石英砂中SiO_2、Fe_2O_3的测定

1 烧失量的测定 1.1 测定原理 石英砂、硅砂主要成分为二氧化硅,常含有铁、铝、钾、钠、钙、镁等杂质。 试样中常含有有机物、易挥发杂质或少量碳酸盐、硫化物、化合水、高温灼烧即挥发逸出,灼烧所损失的重量,即为烧失量。 1.2 测定过程 准确称取试样约1克,放入已灼烧至恒重的铂金坩埚中(试样应在110℃烘干2小时,除去水份)。将铂金坩埚置于950—1000℃的高温灼烧1小时,冷却、干燥、称量。反复灼烧至恒重。     

新型树脂P(3,4HB)灰份的测定

在不同灼烧温度和灼烧时间下,测定粉末状P(3,4HB)树脂的灰份含量,综合分析试验结果,得出测定P(3,4HB)树脂灰份时采用的最佳条件为600℃灼烧0.5h。在同一温度下连续多次灼烧空坩埚,并置于硅胶干燥器冷却相同时间后称量其质量,然后采用数理统计分析方法,求出空坩埚灼烧冷却后的称量误差为±0.0010g,因此可确定灰份测定时和坩埚的恒重判断值为0.002g。     

Nitroso-Rsalt分光光度法测定FKH-01汽油无液碱脱臭催化剂中的钴

以Co2 -Nitroso -Rsalt(亚硝基红盐 )为显色体系 ,用分光光度法测定FKH - 0 1汽油无液碱脱臭催化剂中的微量钴。考察了样品灼烧条件和测定条件。在 80 0℃将样品灼烧 1h以上 ,用HCl溶液溶解灼烧后的COO。在 5 30nm波长处的吸收系数ε =1.0 3× 10 2 L/(mol·cm) ,线性范围为 0～ 0 .0 5mg/mL。测定结果与Co2 - 5 -Br-PADAP分光光度法一致。t检验表明 ,两种方法所得结果无显著差异。本方法简便 ,灵敏度高 ,准确度好     

氯化铵分析中的异常现象的探讨及排除

根据标准GB2946—92和ZBG21008—90，针对氯化铵分析中的异常现象，分析了工业氯化铵中灼烧残渣和农业氯化铵中钠盐含量测定结果异常偏低的原因，并排除了异常现象的干扰，讨论了灼烧温度和时间对测定结果的影响，指出了分析中正确控制样品的灼烧温度和时间的重要性，总结了氯化铵分析中应注意的问题。     

重铬酸钾容量法测定盐碱土中有机碳

建立了重铬酸钾滴定法测定盐碱土试样中有机碳的方法。通过加入0.1g Ag₂SO₄消除试样中少量Cl^-的干扰，在试样中Cl^-含量大于2.0×10⁴mg·kg^-1时，可采用灼烧差减法消除其干扰。实验表明，选择恒温电热板，以0.4mol·L^-1重铬酸钾-硫酸消解试样，利用邻菲啰啉作突变指示剂提高测定结果的准确性；采用高温灼烧后的SiO₂作为空白有效降低了方法的检出限。方法检出限为0.063%、定量限为0.21%。测定不同性质的国家一级标准物质(土壤、水系沉积物)中有机碳，结果与认定值的相对误差RE为-3.15%～1.15%，对数差△lg C为-0.073%～0.0292%，相对标准偏差RSD(n=12)为0.8%～4.41%。本方法操作简单、快捷经济、准确，检出限低、测定范围广，能够满足地球化学调查项目大通量样品的检测需求。     

Nd2BaCuO5超微粒子的制备与表征

以Nd2O3、Ba(NO3)2和CuO为原料，采用微乳液法合成了Nd2BaCuO5超微粒子。用X射线衍射仪(XRD)、扫描电镜(SEM)、BET法及直流电阻电桥对粉体进行了表征。结果表明，制备的超微粒子为钙钛矿型晶体。粉体经600℃灼烧后，其平均粒径为14．9nm；粉体经700℃灼烧后，其平均粒径为46．6nm。粉体经700℃灼烧后，在700℃时其电导率比常温时提高4个数量级。     

CaCO_3/PVC体系灰分含量测定方法的改进

采用二步法灼烧CaCO3/PVC体系,对其灰分的组成和灼烧过程中发生的反应进行了研究,并与一步法灼烧进行了对比。结果表明:①二步法灼烧过程中,CaCO3与HCl发生了复分解反应,且CaCO3的分解温度会降低,灰分含量的测量结果离散度较大;②采用一步法灼烧CaCO3/PVC体系,得到的灰分含量离散度较小,且与CaCO3含量呈一次函数关系,比二步法灼烧更合理,更具实用性。     

微波炉加热技术在鲜钙硫酸根含量测定中的应用

在普通过磷酸钙生产中间控制分析中,鲜钙中硫酸根含量的测定普遍采用硫酸钡烘箱干燥重量法或硫酸钡灼烧重量法,操作过程繁琐,用时长。笔者在实际操作中,采用微波炉加热干燥硫酸钡沉淀,测定值与灼烧重量法的测定值的绝对差值<0.17％。该方法的相对标准偏差(RSD)<0.3％,精密度和准确度良好,适合于生产中间控制分析。     

石英砂中二氧化硅含量测定的方法改进

石英砂是玻璃厂主要的原材料，其主要成分SiO2的测定采用HF-H2SO4处理，使硅逸去，杂质成分在800℃灼烧称重，差减法计算SiO2的含量。和氟硅酸钾法比较，发现该方法测定结果偏低。经过实验，我们利用HF-HNO^-3HClO3体系处理样品，使测定结果达到检测要求。     

羧甲基纤维素钠中代替度氯化物连续测定法

<正> 目前,生产厂家在测定羧甲基纤维素钠(简称CMC钠盐)产品中的代替度和氯化物含量时,是分别进行的。即先将试样用90％的酒精洗涤除去氯化钠后,经碳化灼烧,再用酸碱滴定法测定灼烧残渣中氧化钠来计算代替度;而氯化物的测定则另行称样进行。不但操作繁杂,且由于用AgNO_3溶液滴定氯化物是在粘性较大的溶液中进行的,终点的判断困难,常影响测定结果。鉴于以上情况,笔者经大量实验,提出了CMC钠盐中代替度和氯化物的连续测定法。通过50批生产试样的实际对比测定表明,连续测定法与原法相比,绝对偏差代替度为0.02,氯化物为0.20％,测定时间缩短2小时,并可节约大量乙醇等。     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

ICP-MS法测定地球化学样品中As、Cr、Ge、V等18种微量痕量元素的研究

建立了测定地球化学样品中包括As、Cr、Ge、V等18种微量、痕量元素的ICP-MS方法。地化试样用HF-HNO3混酸分解后,以1 1 HNO3溶解干渣。由于制样不使用盐酸,避免了Cl对As、Cr、Ge、V的质谱干扰。用国家一级地球化学标准物质GBW 07309制备溶液优化仪器工作参数,并用于校准。方法测定限(6s)为:0.007~6.4μg/g,精密度(RSD%,n=12)为:29%~9.4%,经过国家一级地球化学标准物质的分析验证,结果与标准值吻合。方法已应用于国土资源调查的试样分析。