Fully imidized soluble polyimides based on a novel dianhydride: 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride

We have synthesized a novel dianhydride, 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride (DCBTDA). Polyimides were synthesized with DCBTDA or 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and several relatively rigid meta- and para- substituted mononuclear diamines. The BTDA based systems were insoluble in dipolar, aprotic solvents whereas the DCBTDA based polymers displayed enhanced solubility in these solvents. The thermal stability of these polyimides was excellent as measured by 5% weight loss decomposition. The T_g's of the polymers were all above 290°C.     

迎头色谱程序升温脱附快速测定吸附热新方法

在Ｐｏｌａｎｙｉ吸附势理论基础上，结合程序升温脱附曲线的测定，建立了一个快速测定吸附热的新方法，详细讨论了该方法的原理，通过微机采样和数据处理，测定一条吸附热与覆盖度的曲线仅需１ｈ左右。     

Simultaneous determination of tetrahydro-β-carbolines and β-carbolines

Summary Reversed-phase ion-pair HPLC with fluorimetric detectors connected in series was studied for the simultaneous determination of two tetrahydro--carbolines and two -carbolines. After additon of internal standards the samples were reacted with fluorescamine, and then subjected to serial extractions to remove their precursor (tryptamine) from the analytical system. This treatment not only suppressed the artefactual formation of tetrahydro--carbolines and -carbolines during analysis, but also effectively purified them. Under optimum conditions, using trifluoroacetic acid as counter ion, all analytes were separated within 14 min and without major interfering peaks. The quantitative ranges were 0.25–80.0 ng mL^–1 for both tetrahydro--carbolines and 0.1–30.0 ng mL^–1 for both -carbolines. Replicate spiking experiments showed that recovery from most of the samples tested was over 90% and the relative standard deviation ranged from 0.7 to 10.4% within and between assays. The proposed method was applicable to various materials such as soy sauce, vinegar, ketchup, tabasco, beer, wine, sake, whisky, brandy, cows' milk, coffee, cocoa, cheese, cigarette smoke and urine.     

高效液相色谱检测反－2－苯基－邻－硝基肉桂酸

初探了反－２－苯基－邻－硝基肉桂酸（ＰＮＣＡ）的高效液相色谱分离，优选出了最佳分离条件。所建立的方法简单、快速，适用于工业生产中的控制及分析。     

Comparison of combustion sources for sulfur chemiluminescence detection

Three different types of SCD combustion source have been evaluated for use in the chromatographic analysis of atmospheric sulfur compounds. The conventional FID source and the newer inverted burner source were found to be less sensitive and less stable than the flameless design. Overall, the flameless source was superior for use with HRGC-SCD.     

Use of headspace capillary GC to study the development of volatile compounds in fresh fruit

The composition of volatile compounds produced by fruit during growth and post-harvest storage and ripening has been studied and the different headspace methods compared. Static and dynamic headspace sampling have been compared and evaluated according to their capacity to collect and concentrate volatiles from the atmosphere surrounding the fruits, and FID, MSD, and organoleptic detection have been compared. The results emphasize that the headspace sampling procedure selected is crucial to the performance of subsequent analysis.     

Gas chromatographic conditions for the linearity of the relationship between σT,t and tR in open tubes

The linearity of the relationship between σ_T,t² and (1 + k)² is studied with the view of using it for the evaluation of GC equipment. Based on appropriate analytical expressions it is concluded that in general this relationship is not linear and that practical procedures for column evaluation should be developed that take this non-linearity into account.     

杉木针叶磷脂酰甘油脂肪酸组成分析

用改进的DEAE阴离子交换柱色谱法和硅胶薄层色谱法分离制备杉木针叶磷脂酸甘油，用气相色谱法测定了它的脂肪酸组成。分析结果表明，抗寒性强的杉木品种的针叶磷脂酰甘油脂肪酸的（18:1＋18:2＋18:3）／[16:0＋16:1（3t）]比值比不抗寒品种的高。     

Determination of acidic chlorinated pesticides in water: Comparison of official EPA method 515.1 and liquid-solid extraction HPLC/UV and HPLC/PBMS analyses

Summary A comparison of the official EPA method 515.1 for determination of chlorinated acidic pesticides and a modification of it is illustrated. Extraction of the analytes from water and their determination and quantitation is by gas chromatography-electron capture detection (GC-ECD), liquid chromatography-UV detection and liquid chromatography-particle beam mass spectrometry. Although HPLC-PBMS was found to be less sensitive than the GC-ECD method, it was, nevertheless, more sensitive than HPLC-UV. The modified method is simpler, quicker and allows more accurate determination of pesticides in aqueous samples.Deceased July 31, 1996     

The physical meaning of the corrected retention volume

Summary The true meanings of the so-called corrected retention volume and the specific retention volume are explained in the light of the recent paper by Davankov.