化物,同时分离得到MOSH和MOAH,通过由阀切换、保留间隙与溶剂排空阀组成的LC-GC接口分别将MOSH和MOAH导入2 个平行的GC通道并以氢火焰离子化检测器测定。该方法的定量限为0.5 mg/kg,矿物油在0.5～85.5 mg/L内线性关系良好（R2=0.998）,加标回收率为80.3%～93.8%,相对标准偏差为1.58%～8.22%。测定了28 个巧克力产品中的矿物油含量,其中有20 个产品检出MOSH,含量为1.83～22.23 mg/kg,1 个检出1.57 mg/kg MOAH。谱图分析表明,一些产品中含有塑料迁移出的聚烯烃低聚饱和烃（polyolefin oligomeric saturated hydrocarbons,POSH）,LC-GC无法分离POSH与MOSH,因此测得结果实际上是MOSH和POSH的总量。     

Nitrate and nitrite quantification from cured meat and vegetables and their estimated dietary intake in Australians

High dietary nitrate and nitrite intake may increase the risk of gastro-intestinal cancers due to the in vivo formation of carcinogenic chemicals known as N-nitroso compounds. Water and leafy vegetables are natural sources of dietary nitrate, whereas cured meats are the major sources of dietary nitrite. This paper describes a simple and fast analytical method for determining nitrate and nitrite contents in vegetables and meat, using reversed-phase HPLC-UV. The linearity R² value was >0.998 for the anions. The limits of quantification for nitrite and nitrate were 5.0 and 2.5 mg/kg, respectively. This method is applicable for both leafy vegetable and meat samples. A range of vegetables was tested, which contained <23 mg/kg nitrite, but as much as 5000 mg/kg of nitrate. In cured and fresh meat samples, nitrate content ranged from 3.7 to 139.5 mg/kg, and nitrite content ranged from 3.7 to 86.7 mg/kg. These were below the regulatory limits set by food standards Australia and New Zealand (FSANZ). Based on the average consumption of these vegetables and cured meat in Australia, the estimated dietary intake for nitrate and nitrite for Australians were 267 and 5.3 mg/adult/day, respectively.     

QuEChERS-UPLC-MS/MS测定大米中氯虫苯甲酰胺和五氟磺草胺的残留

目的：建立一种新的QuEChERS-超高效液相色谱—串联质谱（UPLC-MS/MS）检测大米中氯虫苯甲酰胺和五氟磺草胺的残留方法。方法：样品经0.2%甲酸—乙腈提取后，N-丙基乙二胺（PSA）和石墨化碳黑（GCB）填料净化，以0.2%甲酸水—乙腈为流动相梯度洗脱，经C₁₈色谱柱分离，采用UPLC-MS/MS测定。结果：氯虫苯甲酰胺和五氟磺草胺的定量限（LOQ）均为0.004 mg/kg，方法检出限（LOD）均为0.001 mg/kg。两种待测农药在0.002~0.5 mg/L质量浓度范围内呈良好的线性关系，其相关系数均在0.993以上。在0.05，0.1，0.5 mg/kg添加水平下，两种待测农药的平均回收率为86%~110%；相对标准偏差（RSD）为1.5%~6.1%。结论：该方法高效简便、稳定性好、灵敏度高，适用于大米中氯虫苯甲酰胺和五氟磺草胺的检测。     

Characterization and determination of brewer's solid wastes composition

Agro‐industrial wastes are produced in large quantities around the world from the processing and manufacturing of food and beverages. The disposal of these wastes into the environment leads to damage to ecosystems owing to their composition rich in organic matter. In this context it may be noted that the brewing industry, whose production process includes processing steps and fermentation of vegetable raw materials such as barley and/or other grains used as adjuncts and hops, generates various byproducts. The worldwide consumption of these beverages and the current model of breweries, which includes production on a large scale, lead to the generation of large amounts of brewery waste, namely spent grain, hot trub and residual yeast. Owing to its composition, these residues exhibit significant potential for application in bioprocess technologies. In this study the three residues mentioned had their composition determined as a function of moisture, ash, total organic carbon (TOC), total and soluble nitrogen, reducing sugar and soluble free amino nitrogen. Moreover, the residues were characterized for total acidity, pH and chemical oxygen demand (COD) of total and soluble fractions. The three residues evaluated had high moisture content (>80%) and high organic matter content (TOC and COD, ~50% and >1000 mg/g, respectively), which can highlights the significant protein fraction (almost 50% for hot trub and residual yeast), suggesting the possibility of using these wastes for recovery. Copyright © 2015 The Institute of Brewing & Distilling