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Analytical and Bioanalytical Chemistry (v.378, #5)

Laboratory skills: mechanics and other hands-on skills by John Fetzer (pp. 1137-1138).

Chemical Logic Challenge (pp. 1139-1140).

Solution to Spectroscopy Challenge 5 (pp. 1141-1142).

Ninth international symposium on biological and environmental reference materials (BERM-9) by Jean Pauwels; Hendrik Emons (pp. 1143-1144).

COMAR²—the internet database for certified reference materials by Thomas Steiger; Rita Pradel (pp. 1145-1146).

Polybrominated diphenyl ether congeners and toxaphene in selected marine standard reference materials by John R. Kucklick; Karen J. S. Tuerk; Stacy S. Vander Pol; Michele M. Schantz; Stephen A. Wise (pp. 1147-1151).

Polybrominated diphenyl ether (PBDE) congeners and components of the complex mixture toxaphene are stable in the environment and readily bioaccumulated into wildlife and human tissues. PBDEs are presently used in large quantities worldwide as flame retardants in textiles, furniture, computer equipment, and cables. Toxaphene is a complex mixture of chlorinated bornanes and bornenes that was the most heavily used pesticide in the United States until it was banned in 1982; however, some countries continue to use toxaphene. The National Institute of Standards and Technology has quantified PBDE congeners and toxaphene in several available Standard Reference Materials (SRMs) using methods of gas chromatography with electron impact mass spectrometry (GC-EI-MS) and GC negative chemical ionization (NCI) MS, respectively. SRM 1588a Organics in Cod Liver Oil and SRM 1945 Organics in Whale Blubber were examined for PBDE congeners 47, 99, 100, 153, and 154, total toxaphene, and toxaphene congeners 26, 50, and 62. SRM 1946 Lake Superior Fish Tissue was also examined for total toxaphene and toxaphene congeners. The sum of the PBDE congeners (mean, (1 SD) wet basis) for SRM 1945 was 150 ng g⁻¹ (7 ng g⁻¹). The concentration of PBDE 47 in SRM 1588a was 82.7 ng g⁻¹ (2.8 ng g⁻¹). Other PBDEs were detected in SRM 1588a but were not quantified due their low levels. The total toxaphene (wet mass basis) was 1,210 ng g⁻¹ (127 ng g⁻¹), 1,960 ng g⁻¹ (133 ng g⁻¹), and 3,980 ng g⁻¹ (248 ng g⁻¹) in SRMs 1945, 1946, and 1588a, respectively. The values for PBDEs and toxaphene determined in the SRMs, while not certified, indicate that the SRMs will be suitable control materials for PBDE and toxaphene analyses.

Keywords: Reference material; Flame retardant; PBDE; Toxaphene; Fish; Marine mammal

Natural toxins: risks, regulations and the analytical situation in Europe by Hans P. van Egmond (pp. 1152-1160).

Natural toxins in food and feed are considered important food safety issues of growing concern, in particular mycotoxins, phycotoxins and plant toxins. Most scientific developments have occurred in the past few decades in the area of mycotoxins. Formal health risk assessments have been carried out by the Joint Expert Committee on Food Additives of the World Health Organization and the Food and Agriculture Organization. Limits and regulations for mycotoxins in food and feed have been established in many countries, including practically all European countries. An array of (formally validated) analytical methods and (certified) reference materials have become available. Several European research projects, funded by the European Commission and supported by the European Standardization Committee, have significantly contributed to this development. Quantitative methods of analysis for mycotoxins often make use of immunoaffinity cleanup with liquid chromatographic or gas chromatographic separation techniques in combination with various types of detectors, including mass spectroscopy. For screening purposes (bio)sensor-based techniques are among the promising newcomers. For the phycotoxins the situation is less advanced. Formal risk assessments by authoritative international bodies have not been carried out. Methods of analysis, formally validated according to internationally harmonized protocols, are scarce and animal testing still plays a key role in official methodology. The development of the analytical methodology is partly hampered by the limited availability of certain reliable calibrants and reference materials, although this situation is gradually improving. New regulations in the European Union have increased the pressure to develop and validate chemical methods of analysis. Joint efforts in the European context are now directed towards significantly improving this situation, and techniques such as liquid chromatography–mass spectroscopy offer promise in this respect. Both the working group on biotoxins of the European Standardization Committee and the network of National Reference Laboratories for Marine Biotoxins have taken up responsibilities here. The plant toxins are a category of natural toxins, where the situation is the least developed with respect to regulations, validated methods of analysis and reference materials. Yet, their occurrence in a wide range of consumable plant species demands the attention of the analytical community.

Keywords: Natural toxin; Mycotoxin; Phycotoxin; Plant toxin; Analysis; Reference material

Filling the AOAC triangle with food-matrix standard reference materials by Katherine E. Sharpless; Robert R. Greenberg; Michele M. Schantz; Michael J. Welch; Stephen A. Wise; Milan Ihnat (pp. 1161-1167).

Well-characterized reference materials are needed by laboratories in the food testing and nutrition communities to facilitate compliance with nutritional labeling laws, to provide traceability for food exports needed for acceptance in many foreign markets, and to improve the accuracy of nutrition information that is provided to assist consumers in making sound dietary choices. As a result of the enactment of the Nutrition Labeling and Education Act of 1990 and the Infant Formula Act of 1980, the National Institute of Standards and Technology (NIST) has developed a suite of food-matrix Standard Reference Materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM 1846 Infant Formula, SRM 1946 Lake Superior Fish Tissue, SRM 2383 Baby Food Composite, SRM 2384 Baking Chocolate, SRM 2385 Spinach, and SRM 2387 Peanut Butter. Many of these materials were developed at the request of the food industry to populate a nine-sectored fat-protein-carbohydrate triangle developed by AOAC International. With the completion of SRM 2387, SRMs representing each sector of the triangle are now available. These food-matrix reference materials are intended primarily for validation of analytical methods for the measurement of proximates, fatty acids, vitamins, minerals, and so on in foods of similar composition. They may also be used as “primary control materials” in the value-assignment of in-house, secondary, control materials to confirm accuracy as well as to establish traceability to NIST.

Keywords: Certified reference materials; Food-matrix reference materials; Nutrition labeling

Preservation of sensitive CRMs and monitoring their stability at IRMM by T. P. J. Linsinger; B. M. Gawlik; S. Trapmann; A. Lamberty; H. Emons (pp. 1168-1174).

Over the years, the nature of CRMs has changed considerably. Recently, more and more CRMs have been certified in their "natural" form, that is processed as little as possible, with analytes at their natural concentration level. This and the trend towards certified properties other than the concentrations of clearly defined molecules/elements have made guaranteeing stability of CRMs and estimating a shelf life an even more important issue for reference material producers than it has been before. One way to meet this challenge is to take more care in processing, storage and dispatch of CRMs. At IRMM, approximately 20 % of the RMs are stored at −20 °C or below and about 10% require cooled transportation. In addition, increased efforts for assessing stability are needed. Shelf lives are estimated using addition of an uncertainty component based on real-temperature stability studies rather than by accelerated stability studies. These pre-certification efforts are complemented by a stability-monitoring program, which at IRMM includes 80 % of the non-nuclear and non-isotopic materials. Although the costs for these efforts are high in absolute terms, they are only a minor and indispensable contribution to the total costs of CRM production.

Keywords: CRM; Stability monitoring; Degradation; Preservation; Stability study

Selenomethionine contents of NIST wheat reference materials by Wayne R. Wolf; Robert J. Goldschmidt (pp. 1175-1181).

Values of the total selenium and selenomethionine (Semet) content of four wheat-based reference materials have been obtained by gas chromatography-stable isotope dilution mass spectrometry methods. The total Se method is an established one, and the results obtained with it are consistent with previously-assigned values. The Semet method (previously reported by our laboratory) is based on reaction with CNBr. Our data indicate that the four wheat samples (wheat gluten, durum wheat, hard red spring wheat, and soft winter wheat), though having a 30-fold range in total Se content, all have about 45% of their total Se values in the form of selenomethionine. Investigation of the CNBr-based method suggests that additional experiments are needed to verify that all selenomethionine in the wheat samples is accounted for, but also indicates that the values obtained are within 15% of the true values. As the form in which Se occurs in foods and dietary supplements is important from a nutritional perspective, adding information about Se speciation to total Se values in appropriate reference materials makes these materials more valuable in relevant analytical work.

Keywords: Selenomethionine; Selenium; Mass spectrometry; Speciation

Production of a calibrant certified reference material for determination of the estrogenic mycotoxin zearalenone by Ralf Dieter Josephs; Rudolf Krska; Susan MacDonald; Pete Wilson; Hans Pettersson (pp. 1182-1189).

Several previous interlaboratory studies in the field of mycotoxin analysis have revealed considerable problems, apparent as high between-laboratory standard deviations, or rather non-comparable and non-traceable results. A major reason is lack of proper calibrants for external calibration. Public awareness of substances that mimic or interfere with the activity of natural hormones (endocrine disrupters) has led to increased interest in mycotoxins with estrogenic potential, e.g. zearalenone (ZON). During a large-scale standard measurement and testing (SMT) project of the European Commission (EC) dealing with the preparation and certification of reference materials for determination of the mycotoxin ZON in maize, a ZON calibrant in acetonitrile was prepared and intensively checked for purity, homogeneity, and stability. Preparation of the material, study of its homogeneity and stability, and characterisation of the calibrant on the basis of its preparation, with discussion of the results obtained, are described in this paper. The certified value of 9.95 µg mL⁻¹ for ZON in acetonitrile and its corresponding expanded uncertainty of ±0.30 µg mL⁻¹ were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement (GUM).

Keywords: Calibrant; Certified reference material (CRM); Expanded uncertainty; Mycotoxin; Zearalenone

Production of certified reference materials for mycotoxins: IRMM’s view on the assessment of uncertainties by Ralf Dieter Josephs; Robert Koeber; Thomas Peter Josef Linsinger; Alexander Bernreuther; Franz Ulberth; Heinz Schimmel (pp. 1190-1197).

Analytical difficulty and the economic importance of controlling mycotoxin levels in food and feed led the Community Bureau of Reference (BCR) to prepare a series of certified reference materials (CRM) for various mycotoxins. Because of the wide acceptance of these CRM and the need to ensure the comparability and traceability of measurements in the future it is necessary to prepare and certify new batches of mycotoxin reference materials (RM). In the following text two different approaches for evaluation of the characterisation uncertainty of CRM will be compared using the certification of aflatoxin M₁ (AfM₁) in milk powder as an example. The conventional approach is based on evaluation of characterisation exercise data; the alternative approach is based on measurement uncertainties of the employed analytical methods. Because laboratories are using totally different approaches to estimate the measurement uncertainties, combination of the uncertainties obtained from the participating laboratories was not recommended. Therefore, a new integrated approach for assessment of the measurement uncertainties of the analytical methods on the basis of additional data collected during the characterisation exercise will be described. The conventional approach was found to be the most appropriate and economical approach to evaluate the characterisation uncertainty as a characterisation exercise must be performed anyway to establish the property values of candidate (C)RM, irrespective of whether or not reliable measurement uncertainties can be provided by the laboratories. An integrated approach for assessment of measurement uncertainties based on additional characterisation data as applied here to enable use of an uncertainty-based approach provides more information but is too time-consuming and cost-intensive to become common practice.

Keywords: Mycotoxin; Aflatoxin M₁ ; Certified reference material; CRM; Characterisation; Uncertainty

Cloned plasmid DNA fragments as calibrators for controlling GMOs: different real-time duplex quantitative PCR methods by Isabel Taverniers; Erik Van Bockstaele; Marc De Loose (pp. 1198-1207).

Analytical real-time PCR technology is a powerful tool for implementation of the GMO labeling regulations enforced in the EU. The quality of analytical measurement data obtained by quantitative real-time PCR depends on the correct use of calibrator and reference materials (RMs). For GMO methods of analysis, the choice of appropriate RMs is currently under debate. So far, genomic DNA solutions from certified reference materials (CRMs) are most often used as calibrators for GMO quantification by means of real-time PCR. However, due to some intrinsic features of these CRMs, errors may be expected in the estimations of DNA sequence quantities. In this paper, two new real-time PCR methods are presented for Roundup Ready soybean, in which two types of plasmid DNA fragments are used as calibrators. Single-target plasmids (STPs) diluted in a background of genomic DNA were used in the first method. Multiple-target plasmids (MTPs) containing both sequences in one molecule were used as calibrators for the second method. Both methods simultaneously detect a promoter 35S sequence as GMO-specific target and a lectin gene sequence as endogenous reference target in a duplex PCR. For the estimation of relative GMO percentages both “delta C_T” and “standard curve” approaches are tested. Delta C_T methods are based on direct comparison of measured C_T values of both the GMO-specific target and the endogenous target. Standard curve methods measure absolute amounts of target copies or haploid genome equivalents. A duplex delta C_T method with STP calibrators performed at least as well as a similar method with genomic DNA calibrators from commercial CRMs. Besides this, high quality results were obtained with a standard curve method using MTP calibrators. This paper demonstrates that plasmid DNA molecules containing either one or multiple target sequences form perfect alternative calibrators for GMO quantification and are especially suitable for duplex PCR reactions.

Keywords: Reference materials; Cloned plasmid DNA standard; Real-time PCR; Duplex quantification; GMO

Human urine certified reference material CZ 6009: creatinine, styrene metabolites (mandelic acid and phenylglyoxylic acid) by I. Šperlingová; L. Dabrowská; V. Stránský; J. Kučera; M. Tichý (pp. 1208-1212).

The reference material was prepared by freeze-drying pooled urine samples obtained from healthy persons occupationally exposed to styrene. The concentrations of mandelic acid (MA), phenylglyoxylic acid (PGA), and hippuric acid (HA) in urine were determined by three modes of high-performance liquid chromatography (HPLC). For isochronous stability testing the urinary mandelic acid and phenylglyoxylic acid concentrations were followed over a 24-month period for a preliminary batch by use of HPLC. No changes of the concentration values were found. The creatinine concentration was stable for more than five years. Standard Reference Material NIST 914a Creatinine was used for traceability purposes for creatinine. Pure chemicals MA and PGA were used for traceability purposes. Control material ClinChek-Urine Control (Recipe) was analyzed simultaneously. The mean values of MA and PGA compare well with the means and fall within the control range of control samples. Results from homogeneity, stability, and traceability testing were evaluated using the statistical program ANOVA. The certified values and their uncertainties were evaluated from the results of interlaboratory comparisons, and homogeneity and stability tests. The values are unweighed arithmetical averages of accepted results and their uncertainties are combined uncertainties (coverage factor=1).

Keywords: Certified reference material; Styrene metabolites; Phenylglyoxylic acid; Mandelic acid; Human urine

Three new mussel tissue standard reference materials (SRMs) for the determination of organic contaminants by Dianne L. Poster; Michele M. Schantz; John R. Kucklick; Maria J. Lopez de Alda; Barbara J. Porter; Rebecca Pugh; Stephen A. Wise (pp. 1213-1231).

Three new mussel tissue standard reference materials (SRMs) have been developed by the National Institute of Standards and Technology (NIST) for the determination of the concentrations of organic contaminants. The most recently prepared material, SRM 1974b, is a fresh frozen tissue homogenate prepared from mussels (Mytilus edulis) collected in Boston Harbor, Massachusetts. The other two materials, SRMs 2977 and 2978, are freeze-dried tissue homogenates prepared from mussels collected in Guanabara Bay, Brazil and Raritan Bay, New Jersey, respectively. All three new mussel tissue SRMs complement the current suite of marine natural-matrix SRMs available from NIST that are characterized for a wide range of contaminants (organic and inorganic). SRM 1974b has been developed to replace its predecessor SRM 1974a, Organics in Mussel Tissue, for which the supply is depleted. Similarly, SRMs 2977 and 2978 were developed to replace a previously available (supply depleted) freeze-dried version of SRM 1974a, SRM 2974, Organics in Freeze-Dried Mussel Tissue. SRM 1974b is the third in a series of fresh frozen mussel tissue homogenate SRMs prepared from mussels collected in Boston Harbor starting in 1988. SRM 1974b has certified concentration values for 22 polycyclic aromatic hydrocarbons (PAHs), 31 polychlorinated biphenyl congeners (PCBs), and 7 chlorinated pesticides. Reference values are provided for additional constituents: 16 PAHs, 8 PCBs plus total PCBs, 6 pesticides, total extractable organics, methylmercury, and 11 trace elements. PAH concentrations range from about 2 ng g⁻¹dry mass (cyclopenta[cd]pyrene) to 180 ng g⁻¹dry mass (pyrene). PCB concentrations range from about 2 ng g⁻¹dry mass (PCB 157) to 120 ng g⁻¹dry mass (PCB 153). The reference value for total PCBs in SRM 1974b is (2020 ± 420) ng g⁻¹dry mass. Pesticide concentrations range from about 4 ng g⁻¹dry mass (4,4′-DDT) to 40 ng g⁻¹dry mass (4,4′-DDE). SRM 2977 has certified values for 14 PAHs, 25 PCB congeners, 7 pesticides, 6 trace elements, and methylmercury. Reference values for 16 additional PAHs and 9 inorganic constituents are provided, and information values are given for 23 additional trace elements. SRM 2978 has certified and reference concentrations for 41 and 22 organic compounds, respectively, and contains contaminant levels similar to those of SRM 1974b. Organic contaminant levels in SRM 2977 (mussels from Guanabara Bay, Brazil) are typically a factor of 2 to 4 lower than those in SRM 1974b and SRM 2978. The organic contaminant concentrations in each new mussel tissue SRM are presented and compared in this paper. In addition, a chronological review of contaminant concentrations associated with mussels collected in Boston Harbor is discussed as well as a stability assessment of SRM 1974a.

Keywords: Standard reference materials; SRMs; Mussels; PCBs; Pesticides; PAHs

The need for reference materials when monitoring nitrate intake by Isabel Castanheira; Luisa Oliveira; Ana Valente; Paula Alvito; Helena S. Costa; Anton Alink (pp. 1232-1238).

Whether dietary exposure to nitrate metabolites is detrimental or beneficial to human health has long been a matter of controversy. In spite of no consistent epidemiological evidence, nitrate metabolites are associated with the formation of carcinogenic-nitrosamines and gastric cancer. Furthermore, recent studies demonstrate that ingested nitrate plays a role in host defence against gastrointestinal pathogenic bacteria. Analytical values of nitrate content in foods are essential for estimating nitrate intake. The analytical process is of paramount importance for assessing human nitrate exposure and for establishing a link between these exposures and the current and future observed health effects. Therefore, the quality assurance of the measurement process is crucial to obtaining reliability, comparability and traceability of results. Certified Reference Materials (CRM) should play a role in the consistency of the measurement process. However, the availability of nitrate CRMs is still poor. When food monitoring is demanded, an approach could be to use In House Reference Materials (IHRM), prepared at a high metrological level, and all preparation steps should be quality driven. IHRMs were prepared, and available CRMs were used to provide traceability of the process. The homogeneity of IHRM was evaluated using an appropriate statistical design. The stability was monitored using an isochronous method. The material shelf life and storage conditions are presented.HPLC was optimised for the determination of nitrates in four vegetable categories. When a suite of IHRMs were used, the response of the HPLC system was linear over the range 1 to 8 mg L^–1. The detection limit for these compounds was 0.2 μg L⁻¹ and the determination limit 1.2 μg L⁻¹.The relationship between measurement uncertainty and critical points of the analytical process is presented. The differences in observed relative uncertainty between food categories could reflect current limitations in the food matrix reference materials.

Keywords: Nitrate intake; Feasibility study; Reference materials; Metrology; Traceability

Preparation and certification of a reference material for the determination of nutrients in seawater by Vincent Clancy; Scott Willie (pp. 1239-1242).

There is an urgent need for natural water reference materials certified for nutrients. In 1996, NRC collected seawater for a proposed CRM at a depth of 200 m in the North Atlantic; this was immediately filtered through 0.05-μm cartridge filters into 50-L carboys. The water was later homogenized in the NRC laboratories in Ottawa and stabilized via gamma irradiation. Over six years of stability testing no significant deterioration was detected. In addition to the usual customary standard colorimetric procedures, alternative analytical methods were developed to enable the certification process. The production of a CRM called MOOS-1 will be discussed. Certified values, with uncertainty components addressing the homogeneity, stability, and characterization of the material, were calculated to be: orthophosphate=1.56±0.07 µmol L⁻¹, silicate=26.0±1.0 µmol L⁻¹, nitrite=3.06±0.15 µmol L⁻¹, and nitrite and nitrate=23.7±0.9 µmol L⁻¹.

Keywords: Certified reference material; Nutrients; Seawater

Establishment of traceability of ammonium nitrogen determination in wastewater by Andreja Drolc; Milenko Roš; Magda Cotman (pp. 1243-1250).

A case study is presented for the establishment of traceability for ammonium nitrogen determination in wastewater in a routine laboratory in order to fulfil the requirements of ISO/IEC standard 17025. The necessary relevant information was obtained from the method validation data, the quality control data and equipment calibration certificates. The method of measurement is described together with the measurement equation, selected traceable reference standards and the associated measurement uncertainty. The major sources of uncertainty of the result of measurement were identified and the combined uncertainty was calculated. Identification of the main uncertainty sources represents the basis for target operations for reducing the measurement uncertainty of this determination.

Keywords: Ammonium nitrogen; Wastewater analysis; Measurement uncertainty; Traceability

Two new marine sediment standard reference materials (SRMs) for the determination of organic contaminants by Stephen A. Wise; Dianne L. Poster; Michele M. Schantz; John R. Kucklick; Lane C. Sander; Maria Lopez de Alda; Patricia Schubert; Reenie M. Parris; Barbara J. Porter (pp. 1251-1264).

Two new marine sediment standard reference materials (SRMs), SRM 1941b Organics in Marine Sediment and SRM 1944 New York/New Jersey Waterway Sediment, have been recently issued by the National Institute of Standards and Technology (NIST) for the determination of organic contaminants including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCB) congeners, and chlorinated pesticides. Both sediment SRMs were analyzed using multiple analytical methods including gas chromatography/mass spectrometry (GC/MS) on columns with different selectivity, reversed-phase liquid chromatography with fluorescence detection (for PAHs only), and GC with electron capture detection (for PCBs and pesticides only). SRM 1941b has certified concentrations for 24 PAHs, 29 PCB congeners, and 7 pesticides, and SRM 1944 has certified concentrations for 24 PAHs, 29 PCB congeners, and 4 pesticides. Reference concentrations are also provided for an additional 58 (SRM 1941b) and 39 (SRM 1944) PAHs, PCB congeners, and pesticides. SRM 1944, which was collected from multiple sites within New York/New Jersey coastal waterways, has contaminant concentrations that are generally a factor of 10–20 greater than SRM 1941b, which was collected in the Baltimore (Maryland) harbor. These two SRMs represent the most extensively characterized marine sediment certified reference materials available for the determination of organic contaminants.

Keywords: Certified reference materials (CRMs); Gas chromatography/mass spectrometry (GC/MS); Marine sediment; Polychlorinated biphenyls (PCBs); Polycyclic aromatic hydrocarbons (PAHs); Standard reference materials (SRMs)

Certification of mono-, di-, and tributyltin compounds in marine sediment certified reference material by species-specific isotope dilution mass spectrometric analysis using synthesized ¹¹⁸Sn-labeled butyltins by Kazumi Inagaki; Akiko Takatsu; Takuro Watanabe; Takayoshi Kuroiwa; Yoshie Aoyagi; Kensaku Okamoto (pp. 1265-1270).

A new marine sediment reference material (NMIJ CRM 7301-a) for butyltins analysis was prepared and certified by the National Metrological Institute of Japan, National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original material of the sediment was collected at a bay near industrial activities in Japan. The sediment material was air-dried, sieved, homogenized, and packaged into 1,000 glass bottles (60 g each). Certification of NMIJ CRM 7301-a was carried out at NMIJ using two different types of species-specific isotope dilution mass spectrometry: isotope dilution–ethylation–gas chromatography/inductively coupled plasma mass spectrometry (GC/ICPMS) and isotope dilution–ethylation–gas chromatography/mass spectrometry (GC/MS). A mixture of ¹¹⁸Sn-enriched monobutyltin, dibutyltin, and tributyltin was synthesized in our laboratory and was used as a spike for both techniques. Certified values are given for tributyltin (0.044±0.004 mg kg⁻¹ as Sn), dibutyltin (0.056±0.006 mg kg⁻¹ as Sn, and monobutyltin (0.058±0.013 mg kg⁻¹ as Sn), being at lower levels than currently available sediment CRMs for the analysis of organotins.

Keywords: Certification; Certified reference material; Species-specific isotope dilution; Butyltin; Sediment

Certified sediment reference materials for trace element analysis from the National Metrology Institute of Japan (NMIJ) by Kazumi Inagaki; Akiko Takatsu; Takayoshi Kuroiwa; Atsuko Nakama; Sakae Eyama; Koichi Chiba; Kensaku Okamoto (pp. 1271-1276).

Two types of sediment reference material (NMIJ 7302-a and 7303-a) for trace elements analysis have been prepared and certified by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). The original materials were collected from a bay near industrial activity in Kyushu (NMIJ CRM 7302-a; marine sediment) and from Lake Biwa (NMIJ CRM 7303-a; lake sediment). The sediment materials were air-dried, sieved, homogenized, packaged in 1000 glass bottles (60 g each), and radiation sterilized. Certification of these CRM for trace elements was conducted by NMIJ, where each element was determined by at least two independent analytical techniques. Isotope-dilution inductively coupled plasma mass spectrometry (ICP–MS) was applied for certification of all the elements except mono-nuclide elements such as As and Co. Other techniques such as ICP–MS with quadrupole mass spectrometry and sector-field mass spectrometry, inductively coupled plasma atomic emission spectrometry (ICP–AES), and atomic absorption spectrometry (AAS), were also used. Certified values have been provided for 14 elements (Sb, As, Cd, Cr, Co, Cu, Pb, Hg, Mo, Ni, Se, Ag, Sn, and Zn) in both CRM.

Keywords: Certification; Certified reference material; Isotope dilution; Trace elements; Sediment

New NIST sediment SRM for inorganic analysis by Rolf Zeisler (pp. 1277-1283).

NIST maintains a portfolio of more than 1300 standard reference materials (SRM), more than a third of these relating to measurements in the biological and environmental fields. As part of the continuous renewal and replacement efforts, a set of new marine sediments has been recently developed covering organic and inorganic determinations. This paper describes the steps taken in sample preparation, homogeneity assay, and analytical characterization and certification with specific emphasis on SRM 2702 inorganics in marine sediment. Neutron activation analysis showed the SRM to be highly homogeneous, opening the possibility for use with solid sampling techniques. The certificate provides certified mass fraction values for 25 elements, reference values for eight elements, and information values for 11 elements, covering most of the priority pollutants with small uncertainties of only several percent relative. The values were obtained by combining results from different laboratories and techniques using a Bayesian statistical model. An intercomparison carried out in field laboratories with the material before certification illustrates a high commutability of this SRM.

Keywords: Homogeneity; Instrumental neutron activation analysis; Marine sediment; Solid sampling; Trace elements; Value assignment

Certified reference materials to support a European thematic strategy for soil protection: the EUROSOILS (IRMM-443) experience by B. M. Gawlik; A. Lamberty; J. Pauwels; H. Muntau (pp. 1284-1287).

The recent proposal of thematic strategy for soil protection by the European Commission outlines that knowledge of problems associated with soil has increased considerably based on surveys, monitoring systems and data networks. Although this information is very useful, its value for the policy-making process is limited due to a lack of comparability. From this unsatisfying situation the need arises to develop an EU-wide monitoring system accompanied by suitable matrix reference materials. Experiences gained from the development and certification of IRMM-443 (The EUROSOILS) show how to approach the complex problem of providing suitable (i.e. representative) soil CRMs for the arising analytical needs to support existing and upcoming EU legislation.This paper presents briefly the quantitative findings of a certification exercise (adsorption coefficients for atrazine, lindane and 2,4-D, as well as pH in suspension). A comparison of these results with those of an intercomparison exercise organised in 1989 by the German UBA on very similar soils shows the significant improvement in the determination of soil adsorption coefficients that was induced by the EUROSOIL project. Indicative values of total and organic carbon content and nitrogen according to ISO Standards are also presented.Furthermore, the idea of reference soils and derived reference materials (for analytical purposes) as well as reference matrices (substrates for ecotoxicological testing) is highlighted and set into the context of horizontal standardisation of methods.

Keywords: Soil adsorption coefficients; CRM; Soil pH measurement; Soil protection

Shipboard analysis of picomolar levels of manganese in seawater by chelating resin concentration and chemiluminescence detection by Takashi Doi; Hajime Obata; Masahiro Maruo (pp. 1288-1293).

A new shipboard analytical method for determining picomolar levels of manganese in seawater has been developed. The method is based on a combination of chelating resin column extraction and improved chemiluminescence (CL) detection in a closed flow system. In this method, manganese in sample solution is selectively collected on newly-developed iminodiacetate-immobilized chelating resin, and then eluted with acidic solution containing hydrogen peroxide. The resulting eluent is mixed with luminol solution and aqueous ammonia after removal of iron ions by a chelating resin column, and then the mixture is introduced into the CL cell. The manganese concentration is obtained from the CL intensity. The detection limit (3SD) of manganese is 5 pmol L⁻¹ from 9 mL of seawater sample. The method was applied to seawater samples collected at the Okinawa Trough.

Keywords: Shipboard analysis; Manganese; Seawater; Chelating resin concentration; Chemiluminescence

Structure elucidation of nanogram quantities of unknown designer drugs based on phenylalkylamine derivates by ion trap multiple mass spectrometry by Stephan Kölliker; Michael Oehme (pp. 1294-1304).

Multiple mass spectra (MS¹ to MS⁶) of 55 phenylalkylamine derivatives were recorded with ion-trap mass spectrometry employing electrospray (ESI) and atmospheric pressure chemical ionization (APCI). Fragmentation patterns were studied in detail and a generally applicable scheme was established for elucidation of the structures of phenylalkylamine derivatives. HPLC combined with ion-trap multiple mass spectrometry was used to identify the structure of reaction by-products in ecstasy samples from the “black” market. Low nanogram amounts were sufficient for on-line HPLC–MS n structure elucidation of unknowns.

Keywords: Designer drugs; Dimethoxyamphetamine; LC–MS n ; MDMA; Phenethylamines; Trimethoxyamphetamine

Characterisation of selected drugs with nitrogen-containing saturated ring structures by use of electrospray ionisation with ion-trap mass spectrometry by W. Franklin Smyth; Venkataraman N. Ramachandran; Edmund O’Kane; Daniel Coulter (pp. 1305-1312).

The electrospray ionisation–ion-trap mass spectrometry (ESI–MS n) of selected drugs with nitrogen-containing saturated ring structures has been investigated. Sequential product-ion fragmentation experiments (MS n) have been performed to elucidate degradation pathways for the [M+H]⁺ ions and their predominant fragment ions. These MS n experiments result in characteristic fragmentations in which functional groups are generally cleaved from the ring systems as neutral molecules such as H₂O, amines, alkenes, esters, carboxylic acids, etc. When such a nitrogen-containing drug molecule also contains a functional group, such as an ester, that on liberation as a neutral molecule has a significantly lower −ΔH _f° value than that of the corresponding amine then the former is preferentially liberated. Furthermore, when an aromatic entity is present in these drug molecules together with the nitrogen-containing saturated ring structure fragmentation of the latter ring occurs with the former, predictably, being resistant to fragmentation. The structures of fragment ions proposed for ESI–MS n can be supported by electrospray ionisation–quadrupole time-of-flight mass spectrometry (ESI–QTOFMS). The data presented in this paper therefore provide useful information on the structure of these heterocyclic compounds which could be used to characterise unknown drug compounds isolated from natural sources, for example.

Keywords: Electrospray ionisation; Ion trap mass spectrometry; Time-of-flight mass spectrometry; Drugs

Application of the revised EU criteria for the confirmation of anabolic steroids in meat using GC-MS by Alida A. M. Stolker; Sylvia H. M. A. Linders; Leendert A. van Ginkel; Udo A. T. Brinkman (pp. 1313-1321).

The EU criteria for the confirmation of the presence of illegal compounds in biological matrices were recently revised. The old and the revised criteria were applied to relative ion intensities obtained for five anabolic steroids (methylboldenone, methyltestosterone, ethynylestradiol, β-boldenone and β-nortestosterone) in meat (cow, pig, turkey) and fish at concentrations ranging from 0.5 to 5.0 μg/kg. Confirmatory analysis was done by GC-MS; therefore four diagnostic ions had to be monitored and three ion ratios had to be calculated and tested against the criteria. Application of the old and revised criteria, with either standards or fortified samples as reference, showed mutually rather divergent results. Confirmation according to the revised EU criteria and using fortified samples as a reference gave the best results; in other words the highest percentage of diagnostic ion ratios within the tolerance intervals. A correlation was found between the percentage of these ion ratios and the signal/noise (S/N) ratio of the least intense ion of interest in the recorded MS spectrum. Although there were distinct differences in the results obtained for different analytes and sample types, it is safe to conclude that at S/N=3 the percentage of ratios within the tolerance intervals generally will be at or below 50%, while for S/N≥10, the percentage increases to over 90%. In the present study, fully satisfactory results were obtained down to about 2 μg/kg, but not for lower analyte concentrations.

Keywords: Residue; Analysis; Quality criterion; Identification point

Quantification of bile acids directly from plasma by MALDI-TOF-MS by DebraLynn Mims; David Hercules (pp. 1322-1326).

Matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (MS) has proved to be a useful method for the quantification of bile acids directly from plasma. Six cholic acid derivatives were selected for analysis: taurocholic acid, taurochenodeoxycholic acid, taurolithocholic acid, glycocholic acid, glycochenodeoxycholic acid, and glycolithocholic acid. Solid-phase extraction (SPE) columns were used to preconcentrate and purify the plasma samples. Calibration curves averaged from 3 days were obtained for the bile acids, and then tested for their ability to accurately determine concentrations from one measurement. In summary, a simple, rapid method has been developed for the quantification of bile salts from plasma by MALDI-MS with SPE cleanup.

Keywords: Bile acids; MALDI; SPE; Quantification; Plasma

Thick-film electrodes for measurement of superoxide and hydrogen peroxide based on direct protein–electrode contacts by Andrey V. Krylov; Moritz Beissenhirtz; Holger Adamzig; Frieder W. Scheller; Fred Lisdat (pp. 1327-1330).

Cytochrome c was immobilized on screen-printed thick-film gold electrodes by a self-assembly approach using mixed monolayers of mercaptoundecanoic acid and mercaptoundecanol. Cyclic voltammetry revealed quasi-reversible electrochemical behavior of the covalently fixed protein with a formal potential of +10 mV vs. Ag/AgCl. Polarized at +150 mV vs. Ag/AgCl the electrode was found to be sensitive to superoxide radicals in the range 300–1200 nmol L⁻¹. Compared with metal needle electrodes sensitivity and reproducibility could be improved and combined with the easiness of preparation. This allows the fabrication of disposable sensors for nanomolar superoxide concentrations. By changing the electrode potential the sensor can be switched from response to superoxide radicals to hydrogen peroxide—another reactive oxygen species. H₂O₂ sensitivity can be provided in the range 10–1000 μmol L⁻¹ which makes the electrode suitable for oxidative stress studies.

Keywords: Thick-film electrodes; Screen-printing; Cytochrome c; Biosensor; Superoxide; Hydrogen peroxide

Biomimetic piezoelectric quartz sensor for caffeine based on a molecularly imprinted polymer by Benilda S. Ebarvia; Christina A. Binag; Fortunato Sevilla III (pp. 1331-1337).

A piezoelectric quartz sensor coated with molecularly imprinted polymer (MIP) for caffeine was developed. The MIP was prepared by co-polymerizing methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) in the presence of azobis(isobutyronitrile) as initiator, caffeine as template molecule, and chloroform as solvent. The MIP suspension in polyvinyl chloride/tetrahydrofuran (6:2:1 w/w/v) solution was spin coated onto the surface of the electrode of a 10 MHz AT-cut quartz crystal. The sensor exhibited a linear relationship between the frequency shift and caffeine concentration in the range of 1×10⁻⁷ mg mL⁻¹up to 1x10⁻³ mg mL⁻¹ [correlation coefficient (r)=0.9935] in a stopped flow measurement mode. It has a sensitivity of about 24 Hz/ln(concentration, mg mL⁻¹). A steady-state response was achieved in less than 10 min. The performance characteristic of the sensor shows a promising and inexpensive alternative method of detecting caffeine. Surface studies were carried out for the reagent phase of the sensor using SEM, AFM, and XPS analysis in order to elucidate the imprinting of the caffeine molecule. The SEM micrograph, AFM image, and XPS spectra confirmed the removal of caffeine by Soxhlet extraction in the imprinting process and the rebinding of caffeine to the MIP sensing layer during measurement.

Keywords: Molecularly imprinted polymer; Piezoelectric quartz crystal; Caffeine; Surface characterization; Chemical sensor; Methacrylic acid

A one-step immunochromatographic assay for detecting ginsenosides Rb1 and Rg1 by Waraporn Putalun; Noriko Fukuda; Hiroyuki Tanaka; Yukihiro Shoyama (pp. 1338-1341).

An immunochromatographic strip test has been developed for detecting ginsenosides Rb1 (G-Rb1) and Rg1 (G-Rg1). This qualitative assay system is useful as a rapid screening method for detecting G-Rb1 and G-Rg1 in plants and plant preparations. Our assay is a competitive immunoassay that uses anti-G-Rb1 and anti-G-Rg1 monoclonal antibodies (MAbs) and a detection reagent that contains colloidal gold particles coated with anti-G-Rb1 and anti-G-Rg1 MAbs. Detection limits are 2 μg mL⁻¹ for both G-Rb1 and G-Rg1.

Keywords: Ginsenoside Rb1; Ginsenoside Rg1; Immunochromatographic

Characterization of honey amino acid profiles using high-pressure liquid chromatography to control authenticity by J. F. Cotte; H. Casabianca; B. Giroud; M. Albert; J. Lheritier; M. F. Grenier-Loustalot (pp. 1342-1350).

Amino acid analysis of honey by high-performance liquid chromatography (HPLC) was used first to discriminate different botanical origins and then to combat adulteration. Pure honeys of seven selected floral varieties were examined. A principal component analysis (PCA) was carried out on the results after selection of the most discriminating parameters. Lavender honeys were thus perfectly characterized, but complete satisfaction was not obtained with the six other varieties. This method (analysis by HPLC and statistical processing by PCA) enabled us to detect the addition of sugar syrup to rape and fir honeys.

Keywords: Honey; Amino acid; Analysis; HPLC; Adulteration; Authenticity

Voltammetric behaviour and determination of moxifloxacin in pharmaceutical products and human plasma by N. Erk (pp. 1351-1356).

The oxidative behaviour of moxifloxacin was studied at a glassy carbon electrode in different buffer systems using cyclic, differential pulse, and Osteryoung square-wave voltammetry. The oxidation process was shown to be irreversible over the entire pH range studied (2.0–10.0) and was diffusion-controlled. The methods were performed in Britton–Robinson buffer and the corresponding calibration graphs were constructed and statistical data were evaluated. When the proposed methods were applied at pH 6.0 linearity was achieved from 4.4×10⁻⁷ to 1.0×10⁻⁵ mol L⁻¹. Applicability to tablets and human plasma analysis was illustrated. Furthermore, a high-performance liquid chromatographic method with diode-array detection was developed. A calibration graph was established from 4.0×10⁻⁶ to 5.0×10⁻⁵ mol L⁻¹ moxifloxacin. The described methods were successfully employed with high precision and accuracy for estimation of the total drug content of human plasma and for pharmaceutical dosage forms of moxifloxacin.

Keywords: Moxifloxacin; Cyclic voltammetry; Differential pulse voltammetry; Osteryoung square-wave voltammetry; High-performance liquid chromatography; Human plasma

Determination of organotin compounds in biological samples using accelerated solvent extraction, sodium tetraethylborate ethylation, and multicapillary gas chromatography–flame photometric detection by Andrzej Wasik; Tomasz Ciesielski (pp. 1357-1363).

A method has been developed for species-selective analysis of organotin compounds in solid, biological samples. The procedure is based on accelerated solvent extraction (ASE) of analytes and includes extraction of the tin species with a methanol–water (90% methanol) solution of acetic acid/sodium acetate containing tropolone (0.03% w/v), their ethylation with NaBEt₄, and separation and detection by GC–FPD. The analytical procedure was optimized with an unspiked sample of harbor porpoise (Phocoena phocoena) liver. Effects of ASE operational variables (extraction temperature and pressure, solvent composition, number of static extraction steps) are discussed. Method detection limits (MDL) were in the range 6–10 ng(Sn) g⁻¹ dry weight and 7–17 ng(Sn) g⁻¹ dry weight for butyl- and phenyltin compounds, respectively. Recoveries were comparable with or better than those obtained by use of other procedures reported in the literature. The analytical procedure was validated by analysis of NIES No. 11 (fish tissue) certified reference material.

Keywords: Biological samples; Organotin compounds; Extraction; Multicapillary gas chromatography

Direct optical resolution of the enantiomers of novel chiral tetrahedral metal clusters by HPLC on a cellulose tris-(3,5-dimethylphenylcarbamate) stationary phase by Wenzhi Li; Weiqiang Zhang; Quanyi Zhao; Yongmin Li; Chunlin Ma; Liren Chen; Yuanqi Yin (pp. 1364-1368).

The enantioseparation of seven novel chiral transition metal tetrahedral clusters has been achieved for the first time on cellulose derivatized with tris(3,5-dimethylphenylcarbamate) (CDMPC) as chiral stationary phase (CSP) and hexane containing different alcohols as modifiers as mobile phases. The effect of mobile-phase composition on enantioselectivity was studied, and the effect of structural variation of the solutes on their enantioseparation was also investigated. It was found that both the metal in the tetrahedral core and the ligand coordinated to the atom in the tetrahedral core had significant effects on the chromatographic behavior of the analytes.

Keywords: Chiral stationary phase; Cellulose tris(3,5-dimethylphenylcarbamate); Chiral transition-metal tetrahedral cluster; Enantioseparation

Solvent extraction of amino acids into a room temperature ionic liquid with dicyclohexano-18-crown-6 by Svetlana V. Smirnova; Irina I. Torocheshnikova; Andrey A. Formanovsky; Igor V. Pletnev (pp. 1369-1375).

Amino acids Trp, Gly, Ala, Leu are extracted efficiently from aqueous solution at pH 1.5–4.0 (Lys and Arg at pH 1.5–5.5) into the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF₆) with dicyclohexano-18-crown-6 (CE). The most hydrophilic amino acids such as Gly are extracted as efficiently as the less hydrophilic (92–96%). The influence of pH, amino acid and crown ether concentration, volume ratio of aqueous and organic phases, and presence of some cations on amino acid recovery were studied. The ratio of amino acid to crown ether in the extracted species is 1:1 for cationic Trp, Leu, Ala, and Gly and to 1:2 for dicationic Arg and Lys. This ionic liquid extraction system was used successfully for the recovery of amino acids from pharmaceutical samples and fermentation broth, and was followed by fluorimetric determination.

Keywords: Room temperature ionic liquid; Liquid–liquid extraction; Amino acids; Dicyclohexano-18-crown-6

Dynamic ultrasound-assisted leaching of essential macro and micronutrient metal elements from animal feeds prior to flame atomic absorption spectrometry by F. Priego-Capote; M. D. Luque de Castro (pp. 1376-1381).

A method for routine analysis of essential metal elements in animal feeds using a dynamic and automated ultrasound-assisted extractor is proposed here. Owing to the different concentration of the essential metal elements in the samples, two macronutrients—namely, Ca and Mg—and three micronutrients or trace elements—namely, Fe, Cu and Zn—were selected as models for the optimisation and characterisation of the proposed method by using experimental design methodology. Moreover, the extraction kinetics and influence of the particle size on the extraction efficiency were studied. The detection and quantification limits ranged between 2.9 and 40 μg kg⁻¹ and between 7.9 and 95.5 μg kg⁻¹, respectively. The precision, expressed as repeatability relative standard deviation (RSD) and as within-laboratory RSD, ranged between 1.86 and 5.66% and between 5.06 and 6.15%, respectively. The proposed approach allows the extraction of these metal elements from animal feeds with extraction efficiencies similar to those provided by the AOAC Official Method 968.08, but with a drastic reduction in both the extraction time (18 min versus 4.5 h) and sample handling, and using smaller volumes of extractant (an acid aqueous solution).

Keywords: Animal feed; Dynamic ultrasound-assisted leaching; FAAS

A method for near-infrared spectral calibration of complex plant samples with wavelet transform and elimination of uninformative variables by Xueguang Shao; Fang Wang; Da Chen; Qingde Su (pp. 1382-1387).

An algorithm is proposed for extracting relevant information from near-infrared (NIR) spectra for multivariate calibration of routine components in complex plant samples. The algorithm is a combination of wavelet transform (WT) data compression and a procedure for uninformative variable elimination (UVE). After compression of the NIR spectra by WT, the UVE approach is used to eliminate the irrelevant wavelet coefficients. Finally, a calibration model is built from the retained wavelet coefficients to enable prediction. Because irrelevant information can be removed from the spectra used for multivariate calibration, the model based on the extracted relevant features is better than those obtained with full-spectrum data. Both prediction precision and calculation speed are improved.

Keywords: Wavelet transform; Uninformative variable elimination (UVE); Partial least squares (PLS); Near-infrared spectrum

Speciation analysis of mercury in water samples by cold vapor atomic absorption spectrometry after preconcentration with dithizone immobilized on microcrystalline naphthalene by Ali Mohammad Haji Shabani; Shayessteh Dadfarnia; Navid Nasirizadeh (pp. 1388-1391).

Trace amounts of inorganic mercury (Hg²⁺) and methylmercury cations (MeHg²⁺) were adsorbed quantitatively from acidic aqueous solution onto a column packed with immobilized dithizone on microcrystalline naphthalene. The trapped mercury was eluted with 10 ml of 7 mol L⁻¹ hydrochloric acid solution. The Hg²⁺ was then directly reduced with tin (II) chloride, and volatilized mercury was determined by cold vapor atomic absorption spectrometry (CVAAS). Total mercury (Hgt) was determined after decomposition of MeHg⁺ into Hg²⁺. Hg²⁺ and MeHg⁺ cations were completely recovered from the water with a preconcentration factor of 200. The relative standard deviation obtained for eight replicate determinations at a concentration of 0.3 μg L⁻¹was 1.8%. The procedure was applied to analysis of water samples, and the accuracy was assessed via recovery experiment.

Keywords: Mercury; Dithizone; Microcrystalline naphthalene; Cold vapor atomic absorption spectrometry

Wavelet packet transform and artificial neural network applied to simultaneous kinetic multicomponent determination by Shouxin Ren; Ling Gao (pp. 1392-1398).

This paper presents a novel method, named wavelet packet transform based multilayer feedforward neural network with Levenberg–Marquardt and back propagation algorithm (WPTLMBP), developed for simultaneous kinetic determination of Cu(II), Fe(III), and Ni(II). Wavelet packet representations of signals provided a local time–frequency description, thus in the wavelet packet domain the quality of noise removal can be improved. The artificial neural network was applied for non-linear multivariate calibration. In this study, by optimization, wavelet packet function, decomposition level and number of hidden nodes for WPTLMBP method were selected as Db2, 2, and 4 respectively. A program PWPTLMBP was designed to perform simultaneous kinetic determination of Cu(II), Fe(III), and Ni(II). The relative standard error of prediction (RSEP) for all components with WPTLMBP, LM-BP-MLFN, and PLS methods were 6.39, 10.4, and 8.30%, respectively. Experimental results showed the proposed method to be successful and better than the others.

Keywords: Wavelet packet transform; Simultaneous kinetic multicomponent determination; Artificial neural network

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Analytical and Bioanalytical Chemistry (v.378, #5)

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Analytical and Bioanalytical Chemistry (v.378, #5)