二次标准加入法校正低氟样品测定偏差的试验研究

当待测液中氟离子浓度较低时氟离子选择电极的电位响应与浓度变化呈非线性关系,造成测定结果发生偏离,从而影响氟离子浓度测定的准确性。为探究氟离子选择电极测定低氟样品时的测定下限和影响情况,以不同性能的离子选择电极和不同浓度梯度待测溶液为研究对象,考察电极电位响应与待测溶液浓度的关系,评估其对测定结果准确度的影响,并提出采用二次标准加入法校正低浓度氟溶液测定偏差。结果表明:电极的能斯特响应临界浓度与其自身性能有关,长时间使用或放置会使临界浓度增大;当待测液浓度低于临界浓度时,采用一次标准加入法测定的氟含量值显著高于理论值,相对误差为28%~364%;使用二次标准加入法,可将干扰较少的待测液定量下限减小至0.02μg/mL,可将基体待测液定量下限减小至0.10μg/mL,测定相对偏差小于10%。

三维CAD技术在基桩偏差测定中的应用

通过对常规测量和三维CAD测量两种方法的详细阐述,结合它们在漳州海事局海事工作船码头工程基桩偏差测定中的实际运用,得出三维CAD测量方法优于常规测量方法的结论,最后提出应用建议。

三维CAD技术在基桩偏差测定中的应用

高桩码头沉桩完毕后的偏差测定,是设计复核和工程质量等级核定的必要依据。通过对常规测量和结合三维CAD测量2种方法的详细阐述,结合具体工程的实际运用,得出结合三维CAD的测量方法优于常规测量方法的结论,并提出应用建议。

石灰稳定土灰剂量测定结果偏差的因素分析

石灰剂量是石灰稳定土重要的施工技术参数之一,在施工过程中需要根据不同的测试时间准确、科学地测定该参数。经过长期检测研究发现,影响石灰稳定土灰剂量测定的因素较多,其中一些具有重要影响的因素在测试过程中容易被忽视,该文对相应的研究进行了阐述,对相关的影响因素进行了量化分析。

瓶胚垂直轴偏差测定仪校准方法的探讨

瓶胚垂直轴偏差测定仪是一种检测瓶胚垂直度偏差的常用仪器,应用范围广泛。针对国内目前尚无瓶胚垂直轴偏差测定仪校准方法的情况,本文对其校准方法进行了探讨,给出了详细的校准步骤。

液液萃取-GC-MS法测定水中硝基苯质量控制指标研究

采用液液萃取–气相色谱–质谱法测定水中硝基苯,通过统计全国多家实验室的测定数据,对平行样测定结果相对偏差、空白加标回收率、样品加标回收率、空白加标回收率相对偏差及样品加标回收率相对偏差5个质控指标进行分析,得出质控指标评价标准。在概率P,γ均为0.90时,平行样测定结果允许最大相对偏差应控制在11.0%;当空白加标浓度为0.2～30μg/L时,回收率控制范围为59%～113%;当样品未检出、加标浓度在0.25～50μg/L时,样品加标回收率控制范围为56%～110%;空白加标、样品加标回收率最大相对偏差应分别控制在10.0%和11.1%。在概率P和γ均为0.95时,平行样测定结果允许最大相对偏差应控制在13.5%;当空白加标浓度为0.2～30μg/L时,回收率的控制范围为50%～122%;当样品未检出、加标浓度在0.25～50μg/L时,样品加标回收率控制范围为49%～117%;空白加标、样品加标回收率最大相对偏差应分别控制在12.6%和14.6%。

水泥凝结时间测值偏差的若干因素分析

水泥凝结是指水泥加水拌和后,随着时间的变化,浆体将失去流动性,可塑性,逐渐形成具有一定强度硬化体的过程,这种过程有两个重要的状态,即初凝和终凝,其所经历的时间则称为初凝时间和终凝时间,它们是水泥重要的品质指标或水泥应用中重要的技术参数,凝结时间过快。

工业化进程中的结构偏差对城市化的影响

以钱-赛世界标准模式与中国195 2 - 2 0 0 0年城市人口比重与产业结构变迁实证为例可以了解到,中国工业化与城市化偏差的问题在于工业化结构偏差;产值结构与就业结构、消费结构偏差,即服务业发展滞后与城乡二元工业结构造成了工业化的进程未能有效带动就业结构与消费结构的变动,从而未能带动城市化的进程。

地—井瞬变电磁关键技术问题研究

地—井瞬变电磁法在加拿大、澳大利亚等国的勘查实践中已取得了很好的效果,国内由于缺乏从仪器设备到资料处理解释的整套技术,使得该方法未能被广泛应用。为此,研制了地—井瞬变电磁仪器,同时系统地研究了地—井三分量坐标系的确定、探头角度系统偏差的测定、三分量的校正运算、勘查目标体方位及距离的分析与计算等,并在实际的地—井瞬变电磁观测中获得了良好的应用效果。

Determination of Lignin in Marine Sediment Using Alkaline Cupric Oxide Oxidation-Solid Phase Extraction-on-Column Derivatization-Gas Chromatography

Lignin serves as one of the most important molecular fossils for tracing Terrestrial Organic Matters （TOMs） in marine environment. Extraction and derivatization of lignin oxidation products （LOPs） are crucial for accurate quantification of lignin in marine sediment. Here we report a modification of the conventional alkaline cupric oxide （CuO） oxidation method, the modification consisting in a solid phase extraction （SPE） and a novel on-column derivatization being employed for better efficiency and reproducibility. In spiking blanks, recoveries with SPE for the LOPs are between 77.84% and 99.57% with relative standard deviations （RSDs） ranging from 0.57% to 8.04% （n=3）, while those with traditional liquid-liquid extraction （LLE） are from 44.52% to 86.16% With RSDs being from 0.53% to 13.14% （n=3）. Moreover, the reproducibility is greatly improved with SPE, with less solvent consumption and shorter processing time. The average efficiency of on-column derivatization for LOPs is 100.8%±0.68%, which is significantly higher than those of in-vial or in-syringe derivatization, thus resulting in still less consumption of derivatizing reagents.Lignin in the surface sediments sampled from the south of Yangtze River estuary, China, was determined with the established method. Recoveries of 72.66% to 85.99% with standard deviation less than 0.01mg/10g dry weight are obtained except for p-hydroxybenzaldehyde. The lignin content ∑8 （produced from 10g dry sediment） in the research area is between 0.231 and 0.587mg. S/V and C/V ratios （1.028 ± 0.433 and 0.192±0.066, respectively） indicate that the TOMs in this region are originated from a mixture of woody and nonwoody angiosperm plants; the high values or （Ad/Al）v suggest that the TOMs has been highly degraded.

Gross Error Detection and Identification Based on Parameter Estimation for Dynamic Systems

The detection and identification of gross errors, especially measurement bias, plays a vital role in data reconciliation for nonlinear dynamic systems. Although parameter estimation method has been proved to be a pow-erful tool for bias identification, without a reliable and efficient bias detection strategy, the method is limited in ef-ficiency and cannot be applied widely. In this paper, a new bias detection strategy is constructed to detect the pres-ence of measurement bias and its occurrence time. With the help of this strategy, the number of parameters to be es-timated is greatly reduced, and sequential detections and iterations are also avoided. In addition, the number of de-cision variables of the optimization model is reduced, through which the influence of the parameters estimated is reduced. By incorporating the strategy into the parameter estimation model, a new methodology named IPEBD (Improved Parameter Estimation method with Bias Detection strategy) is constructed. Simulation studies on a con-tinuous stirred tank reactor (CSTR) and the Tennessee Eastman (TE) problem show that IPEBD is efficient for eliminating random errors, measurement biases and outliers contained in dynamic process data.

Effects of Grain Angle on Reproducibility and Accurate Measurement of Moisture Content of Wood Samples Using a Pin-Style Moisture Meter

Studies were conducted on the effects of grain angle on reproducibility and accurate measurement of moisture content of four wood samples using a pin-style moisture meter. The wood samples were partitioned into four quadrants and moisture contents were measured along the grain direction in the first and second quadrants from 0 degree to 150 degrees insteps of 30 degrees. Experimental results indicated that the average moisture content remained constant as the grain angle increased. Repeated measurements of moisture content at different grain angles or points on the wood surface showed similar patterns of variation. Within-point standard deviations of the moisture contents were greater than between-point standard deviations. A non-destructive method of measuring moisture content at the same location or point on the wood surfaces could not be proposed because of the high variation of moisture content when repeated measurements were taken at the same point. Instead, accurate measurements of moisture content could be obtained at random positions within a radius of 30 mm from the point of intersection of the moisture content axis and the grain angle.

On-line Separation and Preconcentration for Histamine Determination in Fish Meal Using Cation-Exchanger Resin

FI system was used for the determination of histamine. A mini-column filled with amberlite resin （weak cation exchanger） was introduced to the flow system. A 200 laL of the sample was injected into the carrier stream through the injection valve. The merged streams were passed through a quartz flow cell in a spectrophotometer connected to recorder. Under the optimum conditions, the calibration curve was linear in the range 0.02-1.5 μg mL^-1 of histamine using the peak height as an analytical signal, while the detection limit was 0.01 μg mL^-1. The precision and accuracy of the method were studied depending upon the values of the relative standard deviation and relative error percentage. The selectivity of the method was investigated by studying the effect of interference from other species accompanied with histamine in fish meal. Under the optimum conditions, the system was used for on line separation, preconcentration of histamine. The proposed method was applied for the determination of histamine in fish meal. The results were compared with the standard method and a good agreement between the results was obtained.

Determination of impurity elements in MnZn ferrites by inductively coupled plasma mass spectrometry

An inductively coupled plasma mass spectrometry(ICP-MS) method was developed for the determination of Na, Mg, Al,K, Ca, Ti, Cr, Co, Ni, Cu, Ga, As, Mo, Ag, Cd and Pb in MnZn ferrites. The sample was digested by HNO3+HCl with microwave digestion followed by dilution with ultrapure water, then the above 16 impurity elements in the solution were analyzed directly by ICP-MS. The impurity elements were introduced by the helium gas or hydrogen gas into the octopole reaction system(ORS) to eliminate the polyatomic interferences caused by the high salty matrixes. The matrix effect was minimized through matrix matching,and Be, Y and Rh were used as internal standard elements. The working parameters of the instrument were optimized. The results show that the method has good precision and high accuracy. The detection limits for the investigated elements are in the range of0.9-37.5 ng/L, the relative standard deviation of each element is within 1.1%-4.8%, and the recovery of each element is 90%-108%.

Effect of sample treatment on determination of arsenic （Ⅲ） and arsenic （Ⅴ） in aqueous and tissue samples by hydride generation atomic absorption spectrometry

The purpose of this procedure was to optimize and improve a method that used for the determination of arsenic （Ⅲ） and arsenic （Ⅴ） in biological and environmental samples. The method is based on hydride generation and atomic absorption spectrometry. For both As （Ⅲ） and As （Ⅴ） the parameters such as NaBH4, HCI concentration, and pH were optimized. Absorption signal of As （Ⅴ） was approximately 17% of As （Ⅲ） signal. Therefore, for estimation of As （Ⅲ） and As （Ⅴ） concentrations in various samples the difference between the absorbance obtained for arsenic, without and with previous treatment of samples with potassium iodide （KI）, can be applied. The calibration graphs were linear （r〉0.99）, and the detection limits of the method based on three times the standard deviation of the blank were 0.14 and 0.64 μL^-1 for As （Ⅲ） and As （Ⅴ）, respectively. The relative standard deviation （R.S.D.） of measurements was less than 10%. As a means of checking performance method, water samples were spiked with known concentrations of both As （Ⅲ） and As （Ⅴ）, and recovery above 94% was obtained. The proposed method was applied successfully to determine inorganic As （Ⅲ） and As （Ⅴ） in various environmental and total As in biological samples.

Assessment of Triazine Herbicides in Soil by Microwave-assisted Extraction Followed by Gas Chromatography Coupled to Mass Spectrometry Detection

An alternative and fast method for the analysis of a mixture of nine triazines herbicides in soil is presented. The method is based on MAE （microwave-assisted extraction） of herbicides using ethyl acetate as extractant. The economy in the use of solvents coupled with the decrease in extraction time and lower power consumption make MAE a technique that meets the principles of green chemistry. MAE operational parameters, extraction time, mass of the sample and extraction temperature, were optimized by RSM （response surface methodology）. Determination of analytes was completed using gas chromatograph coupled to mass spectrometry detection. The selected triazines could be efficiently extracted by the solvent at 80 ℃ for 10 min, with 80% output of maximum power. When the optimized method was applied to analysis samples, the recoveries of analytes ranged from 81.8 to 106.0% and relative standard deviations were lower than 8.41%. The method is stable and reasonable, which can be used for the determination of ninetriazine herbicides residues in soil.

Optimization of Sample Pretreatment for Determination of Polycyclic Aromatic Hydrocarbons in Estuarine Sediments by Gas Chromatography

This study examined levels of polycyclic aromatic hydrocarbons (PAHs) in estuarine sediments in Licun (Qingdao, China) by gas chromatography under optimized conditions for sample pretreatment via ultrasonic extraction, column chromatography, and thin layer chromatography. Methanol and dichloromethane (DCM)/methanol (2:1, v/v) were used in ultrasonic extraction, and DCM was used as eluate for column chromatography. The developing system consisted of n-hexane and DCM at a ratio of 9:1 (v/v), with DCM as the extraction solvent for PAHs-containing silica gel scraped off the plate. When the spiking level is 100 ng, total recoveries of spiked matrices for four target PAHs (phenanthrene, anthracene, pyrene and chrysene) were 83.7%, 76.4%, 85.8%, and 88.7%, respectively, with relative standard deviation (RSD) between 5.0% and 6.5% (n = 4). When the spiking level is 1000 ng, associated total recoveries were 78.6%, 72.7%, 82.7% and 85.3%, respectively, with RSD between 4.4% and 5.3% (n = 4). The opti-mized method was advantageous for determination of PAHs in complex matrix due to its effective sample purification.

The Precursory Meanings of the Deviation of the Magnitude-Frequency Distribution of Earthquakes from the Gutenberg-Richter Law

The Gutenberg-Richter law (G-R law) of the magnitude-frequency distribution of earthquakes has been an important base in seismology for a long time. However, the actual magnitude-frequency distribution usually deviates from the G-R law. Based on the experimental results of three different rock samples, which contain macro-asperity, compressional en-echelon fault and model-Ⅲ shear fault, the correlative coefficient (r) was calculated by fitting the sequences of the acoustic emissions with the G-R law in every scanning time window. We investigated the changes of the correlative coefficient, which describes the actual deviation of magnitude-frequency distribution of earthquakes from the G-R law within the specific scanning time window. According to the results of the rock samples containing macro-asperity and compressional en-echelon fault respectively, the value decreases prior to the rock fracture, meaning that the deviation of magnitude-frequency distribution from the G-R law tends to be larger. The result of the model-Ⅲ shear fault didn’t show obvious decrease before the final rock fracture. Actually, the studies of some earthquakes also show deviation before the occurrence of moderate earthquakes. The results obtained in this paper will provide us with some useful clues for studying precursors before the occurrence of moderate earthquakes with the data of regional earthquake activities.

Simultaneous determination mercury species of Su-He-Xiang-Wan in rat tissues by HPLC-CVG-AFS

A simple and sensitive high performance liquid chromatography-chemical vapour generation-atom fluorescent spectrometry （HPLC-CVG-AFS） method was developed and validated for simultaneous determination mercury species in Su-He-Xiang-Wan （SHXW） and in tissues of rats, respectively. The species of mercury were separated by a Venusil MP-C 18 （5μm, 150 mm×4.6 ram） column with the optimized mobile phase containing 5% （w/v） acetonitrile, 0.01 mol/L L-cysteine and 0.06 moL/L ammonium acetate. The tissues of rats were freeze-dried after giving the medicine for 10 d, and then added into the solution containing 10% （w/v） HC1, 1% （w/v） sulfocarbamide and 0.15% （w/v） KC1 for increasing extraction rate. The resolutions of Hg2＋, MeHg and EtHg were 1.5 and 2.9, respectively. The detection limits of Hg2＋, MeHg and EtHg were 2.0, 1.0 and 0.9 ng/mL, respectively. The relative standard deviation （RSD） of inter- and intra-day precisions ranged from 1.56% to 2.86%. The recovery rates of three different adding level were 87%-101% （n=6）, and the RSDs were smaller than 8.2%. The results show that no MeHg and EtHg were detected in rat tissues. Only soluble mercury （Hg2＋） was determined for the mercury species of SHXW in rat tissues.

Determination of Soil Parameters in Apple-Growing Regions by Near-and Mid-Infrared Spectroscopy

Soil quality monitoring is important in precision agriculture.This study aimed to examine the possibility of assessing the soil parameters in apple-growing regions using spectroscopic methods.A total of 111 soil samples were collected from 11 typical sites of apple orchards,and the croplands surrounding them.Near-infrared(NIR) and mid-infrared(MIR) spectra,combined with partial least square regression,were used to predict the soil parameters,including organic matter(OM) content,pH,and the contents of As,Cu,Zn,Pb,and Cr.Organic matter and pH were closely correlated with As and the heavy metals.The NIR model showed a high prediction accuracy for the determination of OM,pH,and As,with correlation coefficients(r) of 0.89,0.89,and 0.90,respectively.The predictions of these three parameters by MIR showed reduced accuracy,with r values of 0.77,0.84,and 0.92,respectively.The heavy metals could also be measured by spectroscopy due to their correlation with organic matter.Both NIR and MIR had high correlation coefficients for the determination of Cu,Zn,and Cr,with standard errors of prediction of 2.95,10.48,and 9.49 mg kg-1 for NIR and 3.69,5.84,and 6.94 mg kg-1 for MIR,respectively.Pb content behaved differently from the other parameters.Both NIR and MIR underestimated Pb content,with r values of 0.67 and 0.56 and standard errors of prediction of 3.46 and 2.99,respectively.Cu and Zn had a higher correlation with OM and pH and were better predicted than Pb and Cr.Thus,NIR spectra could accurately predict several soil parameters,metallic and nonmetallic,simultaneously,and were more feasible than MIR in analyzing soil parameters in the study area.