CRMs for quality control of determinations of chemical forms of elements in support to EU legislation

The concern for the control of toxic chemical forms of elements in the environment is reflected by an increasing number of analyses performed by research and routine laboratories. The European Commission has recognised the need to include some of these species in the list of dangerous substances to be monitored, e.g. in the marine environment or in groundwater. However, in most cases, the specifications are far from being sufficient in respect to the chemical forms of the element to be determined. Furthermore, these determinations are in most cases based on multi-step analytical techniques which are often prone to errors (e.g. at the extraction, derivatization or separation steps). Certified reference materials (CRMs) certified for their content in chemical forms of elements are, therefore, necessary to ensure the accuracy of these measurements and hence the respect of the regulations. However, the lack of CRMs for speciation analysis hampers the quality control of determinations which in turn leads to an incomparability of data produced; so far the number of CRMs produced by international organisations, e.g. NIST (USA), NIES (Japan), NRCC (Canada) and BCR (Belgium), is very limited and concerns mainly compounds such as e.g. methyl-mercury and butyltin compounds in biological matrices or sediments. The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has started a series of projects for the improvement of speciation analysis in environmental matrices, the final aim of which being the production of a variety of environmental CRMs. The existing EU legislation involving chemical forms of elements is presented, the requirements for the preparation of CRMs for speciation analysis are discussed and an update of the most recent CRMs produced within the Standards, Measurements and Testing Programme (SM&T) is given.     

Multielement analysis with ICP-AES-possibilities for quality control with CRMs

Summary An analysis using Certified Reference Materials (CRMs) together with routine samples is by far the best approach for quality control in multielement analysis of environmental samples. The selection of the correct CRM is thus the first important step for all reliable analysis. The chosen material should have a similar matrix, similar concentration of the element(s) of interest and a sufficient number of well-certified elements. For the analysis of samples from the Environmental Specimen Bank only a few CRMs could be successfully used. These were analyzed for a considerable period of time, together with the routine samples for quality control. The results of these analyses were compared with the certified values.     

Preparation of liquid milk for proficiency test and internal quality control for chemical elements in food

Laboratories dealing with the analysis of food of animal origin have to face the shortage of both appropriate certified reference materials and pertinent proficiency tests (PTs). Therefore, internal quality control (IQC) materials have to be prepared in-house. The combination matrix/analytes/concentration, as well as the physical state, is a key issue. The European Union Reference Laboratory for Chemical Elements in Food of Animal Origin (EURL-CEFAO), within its activity as PT provider, has set a procedure to prepare test items of liquid milk spiked with arsenic, cadmium and lead at adequate values of concentration. This work describes in detail the steps of this procedure. Homogeneity and stability of the PT test items thus prepared were evaluated by the EURL-CEFAO using a sensitive and accurate method accredited according to ISO/IEC 17025. The analyte concentrations in spiked milk were found stable up to 18 months which is of particular interest for cadmium due to the low value of spiking (roughly 5 μg/kg). The outcome proves that the procedure used to prepare liquid milk spiked with chemical elements is suitable to produce in-house reference materials stable enough for analytical purposes. Furthermore, this procedure is easy to perform and can be applied by routine laboratories to produce samples for their IQC.     

Certified reference materials for the quality control of EDTA- and acetic acid-extractable contents of trace elements in sewage sludge amended soils (CRMs 483 and 484)

 The ecotoxicity and mobility of trace elements in soils are often evaluated through analytical results resulting from operationally-defined determinations (single and sequential extractions), e.g. based on EDTA, acetic acid etc. extractions. The significance and comparability of these results is highly dependent on the procedures used (standardized protocols or standards adopted by international bodies) and their quality control relies on the availability of reference materials certified following these strictly applied procedures. Recognizing the need to harmonize some of the extraction schemes currently used for soil analysis, the Measurements and Testing Programme (formerly BCR) has organized a series of interlaboratory studies, the first aim of which was to evaluate EDTA- and acetic acid-extraction procedures and the second objective was to certify reference materials for their extractable trace element contents. Two sewage amended soils have been prepared for this purpose, originating respectively from Scotland and Catalonia. This paper describes the preparation, homogeneity and stability studies, and gives an overview of the certification campaign. Received: 6 May 1996/Revised: 14 June 1996/Accepted: 27 June 1996     

Certified reference materials (CRMs 398 and 399) for the quality control of major element determination in freshwater

Analyses of freshwater are routinely performed by a number of organisations to monitor the levels of major elements. In order to improve and control the quality of such determinations, the Community Bureau of Reference (BCR) has organised a certification campaign to produce two reference materials (CRM 398, low element content and CRM 399, high element content) certified for their contents of Al, Ca, Cl, Fe, Mg, Mn, K, Na, P and S. These materials were carefully prepared (addition of the elements mentioned in the form of ammonium salts or nitrates to silica free deionised water) and their homogeneity and long term stability were verified. This paper presents the certification work performed.     

Quality control with CRMs for trace element determination in candidate reference materials

Summary Three soil samples and five candidate materials of biological origin (bovine muscle, bovine kidney, bovine blood, rye flour and wheat flour) and one already certified RM (Bovine Liver, 12-02-01) were analyzed for their contents of Cd, Cu, Cr, Pb and Zn. Pressure digestion with nitric acid in PTFE (at 180°C) and quartz (at 290°C) vessels was used for sample decomposition. The measurements were made by graphite furnance atomic absorption spectrometry (ET-AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) and square wave voltammetry. The accuracy of analysis has been checked by simultaneous analyses of six similar CRMs. An excellent agreement between the found and certified values is illustrated by highly significant correlations.     

Role of NAA in the characterization of sampling behaviors of multiple elements in CRMs

Taking the advantage of the high precision and accuracy of neutron activation analysis (NAA), sampling constants have been determined for multielements in several international and Chinese reference materials. The suggested technique may be used for finding elements in existing CRMs qualified for quality control (QC) of small size samples (several mg or less), and characterizing sampling behaviors of multielements in new CRMs specifically made for QC of microanalysis.     

The application of oscillating chemical reactions to analytical determinations

Oscillating chemical reactions, which are far from equilibrium, are extremely sensitive to certain species and may provide new analytical methods using the regular oscillations as well as the non-equilibrium stationary state after system bifurcation. This review of their application to analytical chemistry from 2005 to 2012 includes other appropriate references. Both organic and inorganic analytes are included.     

Methodology in internal quality control of chemical analysis

Internal quality control (IQC) is an essential feature of routine analysis, serving to ensure that the uncertainty of results found during the validation of a procedure is maintained over long periods of time. The primary method of IQC is to analyse a surrogate material alongside the test materials in every run of analysis and thus address run-to-run precision (a subset of VIM3-defined ‘intermediate conditions’). This ‘control material’ must be as similar as practicable in composition to the routine test materials, although there are always some differences. Results from the control material (control values) are plotted on a control chart, and out-of-control results have to be investigated and problems rectified. Considerable care is needed in obtaining correct values of the parameters for determining statistical control limits, and these can be adequately estimated only during routine use of the analytical procedure. In contrast, target control limits have to be set on a fitness-for-purpose basis and are necessarily wider that statistical control limits. An additional type of internal quality control can be executed by the analysis of duplicate test portions of some of the actual test samples. This provides a realistic dispersion, but addresses only repeatability precision. A further complication of duplication is that the precision of results typically varies with concentration of the analyte.     

Validation and quality control of methylmercury determinations by means of capillary electrophoresis

Methyl-Hg is one of the most dangerous pollutants in the environment. It is highly toxic and accumulates through the food chain. Tuna fish especially tends to concentrate Hg in the form of methyl-Hg. Quality assurance is a well established routine in analytical laboratories to control the variability of analytical results and to maintain adequate stability, detection power and reproducibility. Capillary electrophoresis (CE) has shown in recent years powerful capabilities for the resolution and analysis of very complex samples. The high resolution and peak capacity characteristics of this technique could be used favourably in speciation studies of organo-Hg compounds. Since the time needed for separation is usually very short in this technique, it lends itself to routine analysis. The application of quality control approaches in the analysis of methyl-Hg in tuna freeze-dried materials using CE is reported.     

Estimation of the uncertainty of CRMs in accordance with GUM: Application to the certification of four enzyme CRMs

Uncertainties of four enzyme-CRMs that have recently been certified in a co-operation between the IRMM and the International Federation for Clinical Chemistry were estimated. Estimation was based on the sum of the uncertainties of characterization, homogeneity and stability. Data from the certification collaborative study were used to estimate laboratory uncertainties, which form the basis for the uncertainty of characterization. Estimations for the uncertainty of homogeneity were derived from classical homogeneity studies. The estimations of uncertainty of stability caused the most difficulties. Realistic uncertainties fitting the needs of customers while being derived from measurement data based on theoretical considerations were obtained. Received: 11 May 2000 / Revised: 21 June 2000 / Accepted: 27 June 2000     

Preconcentration of anionic forms of chemical elements on filters with anchored quaternary ammonium groups

Sorption of silicomolybdic acid (SMA) and phosphovanadomolybdic acid (PVMA) and arsenic(V), vanadium(V), and chromium(VI) anionic species is studied on cellulose filters with bound quaternary ammonium groups. These heteropoly acids (HPAs) are recovered in quantity on filters from solutions with high salt backgrounds and with high mineral acid concentrations. AsO ₄ ^3? , CrO ₄ ^2? , and VO ₃ ^? anions are sorbed at pH of 3–9. In this case, the ionic strength considerably influences anion recovery. Conditions were found for preconcentrating vanadium, arsenic, and chromium from 250-mL aliquots of aqueous solutions (the preconcentration coefficient was 5 × 10³). A procedure was proposed for the sorption/X-ray fluorescence determination of these elements in high-purity water.     

Certification of reference materials for the quality control of major element determinations in groundwater Part 2: Certification

The quality control of groundwater monitoring requires the availability of representative CRMs. This paper describes the preparation of two artificial groundwater reference materials, CRM 616 (high carbonate content) and CRM 617 (low carbonate content), the homogeneity and stability studies and the analytical work performed for the certification of a range of major elements (Ca, Cl, Fe, K, Mg, Mn, Na, NO₃, PO₄ and SO₄).     

Certification of reference materials for the quality control of major element determinations in groundwater Part 2: Certification

The quality control of groundwater monitoring requires the availability of representative CRMs. This paper describes the preparation of two artificial groundwater reference materials, CRM 616 (high carbonate content) and CRM 617 (low carbonate content), the homogeneity and stability studies and the analytical work performed for the certification of a range of major elements (Ca, Cl, Fe, K, Mg, Mn, Na, NO₃, PO₄ and SO₄). Received: 15 May 1998 / Revised: 25 June 1998 / Accepted: 1 July 1998     

From experimental design to quality by design in pharmaceutical legislation

Quality by design (QbD) is a concept first outlined by Juran, who believed that quality could be planned and that most quality crises and problems relate to the way in which quality was planned in the first place. Experimental design is a powerful technique and tool for QbD, used for exploring new processes, gaining increased knowledge of the existing processes and optimizing these processes for achieving internationally competitive performance. It is also used for the investigation of relationship between parameters of ill-defined process. In this paper, the experimental design principles in pharmaceutical development and impact of these principles on pharmaceutical legislation have been reviewed. Also, slow implementation of QbD in pharmaceutical industries has been discussed. Pharmaceutical legislation is necessary for companies to continue benefiting from knowledge gained and to continually improve throughout the process lifecycle by making adaptations to assure that root causes of manufacturing problems are quickly corrected.     

Collaborative study for the quality control of trace element determinations in paint coatings Part 1. Interlaboratory study

Since the adoption of the European Standard EN71: Part 3 on toy safety, there has been dissatisfaction with the poor reproducibility obtained between laboratories using the test method for the determination of the migration of certain elements from paints to toys. This lack of quality control could result in toys being judged unacceptable with regard to the requirements of the EC Directive 88/378/EEC, which creates a potential barrier to trade. In order to improve the methods of measurements and testing, the Standards, Measurements and Testing Programme (SM&T) is currently supporting a project of which the final aim is to produce paint reference materials. The first step of this collaborative project is aimed to assess and possibly improve the state-of-the-art of trace element determinations in paint coatings through an interlaboratory study, the results of which are presented in this paper.