Teaching Chemometrics with a Bioprocess: Analytical Methods Comparison Using Bivariate Linear Regression

We present an advanced analytical chemistry laboratory experiment involving chemometrics. Students perform a comparison of two analytical methods by checking several analyte concentrations within a certain range by using least-squares linear regression. They obtain statistical information such as the presence of constant and proportional biases. The exercise is based on the determination of glucose levels using two colorimetric methods (enzymatic and Somogyi—Nelson) in a very simple batch system formed by an infusion of tea, glucose, and a combination of a yeast (Schizosacaromyces pombe) and a bacteria (Acetobacter xylimun), usually named Kombucha. Several samples are collected during a week of laboratory work, and measurements are performed in a subsequent four-hour laboratory class. Although commercial computer software exists for a variety of statistical applications, specific programs for the application of statistics to analytical chemistry are not prevalent. In order to solve this particular problem, a Matlab 5.3 routine is presented.     

Determination of sulfur components in natural gas: A review

More stringent environmental regulations as well as higher demands presently being imposed on the sulfur content of natural gas feed-stocks for chemical processes necessitate the development of new analytical procedures for sulfur determination in natural gas. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. The complexity of the natural gas matrix as well as the extremely low concentration levels at which the sulfur species occur make the development of these analytical methods a true challenge. In this review the three steps common for analytical methods for trace analysis in complex matrices, i.e. pretreatment, chromatographic separation, and detection, are discussed in detail. Possible methods for calibration of the system are discussed in the final section. Various techniques to determine sulfur in natural gas are described. Depending on the application, the most suitable system has to be selected. For example, for on-line application in a hazardous area a simple and rugged system is required, i.e. a simple gas chromatograph with a flame photometric detector, while for laboratory application a more complex instrument including preconcentration, column switching, and more exotic detection systems could be more suitable. Therefore it is crucial to define the requirements of the instrument at an early stage and use the information in this review article to develop/select a dedicated instrument/procedure for the problem at hand.     

A view of uncertainty at the bench analytical level

 The problem with which analytical laboratories are confronted, after traceability of their results has been demonstrated, is correctly estimating their uncertainty– to which traceability is also to some extent subject. While the general principles for calculating the uncertainty of physical measurements are applicable to chemical metrology, some refinements are needed, especially careful selection and planning the level at which uncertainty will be estimated by each laboratory in accordance with its capacity and required demands. Depending on the particular decision to be made, the mechanism to be used to estimate the uncertainty varies markedly; also, the rigour of the estimation increases with increasing stringency of the demands. This paper describes the primary sources of uncertainty in chemical metrology and discusses different approaches to its estimation in relation to the type of analytical laboratory concerned. The view presented tries to be close to the bench analytical level, in order to be practical and flexible for laboratories, although it could sometimes be considered slightly heterodox. Received: 25 March 1997 · Accepted: 20 September 1997     

Statistical Comparison of Multiple Methods for the Determination of Dissolved Oxygen Levels in Natural Waters

The following experiment reinforces students working knowledge of statistics by utilizing the t test to compare the results of two independent methods for the determination of dissolved oxygen (DO). In this experiment students utilize a dissolved oxygen probe to determine the levels of DO in natural waters at two sampling locations while obtaining samples of water from the laboratory for analysis using the classic Winkler titration. The importance of using proper sampling methods and techniques to obtain representative samkples is a large focus of the prelaboratory discussion and is continually stressed during fieldwork. After analyzing the water samples by the DO mete and the Winkler titration, students pool the class data and are asked to determine if the two methods for dissolved oxygen agree at each sampling location. The students are then asked to determine if the DO levels at the different sampling locations are statistically different or not. The students are asked to consider why their results agree or differ from the theoretical value they calculate using Henrys law.     

Experience with in-house PT-schemes in the chemical industry

There are many different means of demonstrating the quality of performance of an analytical laboratory. Proficiency testing (PT) is just one! As in other analytical fields, interlaboratory comparisons play an important role in the chemical industry. Collaborative trials or method performance studies do have a long tradition in this field. Sometimes they were designed as laboratory performance studies with the clear aim of making analytical results comparable, e.g. petrol, coal, gas, noble metals analyses – not to mention the biggest PT scheme run on a daily world-wide basis – trade itself. All this is an ongoing process, which started long before the idea of assessing and accrediting the performance of analytical laboratories was born. However, when striving for accreditation in 1996, the analytical production laboratories of the Chemicals Business Unit of the Bayer AG in Germany implemented another facet of PT schemes. In-house-PT schemes are performed regularly and turned out to be useful in evaluating, monitoring, and thus improving, the quality of routine analytical work. Received: 5 December 2000 Accepted: 15 January 2001     

Summary of ISO/TC 201 International Standard ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres and its implementation for imaging laboratory X-ray photoelectron spectrometers (XPS)

ISO 18516:2019 Surface chemical analysis—Determination of lateral resolution and sharpness in beam-based methods with a range from nanometres to micrometres revises ISO 18516:2006 Surface chemical analysis—Auger electron spectroscopy and X-ray photoelectron spectroscopy—Determination of lateral resolution. It implements three different methods delivering parameters useful to express the lateral resolution: (1) the straight edge method, (2) the narrow line method and (3) the grating method. The theoretical background of these methods is introduced in ISO/TR 19319:2013 Surface chemical analysis—Fundamental approaches to determination of lateral resolution and sharpness in beam-based methods. The revised International Standard ISO 18516 delivers standardized procedures for the determination of the (1) effective lateral resolution by imaging of square-wave gratings, the (2) lateral resolution expressed as the parameter D_12–88 characterizing the steepness of the sigmoidal edge spread function (ESF) determined by imaging a straight edge and (3) the lateral resolution expressed as the full width of half maximum of the line spread function (LSF), w_LSF, determined by imaging a narrow line. The last method also delivers information on the shape of the LSF, which characterizes an individual imaging instrument. Finally, the implementation of all three standardized methods in the field of imaging laboratory X-ray photoelectron spectroscopy (XPS) is shortly presented. This part of the letter is based on the use of a new test sample developed at ETH Zurich, Switzerland. This test sample displays a micrometre scaled pattern motivated by the resolving power of recent imaging XPS instruments.     

The ultra-clean chemical laboratory (UCCL) at the Institute for Reference Materials and Measurements (IRMM)

 An Ultra-Clean Chemical Laboratory (UCCL) has been built at IRMM to allow reliable, contamination-free chemical treatment of samples prior to inorganic elemental or isotopic analysis. The concept is intended to guarantee a dust-free environment as well as resistance to corrosion even if hot concentrated mixtures of acids are continuously used, thus establishing not a clean or dust-free room but a clean laboratory. The excellent air quality is demonstrated both by particle measurements and the analysis of acids purified by subboiling distillation in the UCCL. Received: 1 March 1996/Accepted: 16 April 1996     

The task of the analytical chemist in industry

The duties of analytical chemists extend over a wide field, covering many branches of science, and in industry, too, a considerable part of the work consists of analytical determinations. The analytical chemist himself can do much to derive more satisfaction from his more or less subservient task and at the same time to meet more appreciation of his work.Analytical work in a large laboratory consists of: testing of materials and operating control analyses, analyses required for research work, standardisation of analytical methods and analytical research. Decentralisation of this work is often recommendable, especially as regards daily control analyses. However, there should be a central department which is thoroughly acquainted with all the analytical work in the whole laboratory, which sees to it that this work is done as efficiently as possible, which gives advice as to when and where existing methods are to be applied and which tests and developes new methods. Such an “analytical centre” is the source of analytical information for the whole staff.The large number of methods for the determination of the same magnitude and the many variations in procedure for one and the same method sometimes call for standardisation, to facilitate comparison of the results of various investigators.The analytical chemists in a laboratory should also be enabled to carry out analytical research work, so as to retain the necessary freshness and keep abreast of modern developments in their field.     

Probiotics Production: An Interesting Example for the Undergraduate Analytical Chemistry Laboratory

An analytical chemistry laboratory experiment for undergraduates that combines traditional analytical chemistry techniques with the interdisciplinary field of biotechnology is presented. It involves a process in which the combination of a yeast (Schizosacaromyces pombe) and a bacteria (Acetobacter xylimun), usually named Kombucha, in a very simple culture of commercial black tea and glucose produces metabolites that are sampled and quantified by students. Students determine the biomass and quantify the production of several organic acids, and the consumption of glucose. This is an interdisciplinary project where students apply many tools of the general analytical process and combine results obtained by all the participating students to learn the characteristics of a biotechnological process. Overall, the system discussed is easy to implement because the selected micro-organisms are not pathogenic, are safe and easy to manipulate, and are resistant to contamination.     

A Colorful Investigation of a Diprotic Acid: A General Chemistry Laboratory Exercise

A general chemistry laboratory experiment that can be completed in a single laboratory period is described that familiarizes students with the acid—base chemistry of a diprotic acid and with the use of visible spectroscopy to determine species concentrations. This experiment is a modified version of a previously described laboratory exercise developed for an upper-division quantitative analysis course. Students work in teams and as a class to generate different ionization states of various highly absorbing dyes. Both spectroscopic and potentiometric (pH) data is collected using LabWorks II stations, but other inexpensive pH meters and visible spectrometers (e.g., Spec 20s) are suitable. A spreadsheet template is used to determine the percent composition of various ionization states of a diprotic acid and to determine the pK_a values. Besides introducing students to fundamental tools and key chemical concepts, this laboratory is also inexpensive to operate and utilizes nontoxic, colorful solutions.     

Quantitative 1H NMR spectroscopy (qNMR) in the early process development of a new quorum sensing inhibitor

2-methyl-5,6,7,8-tetrahydro-2H-chromen-4(3H)-one (called 6-oxo) is presented as a new AI-1 quorum sensing inhibitor for Vibrio harveyi. The development of a chemical process to afford traceable materials for new biological assays demands the development of analytical methods to ensure their purity and quality. This work describes the use of quantitative ¹H nuclear magnetic resonance (NMR) spectroscopy (qNMR) to assess the purity of a sample of 6-oxo (99.88%) and a sample of its major process impurity (E)-1-(2-hydroxycyclohex-2-en-1-yl)but-2-en-1-one (called HCB; 98.28%). To explore the scope of the use of qNMR to quantify the amount of low-content components in samples related to the chemical process for 6-oxo synthesis, this work also determined the amount of 6-oxo in two HCB samples: (a) the high-purity HCB sample described above and (b) a crude HCB sample collected during the chemical process. Despite the complexity of the crude sample, the amount of 6-oxo was readily assessed and could help to estimate the extent to which 6-oxo was already formed during the HCB synthesis. This information can help the understanding of how the process parameters can be modified to improve the performance of the whole process, by controlling the reaction mechanisms working at each step of this chemical process. In this context, our results reinforce qNMR as a complementary analytical tool for the quantification of the main component found in a sample, contributing to the standardization of reference materials and thus allowing the development of analytical methods for process control and traceability of the samples used for biological assays.     

A MASSive Laboratory Tour. An Interactive Mass Spectrometry Outreach Activity for Children

It is imperative to fascinate young children at an early stage in their education for the analytical sciences. The exposure of the public to mass spectrometry presently increases rapidly through the common media. Outreach activities can take advantage of this exposure and employ mass spectrometry as an exquisite example of an analytical science in which children can be fascinated. The presented teaching modules introduce children to mass spectrometry and give them the opportunity to experience a modern research laboratory. The modules are highly adaptable and can be applied to young children from the age of 6 to 14 y. In an interactive tour, the students explore three major scientific concepts related to mass spectrometry; the building blocks of matter, charged particle manipulation by electrostatic fields, and analyte identification by mass analysis. Also, the students carry out a mass spectrometry experiment and learn to interpret the resulting mass spectra. The multistage, inquiry-based tour contains flexible methods, which teach the students current-day research techniques and possible applications to real research topics. Besides the scientific concepts, laboratory safety and hygiene are stressed and the students are enthused for the analytical sciences by participating in “hands-on” work. The presented modules have repeatedly been successfully employed during laboratory open days. They are also found to be extremely suitable for (early) high school science classes during laboratory visit-focused field trips.

Contracting and calculating traces over the N-electron space: Two powerful tools for obtaining averages

In this study the work performed at our laboratory is outlined by emphasizing the leading role that the idea of average has in our research. © 1996 John Wiley & Sons, Inc.     

Analytical procedures for environmental and biological monitoring

Summary Health protection of persons exposed to chemical substances is achieved by limitation and supervision of the concentrations a) of substances in the air (Environmental Monitoring, EM) and b) of substances and metabolites in body fluids (Biological Monitoring, BM). Both strategies belong to the sphere of responsibility of the analytical chemist. EM and BM show requirements which are different in some characteristic facts among them: EM. The assessment of exposure is difficult because the concentrations strongly depend on the location and time of measurement. The analytical determination of ppm and ppb concentrations in the air in general do not make problems nowadays. Unsolved, however, is the problem of the quality control and the determination of certain species of substances. BM. It offers a better means of the assessment of individual exposure. The complexity of the biological matrix, its low availability, and the small concentration of substances are still a great problem for analytical chemistry. Nowadays g/l-concentrations of metals, organic solvents etc. can routinely be determined in biological matrices. Efficiency of analytical chemistry, however, must further be improved. Certain substances, for instance PAH's, certain metals like Pt, Ni, Co cannot be determined in the required range of concentrations. Huge efforts have to be done to determine the substances at the location of their effects for instance bound to DNA, Hb or certain proteins.The possibilities and limitations of instrumental analysis in the field of environmental and occupational health are discussed using characteristic examples. The problems of analytical reliability and the comparability of results are also discussed.Dedicated to Prof. Dr. G. Tölg, Dortmund, on the occasion of his 60th birthday     

Desirability functions as response in a d‐optimal design for evaluating the extraction and purification steps of six tranquillizers and an anti‐adrenergic by liquid chromatography‐tandem mass spectrometry

Internal standards can be added at different stages of an analytical procedure. When they are added at the beginning of a multiresidue method and their behavior is not exactly the same as that of the analytes, the intended correction for small variations within the analytical process could not be achieved. Because of this, in the present work, the use of d ‐optimal designs together with desirability functions is proposed to state the experimental response under study. The overall desirability function used relates two analytical criteria: to assess a similar chemical behavior of each analyte in relation to its internal standard and to avoid a significant reduction of the absolute peak area of the internal standards. This strategy has been applied to the analysis of the effect of four factors related to the extraction and purification steps of six tranquillizers and a β‐blocker from pig muscle analyzed by liquid chromatography–tandem mass spectrometry. The effect of those factors has been evaluated by means of an ad hoc d ‐optimal design consisting of only 11 experiments. The resulting levels of the four factors that enable to achieve the greatest overall desirability have also been compared with those obtained when either the standardized or absolute peak area has been considered as response. Differences in both the significant factors and their optimum levels have been observed. It is noticeable that the experimental effort necessary to study the effect of the factors has been reduced by more than 50% thanks to the d ‐optimal design. Copyright © 2015 John Wiley & Sons, Ltd.     

The scientific legacy of Howard Vincent Malmstadt

Howard Malmstadt was a true giant of Analytical Chemistry and clearly one of the most influential analytical chemists of the last 50 years. Howard, through his own work and that of his students (first generation) and their students (second generation) and their students' students (third generation) changed the course of Analytical Chemistry. His research interests were broad and ranged from analytical solution chemistry (titrimetry and reaction rates) and electrochemistry to atomic and molecular spectroscopy, chemical instrumentation, clinical chemistry and automation. Howard was also one of the most innovative and influential educators of our time. He changed forever the analytical curriculum through his many books on Electronics for Scientists, most written in conjunction with Chris Enke and Stan Crouch. Their texts and short courses went from pioneering the application of tube-based analog electronics (servo systems and operational amplifiers) in scientific measurements to the impact that integrated circuits and digital electronics would have on laboratory measurements. He strongly believed in the importance of “hands-on” in education. To this end, he expended considerable personal effort and time to see not only the development and commercialization of an effective laboratory infrastructure to support education in analog and digital electronics, but also oversaw the development of modular instrumentation for spectroscopy. Over the years he received many awards from the Analytical Chemistry community for his outstanding efforts and contributions to teaching and research. Many of Howard's students went on into academia. They and their students now represent the ongoing legacy for analytical chemistry that evolved from Howard's laboratory at Illinois. A remarkable diversity of research programs are underway in their laboratories. Topics range from atomic, laser, mass, and Raman spectroscopy to detection technology, analytical education, micro-fabricated instrumentation, and intercellular analytical measurements.     

Quality assurance in the view of a commercial analytical laboratory

 The necessity for analytical quality assurance is primarily a feature of the analytical process itself. With the full establishment of the EU domestic market, it is also becoming a legal necessity for an increasing number of analytical laboratories. The requirements which laboratories will need to fulfil are stipulated in DIN EN 45 001. Accredited testing laboratories must in fact provide evidence that they work solely in accordance with this standard. National and EU commissions, which are legislative authorities, tend therefore to specify analytical methods, e.g. in the form of regulations or appendices thereto, intended to ensure that results from different laboratories will be comparable and hence will stand up in a court of law. The analytical quality assurance system (AQS), introduced by the Baden-Württemberg Ministry for the Environment in 1984, obliges laboratories to regularly participate in collaborative studies and thereby demonstrate their ability to provide suitably accurate analyses. This alone, however, does not sufficiently demonstrate the competence of a laboratory. Only personal appraisal of the laboratory by an auditor, together with the successful analysis of a sample provided by the same and performed under his observation, can provide proof of the competence of the laboratory. From an analytical point of view, the competence of a laboratory must be regarded as the decisive factor. Competence can only be attained through analytical quality assurance, which thus must be demanded of all laboratories. Received: 4 October 1996 Accepted: 15 January 1997     

The progress of analytical chemistry 1910-1970

The progress of analytical chemistry during the period 1910-1970 is reviewed. Topics considered are: the volume of the relevant literature, the countries in which the work was done, the language in which the papers were written, the literature of analytical chemistry, broad trends in the subject, methods used, and the analytical chemistry of individual elements. Some tentative conclusions are made about future short-term trends.     

Metrology for chemical engineers

 The first full-semester course on Quality Assurance in Chemical Measurement was held at the Technical University of Denmark from September to December 1999. The course required sufficient knowledge of basic statistics to understand and apply the methods recommended in ISO 5725–1/6 Accuracy of Measurement Methods and Results. The main purpose of the course was, however, to familiarize PhD students with the BIPM philosophy, using the International Organization for Standardization (ISO) Guide to Expression of Uncertainty in Measurement, which was accepted by IUPAC and other international scientific organizations in 1993. Chemists are notoriously reluctant to accept the BIPM philosophy, but the appearance of a new Draft Guide Quantifying Uncertainty in Analytical Measurement at the EURACHEM Workshop in Helsinki in June 1999 stimulated us to make an attempt to overcome such chemical prejudice. After thorough reading of the examples presented in the Draft Guide, each of the participating students had to prepare an uncertainty budget for their own particular project and present it to the other participants for discussion. Eventually the students learned how to verify their uncertainty budgets by means of experimental results; this invariably entailed a re-evaluation of the uncertainty components in the original budget. The revised budget was again verified, and this iteration was continued until the budget correctly predicted the uncertainty of individual results covering the whole range of applicability of the analytical method. The paper presents the detailed structure of this first course, as well as improvements in the next course scheduled for the year 2000.