About acceptance and rejection zones as defined in the EURACHEM/CITAC Guide (2007) “Use of uncertainty information in compliance assessment”

Considering measurement uncertainty is mandatory in assessing conformance to legal or compositional limits, and specific guidelines are available issued by ASME, ISO and Eurachem/CITAC. However, differences between ISO and EURACHEM/CITAC wordings could induce some perplexities in the most careful readers. Possible problems arise from considering that, before performing a test, it should be decided whether it is to be a test for conformity or a test for non-conformity. This choice could perhaps require some renaming of acceptance/rejection zones as defined in the EURACHEM/CITAC Guide. A tentative solution is discussed in this contribution.     

Comments to EURACHEM/CITAC guide “Measurement uncertainty arising from sampling”

The EURACHEM/CITAC Guide “Measurement uncertainty arising from sampling” deals with the design and analysis of experiments for the evaluation of the sampling and analytical standard deviation when a defined sampling and analytical method is used for the determination of the concentration, expressed as mass fraction (mg/kg), of an analyte in a specified material. The Guide recommends reporting the relative expanded uncertainty and using it directly, i.e. it implicitly assumes that the standard deviation is proportional to the mass fraction even in case the experimental data do not support this assumption. Example A1 (and some of the other examples of the Guide) demonstrates that this can result in extreme levels of underestimation or overestimation of the uncertainty of measurement results. Hence, such recommendations should be avoided!     

Reply to comments on EURACHEM/CITAC guide “Measurement uncertainty arising from sampling”

The Eurachem/CITAC Guide on ‘Measurement uncertainty arising from sampling’ describes a number of methods and approaches that can be used for the estimation of this uncertainty. A recent comment upon this Guide by Wilrich questions the expression of the measurement uncertainty in a form that is relative to the concentration, rather than just as an absolute number (i.e. as relative expanded uncertainty rather than expanded uncertainty), in one of the worked examples. This reply argues that the measurement results from the ‘duplicate’ method cannot reliably distinguish between constant standard deviation and constant relative standard deviation over the range observed in the example and that the most appropriate model must accordingly rely on prior knowledge. Since extensive prior knowledge indicates that the precision of sampling and of chemical analysis both tend to increase as a function of concentration, the body of the Guide recommends expression as a relative standard deviation. It is acknowledged that this assumption should be restated with the results of the worked examples as well as in its current position in the main body of the text, in a future edition of the Guide.     

Quality in (analytical) R&D – ideas for the next step after EURACHEM/CITAC Guide 2

 The EURACHEM/CITAC Guide 2 is an important step towards the establishment of a quality assurance system in analytical research and development. But it is only the first step because it focuses on the metrological characteristics. In addition to Guide 2 there should be a supplementary guide providing assistance for effective and quality-orientated management of research groups.     

On the use of the ‘uncertainty budget’ to detect dominant terms in the evaluation of measurement uncertainty

In the evaluation of measurement uncertainty, the uncertainty budget is usually used to identify dominant terms that contribute to the uncertainty of the output estimate. Although a feature of the GUF method, it is also recommended as a qualitative tool in MCM by using ‘nonlinear’ equivalents of uncertainty contributions and sensitivity coefficients. In this paper, the use of ‘linear’ and ‘nonlinear’ parameters is discussed. It is shown that when and only when the standard uncertainty of the output estimate is nearly equal to the square root of the sum of the squares of the individual uncertainty contributions, will the latter be a reliable tool to detect the degree of contribution of each input quantity to the measurand uncertainty.     

Status of uncertainty assessment in k 0-NAA measurement: anything still missing?

Several approaches to quantifying measurement uncertainty in k ₀-based neutron activation analysis (k ₀-NAA) are reviewed, comprising the original approach, the spreadsheet approach, the dedicated computer program involving analytical calculations and the two k ₀-NAA programs available on the market. Two imperfectness in the dedicated programs are identified, their impact assessed and possible improvements presented for a concrete experimental situation. The status of uncertainty assessment in k ₀-NAA is discussed and steps for improvement are recommended. It is concluded that the present magnitude of measurement uncertainty should further be improved by making additional efforts in reducing uncertainties of the relevant nuclear constants used.     

Use of pollution indices and ecological risk in the assessment of contamination from chemical elements in soils and sediments – Practical aspects

This paper presents a discussion involving practical aspects of applying contamination indices and ecological risk factors derived from chemical elements in the environmental assessment of soils and sediments. The single and integrated indices: Geoaccumulation index (I_geo), Enrichment factor (EF), Contamination factor (CF), Pollution Index (PI), Ecological risk factor (E_ir), Pollution Load Index (PLI), Degree of contamination (C_deg), Modified Contamination Factor (mC_deg), and potential ecological risk index (PERI) were discussed, and some applications were presented didactically. The analytical care needed to obtain reliable indices with the studied ecosystem is also evidenced. In addition, the advantages and limitations of the use of these indices are presented.     

Evaluation of “method uncertainty” in the calibration of piston pipettes (micropipettes) using the gravimetric method in accordance with the procedure of ISO 8655-6

The gravimetric method specified by ISO 8655-6 is a standard method for calibrating piston pipettes (micropipettes). The quality of the calibration can be assessed by uncertainty evaluation, the procedure for which is described in ISO/Technical Report (TR) 20461. However, the existence of “method uncertainty” due to ambiguity in the calibration operation, which is not described in the TR, has been found in various experiments, such as the interlaboratory comparison of CCM.FF-K4.2.2011. In this report, the “method standard uncertainty” is quantified as exp(?4.51 + 0.36 ln(V ^nom/μL) + 0.05{ln(V ^nom/μL)}²) μL for a nominal volume, V ^nom, in the range from 2 μL to 10000 μL. Furthermore, the reported values in an interlaboratory comparison are confirmed to be consistent using the quantified method standard uncertainty.     

Use of Silicon Substituents in the Syntheses of Natural and Non-natural Molecules

Trimethylsilyl groups have been used in our research as a director as well as a bulky and lipophilic group in our quest for natural and non-natural molecules.     

Use of the Mass Spectrum–Compound Fragment Composition Database in the Determination of the Structure of Organic Compounds

A mass spectral database in which structural formulas are presented as nonisomorphic connected k-vertex fragments (2 k 7) is used for identifying the structure of organic compounds. It is shown with the example of a test sample of 13000 mass spectra of various organic compounds that up to half the fragments of an unknown analyte can be identified in 50% of cases. Relationships between the correctly and erroneously identified data are given.     

Use of D–T-produced fast neutrons for in vivo body composition analysis: a reference method for nutritional assessment in the elderly

Body composition has become the main outcome of many nutritional intervention studies including osteoporosis, malnutrition, obesity, AIDS, and aging. Traditional indirect body composition methods developed with healthy young adults do not apply to the elderly or diseased. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. Non-bone phosphorus for muscle is measured by the ³¹P(n,)²⁸Al reaction, and nitrogen for protein via the ¹⁴N(n,2n)¹³N fast neutron reaction. Inelastic neutron scattering is used to measure total body carbon and oxygen. Body fat is derived from carbon after correcting for contributions from protein, bone, and glycogen. Carbon-to-oxygen ratio (C/O) is used to measure the distribution of fat and lean tissue in the body and to monitor small changes of lean mass. A sealed, D–T neutron generator is used for the production of fast neutrons. Carbon and oxygen mass and their ratio are measured in vivo at a radiation exposure of less than 0.06 mSv. Gamma-ray spectra are collected using large BGO detectors and analyzed for the 4.43 MeV state of carbon and 6.13 MeV state of oxygen, simultaneously with the irradiation. P and N analysis by delayed fast neutron activation is performed by transferring the patient to a shielded room equipped with an array of NaI(Tl) detectors. A combination of measurements makes possible the assessment of the quality of fat-free mass. The neutron generator system is used to evaluate the efficacy of new treatments, to study mechanisms of lean tissue depletion with aging, and to investigate methods for preserving function and quality of life in the elderly. It is also used as a reference method for the validation of portable instruments of nutritional assessment.     

Estimation of the uncertainty components associated with the measurement of radionuclides in air filters using γ-ray spectrometry

This paper discusses and assesses the major sources of uncertainty arising in measurement of radionuclide activity concentrations in air. Besides counting statistics, the main contributors to the overall uncertainty of the activity concentration of long-lived radionuclides are the heterogeneities of the calibration source and the test samples (approximately 4%). In addition, in the case of radionuclides with half-lives of the order of days or shorter, a significant uncertainty results from the variability of the source term because the peak concentration of the radionuclide might occur either at the beginning or at the end of the sampling period. For¹³¹I (T_1/28 days), for instance, the relative standard uncertainty was estimated as 17% owing to this effect. In addition, the uncertainty introduced by the software used for evaluation of the -ray spectra is discussed. Details of the uncertainty components, including their assessed probability distributions and degrees of freedom, and the conversion into standard uncertainties are reported in this paper, following the ISO Guide to the expression of uncertainty in measurement. A standard form for documenting and reporting the uncertainty budged is proposed and illustrated with an example.     

Use of Diphenyliodonium Bromide in the Synthesis of Some N-Phenyl α-Amino Acids

The N-phenyl methyl esters 4 of glycine, alanine, valine, leucine, isoleucine, phenylalanine, methionine, proline, serine, threonine, tyrosine, aspartic acid, and glutamic acid have been synthesized in good to excellent yields using diphenyliodonium bromide, AgNO₃, and a catalytic amount of CuBr starting from the relevant amino acid ester. The chiral integrity of the amino acids 5 was maintained during these reactions, which were confirmed by the synthesis of dipeptide for each N-phenyl amino acid. The structures of the new compounds were confirmed by the analysis of their IR, ¹H, and ¹³C NMR spectra in addition to CHN microanalysis or high-resolution mass spectrometry for the new N-phenyl amino acids 5 and the esters 4.     

Use of HPLC in the Determination of the Molar Absorptivity of 4��-Geranyloxyferulic Acid and Boropinic Acid

Natural prenyloxycinnamic acids were shown to exert in vitro and in vivo remarkable and valuable anti-cancer and anti-inflammatory effects. Among these, 4??-geranyloxyferulic acid [3-(4??-geranyloxy-3??-methoxyphenyl)-2-trans-propenoic acid] was discovered as an efficient orally active chemopreventive agent of several types of cancer, and its structural analogue boropinic acid was shown to exert a valuable inhibitory effect both in vitro and in vivo against the growth of Helicobacter pylori. As a continuation of our chemical, chemico-physical, and pharmacological studies on these secondary metabolites, we report herein the comparison between traditional UV/Vis assays and HPLC?CDAD methods for the determination of the molar absorptivity coefficient of 4??-geranyloxyferulic acid (?? ₃₁₀ = 12,950 and ?? ₂₈₈ = 11,910 L mol^?1 cm^?1) and boropinic acid (?? ₃₁₀ = 13,510 and ?? ₂₈₈ = 12,350 L mol^?1 cm^?1). Ferulic acid was merely used as a reference standard to test the possibility of the application of these two assays to the oxyprenylated compounds. The data reported in the present study will represent an essential aid for future studies aimed to better define the pharmacological profile and the mechanism of action of these compounds and are an important starting point to evaluate other natural products where standard powders are not available.     

Facile Formation of Ytterbium Diiodide and Its Use in the Synthesis of Allyl Selenides

Ytterbium metal reacts with iodine to generate ytterbium diiodide directly,which can react with diselenides to form ytterbium selenolates(RSeYbI2).These species reacted smoothly with allyl bromide to give allylselenides in moderato to good yields under neutral conditions.     

Use of Capillary Electrophoresis in the Study of Interaction between dsDNA and Drug Molecules

The advantages of berberine such as the anticancer1, antiinflammatory2 and no side effects of camptothecin1, have promoted the research in the mechanism of berberine with macrobiomolecules. In general, three different points of view have been presented on…     

Studies on Tripolycyanamide Formaldehyde Resin-Pd Complex and Its Use in the Synthesis of the Branch of Paclitaxel

A novel method was developed to prepare the branch of paclitaxel using 2,4-dichlorophenylaldehyde as the starting material.The branch was synthesized through condensation, cydoaddltion and catalyzing hydrogenation of dichlorophenyl intermediate. Tripolycyanamide formaldehyde resin-Pd complex as hydrogenation catalyst has been studied. The influence of temperature and N/Pd atomic ratio of the catalyst on the effect of catalytic hydrogenation was investigated and the optimum conditious were found. Because of the mild cyclization reaction condition, convenient asymmetric resolution operation and high yield, the synthetic route was practical.     

The Use of Bone Substitutes in the Treatment of Bone Defects – the Clinical View and History

Summary: Bone has the ability to regenerate and remodel itself. In the clinic circumstances appear when bone defects do not heal spontaneously. These situations frequently result from trauma, congenital abnormities, infection or tumor resection. Hence, filling of the resulting defect by bone transplantation is a common practise with an increasing value in the re-establishment of the musculoskeletal system to promote bone healing. Since decades, efforts have been put to improve the effectiveness of bone substitutes. Conventional approaches with the use of ivory, animal and also human bone were not satisfactory. Negative effects like allergic reactions, rejection reactions, inflammations and other problems occurred. These led to implant failure, non union and amputation, to only mention a few. The introduction of bone banks and the development of standards in bone transplantation brought up the false hope to find a final solution for the treatment of bone loss. Disease transmissions (HIV) by allografts caused critical discussions. Despite all efforts, transplantation of autogenous cancellous bone is still the “gold standard” to induce bone healing. However, autografts are only limited available and are accompanied with high morbidity and mortality during the harvest. The problems associated with autologous and allogenous bone grafts promoted the development of multiple organic and inorganic bone substitutes. Well established substitutes at the present are demineralised bone matrix (DBM), composites and calcium phosphates (hydroxyl apatite and tri-calcium phosphate). These osteoconductive substances have shown to improve new bone formation. Nevertheless, clinical application of these materials is merely successful in a good bony environment but does not induce large progress in critical bone defects.     

“Conjugate” Substitution of Hydrogen in the Methyl Group of Pentabromotoluene in the Presence of Strong Bases

The reactions of pentabromotoluene with i-PrONa or t-BuONa in pyridine give N-(pentabromobenzyl)pyridinium bromide and a mixture of isomeric tetrabromotoluenes. In the presence of bromine or carbon tetrabromide, the reductive debromination is blocked, and the reactions involve exclusively substitution of hydrogen in the methyl group of pentabromotoluene by the pyridinium residue.     

Use of polyethylene glycol in the process of sol–gel encapsulation of Burkholderia cepacia lipase

Lipases from Burkholderia cepacia were encapsulated using polyethylene glycol (PEG, M _w 1500) at various concentrations (0.5–3.0 %, w/v) as an additive during the sol–gel immobilisation process. Matrixes immobilized in the presence and absences of additives were characterized by thermal analysis [thermogravimetric (TG) and differential scanning calorimetry (DSC)], scanning electron microscopy (SEM), enzymatic activity, and total activity recovery yield (Ya). The addition of PEG increased the activity values, with Ya just above 1.0 % (w/v) in the presence of PEG. The additional of 1.0 % (w/v) PEG increased enzyme activity from 33.98 to 89.91 U g^?1 and the values of recovery yield were 43.0–91.4 %, compared to values of the samples without PEG. PEG enhanced the thermal stability of the matrix structure in the temperature range 50–200 °C, as confirmed by TG and DSC analyses. This was influenced by the presence of water bound to the matrix. The SEM micrographs clearly showed an increase in the number of deposits on the material surface, producing matrices with greater porosity.