Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytica Chimica Acta (v.624, #1)
A review of analytical methods for the determination of aminoglycoside and macrolide residues in food matrices by Tara A. McGlinchey; Paul A. Rafter; Fiona Regan; Gillian P. McMahon (pp. 1-15).
The development of antibiotic resistance in bacteria has been attributed to the overuse of antimicrobials in human medicine. Another route by which humans are exposed to antibiotics is through the animal foods we eat. In modern agricultural practice, veterinary drugs are being used on a large scale, administered for treating infection or prophylactically to prevent infection. Hence, there is pressure on analytical scientists to detect and confirm the presence of antimicrobials in foods of animal origin.The aminoglycosides and macrolides are two families of antibiotics, each with important applications in veterinary medicine. These antibiotics are widely used in the treatment of bacterial disease, e.g., aminoglycosides for mastitis and macrolides for enteric infections. They have also been used as feed additives for growth promotion. As a result, legislation has been laid down by the European commission in which member states must meet strict criteria for monitoring residues (including antimicrobials). Testing for low levels of aminoglycosides and macrolides in foods is a priority and hence the development of fast, reliable, sensitive methods for their extraction and subsequent analysis is of great interest.This paper reviews analytical methods for both extracting and determining these classes of antibiotics in various food matrices focusing in particular on the last 10 years. Extraction and clean-up methods such as deproteinisation, and solid-phase extraction are described. Various screening methods are also covered including thin layer chromatography (TLC), enzyme immunoassay, capillary electrophoresis (CE) and microbiological assays. Finally, liquid chromatography (LC) methods are discussed which are combined with mass spectrometry (MS) when sensitivity requirements are stringent.
Keywords: Veterinary antibiotics; Aminoglycosides; Macrolides; Screening methods; Confirmation methods; Analysis; Extraction; Complex matrices
Review of a current role of mass spectrometry for proteome research by Chung-Hsuan (Winston) Chen (pp. 16-36).
This review is intended to give readers a snapshot of current mass spectrometry for proteomics research. It covers a brief history of mass spectrometry proteomic research, peptidomics and proteomics for biomarker search, quantitative proteomics, proteomics with post-translational modification and future perspective of proteomics.
Keywords: Proteomics; Glycomics; Collision-induced dissociation (CID); Electron capture dissociation (ECD); Quantitative proteomics
Characterisation and quantification of organic phosphorus and organic nitrogen components in aquatic systems: A Review by Paul J. Worsfold; Philippe Monbet; Alan D. Tappin; Mark F. Fitzsimons; David A. Stiles; Ian D. McKelvie (pp. 37-58).
This review provides a critical assessment of knowledge regarding the determination of organic phosphorus (OP) and organic nitrogen (ON) in aquatic systems, with an emphasis on biogeochemical considerations and analytical challenges. A general background on organic phosphorus and organic nitrogen precedes a discussion of sample collection, extraction, treatment/conditioning and preconcentration of organic phosphorus/nitrogen from sediments, including suspended particulate matter, and waters, including sediment porewaters. This is followed by sections on the determination of organic phosphorus/nitrogen components. Key techniques covered for organic phosphorus components are molecular spectrometry, atomic spectrometry and enzymatic methods. For nitrogen the focus is on the measurement of total organic nitrogen concentrations by carbon hydrogen nitrogen analysis and high temperature combustion, and organic nitrogen components by gas chromatography, high-performance liquid chromatography, gel electrophoresis, mass spectrometry, nuclear magnetic resonance spectrometry, X-ray techniques and enzymatic methods. Finally future trends and needs are discussed and recommendations made.
Keywords: Organic nitrogen; Organic phosphorus; Aquatic systems; Sediment; Water; Suspended particulate matter
Method validation for determination of arsenic, cadmium, chromium and lead in milk by means of dynamic reaction cell inductively coupled plasma mass spectrometry by S. D’Ilio; F. Petrucci; M. D’Amato; M. Di Gregorio; O. Senofonte; N. Violante (pp. 59-67).
With Regulation No. 1881/2006 the European Union fixed a maximum level for lead in milk. Consequently, there is the need to determine very low concentration of elements that may be present in milk in trace and ultratrace levels.Quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) combined with dynamic reaction cell (DRC) has been widely employed in order to reach very low concentration, requested for this product. Furthermore, the DRC technology can help in removing polyatomic and argon-based interferences.In the present study, a method for the determination of arsenic, cadmium, chromium and lead in bovine milk was validated according to the EU common standards by means of DRC–ICP-MS. The main parameters evaluated in the validation were: recovery, repeatability and within-laboratory reproducibility, detection and quantification limits, linearity range and measurement uncertainty. Additionally, stability studies of the analyte in solution and ruggedness studies were carried out.The results obtained for limit of detection (LoD) and limit of quantification (LoQ) in μgkg−1 were respectively: As, 3.1 and 9.5; Cd, 0.08 and 0.24; Cr, 0.229 and 0.693; Pb, 0.5 and 1.5. While for the recovery: As, 91%; Cd 96%; Cr 99%; Pb, 95%. As for the repeatability: As, 7%; Cd, 3%; Cr, 6%; Pb, 4%.
Keywords: Method validation; Milk; Trace elements; Inductively coupled plasma mass spectrometry
Application of chemometric tools for coal classification and multivariate calibration by transmission and drift mid-infrared spectroscopy by M.T. Bona; J.M. Andrés (pp. 68-78).
The aim of this paper focuses on the determination of nine coal properties related to combustion power plants (moisture (%), ash (%), volatile matter (%), fixed carbon (%), heating value (kcalkg−1), carbon (%), hydrogen (%), nitrogen (%) and sulphur (%)) by mid-infrared spectroscopy. For that, a wide and diverse coal sample set has been clustered into new homogeneous coal subgroups by the use of hierarchical clustering analysis. This process was performed including property values and spectral data (scores of principal component analysis, PCA) as independent variables. Once the clusters were defined, the corresponding property calibration models were performed by partial least squares regression. Several mathematical pre-treatments were applied to the original spectral data in order to cope with some non-linearities. The accuracy and precision levels for each property were studied. The results revealed that coal properties related to organic components presented relative error values around 2% for some clusters, comparable to those provided by commercial online analysers. Finally, the discrimination level between those groups of samples was evaluated by linear discriminant analysis (LDA). The sensitivity of the system was studied accomplishing percentages close to 100% when the samples were classified attending only to their mid-infrared spectra.
Keywords: Coal analysis; Hierarchical cluster analysis (HCA); Partial least squares regression (PLS); Linear discriminant analysis (LDA)
Optimisation of stir bar sorptive extraction and liquid desorption combined with large volume injection-gas chromatography–quadrupole mass spectrometry for the determination of volatile compounds in wines by Elisabete Coelho; Rosa Perestrelo; Nuno R. Neng; José S. Câmara; Manuel A. Coimbra; J.M.F. Nogueira; Sílvia M. Rocha (pp. 79-89).
Stir bar sorptive extraction and liquid desorption followed by large volume injection coupled to gas chromatography–quadrupole mass spectrometry (SBSE–LD/LVI-GC–qMS) had been applied for the determination of volatiles in wines. The methodology was optimised in terms of extraction time and influence of ethanol in the matrix; LD conditions, and instrumental settings. The optimisation was carried out by using 10 standards representative of the main chemical families of wine, i.e. guaiazulene, E, E-farnesol, β-ionone, geranylacetone, ethyl decanoate, β-citronellol, 2-phenylethanol, linalool, hexyl acetate and hexanol. The methodology shows good linearity over the concentration range tested, with correlation coefficients higher than 0.9821, a good reproducibility was attained (8.9–17.8%), and low detection limits were achieved for nine volatile compounds (0.05–9.09μgL−1), with the exception of 2-phenylethanol due to low recovery by SBSE. The analytical ability of the SBSE–LD/LVI-GC–qMS methodology was tested in real matrices, such as sparkling and table wines using analytical curves prepared by using the 10 standards where each one was applied to quantify the structurally related compounds. This methodology allowed, in a single run, the quantification of 67 wine volatiles at levels lower than their respective olfactory thresholds. The proposed methodology demonstrated to be easy to work-up, reliable, sensitive and with low sample requirement to monitor the volatile fraction of wine.
Keywords: Stir bar sorptive extraction; Liquid desorption; Large volume injection; Volatile compounds; Gas chromatography–quadrupole mass spectrometry; Wine
Ultra trace determination of 31 pesticides in water samples by direct injection–rapid resolution liquid chromatography-electrospray tandem mass spectrometry by Laura Díaz; Julio Llorca-Pórcel; Ignacio Valor (pp. 90-96).
A liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method for the detection of pesticides in tap and treated wastewater was developed and validated according to the ISO/IEC 17025:1999. Key features of this method include direct injection of 100μL of sample, an 11min separation by means of a rapid resolution liquid chromatography system with a 4.6mm×50mm, 1.8μm particle size reverse phase column and detection by electrospray ionization (ESI) MS–MS. The limits of detection were below 15ngL−1 and correlation coefficients for the calibration curves in the range of 30–2000ngL−1 were higher than 0.99. Precision was always below 20% and accuracy was confirmed by external evaluation. The main advantages of this method are direct injection of sample without preparative procedures and low limits of detection that fulfill the requirements established by the current European regulations governing pesticide detection.
Keywords: Direct injection; Water analysis; Pesticides; Method validation; Rapid resolution; Liquid chromatography-tandem mass spectrometry
Efficient mining of myxobacterial metabolite profiles enabled by liquid chromatography–electrospray ionisation-time-of-flight mass spectrometry and compound-based principal component analysis by Daniel Krug; Gabriela Zurek; Birgit Schneider; Ronald Garcia; Rolf Müller (pp. 97-106).
Bacteria producing secondary metabolites are an important source of natural products with highly diverse structures and biological activities. Developing methods to efficiently mine procaryotic secondary metabolomes for the presence of potentially novel natural products is therefore of considerable interest. Modern mass spectrometry–coupled liquid chromatography can effectively capture microbial metabolic diversity with ever improving sensitivity and accuracy. In addition, computational and statistical tools increasingly enable the targeted analysis and exploration of information-rich LC–MS datasets.In this article, we describe the use of such techniques for the characterization of myxobacterial secondary metabolomes. Using accurate mass data from high-resolution ESI-TOF measurements, target screening has facilitated the rapid identification of known myxobacterial metabolites in extracts from nine Myxococcus species. Furthermore, principal component analysis (PCA), implementing an advanced compound-based bucketing approach, readily revealed the presence of further compounds which contribute to variation among the metabolite profiles under investigation. The generation of molecular formulae for putative novel compounds with high confidence due to evaluation of both exact mass position and isotopic pattern, is exemplified as an important key for de-replication and prioritization of candidates for further characterization.
Keywords: Principal component analysis; High-resolution mass spectrometry; Myxobacteria; Secondary metabolites; Natural products
Determination of ent-kaurene in subcutaneous fat of Iberian pigs by gas chromatography multi-stage mass spectrometry with the aim to differentiate between intensive and extensive fattening systems by Mónica Narváez Rivas; José Julian Rios; Jesús F. Arteaga; José F. Quilez; Alejandro F. Barrero; Manuel León-Camacho (pp. 107-112).
This work presents a gas chromatography multi-stage mass spectrometry (GC–MS3) method for the determination of ent-kaurene in subcutaneous fat of Iberian pig, present in adipose tissue of animals due to pasture ingestion (extensive fattening system). The method comprises a saponification and a liquid–liquid extraction of the unsaponifiable fraction, followed by an isolation of the hydrocarbon fraction by high performance liquid chromatography (HPLC) and analysis by GC–MS3 (ion trap) with electronic ionization. The GC–MS3 analysis allows the isolation and characterization of specific fragments from the original (MS1) molecular structure, and particularly, those fragments originated from the precursor ion ( m/ z=229) characteristic of ent-kaurene. The MS/MS product fragment m/ z=213 is used as a further precursor fragment giving rise to a MS3 spectrum specific for ent-kaurene. The limit of detection of the MS3 technique is lower than 0.2μgkg−1 and a linear regression has been found between 0.2 and 112μgkg−1. This method is applicable for the determination of the fattening system of the Iberian pig.
Keywords: Iberian pig; Subcutaneous fat; Ent-kaurene; Ion trap; Multi-stage mass spectrometry; Gas chromatography
Characterization of estuarine sediments by near infrared diffuse reflectance spectroscopy by Javier Moros; María C. Barciela-Alonso; Paula Pazos-Capeáns; Pilar Bermejo-Barrera; Elena Peña-Vázquez; Salvador Garrigues; Miguel de la Guardia (pp. 113-127).
It has been developed a partial least squares near infrared (PLS-NIR) method for the determination of estuarine sediment physicochemical parameters. The method was based on the chemometric treatment of first order derivative reflectance spectra obtained from samples previously lyophilized and sieved through a lower than 63μm grid. Spectra were scanned from 833 to 2976nm, averaging 36 scans per spectrum at a resolution of 8cm−1, using chromatographic glass vials of 9.5mm internal diameter as measurement cells. Models were built using reference data of 31 samples selected through the use of a hierarchical cluster analysis of NIR spectra of sediments obtained from the Ria de Arousa estuary and prediction parameters were established from a validation set of 50 samples of the same area. pH, redox potential (Eh), carbon (C), nitrogen (N) and hydrogen (H) content together with Sn, Pb, Cd, As, Sb and total Cr and also acid soluble, reducible and oxidable Cr fractions were employed as characteristic parameters of the studied sediments. Standard error of prediction values for C and N content were of the order of 4 and 1.3mgg−1 for H. Prediction errors for pH and Eh were 0.15 units and 37mV, respectively, thus indicating the good prediction capabilities of the method. Regarding trace metal concentrations PLS-NIR provided prediction error levels for unknown samples around 20% for Sn, Pb, As and Sb and root mean square errors of prediction around 40% for concentration levels of 400ngg−1 Cd and 100μgg−1 Cr. For the different extractable fractions of Cr the residual prediction deviation varied from 1.3 to 1.7 but relative errors found for samples of the validation set were only useful for screening purposes.
Keywords: Partial-least-squares; Near infrared; Diffuse reflectance; Marine sediments; Hierarchical cluster analysis
Selectively light scattering spectrometric detection of copper (II) based on a new synthesized oxamide ligand by Yun Fei Long; Cheng Zhi Huang; Rong Xing He; Yuan Fang Li (pp. 128-132).
Light scattering (LS) signals have been applied for analytical detections, but the selectivity is poor. In order to improve the selectivity, pre-separation or new machines are generally considered. Differing from these methods, we synthesized a highly selective oxamide ligand, N′, N′-bis (2-aminophenyl) oxamide (NAPO). It was found that the LS signals of NAPO, measured with a common spectrofluorometer, could be selectively enhanced by copper ion in neutral medium. Thus, a new highly selective detection method for copper ion could be developed over the range of 0.9–31.0μM with the limit of determination of 97.6nM (3 σ). Foreign ions including Cd(II), Al(III) could be allowed even if present at the level of 7-fold more than that of Cu2+, avoiding pre-separation procedures from complicated samples such as real wastewater samples. Mechanism studies showed that the reaction between NAPO and copper ion could form some kinds of clusters and induce the enhanced LS signals.
Keywords: Light scattering; Copper ion; N; ′,; N; ′-bis (2-Aminophenyl) oxamide; Oxamide ligand; Detection
Spectrofluorimetric determination of benzoimidazolic pesticides: Effect of p-sulfonatocalix[6]arene and cyclodextrins by Natalia L. Pacioni; Valeria N. Sueldo Occello; Márcio Lazzarotto; Alicia V. Veglia (pp. 133-140).
The effect of the addition of a macrocyclic host (H) such as p-sulfonatocalix[6]arene (C6S), native and modified cyclodextrins (CDs), on the fluorescence of benzoimidazolic fungicides (P), like Benomyl (BY) and Carbendazim (CZ), has been studied.The fluorescence ofBY in water at pH 1.000 and 25.0°C was increased in the presence ofC6S, αCD and hydroxypropyl-β-CD (HPCD). The association constants determined by fluorescence enhancement showed weak interactions ( KA∼101 to 102M−1) between the fungicide with bothCDs, whereas they were stronger withC6S ( KA∼105M−1). Molecular recognition ofBY forC6S was mainly attributed to electrostatic interactions, and forCDs to the hydrophobic effect and hydrogen bond formation.On the other hand, the fluorescent behaviour ofCZ in the presence ofC6S at pH 6.994 was interpreted as the formation of two complexes with 1:1 (P:H) and 1:2 (P:H2) stoichiometry, the latter being less fluorescent than the free analyte.Relative fluorescence quantum yield ratios between the complexed and freeBY ( ϕP:H/ ϕP) were 2.00±0.05, 1.40±0.03 and 2.8±0.4 forC6S, αCD andHPCD, respectively. The analytical parameters improved in the presence ofC6S andCDs. The best limit of detection ( LD, ngmL−1) was 17.4±0.8 withHPCD. The proposed method withC6S andHPCD was successfully applied to fortified samples of tap water and orange flesh extract with good recoveries (91–106%) and R.S.D. (≤2%) by triplicate analysis. The method is rapid, direct and simple and needs no previous degradation or derivatization reaction.
Keywords: Benzoimidazolic pesticides; Calixarenes; Cyclodextrins; Macrocyclic cavities; Supramolecular sensors; Fluorescence enhancement
Part-per-trillion level detection of estradiol by competitive fluorescence immunoassay using DNA/dye conjugate as antibody multiple labels by Shengchao Zhu; Qin Zhang; Liang-Hong Guo (pp. 141-146).
Fluorescent organic dyes are currently the standard signal-generating labels used in microarray quantification. However, new labeling strategies are needed to meet the demand for high sensitivity in the detection of low-abundance proteins and small molecules. In this report, a long-chain DNA/dye conjugate was used to attach multiple fluorescence labels on antibodies to improve signal intensity and immunoassay sensitivity. Compared with the 30 base-pair (bp) oligonucleotide used in our previous work [Q. Zhang, L.-H. Guo, Bioconjugate Chem. 18 (2007) 1668–1672], conjugation of a 219bp DNA in solution with a fluorescent DNA binder SYBR Green I resulted in more than sixfold increase in signal intensity, consistent with the increase in bp number. In a direct immunoassay for the detection of goat anti-mouse IgG in a mouse IgG-coated 96-well plate, the long DNA conjugate label also produced higher fluorescence than the short one, accompanied by about 15-fold improvement in the detection limit. To demonstrate its advantage in real applications, the DNA/dye conjugate was employed in the competitive immunoassay of 17β-estradiol, a clinically and environmentally important analyte. The biotin-terminated DNA was attached to biotinylated anti-estradiol antibody through the biotin/streptavidin/biotin bridge after the immuno-reaction was completed, followed by conjugation with SYBR Green I. The limit of detection for 17β-estradiol is 1.9pgmL−1, which is 200-fold lower than the assay using fluorescein-labeled antibodies. The new multiple labeling strategy uses readily available reagents, and is also compatible with current biochip platform. It has great potential in the sensitive detection of protein and antibody microarrays.
Keywords: Estradiol; Competitive immunoassay; Fluorescence; DNA/dye label
Screening of anti-HIV-1 inophyllums by HPLC–DAD of Calophyllum inophyllum leaf extracts from French Polynesia Islands by Frédéric Laure; Phila Raharivelomanana; Jean-François Butaud; Jean-Pierre Bianchini; Emile M. Gaydou (pp. 147-153).
Various pyranocoumarins, calophyllolide, inophyllums B, C, G1, G2 and P, from Calophyllum inophyllum (Clusiaceae) leaves of French Polynesia (Austral, Marquesas, Society and Tuamotu archipelagos) have been determined in 136 leaf extracts using a high pressure liquid chromatography-UV-diode array detection (HPLC–UV-DAD) technique. Results show a wide range in chemical composition within trees growing on eighteen islands. The use of multivariate statistical analyses (PCA) shows geographical distribution of inophyllums and indicate those rich in HIV-1 active (+)-inophyllums. Inophyllum B and P contents (0.0–39.0 and 0.0–21.8mgkg−1, respectively) confirm the chemodiversity of this species within the large area of French Polynesia. The study suggests the presence of interesting chemotypes which could be used as plant source for anti-HIV-1 drugs.
Keywords: Calophyllum inophyllum; Clusiaceae; Tamanu; Inophyllums; Coumarins; Neoflavonoids; Anti-HIV-1 agents; High pressure liquid chromatography-UV-diode array detection; Chemodiversity; Multivariate analyses
Monitoring of morphology and physical properties of cultured cells using a micro camera and a quartz crystal with transparent indium tin oxide electrodes after injections of glutaraldehyde and trypsin by Hyen-Wook Kang; Kazumi Ida; Yuji Yamamoto; Hiroshi Muramatsu (pp. 154-161).
For investigating the effects of chemical stimulation to cultured cells, we have developed a quartz crystal sensor system with a micro charge-coupled device (CCD) camera that enables microphotograph imaging simultaneously with quartz crystal measurement. Human hepatoma cell line (HepG2) cells were cultured on the quartz crystal through a collagen film. The electrode of the quartz crystal was made of indium tin oxide (ITO) transparent electrodes that enable to obtain a transparent mode photograph. Glutaraldehyde and trypsin were injected to the chamber of the cells, respectively. The response of the quartz crystal was monitored and microphotographs were recorded, and the resonance frequency and resonance resistance were analyzed with an F– R diagram that plotted the resonance frequency and resonance resistance. In the case of the glutaraldehyde injection, the cells responded in two steps that included the fast response of the cross-linking reaction and the successive internal change in the cells. In the case of the trypsin injection, the responses included two processes. In the first step, cell adhesion factors were cleaved and the cell structure became round, and in the next step, the cells were deposited on the quartz crystal surface and the surface of the cells was directly in contact with the quartz crystal surface.
Keywords: Quartz crystal; Indium tin oxide electrode; Microphotograph; Chemical stimulation; Glutaraldehyde; Trypsin; Human hepatoma cell line