Trace element analysis of archaeological materials and the use of pattern recognition methods to establish identity

Trace elements were determined in South West African potsherds by instrumental NAA and by PIXE. The elements for which the relative spread of concentrations were greatest were selected as indicators. From these the methods of the Minimal Spanning Tree and of Nonlinear Mapping were used to classify about 60 specimens. Groups were tested by concentration, sum of concentration and normalized concentration indices. Similar groupings were obtained irrespective of which analytical data or mathematical techniques was used.     

Comparison of extraction efficiencies and LC–MS–MS matrix effects using LLE and SPE methods for 19 antipsychotics in human blood

Antipsychotic drugs are frequently associated with sudden death investigations. Detection of these drugs is necessary to establish their use and possible contribution to the death. LC–MS(MS) methods are common; however accurate and precise quantification is assured by using validated methods. This study compared extraction efficiency and matrix effects using common liquid–liquid and solid-phase extraction procedures in both ante-mortem and post-mortem specimen using LC–MS–MS. Extraction efficiencies and matrix effects were determined in five different blank blood specimens of each blood type. The samples were extracted using a number of different liquid–liquid extraction methods and compared with a standard mixed-mode solid-phase extraction method. Matrix effects were determined using a post-extraction addition approach—the blank blood specimens were extracted as described above and the extracts were reconstituted in mobile phase containing a known amount of analytes. The extraction comparison of ante-mortem and post-mortem blood showed considerable differences, in particular the extraction efficiency was quite different between ante-mortem and post-mortem blood. Quantitative methods used for determination of antipsychotic drugs in post-mortem blood should establish that there are no differences in extraction efficiency and matrix effects, particularly if using ante-mortem blood as calibrator.     

Evaluation of hybrid laser-cut and cast miniature fracture specimens

This paper presents a new hybrid laser-cutting method for producing fracture test specimens from thermosetting materials. The hybrid approach combines casting of a sheet of material with subsequent laser-cutting of the test specimens. The new approach was compared to the traditional casting method using a fracture toughness test. For this study, a compact version of the tapered double cantilever beam (cTDCB) was used as a specimen geometry for both manufacturing methods. The cTDCB specimen is crack length independent, and crack length investigations were performed to ensure the crack length independence of the cTDCB specimens. The specimens that were made by the hybrid laser-cut method were found to be comparable to the specimens obtained by the traditional casting method. Moreover, the laser-cut method provides a fast and accurate method to make a significant number of samples in a reasonable time. These tests show that the hybrid laser-cut method could be a good alternative to the traditional casting method.     

Development of headspace SPME method for analysis of volatile organic compounds present in human biological specimens

In recent years, interest has increased regarding the identification of volatile organic compounds (VOCs) for metabolic profiling, human scent identification of the living and deceased, and diagnostic potentials for certain diseases that are known for its association with distinct odor. In this study, a method has been developed that is capable of sampling, identifying, and differentiating the VOCs present in various biological specimens of forensic importance (blood, breath, buccal cells, and urine) taken from the same individuals. The developed method requires a pretreatment step to remove targeted VOCs from the sampling apparatus prior to sampling of the individual specimens. The VOCs collected from the biological specimens were characterized by solid-phase microextraction and gas chromatography/mass spectrometry with ratios of the most abundant and frequent VOCs compared using qualitative and semiquantitative methods. Blood, breath, and buccal cells required extraction procedures ranging from 18 to 21 h in order to optimize the limit of detection, which averaged 5–15 ng across these specimens. The optimal method for measuring urine VOCs was complete in less than an hour; however, the limit of detection was higher with a range of 10–40 ng quantifiable. The demonstrated sensitivity and reproducibility of the methods developed allow for population studies of human scent VOCs from various biological specimen collection kits used in the forensic and clinical fields.     

Chemometrics in near-infrared spectroscopy

Spectroscopy methods of chemical analysis are excellent for the application of chemometric methods, because the measurements at many different wavelengths provide inherently multivariate data. The chemist generally requires three categories of information from specimens under investigation: quantitative data, qualitative data, and fundamental information on the properties of the material. Spectroscopy has long been used for all three purposes; the recent application of chemometric algorithms has assisted greatly in these endeavors. Although there is some overlap, three chemometric methods correspond to the three types of information: multiple regression, discriminant analysis, and principal components analysis. The basis of these chemometric methods and some of their strengths and limitations in application to near-infrared spectroscopy are discussed.     

Requirements for bioanalytical procedures in postmortem toxicology

The application of analytical techniques in postmortem toxicology is often more difficult than in other forms of forensic toxicology owing to the variable and often degraded nature of the specimens and the diverse range of specimens available for analysis. Consequently, analysts must ensure that all methods are fully validated for the particular postmortem specimen(s) used. Collection of specimens must be standardized to minimize site-to-site variability and should if available include a peripheral blood sample and at least one other specimen. Urine and vitreous humor are good specimens to complement blood. In some circumstances solid tissues such as liver are recommended as well as gastric contents. Substance-screening techniques are the most important element since they will determine the range of substances that were targeted in the investigation and provide initial indication of the possible role of substances in the death. While immunoassay techniques are still commonly used for the most common drugs-of-abuse, chromatographic screening methods are required for general unknown testing. These are still predominately gas chromatography (GC) based using nitrogen/phosphorous detection and/or mass spectrometry (MS) detection, although some laboratories are now using time-of-flight MS or liquid chromatography (LC)–MS(MS) to cover a sometimes more limited range of substances. It is recommended that laboratories include a second chromatographic method to provide coverage of acidic and other substances not readily covered by a GC-based screen when extracts do not include all physiochemical types. This may include a gradient high-performance liquid chromatography (HPLC) photodiode array method, or better LC-MS(MS). Substance-specific techniques (e.g., benzodiazepines, opiates) providing a second form of identification (confirmation) are now divided between GC-MS(MS) and LC-MS(MS) procedures. LC-MS(MS) has taken over from many methods for the more polar compounds previously used in HPLC or in GC methods requiring derivatization. Analysts using LC-MS will need to obtain clean extracts to avoid poor and variable sensitivity caused by background suppression of the signal. Isolation techniques in postmortem toxicology tend to favor liquid extraction; however solid-phase extraction and solid-phase microextraction methods are available for many analytes.     

Trends in techniques for the extraction of drugs and pesticides from biological specimens prior to chromatographic separation and detection

The isolation of non-volatile organic poisons from biological specimens is often difficult and time consuming. This paper surveys the isolation of common drugs and pesticides from biological specimens, including serum, blood and tissue, and the effect of experimental variables on the recovery of compounds, with emphasis on recent trends in extraction techniques and new methods under development, particularly those applicable to forensic toxicology. Traditional liquid-liquid extraction techniques are increasingly being replaced by or used in combination with newer extraction techniques such as solid-phase and supercritical fluid extraction. The potential advantages and problems encountered when incorporating these new methodologies in the isolation of drugs and pesticides from biological matrices are discussed. Although early implementation of solid-phase extraction techniques in forensic toxicology has been hampered by a variety of problems, including extract quality, reproducibility and selectivity, improvements in sorbent quality and elution solvents continue to facilitate their replacement of traditional liquid-liquid extraction methods. Future developments in supercritical fluid extraction should allow this technique to develop in an extremely powerful quantitative tool for the isolation of drugs and pesticides either from solid-phase sorbents or from their endogenous matrices.     

Raman spectroscopy of hot desert, high altitude epilithic lichens

Twenty-three highly-coloured lichen specimens belonging to the genera Candelariella, Aspicilia and Xanthoria from high altitude sites in the Atacama Desert, Chile, 2300-4500 metres, have been analysed non-destructively by Raman spectroscopy. The vibrational band assignments in the spectra of the specimens, which were still attached to their limestone or sandstone substrata, were accomplished by comparison with the chemical compositions obtained from wet chemical extraction methods. Carotenoids and chlorophyll were found in all specimens as major components and the characteristic spectral signatures of calcium oxalate monohydrate (whewellite) and dihydrate (weddellite) could be identified; chemical signatures were found for these materials even in lichen thalli growing on the non-calcareous substrata, indicating probably that the calcium was provided here from wind- or rain-borne sources. The Raman spectral biomarkers for a variety of protective biomolecules and accessory pigments such as usnic acid, calycin, pulvinic acid dilactone and rhizocarpic acid have been identified in the lichens, in broad agreement with the chemical extraction profiles. The present study indicates that some form of non-destructive taxonomic identification based on Raman spectroscopy was also possible.     

Separation assay of histamine and its metabolites in biological specimens

This review summarizes the determination methods for histamine and the metabolites in biological specimens by separation techniques, such as gas chromatography, liquid chromatography and capillary electrophoresis. The typical applications using these methods are also described in this review together with the characteristics of the methods. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Comparison of caustics and the strain gage method for measuring mode I stress intensity factor of PMMA material

Both caustics and strain gage methods are shown to be effective in the determination of mode I stress intensity factor (SIF) at the crack tip. However, there is a lack of investigation with regard to the quantitative comparison of the two methods. In this paper, dynamic three-point bending tests were performed on polymethyl methacrylate (PMMA) specimens using the caustic and the strain gage methods simultaneously. The SIFs calculated by these two methods were analyzed and compared. The results show that the deviations of the SIF values between caustics and the strain gage method are slightly more significant when the orientation of the gage is obtuse rather than acute. Furthermore, this deviation increases with the gage mounted closer to the edge of the specimen when the orientation is acute. In addition, the whole cracking process could be clearly recorded by the caustic method, while the time-evolution of SIF can be roughly obtained with a limited number of strain gages during the crack propagation.     

人工神经网络用于连钱草中总黄酮和三萜酸类成分的含量预测

以连钱草的毛细管电泳指纹图谱为输入数据,以总黄酮和三萜酸类成分含量为输出数据,构建了反向传播网络、径向基函数网络和广义回归网络三种人工神经网络模型.采用三种网络模型和两种预测方法对未知样本的总黄酮和三萜酸类成分含量进行了预测,并分别比较了三种网络和两种预测方法的预测结果.另外,结合聚类分析结果和输入数据的相似度,分析了预测误差的来源.结果表明:三种网络对大部分样本的预测值与实际值都比较接近,而广义回归网络的预测效果最优;扣除奇异值后,广义回归网络的两种预测方法对未知样本的总黄酮和三萜酸类成分含量的平均预测误差分别为10.9%和0.00073%.     

Enzymic determination of cerebrospinal fluid lipid fractions

Colorimetric peroxidase-coupled procedures for the determination of several cerebrospinal fluid (CSF) lipid classes are described. These methods were modified to increase the effectiveness of each cerebrospinal fluid lipid assay by using the sample as the primary diluent for a highly concentrated reagent in an inverse concentration technique. Direct enzymic assays for the determination of CSF cholesterol (free and total), choline phospholipids, and triglycerides were adapted from existing assays to require less than 0.5 ml of sample per assay. This made determinations of the several lipid analytes possible even when samples were from pediatric specimens. In a study model, 51 pediatric CSF samples were analyzed for these lipid constituents. Mean values and standard deviations were determined. Within and between-run studies were performed by sampling from a pool of cerebrospinal fluid specimens. Within-run coefficients of variation for the several proposed procedures were less than 3% while the between-run findings for all of the procedures were less than 5%.     

Analytical methods for human biomonitoring of pesticides. A review

Biomonitoring of both currently-used and banned-persistent pesticides is a very useful tool for assessing human exposure to these chemicals. In this review, we present current approaches and recent advances in the analytical methods for determining the biomarkers of exposure to pesticides in the most commonly used specimens, such as blood, urine, and breast milk, and in emerging non-invasive matrices such as hair and meconium. We critically discuss the main applications for sample treatment, and the instrumental techniques currently used to determine the most relevant pesticide biomarkers. We finally look at the future trends in this field.     

Lichen biodeterioration of ecclesiastical monuments in northern Spain

Seven highly-coloured lichen species belonging to the genera Caloplaca, Candelariella, Aspicilia and Xanthoria from ecclesiastical buildings in northern Spain have been analysed non-destructively by FT-Raman spectroscopy. The vibrational band assignments in the spectra of the specimens, which were still attached to their limestone or sandstone substrata, were accomplished with the assistance of the chemical compositions obtained from wet chemical extraction methods. beta-Carotene was found in all specimens as the major pigment, and the characteristic spectral signatures of calcium oxalate monohydrate (whewellite) and dihydrate (weddelite) could be identified; chemical signatures were found for these materials even in lichen thalli growing the non-calcareous substrata, indicating, probably, that the calcium was provided here from wind-or-rain-borne sources. The Raman spectral biomarkers found in the lichens broadly agreed with the chemical extraction profiles as expected, but the present study indicates that some form of non-destructive taxonomic identification based on Raman spectroscopy was possible.     

Morphology and electrical breakdown properties of LDPE‐polypropylene copolymer blends

In this study, the specimens of low‐density polyethylene (LDPE) and blend polymers of LDPE and a random copolymer of ethylene and propylene were prepared by the blowing process and T‐die method. The differences in electrical breakdown properties and morphology between the specimens made by the two different methods were studied. It was found that the specimen made by the T‐die method had a higher electrical breakdown strength than the specimen made by the blowing process, except for the DC breakdown strength in some cases at 30 °C. The morphology of the specimens was investigated by means of the measurements of thermal shrinkage, infrared dichroism, and X‐ray diffraction. The specimen made by the T‐die method has a stronger orientation in both the crystalline and amorphous phases than the specimen made by the blowing process. The difference in morphology is supposed to be correlated with the difference in electrical breakdown properties between the specimens made by the two different methods. It was concluded that the electrical breakdown properties are strongly affected by the orientation of chains in the specimen. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1741–1748, 2001     

A study of ochres from an Australian aboriginal bark painting using thermal methods

The potential of thermogravimetric analysis (TG) as a tool for the characterisation of ochre paint used in indigenous Australian bark paintings has been investigated. TG has been combined with differential scanning calorimetry (DSC) and mass spectrometry (MS) to identify and quantify the main inorganic and organic components present in the paints. The results obtained were supported by comparison with infrared spectra and XRD data obtained for the same specimens. The potential of thermal methods for the characterisation ochres has been demonstrated, with subtle differences between small samples being able to be identified.     

Determination of metals in biofluids and tissues: sample preparation methods for atomic spectroscopic techniques

Several sample preparation methods unique to each instrumental technique exist for the elemental analysis of biological specimens, but no review or book has dealt with them. The present review is an attempt to fill this void and focuses on sample preparation methods unique to atomic and X-ray spectroscopic techniques. The techniques covered are: flame and electrothermal AAS, inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence spectrometry (XRF) since these are most commonly used in trace element analysis of biological materials. The intent is not to present the procedural details for the various tissues or elements, but rather to highlight the methods which are unique to each instrument. The bibliography accompanying this review should aid the analytical chemist in his/her search for the detailed preparation protocols.     

High speed determination of beta-receptor blocking agents in human urine by liquid chromatography/tandem mass spectrometry

Beta-receptor blocking agents are present on the international market in a huge variety. The International Olympic Committee prohibits the use of these drugs in several sport sections and doping control laboratories analyse urine samples of high-performance athletes with different techniques. Therefore, fast and reliable methods are required to enable a sensitive detection of many drugs and a high throughput of samples. In the present study a screening procedure is described using high speed liquid chromatography and multiple reaction monitoring to identify 32 beta-receptor blocking agents extracted from human urine. Urine specimens (blank urine samples, spiked urine samples and specimens of excretion studies) were hydrolysed, extracted and analysed within 7 min. Quasi-molecular ions (M(+) + H) of the beta-blockers are generated by means of an atmospheric pressure chemical ionization interface followed by collision-induced dissociation in a triple quadrupole mass spectrometer and subsequent detection of daughter ions. Proposals for the origin of common and individual secondary ions are presented.     

振动注塑PP的拉伸蠕变研究

分别通过改变机械振动注塑机的频率(5~25 Hz)和压力(10~18 MPa)获得不同条件下成型的PP样条,然后在各种成型条件下的PP样条上分别施加相同的拉伸力(F=125 N),进行24 h拉伸蠕变实验.结果表明,在相同的振动频率(10 Hz)和不同的振动压力下成型的PP试样,其24 h蠕变量随着压力的增大而减小;在相同振动压力(12 MPa)和不同的振动频率下成型的PP试样,其24 h蠕变量随着频率的增大而增大.当振动频率达到f=10 Hz的时候,其24 h拉伸蠕变量的变化趋于平缓.同时,也对不同振动条件下注塑的PP试样进行拉伸实验,冲击实验和动态力学性能测试,讨论了成型条件对性能的影响.