Purity assignment for peptide certified reference materials by combining qNMR and LC-MS/MS amino acid analysis results: application to angiotensin II

Analytical and Bioanalytical Chemistry - The purity value assignment of metrologically traceable peptide reference standards requires specialized primary methods. Conventionally, amino acid...     

Simultaneous separation of angiotensin and endothelin peptide families by high-performance liquid chromatography: application to the specific radioimmunoassay measurement of angiotensin II or endothelin-1 from tissue

Currently available measurements of endogenous angiotensin II (ANG II) and endothelin-1 (ET-1) concentrations by radioimmunoassay (RIA) lack specificity to ANG II or ET-1. ANG II and ET-1 antibodies cross-react with immuno-reactive angiotensin and endothelin family members, respectively. We have therefore developed an ion-pair reversed-phase high-performance liquid chromatography (HPLC) for simultaneously separating angiotensin and endothelin peptides and enhancing RIA specificity in the measurement of ANG II and ET-1. The developed HPLC separation was applied to canine myocardium extracts; ANG II or ET-1 fractions were collected and quantified by RIA. Elution times for both peptide families, ANG I, ANG II, ANG III, ANG IV, ANG II(4–8), bET-1, ET-1, ET-2 and ET-3 were within 25 min. In normal canine myocardium from the right atrium, right ventricle, left atrium and left ventricle, ANG II concentrations were 39±11, 28±21, 31±11 and 21±8 fmol/g and ET-1 concentrations were 43±16, 42±19, 55±21 and 57±34 fmol/g (mean±SD, N=7), respectively. The combination of HPLC with RIA renders the measurement of ANG II or ET-1 specific and convenient, and saves time. This HPLC separation may be applied to the specific measurement of other immuno-reactive angiotensin and endothelin peptides.     

The peptide hormone angiotensin II: its new functions in tissues and organs

The peptide hormone angiotensin II is well established to play an endocrine role in the regulation of blood pressure, fluid and electrolyte homeostasis. In addition to its hemodynamic function, recent studies have shown that numerous tissues and organs contain their own locally generated angiotensin products (angiotensin II, III, IV and Ang 1-7) and they exhibit their respective activities. Such an intrinsic angiotensin-generating system renders to specific tissue function of our body, frequently via the regulatory mechanism of a paracrine, autocrine or intracrine manner. These tissues and organs include, to name but a few, the brain, bone marrow, adipose, epididymis, carotid body, liver, and pancreas. This local system has been shown to be responsive to various stimuli of physiological and pathophysiological importance. Moreover, the locally generated angiotensin peptides have multiple and novel actions including cell growth, anti-proliferation, apoptosis, reactive oxygen species generation, hormonal secretion, pro-inflammatory, and pro-fibrogenic actions, as well as vasoconstriction and vasodilatation. Notwithstanding the emerging roles of angiotensin II in various tissues and organs, the physiological significance and ultimately the clinical relevance remain largely undefined. Future target for these new functions by making use of specific renin-angiotensin system inhibitors, such as the angiotensin-converting enzyme and angiotensin II receptor blockers either in mono-therapy or in combination, could be of clinical importance. The current review is to focus on some of the new functions arising from the locally formed angiotensin II in tissues and organs, with particular attention to its emerging roles in the liver and the pancreas.     

Metal-based impurities in graphenes: application for electroanalysis

We show here that metallic impurities presented in graphenes prepared from graphite can be usefully employed for electroanalysis. We demonstrate that cumene hydroperoxide electrochemical reduction on graphene containing iron-based impurities provides significantly larger voltammetric currents than the same experiment using iron oxide nanoparticles. This opens doors for turning metallic impurities into potentially useful components of graphene based electrochemical systems.     

Availability of reference materials: COMAR the database for certified reference materials

COMAR is the international database for certified reference materials. A new user-friendly web-based version, COMAR², has been developed by BAM and CONET Consulting AG which will be available in December 2002. The advantages of COMAR² are briefly explained.Presented at the International ILAC/IAF Conference on Accreditation in Global Trade, 23-25 September 2002, Berlin, Germany     

新型生物医用材料: 肽类树枝状大分子及其生物医学应用

肽类树枝状大分子是近年来发展起来的一类新型生物医用高分子材料, 它在具有普通树枝状大分子的特征如规整性、高度支化、表面呈现高密度功能团、尺度为纳米级、通过可控制备可得到单一分子量等之外, 同时还具有类似蛋白一样的球状结构、好的生物相容性、水溶性、耐蛋白酶水解、生物降解等独特的性能. 肽类树枝状大分子的上述特点, 使其在生物医学应用中显示出诱人的前景. 本综述从肽类树枝状大分子的制备出发、详尽介绍了肽类树枝状大分子的功能化及其在疾病诊断和治疗中的应用等方面的研究进展, 籍此推动肽类树枝状大分子在生物医学领域的研究与开发.     

Review of neutron activation analysis in the standardization and study of reference materials, including its application to radionuclide reference materials

Summary Neutron activation analysis (NAA) plays a very important role in the certification of reference materials (RMs) and their characterization, including homogeneity testing. The features of the method are briefly reviewed, particularly aspects relating to its completely independent nuclear basis, its virtual freedom from blank problems, and its capacity for self-verification. This last aspect, arising from the essentially isotopic character of NAA, can be exploited by using different nuclear reactions and induced nuclides, and the possibility of employing two modes, one instrumental (nondestructive), the other radiochemical (destructive). This enables the derivation of essentially independent analytical information and the unique capacity of NAA for self-validation. The application of NAA to quantify natural or man-made radionuclides such as uranium, thorium, ²³⁷Np, ¹²⁹I and ²³⁰Th is discussed, including its advantages over conventional radiometric methods, and its usefulness in providing independent data for nuclides where other confirmatory analyses are impossible, or are only recently becoming available through newer atom counting techniques. Certain additional, prospective uses of NAA in the study of RMs and potential RMs are mentioned, including transmutation reactions, creation of endogenously radiolabelled matrices for production and study of RMs (such as dissolution and leaching tests, use as incorporated radiotracers for chemical recovery correction), and the possibility of molecular activation analysis for speciation.     

Feasibility studies for the preparation and certification of reference materials Part II: mineral oil contaminated waste materials

The 2-year international joint project HYCREF (Contract-No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogenous and stable water-, soil- and waste reference materials contaminated with mineral oil hydrocarbons and to test certify the mineral oil content by gas chromatographic methods. As mineral oil products are important sources for environmental contaminations, appropriate reference materials certified by using the new gas chromatographic methods (soil: ISO/FDIS 16703, waste: prEN 14039 and KW/04, water: ISO 9377-2) are highly needed. Additional to the HYCREF-results presented in part I–mineral contaminated soils–this second paper gives an overview of the feasibility study for the preparation and test certification of three waste reference materials (offshore marine sediment, building material and industrial waste). The following specifications, which had been defined in the project work plan, were reached successfully: uncertainty of the mineral oil content resulting from the certification exercise ≤5% and a between-bottle inhomogeneity of ≤3%. All three materials have been evaluated for long- and short term stability. They contain different levels and types of mineral oil and cover the full application range of ISO/FDIS 16703 and prEN 14039 (100–10,000 mg/kg). The expanded uncertainties U _cert of the three materials are about 6%. In this way, they are comparable to ERM^®-CC015a (U _cert=7.1%, mineral oil in a river sediment) and are suited to close the present gap of commercially available CRM for mineral oil determination in waste.     

Innovative strategies to effectively increase the active-site density of M-N-C materials for electrochemical application

Owning the merits of low-cost, unique electronic and geometric properties, atomically dispersed M-N-C materials have been extensively examined as robust electrocatalysts for many important electrochemical reactions. Nevertheless, it remains a grand synthetic challenge to fabricate such materials with a high concentration of isolated metal active sites, as the formation of metal clusters/nanoparticles seems to be inevitable during the calcination process due to the high surface free energy of single-atom metals. As a result, although M-N-Cs have been successfully tuned to display remarkable activities per metal atomic site, their overall catalytic performances are still unsatisfactory. In this current opinion article, we summarize recent advances in innovative strategies to increase the active-site density of M-N-Cs and also propose the future opportunities and challenges for fostering the practical application of M-N-Cs in electrochemical devices.     

Environmental lead: need for reference materials

The status of the availability and appropriateness of standard reference materials (RMs) currently available for Pb in paint, dust, soil and drinking water is reviewed. The need for RMs which will be most appropriate for environmental Pb analysis in the context of the analytical techniques used, government regulations and health effects, is assessed. Also, the importance of factors such as bioavailability, sample size, homogeneity and composition that should be considered in developing appropriate RMs certified for Pb in paint, dust, soil and drinking water is stressed.     

Operationally defined extraction procedures for soil and sediment analysis: II. Certified reference materials

Single or sequential extraction procedures are often used for soil and sediment studies to determine forms or phases of elements (e.g. ‘bioavailable' forms of elements). The significance of the analytical results is highly dependent on the extraction procedures used, owing to the ‘operationally defined' character of these schemes which requires the adoption of standardized protocols. The first part of the present review discusses the aspects of standardization of leaching and extraction schemes as applied to environmental analysis. This second part focuses on the validation aspects of such procedures and describes the preparation and certification of soil and sediment reference materials certified for their extractable trace element contents, following standardized single and sequential extraction procedures.     

环境监测分析中标准物质的选择及应用

针对分析人员对标准物质概念不清、使用不规范等问题,就环境监测领域标准物质选择和应用方法做了梳理。从标准物质的概念、区分有证和非有证标准物质的方法、标准物质的应用范围及标准物质的使用注意事项等4个方面系统地进行了梳理,重点阐述了有证标准物质和非有证标准物质的概念区别及使用时的误区,为分析人员在实际工作中出具准确数据提供理论依据。     

Application of reference materials in the accurate calibration of the detection efficiency of a low-level gamma-ray spectrometry assembly for environmental samples

A new assembly dedicated for the low-level ψ-ray spectrometric measurements of environmental samples have been installed recently at the International Atomic Energy Agency's Laboratories, Seibersdorf. Calibration of the detection efficiency was performed by a set of 14 IAEA Certified Reference Materials, a standardized solution of¹³⁴Cs, solutions of 2 pure potassium salts, and 2 mixed radionuclide gamma reference standard solutions. These materials, in 1.3 liter Marinelli beakers, were measured by a large HPGe detector. The high precision and accuracy of the calibration procedure is shown by the high significance achieved in the linear fits of the efficiency results, which are traceable to certified and standard reference materials. Small biases between some calibrands were detected. A new corrected result is the 1.37±0.05 Bq/kg activity concentration of¹³⁷Cs in IAEA-A-14 Milk Powder.     

Separation and quantitation of several angiotensin II receptor antagonist drugs in human urine by a SPE-HPLC-DAD method

In this work, an SPE-HPLC method coupled to photodiode array detection was validated in human urine matrix, in order to monitor four antihypertensive angiotensin II receptor antagonist drugs in patients under cardiovascular treatment. For that purpose, experimental design was used. Quantitation was accomplished by the internal standard method. The obtained LOQs were 95, 113, 125, and 85 ng/mL for eprosartan, telmisartan, irbesartan, and valsartan, respectively. The intraday and interday precision and accuracy at four concentration levels in the working range (LOQ-15 microg/mL) were always lower than 11% RSD and 8% relative error. The urine samples proved to be stable during 4 h at room temperature, after three thaw-freeze cycles, and for 2 months at -20 degrees C. No interferences from other endogenous compounds or co-administered drugs were found. The method has been successfully applied to monitor the renal elimination of eprosartan and valsartan during 24 h.     

Reference materials and certified reference materials for spectrometry in Romania

Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed.     

Reference materials and certified reference materials for spectrometry in Romania

Several reference materials (RMs) and certified reference materials (CRMs) are widely used in Romania as measurement standards in different spectrochemical measurements. Among them, single element standard solution certified for their mass concentration play a key role in ensuring the required traceability of results expressed in this measurement unit. A short review of the locally available elemental RMs and CRMs used in atomic spectrometry or in other analytical techniques where aqueous standard solutions are required (usually called RMs or CRMs for spectrometry) is given. The experience of the INM in preparation and certification of such materials is described. Some aspects regarding their use for ensuring the accuracy and for confirmation of the traceability of analytical measurements, especially through calibration and metrological validation of main instrument performances, are discussed.     

Validation of an immunoassay for detection and quantitation of a genetically modified soybean in food and food fractions using reference materials: interlaboratory study

An immunoassay for detection of a specific genetically modified soybean (Roundup-Ready) was validated on dried soybean powder in an interlaboratory study. Different percentages of genetically modified soybeans in nonmodified soybean matrix were evaluated in a blind study. Thirty-eight laboratories from 13 countries participated. The immunoassay was evaluated for 2 endpoints: (1) To give a semiquantitative result, i.e., determination of a given sample above or below a given threshold, or (2) to compute a quantitative result, i.e., percentage of genetically modified soybeans in the sample. Semiquantitative results showed that a given sample which contained <2% genetically modified soybeans was identified as below 2% with a 99% confidence level. Quantitative use of the assay resulted in a repeatability (r) and reproducibility (R) that were computed to be RSDr = 7% and RSDR = 10%, respectively, for a sample containing 2% genetically modified soybeans. Application of this method depends on availability of appropriate reference materials for a specific food matrix. Only matrix-matched reference materials can be used for analysis of food or food fractions.     

Need for food reference materials in Asia

Summary A survey was conducted to determine perception, knowledge, use or application of Food Reference Materials (Food RM) in Asia and to assess individual country needs for these materials. Respondents of the questionnaire came from government institutions, private laboratories, food industries and state universities in 12 countries in Asia involved in food composition data generation. Results showed that only a third of the respondents had been using Food RM in their studies while the remainder were either unaware or not using these materials for logistical reasons or unavailability. The survey revealed emerging interest on the need to establish a Food RM Program in Asia. A common implementation strategy expressed by respondents is the creation of a center, where Food RM can be developed. This center will also be entrusted with the distribution of Food RM and collection, monitoring and evaluation of analytical data. The survey results will help ASIAFOODS in formulating guidelines or planning action regarding the use of Food RM to ensure accurate and dependable food composition data in the Asian region.