人工神经网络-荧光光谱法同时测定维生素B1,B2,B6

应用人工神经网络原理 ,以Levenberg MarquardtBP算法对荧光光谱严重重叠的维生素B1 ,B2 ,B6三组份混合体系同时进行了含量测定。在 390～ 5 2 0nm的范围内 ,以 15个特征波长处的荧光强度值作为网络特征参数 ,并通过均匀设计安排样本 ,经网络训练和计算得出维生素B1 ,B2 ,B6 三者的平均回收率分别为 99 86 % ,99 6 0 % ,99 4 9% ,测定结果的相对标准偏差各为 1 7% ,1 6 % ,1 7%。     

荧光熄灭法测定维生素K3针剂中甲萘醌的含量

本文利用荧光熄灭法对维生素K3针剂中甲萘醌含量的测定进行了研究，工作结果表明：荧光熄灭法测定甲萘醌较常规的VK3针剂分析方法快速、准确，相对标准偏差小于3％，回收率在96％－102％。     

导数光谱法同时测定甲硝唑和维生素B6的研究

本建立了以０．１ｍｏｌ／ＬＨＣｌ为介质，采用三阶导数光谱法，同时测定甲硝唑和维生素Ｂ６的新方法，方法检测限为０．８１μｇ／ｍＬ甲硝唑和０．１６μｇ／ｍＬ维生素Ｂ６，二测定的线性范围均为１．６－２２．４μｇ／ｍＬ，直接用于复方甲硝唑片剂中甲硝唑和维生素Ｂ６的测定，两种生物的测定变异系数分别小于２．２６和２．６０％，回收率分别为９３－１０２％和９９－１０１％．     

苦瓜中维生素C含量的测定

建立苦瓜中维生素C含量直接测定新方法。以10%盐酸溶液为溶剂,采用紫外分光光度法测定含量。维生素C在0—10μg/mL浓度范围内与吸光度呈良好的线性关系,回归方程为：y=0.04746C＋0.00109,r=0.9997。检出限为0.023μg/mL,加标回收率在94.8%—101.1%之间。该法操作简单,干扰离子少,结果准确,测量快速、准确度和灵敏度高,可应用于维生素C含量的测定。     

HPLC法对医学生血清维生素A含量的测定

建立快速提取血清中维生素A和运用HPLC测定其含量的方法。取待测血清200μL,加入无水乙醇液200μL,旋涡混合1min,再加入正己烷溶液400μL,旋涡混合3min,离心后取上清液,用高效液相色谱仪测定。色谱条件：分析柱为Kromasil100-5C18（150×4.6mm,5μm）;流动相为甲醇∶水（98∶2,V/V）;流速为1.2mL/min;检测波长为325nm。血清中维生素A分离良好,浓度在2—80μg/dL范围内呈线性关系,r2=0.9992。平均回收率为98.48%,日内、日间RSD均〈10%。所测医学生血清中维生素A的含量男性为（38.65±12.99）μg/dL,女性为（34.17±10.10）μg/dL。该法操作快速、样品处理简便易行,适用于血清中维生素A的快速提取和含量的测定。     

分光光度法测定柚子中的维生素C

柚子是一种含维生素C较高的水果,采用2,4-二硝基苯肼法对柚子中的维生素C含量进行测定.先进行波长扫描,确定维生素C的最大吸光度在510nm.然后绘制校准曲线,得到校准曲线方程y=0.0545x+0.053(r=0.9992),测定矮晚柚的平均维生素C含量为75.89mg/100g.并做了3个柚类品种的加标回收实验,回收率都在90％以上,说明此种方法准确率高,方法可行,可用于水果、蔬菜维生素C含量的测定.     

反向高效色谱法测定维生素E中α-V_E含量

采用反相高效液相色谱法测定维生素E中α-VE的含量。C18柱为色谱柱。甲醇/水（100∶0）为流动相,流速为1.0mL/min.检测波长为292nm。线性范围50—100μg/mL,r=0.9993,维生素E中α-VE的含量为84.82mg/L。本法操作简便,样品分离效果好,回收率高,结果准确可靠。     

紫外分光光度法测定维生素B_6

本文建立了以 0 .0 35 mol/ L HAc(醋酸 )为介质 ,采用紫外分光光度法测定维生素 B6的新方法。该方法体系简单 ,操作方便、快速、灵敏 ,其表观摩尔吸光系数ε为 9.37× 10 4 L· mol-1· cm-1。线性范围为0 .61— 4 0 .10μg/ m L。用于 VB6片剂和针剂测定 ,回收率为 10 0 .82 %— 10 1.90 %     

水果、蔬菜中维生素C含量的测定——紫外分光光度快速测定方法探讨

本文利用维生素C具有对紫外产生吸收和对碱不稳定的特性,建立了紫外分光光度快速测定水果、蔬菜维生素C含量的新方法.维生素C浓度在1.00-12.0μg/mL范围内与吸收值呈良好的线性关系;检出限为0.014μg/mL;加标回收率在97.9%-99.0%之间.该法操作简单,结果准确,应用于维生素C含量的测定,结果令人满意.     

同步荧光法测定食品中维生素B1

本文研究了食品中维生素Ｂ１的同步荧光法测定条件，采用氯化钾－乙醇作柱层析洗脱液，碱性介质中氧化后立即调为中性，并加入表面活性剂ＯＰ对体系增稳增敏，取代丁醇萃取，经济方便，用于几种粮食样品的测定，结果满意。     

异丙醇-水配合液的荧光偏振和时间分辨特性

研究了紫外光照射下异丙醇-水配合液的偏振荧光光谱,以及不同荧光峰处光子强度随时间的衰变过程,计算了偏振度并讨论了其偏振特性,测试了不同峰位对应的荧光寿命并分析了其荧光发射特性.结果表明,异丙醇-水配合液在紫外光激励下发射的荧光为具有确定分子取向的部分偏振光,偏振度和各向异性度分别为0.542和0.441.在波长为220...     

高效液相色谱测定卷烟及其主流烟气中的维生素E

样品用饱和抗坏血酸乙醇溶液萃取,ZORBAX Extend-C18（5μm,4.6×150mm）色谱柱及FLD检测器在激发波长为298nm,发射波长为325nm下检测,流动相为100%甲醇。采用外标法定量,线性相关系数为0.99996,检出限为0.12μg/mL,卷烟及其主流烟气中维生素E平均回收率分别为97.0%和97.4%,RSD分别为0.70%和4.70%。研究表明：烤烟型卷烟烟丝比混合型卷烟烟丝中维生素E含量高,烤烟型卷烟主流烟气比混合型卷烟主流烟气中维生素E含量高,维生素E从卷烟烟丝到主流烟气的迁移率为7%—16%。     

紫外光分光光度法测定淫羊藿中维生素C的含量

紫外光分光光度法测定淫羊藿中维生素C含量。测定波长为243nm;维生素C浸提剂为1.0%（V/V）盐酸溶液;维生素C浓度在2—50mg/L范围内与吸光度线性关系良好（r=0.9992,n=3）;回收率在97%—115%之间（n=3）;相对标准偏差都小于6.0%（n=3）;检出限（LOD）和定量限（LOQ）分别为1.33mg/L和4.04mg/L。人工栽培的箭叶淫羊藿、天平山淫羊藿和长蕊淫羊藿鲜叶中维生素C的含量不同。     

藏药迷果芹脂溶性成分分析

采用气相色谱-质谱（GC-MS）联用技术对藏药迷果芹的脂溶性成分进行分析.从藏药迷果芹石油醚萃取物中分离鉴定出26种化合物,占其总量的98.77％.在已鉴定的化学成分中,含量较高的化学成分依次为亚油酸（35.90％）、芹菜脑（23.98％）、棕榈酸（11.41％）、亚油酸乙酯（4.08％）、亚油酸甲酯（4.06％）、β-谷甾醇（4.40％）.本研究为开发迷果芹资源提供了科学依据.     

间接分光光度法测定药物中的维生素E

在表面活性剂CTMAB存在下,维生素E能够定量将Fe(Ⅲ)还原为Fe(Ⅱ)离子,利用显色剂5-硝基-1,10菲咯啉建立了间接分光光度法测定维生素E的方法,在pH 4.6的乙酸-乙酸钠缓冲溶液中,Fe(Ⅱ)-5-硝基-1,10-菲咯啉络合物的最大吸收峰位于502nm处,维生素E的含量在0.3—2.0 mg·L-1范围内符合比耳定律,表观摩尔吸光系数ε502=2.43×104L·mol-1·cm-1。本法用于维生素E片剂、胶丸及注射液中维生素E含量的测定,与药典法对照,2种方法所得结果一致。     

Dehydration reaction of hydroxenin monoacetate in carbon tetrachloride and an aliphatic alcohol under ultrasound irradiation

A new method for the preparation of an E/Z mixture of vitamin A acetate from hydroxenin monoacetate is described. This two-step reaction was studied by changing the reaction parameters (reaction temperature, ultrasound power, and reaction time) and the alcohol used. This approach consists of the dehydration reaction of hydroxenin monoacetate under ultrasound irradiation in CCl4 and an aliphatic alcohol under an inert atmosphere. The formation of small amounts of HCl from CCl4 and an aliphatic alcohol under ultrasound irradiation is followed by the dehydration reaction of hydroxenin monoacetate. An E/Z mixture of vitamin A acetate was obtained resulting in the desired pentaenes. Some ethers derivatives were also formed as by-products, isolated and characterized. Study of the reaction mechanism is also reported here.     

Measurement of the effect of high-power ultrasound on wetting of paper

High-power ultrasound has been known to promote penetration of liquids into porous materials. This work presents results of experimental investigations of the influence of 40 kHz high-power ultrasound on wetting processes of papers. Wetting was monitored by the measurement of the attenuation of 0.5-9 MHz ultrasound transmitted through the immersed sample. The samples were sized papers with contact angles 40 degrees, 70 degrees and 110 degrees, and the immersion liquids were isopropanol-water mixtures of 0-100% isopropanol concentration. The investigation showed that application of high-power ultrasound resulted in faster sorption processes. However, the absolute reduction in time to reach the stationary state was not very great.     

定量核磁共振法同时测定复合维生素B片中B1、B2、烟酰胺和泛酸钙

建立了同时测定复合维生素B片中4种有效成分——维生素B1(VB1)、维生素B2(VB2)、烟酰胺和泛酸钙的定量核磁共振氢谱(~1H qNMR)方法.选择延迟时间(D_1)为1.0 s、脉冲宽度(P_1)为3.0μs、采样次数(NS)为500次.以对苯二甲醛为内标,其质子峰δ10.12(2H)为内标峰;溶剂为氘代二甲亚砜(DMSO-d_6).定量峰的化学位移VB1选择δ9.60~9.90(~1H),VB2选择δ11.36(~1H),烟酰胺选择δ9.01(~1H),泛酸钙选择δ0.78(12H).通过标定VB1和泛酸钙对照品的纯度,测定各成分的零截距标准曲线斜率与理论值相符,说明可以直接用绝对定量公式计算其含量.测定各成分的回收率均接近100%,且重复性很好.结果表明该方法准确度高、结果可靠,可用于复合维生素B片中VB1、VB2、烟酰胺和泛酸钙含量的测定.     

EPR Study of γ-Irradiated UHMWPE Doped with Vitamin E: Assessment of Thermal Effects on the Organic Radicals During Vitamin E Diffusion

Thermal effects on ultra-high-molecular-weight polyethylene (UHMWPE) residual radicals during the vitamin E diffusion process were studied in detail. Electron paramagnetic resonance (EPR) technique showed a significant reduction in concentrations of radiation-induced primary (alkyl (–CH₂– ^?CH–CH₂–), allyl (–CH₂–^?CH=CH–CH–CH₂–) and polyenyl (–^?CH–[CH=CH–] _m –) with m > 3) radicals for both control and vitamin E-doped samples. The concentrations of radiation-induced primary radicals (RIPRs) were found to decrease proportionally with the heat/diffusion time. While the EPR spectra of the control samples showed only polyethylene (PE) radicals, the spectra of vitamin E-doped samples were found to exhibit vitamin E radicals in addition to PE radicals. Of particular interest, the heat involved during vitamin E diffusion plays a significant role in reducing the radiation-induced primary radicals of UHMWPE. For 120 min of heat/diffusion time, the available quantity of primary radicals in control samples were found to be ~7.5 % of initial radicals. The leftover amounts of these primary radicals for vitamin E-doped samples were approximately ~10.0 %. In addition to this, EPR power saturation techniques were also used to assess the effects of initial heat/diffusion treatment on the oxygen-induced residual radicals (OIRRs): R₁ (–^?CH–[CH=CH–] _m –) with m > 3 and R₂ (^?OCH–[CH=CH–] _m –) with m = 2 or 3. It was found that the concentration of OIRRs also decreases proportionally with initial heat/diffusion time. The remaining amount of OIRRs relative to leftover RIPRs after heat/diffusion was found to be approximately 4.0 % in controls and was still found to be 10.0 % in vitamin E-doped UHMWPE. This may indicate that vitamin E slows down the oxidation processes, which may contribute to the strong oxidation resistance of vitamin E-doped UHMWPE.     

Improvement in Retinol Analysis by Fluorescence and Solid Phase Extraction (SPE) in Micellar Medium

In this paper, the determination of retinol, the structure with the most activity as vitamin A, was carried out in an aqueous micellar medium with a low quantity of a short-chain alcohol. The analytical technique used in this work was fluorescence, which gave us very much information qualitative and quantitative. The sensitivity of the method is higher than that obtained in other media; the detection limit is 0.03 mg L⁻¹ and retinol was stable in solution for at least 5 days. The use of solid phase extraction (SPE) for organic samples, allowed us to change the organic matrix by a mixture CTAB 5%/n-butanol 10%/water 85% w/w/w with recoveries in retinol spiked samples close to 100%. In addition, the combination of SPE and fluorescence is a good preconcentration technique, sensitive and fast for the identification and determination of retinol, simultaneously.