等摩尔吸收点二甲酚橙光度法测定紫菜中钙和镁

在pH=10.5的NH3-NH4Cl缓冲溶液中,Ca2+、Mg2+均与二甲酚橙形成紫色配合物。研究以二甲酚橙为显色剂,利用等摩尔吸收点光度法测定Ca2+、Mg2+含量的方法。实验表明,等吸收点测定波长为λ=584 nm,最佳实验条件下,Ca2+、Mg2+总量在0~6.0×10-5 mol/L范围内符合Lambert-Bill定律,检出限为7.2×10-6 mol/L。该法用于紫菜中钙镁含量的测定,方法的相对标准偏差为3.6%,加标回收率为96.0%。     

多波长分光光度法测定牛乳中钙和镁

研究了在pH12时,铬天青S（CAS）-溴化十六烷基三甲铵（CTMAB）-钙和镁显色体系。采用盐酸煮沸分解,净化,借助于K-矩阵法同时测定了牛乳中钙和镁。结果表明,该方法对牛乳中钙和镁的添加回收率分别为102.0%～103.3%和103.3%～110.0%。      

多波长分光光度法测定牛乳中钙和镁

研究了在pH12时,铬天青S(CAS)-溴化十六烷基三甲铵(CTMAB)-钙和镁显色体系。采用盐酸煮沸分解,净化,借助于K-矩阵法同时测定了牛乳中钙和镁。结果表明,该方法对牛乳中钙和镁的添加回收率分别为102.0%～103.3%和103.3%～110.0%。     

干法灰化-离子色谱法测定烟草中的钾、钙和镁

建立了测定烟草中钾、钙和镁的干法灰化-离子色谱方法。结果表明:①钾、钙和镁3种元素可以实现一次进样,同时测定;②相对平均标准偏差RSD<5%;③加标回收率分别为98.0%~105.0%,98.6%～102.3%,97.0%～104.9%;④检出限分别为0.06,0.03,0.05μg/mL。     

微波消解-火焰原子吸收光谱法测定市售3种珍珠粉中金属元素

采用微波消解法处理样品,用硝酸-双氧水(体积比6∶1)混合溶液作为消解剂进行微波消解,火焰原子吸收光谱法测定了市售3种珍珠粉中锌、钠、镁、铁、钙、铜、锰、锶等8种金属元素含量。8种元素检出限(3S/N)在0.000 6～0.024 8 mg/L,回收率95%～105%,相对标准偏差(n=10)<5%。试验结果表明:3种珍珠粉样品中8种金属含量的数值变化趋势较为一致,其中钙含量最高,含量均达34.15%以上,锰、锶、铁、钠的含量也较为丰富,均在94.74μg/g以上,而锌、镁、铜含量相对较少,均少于11.78μg/g。从珍珠粉的主要成分金属元素钙的含量测定结果可以推断出3种珍珠粉的品质有所差别,钙含量低的质量相对差。     

大量锶存在下用原子吸收分光光度法连续测定微量钙、镁

使用带数字显示和记录仪的 WFX-2型双光束原子吸收分光光度计,研究在含有大量锶存在的天青石中微量钙、镁的测定,其最适宜的条件是有镧存在。1:1盐酸用量控制占测定体积的2%,选用吸收波长钙4227(?),镁2852(?),其线性范围钙1—5微克/毫升,镁0.1—0.5微克/毫升。因为钙、镁在该试验条件下,相互之间不干扰,所以能在同一溶液中连续测定钙和镁。对低含量的钙,特别是微量的镁,结果是令人满意的。此法避免了化学法从锶、钡中分离钙用有机溶剂萃取等繁琐手续。     

流动分析法测定卷烟纸中的钙、镁含量

考察了消化液体积和温度对卷烟纸中钙和镁含量检测结果的影响,并采用该方法和离子色谱法检测了20个卷烟纸样品.结果表明:①卷烟纸样品消化的适宜条件:卷烟纸样品0.2 ～0.3 g;消化液5 mL硝酸-高氯酸混合液;消化温度300℃;消化时间1h;②钙、镁的RSD分别为0.93%,2.95%,回收率为96.7% ～ 102.9%和98.6%～106.7%;③国产卷烟纸样品钙、镁含量的均值各为117.4和1.09 mg/g,进口卷烟纸样品钙、镁含量均值116.0和1.17 mg/g;④2种方法的钙、镁含量检测值在0.05水平下无显著性差异.该法适合于卷烟纸中钙和镁含量的分析.     

奶粉中钠、钾、镁、钙的"动态透析"离子色谱法测定研究

目的:探索出较为简便易行的奶粉中钠、钾、镁、钙同时测定的方法。方法:使用透析袋将溶解后的奶粉透析后取出分别过C18柱分离后使用20mol/L甲烷磺酸作为淋洗液,用离子色谱法同时分离和测定奶粉中钠、钾、镁、钙这四种物质。结果:选择转速为200r/min室温下动态透析平衡时间只要2h左右,四物质离子色谱峰形较好,其他离子对它的干扰较小,RSD%均小于5%,回收率在95%～105%之间。结论:奶粉中钠、钾、镁、钙的"动态透析"离子色谱法测定是一种较为实用的测定方法。     

分光光度法测定大麦苗粉中脱镁叶绿酸的含量

以建立测定叶绿素类产品中脱镁叶绿酸含量方法为主要目的,采用85%丙酮和乙醚萃取色素,经17%的盐酸溶液酸化后,用可见分光光度计测定667 nm下样品的吸光值,计算出脱镁叶绿酸的含量.结果表明:脱镁叶绿酸浓度在0.13mg/L～127mg/L范围内具有良好的线性关系,回归方程为Y=0.027 5X+0.002 5,R2=0.999 8.加样平均回收率为90.0%.     

微波消解-电感耦合等离子体质谱法同时测定雄蚕蛾中8种元素

目的 建立微波消解-电感耦合等离子体质谱(inductively coupled plasma mass spectrometry, ICP-MS)法同时测定雄蚕蛾中钠、锰、镁、铜、钙、铁、硒和锌8种元素的含量的方法。方法 样品经硝酸-过氧化氢微波消解后, 通过在线加入内标溶液校正, 以72Ge为内标, 采用ICP-MS测定雄蚕蛾中钠、锰、镁、铜、钙、铁、硒和锌8种元素的含量。结果 8种元素线性良好, 相关系数为0.9995~0.9999; 钠、锰、镁、铜、钙、铁、硒和锌的检出限分别为0.04、0.0004、0.003、0.003、0.01、0.004、0.0005、0.006 mg/kg; 8种元素的回收率在91.3%~98.6%之间, 相对标准偏差(relative standard deviation, RSD)≤3.7%(n=6)。结论 该方法灵敏度高、稳定性好, 可以满足雄蚕蛾中钠、锰、镁、铜、钙、铁、硒和锌的同时测定。     

绿茶萃取物溶出变化研究

研究绿茶在50、60、70、80℃水中不同时段萃取时萃出液中茶多酚(EG、EGC、ECG、GGEG)、氨基酸、果胶等的变化。结果显示,游离型儿茶素在冷水中比较容易溶出,3萃时有80%～90%溶出;酯型儿茶素的溶出较慢,3萃时只有50%左右溶出;咖啡因的溶出特性与游离型儿茶素相类似;氨基酸在1萃溶出量较多,从1萃到3萃前,依次下降,除精氨酸外,其他氨基酸在2萃时溶出率达70%～80%,3萃时溶出率为90%～100%,精氨酸在2萃时溶出率为50%,3萃溶出率为70%;钙、镁、磷酸类在1～3萃取中溶出量依次降低;1萃时水溶及盐溶性果胶的萃取率较高。以上参数为茶饮料的工业化生产及品质保证提供参考。     

水热合成法制备高纯度氧化镁

用水热合成法制备了高纯度氧化镁 ,实验发现 ,这种方法是一种分离镁和钙的非常有效的方法 ,与气相氧化法、液相滴下法、Sulmag法、Aman法相比 ,本方法简单 ,产品质量稳定 ,氧化镁含量可达 99.95 %～ 99.98%。适应于工业化生产。     

Estrogen in plasma of parturient paretic and normal cows.

The endocrine factors associated with parturient paresis have not been defined totally. Estrogens stimulate uptake of calcium by bone. Since secretion of estrogen increases dramatically as parturition approaches, estrogen may be involved in homeostatic mechanisms regulating calcium metabolism. Plasma was collected for 30 days (-30) prepartum to 5 days (+5) postpartum from six Holstein and nine Jersey cows approaching three or more lactations. Of all cows, six Jerseys contracted parturient paresis. Estradiol and estrone were analyzed by radioimmunoassay, total calcium and total magnesium by atomic absorption spectrophotometry, and total phosphorus by colorimetry. Data were grouped into periods respresenting days -30 to -21, -20 to -11, -10 to -6, -5 to -4, -3 to -2, -1, 0 (parturition), +1, +2 to +3, and +4 to +5. Calcium in plasma was lower in parturient paresis cows on days +1 and +2 to +3, and magnesium was higher during the same periods but lower on days -4 to -5. Total phosphorus, estrone, and estradiol of normal cows and those with parturient paresis were not different. During the entire sampling period, phosphorus and estradiol were similar in both groups while magnesium was higher and calcium lower in cows with parturient paresis. Estrone was lower in cows with parturient paresis. Lower estrone in cows with parturient paresis may be predisposing for parturient paresis.     

Synthesis of protodolomite from coral reef sand

Protodolomite (calcium carbonate, PD) is widely used in calcium (Ca) and magnesium (Mg) nutritional supplements because it is rich in Ca (>20%) and Mg (>10%). Synthesis of PD usually involves the use of a NaCl solution with Ca²⁺ and Mg²⁺. In this study, we synthesized PD from coral reef sand (CRS) and magnesium chloride (MgCl₂). First, CRS was dissolved in hydrogen chloride (HCl). MgCl₂ was then added to the solution and the concentrations of Ca²⁺ and Mg²⁺ in the solution were adjusted to 150 and 350 mM, respectively. The solution was mixed with sodium carbonate (Na₂CO₃ = 156 mM) and incubated at 40 °C for 2 days in order to precipitate PD. The precipitate was identified as PD by X-ray diffraction analysis and atomic absorption analysis. This is the first study to synthesize PD from CRS, providing a new source of PD for the food industry.     

Reference-material-based collaborative test of flame atomic absorption spectroscopic determination of calcium and magnesium in foods and biological materials

A flame atomic absorption spectroscopic (FAAS) method is described for the determination of calcium and magnesium in a wide variety of foods and biological substrates. Results for reference materials (n = 9) are presented that demonstrate the validity of the procedure. Samples are digested with nitric acid at 150 degrees C in a pressure decomposition vessel, diluted and adjusted to pH 2 with ammonia. Lanthanum chloride solution is added to suppress phosphate interferences and the ionization of calcium and magnesium in the AAS flame. Additional dilutions are made as appropriate, whereupon the atomic absorption of calcium and magnesium is measured in an oxidizing air-acetylene flame. The wavelength settings for calcium is 422.7 nm and for magnesium 285.2 nm. The method was tested in a collaborative trial involving a milk powder practice sample and four test samples, all of which were reference materials. Participants were requested to carry out duplicate determinations exclusively. Results were obtained from 12 laboratories. However, the results of 3 laboratories had to be rejected for various reasons. The remaining set of data was statistically evaluated according to ISO 5725; the method of analysis proved to be precise and accurate. Coefficients of variation values for calcium ranged from 1.19% to 4.44% within laboratories (CVr) and from 5.30% to 15.9% between laboratories (CVR). For magnesium, the corresponding values were CVr, 1.07% to 3.52% and CVR, 3.07% to 5.99%. The method is recommended for the determination of calcium and magnesium at the levels considered in foods and biological substrates.     

SALT SUBSTITUTES IN RESTRUCTURED HAM

Potassium chloride, magnesium chloride, calcium chloride and magnesium sulfate were incorporated to individually substitute 50% of the ionic strength of the sodium chloride in restructured ham. The calcium chloride, magnesium chloride and magnesium sulfate treatments resulted in significantly lower cook yields while those samples with calcium chloride exhibited significantly higher thiobarbituric acid (TBA) values compared to the four other treatments. The calcium chloride and magnesium sulfate treatments produced hams that had significantly different "L", "a", and "b" values compared with the control. The total lipid and cholesterol contents of the various treatments were not significantly different.     

Content of mineral substances in the internal organs of rats on intravenous feeding

The experiments on rats receiving a complete intravenous nutrition (group 1) during 15 days showed that the concentration of natrium, magnesium and iron was increased in the liver and decreased in the spleen as compared to that in controls given normal feeding (group 2). The content of zink and copper (mg%) was significantly lowered in both the organs of rats in group 1. The growth of the liver and spleen mass during parenteral feeding led to a significant rise in the content of natrium, potassium, magnesium, iron, zink and manganese in the whole liver tissue of group 1 rats, while the content of calcium and copper was similar in both groups of animals. The content of natrium, potassium, magnesium, iron and zink in the whole spleen tissue was significantly higher in group 1 rats, while the content of calcium, copper and manganese was similar in both groups of rats. A correlation was revealed between the content of iron and copper in the liver tissue (r = +0.87) and the levels of natrium and magnesium it the spleen tissue (r = +0.78) of group 1 rats. In group 2 rats a correlation was recorded between the content of calcium and manganese in the liver tissue an the levels of natrium and calcium in the spleen (r = +0.85 and +0.86, respectively).     

有机肥、硫酸镁、钙镁磷及石灰在酸性红壤蔗区的施用效应

针对华南酸性红壤蔗区甘蔗生产的土壤限制因子,通过布置田间试验,研究了增施有机肥、镁肥和石灰,以及施用钙镁磷肥对甘蔗农艺、产量及品质性状的影响。结果表明:适量增施石灰、钙镁磷肥及有机肥,可提高土壤p H;不同处理间的甘蔗萌芽没有显著差异,而株高、茎径、蔗产量及蔗糖分等存在差异。与常规处理相比,增施镁肥的甘蔗株高及产量,增施有机肥的茎径及蔗产量,增施石灰的甘蔗糖分有显著提高;同时,与常规处理相比,增施有机肥、镁肥、石灰及施用钙镁磷肥的甘蔗收益分别提高31.93%、40.74%、14.92%和18.74%。     

Redistribution of minerals in apple fruit during storage. Preliminary investigations with the variety spartan

Concentration gradients of dry matter, potassium, phosphorus, magnesium and calcium across median transverse slices were measured on a fresh matter basis at intervals during the storage of Spartan apples in either air or 2% oxygen (<1% carbon dioxide) at 1°C. Proportions of calcium declined in the core and increased, during the first 4 months of storage, in the cortex where calcium rapidly became less extractable with 75% ethanol. Proportions of potassium increased in the inner cortex while those of phosphorus increased in the inner cortex and, during the first 2 months of storage, in the core. Proportions of magnesium declined steadily in the peel and outer cortex with corresponding increases towards the fruit centre. These changes were mainly independent of storage conditions and differences in dry matter concentrations. Calcium and magnesium moved to the core region when core browning developed, especially in the air-stored samples, towards the end of the storage period.     

Support materials for yeast immobilization affect the concentration of metal ions in the fermentation medium

Hydrogels are potential absorbers of ions present in the medium, but they can also release some cations (e.g. calcium in calcium alginates). Polyelectrolytes such as alginic acid and poly(acrylic acid) strongly bind polyvalent metal ions. In this paper, the impact of some materials used for the immobilization of yeast, in particular the concentration of certain ions, especially those that play a significant role in the process of fermentation such as calcium, magnesium, zinc and manganese, was assessed. The support for the immobilization of yeast (calcium alginate and polyacrylate) significantly affected the concentration of metal ions in a model solution. Calcium alginate decreased the concentration of Mg²⁺, Zn²⁺ and Mn²⁺ in the solution by about 10–25%, and greatly increased the Ca²⁺ concentration. Polyacrylate, while swelling, decreased the concentration of cations present by up to 50%. Based on the results in this work, no supplementation of wort with divalent metal salts is advised, since it may lead to a stronger cross‐linking of polyelectrolytes used, and consequently result in a slower fermentation. Similarly, the relatively high concentration of calcium ions, caused by ion exchange, did not appear to affect the fermentation process. Copyright © 2013 The Institute of Brewing & Distilling