In Situ Investigation of Under-Deposit Microbial Corrosion and its Inhibition Using a Multi-Electrode Array System.

Carbon steel pipelines used in the oil and gas industry can be susceptible to the combined presence of deposits and microorganisms, which can result in a complex phenomenon, recently termed under-deposit microbial corrosion (UDMC). UDMC and its inhibition in CO2 ambiance were investigated in real-time using a multi-electrode array (MEA) system and surface profilometry analysis. Maps from corrosion rates, galvanic currents, and corrosion potentials recorded at each microelectrode allowed the visualization of local corrosion events on the steel surface. A marine bacterium Enterobacter roggenkampii, an iron-oxidizing, nitrate-reducing microorganism, generated iron deposits on the surface that resulted in pitting corrosion under anaerobic conditions. Areas under deposits displayed anodic behavior, more negative potentials, higher corrosion rates, and pitting compared to areas outside deposits. In the presence of the organic film-forming corrosion inhibitor, 2-Mercaptopyrimidine, the marine bacterium induced local breakdown of the protective inhibitor film and subsequent pitting corrosion of carbon steel. The ability of the MEA system to locally measure self-corrosion processes, galvanic effects and, corrosion potentials across the surface demonstrated its suitability to detect, evaluate and monitor the UDMC process as well as the efficiency of corrosion inhibitors to prevent this corrosion phenomenon. This research highlights the importance of incorporating the microbial component to corrosion inhibitors evaluation to ensure chemical effectiveness in the likely scenario of deposit formation and microbial contamination in oil and gas production equipment.

Ion suppression; a critical review on causes, evaluation, prevention and applications.

The consequences of matrix effects in mass spectrometry analysis are a major issue of concern to analytical chemists. The identification of any ion suppressing (or enhancing) agents caused by sample matrix, solvent or LC-MS system components should be quantified and measures should be taken to eliminate or reduce the problem. Taking account of ion suppression should form part of the optimisation and validation of any quantitative LC-MS method. For example the US Food and Drug Administration has included the evaluation of matrix effects in its "Guidance for Industry on Bioanalytical Method Validation" (F.D.A. Department of Health and Human Services, Guidance for industry on bioanalytical method validation, Fed. Regist. 66 (100) 2001). If ion suppression is not assessed and corrected in an analytical method, the sensitivity of the LC-MS method can be seriously undermined, and it is possible that the target analyte may be undetected even when using very sensitive instrumentation. Sample analysis may be further complicated in cases where there are large sample-to-sample matrix variations (e.g. blood samples from different people can sometimes vary in certain matrix components, shellfish tissue samples sourced from different regions where different phytoplankton food sources are present, etc) and therefore exhibit varying ion-suppression effects. Although it is widely agreed that there is no generic method to overcome ion suppression, the purpose of this review is to: provide an overview of how ion suppression occurs, outline the methodologies used to assess and quantify the impact of ion suppression, discuss the various corrective actions that have been used to eliminate ion suppression in sample analysis, that is to say the deployment of techniques that eliminate or reduce the components in the sample matrix that cause ion suppression. This review article aims to collect together the latest information on the causes of ion suppression in LC-MS analysis and to consider the efficacy of common approaches to eliminate or reduce the problem using relevant examples published in the literature.

Monitoring the occurrence of PAHs in Irish wastewater effluent.

Polycyclic aromatic hydrocarbons (PAHs) are commonly occurring environmental pollutants, 8 of which have been chosen from the list of priority substances in the EU Water Framework Directive (WFD). The levels of PAHs in the environment are affected by a number of emission factors including anthropogenic activities, population equivalents, and weather, all of which must be taken into account when monitoring levels of PAHs being released into the environment via waste water treatment plant effluent. Effluent samples have been collected from nine different wastewater treatment plants in 2 areas of Ireland (Dublin and Cork) over a period of 3 years (2009-2011), including several weeks of high intensity sampling. Solid phase extraction is used in the sample preparation process with subsequent analysis by gas chromatography with mass spectrometric detection (GCMS). All samples analysed contained the priority PAHs in this study; however levels detected do not exceed environmental quality standards (EQSs). Herein these results are related to a number of key emission factors affecting the levels of PAHs present in wastewater treatment plant effluent. This study aims to complement storm water studies and inform future targeted priority substance monitoring programmes.

Determination of the new anthelmintic monepantel and its sulfone metabolite in milk and muscle using a UHPLC-MS/MS and QuEChERS method.

This is the first paper to report a method for the detection of the new anthelmintic monepantel and its sulfone metabolite in goat's milk and ovine muscle. Samples were extracted and purified using a modified QuEChERS method. A concentration step was included when analyzing in the low µg kg(-1) range. Analysis was carried out by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) in a 13min run time using atmospheric pressure electrospray ionisation in the negative mode (ESI(-)) and multiple reaction monitoring (MRM) scanning. Monepantel (m/z 472) and monepantel-sulfone (m/z 504) both had product ions at m/z 186 and m/z 166. The method has been single-laboratory validated according to the 2002/657/EC guidelines. The mean recovery in milk was 108 and 106% for monepantel and monepantel-sulfone, respectively. The mean recovery in muscle was 109 and 108% for monepantel and monepantel-sulfone, respectively. The coefficients of variation for the within laboratory repeatability and reproducibility were ≤6.4% in milk and ≤14.2% in muscle. The decision limits (CCα) in milk were 2.20 and 2.08 µg kg(-1) for monepantel and monepantel-sulfone, respectively. The decision limits (CCα) in muscle were 771 and 746 µg kg(-1) for monepantel and monepantel-sulfone, respectively.

A dual validation approach to detect anthelmintic residues in bovine liver over an extended concentration range.

This paper describes a method for the detection and quantification of 38 residues of the most widely used anthelmintics (including 26 veterinary drugs belonging to the benzimidazole, macrocyclic lactone and flukicide classes) in bovine liver using two different protocols for MRL and non-MRL levels. A dual validation approach was adopted to reliably quantify anthelmintic residues over an extended concentration range (1-3000 µg kg(-1)). Sample extraction and purification was carried out using a modified QuEChERS method. A concentration step was included when analysing in the low µg kg(-1) range. Rapid analysis was carried out by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), which was capable of detecting residues to <2 µg kg(-1). The method has been single-laboratory validated according to the 2002/657/EC guidelines and met acceptability criteria in all but a few cases. The inclusion of 19 internal standards, including 14 isotopically labelled internal standards, improved accuracy, precision, decision limit (CCα) and detection capability (CCß).

Determination of anthelmintic drug residues in milk using ultra high performance liquid chromatography-tandem mass spectrometry with rapid polarity switching.

A new UHPLC-MS/MS (ultra high performance liquid chromatography coupled to tandem mass spectrometry) method was developed and validated to detect 38 anthelmintic drug residues, consisting of benzimidazoles, avermectins and flukicides. A modified QuEChERS-type extraction method was developed with an added concentration step to detect most of the analytes at <1 microg kg(-1) levels in milk. Anthelmintic residues were extracted into acetonitrile using magnesium sulphate and sodium chloride to induce liquid-liquid partitioning followed by dispersive solid phase extraction for cleanup. The extract was concentrated into dimethyl sulphoxide, which was used as a keeper to ensure analytes remain in solution. Using rapid polarity switching in electrospray ionisation, a single injection was capable of detecting both positively and negatively charged ions in a 13 min run time. The method was validated at two levels: the unapproved use level and at the maximum residue level (MRL) according to Commission Decision (CD) 2002/657/EC criteria. The decision limit (CCalpha) of the method was in the range of 0.14-1.9 and 11-123 microg kg(-1) for drugs validated at unapproved and MRL levels, respectively. The performance of the method was successfully verified for benzimidazoles and levamisole by participating in a proficiency study.

Th1 cytokines promote T-cell binding to antigen-presenting cells via enhanced hyaluronan production and accumulation at the immune synapse.

Hyaluronan (HA) production by dendritic cells (DCs) is known to promote antigen presentation and to augment T-cell activation and proliferation. We hypothesized that pericellular HA can function as intercellular 'glue' directly mediating T cell-DC binding. Using primary human cells, we observed HA-dependent binding between T cells and DCs, which was abrogated upon pre-treatment of the DCs with 4-methylumbelliferone (4-MU), an agent which blocks HA synthesis. Furthermore, T cells regulate HA production by DCs via T cell-derived cytokines in a T helper (Th) subset-specific manner, as demonstrated by the observation that cell-culture supernatants from Th1 but not Th2 clones promote HA production. Similar effects were seen upon the addition of exogenous Th1 cytokines, IL-2, interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). The critical factors which determined the extent of DC-T cell binding in this system were the nature of the pre-treatment the DCs received and their capacity to synthesize HA, as T-cell clones which were pre-treated with monensin, added to block cytokine secretion, bound equivalently irrespective of their Th subset. These data support the existence of a feedforward loop wherein T-cell cytokines influence DC production of HA, which in turn affects the extent of DC-T cell binding. We also document the presence of focal deposits of HA at the immune synapse between T-cells and APC and on dendritic processes thought to be important in antigen presentation. These data point to a pivotal role for HA in DC-T cell interactions at the IS.

Current trends in sample preparation for growth promoter and veterinary drug residue analysis.

A comprehensive review is presented on the current trends in sample preparation for the isolation of veterinary drugs and growth promoters from foods. The objective of the review is to firstly give an overview of the sample preparation techniques that are applied in field. The review will focus on new techniques and technologies, which improve efficiency and coverage of residues. The underlying theme to the paper is the developments that have been made in multi-residue methods and particularly multi-class methods for residues of licensed animal health products, which have been developed in the last couple of years. The role of multi-class methods is discussed and how they can be accommodated in future residue surveillance.

New method for the analysis of flukicide and other anthelmintic residues in bovine milk and liver using liquid chromatography-tandem mass spectrometry.

A liquid chromatographic-tandem mass spectrometric (LC-MS/MS) multi-residue method for the simultaneous quantification and identification of 38 residues of the most widely used anthelmintic veterinary drugs (including benzimidazoles, macrocyclic lactones, and flukicides) in milk and liver has been developed and validated. For sample preparation, we used a simple modification of the QuEChERS method, which was initially developed for pesticide residue analysis. The method involved extracting sample (10 g) with acetonitrile (10 mL), followed by phase separation from water (salting out) with MgSO(4):NaCl (4:1, w/w). After centrifugation, an aliquot of the extract (1 mL) was purified by dispersive solid-phase extraction with MgSO(4) (150 mg) and C(18) (50mg), prior to LC-MS/MS analysis. Two injections of the same extract were required with the LC-MS/MS instrument to cover the 30 electrospray positive and 8 electrospray negative analytes. The limit of quantitation of the method was 5 microgkg(-1) for 37 analytes (and 10 microgkg(-1) for dichlorvos). The method was successfully validated according to the 2002/657/EC guidelines. Recovery of analytes was typically in the 70-120% range, with repeatabilities and reproducibilities typically <15% in milk and <20% in liver.

Comparison of screening methods for antibiotics in beef kidney juice and serum.

Rapid screening tests can be used as part of an efficient program designed to monitor veterinary drug residues in cattle. In this work, three rapid tests designed to screen samples for the presence of antibiotic residues, the Fast Antimicrobial Screen Test (FAST), Premi and Kidney Inhibition Swab (KIS) tests, were compared using beef kidney juice and serum samples. In order to provide a realistic assessment, potentially incurred samples of beef kidney juice and serum were obtained from 235 carcasses which had been retained by inspectors in a processing plant for further testing. In addition, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was conducted on these samples to identify what antibiotics were present, if any, and their levels. The comparison of the three rapid screening test results with those from LC-MS/MS analysis allowed for a more complete comparison of the relative sensitivity of these analytical methods, as well as valuable information on false positive and negative response rates.