恒温石墨炉中基体对钾和镉的影响

电热原子化原子吸收分析易受基体的干扰,使得准确度的提高受到限制.有关减少和消除这个影响已有报导^[1-6]。Czobik等^[6]人曾指出,为减少和消除基体的干扰,应设计一种具有时间和空间上等热条件的石墨炉。恒温石墨炉有上述的性质,用它作原子化器能消除和减少基体的影响。     

恒温炉中加热管材料对灵敏度的影响

恒温炉中加热管石墨表面结构和物理性质,直接影响分析试样的原子化行为。目前,利用热解涂层石墨管改善原子吸收分析灵敏度,已被人们重视并广泛应用^[1-2]。本文采用Woodriff炉做原子化器,对Al、K、Ag、Cd在普通石墨管和玻璃碳管中的原子化行为进行了研究,结果四种元素在玻璃碳管中的灵敏度均获得提高。     

炸药爆轰合成纳米石墨的红外光谱研究

石墨是碳材料中最常见的结晶状态,它具有耐高温、抗腐蚀、自润滑、无毒及价格低廉等特点,广泛应用于润滑剂和添加剂等方面^[1].由于高纯纳米石墨粉在某些高新技术领域中有较好的应用前景,近些年来得到开发和应用,如制成复合导电材料、吸波材料及储氢材料等^[2].以前有学者用纳米金刚石粉加热相转变^[3]和高能球磨^[4,5]的方法制备了纳米石墨,在制备碳纳米管时也有石墨的纳米粒子生成^[6].但用这几种方法制备纳米石墨,既费时又消耗较大能量,成本非常高.     

微波消解-微波等离子体炬原子发射光谱法测定无铅汽油中痕量铅的研究

四乙基铅作为一种良好的抗爆添加剂,曾广泛用于汽油生产中,但由于四乙基铅有很强的毒性,目前国际上已停止生产和使用车用含铅汽油,因此在生产车用无铅汽油时严格控制和准确测定铅的含量十分必要.迄今,测定汽油中铅含量的常用方法是铬酸盐容量法^[1]、一氯化碘法^[2]、X射线光谱法^[3]、分光光度法^[4,5]、原子吸收光谱法^[6]和等离子体光谱法^[7].这些方法或操作烦琐,测定时间较长^[4],或灵敏度低^[1～3],或测定误差较大,且在测试中需使用毒性较大的四乙基铅^[5],或所需的氯化甲基三辛基铵不易购买^[6],或处理过程繁琐,且仪器设备昂贵^[7].因此,建立一种简便、快速、灵敏、准确和无毒副作用的测定无铅汽油中痕量铅的方法已显得十分迫切.近年来发展的微波等离子体炬原子发射光谱法^[8]已有商品化仪器问世^[9].本文利用微波等离子体炬原子发射光谱仪研究了无铅汽油中痕量铅的测定方法,并提出用微波消解法预处理无铅汽油样品,将微波消解技术与微波等离子体炬原子发射光谱法相结合,建立了简便、快速、灵敏、准确和无污染的测定无铅汽油中痕量铅的新方法.     

电极防吸附膜研究

在电化学分析及电极过程动力学研究中,表面活性物质在电极上的吸附,常使测量结果受到严重影响^[1,2]。在天然水的反向极谱分析中,由于天然水,特别是海水,含有大量表面活性物质及悬浮体,并且分析溶液又进行搅拌,因此对电极的灵敏度及重演性影响特别严重^[3-5]。用汞膜电极测定一个新采集的海水样品后,即需重新涂汞^[3,4]。     

石墨炉原子吸收光谱中尿的背景吸收研究

本文较详细地研究了尿背景吸收的来源, 特点和消除方法, 背景吸收波长特性和在石墨管内蒸发行为的研究表明, 尿的背景吸收主要来自氯化钠, 其次是氯化铵, 其他组份的贡献很小, 时间特性研究表明, 背景吸收大小和背景吸收曲线轮廓与原子化阶段的加热方式和原子化温度有关。还研究了应用基体改进剂和其他减小背景吸收的方法。     

气相色谱法测定痕量氟方法的研究

气相色谱法测定有机硅化合物中的痕量氟是60年代末发展起来的,1967年Bock和Semmer^[1]用三乙基氯硅烷等有机硅化合物萃取,用半饱和NaHCO₃反萃测定氟,并建议可用GC法直接测定三乙基氟硅烷,1968年Fressen等^[2]用气相色谱法测定氟,近20年来,气相色谱法测定氟在环境监测、卫生防疫等方面得到应用^[3,4]。     

开系下的极限环线

B-Z反应较早是用分光光度计观察颜色的周期性变化^[1]。Field采用电动势测定E～t或C～t图^[2]。最近大量工作证明上述二种方法仍然是很重要的。B-Z反应是属于非平衡态中存在自组织现象的一个实例,三分子模型^[3]和低浓度三分子模型^[4]至今尚未找到实例,因而Oregonator成了颇为重要的一个实际模型^[5]。原则上直接测到相平面上lg[Br^-]与lg[Ce⁴⁺]的变化。给验证理论提供了一种可靠性。     

离子选择电极电位滴定法有机化合物中硼的快速微量分析

有机硼化合物在分解后通常转化为硼酸,需以甘露糖醇使其形成络合物,再用标准氢氧化钠溶液滴定^[1]。氧瓶分解法分解有机硼化合物,常需在样品燃烧前于样品内加入蔗糖^[2]、氢氧化钾^[3]或EDTA二钠盐^[4]。Gadson等^[5]在含硼无机溶液中加入少量10％氢氟酸,10分钟内形成BF₄^-,然后用流动载体氟硼酸根离子选择电极直接电位法进行测定。由此,我国刘成梁等^[4]首次提出氟硼酸根离子选择电极标准添加法,应用于有机硼元素微量分析。     

硝基磺酚C光度法测定蛋白质的研究

蛋白质的定量分析是生化研究、临床化验和食品检验等领域经常涉及的内容.以有机小分子作光谱探针测定蛋白质,如甲基橙^[1,2]、考马斯亮蓝G-250^[3]、溴酚蓝^[4]、溴甲酚绿^[5]和偶氮胂Ⅲ^[6]等已得到研究.     

镥、镱基体在石墨炉原子吸收光谱中的背景吸收研究

利用镥、镱基体在石墨炉中的蒸发行为研究了背景吸收的来源 ,讨论利用基体改进剂减少氯化物背景吸收的方法 ,为镥、镱基体中超痕量元素的精确测定提供帮助。     

石墨炉原子吸收光谱中GdCl3,Gd（NO3）3基体的背景吸收

研究了石墨炉原子吸收光谱中ＧｄＣｌ３、Ｇｄ（ＮＯ３）３基体的背影吸收影响。背景吸收波长特性的研究表明，ＧｄＣｌ３和Ｇｄ（ＮＯ３）３的背景吸收都具有明显的波长特性。蒸发行为研究表明ＧｄＣｌ３的背景吸收主要来自ＧｄＣｌ３的分子蒸气，Ｇｄ（ＮＯ３）３的背景吸收主要来自ＮＯ。钆基体的背景吸收峰高与灰化有关，ＧｄＣｌ３背上曲线轮廓与原子化温度和原子化方式有关。Ｇｄ（ＮＯ３）３的背景吸收远小于ＧｄＣｌ３。本文     

Comparative Study of the Effect of Sample Matrix on the Atomic Absorption of High-Volatile Elements in Two-Step and Conventional Atomizers

The space–time dynamics of absorbing atomic layers of cadmium and lead and molecular layers of zinc chloride in a commercially produced transverse-heated graphite atomizer and a newly developed two-step atomizer was studied. It was shown that the limiting temperature of cadmium pyrolysis in the two-step atomizer without the use of modifiers may be as high as 1000°C, whereas in the commercial analyzer is it not higher than 300°C. Levels of nonselective absorption due to sodium chloride were compared. It was found that, for a two-step atomizer, the maximum allowable mass of sodium chloride for which the background at lead and cadmium lines can be adequately compensated is 17–30 times higher than that for the commercial atomizer. The atomization of cadmium in the presence of sodium chloride was studied using time, space, and spectral resolution. It was shown that the effect of the chloride matrix in the two-step atomizer is suppressed because of sample fractionation and distillation in the course of its evaporation and condensation.     

Effect of atomizer surface type on the quantitation of molybdenum and ytterbium by electrothermal atomization atomic absorption spectrometry

The effect of pyrocoated graphite, uncoated graphite, metal-carbide, and metal atomization surfaces on the quantitation of molybdenum and ytterbium by electrothermal atomization atomic absorption spectrometry was investigated. The peak shape was affected by heating rate and the different surfaces gave different shapes. Except for the case of uncoated graphite, the sensitivities and detection limits were similar for all surfaces. In a sodium chloride matrix it is preferable to use uncoated graphite for molybdenum because an ashing stage greater than the boiling point of sodium chloride can be used without loss of molybdenum. Tube lifetime depended on atomization temperature, atomization time and the matrix.     

Determination of iron in seawater by electrothermal atomic absorption spectrometry and atomic fluorescence spectrometry: A comparative study

Two methods available for direct determination of total Fe in seawater at low concentration level have been examined: electrothermal atomization atomic absorption spectrometry (ETAAS) and electrothermal atomization laser excited atomic fluorescence spectrometry (ETA-LEAFS). In a first part, we have optimized experimental conditions of ETAAS (electrothermal program, matrix chemical modification) for the determination of Fe in seawater by minimizing the chemical interference effects and the magnitude of the simultaneous background absorption signal. By using the best experimental conditions, a detection limit of 80 ng L⁻¹ (20 μL, 3σ) for total Fe concentration was obtained by ETAAS. Using similar experimental conditions (electrothermal program, chemical modification), we have optimized experimental conditions for the determination of Fe by LEAFS. The selected experimental conditions for ETA-LEAFS: excitation wavelength (296.69 nm), noise attenuation and adequate background correction led to a detection limit (3σ) of 3 ng L⁻¹ (i.e. 54 pM) for total Fe concentration with the use a 20 μL seawater sample. For the two methods, concentration values obtained for the analysis of Fe in a NASS-5 (0.2 μg L⁻¹) seawater sample were in good agreement with the certified values.     

平衡时溶液的表面吸附

溶液的表面吸附仍是表面热力学当中的一个具有挑战性的问题.在本文中我们定义了一个新的热力学态函数,表面吸附的平衡条件是这个态函数的微分为零.基于这个条件,我们推导了描述平衡时表面吸附的新方程.在推导过程中没有采用假想分界面.新的表面吸附方程和Gibbs表面吸附方程完全不一样.还通过分子动力学方法模拟了氯化钠溶液,模拟结果和我们的理论预测符合较好.     

Improvement of direct determination of Cu and Mn in seawater by GFAAS and total elimination of the saline matrix with the use of hydrofluoric acid

Hydrofluoric acid, added to seawater, can assist in the removal of chloride in the drying step by precipitating fluoride salts, thus suppressing the chloride interference effects induced on the atomization signals of Cu and Mn. By adding HF to seawater before the analysis, MgF₂ and CaF₂ are precipitated at the bottom of the sampling flask, without precipitating Cu and Mn, and are consequently not introduced into the graphite furnace. Because sodium salts are eliminated at the pretreatment step, the whole seawater matrix is eliminated before the atomization of Cu or Mn. Therefore, the analyzed volume of seawater can be increased by using the multi-injection procedure without degradation of the limit of detection and risks of spectral interferences. The limit of detection obtained for Cu and Mn are 0.05 and 0.01 μg L⁻¹, respectively, for a 50 μL analyzed seawater volume.