The deplorable state of the description of the use of certified reference materials in the literature.

A detailed survey of 26 scientific journals showed that journal editors and a majority of authors of the re- c viewed papers seem unconcerned by the importance of correctly reporting their use of certified reference materials (CRMs). Only around 55% of the abstracts surveyed mention the use of CRMs described in these papers. This, however, is of key importance as the abstract of a paper is most widely available in electronic media. Many authors mentioned the use of CRMs in passing, often in incomplete form and without giving any details of the results obtained. Some are confused about the source of the reference material used, as they fail to report the type or the producer of CRMs applied. Others use materials that do not match the samples analyzed or do not see the need to use any CRM, despite the availability of suitable materials. Even in cases where correct data were given for type and producer of the CRMs, frequently the proper use and statistical evaluation are questionable. To improve this situation it is necessary that publishers should give recommendations where and how the use of CRMs should be described.     

Compliance with legal requirements: definition of limits, sampling and measurement uncertainty

In many cases compositional requirements for foodstuffs (e.g. limits for the fat, protein, dry matter, or water content) are established by legislation. Adequate compliance testing is possible only if limits are clearly defined, taking measurement and sampling uncertainty into consideration. Furthermore, decisions on compliance must be based on samples which reflect the composition of the quantity to be evaluated. The resulting sample sizes are normally regarded by food inspection authorities as being much larger than acceptable. Consequently, an alternative strategy should be developed. Autocontrol data (i.e. inspection results obtained by the factory) in principle provide an adequate data basis for decisions on compliance. However, they must be reliable and the food inspection authority must have access to these data on request. Using these data and on condition that they show an approximate normal distribution, an inspection strategy based on arithmetic mean and standard deviation can be developed. Reliable and transparent decisions on compliance can thus be made. In many cases an adequate verification of food authenticity requires a comparison of raw material and product composition. Maximum acceptable differences, taking the relevant sources of variation into consideration, have to be defined and should be used instead of limits. Received: 17 April 2002 Accepted: 23 June 2002     

The potential use of continuous-flow isotope-ratio mass spectrometry as a tool in forensic soil analysis: a preliminary report

The use of continuous-flow isotope-ratio mass spectrometry (CF-IRMS) as a tool in soil analysis has been assessed as part of a larger study using a number of geological techniques applied in a forensic context. Carbon and nitrogen isotopic ratios, delta13C and delta15N, have been analysed to investigate situations which have arisen from crime casework. Three questions have been addressed: the role of spatial variation found over the short-scale (less than 20 m), temporal variation over a period of almost 2 years, and the variation found between source soils and soil transferred to footwear soles during a simple one-stage transfer process. Results are presented for the three experiments. The use of carbon and nitrogen isotopes has been shown to be useful in discriminating between soil types and sample locations, even when sampling occurs at a different time (as might be the case with a crime scene). In cases of primary transfer (from a source soil by a one-stage transfer to another surface, in this case, shoes and boots), the combination of carbon and nitrogen isotope ratios is a valuable tool in discriminating between sites and in showing the relationship of the transferred samples to the relevant source soils. Used in combination with other analytical techniques, isotopic analysis may prove to be a useful tool in a forensic context.     

Proving beyond all reasonable doubt – Analytical aspects

An overview is presented of the problems and challenges facing the analyst who is asked to provide data to support the law. Factors that the analyst should consider include: the legal reasons for performing the analysis; situations where analytical data should and should not be used in support of litigation; the scientific basis for the legislation; and the sample source and method of sampling.     

Proving beyond all reasonable doubt--analytical aspects

An overview is presented of the problems and challenges facing the analyst who is asked to provide data to support the law. Factors that the analyst should consider include: the legal reasons for performing the analysis; situations where analytical data should and should not be used in support of litigation; the scientific basis for the legislation; and the sample source and method of sampling.     

Sample size planning for classification models

In biospectroscopy, suitably annotated and statistically independent samples (e.g. patients, batches, etc.) for classifier training and testing are scarce and costly. Learning curves show the model performance as function of the training sample size and can help to determine the sample size needed to train good classifiers. However, building a good model is actually not enough: the performance must also be proven. We discuss learning curves for typical small sample size situations with 5–25 independent samples per class. Although the classification models achieve acceptable performance, the learning curve can be completely masked by the random testing uncertainty due to the equally limited test sample size. In consequence, we determine test sample sizes necessary to achieve reasonable precision in the validation and find that 75–100 samples will usually be needed to test a good but not perfect classifier. Such a data set will then allow refined sample size planning on the basis of the achieved performance. We also demonstrate how to calculate necessary sample sizes in order to show the superiority of one classifier over another: this often requires hundreds of statistically independent test samples or is even theoretically impossible. We demonstrate our findings with a data set of ca. 2550 Raman spectra of single cells (five classes: erythrocytes, leukocytes and three tumour cell lines BT-20, MCF-7 and OCI-AML3) as well as by an extensive simulation that allows precise determination of the actual performance of the models in question.     

Impact of calibrator concentrations and their distribution on accuracy of quadratic regression for liquid chromatography–mass spectrometry bioanalysis

Despite the common use of quadratic regression in LC–MS bioanalysis, how calibrator concentrations should be determined is still vague. Both the number and concentrations of calibrators are usually selected arbitrarily to each one's preference. The purposes of this research were to evaluate the impact of calibrator concentrations and to find new approaches with improved accuracy and reduced cost for LC–MS bioanalysis. It was found for the first time that the lower and upper limits of quantitation plus their geometric mean are the three critical concentrations for quadratic regression. When different concentration ranges, different response precisions, and various degrees of downward quadratic responses were simulated, the best accuracy was obtained by including these critical concentrations and using fewer calibrator concentrations with more replicates per concentration, instead of using more calibrator concentrations in duplicate. In many cases, when the aforementioned three concentrations are used, as few as two replicates per concentration are enough for routine use and up to 20% of time and cost can be saved. Furthermore, downward quadratic response should be eliminated or reduced as much as possible and upper limit quality control must be included in each batch to monitor the accuracy at the high concentration end. The retrospective data analysis of published experimental results corroborates the aforementioned findings. Finally, the typical “concerns” and potential applications of the new quadratic regression approaches are discussed.     

A Validated Approach to Discovering Implication Knowledge from Empirical Data with Applications in Chemometrics

Implication knowledge is useful for drawing conclusions or confirming hypotheses based on some observed data. The challenge here is where/how to derive such knowledge. Traditional knowledge acquisition methodologies or tools have limited power in that they rely on human knowledge engineers' judgements and are applicable only under controlled situations. It would be desirable as well as imperative if we can demonstrate any automatic means of mining such implication knowledge directly from empirical data-this is because in practical applications,data samples are usually available and most importantly the automatically induced implications are less subjective and mathematically sound. As a response to this challenge, our work has developed and validated a new method of automatically discovering implication knowledge by statistically inducing the implication relationships among the data attributes in empirically-obtained sample data.     

Ensuring the reliability of stable isotope ratio data—beyond the principle of identical treatment

The need for inter-laboratory comparability is crucial to facilitate the globalisation of scientific networks and the development of international databases to support scientific and criminal investigations. This article considers what lessons can be learned from a series of inter-laboratory comparison exercises organised by the Forensic Isotope Ratio Mass Spectrometry (FIRMS) network in terms of reference materials (RMs), the management of data quality, and technical limitations. The results showed that within-laboratory precision (repeatability) was generally good but between-laboratory accuracy (reproducibility) called for improvements. This review considers how stable isotope laboratories can establish a system of quality control (QC) and quality assurance (QA), emphasising issues of repeatability and reproducibility. For results to be comparable between laboratories, measurements must be traceable to the international δ-scales and, because isotope ratio measurements are reported relative to standards, a key aspect is the correct selection, calibration, and use of international and in-house RMs. The authors identify four principles which promote good laboratory practice. The principle of identical treatment by which samples and RMs are processed in an identical manner and which incorporates three further principles; the principle of identical correction (by which necessary corrections are identified and evenly applied), the principle of identical scaling (by which data are shifted and stretched to the international δ-scales), and the principle of error detection by which QC and QA results are monitored and acted upon. To achieve both good repeatability and good reproducibility it is essential to obtain RMs with internationally agreed δ-values. These RMs will act as the basis for QC and can be used to calibrate further in-house QC RMs tailored to the activities of specific laboratories. In-house QA standards must also be developed to ensure that QC-based calibrations and corrections lead to accurate results for samples. The δ-values assigned to RMs must be recorded and reported with all data. Reference materials must be used to determine what corrections are necessary for measured data. Each analytical sequence of samples must include both QC and QA materials which are subject to identical treatment during measurement and data processing. Results for these materials must be plotted, monitored, and acted upon. Periodically international RMs should be analysed as an in-house proficiency test to demonstrate results are accurate.     

The deplorable state of the description of the use of certified reference materials in the literature

A detailed survey of 26 scientific journals showed that journal editors and a majority of authors of the reviewed papers seem unconcerned by the importance of correctly reporting their use of certified reference materials (CRMs). Only around 55% of the abstracts surveyed mention the use of CRMs described in these papers. This, however, is of key importance as the abstract of a paper is most widely available in electronic media. Many authors mentioned the use of CRMs in passing, often in incomplete form and without giving any details of the results obtained. Some are confused about the source of the reference material used, as they fail to report the type or the producer of CRMs applied. Others use materials that do not match the samples analyzed or do not see the need to use any CRM, despite the availability of suitable materials. Even in cases where correct data were given for type and producer of the CRMs, frequently the proper use and statistical evaluation are questionable. To improve this situation it is necessary that publishers should give recommendations where and how the use of CRMs should be described.     

Individuation of characteristic parameters of “glass paste” of Meridional Etruria by the use of scientific methodologies

The individuation of parameters that characterize decorations in “glass paste” of Etruscan jewels in Meridional Etruria area, by the use of scientific methodologies, has the aim to collocate this typology of manufacts in a historical and geographical context and to improve the knowledge of the technology connected with their realization. The term “glass paste” is widely used in humanistic literature to describe different materials, all based on a “glass like” composition, but its definition is lacking or confusing if the term is not referred to a scientific meaning.The glass analysis is difficult owing to the complexity of the elements that compose the various classes of vitreous materials. For this reason the interpretation of the composition table containing the values of the numerous glass elements, induces the use of statistical methods for the elaboration of the results. The multivariate analysis can be a valid tool for an immediate lecture of the common characteristics of the different typologies of vitreous materials.In this work, the application of the Principal Component Analysis (PCA), has been applied for the elaboration of chemical composition data obtained by electronic microanalysis (SEM-EDS) on findings coming from Etruscan archaeological sites of Nepi and Cerveteri, and on pearls of a necklace from Castellani's Collection. Besides, an attempt has been made to compare the chemical elements found in the vitreous materials of the jewelry with the elements of sands from probable sites along the rivers present in the Etruscan sites by following the indications reported by historical fonts.The obtained results furnished information in various directions, either for the characterization of each historical sample analyzed or the validation of the applied statistical methodology for the composition data elaboration, besides it has been possible to contribute in the knowledge of the possible existence of glass production sites in the Meridional Etruria, more specifically for the realization of decoration in glass paste.     

Is there a future for biomonitoring of elemental air pollution? A review focused on a larger-scaled health-related (epidemiological) context

The present paper focuses on biomonitoring of elemental atmospheric pollution, which is reviewed in terms of larger-scaled biomonitoring surveys in an epidemiological context. Based on the literature information, today’s availability of solar-powered small air filter samplers and fibrous ion exchange materials is regarded as adequate or an even better alternative for biomonitor transplant materials used in small-scaled set-ups, but biomonitors remain valuable in larger-scaled set-ups and in unforeseen releases and accidental situations. In the latter case, in-situ biomonitoring is seen as the only option for a retrospective study: biomoniors are there before one even knows that they are needed. For biomonitoring, nuclear analytical techniques are discussed as key techniques, especially because of the necessary multi-element assessments in both source recognition and single-element interpretation. To live up to the demands in an epidemiological context, larger-scaled in-situ biomonitoring asks for large numbers of samples, and consequently, for large total sample masses, this all to ensure representation of both local situations and survey area characteristics. Possibly, this point should direct studies into new “easy-to-sample” biomonitor organisms, of which high masses and numbers may be obtained in field work, rather than continue with biomonitors such as lichens. This also means that both sample handling and processing are of key importance in these studies. To avoid problems in comparability of analytical general procedures in milling, homogenization and digestion of samples of large masses, the paper proposes to involve only few but high-quality laboratories in the total element assessment routines. In this respect, facilities that can handle large sample masses in the assessment of element concentrations are to be preferred. This all highlights the involvement of large-sample-volume nuclear facilities, which, however, should be upgraded and automated in their operation to ensure the necessary sample throughput in larger-scaled biomonitoring.     

Fast analysis with Zeeman graphite furnace AAS

Stabilized Temperature Platform Furnace (STPF) methods have been adapted and altered to reduce the analytical time to less than 1 min per sample with no loss of analytical precision or accuracy. It is shown that this could be further reduced to about 30 s per sample if certain changes in instrumentation are implemented, especially in the software and firmware that control the autosampler. The sample uptake rate for the autosampler should overlap the cooldown of the tube from the prior determination. Also, the sample should be deposited onto a heated platform. In this work the pyrolysis step and, in most cases, the use of a matrix modifier has been omitted. Since backgrounds were therefore larger, the use of Zeeman correction was usually required, but continuum background correction was not tried. To confirm that these fast analytical methods might be practical, more than 10 standard reference materials were analyzed for several elements including Pb, Cd, Cu, Ni, As and Cr. The paper is not primarily intended to provide routine and reliable methods; it is intended to test the feasibility of these fast methods.     

Uncertainty calculations in the certification of reference materials. 2. Homogeneity study

 Many reference materials undergo a batch certification, which implies that a small number of samples is taken from a batch, characterised, and these results are then assumed to be representative of all remaining samples. An important aspect in this design is the translation of the characterisation data to a single sample, as usually the laboratory will be using only one sample of the batch. This form of homogeneity is very important and can be influenced to a certain extent by well-designed sample preparation procedures. Another subsampling problem associated with many reference materials is that only a small test portion is drawn from the sample to carry out the measurement. Obviously, this test portion must be representative of the sample, otherwise the certified value is still not applicable. Both kinds of homogeneity tests are examined in the paper and evaluated using practical examples. Received: 31 May 2000 · Accepted: 29 July 2000     

Bioanalytical procedures for detection of chemical agents in hair in the case of drug-facilitated crimes

The use of a drug to modify a person’s behavior for criminal gain is not a recent phenomenon. However, the recent increase in reports of drug-facilitated crimes (sexual assault, robbery) has caused alarm in the general public. The drugs involved can be pharmaceuticals, such as benzodiazepines (flunitrazepam, lorazepam, etc.), hypnotics (zopiclone, zolpidem), sedatives (neuroleptics, some anti-H1) or anaesthetics (γ-hydroxybutyrate, ketamine), drugs of abuse, such as cannabis, ecstasy or LSD, or more often ethanol. To perform successful toxicological examinations, the analyst must follow some important rules: (1) obtain as soon as possible the corresponding biological specimens (blood and urine); (2) collect hair about 1 month after the alleged event; (3) use sophisticated analytical techniques (gas or liquid chromatography coupled to tandem mass spectrometry, MS/MS, headspace gas chromatography); and (4) take care in the interpretation of the findings. Drugs used to facilitate sexual assaults can be difficult to detect (active products at low doses, chemical instability), possess amnesic properties and can be rapidly cleared from the body (short half-life). In these situations, blood or even urine can be of low interest. This is the reason why some laboratories have developed an original approach based on hair testing. Hair was suggested as a valuable specimen in situations where, as a result of a delay in reporting the crime, natural processes have eliminated the drug from typical biological specimens. While there are a lot of papers that have focused on the identification of drugs in hair following chronic drug use, those dealing with a single dose are very scarce. The experience of the author and a review of the existing literature will be presented for cases involving benzodiazepines, hypnotics, γ-hydroxybutyrate and various sedatives or chemical weapons. The expected concentrations in hair are in the low picogram/milligram range for most compounds. Hair analysis may be a useful adjunct to conventional drug testing in sexual assault. It should not be considered as an alternative to blood and urine analyses, but as a complement. This approach may find useful applications, but the definition of legally defensible cutoff values would require much more data. MS/MS technologies appear as a prerequisite in drug-facilitated cases.     

Prompt Gamma-Ray Activation Analysis: Fundamentals and Applications

Prompt gamma-ray activation analysis (PGAA) is an important nuclear analytical technique that complements conventional neutron activation analysis (NAA). When a target is placed in a beam of neutrons, gamma-rays emitted upon neutron capture are measured by a shielded germanium detector, yielding quantitative elemental analysis. The radiation is penetrating and the analysis both nondestructive and independent of the chemical form of the element(s) being measured. The technique is most useful for measurement of light elements (H, B, C, N, Si, P, S, Cl) which can not be easily measured by other methods. Best sensitivity is achieved with neutron beams from research reactors. Although sample preparation is minimal, care must be taken to select proper standards and blanks, and numerous corrections must sometimes be applied to the data from the complex spectra. PGAA has proven useful for multielement analysis of a wide variety of different materials spanning a broad range of scientific disciplines. Of particular importance has been the measurement of hydrogen in materials.     

Accurate ab initio gradient calculation of the structures and conformations of some boric and fluoroboric acids. Basis-set effects on angles around oxygen

Accurate geometry determinations by SCF computation are reported for BF₂H, H₂BOH, two conformers of FHBOH,F₂BOH, three conformers of HB(OH)₂, and three conformers of FB(OH)₂. The effect of adding polarization functions to the double zeta basis set is examined in detail both with respect to alteration of the computed absolute values of the structural parameters and to changes in the consistency of the computed relative values. It is shown that geometry computation should be done at a level which is adequate to produce small and constant offset values for the parameters sought, i.e. constant and predictable residual errors resulting from use of a finite basis set and neglect of electron correlation. In the rare situations when the desired chemical information is found in absolute rather than relative values of the parameters, the offset correction can be added to the computed value. In many cases, such structure evaluations are at least as reliable as those from the best experiments. For the compounds in this study, substitution of either F or OH increases the ionic character of both the B---F and B---bonds. The B---F bond is slightly more ionic than B---O. The OH group is a slightly stronger σ electron-acceptor and π electron-donor than is F.     

Simplified batch equilibration for D/H determination of non‐exchangeable hydrogen in solid organic material

Hydrogen isotopic analysis of organic materials has been widely applied in studies of paleoclimate, animal migration, forensics, food and flavor authentication, and the origin and diagenesis of organic matter. Hydrogen bound to carbon (C‐H) generally retains isotopic information about the water present during organic matter synthesis and associated biosynthetic fractionations, but hydrogen bound to other elements (O, S, or N) can readily exchange with atmospheric water vapor and reflects recent exposure to water or vapor. These two pools must be separated to obtain meaningful information from isotope ratios of organic materials. Previously published analytical methods either replace exchangeable H chemically or control its isotopic composition, usually by equilibration with water or waters of known isotopic composition. In addition, the fraction of H that is exchangeable can vary among samples and is itself of scientific interest. Here we report an improved and automated double‐equilibration approach. Samples are loaded in a 50‐position autosampler carousel in an air‐tight aluminum equilibration chamber. Water vapor of known isotopic composition is pumped through the chamber at 115°C for at least 6 h. After flushing with dry N₂ and being cooled, the carousel is rapidly transferred from the equilibration chamber to a He‐purged autosampler attached to a pyrolysis elemental analyzer connected to an isotope ratio mass spectrometer. By equilibrating two aliquots of each sample with two isotopically distinct waters, it is possible to calculate both (1) the D/H ratio of non‐exchangeable H, and (2) the fraction of H that is exchangeable. Relative to previous double‐equilibration techniques, this approach offers significant reductions in sample size and labor by allowing simultaneous equilibration of several tens of samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation of Commercial Graphenes

For graphene to achieve its full scientific and commercial potential, reliable mass production of the material on the multi-tonne scale is essential. We have investigated five samples of graphene obtained from commercial sources that state they can supply the product on the tonne scale per annum. From electron microscopy at the micrometre to the nanometre scale, and neutron vibrational spectroscopy, we find that none of the materials examined were 100 % isolated graphene sheets. In all cases, there was a substantial content of graphite-like material. The samples exhibited varying oxygen contents, this could be present as carboxylic acid (although other oxygenates, quinones, phenols may also be present) or water. We emphasise that INS spectroscopy is particularly useful for the investigation of inorganic materials that will be used commercially: it provides atomic scale information from macroscopic (10’s of g) amounts of sample, thus ensuring that the results are truly representative.