Elemental analysis of dust trapped in air conditioner filters for the assessment of Lahore city’s air quality

A study was undertaken to assess the air quality of Lahore by the elemental analysis of air conditioner (AC) filter dust samples collected from 15 different commercial sites. Samples were prepared using the Leeds Public Analyst Method and were analyzed using instrumental neutron activation analysis (INAA) for up to 31 elements. The elements Al, As, Ba, Ce, Co, Cr, Cs, Fe, Hf, K, La, Lu, Mn, Na, Nd, Rb, Sc, Sm, Sn, Ta, Th, Yb and Zn were detected in all 15 samples whereas the remaining elements have been detected in fewer samples; i.e. Mg, Sb and Tb were detected in 14 samples, Br and V in ten samples, U in nine samples and Ca and Ti in eight samples only. Al, Ca, Fe, K, Mg and Na were determined in all samples at percentage levels. The concentrations of most elements were found to lie around the mean values for the 15 samples studied and were not orders of magnitude different. However the concentrations of Ca, Mg, Sn and Zn were found to be more variable and were found to be dependant on activities such as construction, fruit and vegetable handling, tin plating and transport, respectively.     

One-year’s experience of a ‘repeat analysis’ quality programme for blood gas analysers

The aim of this study was to determine the value of a quality assurance (QA) programme based on the repeat analysis principle, where a sample is analysed at one site, and sent to another site for repeat analysis and the comparison of the two sets of values. Once each day a routine blood gas sample, collected from a patient in the Intensive Therapy Unit (ITU) of the hospital, was analysed by the ITU nurse on the ITU blood gas analyser. The air bubble was expelled and the sample sealed and sent to the biochemistry laboratory immediately. The sample was re-analysed in the biochemistry laboratory. This programme was continued for a year. The biochemistry laboratory results (gold standard) were compared with the ITU results and rule breaches were notified to ITU immediately after the repeat analysis. All results were graphed and linear regressions and correlation coefficients calculated. The correlation coefficients ranged from r ²=0.9317 for pH to r ²=0.4381 for pO². All parameters except pO₂ and Na⁺ gave satisfactory correlations. The Na⁺ results should be adjusted by inserting a slope and intercept. It is suspected that improvement in the pO₂ would be possible if the time between ITU and biochemistry analyses could be reduced from its current levels.Presented at the 8th Conference on Quality in the Spotlight, 17–18 March 2003, Antwerp, Belgium     

Löwdin’s bracketing function revisited

A variational principle is formulated for Löwdin’s bracketing function. Setting the bracketing function stationary leads to the eigenvalue equation of the resolvent operator. An Eckart-type inequality is derived for the wavefunction optimized this way. A linearized approximation of the resolvent eigenvalue equation—reminiscent of the simplest coupled electron pair (CEPA0) treatment—is examined. We prove that the asymmetric energy formula of the resulting approximate function is a strict lower bound.     

Determination of the standard deviation for proficiency assessment from past participant’s performances

The ??uncertainty function?? introduced by Thompson et al. estimates the reproducibility standard deviation as a function of concentration or mass fraction. This model was successfully applied to data derived from three proficiency testing schemes aiming at the quantification of cadmium, lead and mercury in blood and urine. This model allows the estimation of standard deviation for the performance assessment for proficiency testing rounds.     

Models for Mandel’s formula

Photon-counting models based on Poisson transforms was pioneered by Mandel (Proc. Phys. Soc. 74, 233–243 1959). This note derives a collection of some sixteen flexible models for the formula suggested by Mandel (Proc. Phys. Soc. 74, 233–243 1959). The corresponding estimation procedures are also derived by the method of moments. We expect that this work could serve as a useful reference for photon-counting problems.     

Extension of Fermat’s last theorem in Minkowski natural spaces

Journal of Mathematical Chemistry - Minkowski natural (N?+?1)-dimensional spaces constitute the framework where the extension of Fermat’s last theorem is discussed. Based on...     

Production of certified reference materials for mycotoxins: IRMM’s view on the assessment of uncertainties

Analytical difficulty and the economic importance of controlling mycotoxin levels in food and feed led the Community Bureau of Reference (BCR) to prepare a series of certified reference materials (CRM) for various mycotoxins. Because of the wide acceptance of these CRM and the need to ensure the comparability and traceability of measurements in the future it is necessary to prepare and certify new batches of mycotoxin reference materials (RM). In the following text two different approaches for evaluation of the characterisation uncertainty of CRM will be compared using the certification of aflatoxin M₁ (AfM₁) in milk powder as an example. The conventional approach is based on evaluation of characterisation exercise data; the alternative approach is based on measurement uncertainties of the employed analytical methods. Because laboratories are using totally different approaches to estimate the measurement uncertainties, combination of the uncertainties obtained from the participating laboratories was not recommended. Therefore, a new integrated approach for assessment of the measurement uncertainties of the analytical methods on the basis of additional data collected during the characterisation exercise will be described. The conventional approach was found to be the most appropriate and economical approach to evaluate the characterisation uncertainty as a characterisation exercise must be performed anyway to establish the property values of candidate (C)RM, irrespective of whether or not reliable measurement uncertainties can be provided by the laboratories. An integrated approach for assessment of measurement uncertainties based on additional characterisation data as applied here to enable use of an uncertainty-based approach provides more information but is too time-consuming and cost-intensive to become common practice.     

Modelling European quality assurance procedures for analysers monitoring emissions under the EU’s Industrial Emissions Directive

Accreditation and Quality Assurance - A model has been created to investigate the uncertainty of a gas analyser operating according to the European Standard EN 14181, which ensures that the...     

(Xeno)metabolomics for the evaluation of aquatic organism’s exposure to field contaminated water

Environmental (xeno)metabolomics offers a major advantage compared to other approaches for the evaluation of aquatic organism’s exposure to contaminated water because its allows the simultaneous profiling of the xenometabolome (chemical xenobiotics and their metabolites accumulated in an organism exposed to environmental contaminants) and the metabolome (endogenous metabolites whose levels are altered due to an external stressor). This approach has been widely explored in lab exposure experiments, however in field studies environmental (xeno)metabolomics has only started in the last years. In this review, the papers published so far that have performed different (xeno)metabolomics approaches for the evaluation of aquatic organisms exposed to contaminated water are presented, together with their main achievements, current limitations, and future perspectives. The different analytical methods applied including sample pre-treatment (considering matrix type), platforms used (Nuclear Magnetic Resonance (NMR) and low- or high-resolution Mass Spectrometry (MS or HRMS)), and the analytical strategy (target vs non-target analysis) are discussed. The application of (xeno)metabolomics to provide information of xenobiotics mixtures accumulated in exposed organisms, either in lab or field studies, as well as biomarkers of exposure and biomarkers of effect are debated, and finally, the most commonly metabolic pathways disrupted by chemical contamination are highlighted.     

Data fusion methodologies for food and beverage authentication and quality assessment – A review

The ever increasing interest of consumers for safety, authenticity and quality of food commodities has driven the attention towards the analytical techniques used for analyzing these commodities. In recent years, rapid and reliable sensor, spectroscopic and chromatographic techniques have emerged that, together with multivariate and multiway chemometrics, have improved the whole control process by reducing the time of analysis and providing more informative results. In this progression of more and better information, the combination (fusion) of outputs of different instrumental techniques has emerged as a means for increasing the reliability of classification or prediction of foodstuff specifications as compared to using a single analytical technique. Although promising results have been obtained in food and beverage authentication and quality assessment, the combination of data from several techniques is not straightforward and represents an important challenge for chemometricians. This review provides a general overview of data fusion strategies that have been used in the field of food and beverage authentication and quality assessment.     

Green’s function method and the first-order linear differential equation

Use of a compact form of the general solution of the first-order linear differential equation allows establishing a direct connection with the Green’s function method, providing an interesting interpretation of the result. This interpretation is valid for a wide range of physical and chemical problems.     

Forecasting China’s natural gas consumption based on a combination model

Ensuring a sufficient energy supply is essential to a country. Natural gas constitutes a vital part in energy supply and therefore forecasting natural gas consumption reliably and accurately is an essential part of a country's energy policy. Over the years, studies have shown that a combinative model gives better projected results compared to a single model. In this study, we used Polynomial Curve and Moving Average Combination Projection (PCMACP) model to estimate the future natural gas consumption in China from 2009 to 2015. The new proposed PCMACP model shows more reliable and accurate results: its Mean Absolute Percentage Error (MAPE) is less than those of any previous models within the investigated range. According to the PCMACP model, the average annual growth rate will increase for the next 7 years and the amount of natural gas consumption will reach 171600 million cubic meters in 2015 in China.     

Use of the ‘characteristic function’ for modelling repeatability precision

The ‘characteristic function’ is a two-parameter function relating precision or uncertainty in analytical results to the concentration of the analyte. In previous papers, in this series, it has been shown to provide a good model of precision measured: (a) under reproducibility conditions and (b) under ‘instrumental’ conditions. The present study shows that it is also a valuable model for precision estimated under repeatability conditions. The study data were large sets of duplicated results obtained for the purposes of quality control on typical test materials in routine analysis. As the analytes exhibited concentration ranges encompassing between one and three orders of magnitude, there was ample scope to demonstrate goodness of fit to the function under different circumstances.     

Linear augmented cylindrical wave Green’s function method for perfect nanotubes and nanotubes with regular and point impurities

Nanotubes are giant cage molecules looking like closed hollow cylindrical shells. This review deals with basic principles of the linear augmented cylindrical Green’s function method and its applications to calculation of the electronic structure of perfect nanotubes and those containing substitutional impurities. A major argument for using cylindrical waves to describe nanotubes is that such a choice of the basis set makes it possible to explicitly consider the actual cylindrical geometry of nanotubes, which, in particular, ensures rapid convergence of iterative procedures. A computation technique has been described and the results of calculations of the band structure and densities of states of carbon and boron nitride nanotubes have been reported. Special attention has been paid to the changes in the electronic properties of nanotubes induced by the substitution of nitrogen, boron, or oxygen for C atoms in the carbon nanotubes, as well as to the isoelectronic substitution of P, Sb, or As for the nitrogen and of Al, In, or Ga for the boron in boron nitride nanotubes.     

Computer realization of G. B. Bokii’s idea of taxon separation for the natural classification of minerals

The paper describes G. B. Bokii’s idea of separating the primary classification levels of the mineral world and the results of developing the database containing G. B. Bokii’s decimal symbols.     

Analytical solution to transient inverse heat conduction problem using Green’s function

Journal of Thermal Analysis and Calorimetry - A transient inverse heat conduction problem concerning jet impingement heat transfer has been solved analytically in this paper. Experimentally...     

Contaminant detection in treated water using Optiqua’s MiniLab™ biosensing system: a case study for Bisphenol A

An inhibition assay for detection of Bisphenol A (BPA) in treated water has been developed and validated for the MiniLab? system from Optiqua Technologies. This biosensor-based analytical system can be used for detection of specific contaminants in solution. The system uses an integrated optic Mach-Zehnder interferometer chip that is functionalised with a biochemical interface layer. The sensor chip surface was first coated with aminodextran which formed a hydrophilic layer suitable for further modification. 4,4-bis(4-hydroxyphenyl) valeric acid (BVA), which is a structural analogue of BPA, was then successfully coupled to the aminodextran layer. This surface chemistry was used in a qualitative inhibition assay format for the selective detection of the presence of BPA. The assay was developed and optimised using a polyclonal anti-BPA antibody. Samples from 12 different water matrices of Singapore were spiked with known amounts of BPA and tested with the MiniLab? system. The working range of the BPA inhibition assay is from 0.5 to 5 µg/L. Intra- and inter-assay variations were measured, with calculated relative standard deviation averaging of about 15%. BPA concentrations of the spiked samples were also verified and confirmed with LC-MS. Such functionalised biosensor chip can be reused for more than 200 sample injections over a period longer than 6 months. Developed as a robust, user-friendly and cost-effective system that can be field deployed, the MiniLab? system enables target-specific assays currently only available in the lab to become available in the field.     

Measurement uncertainty in water microbiology may not estimate the laboratory’s precision

It has been proposed that microbiology laboratories introduce a measurement uncertainty for organism counts. Suggested methods of achieving this involve studying replicate counts from subsamples. This will overwhelmingly estimate the natural variation in numbers of organisms present in different subsamples, and the different characteristics of strains of organisms within the species or group (e.g. the coliform bacteria) being counted. Thus any measure of the laboratorys competence, in terms of precision, will be masked. In chemistry there is likely to be much more complete homogeneity of an analyte in a test material and these replicate measures will illustrate whether the laboratory is competent in achieving accurate results.