Easy and rapid method for the quantitative determination of pyrrolizidine alkaloids in honey by ultra performance liquid chromatography-mass spectrometry: An evaluation in commercial honey

Pyrrolizidine alkaloids (PAs) are toxins biosynthesised by plants and they are known to be present in approximately 6000 plant species, about 3% of all flowering plants. PAs are probably the most widely distributed natural toxins and represent a potential risk to human health, since poisoning caused by these toxins is associated with acute and chronic liver damage and may lead to death. One of the most common sources of PAs exposure in humans is honey consumption. We have developed a quick and easy method to quantify nine different PAs (echimidine, heliotrine, intermedine, lycopsamine, lasiocarpine, retrorsine, seneciphylline, senecionine, senkirkine) in honey based on QuEChERS sample extraction and ultra fast liquid chromatography coupled with mass spectrometry detection. We performed a validation study of the method and it resulted in good precision and accuracy, high recoveries, and good linear calibrations. The limit of detection ranged from 0.021 to 1.39 μg Kg⁻¹ and the limit of quantification from 0.081 to 4.35 μg Kg⁻¹. This new approach was applied to the quantification of PAs in retail honeys purchased in local supermarkets, classified by their country of origin: Italian honeys, blends of honey of European countries and blends of honey of European and non-European countries. The concentrations detected ranged from 1 to 169 μg PAs/kg⁻¹ with higher concentrations in blends of European and non-European honeys. This study reveals that many samples tested would exceed the tolerable daily intake suggested for these substances and they could be a hazard to human health.     

Validation of a method of high performance liquid chromatography with fluorescence detection for melamine determination in UHT whole bovine milk

A method of high performance liquid chromatography with fluorescence detection (HPLC-Fluo), based on previous studies of the natural fluorescence emission of melamine (250/365 nm), was developed and validated for melamine determination as an adulterant of bovine UHT whole milk. The clean up treatment of milk samples by deproteinization was thoroughly optimized. No matrix effect was observed and a linear range from 0.05 to 10.0 μg mL⁻¹ was obtained, with a value of R² equal to 0.9998. The limits of detection and quantification of melamine were 0.0081 and 0.027 μg mL⁻¹ respectively, or 0.023 and 0.076 μg g⁻¹ of milk, respectively, considering the sample dilution during extraction. Extracts of milk samples fortified with melamine at three concentration levels, two of which corresponded to the levels established by WHO for melamine in foods, led to an overall mean recovery of 95.4 ± 1.2% (n = 9). This recovery value satisfies the performance criteria established by the Codex Alimentarius for analytical methods suitable for determination of food residues, demonstrating the usefulness and effectiveness of the proposed method.     

Comparison between Karl Fischer and refractometric method for determination of water content in honey

The aim of this work was to compare refractometric index (RI) and Karl Fischer (KF) titration methods for water content measurement in honeys. In addition, the effectiveness of two different solvents (methanol (M) and methanol:formamide in the ratio 1:1 (M + F)) was evaluated.Results indicated that RI and KF methods yielded similar results for water content determination in honeys; mainly, when the solvent M + F was used. This solvent mixture (M + F) also allowed a reduction in titration time which may be a potential advantage for measuring water content in honey.     

三维定量荧光录井解释评价方法研究

二维定量荧光录井检测精度相对较低,荧光谱图所反映的信息量欠丰富,虽然在一定程度上可以满足录井解释评价的要求,但解释评价符合率低;三维定量荧光录井虽然检测精度高、谱图信息丰富,但目前国内各油田尚无定型的解释评价标准和方法。针对这一现状,以吉林探区为例,在深入分析荧光谱图中反映最大荧光强度特征峰位最佳激发波长和发射波长的基础上,得出了利用特征峰位识别含油样品原油性质的标准;在详细分析如何确定二维、三维油性指数的条件下,建立了运用二维、三维油性指数判断油质的标准;通过对10口井54层岩屑样品的二维、三维定量荧光油性指数的统计分析,结合试油结果,分别建立了二维油性指数与单点标定相当油含量油水层解释评价图板和三维油性指数与体积标定相当油含量油水层解释评价图板。实际应用和统计分析表明,含油样品原油性质的识别标准行之有效,储集层解释评价方法具有一定的可行性。     

HPLC荧光法测定文拉法辛血浆药物浓度

建立一种反相高效液相色谱法测定血浆中文拉法辛浓度。血样经液-液萃取,以乙腈-0.05 moL·L~(-1)磷酸二氢钠溶液为流动相洗脱,流速1.0 mL/min,柱温为40℃;激发波长为276 nm,发射波长为598 nm。文拉法辛的线性范围为5～1000 ng/mL,最低血药检测浓度为1 ng/mL(S/N>3);文拉法辛在浓度10,40,1000 ng/mL的萃取回收率和方法回收率分别在78.9%～84.2%和93.2%～108.5%以内;日内与日间的RSD分别小于7%和14%(n=5);本法灵敏,简单,准确,经济,重现性好,可满足药动学研究与治疗药物监测的要求。     

Methods for the determination of HMF in honey: a comparison

HMF (5-hydroxymethylfurfuraldehyde) is essential to evaluate the conformity of honey to the current legislation. Elevated concentrations of HMF in honey provide an indication of overheating, storage in poor conditions or age of the honey. Both the Codex Alimentarius Commission (Alinorm 01/25, 2000) and the European Union (Directive 110/2001) established that its concentration in honey usually should not exceed 80 or 40 mg/kg, respectively. The International Honey Commission recommends three methods for the determination of HMF: two spectrophotometric methods, determination after White and after Winkler and a HPLC method. These methods were recently tested by the International Honey Commission (1999). Aim of this research was to compare HMF values in unifloral honeys measured by the three methods. From our data, HPLC and White methods usually give similar values, except for eucalyptus honey; Winkler method gave for all honeys higher values than other two methods.     

Chiral volatile compounds for the determination of orange honey authenticity

Assessment of the botanical origin of the unifloral honeys is of great concern in the context of consumer protection and quality control. Nevertheless, the methods that are currently available are not satisfactory. In order to find alternatives to the time consuming and uncertain methods, a new analytical approach is proposed; it is based on the enantiomeric ratio investigation of chiral volatile constituents which are derived from the plants being visited by the bees. The method was applied to orange honeys; firstly, the volatile fraction of orange honey and flowers were studied by SPME-GC-MS; a large number of components were identified in orange honeys while linalool prevailed among orange flower volatiles. The enantiomeric ratios of linalool and its oxides were determined and analogous values between honey and flowers resulted. Even if a wide variability in the amount of typical volatile constituents of orange honeys emerged, the enantiomeric ratios of linalool and its oxides remained stable and thus less influenced by production period, conditioning, packaging, storage, etc. As a result the enantiomeric distribution of the honey volatile constituents that directly come from flowers could represent a rapid and easy method for floral origin authenticity.     

紫外荧光法和氧化微库仑法测定天然气中总硫含量的比对研究

目前国内检测天然气中总硫含量应用比较多的方法是氧化微库仑法和紫外荧光法,在实际应用中,紫外荧光法具有比氧化微库仑法更加稳定抗干扰的优点。同时,越来越多的紫外荧光仪使用反馈都优于氧化微库仑仪。为了对两种方法进行充分研究,在8家实验室用不同的紫外荧光仪以及在4家实验室用不同的氧化微库仑仪对同一批次21个样品进行了重复测试,分别从精密度、稳定性、仪器效率、操作、普及情况5个方面进行比较。研究结果表明,两种方法的精密度数据相差不大,紫外荧光法相比氧化微库仑法具有仪器分析效率更高、调试过程更快速简捷,稳定性更优越并在国内的使用越来越普及等优势。该研究成果为两种方法测定天然气总硫含量测试的结果判定提供了参考,为GB 17820-2018《天然气》中将总硫检测的仲裁方法修改为紫外荧光法提供了有力的技术支撑,也为制定ISO 20729:2017《天然气硫化合物测定用紫外荧光法测定总硫含量》和修订GB/T 11060.8-2012《天然气含硫化合物的测定第8部分:用紫外荧光光度法测定总硫含量》提供了基础数据;与现行的GB/T 11060.4-2017《天然气含硫化合物的测定第4部分:用氧化微库仑法测定总硫含量》精密度要求相比,该研究成果更契合日常实验检测水平,建议开展该项国家标准的修订工作。     

空气雾化钻井井壁稳定性模拟实验装置及评价方法

介绍了一种空气雾化钻井井壁稳定性模拟实验装置,该装置雾化效果好,雾化液量、风速、温度可调节,可很好地模拟液滴与岩心的相互作用和高速气流对井壁的剪切作用。提出两种评价井壁稳定性的方法:井壁针入度法和井径法。针入度和井径均可用针入度仪测定。针入度法能敏感地反映岩心与雾化空气之间因物理化学作用所引起的岩心强度的变化;井径法能反映岩心遇雾时吸水膨胀和风速对井壁剪切冲蚀作用的综合结果。这两种评价方法重现性好,规律性强。     

Rapid method based on immunoassay for determination of paraquat residues in wheat,barley and potato

The detection of bipyridine herbicides residues in food samples is hampered due to their particular physico-chemical features, which requires the application of specific extraction and analytical procedures, which disqualifies them from being incorporated into the multi-residue methods (MRMs). There is a need for alternative robust and efficient analytical screening methods, and in this respect, we present here a fast and reliable immunochemical analytical procedure for the detection of paraquat (PQ) residues in food samples, particularly potato, barley and wheat. The procedure involves the extraction with 1 N HCl:MeOH at 80 °C, followed by centrifugation and filtration, and the extracts can be directly measured by a microplate-based ELISA without any other sample treatment or clean-up, except from buffering the solution and adjusting the pH. Selective polyclonal antibodies, were raised against N-(4-carboxypent-1-yl)-N′-methyl bipyridilium acid (hapten PQ1), and used to establish a high sensitive immunochemical analytical assay, able to measure simultaneously many samples. Under these conditions the accuracy is very good, with almost quantitative recoveries. The non-specific interferences caused by the matrix are negligible for the case of potato and wheat, while for barley it is necessary to further dilute the extract or using a negative certified extract to build the standard calibration curve. The method of extraction consisted in acidic extraction and after a dilution is able to be measured. The analysis method results simply, achieving good detectabilities. The limits of detection (LODs) achieved were between 0.037 ± 0.01 μg kg⁻¹ in wheat, 0.71 ± 0.3 μg kg⁻¹ in barley and 0.56 ± 0.10 μg kg⁻¹ in potatoes, values that are far below the Maximum Residue Level (20 μg kg⁻¹) established by the EU policies for paraquat residues in these foodstuff products. The results demonstrate the high potential of these methods as screening tools for food safety and inspection controls.     

Rapid method for the determination of organic acids in wine by capillary electrophoresis with indirect UV detection

A capillary electrophoresis method for organic acids in wine was developed and validated. The optimal electrolyte consisted of 10 mmol/L 3,5-dinitrobenzoic acid (DNB) at pH 3.6 containing 0.2 mmol/L cetyltrimethylammonium bromide as flow reverser. DNB was chosen because it has an effective mobility similar to the organic acids under investigation, good buffering capacity at pH 3.6, and good chromophoric characteristics for indirect UV-absorbance detection at 254 nm. Sample preparation involved dilution and filtration. The method showed good performance characteristics: Linearity at 6 to 285 mg/L (r > 0.99); detection and quantification limits of 0.64 to 1.55 and 2.12 to 5.15 mg/L, respectively; separation time of less than 5.5 min. Coefficients of variation for ten injections were less than 5% and recoveries varied from 95% to 102%. Application to 23 samples of Brazilian wine confirmed good repeatability and demonstrated wide variation in the organic acid concentrations.     

Monitoring the presence of residues of tetracyclines in baby food samples by HPLC-MS/MS

Tetracyclin is a group of antimicrobial permitted in animal food production, but their concentrations in food of animal origin should not exceed 100 μg kg⁻¹ (in meat and milk). Although the detection of these substances above these limits involves fines and jail for the producer, residues of tetracyclines are still being detected in food a potential risk to consumer health, especially babies.In the past, baby foods were carefully prepared at homes. However, modern lifestyles have led to the commercialization of ready-made baby food. Generally, these products are made with vegetable and meat from different animals, such as pork, chicken or beef. The presence of tetracyclines in meat at concentrations above 100 μg kg⁻¹ is forbidden in Europe by the Regulation 37/2010. Consequently this concentration is also applicable to the portion of meat present in baby food. Even if the presence of tetracyclines is controlled regularly in meat, they should also be monitored in baby food as babies are vulnerable to such as drugs.A rapid analytical method based on high-performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS) for quantification of four tetracyclines (tetracycline, chlortetracycline, doxycycline and oxytetracycline) in baby food is presented. The tetracyclines are extracted with EDTA-McIlvaine buffer, acidified at pH 4.0, followed by liquid–liquid extraction with ethyl acetate. The final extract is analysed within 19 min on a Sunfire HPLC column from Waters. Validation was performed according to the Commission Decision 2002/657/EC. The mean accuracy was 103 μg kg⁻¹, and the mean precision, was less than 23% for all the tetracyclines. The method was tested on 31 prepared baby food samples containing vegetable and beef. The presence of oxytetracycline was detected in one of the samples at a concentration of 5 μg kg⁻¹.     

Alternatives to official analytical methods used for the water determination in honey

A modified Karl Fischer (KF) titration method (measurements at 50°C instead of room temperature) for the precise determination of the water content in honey has been developed together with the adjustment of a drying method using an infrared (IR) technique. The results obtained by this IR method applying a temperature between 98–100°C were found to be very similar to those obtained by the KF technique. In the second part of the study, the water concentration was determined in 39 authentic honey samples from various geographical and botanical origins using four different techniques: KF titration, refractive index measurements, official oven-drying method and a special oven method. Significant differences could be observed (maximum differences were in the range 0.9–5.1% absolute). The results obtained by KF titration were found to have the lowest standard deviations. With the exception of a few honey varieties, this method led to the highest values.     

Validation of the procedure for the determination of aflatoxin B1 in animal liver using immunoaffinity columns and liquid chromatography with postcolumn derivatisation and fluorescence detection

The validation of the procedure for the determination of aflatoxin B₁ in animal liver (pig, chicken, turkey, beef, calf) was performed. The limit of detection (LOD) and limit of quantification (LOQ) were 2 ng/kg and 7.8 ng/kg, respectively. The repeatability of measurements, represented by the standard deviation (RSD_r) was 7.5%, 7.1%, and 4.8% at the contamination levels of 0.025 μg/kg, 0.050 μg/kg, and 0.075 μg/kg, respectively. The relative standard deviation for the within-laboratory reproducibility (RSD_R) was 18% at the level of 0.025 μg/kg and 22% at the levels of 0.050 μg/kg and 0.075 μg/kg. The measurement uncertainties at the same contamination levels were ±0.007 μg/kg, ±0.016 μg/kg, and ±0.023 μg/kg, respectively. The mean recovery was 72.8%, the decision limit (CCα) 0.063 μg/kg and the detection capability (CCβ) 0.080 μg/kg. The results indicate that the procedure is suitable for the determination of aflatoxin B₁ in animal liver and can be implemented for the routine analysis.     

同步荧光光谱多点函数拟合确定原油样品浓度技术

目前油田使用的定量荧光录井中存在二维发射光谱单一峰值浓度的定量测量范围小、多次稀释增大了人为误差和浪费的问题.利用同步扫描荧光光谱技术,在10^-4g/L至10g/L浓度范围内获取胜利油田原油样品在不同浓度下波长差为40nm的正己烷萃取液的同步光谱,发现不同的浓度下同步光谱不仅表现为峰高变化,峰位也有显著变化.选取了最具代表性的7个峰值,将光谱数据在非线性范围内进行多峰值的最小二乘法浓度响应函数拟合,多点同时定量,所得误差小于5%,重复率和准确率较高.图1表2参9     

Assessment of a handheld fluorescence imaging device as an aid for detection of food residues on processing surfaces

Contamination of food with pathogenic bacteria can lead to foodborne illnesses. Food processing surfaces can serve as a medium for cross-contamination if sanitization procedures are inadequate. Ensuring that food processing surfaces are correctly cleaned and sanitized is important in the food industry to reduce risks of foodborne illnesses and their related costs. A handheld fluorescence imaging device was assessed for detection of three types of food residues that have been associated with foodborne illness outbreaks, i.e. spinach leaf, milk, and bovine red meat, on two commonly used processing surfaces, i.e. high-density polyethylene and food grade stainless steel. Fluorescence excitation at 405 nm was supplied by 4 × 10 W light emitting diodes. Interchangeable optical filters were selected to optimise the contrast between the food residues and processing surfaces, using hyperspectral fluorescence imaging. The fluorescence imaging plus image analysis differentiated food residues from the processing surfaces more clearly than visual inspection in ambient lighting. This optical sensing device can be used to detect food fouling on food processing surfaces over relatively large areas, and has potential for use in the food industry as an aid for detection of specific food residues.     

利用气测录井简易参数法判别油、气、水层

气测录井现场解释评价常用且比较成熟的经验统计法有烃组分三角形图解法、皮克斯勒解释图板法、烃类比值法（3H法）等,由于不同井场的地下地质和地面环境因素不尽相同、钻井工程参数的差异和解释方法的局限性,各种方法的解释符合率均有一定程度的差异。从提高解释符合率以及简便、快速发现并判别油、气层的角度出发,分析了应用气测录井全烃、异常倍数和重烃相对含量判别储集层油气水状况的理论依据,给出了利用该3项参数的判别标准,结合实例分析了不同条件下的判别原则,同时指出了该方法的局限性。通过103个油、气、水层的判别实例归纳分析,表明这种方法简便、可行,符合率相对较高,具有一定的推广应用价值。