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991.
992.
Analytical techniques for the determination of polychorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and dioxin-like PCBs (DLPCB) are reviewed. The focus of the review is
on recent advances in methodology and analytical procedures. The paper also reviews toxicology, the development of toxic equivalent
factors (TEF) and the determination of toxic equivalent quantity (TEQ) values. Sources, occurrence and temporal trends of
PCDD/PCDF are summarized to provide examples of levels and concentration ranges for the methods and techniques reviewed. 相似文献
993.
制革废水中总铬的萃取光度法测定 总被引:5,自引:0,他引:5
研究了在含氯离子的酸性溶液中,用醋酸戊酯萃取二甲基吲哚二羰花青(DIDC)染料与Cr(Ⅵ)配合物,基于此,建立了一种测定Cr(Ⅵ)的新的光度法。结果表明在3 5mol/L~5 0mol/L的HCl介质中,醋酸戊酯对配合物的萃取率最高;最大吸收波长为640nm;摩尔吸光系数为3 6×105L·mol-1·cm-1,检出限为2 0×10-3mg/L,有色溶液的吸光度与Cr(Ⅵ)量在0 01mg/L~2 1mg/L范围内符合比尔定律,加标回收率为96 8%~104 5%(n=6),Cr(Ⅵ)∶Cl-∶DIDC的摩尔比为1∶1∶1。本法测定了制革废水中的总铬含量。 相似文献
994.
995.
利用沉淀分离、氧化 -还原、萃取和分光光度法测定 KIO3 - KI- KBr O3 - KBr混合体系中各组分含量。实验设计方案对实验综合设计以及复杂体系中各组分测定具有参考价值。 相似文献
996.
有机抽提对泥炭中的木栓质体荧光光谱特性的影响 总被引:2,自引:1,他引:2
钟建华 《光谱学与光谱分析》1997,17(3):119-122
对泥炭中的木栓质体及泥炭有机抽提残渣中的木栓质进行了荧光(光谱)对比研究,研究发现有机抽提对泥炭中的木栓质体的荧光(光谱)性影响很大,有机抽提前泥炭中的木栓质体发鲜艳的黄绿至绿色荧光:λmax=470~520nm;Q650/500=0.10~0.54。有机抽提后泥炭中的木栓质体则发暗黄色橙黄色荧光:λmax=605~660nm,Q650/500=1.85~4.09,有机抽提使木栓质体的荧光强度(I 相似文献
997.
Extraction and derivatization in single drop (EDSD) coupled to matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) was utilized to determine small molecular aldehydes (SMAs) in single puff smoke. A methanol solution of diphenylamine, 2,5-dihydroxybenzoic acid was used for extraction/derivatization of SMAs and a microdrop of the extraction solution containing the ionic derivatization products of SMAs could be directly deposited in the MALDI target to perform the measurement of SMAs in the cigarette smoke on puff level by MALDI-FTICR-MS. As a result, a consecutive operation of sample pre-treating and MALDI sample plate preparation was achieved. SMAs were derivatized by the reaction with diphenylamine and transformed a stable Schiff base bearing a quaternary ammonium group, and the sensitivity of analysis for SMAs was significantly improved. Good sample homogeneity in in-dot was achieved by adding diphenylamine into the solvent for EDSD and a satisfying repeatability (R.S.D. = 7.3% for formaldehyde, n = 5) of MALDI-FTICR-MS signals was obtained. This solvent- and reagent-minimized approach with an automatic potential provided a simple, rapid, and accurate procedure for the determination of SMAs in smoke. 相似文献
998.
用于小型显示器的背光源 总被引:1,自引:0,他引:1
背光源制造商们用更高的功效、更好的均匀性和更低的成本,来响应当今小尺寸显示器OEM的要求,所有这些都需要先进的光学技术。 相似文献
999.
1000.
Past research regarding singing ability has provided evidence that both supports and refutes a relationship between pitch discrimination ability and pitch production ability. Researchers have suggested that these skills improve with age. Despite this suggestion, most investigators studying singing ability have included only children as participants. Additionally, although many researchers have studied accurate singers, few have directly studied persons who do not sing accurately. We designed this study to examine the relationship between pitch discrimination ability and pitch production ability in inaccurate adult singers. Fifteen adults, aged 18 to 40 years, that met specific criteria qualified as inaccurate singers. Each participated in two tasks, a pitch discrimination task and a pitch production task. We used the Multi-Dimensional Voice Profile-Advanced (Kay Elemetrics Corporation, Lincoln Park, NJ) to determine the frequency of each participant's vocal productions during the pitch production task. We also used a Pearson product moment correlation to analyze the relationship between pitch discrimination and pitch production accuracy within a semitone of the target frequency. No meaningful relationship was found, and results were not statistically significant. However, the inaccurate singers in this study could be classified into two separate categories, those who discriminated pitches accurately, but produced pitches inaccurately, and those who discriminated pitches inaccurately and produced pitches inaccurately. These findings may be of great importance to music educators and impact the focus of instruction when teaching an inaccurate singer to sing more accurately. 相似文献