液相色谱法测定多元维生素片中4种水溶性维生素

采用高效液相色谱法测定多元维生素片中盐酸硫胺(B1)、核黄素(B2)、泛酸钙(B5)、盐酸吡哆醇(B6)的含量。重点考察了提取条件对于维生素测定的影响,4种维生素在确定的浓度范围内分别与色谱峰面积呈良好的线性关系,r2≥0.9999,加标回收率为99.2%～101.4%。4种维生素的检出限分别为0.30、0.19、0.45、0.11μg/g(S/N10)。该方法可作为实际测试标准方法使用。     

高效毛细管电泳电导法快速检测复方维生素B片中的VBl、VBl2、VB6和VC

采用高效毛细管电泳电导法同时分离、测定了复方维生素B片中的主要成分VB1，VB12，VB6和VC的含量。研究了运行缓冲溶液的酸度和浓度、电泳电压、进样时间等因素对电泳的影响。在优化的实验条件下：40mmol/L Tris-4mmol/L H3BO3(pH8．0)的缓冲溶液中加入0．30mmol/L CTAB(溴化十六烷基三甲基铵)，分离电压为15kV，上述4组分在5min内得到良好的分离。维生素B1，B12，B6和VC的线性范围分别为5．5～1．0mg/mL；15～1．5mg／mL;1．0～0．40mg／mL和6．6～0．80mg／mL；检测限分别为0．80μg/mL，4．0μg/mL，0．50μg/mL，2．9μg/mL；5次测定峰高的相对标准偏差分别为2．2％，1．6％，3．9％，2．8％。5次测定的平均回收率分别为99％，94％，l00％，97％。     

多壁碳纳米管修饰电极同时测定维生素B2、B6、B12和维生素C

制备了多壁碳纳米管修饰玻碳电极(MWNT/GCE),研究了维生素B2、B6、B12和维生素C共存时在该电极上的电化学行为.实验发现,在HAc-NaAc缓冲溶液中,该电极可同时测定以上四种维生素,线性范围分别为1.0×10-6～1.0×10-4 mol/L、5.0×10-5～2.0×10-3 mol/L、5.0×10-5～7.5×10-4 mol/L和5.0×10-5～2.0×10-3 mol/L,其检出限分别为7.0×10-7 mol/L、1.0×10-5 mol/L、2.5×10-5 mol/L和5.0×10-6 mol/L.样品分析的RSD分别为1.66%、1.71%、2.26%和1.46%.方法简便快捷,可用于四种维生素同时分析测定.     

维生素B1、B6与金属离子关系的光化学研究

分别研究了必需微量元素铁、锌、铜、锰、硒、常量元素钙、镁、非必需元素铝、锂，有毒元素尔，铅，镉对维生素B1、B6的紫外吸收光谱的影响，并对其机理进行了初步探讨。所得结果对于金属离子与维生素B1、B6的关系及其在人体中的生化、生理功能和生物有效性提供了一定的理论依据。     

维生素对微量元素吸收利用的影响

维生素A：维生素A能增强硒抑制癌症的作用。缺乏对微量元素吸收利用维生素A可妨碍铁的吸收利用。 维生素B族：有学者发现给缺乏维生素B6饮食的鼠组织中锌含量降低,而缺乏维生素B1和维生素B2并不产生此现象,已证明维生素眈缺乏引起的锌吸收障碍,是由于PA（色氨酸的代谢产物）减少所致。     

维生素B6在维生素B12修饰电极上的电化学行为及其分析应用

采用循环伏安法研究了维生素B6在维生素B12修饰玻碳电极上的电化学行为,建立了测定痕量维生素B6的新方法.在pH 8.6的NH3-NH4Cl缓冲溶液中,维生素B6在修饰电极上产生一个灵敏的氧化峰,采用差分脉冲伏安法测定,其氧化峰电流与维生素B6的浓度在8.0×10-7～2.0×10-4 mol/L范围内呈良好的线性关系,检出限为2.0×10-7 mol/L.该修饰电极具有良好的选择性、灵敏度及稳定性,用于片剂中维生素B6的定量分析,结果令人满意.     

离子对反相高效液相色谱法同时测定复合维生素片中4种水溶性维生素

采用离子对反相高效液相色谱法同时测定了复合维生素片中烟酰胺、维生素B1、维生素B2、维生素B6等4种水溶性维生素的含量。样品经水溶解、过滤后,以Hypersil C18化学键合硅胶为固定相,以甲醇-0.5%(体积分数)醋酸水溶液(含2.5 mmol/L己磺酸钠,pH 2.8)(体积比为18∶82)为流动相,等度洗脱,紫外检测器于280 nm波长下检测。当烟酰胺、维生素B1、维生素B2和维生素B6的质量浓度分别在25450 mg/L,590 mg/L,2.590 mg/L,595 mg/L时,其峰面积与质量浓度的线性关系良好;日内测定平均相对标准偏差(n=7)分别为1.0%,2.2%,1.8%和1.3%;日间测定相对标准偏差(n=5)分别为1.5%,3.6%,2.4%和1.7%。该方法已成功应用于复合维生素片中4种水溶性维生素的同时测定。     

导数－同步荧光光谱法同时测定三种B族维生素的研究

研究了维生素B₁的氧化产物(硫色素)、维生素B₂和B₆混合物体系的导数-同步荧光光谱,提出了混合物体系荧光光谱被分辨开的同时测定方法。该法可不经分离直接测定复合维生素片剂中维生素B₁、B₂及B₆,其线性范围均为0～1.0μg/mL,检出限分别为0.5、1.5及4.0ng/mL.     

The Hydrotrope Action of Vitamin C

The effects of vitamin C are determined in the oil-in-water(0/ W) and water-in-oil(W/ 0) microemulsion regions of CTAB/ pentanol/ p-xylene/ H20 system. The addition of Vc joins the O/ W and W/ O areas in the phase diagram and expands the bicontinous region by reducing the lamellar liquid crystal one. The results show that the “ coupling action” of Vc is in fact a structural transition from lamellar crystal to isotropic phase with W/ O, O/ W and bicontinous structure.     

The Vitamin D Status Among Tibetans

UVB from the sun and intake from food are the only human sources of vitamin D. Tibet is a unique region for comparisons of these sources: (1) it lies at a low latitude and at a high altitude and has very large annual fluences of UVB; (2) the traditional Tibetan food is poor in vitamin D. Blood samples were taken from 63 persons of different age, with different occupations and staying at different places. UVB doses at these places were measured. The samples were analyzed by a standard radioimmune assay for determination of the serum concentration of 25 hydroxyvitamin D (25(OH)D). The main finding was that among nomads, there seems to be severe vitamin D deficiency (serum levels of 25(OH)D < 30 n m ). We tentatively propose that the low level of 25(OH)D of nomads is related to their clothing and sun exposure habits. For persons of other occupations (students, teachers and farmers) the levels are higher, although a significant fraction of these persons also have lower levels than 75 n m , by many regarded as a limit for insufficiency related to a number of negative health conditions. The annual dose of vitamin D-generating UVB is about five times larger in Lhasa than in Oslo. Despite this, the average vitamin D status seems to be similar, except in the case of nomads. This phenomenon is certainly related to food habits. In conclusion, the 25(OH)D status among nomads in Tibet appears to be alarmingly low. However, for people of other occupations the status is more normal.     

Maximal orbital analysis of molecular wavefunctions

We describe a new way to decompose one-electron orbitals of a molecule into atom-centered or fragment-centered orbitals by an approach that we call “maximal orbital analysis” (MOA). The MOA analysis is based on the corresponding orbital transformation (COT) that has the unique mathematical property of maximizing any sub-trace of the overlap matrix, in Hilbert metric sense, between two sets of nonorthogonal orbitals. Here, one set comprises the molecule orbitals (Hartree–Fock, Kohn–Sham, complete-active-space, or any set of orthonormal molecular orbitals), the other set comprises the basis functions associated with an atom or a group of atoms. We show in prototypical molecular systems such as a water dimer, metal carbonyl complexes, and a mixed-valent transition metal complex, that the MOA orbitals capture very well key aspects of wavefunctions and the ensuing chemical concepts that govern electronic interactions in molecules. © 2019 Wiley Periodicals, Inc.     

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本文对近10年来出现的新型离子液体进行了分类综述,并对其发展前景提出了一些见解.     

The Spectrophotometric Determination of Vitamin a Using Iodine

Abstract

Methods are described for the spectrophotometric determination of vitamin A (0.15–12.5 μg) using iodine as the chromogenic reagent. The reaction is most sensitive in chloroform. Vitamin D₂ and ß-carotene do not interfere if the analysis is carried out in 1, 2 -dichloroethane.     

The Role of Vitamin C,Vitamin D,and Selenium in Immune System against COVID-19

Low levels of micronutrients have been associated with adverse clinical outcomes during viral infections. Therefore, to maximize the nutritional defense against infections, a daily allowance of vitamins and trace elements for malnourished patients at risk of or diagnosed with coronavirus disease 2019 (COVID-19) may be beneficial. Recent studies on COVID-19 patients have shown that vitamin D and selenium deficiencies are evident in patients with acute respiratory tract infections. Vitamin D improves the physical barrier against viruses and stimulates the production of antimicrobial peptides. It may prevent cytokine storms by decreasing the production of inflammatory cytokines. Selenium enhances the function of cytotoxic effector cells. Furthermore, selenium is important for maintaining T cell maturation and functions, as well as for T cell-dependent antibody production. Vitamin C is considered an antiviral agent as it increases immunity. Administration of vitamin C increased the survival rate of COVID-19 patients by attenuating excessive activation of the immune response. Vitamin C increases antiviral cytokines and free radical formation, decreasing viral yield. It also attenuates excessive inflammatory responses and hyperactivation of immune cells. In this mini-review, the roles of vitamin C, vitamin D, and selenium in the immune system are discussed in relation to COVID-19.     

The Measurement of Nanogram Quantities of Vitamin D3

Abstract

An isotope dilution method is described for the measurement of nanogram quantities of vitamin D₃ (cholecalciferol). Use is made of the Diels -Alder reaction between vitamin D₃ and tetracyanoethylene.

Increasing quantities of exogeneous vitamin D₃ added to a standard reaction mixture of ¹⁴C-labelled vitamin D₃ and tetracyanoethylene produced a decrease in the ratio of reacted to unreacted vitamin D₃. The ratio (y) was measured by radio-scanning of an eluted thin-layer chromatogram, and quantitation of added vitamin D₃ was thereby achieved.