Principal component analysis: a chemometric aid for classification of polluted and unpolluted mussels

Ten trace elements (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) were determined in the dissolved ash of the edible part of wild mussels (28 samples) from a polluted site by electrothermal atomic absorption spectrometry. The distribution of the concentration of each element in the mussels was first investigated by means of a test of normality. The correlation matrix around the mean was used as a starting matrix for principal component analysis (PCA). Ten variables were reduced to two principal components, accounting for 77% of the total variance; Al, Cr, Mn, Fe, Zn, Cd and Pb are all positively associated with the first principal component and form a cluster of variables, indicating a common terrigenous origin. Comparison with 43 samples of unpolluted mussels from a nearby hatchery, on the basis of eight common variables (concentration of Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb; 71 samples) by using a two-dimensional plot of PC scores, allows the mussels from the two sites to be differentiated.     

Direct μ-flow injection isotope dilution ICP-MS for the determination of heavy metals in oil samples

The determination of trace elements in oil samples and their products is of high interest as their presence significantly affects refinery processes and the environment by possible impact of their combustion products. In this context, inductively coupled plasma mass spectrometry (ICP-MS) plays an important role due to its outstanding analytical properties in the quantification of trace elements. In this work, we present the accurate and precise determination of selected heavy metals in oil samples by making use of the combination of μ-flow direct injection and isotope dilution ICP-MS (ICP-IDMS). Spike solutions of ⁶²Ni, ⁹⁷Mo, ¹¹⁷Sn and ²⁰⁶Pb were prepared in an organic solvent, mixed directly with the diluted oil samples and tested to be fit for purpose for the intended ID approach. The analysis of real samples revealed strong matrix effects affecting the ICP-MS sensitivity, but not the isotope ratio measurements, so that accurate results are obtained by ICP-IDMS. Typical relative standard deviations were about 15% for peak area and peak height measurements, whereas the isotope ratios were not significantly affected (RSD < 2%). The developed method was validated by the analysis of a metallo-organic multi-element standard (SCP-21, typically applied as a calibration standard) and the standard reference material SRM1084a (wear metals in lubricating oil). The obtained results were in excellent agreement with the certified values (recoveries between 98% and 102%), so the proposed methodology of combining μ-flow direct injection and ICP-IDMS can be regarded as a new tool for the matrix-independent, multi-element and reliable determination of trace elements in oil and related organic liquids.     

Major,minor and trace element mass fractions determined using ED-XRF,WD-XRF and INAA for five certified clay reference materials: NCS DC 60102–60105; NCS DC 61101 (GBW 03101A, 03102A, 03103, and 03115)

Major, minor and trace element mass fractions were determined using wavelength dispersive and energy dispersive X-ray fluorescence and instrumental neutron activation analysis for five clay certified reference materials (NCS DC 60102–60105, 61101) distributed by the National Research Center for Certified Reference Materials in China. We report mass fractions for 10 major and the following 29 minor and trace elements: As, Ba, Ce, Co, Cr, Cs, Cu, Eu, Hf, La, Lu, Nb, Nd, Ni, Pb, Rb, Sb, Sc, Sm, Sr, Ta, Tb, Th, U, V, Y, Yb, Zn, and Zr.     

Evaluation of strontium isotope abundance ratios in combination with multi-elemental analysis as a possible tool to study the geographical origin of ciders

In order to evaluate alternative analytical methodologies to study the geographical origin of ciders, both multi-elemental analysis and Sr isotope abundance ratios in combination with multivariate statistical analysis were estimated in 67 samples from England, Switzerland, France and two Spanish regions (Asturias and the Basque Country). A methodology for the precise and accurate determination of the ⁸⁷Sr/⁸⁶Sr isotope abundance ratio in ciders by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. Major elements (Na, K, Ca and Mg) were measured by ICP-AES and minor and trace elements (Li, Be, B, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Sb, Cs, Ba, La, Ce, W, Tl, Pb, Bi, Th and U) were measured by ICP-MS using a collision cell instrument operated in multitune mode. An analysis of variance (ANOVA test) indicated that group means for B, Cr, Fe, Ni, Cu, Se, Cd, Cs, Ce, W, Pb, Bi and U did not show any significant differences at the 95% confidence level, so these elements were rejected for further statistical analysis. Another group of elements (Li, Be, Sc, Co, Ga, Y, Sn, Sb, La, Tl, Th) was removed from the data set because concentrations were close to the limits of detection for many samples. Therefore, the remaining elements (Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba) together with ⁸⁷Sr/⁸⁶Sr isotope abundance ratio were considered for principal component analysis (PCA) and linear discriminant analysis (LDA). Finally, LDA was able to classify correctly 100% of cider samples coming from different Spanish regions, France, England and Switzerland when considering Na, Mg, Al, K, Ca, Ti, V, Mn, Zn, As, Rb, Sr, Mo, Ba and ⁸⁷Sr/⁸⁶Sr isotope abundance ratio as original variables.     

Analysis of elemental concentration censored distributions in breast malignant and breast benign neoplasm tissues

The total reflection X-ray fluorescence method was applied to study the trace element concentrations in human breast malignant and breast benign neoplasm tissues taken from the women who were patients of Holycross Cancer Centre in Kielce (Poland). These investigations were mainly focused on the development of new possibilities of cancer diagnosis and therapy monitoring. This systematic comparative study was based on relatively large (∼ 100) population studied, namely 26 samples of breast malignant and 68 samples of breast benign neoplasm tissues. The concentrations, being in the range from a few ppb to 0.1%, were determined for thirteen elements (from P to Pb). The results were carefully analysed to investigate the concentration distribution of trace elements in the studied samples. The measurements of concentration of trace elements by total reflection X-ray fluorescence were limited, however, by the detection limit of the method. It was observed that for more than 50% of elements determined, the concentrations were not measured in all samples. These incomplete measurements were treated within the statistical concept called left-random censoring and for the estimation of the mean value and median of censored concentration distributions, the Kaplan–Meier estimator was used. For comparison of concentrations in two populations, the log-rank test was applied, which allows to compare the censored total reflection X-ray fluorescence data. Found statistically significant differences are discussed in more details. It is noted that described data analysis procedures should be the standard tool to analyze the censored concentrations of trace elements analysed by X-ray fluorescence methods.     

昆明西山植物微量元素主成分分析

用主成分软件分析昆明西山植物微量元素含量特征，元素Ｍｎ，Ｐｂ，Ｎｉ含量的累计贡献率达８４％，从而建立了以Ｍｎ，Ｐｂ，Ｎｉ为主导的三个主成分方程。     

青海生活饮用水中矿质元素含量检测以及主成分分析

为了深入认识青海生活饮用水中矿质元素存在的现状,并对饮用水资源高效开发利用与保护提供一定的科学基础,本研究采用微波消解,电感耦合等离子体质谱（Inductively coupled plasma mass spectrometry,ICP-MS）法分析青海西宁市区、民和回族土族自治县、循化撒拉族自治县、化隆回族自治县、海东市乐都区、互助土族自治县、大通回族土族自治县、门源回族自治县、湟源县、贵德县、贵南县、兴海县、同德县、刚察县、天峻县、乌兰县、都兰县、玛多县、格尔木市和德令哈市共计20个地区的生活饮用水中17种矿质元素K、Ca、Mg、Na、Fe、Mn、Zn、Al、Cu、Pb、Cd、Ge、As、Hg、Cr、Co和Se的含量,并对测定结果进行主成分分析。结果表明：17种元素的相对标准偏差范围为1.52% - 3.89%,加标回收率范围是97.63% - 100.85%。此外,20个地区的生活饮用水中富含及其丰富的微量元素,其中德令哈市饮用水的钙含量达到32.75 ± 0.29 mg·L-1,海东市乐都区的饮用水中Se含量达到1.09 ± 0.01 mg·L-1,有潜在生理毒性的元素如Pb、Cd、As、Hg、Cr的含量较低。在此基础上,将水样17个元素进行主成分分析降维得到7个线性不相关主成分,7个主成分方差贡献率分别为19.69%、16.05%、11.02%、10.41%、8.28%、7.39%、6.52%,合计贡献率达79.36%,可综合初始数据的绝大部分信息。通过雷达图分析,每个主成分在20个地区间的差异显著。每个主成分综合的元素信息各不相同。     

Chemical characterization of ancient potteries from Himera and Pestavecchia necropolis (Sicily, Italy) by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES)

Thirty-eight samples of pottery were analyzed for determining chemical composition in order to establish their provenance. The potteries tested in the present research come from Himera and Pestavecchia archaeological sites. After digestion in microwave oven, the samples have been analyzed for fourteen minor elements (Ba, Cd, Co, Cr, Cu, Ga, Li, Mn, Ni, Pb, Sr, Ti, Tl, and Zn) and six major elements (Al, Ca, Fe, K, Mg, and Na). Chemical analysis was carried out by Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP–OES). The most abundant minor elements are Cr, Ba and Ni. Cr concentration ranged from 66 to 3635 mg kg^{− 1}, Ba concentration ranged from 388 to 2677 mg kg^{− 1} and Ni concentration ranged from 35 to 1758 mg kg^{− 1}. The relative standard deviation (RSD) of the replicates on the concentrations of analyzed metals ranged from 0.07% to 14%.The aim of this study is to assign the local or non-local provenance of the examined potteries, in particular validating and clarifying archaeological hypothesis based on the simple visual examination and stylistic characterization of ceramic objects. Principal component analysis performed on the dataset, together with the application of cluster technique and non statistical analysis, allowed the identification of three main groups of samples and a lonely one (R 97). In particular, sample R 97 shows high Cr concentration (3635 mg kg^{− 1}) and high Ni concentration (1758 mg kg^{− 1}), typical of Corinthian pottery. The results of chemical analysis show that the stylistic features are not always sufficient to correctly identify the origin of a ceramic object.     

Elemental fingerprint profile of beer samples constructed using 14 elements determined by inductively coupled plasma–mass spectrometry (ICP-MS): multivariation analysis and potential application to forensic sample comparison

Determination of elemental fingerprint profile of 40 commercial beer samples was performed using inductively coupled plasma–mass spectrometry combined with principal component analysis and receiver operating characteristic (ROC) analysis. Fourteen trace elements, ⁵¹V, ⁵²Cr, ⁵⁹Co, ⁶⁰Ni, ⁷⁵As, ⁸²Se, ⁹⁵Mo, ¹¹¹Cd, ¹¹⁵In, ¹²¹Sb, ¹³³Cs, ²⁰⁸Pb, ²⁰⁹Bi, and ²³⁸U, were monitored. All 40 beer samples are distinguishable by using the proposed method. ROC analysis showed that individual beer samples can be correctly identified via the magnitude of its correlation coefficient with respect to the other beers with low false positive rate. The obtained results suggested that the elemental fingerprint technique is feasible for sample differentiation and comparison.     

Seasonal variation of natural radionuclides and some elements in plant leaves

Leaf and aerosol samples were monthly collected in Mt. Sefuri (Fukuoka Prefecture). Radioactivities of ⁷Be, ²¹⁰Pb and ⁴⁰K were determined with gamma-ray spectrometry. The concentrations of some elements in the leaf samples were determined by neutron activation analysis. Similar seasonal variation of ⁷Be and ²¹⁰Pb was observed between leaf and aerosol samples, high in spring and winter and low in summer. Correlation factors for trace elements contained in the leaf show large variations. This indicates that the contribution of two sources (atmospheric deposition and uptake from soil) is very variable.     

Application of Inductively Coupled Plasma Spectrometric Techniques and Multivariate Statistical Analysis in the Hydrogeochemical Profiling of Caves—Case Study Cloșani,Romania

The aim of the study was to develop the hydrogeochemical profiling of caves based on the elemental composition of water and silty soil samples and a multivariate statistical analysis. Major and trace elements, including rare earths, were determined in the water and soil samples. The general characteristics of water, anions content, inorganic and organic carbon fractions and nitrogen species (NO₃⁻ and NH₄⁺) were also considered. The ANOVA—principal component analysis (PCA) and two-way joining analysis were applied on samples collected from Cloșani Cave, Romania. The ANOVA-PCA revealed that the hydrogeochemical characteristics of Ca²⁺-HCO₃⁻ water facies were described by five factors, the strongest being associated with water-carbonate rock interactions and the occurrence of Ca, Mg and HCO₃⁻ (43.4%). Although organic carbon fractions have a lower influence (20.1%) than inorganic ones on water characteristics, they are involved in the chemical processes of nitrogen and of the elements involved in redox processes (Fe, Mn, Cr and Sn). The seasonal variability of water characteristics, especially during the spring, was observed. The variability of silty soil samples was described by four principal components, the strongest influence being attributed to rare earth elements (52.2%). The ANOVA-PCA provided deeper information compared to Gibbs and Piper diagrams and the correlation analysis.     

High resolution inductively coupled plasma mass spectrometry (HR-ICPMS) determination and multivariate evaluation of 10 trace elements in mussels from 7 sites in Limfjorden, Denmark

The contents of V, Cr, Co, Ni, Cu, Ga, Rb, Cd, Ba, and Pb in the soft tissue of blue mussel (Mytilus edulis) were determined by a high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) method. Sample digestions were performed in closed microwave vessels using nitric acid and hydrogen peroxide. Using HR-ICPMS it is possible to resolve the analytical peaks from otherwise interfering polyatomic ions with a mass resolution setting of 4000 (Cr, Ni, Cu). The proposed method was validated using a mussel tissue reference material (NIST SRM 2974). The proposed method was applied to real samples of blue mussel from seven sites in the inlet “Limfjorden”, Denmark, and the levels of trace elements found were compared with the levels found in an earlier study. For the mussel samples large inter-regional differences in trace element concentrations in the tissues were recorded. The mussels from the different sites could be separated using principal component analysis (PCA). Comparison with the levels of trace elements in mussels found in 1982 showed that the trace elemental contamination has increased during the last 15 years. From the data obtained, mussel tissue appears to be good bio-indicator for identification of coastal areas exposed to metallic contaminants.     

High resolution inductively coupled plasma mass spectrometry (HR-ICPMS) determination and multivariate evaluation of 10 trace elements in mussels from 7 sites in Limfjorden, Denmark

The contents of V, Cr, Co, Ni, Cu, Ga, Rb, Cd, Ba, and Pb in the soft tissue of blue mussel (Mytilus edulis) were determined by a high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) method. Sample digestions were performed in closed microwave vessels using nitric acid and hydrogen peroxide. Using HR-ICPMS it is possible to resolve the analytical peaks from otherwise interfering polyatomic ions with a mass resolution setting of 4,000 (Cr, Ni, Cu). The proposed method was validated using a mussel tissue reference material (NIST SRM 2974). The proposed method was applied to real samples of blue mussel from seven sites in the inlet "Limfjorden", Denmark, and the levels of trace elements found were compared with the levels found in an earlier study. For the mussel samples large inter-regional differences in trace element concentrations in the tissues were recorded. The mussels from the different sites could be separated using principal component analysis (PCA). Comparison with the levels of trace elements in mussels found in 1982 showed that the trace elemental contamination has increased during the last 15 years. From the data obtained, mussel tissue appears to be good bio-indicator for identification of coastal areas exposed to metallic contaminants.     

Determination of the provenance of majolica ceramics from Europe by thermoluminescence employing principal components

Thermoluminescence data, obtained from majolica pottery after irradiation in the laboratory with gamma rays, were studied using the principal components technique to determine if the places of manufacture of this ceramic are differentiated one from another. A total of ten provenances in Holland, Spain and Italy was established by principal components. Six variables were used for the statistical analysis: the three glow-peaks positions, the relative intensity of the second peak to the first peak, the relative intensity of the third peak to the first peak, and the area under the glow curve.The precision for these parameters was about ± 5%, but the precision of the variables for a suite of standards was much higher. In addition, two groups of sherds collected in Latin America, and previously assigned to the provenances of Cataluna and Sevilla (Spain) by artistic criteria, were investigated in this study. All six samples of Cataluna agreed well with their previous assignment of provenance, but several of the samples assigned previously to Sevilla were not related unambiguously to this provenance, although they were with certainty excluded from other provenances.     

New application of a traditional analytical method – arsenic removal from water works sludge during iron(III) chloride coagulant production

A new method for the detection of trace elements in polar ice cores using laser ablation with subsequent inductively coupled plasma mass spectrometry analysis is described. To enable direct analysis of frozen ice samples a special laser ablation chamber was constructed. Direct analysis reduces the risk of contamination. The defined removal of material from the ice surface by means of a laser beam leads to higher spatial resolution (300– 1000 μm) in comparison to investigations with molten ice samples. This is helpful for the detection of element signatures in annual layers of ice cores. The method was applied to the successful determination of traces for the elements Mg, Al, Fe, Zn, Cd, Pb, some rare-earth elements (REE) and minor constituents such as Ca and Na in ice cores. These selected elements serve as tracer elements for certain sources and their element signatures detected in polar ice cores can give hints to climate changes in the past. We report results from measurements of frozen ice samples, the achievable signal intensities, standard deviations and calibration graphs as well as the first signal progression of ²⁰⁸Pb in an 8,000-year-old ice core sample from Greenland. In addition, the first picture of a crater on an ice surface burnt by an IR laser made by cryogenic scanning electron microscopy is presented.     

Colonne chromatographique pastillable pour la determination d'elements traces par spectrometrie des rayons-x de fluorescence sur resine chelatante: Compressible chelating resin column for the determination of trace elements by x-ray fluorescence spectrometry

Compressible chelating resin column for the determination of trace elements by x-ray fluorescence spectrometry. Trace metals at μg l^-1 levels are preconcentrated on Chelex-100 (Dowex A-1) resin in a Makrolon cartridge. The loaded cartridge is pressed to a pellet (125°C, 3500 bars), which serves as the target for x.r.f. spectrometry. Recoveries are quantitative; relative standard deviations for Cd, Hg, Pb and Zn are better than 6%. The pellets can withstand many exposures and can be stored for further measurements.     

ON THE ORIGIN OF LOW TEMPERATURE THERMOLUMINESCENCE IN NUCLEIC ACID BASES: EXCITATION AND EMISSION SPECTRAL STUDIES

Abstract. Thermoluminescence excitation spectra of adenine, guanine, thymine and 1,3-dimethyluracil were observed to be similar to their phosphorescence excitation spectra. Intensity dependence studies of thermoluminescence induced by ultraviolet light suggest that thermoluminescence could not be due to biphotonic ionisation of the molecule by UV. Evidence is presented which demonstrates that the fluorescence component observed in thermoluminescence of some compounds may not be due to triplet-triplet fusion. Further, phosphorescence and thermoluminescence measurements following excitation with monochromatic light at very low intensities and short durations have shown for both a linear dependence on excitation intensity. It thus appears that direct entry of the electrons from the traps into the singlet manifold is necessary for explaining the fluorescence component of thermoluminescence.     

Use of neutron activation analysis for the characterization of single-wall carbon nanotube materials

Instrumental neutron activation analysis (INAA) and prompt gamma neutron activation analysis (PGAA) were used to characterize a variety of single-wall carbon nanotube (SWCNT) materials from different principal production processes, as well as a material containing SWCNTs together with other carbon species, catalyst residues, and trace element contaminants to be issued by the National Institute of Standards and Technology for characterization and distribution as Standard Reference Material SRM 2483 Carbon Nanotube Soot. INAA proved to be well suited for the direct determination of catalyst and contaminant trace elements requiring only minimal sample preparation. PGAA complemented the INAA data in particular with determinations of the light elements. Carbon and hydrogen results provided information on the materials purity and storage properties. Strategies for the quality assurance of the measurements in these new materials were developed. INAA and PGAA data were provided for the value assignment of mass fractions of catalyst and trace elements in the candidate SRM and a systematic overview was obtained of the catalyst and trace element contaminants associated with each of the major production routes.     

Neutron activation analysis on ancient Greek silver coins and related materials

66 archaic Greek silver coins have been analyzed for the minor elements Cu, Au, Bi and Pb, and for the trace elements Na, Mn, Co, Ni, As, Sn, Sb and Ir. Instrumental neutron activation has been used for the determination of Cu and Au and atomic absorption spectroscopy for Pb and Bi. The trace elements could be detected only after a separation of the interfering matrix activities by an extraction with a diethyl-dithio-carbamate complex. The homogeneity of Au and Cu in the coins and the significance of the trace elements are discussed. The statistical evaluation of the analytical data reveals distinct groups for coins of some provenances.     

Partial least squares X-ray fluorescence determination of trace elements in sediments from the estuary of Nerbioi-Ibaizabal River

The feasibility of partial least squares (PLS) regression modeling of X-ray fluorescence (XRF) spectra of estuarine sediments has been evaluated as a tool for rapid trace element content monitoring. Multivariate PLS calibration models were developed to predict the concentration of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn in sediments collected from different locations across the estuary of the Nerbioi-Ibaizabal River (Metropolitan Bilbao, Bay of Biscay, Basque Country). The study was carried out on a set of 116 sediment samples, previously lyophilized and sieved with a particle size lower than 63 μm. Sample reference data were obtained by inductively coupled plasma mass spectrometry. 34 samples were selected for building PLS models through a hierarchical cluster analysis. The remaining 82 samples were used as a test set to validate the models. Results obtained in the present study involved relative root mean square errors of prediction varying from 21%, for the determination of Pb at hundreds μg g⁻¹ level, up to 87%, for Ni determination at little tens μg g⁻¹ level. An average prediction error of ±37% for the 14 elements under study was obtained, being in all cases mean differences between predicted and reference results of the same order than the standard deviation of three replicates from a same sample. Residual predictive deviation values obtained ranged from 1.1 to 3.9.