Topical Problems in Elemental Analysis of Advanced Ceramic Materials

Selected prominent problems in the analysis of advanced ceramic materials are surveyed. The importance of reliability of results is discussed in the field of elemental trace- and microanalysis in view of its interaction with economy, power of detection, local resolution and speciation selectivity. Particular problems in the analysis of major constituents, trace components and microlocal distributions are based on the striking propertics of ceramics; they are exemplified. Analytical assistance must start from the beginning of the production processing, in the preparation of the powdered base materials. Determination of the stoichiometry requires high accuracy and differentiation of chemical species in bulk and surface analysis of ceramic base powders. Element trace determination by direct instrumental methods requires standard reference materials for calibration; these are currently inavailable in a sufficient variety. For optimum reliability and power of detection, element traces must be prepared in isolated form in a small excitation volume for analysis. A review on the state-of-the-art of wet-chemical combined procedures is presented. Decomposition position procedures are emphasized, due to their risk of contributing severe systematic error. Combustion in elementary fluorine is presented for decomposition of refractory materials. The performance of some direct procedures is discussed. Very efficient methods are available for element trace determinations in ceramic materials, offering high detection power. Several approaches for high-resolution local microanalysis in non-conductive ceramic materials are identified as the most promising development in the analysis of sintered compact ceramic products and devices.     

Measurement of lactate in whole human blood with near-infrared transmission spectroscopy

We have evaluated the potential of near-infrared spectroscopy (NIRS) as a technique for rapid analysis of lactate in whole blood. To test the NIRS technique, a comparison was made with a standard clinical method using whole blood samples taken from five exercising human subjects at three different stage of exercise. To expand lactate concentration within the physiological range, standard additions method was used to generate 45 unique data points. Spectra were collected over the 2050-2400 nm spectral range with a 1 mm optical path length quartz cell. Reference lactate concentrations in the samples were determined by enzymatic measurements. Estimates and calibration of the lactate concentration with NIRS was made using partial least squares (PLS) regression analysis and leave-N-out cross validation on second derivative spectra. Separate calibrations were determined from each of the subject samples and cumulative PRESS was used to determine the number of PLS factors in the final model. The results from the PLS model presented are generated from the five individual calibration coefficient vectors and provided a correlation coefficient of 0.978 and a standard error of cross validation of 0.65 mmol l⁻¹ between the enzymatic assay and the NIRS technique. To study the parameters that impact the spectra baseline and the correlation between the calculated model and the data, referenced measurements of lactate against baseline spectrum were made for each individual. A correlation coefficient of 0.992 and a standard error of cross validation of 0.21 mmol l⁻¹ were found. The results suggest that NIRS may provide a valuable tool to assess physiological status for both research and clinical needs.     

Preparation of VPS and PVD coatings for metallographic and TEM investigations

The aim of the first part of the paper is to give some advice for the faultless metallographic preparation of vacuum plasma sprayed coatings. Several coating/substrate combinations using metals, alloys and ceramics were investigated to derive some general rules. The second part deals with a preparation technique for cross-sections- of physical vapour deposition coatings. This technique was optimized for TiN and Ti(C, N) coatings on hardmetals which were examined in an analytical transmission electron microscope.     

Analysis of volatile compounds of rosemary honey. Comparison of different extraction techniques

Summary The analysis of the volatile fraction from honey requires the sugar matrix to be separated prior to the analysis by GC-MS. In this study, three extraction techniques, simultaneous extraction-distillation, liquid-liquid extraction and solid-phase extraction, were compared to the extraction of the volatile compounds of a rosemary honey. Analysis of these fractions by gas chromatography—mass spectrometry enabled the tentative identification of up to 122 volatile compounds (alcohols, ketones, aldehydes, acids, esters, terpenes, hydrocarbons, phenol, furan and pyran compounds). SDE extracts were rich in terpenes and esters, while the other two techniques avoided the formation of artefacts due to heating the sample.     

Microanalysis of Volatile Organic Compounds (VOCs) in Water Samples – Methods and Instruments

Volatile organic compounds (VOCs), due to their toxicity and persistence in the environment, are particularly important pollutants. Some of these compounds are mutagens, teratogens or carcinogens, while others are responsible for the degradation of organoleptic parameters such as taste and odour of water. This review focuses on a number of key procedural steps in the analysis of volatile organic compounds (VOCs) in water samples. A wide spectrum of techniques for the isolation and preconcentration of the aforementioned pollutants for trace organic analysis by gas chromatography are presented and discussed. The advantages and disadvantages of these techniques are discussed and novel developments are also taken into consideration.     

Time-dependent mixing and demixing processes in binary lipid monolayers studied by mixed and separate spreading using film pressure and film potential measurements

Using both spreading techniques — mixed spreading and separate spreading- and, simultaneously, film pressure and film potential measurements, the mixing behavior of the following five binary systems was investigated and compared: 1) system 1,2-dilauroyl-phosphatidylethanolamine/cholesterol; 2) system 1,2-dimyristoyl-phosphatidylethanolamine/cholesterol; 3) system 1,2-dipalmitoyl-phosphatidylethanolamine/cholesterol; 4) system Na-eicosyl sulphate/hexadecanol; 5) system phosphatidic acid/1,2-dimyristoyl-phosphatidylethanolamine.Analyzing the time and concentration dependence of the /a isotherms and v/a isotherms (^s = film pressure, v ^s potential,a=average area per molecule in mixed films in the monolayers) of the binary monolayers it can be concluded that the components of the binary systems 1–4 are complete miscible in the monolayers. On the other hand the components of the system 5 are probably partially miscible only.     

高纯氧化钇中镧、铈、钐、铝、铅和铜的电感耦合等离子体原子发射光谱法测定

本文以纯Y_2O_3中杂质元素的ICP-AES测定为例,研究用数值微分技术解决光谱干扰同题。结果表明,导数光谱法不仅可以有效地消除来自基体的光谱干扰,还能减小谱线干扰对检测能力的影响。当分析物浓度较低时,导数光谱法的加入回收率明显优于离峰分析法,多数情况下也优于在峰法校正光谱干扰时的回收率。     

Numerical solution of minimax problems of optimal control,part 1

This paper contains general transformation techniques useful to convert minimax problems of optimal control into the Mayer-Bolza problem of the calculus of variations [Problem (P)]. We consider two types of minimax problems: minimax problems of Type (Q), in which the minimax function depends on the state and does not depend on the control; and minimax problems of Type (R), in which the minimax function depends on both the state and the control. Both Problem (Q) and Problem (R) can be reduced to Problem (P).For Problem (Q), we exploit the analogy with a bounded-state problem in combination with a transformation of the Jacobson type. This requires the proper augmentation of the state vectorx(t), the control vectoru(t), and the parameter vector , as well as the proper augmentation of the constraining relations. As a result of the transformation, the unknown minimax value of the performance index becomes a component of the parameter vector being optimized.For Problem (R), we exploit the analogy with a bounded-control problem in combination with a transformation of the Valentine type. This requires the proper augmentation of the control vectoru(t) and the parameter vector , as well as the proper augmentation of the constraining relations. As a result of the transformation, the unknown minimax value of the performance index becomes a component of the parameter vector being optimized.In a subsequent paper (Part 2), the transformation techniques presented here are employed in conjunction with the sequential gradient-restoration algorithm for solving optimal control problems on a digital computer; both the single-subarc approach and the multiple-subarc approach are discussed.This research was supported by the National Science Foundation, Grant No. ENG-79-18667, and by Wright-Patterson Air Force Base, Contract No. F33615-80-C3000. This paper is a condensation of the investigations reported in Refs. 1–7. The authors are indebted to E. M. Coker and E. M. Sims for analytical and computational assistance.     

Sol-gel approach to in situ creation of high pH-resistant surface-bonded organic-inorganic hybrid zirconia coating for capillary microextraction (in-tube SPME)

A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME).