A GUM-compliant uncertainty budget for the analysis of total carbon dioxide (TCO<Subscript>2</Subscript>) in equine plasma

Samples of plasma from chosen horses are collected prior to racing for the analysis of total carbon dioxide (TCO₂). Five or six (dependent on jurisdiction) tubes of blood are taken as required for a screen, followed (if positive) by confirmation (two tubes in quadruplicate) and, further confirmation (two tubes in quadruplicate) at a second referee laboratory. The threshold limit prescribed by the rules of racing is an amount concentration of 36.0 mM, with further action ensuing if the reported concentration is greater than 37.2 mM. Using QC data and an analysis of the measurement procedure, the combined standard measurement uncertainty of a measurement result was estimated to be 0.22 mM. This leads to a conclusion that the odds of incorrectly deciding that a sample at the threshold limit exceeded the action concentration, are 13 000 000:1 against. The combined standard measurement uncertainty could be reduced to 0.20 mM by combining results from the first and referee laboratories. An allowance for uncertainty of measurement of 1.0 mM is proposed, which leads to odds of 185 000:1 against concluding a sample is over the threshold limit when, in fact, it is not.     

Pediatric ocular nanomedicines:Challenges and opportunities

Challenges and opportunities to development of ocular drug delivery systems and nanomedicines for pediatric patients are reviewed.     

Improvements of an oscillatory squeezing flow rheometer for small elasticity measurements of liquids

Dilute dispersions and polymer solutions used as functional fluids or operation fluids are required to be controlled in an extremely high quality level in the semiconductor industry or MEMS (Micro Mechanical Electric System) devices, such as inkjet print heads and micro pumps. Many of the quality items depend on microscopic state of dispersion or solution stem from mutual interactions among the dispersed particles and solved polymers; hence, close investigations of these complex interactions are of great concern for developments of highly functional fluids and micro fluidic devices. Here, some great improvements are presented on a random oscillatory squeezing flow rheometer to detect subtle rheological properties arise as results of interactions between micro solid particles dispersed in liquids. To detect subtle elasticity within fundamentally viscous liquids, very small phase difference from the viscous response has to be measured, and for this reason effects from three major sources (sensor nonlinearity, nonlinear squeeze flow response, and instrument compliance) that give phase errors and noises as well as fluid inertia are completely compensated by data processing, achieving sensitivity for subtle dynamic modulus G to the extent of G/G 0.001. As examples of the dilute dispersions, water dispersions of monodisperse acrylic latex were measured and detections of dynamic modulus G of 10^–3 Pa at 100 Hz were demonstrated.     

On the assessment of compliance with legal limits Part 1: signal and concentration domains

Taking into account the uncertainty of measurement when assessing compliance of a given sample with compositional specifications or statutory limits is an open question. Rigorous assessment should be performed within the signal domain, and by considering both α and β errors. Working within the concentration domain through a calibration function, which is affected by additional experimental uncertainties, involves a different degree of uncertainty and can sometimes lead to unreliable verdicts. The matter is discussed, and illustrated with the aid of some worked examples, each using multiple simulated data sets, obtained by adding an arbitrarily chosen Gaussian noise to representative response/concentration functional relationships. Received: 12 October 2000 Accepted: 12 July 2001     

On the Kinetics of Polymer Crystallization in Opposite-Nozzle Flow

The present work was encouraged by the successes obtained previously in this laboratory with short-term shearing experiments on slightly undercooled melts of i-PP: post-shearing lamellar growth on (inconspicuous) thread-like precursors. For the present purpose (evaluation of the influence of extensional flow) the pioneering work by Mackley and Keller is taken as the point of departure. Our own machine of the same type has been adapted for creep experiments (adjustment to steady flow in fractions of the time needed in the original machine). The range of extension rates, where a transition takes place from a mere multiplication of the number of nuclei to the induction of highly oriented structures, appears to be quite narrow in undercooled i-PP melts. In the range of high extension rates (≅50 s⁻¹ ) the critical time for the formation of an oriented structure could not be measured because of its shortness (less than 0.2 s). It turns out that the flow pattern in the opposite-nozzle machine is far from ideal. A proposal had to be made for a redesign. In spite of the preliminary nature of some of our results, several interesting insights should not be “bottled up”. First of all, there is the usefulness of creep flow (because of its fast transition into steady state, after an almost instantaneous compliance). Secondly, there is the quite unexpected ineffectiveness of lower stretching rates for the formation of oriented structures. Thirdly, there is the overwhelming influence of a change of the geometry: the provisional introduction of trumpet-shaped (nearly hyperbolic) entrance regions to the nozzles caused a remarkable broadening of the birefringent zone, which was previously observed as a very thin “string” connecting the nozzles. Finally, the almost certain usefulness of the revised machine for other (sometimes purely rheological) purposes, e.g., for steady-state flow birefringence measurements in extensional flow should be mentioned. Received: 22 June 1999 Accepted: 28 September 2000     

Coupling coefficients of glass/epoxy laminates under off-axis tensile conditions: Experimental verification

A comprehensive experimental study on the coupling coefficients of unidirectional (UD) and woven fabric glass/epoxy laminates under off-axis tensile loading was conducted in comparison with the theoretical prediction. The capability of the off-axis test to evaluate the elastic constants in the loading direction was reported. Four coupling coefficients were obtained from tests and discussed in comparison with the theoretical prediction. A further comparison of coupling compliance coefficients in compliance matrix was made in order to generalize the influence of off-axis angle on the compliance coefficients. The theoretical prediction agreed well with the experimental data. It is shown that non-monotonic and symmetry phenomena can be observed in the curves of the coupling and compliance coefficients. The results of this experimental study provide a data base of the coupling coefficients of glass/epoxy laminates for engineering application.     

The effect of instrument compliance on dynamic rheological measurements

The effect of instrument compliance on ERD and forced oscillation experiments is examined. A relationship for the determination of correct experimental conditions in ERD measurements is presented. It is concluded that the applicability of shear compliance corrections is doubtful whenever their magnitude is over 50% of the measured quantity and |G ^*| > 5 × 10⁵ Pa. Compressive compliance is found to have a negligible effect in all practical cases. Torsional compliance can be important in oscillatory experiments when sample torsional stiffness is high relative to instrument stiffness. Numerical values for Rheometrics equipment are used throughout the discussion.     

Compliance decision criteria—problems encountered and actions taken in the EU and Codex

It is now recognised that there is an intimate relationship between the final analytical result and the sampling, the measurement uncertainty and the recovery factor used to obtain that result. Within the food sector in the EU this was identified by the SCOOP Task 9.1 “Preparation Of A Working Document In Support Of The Uniform Interpretation Of Legislative Standards And The Laboratory Quality Standards Prescribed Under Directive 93/99/EEC”. The recommendations from this Report have been accepted in the Food Contaminants and the Undesirable Substances in Feed Sectors. These are given in the SANCO document “Report To The Standing Committee On The Food Chain And Animal Health On The Relationship Between Analytical Results, The Measurement Uncertainty, Recovery Factors And The Provisions In EU Food And Feed Legislation With Particular Focus On The Community Legislation Concerning: (A): Contaminants In Food (Council Regulation (EEC) No 315/93 of 8 February 1993 Laying Down Community Procedures For Contaminants In Food), and (B): Undesirable Substances In Feed (Directive 2002/32/EC Of The European Parliament And Of The Council Of 7 May 2002 On Undesirable Substances In Animal Feed).” Similar considerations were identified in the Codex Alimentations Commission where the guidelines “The Use Of Analytical Results: Sampling, Relationship Between The Analytical Results, The Measurement Uncertainty, Recovery Factors And The Provisions In Codex Standards” are being progressed through the Codex system. Both of these Reports stress that before deciding whether a sample is in compliance with a legislative limit the uncertainty should be deducted and the results corrected for recovery. Thus that there is a difference between the legal specification and enforcement limit will be stressed and that this should be appreciated when specifications are being set. The rationale behind the Reports is described. Presented at AOAC Europe/Eurachem Symposium March 2005, Brussels, Belgium

---

     

Synthesis and electrical,rheological and thermal characterization of conductive polyurethane

This work studies the electrical, rheological, and thermal characteristics for polyurethane (PU) capped with tetraaniline as a new material, tetraaniline-containing poly(urethane–urea) (TAPU). The conductivities can be increased from less than 10⁻¹⁰ S/cm for pure PU to 10⁻⁴ S/cm for TAPU, independently of the length of the soft segment in the TAPU backbone chain. The tensile strength and modulus are increased when PU is copolymerized with tetraaniline. The viscoelastic creep can be effectively simulated using a Burgers model. Additionally, TAPU has higher viscosity, higher retardation time, and lower compliance J ₁ than regular PU. Restated, TAPU exhibits less elastic but superior permanent deformation than PU because tetraaniline functions as a chain holder. The thermogravimetric analytic (TGA) results reveal that TAPU has lower T _d, smaller T _mw1 and T _mw2, and higher char yield because the dehydration of the urea-containing polymer produces a thin layer from a nitrogen compound on the polymer’s surface, which insulates the underlying polymer from heat and oxygen.