卡尔曼滤波分光光度法同时测定铁矿石中钙和镁

本文采用卡尔曼滤波算法，以酸性铬蓝Ｋ与钙，镁的显色体系同时测定钙和镁，利用单纯形优化法确定显色反应的最佳条件，基于测量数据精密度的要求选择了合适的测量波长范围，同时以甲基异丁基酮萃取及氢氧化物沉淀法分离共存的干扰离子，用于实际铁矿石样品分析，所得结果较满意。     

磷酸铵镁法回收稀土分离废水中镁及氨氮的研究

磷酸铵镁法是一种有效的回收氨氮、磷和镁的方法。本文通过热力学计算,分析了反应过程及pH值对磷酸铵镁生成的影响规律。根据理论分析结果,进行了pH值、磷源、加料方式等因素对氨氮、磷去除率的影响实验。结果表明:以Na3PO4为磷源,通过向氮磷混合液中加入含镁废水,并控制反应液pH值为9时,氮磷镁去除率均可达98%以上,得到沉淀物经X衍射分析为六水磷酸铵镁。     

兴多偶氮氯膦Ⅰ光度法测定酸性土壤中的交换性镁

本文研究了Mg-KCPA-I(KCPA-I称为兴多偶氮氯膦I)络合物在醋酸铵介质中的形成条件和组成,共存离子的影响及其消除方法。该法用于土壤交换性镁的测定,获得了较满意的结果。实验部分一、仪器和试剂1.除吸收光谱用721型光度计(波长范围360—800钠米)测定外,其余实验均用72型     

MgCl2在LiCl-KCl熔盐中的电化学特性

研究了温度范围在723-908 K的LiCl-KCl 熔盐体系中MgCl₂的电化学行为和热力学性质. 循环伏安和方波伏安法研究表明镁离子的电化学还原过程为包含了两个电子转移的一步反应. 利用Berzins 和Delahay 方程计算了不同温度下的镁离子的扩散系数, 并通过Arrhenius 公式计算了镁离子在LiCl-KCl 熔盐体系中的扩散活化能. 采用开路计时电位法得到了不同温度下的Mg(II)/Mg(0)体系的平衡电位, 并结合电动势法计算了在LiCl-KCl 熔盐体系中Mg(II)/Mg(0)体系的标准形式电位. 根据不同温度下的标准形式电位, 计算得到了MgCl₂在LiCl-KCl 熔盐体系中的熵变和焓变以及不同温度下的活度系数.     

三种方法联合测试硝酸-氢氟酸-醋酸混酸组成

提出了测定硝酸-氢氟酸-醋酸体系各酸的方法。采用紫外分光光度法、沉淀法分别测试硝酸和氢氟酸含量,电位滴定法测定总酸含量,减去硝酸和氢氟酸得到醋酸含量。分光光度法测试硝酸相对标准偏差(RSD)在0.20%左右,沉淀法测试氢氟酸RSD不大于0.81%,该法测试醋酸RSD在0.40%左右,并进行了样品加入回收和空白加入回收验证。     

溴邻苯三酚红-溴化十六烷基三甲铵分光光度法测定钢铁中的钨

用钨(Ⅵ)-溴邻苯三酚红(BPR)-溴化十六烷基三甲铵(CTMAB)体系测定钢铁中微量钨时,以盐酸羟胺、抗坏血酸、CyDTA和氟化钠混合掩蔽剂,虽然一般常见离子不干扰,但钼离子超过80微克严重干扰测定钨。为此提出用氨荒酸铵(TCA)掩蔽钼离子。试验表明,1毫升氨荒酸铵溶液(1+1)至少可掩蔽50微克钼(Ⅴ),而对钨(Ⅵ)不起掩蔽作用。5毫升混合     

不同提取方法所得褐藻糖胶的理化性质比较

通过各种理化性质的测定,对不同提取方法所得褐藻糖胶进行了分析,乙醇沉淀法的测定结果为:总糖含量(76.00±9.00)%、硫酸根含量(11.33±0.47)%、岩藻糖含量(35.60±4.20)%、重均/数均分子量(3.42×104)/(1.21×104);高分子电解质沉淀法的测定结果为:总糖含量(70.00±11.00)%、硫酸根含量(10.80±0.58)%、岩藻糖含量(35.15±2.85)%、重均/数均分子量(1.15×105)/(5.88×104)。高分子电解质沉淀法所得褐藻糖胶粗品和纯化后褐藻糖胶,其高分子电解质残留量分别为(0.12±0.038)%和(0.022±0.002)%。结果表明,乙醇沉淀法所得产品质量优于高分子电解质沉淀法,但是高分子电解质沉淀法具有工艺简单、成本低,更适于工业化生产等优点。     

电感耦合等离子体原子发射光谱法(ICP-AES)测定铜磁铁矿中铜、锰、铝、钙、镁、钛和磷的含量

通过样品处理、干扰实验、方法检出限、准确度和精密度实验,确定了最佳实验条件,建立了电感耦合等离子体-原子发射光谱法(ICP-AES)测定铜磁铁矿中铜、锰、铝、钙、镁、钛和磷含量的方法。试料经盐酸、硝酸、氢氟酸、高氯酸分解,用盐酸溶解盐类,过滤,采用电感耦合等离子体原子发射光谱法同时测定滤液中铜、锰、铝、钙、镁、钛和磷的含量。方法检出限为锰、钛和磷小于0.00085%,其它元素小于0.0054%,分析结果与分光光度法、X射线荧光光谱法(XRF)和原子吸收光谱法(AAS)分析结果一致,8个实验室对5个水平样品进行协同实验给出了方法的精密度。     

稀土萃取分离废水制备高纯碳酸氢镁溶液过程中铁杂质的行为与影响

以稀土冶炼分离过程中产生的氯化镁废水和白云石为原料制备氢氧化镁,然后采用碳化法制备高纯碳酸氢镁溶液,研究了铁杂质离子的行为与影响。结果表明:碳酸氢镁溶液中的杂质铁是由于二价固态铁发生碳化反应而引入并以重碳酸亚铁(Fe(HCO3)2)形式存在,即碳化反应过程是除铁的核心工序,Mg(HCO3)2溶液经过除铁后沉淀稀土离子可以明显降低沉淀产物中铁杂质含量。本文为氯化镁废水-白云石碳化法制备碳酸氢镁溶液过程中铁杂质离子的去除提供切实可行的理论指导。     

毛细管离子色谱法测定酒和饮料中阳离子

建立了毛细管离子色谱测定酒、饮料等样品中阳离子的分析方法。使用毛细管离子色谱柱IonPac CS12A(250 mm×0.4 mm, 8 μm),以甲基磺酸淋洗液发生器(EGC-MSA)产生18 mmol/L的甲基磺酸为流动相,进样量0.4 μL,在流速0.01 mL/min的条件下,采用自循环抑制电导检测的方法对啤酒、葡萄酒、白酒、果汁及奶茶等样品中的阳离子含量进行检测。结果表明,毛细管离子色谱法能满足阳离子含量的测定要求,系统稳定不易堵,在灵敏度方面优于常规离子色谱系统。该方法能够快速、准确地测定酒、饮料等样品中的5种阳离子(钠、铵、钾、镁和钙),回归方程的相关系数在0.9997以上,实际样品的加标回收率为95.2%～103.3%。该方法具有灵敏度高,操作简单,环境友好的特点。     

Simultaneous Determination of Total Nitrogen and Metal Elements in Tobaccos by High Performance Ion Chromatography

A simple method, developed primarily for simultaneous determination of total nitrogen and inorganic cations by high performance ion chromatographic (HPIC), was optimized for digestion of flue‐cured tobaccos, and compared with the traditional Kjeldahl method and atomic absorption spectrometry (AAS). Nitrogen determination by either Dumas method or Kjeldahl method is time‐consuming and tedious. Metal elements determination by either inductively coupled plasma‐mass spectrometry (ICP‐MS) or AAS may be more expensive and requires specialist equipment. The use of HPIC to simultaneous determine total nitrogen as ammonium ion and metal elements as inorganic cations after sample digestion significantly improves the speed of the analysis compared with the conventional methods. The cation‐exchange column and suppressed conductivity detector was used for determination of ammonium and inorganic cations in the presence of the elevated levels of sulfuric acid found in digested sample. The propsoed digestion method was accurate and precise, and required little investment. The determination of ammonium and inorganic cations was linear from 15 pg·L^?1 up to 25 ng·L^?1. The results obtained by the HPIC method were compared with those for the conventional methods approach for the determination of total nitrogen and metal elements. The application of the HPIC method is also demonstrated for a variety of other plant samples matrices.     

酸性氯酸钾处理-水浴加热全自动凯氏定氮仪测定土壤矿物中的固定态铵

固定态铵作为一种重要的潜在氮源,准确测定其含量,对于认识土壤肥力的形成机理、生态系统氮循环和保障国家粮食安全具有十分重要的意义。固定态铵最常用的方法是Silva-Bremner法,但该方法试剂配制要求严苛,前处理过程操作繁琐、费时。为了实现快速、准确、安全地测定土壤固定态铵的含量,对前处理过程进行了研究,用酸性氯酸钾溶液处理土壤样品,用水浴代替震荡,并与Silva-Bremner法的结果进行了对比。试验了自动凯氏定氮仪工作参数、酸性氯酸钾的浓度和用量、水浴加热的温度和时间,确定了测定土壤固定态铵的最佳条件。结果表明,称取1克样品加入20毫升氯酸钾-盐酸混合溶液（3％-10％）预处理,用0.5mol/L氯化钾溶液交换、洗涤,残渣加入加5mL氢氟酸-盐酸溶液（5mol/L-1mol/L）,在沸水浴加热1.5-2h,用自动凯氏定氮仪蒸馏滴定。对5种类型土壤固定态铵7次测定的结果进行了数据分析,相对标准偏差（RSD）均小于3.87%,最大G值1.49,最大F检验值4.12,最大t检验值0.72,均小于临界值,两种方法测定结果无显著差异。该方法的操作安全性和分析效率得到大幅提高,方法的精密度、准确度满足要求。     

High-performance ion chromatography assessment of inorganic and organic nitrogen fractions in potatoes

A new high-performance ion chromatography assay for organic and inorganic nitrogen analysis has been proposed and examined. In the devised protocol, inorganic sample constituents were measured after ultrasonically assisted water extraction. The amine and amide nitrogen content was assessed after modified Kjeldahl digestion and determined as NH₄⁺, and the total nitrogen content was quantified as NO₃⁻ after microwave-facilitated digestion. Finally, the nitro, azo, azoxy nitrogen was calculated by comparison of the total nitrogen content and all measured nitrogen species. The detection limits of the measured ions were 2.0, 0.82 and 0.17 mg L⁻¹ for nitrate, nitrite and ammonium, respectively. For samples of potatoes, the average shares of the nitrogen species found in the total nitrogen content were: 0.83% of nitrate nitrogen, <0.03% of nitrite nitrogen, 2.1% of ammonium nitrogen, 71% of nitro, azo, azoxy nitrogen, and 26% of amine, amide nitrogen. We expect the method to be applicable to different vegetable samples. The quality of the results obtained was verified by analyzing certified reference material and comparing to another analytical method.     

Rapid estimation of global sugars by UV photodegradation and UV spectrophotometry

The UV/UV method developed for the measurement of specific wastewater pollution parameters (ammonium, Kjeldahl nitrogen, total phosphorus) is adapted to the determination of sugars in fruit juices and soft drinks. The procedure is based on the UV spectrophotometric detection of by-products of UV photodegradation of carbohydrates. Time of analysis is greatly reduced by using specific pH conditions and diluted samples.     

Comparison of the Kjeldahl method and a combustion method for total nitrogen determination in animal feed

The features of the Dumas combustion method (CM) and those of the Kjeldahl method (KM) were compared as they apply to total nitrogen determination in animal feed. Both methods achieved similar repeatability (S.D., 0.11-0.38 from Kjeldahl and 0.15-0.36 from combustion) and similar intra-laboratory reproducibility (S.D., 0.11-0.39 from Kjeldahl and 0.15-0.37 from combustion). R.S.D. is always below 2%. These results show that the CM is suitable for the analysis of protein content in animal feed (5-75% protein content). The CM is recommended owing to its shorter analysis time, its cost and its environmental suitability.     

A microscale Kjeldahl nitrogen determination for environmental waters

A microscale Kjeldahl system has been designed which has been homemade reduced. The digestor unit of a macroKjeldahl system and a modified glassware microdistillation unit have been used. The optimal conditions for digestion and distillation have been established for ammonium and methylamine as model compound of organic amino nitrogen. The optimised procedure has been applied to the determination of Kjeldahl nitrogen in water samples. Recoveries near 100% and good precision have been achieved. This procedure combines nitrogen miniaturized system and the use of a selective ion electrode for ammonia detection. The analysis time was reduced 4.8 times and the analysis cost 6.6 times compared with classical procedure. The residues generated have been also markedly minimized. A preconcentration factor of 4 instead of 1.5 obtained by the macroscale design has been achieved.     

Analysis of beryllium carbide

An analysis scheme is presented for determining the composition of impure beryllium carbide. The determination of combined (carbide) carbon, which fixes the amount of Be2C present, is based on a catalytic oxidation of the methane formed by an acid hydrolysis of the carbide. The major impurities, beryllium oxide and free carbon, are readily determinable after separating the oxide by selective bromination of the carbide, and liberating the free carbon by a simple acid digestion. Analysis for fixed nitrogen is made by the Kjeldahl method and total moisture, which includes both adsorbed water and water of hydration, is obtained by drying samples in an inert gas stream at 700° C. An improved dibasic ammonium phosphate precipitation is used for determining beryllium.     

Removal of aqueous ammonium with magnesium phosphates obtained from the ammonium-elimination of magnesium ammonium phosphate

In order to recycle magnesium ammonium phosphate (MgNH4PO4.6H2O: MAP) obtained from MAP process, which is one of the attractive processes for removal of aqueous ammonium and phosphate from wastewater, ammonium elimination from MAP to magnesium phosphates and ammonium incorporation into the magnesium phosphates have been investigated in the present study. It is confirmed that magnesium hydrogen phosphate (MgHPO4) is favorably obtained from the ammonium elimination from MAP at temperatures greater than 353 K, although magnesium phosphate (Mg3(PO4)2) and magnesium pyrophosphate (Mg2P2O7) have been suggested as possible candidates. Based on the dissolution-precipitation mechanism for the removal of aqueous ammonium with magnesium phosphates, three magnesium phosphates were employed for the removal of aqueous ammonium. The order of the removal rate of the aqueous ammonium was MgHPO4>Mg3(PO4)2>Mg2P2O7, as expected from the solubility of those magnesium phosphates. The removability of the solid obtained from ammonium elimination of MAP is also confirmed. The present results show that MAP can be employed as an advanced material for the removal/recovery of ammonium, although it is generally accepted that an excess of MAP obtained from the wastewater treatment can be only used as a slow-acting fertilizer.     

Ultrafast capillary electrophoresis method for the simultaneous determination of ammonium and diphenhydramine in pharmaceutical samples

Ammonium and diphenhydramine are active ingredients commonly found in the same pharmaceutical preparations. We report, for the first time, a sub‐minute method for the simultaneous determination of ammonium and diphenhydramine. The method is based on capillary electrophoresis with capacitively coupled contactless conductivity detection. Both analytes can be quantified in a single run (∼80 injections/h) using 30 mmol/L 2‐(N‐morpholino)ethanesulfonic acid and 15 mmol/L lithium hydroxide (pH 6.0) as background electrolyte. The separation by capillary electrophoresis was achieved on a fused‐silica capillary (50 cm total length, 10 cm effective length, and 50 μm inside diameter). The limits of detection were 0.04 and 0.02 mmol/L for ammonium and diphenhydramine, respectively. The proposed method also provided adequate recovery values for spiked samples (100–106 and 97–104% for ammonium and diphenhydramine, respectively). The results obtained with the new capillary electrophoresis method were compared with those of the high‐performance liquid chromatography method for diphenhydramine and the Kjeldahl method for ammonium and no statistically significant differences were found (95% confidence level).