固相萃取-高效液相色谱法同时测定噻菌灵和多菌灵在浓缩菠萝汁中的残留量

建立了一种可同时测定浓缩菠萝汁中噻菌灵和多菌灵残留量的反相高效液相色谱分析法。浓缩菠萝汁样品与水按一定比例稀释后,经过调节溶液的pH值、离心、过滤,用混合相固相萃取小柱(Mixed-mode SPE)进行提取、净化,并用配有二极管阵列检测器(DAD)的液相色谱仪检测,外标法定量。使用噻菌灵和多菌灵对照品进行添加回收率测定,结果显示,本方法对噻菌灵的检出限为0.020 mg/kg,回收率为75.7%~93.3%;对多菌灵的检出限为0.020 mg/kg,回收率为80.8%~99.2%;测定的相对标准偏差均不大于5.7%。本方法简单、快速、准确,能满足常规噻菌灵和多菌灵残留量检测的需要。     

A new method research for determination of natural pigment crocin yellow in foods by solid-phase extraction ultrahigh pressure liquid chromatography

Crocin yellow was determined in soft drinks, sausages and sauces by ultra performance liquid chromatography coupled with ultraviolet detector and analyzed within 5 min using a short analytical column ACQUITY UPLC HSS T3 2.1 x 100 mm 1.8 μm) with gradient elution. An innovative pretreatment method based on homemade macroporous resin solid-phase extraction (SPE) column was established. The SPE column packed with macroporous resins could simplify the sample preparation of multi-matrices and be reused by regeneration steps. The recoveries of crocin yellow added to soft drinks, sausages and sauces at three levels ranged from 81.3% to 106.2%, and relative standard deviations (RSDs) were within 8.8%. The limits of quantitation of soft drinks, sausages and sauces were 0.5 mg/kg, 5 mg/kg and 5 mg/kg, respectively.     

Determination of the total carbon in soft drinks by tungsten coil electrothermal vaporization inductively coupled plasma spectrometry

A method is developed for the direct determination of carbon in soft drinks by electrothermal vaporization inductively coupled plasma atomic emission spectrometry. A tungsten coil is used as the electrothermal vaporizer, and is extracted from a commercially produced 150 W, 15 V microscope bulb. The standard additions method is employed to correct any matrix effects from the samples. Carbon emission is monitored at 193.091 nm. Carbon content determined for the samples was in the range of 13 to 60 g in one 8 fl oz serving, and these values agreed with the label values in the range 93 to 137% (except for one sample, Orange Fanta, which provided a 200% recovery. This was likely due to non-carbohydrate carbon-containing species in that sample). The precision of the technique was always better than 20% relative standard deviation (n = 10). The detection limits for carbon range from 0.4 to 3 mg L^{− 1}, and absolute detection limits range from 12 ng to 90 ng for a 30 μL aliquot of sample on the coil. This method could be an alternative approach for determining the carbon content of nonvolatile compounds, and complement HPLC–ICP-AES determination of those same species.     

果汁中天然色素紫胶红的UPLC/TUV定量检测及UPLC - MS/MS结构确证

建立了天然色素紫胶红各组分的UPLC/TUV定量检测及UPLC - MS/MS结构确证方法,并将所建立的分析方法应用于果汁中紫胶红色素的定性定量检测.通过Oasis(R) HLB小柱固相萃取技术净化、提取果汁饮料样品中的紫胶红色素.使用Waters Acquity UPLC BEH Shield RP C18(1.7 ...     

氮硫共掺杂碳量子点对胃液pH值的精确检测

以水杨酸和硫脲为原料, 通过水热法一步合成水溶性好、 稳定性强、 量子产率高(36.23%)、 呈蓝光的氮硫共掺杂碳量子点(N,S-CQDs). 在302 nm波长激发下, N,S-CQDs在发射波长409 nm处的荧光强度与pH值(在2.01~5.11范围内)线性关系良好, 相关系数为0.9931, 可原位、 实时检测胃液内pH值在Δ0.01范围内的变化. 可用于胃癌早期诊断和新生儿健康防护. 400 μg/mL N,S-CQDs孵育铜绿微囊藻细胞48 h, 存活率82.8%, 其可作为人体胃细胞荧光探针, 经人体排泄进入水环境, 对淡水浮游生物毒性低, 环境友好.     

Metabolic and Isotopic Correlations between D-Glucose,L-Ascorbic Acid and L-Tartaric Acid

Abstract

L-Ascorbic acid in fruit juices is enriched in ¹³C by 4.8 δ-units relative to its precursor glucose, and this enrichment is mainly located in position C-1. On the other hand, biotechnologically produced L-ascorbic acid preserves the pattern as expected from glucose. In grapes L-tartaric acid is synthesized from glucose via L-ascorbic acid and it is one of its main products. It preserves C-atoms 1 to 4 from glucose and the measured δ¹³C-value is identical to that calculated from this precursor.

The findings are interpreted as overlapping influences of isotope discriminations after metabolic branching and relative turnover rates leading to isotopic balances. The results can also be used to distinguish between identical products by different synthetic processes.     

Ultrasonic and other sterilization methods on nutrition and flavor of cloudy apple juice

Sterilization plays an important role in extending the shelf-life of apple juice; however, it also affects the nutritional and flavor profile of the juice. This study was initiated to evaluate the effects of several common sterilization methods (conventional pasteurization, microwave sterilization, ultrasonic sterilization, and ultra-high-pressure sterilization) on some important quality parameters of apple juice. The results showed that the content of soluble pectin and soluble protein in juice decreased significantly after ultra-high-pressure sterilization. Sonication was found to be effective in increasing the level of ascorbic acid in apple juice. The sugar:acid ratio increased significantly after pasteurization, microwave sterilization, and ultra-high-pressure sterilization, which changed the taste of juice. Microwave sterilization caused the highest volatile compound loss, while ultra-high-pressure sterilization led to a higher retention rate of volatile compounds in juice. This study could be helpful in seeking suitable sterilization methods retaining the quality of cloudy apple juice.     

Concentration of noni juice by means of osmotic distillation

Osmotic distillation (OD) or osmotic evaporation (OE) is a promising membrane process generally applied to concentrate solutions under isothermal conditions. In this work, this process was applied to concentrate commercial noni juice (Morinda citrifolia). Several nutraceutical properties have been reported for noni-derived products, mainly associated to the phenolic content of the fruit.The analyzed system is an osmotic distillation system where the solutions are circulated through a hollow fiber membrane contactor operating in transient configuration with circulation rates between 0.1 and 1.0 L min⁻¹ and concentrated solutions of CaCl₂ were used as extraction brine. At isothermal conditions (30 °C), transmembrane vapor water flux was experimentally determined from 0.090 up to 0.413 kg h⁻¹ m⁻². Noni juice was concentrated from 8 to 32 °Brix after 60 min of treatment. The content of phenolic compounds was preserved after this processing.Simulation algorithms based on phenomenological equations of heat and mass transfer were developed considering a resistances-in-series model to predict the performance of the process from theoretical information. The values of transmembrane water flux obtained by simulations showed deviations between 2.35 and 16.19% with the experimental ones for the operating conditions applied in this work.     

Optimization of clean-up procedure for patulin determination in apple juice and apple purees by liquid chromatography

Patulin (PAT) is a mycotoxin produced in fruits, mainly in apples, by several fungal species that can be carried into industrial apple juice by-products during factory processing. An analytical method for determination of PAT in apple juice and another one for determination of this compound in apple purees and apple compotes by liquid chromatography are proposed in the present paper. These methods have better precision and sensitivity than previously reported methods and focus mainly on extraction and clean-up. To accomplish analytical methods with higher accuracy, lower limits of detection and simpler procedures for application in quality control of the goods, different extraction and clean-up procedures for PAT were comparatively studied. PAT recoveries in apple juice spiked with 1.0 mg PAT/kg varied between 52.3% and 81.0%. The highest PAT recovery in apple puree spiked with 0.1 mg PAT/kg was 82.9%. Addition of NaH₂PO₄ during the extraction phase here reported for the first time has the advantage of keeping the pH slightly acidic, thus avoiding PAT degradation.