Analytica Chimica Acta (v.608, #2)

Contents (iii-iv).

The radiometric methods, alpha (α)-, beta (β)-, gamma (γ)-spectrometry, and mass spectrometric methods, inductively coupled plasma mass spectrometry, accelerator mass spectrometry, thermal ionization mass spectrometry, resonance ionization mass spectrometry, secondary ion mass spectrometry, and glow discharge mass spectrometry are reviewed for the determination of radionuclides. These methods are critically compared for the determination of long-lived radionuclides important for radiation protection, decommissioning of nuclear facilities, repository of nuclear waste, tracer application in the environmental and biological researches, these radionuclides include 3H, 14C, 36Cl, 41Ca, 59,63Ni, 89,90Sr, 99Tc, 129I, 135,137Cs, 210Pb, 226,228Ra, 237Np, 241Am, and isotopes of thorium, uranium and plutonium. The application of on-line methods (flow injection/sequential injection) for separation of radionuclides and automated determination of radionuclides is also discussed.
Keywords: Review; Radionuclides; Radiometric methods; Mass spectrometric methods; Environmental radioactivity; Nuclear waste; Characterization of waste; Environmental samples; Alpha spectrometry; Beta counting; Liquid scintillation counting; Gamma spectrometry; Inductively coupled plasma mass spectrometry; Accelerator mass spectrometry; Thermal ionization mass spectrometry; Secondary ion mass spectrometry; Glow discharge mass spectrometry; Neutron activation analysis;

A spectroelectrochemical approach to the electrodeposition of bismuth film electrodes and their use in stripping analysis by Eva Tesařová; Aránzazu Heras; Álvaro Colina; Virginia Ruiz; Ivan Švancara; Karel Vytřas; Jesús López-Palacios (140-146).
UV–vis reflection spectroelectrochemistry has proven to be a very useful multiresponse technique to evaluate the quality of bismuth films obtained by electrochemical deposition on glassy carbon electrodes (GCEs). Bismuth films have recently emerged as a promising and environmental friendly alternative to mercury electrodes for stripping analysis. Spectroelectrochemical measurements, carried out in a flow cell, allowed us to follow in situ the electrodeposition and stripping of bismuth and cadmium. Electrochemical and spectroscopic responses individually have led to successfully quantify the amount of cadmium in test solutions.
Keywords: Spectroelectrochemistry; Bismuth film; Electrochemical stripping analysis; Spectroelectrochemical flow cell;

The effect of oxidation of anoxic sediment upon the extraction of 13 elements (Cd, Sn, Sb, Pb, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As) using the optimised Community Bureau of Reference of the European Commission (BCR) sequential extraction procedure and a dilute acid partial extraction procedure (4 h, 1 mol L−1 HCl) was investigated. Elements commonly associated with the sulfidic phase, Cd, Cu, Pb, Zn and Fe exhibited the most significant changes under the BCR sequential extraction procedure. Cd, Cu, Zn, and to a lesser extent Pb, were redistributed into the weak acid extractable fraction upon oxidation of the anoxic sediment and Fe was redistributed into the reducible fraction as expected, but an increase was also observed in the residual Fe. For the HCl partial extraction, sediments with moderate acid volatile sulfide (AVS) levels (1–100 μmol g−1) showed no significant difference in element partitioning following oxidation, whilst sediments containing high AVS levels (>100 μmol g−1) were significantly different with elevated concentrations of Cu and Sn noted in the partial extract following oxidation of the sediment. Comparison of the labile metals released using the BCR sequential extraction procedure (ΣSteps 1–3) to labile metals extracted using the dilute HCl partial extraction showed that no method was consistently more aggressive than the other, with the HCl partial extraction extracting more Sn and Sb from the anoxic sediment than the BCR procedure, whilst the BCR procedure extracted more Cr, Co, Cu and As than the HCl extraction.
Keywords: Sequential extraction; Community Bureau of Reference of the European Commission; Partial extraction; Dilute HCl; Anoxic sediment; Acid volatile sulfide;

A new straightforward method based on cloud-point extraction (CPE) was developed to determine osthole in rat plasma by reversed phase high-performance liquid chromatography with ultraviolet detection using a photodiode array detector. The non-ionic surfactant Triton X-114 was chosen as the extract solvent. Variable parameters affecting the CPE efficiency were evaluated and optimized. A Zorbax SB-C18 column was used for elution separation at 25 °C with detection wavelength at 322 nm. Under the optimum conditions, the method was shown to be reproducible and reliable with intra-day precision below 7.62%, inter-day precision below 6.37%, and accuracy within ±5.02% and mean extraction recovery more than 90.4%, which were all calculated using a range of spiked samples at three concentrations of 0.5, 5.0 and 15.0 μg mL−1 for osthole in plasma. The calibration curve for the analyte was linear in the range from 0.1 to 20 μg mL−1 with the correlation coefficients greater than 0.9981. Limit of detection (S/N = 3) was less than 0.03 μg mL−1and limit of quantification (S/N = 10) was less than 0.1 μg mL−1. After strict validation, the method was successfully applied to the pharmacokinetic study of osthole in rats after oral and intravenous administration, respectively.
Keywords: Osthole; Cloud-point extraction; High-performance liquid chromatography; Triton X-114; Pharmacokinetics;

Accurate screening for synthetic preservatives in beverage using high performance liquid chromatography with time-of-flight mass spectrometry by Xiu Qin Li; Feng Zhang; Yan Yan Sun; Wei Yong; Xiao Gang Chu; Yan Yan Fang; Jerry Zweigenbaum (165-177).
In this study, liquid chromatography time-of-flight mass spectrometry (HPLC/TOF-MS) is applied to qualitation and quantitation of 18 synthetic preservatives in beverage. The identification by HPLC/TOF-MS is accomplished with the accurate mass (the subsequent generated empirical formula) of the protonated molecules [M + H]+ or the deprotonated molecules [M − H]−, along with the accurate mass of their main fragment ions. In order to obtain sufficient sensitivity for quantitation purposes (using the protonated or deprotonated molecule) and additional qualitative mass spectrum information provided by the fragments ions, segment program of fragmentor voltages is designed in positive and negative ion mode, respectively. Accurate mass measurements are highly useful in the complex sample analyses since they allow us to achieve a high degree of specificity, often needed when other interferents are present in the matrix. The mass accuracy typically obtained is routinely better than 3 ppm. The 18 compounds behave linearly in the 0.005–5.0 mg·kg−1 concentration range, with correlation coefficient >0.996. The recoveries at the tested concentrations of 1.0 mg·kg−1–100 mg·kg−1 are 81–106%, with coefficients of variation <7.5%. Limits of detection (LODs) range from 0.0005 to 0.05 mg·kg−1, which are far below the required maximum residue level (MRL) for these preservatives in foodstuff. The method is suitable for routine quantitative and qualitative analyses of synthetic preservatives in foodstuff.
Keywords: Liquid Chromatography Time-of-Flight Mass Spectrometry; Synthetic Preservative; Screening; Beverage;

The spontaneous formation of the neurotoxic carcinogen acrylamide in a wide range of cooked foods has recently been discovered. These foods include bread and other bakery products, crisps, chips, breakfast cereals, and coffee. To date, the diminutive size of acrylamide (71.08 Da) has prevented the development of screening immunoassays for this chemical. In this study, a polyclonal antibody capable of binding the carcinogen was produced by the synthesis of an immunogen comprising acrylamide derivatised with 3-mercaptobenzoic acid (3-MBA), and its conjugation to the carrier protein bovine thyroglobulin. Antiserum from the immunised rabbit was harvested and fully characterised. It displayed no binding affinity for acrylamide or 3-MBA but had a high affinity for 3-MBA-derivitised acrylamide. The antisera produced was utilised in the development of an ELISA based detection system for acrylamide. Spiked water samples were assayed for acrylamide content using a previously published extraction method validated for coffee, crispbread, potato, milk chocolate and potato crisp matrices. Extracted acrylamide was then subjected to a rapid 1-h derivatisation with 3-MBA, pre-analysis. The ELISA was shown to have a high specificity for acrylamide, with a limit of detection in water samples of 65.7 μg kg−1, i.e. potentially suitable for acrylamide detection in a wide range of food commodities. Future development of this assay will increase sensitivity further. This is the first report of an immunoassay capable of detecting the carcinogen, as its small size has necessitated current analytical detection via expensive, slower, physico-chemical techniques such as Gas or Liquid Chromatography coupled to Mass Spectrometry.
Keywords: Acrylamide immunoassay; ELISA; Dietary carcinogen; Derivatised;

A miniature cytometry platform for capture and characterization of T-lymphocytes from human blood by He Zhu; Monica Macal; Caroline N. Jones; Michael D. George; Satya Dandekar; Alexander Revzin (186-196).
Given the clinical and diagnostic importance of blood analysis, there is considerable interest in developing novel miniature devices for rapid characterization of blood constituents. The present paper describes development of a miniature cytometry platform aimed at analysis of T-lymphocytes from peripheral human blood. Microarrays of T-cell-specific antibodies (Abs), including anti-CD3, -CD4, -CD8 and mouse IgG (negative control) were robotically printed onto glass slides coated with a non-fouling poly(ethylene glycol) (PEG) hydrogel. The glass substrates containing Ab arrays were incubated with 100 μL of red blood cell (RBC)-depleted whole human blood for 15 min and then exposed to a controlled shear of ∼2 dyn cm−2 for additional 10 min. This process led to the removal of non-specific leukocytes and “development” of patterns of T-cells captured on the Ab spots. The immunofluorescent staining of the surface-bound cells revealed the presence of purified CD4+ and CD8+ T-cells (purity >94%) on their respective Ab spots. Importantly, the proportions of CD4+ and CD8+ T-cells captured on the Ab spots correlated closely (R 2 − 0.9) with flow cytometry analysis of T-cell subsets in blood. Overall, this cytometry platform allowed to rapidly (under 30 min) capture pure T-cell subsets from minimally processed human blood. Significantly, our device provided quantitative information about subset abundance solely based on the location of cells within the microarray. This cytometry platform is envisioned as a miniature immunology tool for determination of T-cell phenotype and will have immediate applications in HIV diagnostics and research.
Keywords: Blood-based diagnostics; Antibody microarrays; Cell microarrays; T-cell capture;

Analytical followup of the gamma initiated synthesis of a molecularly imprinted polymer by Zoltán Zsebi; Viola Horváth; Ágnes Sáfrány; George Horvai (197-203).
A molecularly imprinted polymer (MIP) for the template phenytoin has been prepared by gamma initiated copolymerization of methacrylamide and ethylene glycol dimethacrylate. The progress of polymerization was studied by measuring the monomer conversions and the template binding properties of the resulting polymers, respectively. The consumption rate of the two monomers showed different course. There was no difference observed in the polymerization rates of the MIP and the control polymer (NIP). The template binding properties of the MIP and the NIP changed considerably with the progress of the polymerization process and became similar to those of the thermally initiated polymers after full conversion.
Keywords: Molecular imprinting; Gamma polymerization; Radiation polymerization; Conversion rates;

Determination of imipenem and rifampicin in mouse plasma by high performance liquid chromatography–diode array detection by R. Fernández-Torres; M.A. Bello-López; M. Callejón-Mochón; J.C. Jiménez-Sánchez (204-210).
A high performance liquid chromatographic (HPLC) method for the determination of imipenem and rifampicin was developed and validated. The method involves plasma deproteinisation with methanol, gradient elution on a RP-18 column and diode array detection. Separation was carried out in 8 min using a mobile phase composed of methanol and 0.2 M borate buffer (pH 7.2). Imipenem and rifampicin were detected at 300 nm and 255 nm, respectively. A linear response was observed at plasma levels ranged between 0.3 and 30 μg mL−1 for imipenem and 1.5 and 20 μg mL−1 for rifampicin. The detection limits were 0.07 μg mL−1 and 0.47 μg mL−1 for imipenem and rifampicin, respectively. The method was applied to the determination of both compounds in mouse plasma samples.
Keywords: Imipenem; Rifampicin; High performance liquid chromatography; Mouse plasma;

Estimation of single-nucleotide polymorphism allele frequency by alternately binding probe competitive polymerase chain reaction by Naohiro Noda; Hidenori Tani; Nao Morita; Shinya Kurata; Kazunori Nakamura; Takahiro Kanagawa; Satoshi Tsuneda; Yuji Sekiguchi (211-216).
Estimation of single-nucleotide polymorphism (SNP) allele frequency in pooled DNA samples is a promising approach to clarify the relationships between SNPs and diseases. Here, we present a simple, accurate, and cost-effective method for estimating SNP allele frequency, called alternately binding probe (ABProbe) competitive polymerase chain reaction (ABC-PCR) that entails no expensive devices for real-time fluorescence measurement and complex post-PCR steps. We prepared DNA pools of PCR products derived from homozygous samples of three different SNPs (ALDH2, GNB3, and HTR2A) in different portions, and the allele frequencies of these samples were estimated by ABC-PCR. Two alleles were coamplified by PCR with a fluorescent probe that binds to either alleles, and then fluorescence intensity was measured using a simple fluorometer. The ratio of the two alleles was calculated from the fluorescence intensity of the probe at the end-point. The estimated allele frequencies strongly correlated to the expected ratios for all three SNPs with high accuracy. When the allele frequencies were more than 5%, the relative standard deviations (R.S.D.s) of ABC-PCR were less than 20%. Moreover, we also confirmed that this method was applicable to SNP genotyping.
Keywords: Single-nucleotide polymorphism; Allele frequency; Alternately binding probe competitive polymerase chain reaction; Fluorescence quenching; Competitive polymerase chain reaction; Real-time polymerase chain reaction;

Effective monitoring for ractopamine residues in samples of animal origin by SPR biosensor and mass spectrometry by Colin S. Thompson; Simon A. Haughey; Imelda M. Traynor; Terence L. Fodey; Christopher T. Elliott; Jean-Philippe Antignac; Bruno Le Bizec; Steven R.H. Crooks (217-225).
Ractopamine (RCT) is a member of the β-2-agonist (β-agonist) family. It is licensed for use as an animal growth promoter in more than 20 countries worldwide, including the United States and Canada, but is either not licensed or prohibited by over 150 others, including those within the European Union. The issue of the use of RCT in livestock bound for human consumption has risen to prominence recently following the decision by The People's Republic of China to ban the import of pork from a number of processing plants after finding traces of RCT in shipments from the U.S.A.In order to monitor for the illegal use of such compounds within Europe, there is a requirement to have a robust and reliable testing scheme capable of the detection of low concentrations of RCT. In the present study an optical biosensor screening assay was developed. The developed assay was compared with a liquid chromatography/mass spectrometry/mass spectrometry (LC–MS/MS) confirmatory procedure. These methods were used to study the ability to detect RCT in pigs following treatment. Both testing procedures were capable of detecting low μg kg−1 concentrations of the drug in urine and liver. Liver was found to be a less suitable sample matrix, with RCT residue levels being undetectable after 5 days withdrawal of the drug. Urine samples however still contained detectable RCT residues several weeks after withdrawal. The correlation (as measured by r 2) between the biosensor and LC–MS/MS methods was 0.99 and 0.97 for urine and liver samples, respectively.It is concluded that testing regimes based on RCT analysis in liver are less likely to detect illegal administration of the drug than those based on urine analysis. Urine samples provide an excellent matrix for the detection of RCT residues for an extended period post withdrawal.
Keywords: Ractopamine; Residues; Biosensor; Screening; Confirmation; Liquid chromatography/mass spectrometry/mass spectrometry;