计算机模拟地质化验室分样及取样常数Ks的估算

提出了计算机模拟地质化验室取样过程,考察取样误差与取样量、样品粒度之间关系,并估算取样常数.实验所得的误差与取样量之间的关系与Ingamells的取样方程一致,取样常数及取样常数和样品粒度关系式也与Ingamells推导的相符.由于计算机模拟是一颗颗取样,不用预设分布模式,不存在分析方法误差和分样操作误差的叠加,误差完...     

Inverse Optimal Filtering Method for the Instrumental Spreading Correction in Size Exclusion Chromatography

Abstract

The Kalman filter based techniques are adapted to solve the most general form of Tung's integral formula, i. e. when a non-uniform, non-symmetric calibration model is employed to correct chromatograms obtained in size exclusion chromatography from instrumental broadening errors. Through this method, the inverse smoothing of a chromatogram contaminated with measurement noise of known statistics is optimally performed by minimizing the estimation error variance. The method is numerically very “robust”, improves the signal to noise ratio, provides good validation checks, and does not involve any previous parameter estimation procedure.     

Sampling variability and uncertainty in total diet studies

Here, the uncertainty budget for a total diet study (TDS) was clarified by separating the total measurement uncertainty into the uncertainty arising from the compositional heterogeneity of food items between cities (referred to as inter-city variance), the heterogeneity of food items within cities (intra-city variance), and the chemical analysis of the food samples (analytical variance) at one study design. TDS samples were collected from 14 cities in Japan. Duplicate samples collected in each city were prepared from food items purchased from different shops, and the cadmium concentrations were measured individually to obtain the intra-city variance. These results were used to show the importance of sampling design in TDSs, by evaluating a sampling method known as a multi-stage design, in which multiple samples are collected from several cities. Such schemes have been applied to TDSs, but the uncertainty involved has not been assessed. An intra-city correlation was observed between the cadmium concentrations in samples from the same city, demonstrating that the effective sample size was not simply the number of cities and shops sampled. The TDS results showed a high intra-city variance, which was greater than the inter-city variance for all of the food groups studied, and particularly for the bean and potato groups. By combining the sampling and analytical uncertainties obtained, the sampling uncertainty across different primary sampling unit sizes and secondary sampling unit sizes was obtained. As suggested by the analysis of potatoes and beans, grouping food samples from different shops in the same city can improve the representativeness of the results.     

Detection of sequence variability of the collagen type IIalpha 1 3' variable number of tandem repeat

The variable number of tandem repeat (VNTR) 3' of the collagen type II (COL2A1) gene has been shown to be highly variable with a complex molecular structure. In a previous pilot experiment we observed discordance between methods to genotype this informative marker. To further investigate the extent and molecular nature of this discordance, we genotyped a random sample of 207 Caucasian individuals with two genotyping methods and sequenced new alleles. We compared single-strand (SS) analysis, which is based on detection of size differences between the different alleles, and heteroduplex analysis (HA), which is sensitive to both size and sequence differences. Overall, 26% of discordance between the two methods was detected. Approximately two thirds of this discordance was caused by subdivision of SS-alleles 13R1 and 14R2 into HA-alleles 4A + 4B and 3B + 3C, respectively. Sequence analysis of the COL2A1 VNTR alleles 4B and 3C showed that these alleles differed in sequence, but not in size, from already described SS-alleles, which explains why they escape detection by SS. The 4B allele is a frequent allele in the population (14%) and is, therefore, important to distinguish in association studies. We conclude that HA is a reliable method when the described optimized electrophoretic conditions are used. HA is a sensitive genotyping method to document allelic diversity at this locus, which can distinguish more alleles compared to the SS method.     

Sampling hazelnuts for aflatoxin: uncertainty associated with sampling, sample preparation, and analysis

The variability associated with the aflatoxin test procedure used to estimate aflatoxin levels in bulk shipments of hazelnuts was investigated. Sixteen 10 kg samples of shelled hazelnuts were taken from each of 20 lots that were suspected of aflatoxin contamination. The total variance associated with testing shelled hazelnuts was estimated and partitioned into sampling, sample preparation, and analytical variance components. Each variance component increased as aflatoxin concentration (either B1 or total) increased. With the use of regression analysis, mathematical expressions were developed to model the relationship between aflatoxin concentration and the total, sampling, sample preparation, and analytical variances. The expressions for these relationships were used to estimate the variance for any sample size, subsample size, and number of analyses for a specific aflatoxin concentration. The sampling, sample preparation, and analytical variances associated with estimating aflatoxin in a hazelnut lot at a total aflatoxin level of 10 ng/g and using a 10 kg sample, a 50 g subsample, dry comminution with a Robot Coupe mill, and a high-performance liquid chromatographic analytical method are 174.40, 0.74, and 0.27, respectively. The sampling, sample preparation, and analytical steps of the aflatoxin test procedure accounted for 99.4, 0.4, and 0.2% of the total variability, respectively.     

数理统计在地球化学样品分析质量控制中的应用

使用Excel2013和Minitab两种常用软件对地球化学样品中CaO含量分布情况进行了研究,运用描述性统计、正态分布、背景值与异常方法对实验室分析的广西某地地球化学样品的分析数据进行了质量评价,结果表明:综合运用计算机软件和数理统计方法,能快速找到分析数据的详细信息和数据特征,判别地球化学样品实验室分析数据的准确性,找出元素的背景值和异常值并剔除异常值,比较发现,样品中CaO含量分析数据对数转换后比原始数据的分布更趋于正态分布,相比于X射线荧光光谱方法,用电感耦合等离子体发射光谱法测定的结果更符合正态分布。方法对地球化学调查样品的分析数据质量评价作了有益的尝试,揭示了数理统计方法是地球化学样品分析质量控制的有效手段。     

Classification for high-throughput data with an optimal subset of principal components

High-throughput data have been widely used in biological and medical studies to discover gene and protein functions. Due to the high dimensionality, principal component analysis (PCA) is often involved for data dimension reduction. However, when a few principal components (PCs) are selected for dimension reduction or considered for dimension determination, they are typically ranked by their variances, eigenvalues. However, this approach is not always effective in subsequent multivariate analysis, particularly classification. To maximize information from data with a subset of the components, we apply a different ranking criterion, canonical variate criterion, which considers within- and between-group variance rather than total variance in the classical criterion. Four prevalent classification methods are considered and compared using leave-one-out cross-validation. These methods are illustrated with three real high-throughput data sets, two microarray data sets and a nuclear magnetic resonance spectra data set.     

Ped_Outlier software for automatic identification of within-family outliers

A high-throughput resequencing technology has brought family based studies back into genetic research focus. Within-family outliers (the individuals whose phenotype is very much unlike the phenotype of relatives) may carry rare variants of large effects and thus resequencing of these provides a highly powered strategy for rare variants detection. On the other hand, such outliers may complicate search for common variants of smaller effects, because they may obscure a real linkage signal. We have developed a program Ped_Outlier allowing automatic detection of within-family outliers in a sample of pedigrees of arbitrary structure and size. We tested our program by identification of within-family outliers for adult height and intracranial volume in large pedigree. Results of linkage analysis of these traits demonstrated that identification of within-family outliers is one of the important steps of pedigree analysis. The program Ped_outlier is freely available at http://mga.bionet.nsc.ru/soft/index.html.     

Automated sequential trace enrichment of dialysates and robotics. A technique for the preparation of biological samples prior to high-performance liquid chromatography

The development of the sample preparation process, the automated sequential trace enrichment of dialysates, in association with a cartesian robotic sampler is described. The system has been applied to the total automation of the preparation of biological samples and high-performance liquid chromatographic analysis. Concepts of the technique are reported together with an examination of its application to free and total analyte estimation. Examples of chromatographic separations obtained from the preparation of a variety of different analytes and sample materials are given.     

Determination of total fluorine in five coal reference materials by proton-induced gamma-ray emission spectrometry

The direct non-destructive proton-induced gamma-ray emission (PIGE) technique with a germanium detector was applied to the determination of total fluorine concentration in five coal reference materials (BCR 40, NIST 1632b, NIST 1635, SARM 20 and USGS CLB-1). Duplicate analyses were made from five randomly selected bottles of each coal. Individual data are presented and some problems (calibration, proton stopping power, effects of sample heating by the proton beam, background estimation) which were encountered during this study are discussed. Sensitivity and reproducibility of the determinations, and homogeneity of the coal samples with respect to fluorine contents by analysis of variance were investigated. The present data are also compared with the few published values for these reference samples, including other PIGE data. The use of synthetic standards and spiked samples in the present study suggested that the PIGE method was more accurate than other techniques.     

Quantification in highly scattering/absorbing layered samples using photon time-of-flight measurements and confocal optical geometry

A method for depth-resolved quantification in scattering/absorbing layered samples is described. Confocal optical geometry was used in conjunction with time gated detection for non-invasive quantification of sub-surface absorbing constituents. For analysis, the time-resolved diffuse reflectance intensities from a series of layered absorbing samples were ratioed to that of a similar, non-absorbing specimen. Using this approach, absorbance information sensitive to changing sample composition was obtained. The effect of confocal optical geometry focussing on depth-resolved quantification was characterized using different portions of the time profile. In addition, imaging performance is assessed with varying focal depth, numerical aperture and effective pinhole size. Results indicate that the effect of multiple scattering on the detected signal may be reduced by using a larger numerical aperture objective and small effective pinhole size. Also, the sample absorbance was found to be more linear over a wider concentration range when compared with a large pinhole. When time information was included, the initial rising portion of the time profile was found to enhance sample absorbance linearity when a large pinhole is used. However, little enhancement was observed when the imaging pinhole size was small. Similar effects were seen at each focal depth in the sample. This finding suggests that although including time information may be beneficial, it is not needed when confocal light collection is employed in the analysis of macroscopic scattering samples.     

Sample preparation for the chromatographic determination of ecdysteroids using solid-phase extraction methods

The ecdysteroids are hormones widely distributed in insects and crustaceans, where they are involved in the regulation of moulting. Methods of sample preparation based on solid-phase extraction of the ecdysteroids from biological samples for subsequent chromatographic analysis are reviewed. Most methods use an initial partition of the sample (or extract) between water or aqueous methanol with a non-polar solvent to remove lipids. The aqueous portion is applied to a cartridge containing C₁₈-bonded silica gel. Removal of polar impurities is then effected, followed by recovery of the ecdysteroids from the cartridge and chromatographic analysis. Results are given for the use of phenylboronic acid (PBA) bonded to silica gel as a means of obtaining a much more specific method of extraction. The PBA phase was shown to have a high affinity for ecdysteroids containing a 20,22-cis-diol but not for compounds possessing only a 2,3-cis-diol.     

Suitability of nitric-sulphuric acid decomposition for the determination of tungsten and molybdenum in geochemical exploration

A mixture of nitric and sulphuric acids is used for the decomposition of geochemical samples for the estimation of tungsten. In the resulting sample solution tungsten is determined colorimetrically by the dithiol method. The decomposition procedure suggested works well for scheelite mineral. However wolframite is only partially decomposed. The same sample solution is used for estimation of molybdenum by the thiocyanate method. The method is suitable for batch analysis and results in a high throughput.     

Sample Preparation Methods for the Determination of Chlorination Disinfection Byproducts in Water Samples

Chlorination has been widely used as a disinfection method for control of pathogens in drinking water and wastewater treatment plants. Chlorination disinfection byproducts (DBPs) are formed when organic matter is present in water, and they are harmful to human health. The main groups of compounds formed are trihalomethanes (THMs), haloacetic acids (HAAs) and haloacetonitriles (HANs). Analysis of THMs, HAAs and HANs in water samples has been reported. This paper reviews the various sample preparation methods in use for analysis of THMs, HAAs and HANs in water samples.

     

不定物种的多组分体系同时测定：逐步回归法解析紫外光谱矢量数据的研究

本文采用逐步回归法对不定物种的多组分体系的紫外光谱矢量数据进行解析，可对物种及物种含量同时进行定性和定量分析，通过对两个复方药物体系（复方扑热息痛与复方维生素Ｂ）的紫外光谱数据的实际解析，表明本法能有效地完成混合物中物种及物种含量的同时定性和定量测定。     

Weighted least squares in calibration: estimating data variance functions in high-performance liquid chromatography

For minimum-variance estimation of parameters by the method of least squares, heteroscedastic data should be weighted inversely as their variance, w(i) proportional, variant 1/sigma(i)2. Here the instrumental data variance for a commercial high-performance liquid chromatography (HPLC) instrument is estimated from 5 to 11 replicate measurements on more than 20 samples for each of four different analytes. The samples span a range of over four orders of magnitude in concentration and HPLC peak area, over which the sampling variance estimates s2 are well represented as a sum of a constant term and a term proportional to the square of the peak area. The latter contribution is dominant over most of the range used in routine HPLC analysis and represents approximately 0.2% of peak area for all four analytes studied here. It includes a contribution from uncertainty in the syringe injection volume, which is found to be +/-0.008 microL. The dominance of proportional error justifies the use of 1/x2 or 1/y2 weighting in routine calibration with such data; however, the constant variance term means that these weighting formulas are not correct in the low-signal limit relevant for analysis at trace levels. Least-squares methods for both direct and logarithmic fitting of variance sampling estimates are described. Since such estimates themselves have proportional uncertainty, direct fitting requires iterative adjustment of the weights, while logarithmic fitting does not.     

Interlaced size exclusion liquid chromatography of monoclonal antibodies

Size exclusion chromatography is a widely performed analysis of monoclonal antibodies, primarily used to monitor the levels of higher weight molecular species such as aggregates. Owing to the subtleties of these separation mechanisms and frequently observed partial resolutions of components in these separations, many common methods for increasing the method throughput are not practical as they trade off resolution for speed. Short columns, high flow rates and smaller particles are examples of these approaches. In this paper a practical method is demonstrated for injecting samples onto the column in rapid succession and gating the detection window to monitor the elution of each sample individually. At any given instant approximately two samples are eluting through the column. By co-ordinating the injection and detection time windows the samples can be kept discrete and significant throughput enhancements achieved, up to nearly 2-fold improvements are demonstrated. A rudimentary theory is development to show that the throughput improvements can be predicted to approximation by simple column characteristics. Experimental results for a series of monoclonal antibodies demonstrate the equivalency of the method to a conventional injection approach, the throughput increase, and the robustness of the method.     

A proposed k0 based methodology for neutron activation analysis of samples of non-standard geometry

An internal mono-standard method has been proposed for multi element analysis. This method gives the relative concentration of the elements in a sample of non-standard shape and size. It utilizes an in-situ relative efficiency calibration and hence, does not need the cumbersome procedures, otherwise required to correct for -attenuation in the sample. To validate this method, the relative concentration of elements in IAEA RM's SL-3 and Soil-7 were analyzed with sample amounts ranging from a few milligrams to grams. The samples were counted in different non-specific geometries. The results are in good agreement with the recommended values, suggesting that this methodology could be applied for the analysis of samples of non-standard size and shape, and in principle, for the analysis of large samples.     

Validity of extracellular water assessment with saliva samples using plasma as the reference biological fluid

Extracellular water (ECW) assessment is based on dilution techniques, commonly using blood sampling. However, plasma collection is an invasive procedure. We aimed to validate the use of saliva for ECW estimation by the bromide dilution technique using plasma as the reference method, in a sample of elite athletes. A total of 89 elite athletes with a mean age of 20.4 ± 4.4 years were evaluated. Baseline samples were collected before sodium bromide oral dose administration, and enriched samples were collected 3 h post‐dose administration. The bromide concentration was assessed by high‐performance liquid chromatography. Comparison of means, concordance coefficient correlation (CCC), multiple regression and Bland–Altman analysis were performed. The ECW from saliva explained 91% of the variance in ECW by plasma with a standard error of estimation of 0.91 kg. The CCC between alternative and reference methods was 0.952. No significant trend was observed between the mean and difference of the methods, with limits of agreement ranging between ?1.5 and 2.1 kg. These findings reveal that bromide dilution volume calculated from saliva samples is a valid noninvasive method for ECW assessment in elite athletes. Copyright © 2012 John Wiley & Sons, Ltd.     

Estimation of the band broadening contribution of HPLC equipment to column elution profiles

Summary Methods to determine the contribution of the chromatographic equipment to the total band broadening which involve replacing the column by a union or a capillary tube are not suitable as they involve a fundamental change in the chromatographic system. The linear extrapolation method, based on the estimation of the relative influence of the instrument variance on solutes with different capacity factors, is a more attractive alternative method since the column remains in the chromatographic system. This method is only valid when a number of conditions are satisfied. By meeting these conditions the error in the instrument variance by using the linear extrapolation method was determined. At the same time, ways to minimise these errors were studied. Use of the linear extrapolation method in combination with conventional columns of 4.6 mm i.d. appears to yield inaccurate results. In combination with microbore columns the method can be used, provided the columns have a maximum length of 5cm and contain a packing material with a particle size of 2 or 3μm. The error in the determined instrument variance is then of the order of 2μl².