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41.
工业废水中微量铜(Ⅱ)和氰化物的流动注射光度分析 总被引:2,自引:0,他引:2
采用FIA技术,以光度比色法为基础,建立了工业废水中微量Cu^2+和CN^-的顺序自动分析方法和装置。其对二种离子的测定频率为60样/h,相对标准偏差<1.0%,工作曲线的r值≥0.999,各项分析技术指标均优于手工法操作。 相似文献
42.
Weil Joseph Brewer Mark Hendrickson Richard Sarikaya Ayda Ladisch Michael R. 《Applied biochemistry and biotechnology》1998,(1):99-111
Yellow poplar wood sawdust consists of 41% cellulose and 19% hemicellulose. The goal of pressure cooking this material in
water is to hydrate the more chemically resistive regions of cellulose in order to enhance enzymatic conversion to glucose.
Pretreatment can generate organic acids through acid-catalyzed degradation of monosaccharides formed because of acids released
from the biomass material or the inherent acidity of the water at temperatures above 160°C. The resulting acids will further
promote the acid-catalyzed degradation of monomers that cause both a reduction in the yield and the formation of fermentation
inhibitors such as hydroxymethyl furfural and furfural. A continuous pH-monitoring system was developed to help characterize
the trends in pH during pretreatment and to assist in the development of a base (2.0 M KOH) addition profile to help keep
the pH within a specified range in order to reduce any catalytic degradation and the formation of any monosac-charide degradation
products during pretreatment. The results of this work are discussed. 相似文献
43.
Linsinger TP Gawlik BM Trapmann S Lamberty A Emons H 《Analytical and bioanalytical chemistry》2004,378(5):1168-1174
Over the years, the nature of CRMs has changed considerably. Recently, more and more CRMs have been certified in their "natural" form, that is processed as little as possible, with analytes at their natural concentration level. This and the trend towards certified properties other than the concentrations of clearly defined molecules/elements have made guaranteeing stability of CRMs and estimating a shelf life an even more important issue for reference material producers than it has been before. One way to meet this challenge is to take more care in processing, storage and dispatch of CRMs. At IRMM, approximately 20 % of the RMs are stored at –20 °C or below and about 10% require cooled transportation. In addition, increased efforts for assessing stability are needed. Shelf lives are estimated using addition of an uncertainty component based on real-temperature stability studies rather than by accelerated stability studies. These pre-certification efforts are complemented by a stability-monitoring program, which at IRMM includes 80 % of the non-nuclear and non-isotopic materials. Although the costs for these efforts are high in absolute terms, they are only a minor and indispensable contribution to the total costs of CRM production. 相似文献
44.
Using column-switching liquid chromatography/tandem mass spectrometry (LC-MS/MS), we developed an improved analytical method of urinary estriol glucuronides. This new method is derived predominantly from maternal and fetal precursors in pregnancy. We used in the following procedure: first, we filtered urine samples with a membrane filter. Next, we directly injected the 50 microL aliquot of urine samples onto a pre-column. Then, after activating the column-switching valve, we backflushed the loaded samples onto the C(18) analytical column. Urine samples can be assayed within 20 min without any sample preparation steps. We monitored separated estriol glucuronides by negative electrospray ionization (ESI) and selected-reaction monitoring (SRM). The calibration range of estriol-3-glucuronide (E3-3G) and estriol-16-glucuronide (E3-16G) was 0.1-20 microg/mL and the linearity of the method was 0.9984 for E3-3G and 0.9987 for E3-16G. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 10 ng/mL (E3-3G) and 5 ng/mL (E3-16G). The analytical recovery was over 85% and, in general, inter-day and intra-day variability for precision and accuracy were less than 10%. When applied to a pregnancy urine sample to biomedical monitoring of the function of the maternal/fetal unit, the proposed method allowed rapid and sensitive screening for the detection of E3-3G and E3-16G. 相似文献
45.
神府烟煤以及贵阳贫煤分别与木屑掺烧灰沉积特性研究 《燃料化学学报》2003,48(9):1055-1062
利用CCD相机和沉积探针组成的在线监测系统,在50 kW下行炉上研究了木屑与神府烟煤以及贵阳贫煤的掺烧灰沉积特性。灰渣沉积过程可分为三个阶段:缓慢增长阶段、快速增长阶段和稳定阶段。烟煤掺烧灰沉积厚度随着木屑掺烧比例的增加而增加,贫煤掺烧灰沉积厚度则随着木屑掺烧比例增加而减小。烟煤中掺烧木屑比例为0、6.7%、15%和22%时,渣层稳定厚度分别为1.37、3.85、11.50、20.56 mm,稳定相对热流密度分别为0.44、0.41、0.30、0.26。贫煤掺烧木屑比例为6.7%、15%和22%时,稳定厚度分别为18.65、10.97和9.78 mm,稳定相对热流密度分别为0.29、0.31、0.33。掺烧木屑之后,灰渣初始层中Ca、K元素显著增加。在相同温度下,随着木屑掺烧比例的增加,灰中熔融相比例增加,因为木屑灰分中含有较多的Na2O、K2O等碱金属氧化物,而Al2O3、SiO2等含量较少,降低了灰的熔融温度。 相似文献
46.
The reaction of styrene oxide, a potential carcinogen in humans, with DNA constituents has been used to develop an improved method for quantification of DNA adducts. To enable monitoring of DNA adducts caused by xenobiotics at physiological relevant levels, a robust, reliable and powerful method based on monitoring of phosphorus in nucleotides is described. An efficient enzymatic digestion step and a sample-preconcentration procedure are essential, and enable separation of alkylated nucleotides from the large excess of native nucleotides. The adducts are detected by means of the phosphorus signal measured at mass m/z=31 with an inductively-coupled-plasma mass spectrometer. Bis(4-nitrophenyl)phosphate (BNPP) serves as internal standard for quantification of the adducts. The absolute limit of detection, 45 fmol, corresponds to detection of three modified nucleotides among 107 native nucleotides (the calculation is based on use of 50 g calf thymus DNA). An adduct formation ratio at the DNA of 3.6 adducts per 1000 nucleotides was measured, which is 75% lower than for reaction with monomeric 2-deoxy-nucleotides. In addition, a substantial amount of phosphate adducts were detected, but in DNA the rate of phosphate formation was lower than with monomeric nucleotides. Most probably these adducts escaped unnoticed when 31P-post-labelling was employed. 相似文献
47.
研究聚焦董事会内部沟通网络,基于独立董事信息共享机制探讨对高管薪酬的监督效果。研究发现,独立董事相互之间通过共享信息来增强对高管自利行为的抑制能力,有效降低了高管薪酬。同时,管理者权力对独立董事信息共享机制的监督效力起到调节作用,具体表现为随着管理者权力的增强,独立董事信息共享对于高管薪酬的约束作用被弱化,这一结果说明独立董事信息共享机制的监督有效性受到管理者权力的限制。研究构建了独立董事信息共享指标,并基于董事会监督博弈过程分析信息共享对高管自利行为的约束过程,最后运用A股上市公司数据加以验证。研究拓展了对独立董事监督机制的认识,为打开董事会“黑箱”、提升董事会绩效提供新视角,促进公司治理机制由静态结构研究向动态过程研究转化。 相似文献
48.
Traceability of the measurement of analytical parameters capable of evaluating the performance of methods is an important
concept for the assessment of quality for the routine control, especially for residue monitoring of non-authorized medicinal
substances in food from animal origin. The European Decision no. 657/2002/EC recommends to calculate two statistical limits,
CCα and CCβ, which allow to evaluate the critical concentrations above which the method reliably distinguish and quantify
a substance taking into account the variability of the method and the statistical risk to take a wrong decision. The calculation,
which can be derived from the ISO standard no. 11843 is applied on a routine basis. An example displays a very simple way
for evaluating the performance of an LC-MSMS method which has been validated a few years ago and is qualified onto a Micromass
Quattro LCZ tandem mass spectrometer to monitor and confirm the nitrofuran metabolite residues in food from animal origin.
Community Reference Laboratory for Antimicrobial Veterinary Drug Residue Control in Food from Animal Origin 相似文献
49.
气相色谱-负化学源质谱联用法测定菊酯类农药 总被引:1,自引:0,他引:1
通过固相萃取-气相色谱-负化学离子源质谱技术建立了11种拟除虫菊酯类农药残留的检测方法,并应用于茶叶农残检测。样品经乙酸乙酯提取后,用串联的活性炭和中性氧化铝固相萃取柱选择性地富集茶叶中待测组分,再由气相色谱-负化学离子源质谱分时段选择离子监测技术进行测定。方法简单快速,一次进样就能得到11种菊酯残留结果;准确度和精密度高,在0.016μg/kg、0.032μg/kg和0.064μg/kg3个添加水平下的回收率在70%~110%之间,CV≤7.4%;选择性好,消除了色素和其它杂质干扰;灵敏度高,检出限低,除了氯菊酯为10μg/kg外,其它菊酯检出限都在μg/∥kg级,七氟菊酯则达到了0.02μg/kg。 相似文献
50.
LING Daren LIU Bing WU Guoqi Department of Applied Chemistry Jiangsu Institute of Petrochemical Technology Changzhou China 《Chinese Journal of Reactive Polymers》2002,(1)
1. INTRODUCTION When investigating contaminated sites it is often essential to determine specific pollutants in a large number of ambient air samples. Amongst these sites, polycylic aromatic hydrocarbons (PAHs) are a major class of compounds that hav… 相似文献