Reference standards for quantitative trace analysis of PCB's by GC. Technical PCB formulations for the calibration of ECD and MSD responses

Summary The composition of any technical PCB formulation can be determined directly by analyzing the PCB sample by gas chromatography with a flame ionization detector (GC-FID), provided the relative molecular masses of the components are known. The responses of electron capture and selected-ion monitoring, mass-spectra detectors can then be calibrated for individual PCB congeners by correlation of the chromatographic patterns with those of concentrated PCB samples obtained by GC-FID. This procedure, which uses a given technical PCB formulation as a secondary reference standard mixture, is to be preferred over existing calibration methods, when results with ±10% errors are acceptable because commercial PCB formulations cover the whole range of chlorination products.     

Synthesis of dioxin-like monofluorinated PCBs: for the use as internal standards for PCB analysis

Monofluorinated polychlorinated biphenyls (fluoro-PCBs) have been prepared using the Suzuki-coupling, for use as analytical standards for PCB measurements. Seven of these fluoro-PCBs are analogues of the dioxin-like PCBs, listed by the WHO as the most toxic PCB congeners. Four highly chlorinated fluoro-PCBs have been prepared by Suzuki-coupling of 2,3,5,6-tetrachloro-bromoaniline with various substituted arylboronic acids. The resulting amino-fluoro-PCBs are chlorinated using the Sandmeyer reaction or deaminated to yield tetra-, penta- and hexa-chlorinated fluoro-PCBs. The fluoro-PCBs elute just before the corresponding PCBs in the GC chromatogram, which strongly indicates their potential as analytical standards.     

Complete PCB congener distributions for 17 aroclor mixtures determined by 3 HRGC systems optimized for comprehensive,quantitative, congener-specific analysis

Three HRGC systems (1: 30m DB-XLB capillary with MS-SIM detection; 2: 60m DB-XLB capillary with full-scan, ion-trap MS detection; and 3: Parallel dual-column DB-17 and series-coupled HP5/HT5 with ECD detection) were used to completely characterize multiple lots of 8 different-numbered Aroclor mixtures by quantitative calibration against 9 solutions containing primary standards of all 209 PCB congeners. Despite lower absolute sensitivity and more Aroclor congener coelutions than the dual-column ECD system, the MS systems enabled measurement of more congeners per Aroclor since their greater linear response range did not require dilution of samples and standards. Pairs of different lots of Aroclors 1248 and 1254 displayed markedly different proportions of congeners, and the 1254 pair displayed strong differences in the extent of ortho-chlorine substitution. The tables of congener weight percent distributions among Aroclors are more comprehensive and quantitatively precise than those of prior publications. However, the limitations of single-level calibration precluded measurement of all congeners to the ±10% accuracy desirable for establishing these Aroclors as secondary standards for comprehensive, quantitative congener-specific PCB analysis.     

Ion-implanted reference standards for use in microchemical analysis of materials

Summary A concise overview has been given of the present state of development of ion-implanted reference standards for the calibration of instrumental methods of microchemical characterization of solid materials.

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Ionen-implantierte Standardpräparate für die Mikroanalyse

Zusammenfassung Der gegenwärtige Entwicklungsstand ionenimplantierter Standardpräparate für die Eichung instrumenteller Mikromethoden der chemischen Feststoffanalyse wurde besprochen.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana,and in Vitro Evaluation of Its Antioxidant Activity

Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO₂) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C₁₅H₂₆O, was the major constituent (20.04–36.87%) in all extracts. Oxygenated sesquiterpenes (24.36–43.14%), C₁₀H₁₆, monoterpenes (27.70–39.87%), and C₁₅H₂₄, sesquiterpenes (10.04–22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (C_n > 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.     

Preparation of pentylated organotin standards for use in trace analysis with gas chromatography

A method for the preparation and purification of pentylated derivatives is described for nine organotin compounds that are relevant in environmental analysis (tributyltin acetate, dibutyltin dichloride, butyltin trichloride, triphenyltin chloride, diphenyltin dichloride, phenyltin trichloride, tricyclohexyltin hydroxide (cyhexatin), dicyclohexyltin dibromide and bis (trineophyltin) oxide (fenbutatinoxide)). The compounds are synthesized on a 100 mg scale and purified by column chromatography. Purity checks were performed with gas chromatography with mass selective detection. The mass spectrum of pentyltrineophyltin is presented.     

Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique

Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/l to 1.0 ng/l and from 1.0 pg/l to 1.0 ng/l in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.Dedicated to Professor Leslie S. Ettre on the occasion of his 70th birthday.     

Using additional standards for increasing the accuracy of quantitative chromatographic analysis

Uncontrolled partial losses at the step of sample injection into a gas chromatographic column increase errors of determination by the external standard, absolute calibration, and standard addition methods. Modified method is proposed for quantitative analysis; it includes the introduction of additional standards into test samples and calculations by the ratio between the areas of chromatographic peaks and peaks of standards rather than the absolute areas of chromatographic peaks. The calculation equations are presented for modified methods of quantitative analysis using additional standards, including those for estimating random errors of determination. The relative standard deviations of peak areas were shown to be 6–38-fold lower than the analogous statistical characteristics of absolute areas. This ensures a high accuracy of quantitative determinations even under the conditions of low reproducibility of sample dosing. Solvents contained in the analyzed samples can be used as additional standards. This version can be recommended as a routine method of data representation and processing.     

The complementary use of radioanalytical methods and trace analysis methods for the characterisation of environmental IAEA reference materials

The IAEA laboratories have access to both nuclear analytical methods and conventional instrumental methods for trace analysis for the characterisation of its environmental and biological reference materials. A technical concept integrating the homogeneity data, the recommended test portion mass and the uncertainty on the trace element concentrations is explored using a combination of INAA, XRF, ICP-MS, ICP-AES, and AAS. The above approach is illustrated by selected examples of reference materials currently under evaluation for their trace element content. They include some or all of the following elements Al, As, Br, Ca, Cd, Co, Cr, Cs, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Th, U, Zn in environmental biomonitor organisms (lichen, algae) and air dust filters.     

Qualitative and quantitative analysis of the unsaponifiable fraction of vegetable oils by using comprehensive 2D GC with dual MS/FID detection

The present investigation is focused on the development of a comprehensive two-dimensional GC (GC?×?GC) method, with dual MS/FID detection, for the qualitative and quantitative analysis of the entire unsaponifiable fraction of vegetable oils. The unsaponifiable fraction forms a minor, highly specific part of a vegetable oil, and can be used as an indicator of genuineness. The column set used consisted of a low-polarity first dimension, and a medium-polarity secondary one, both characterized by a high thermal stability. The use of dual detection enabled the attainment of both mass spectral information and relative % FID data. The complexity of the fingerprint, generated by the unsaponifiable fraction, fully justified the employment of the two-dimensional GC technology. Furthermore, two other GC?×?GC benefits contributed greatly to the attainment of promising results, namely sensitivity enhancement and the formation of group-type patterns. The method herein proposed could potentially open a new opportunity for the more in-depth knowledge of the unsaponifiable fraction of vegetable oils.     

Certification of reference materials for inorganic trace analysis: the INCT approach

This paper presents the work done by the Institute of Nuclear Chemistry and Technology (INCT), Warsaw on a procedure of the certification of matrix reference materials (CRMs) for inorganic trace analysis. The INCT has been involved in preparation and certification of that type of CRMs since 1986 till now. The certification of CRMs is performed on the basis of statistical evaluation of the data obtained from the worldwide interlaboratory comparison. The initially adopted certification procedure has been developed, and the final shape is presented and discussed. The modifications are connected with the new demands of the international standards. The results of analysis of candidate CRMs obtained by the potentially primary procedures based on radiochemical neutron activation analysis (RNAA) and results of analysis of CRM accompanying candidate RMs are applied in the certification process for quality assurance purpose.     

Development of standards for reliable surface analyses by ISO technical committee 201 on surface chemical analysis

The need for reliable surface analyses together with quality‐management requirements for analytical laboratories led the International Organization for Standardization (ISO) to form its Technical Committee (TC) 201 on Surface Chemical Analysis in 1991. This article describes the organization of TC 201, the strategies that have been found useful for identifying and assessing possible projects for new international standards, and the 57 international standards and other documents prepared to date by TC 201. Standards have now been developed for Auger‐electron spectroscopy, glow‐discharge spectroscopy, various types of scanning probe microscopy, secondary‐ion mass spectrometry, sputter‐depth profiling, total‐reflection X‐ray fluorescence spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray reflectometry. In addition, standards have been developed with definitions of terms used in surface chemical analysis; the handling, preparation of specimens for surface analysis; information and data‐transfer formats; and methods for determining the lateral resolution of beam‐based methods of surface analysis. Copyright © 2014 John Wiley & Sons, Ltd.     

Radiochemical separation for the certification of some trace elements in biological reference materials by neutron activation analysis

A radiochemical separation procedure based on chromatographic separation using Chelex-100 in 0.1M HAc-0.1M NH₄Ac at pH 4.8 and TDO in 6M HCl, has been developed to determine Cd, Co, Cr, Fe, Se, The, U, W and Zn in three biological materials of botanic origin used as SRM's: 1547 Peach Leaves, 1515 Apple Leaves and the new proposed material Spinach. The aim was to obtain more information for these elements whose values are not yet determined or are given only as suggested values.     

Extending the use of certified reference sediments for assessment of accuracy in determinations of trace metals

Straightforward analysis for components in a single certified reference sediment is of limited use for assessing the accuracy of environmental determinations. A systematic approach requires mixing of certified sediments, one with another and with environmental samples, and the preparation of secondary reference material by the laboratory. Use of Youden pairs, reference material embedded in samples and linear models should enable valid accuracy statements to be made based on well known statistical concepts. For assessing accuracy, reference sediments which are matched in particle size, and are end-members for components or sediment types are most useful.     

Trends in certified reference materials for the speciation of trace elements.

The measurement of the chemical species of elements (instead of the total element concentration) has become an irreversible trend in analytical chemistry. The motivation lies in the fact that the biochemical and geochemical behaviour of an element is governed by its species. Quality assurance of the analytical procedures used for speciation analysis requires the analysis of representative reference materials, certified for the relevant species. Up to now the number of existing certified reference materials for trace element species is very limited. The most important ones are environmental CRMs certified for trialkyltin compounds, methylmercury, Cr(III)/Cr(VI) and food CRMs certified for arsenic species and methylmercury. Major developments are to be expected in CRMs focussed on environmental problems, including waste treatment, on bioavailability of trace elements in food and on bio-monitoring in occupational health and hygiene. It is, however, unlikely that the producers of CRMs will ever be able to cover all needs. Add to this that many, very active species are notoriously unstable and/or short living and require in-situ analysis. This will lead to different analytical developments, such as analyses in-situ, where the classical concept of CRMs may not stand firm anymore.     

Some fundamental and technical aspects of the quantitative analysis of pharmaceutical drugs by matrix-assisted laser desorption/ionization mass spectrometry

The purpose of the present paper was to study some of the underlying physical and technical aspects of high-throughput quantitative matrix-assisted laser desorption/ionization (MALDI) of small drug molecules. A prototype MALDI-triple quadrupole instrument equipped with a high repetition rate laser was employed. Initially, the detection limits and dynamic ranges for the quantitation of four drugs (quinidine, danofloxacin, ramipril and nadolol) were determined. Internal standards were carefully chosen for each of these analytes in terms of structure similarity and fragmentation pathways. Three organic matrices were tested for these assays, resulting in different crystallization behaviors and measurement reproducibilities. alpha-Cyano-4-hydroxycinnamic acid yielded the best results and was subsequently employed for the quantitative determination of all four analytes. Further experiments considered the role of laser energy and pulse rate on the ablated areas as well as ion signals. Light microscope and scanning electron microscope images allowed the examination of the ablated area of the MALDI spots. The images showed convincing evidence that the ablated area was virtually void of crystals after analysis, with no preferential removal of material in the center of the laser's path. Average values for the amount of material ablated were determined to be 3.9+/-0.5% of the total spot size, and as low as 19.5 attomoles of analyte were detectable for our most sensitive analyte, ramipril. It was calculated that, under these assay conditions, it was possible to accurately quantify less than 1 femtomole of all analytes with the use of appropriately pure internal standards. These studies showed very promising results for the quantitative nature of MALDI for small molecules with molecular weights less than 500 Da.     

Five years activity in determining trace elements for the certification of standard reference materials by neutron activation analysis

Summary A review of the experiences developed in the last five years of analytical work concerning the determination of trace element concentrations in reference materials by neutron activation analysis has been reported and discussed. Several elements such as Co, Sc, Mn, V, Fe, La, Sb, Zn, Th, have been determined by instrumental neutron activation analysis, while elements such as Hg, Se, As, Cu, Cd, I, required a selective radiochemical procedure. The results obtained are compared with the final certified values. For each matrix and/or group of matrices analytical problems and their solutions are illustrated.

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Fünf Jahre Tätigkeit zur Bestimmung von Spurenelementen zwecks Sicherung von Standardproben durch Neutronenaktivierung

Zusammenfassung Eine Übersicht über die Erfahrungen der letzten 5 Jahre bei der analytischen Bestimmung von Spurenelementen mittels Neutronenaktivierung wurde gegeben und diskutiert. Einzelne Elemente wie Co, Sc, Mn, V, Fe, La, Sb, Zn und Th wurden mit Hilfe instrumenteller Neutronenaktivierungsanalyse bestimmt; andere Elemente, wie Hg, Se, As, Cu, Cd und J, erfordern ein selektives radiochemisches Verfahren. Die erhaltenen Ergebnisse wurden mit sichergestellten Werten verglichen. Für jede Matrix bzw. Matrixgruppe wurden die analytischen Probleme und deren Lösung angegeben.

     

Cabbage leaves CL-1 certified reference material for the trace analysis of plant materials

Summary The preparation of cabbage leaves (CL-1) certified reference material and homogenisation procedures are described and relevant data are compiled. In evaluation of the data four concurrent tests (Dixon's, Grubb's, Nalimov's and the test of coefficient of Kurtosis) for outlier rejection at the significance level 0.05 have been applied. As a result it was possible to establish certified concentration values for 10 elements and reference values for 4 elements.

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Zertifiziertes Referenzmaterial Cabbage Leaves CL-1 für die Spurenanalyse von pflanzlichem Material

     

On the role of environmental reference materials in the development of horizontal standards for environmental protection

The need for standardisation and harmonisation of measurements increases with the progress of the European integration process. One of the areas for which the need for harmonisation has been emphasised is the protection of the soil compartment. While knowledge of problems associated with soils is increasing in Europe, based on soil surveys, monitoring systems and data networks, the corresponding (analytical) data is not often comparable, which limits its value for policy development. In this context, the European Commission has invited the Member States to investigate the possibility for a harmonisation of European standards in the fields of soil, sludge and biodegradable waste (compost). Furthermore, the development of new reference materials for both the validation of these new methods and their successful implementation on a routine basis is required. This paper shows some selected examples for which the development of horizontal standards may be worth investigating. In addition, it discusses and proposes the vehicle of (C)RMs for the implementation of a common measurement system for soil, related to these horizontal standards. It also raises some open questions and sheds light on future perspectives and challenges.Presented at BERM-9 – 9^th International Symposium on Biological and Environmental Reference Materials, June 15–19, Berlin, Germany