Brian Kinsella

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.

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.

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.

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 (CCβ).

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.

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 goats 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.

Occurrence of Selected Metals in Wastewater Effluent and Surface Water in Ireland

ABSTRACT Metals occur naturally in the environment and as constituents of the Earth’s crust. They have many uses, and metals such as iron, copper, and zinc are widely used in industries. Elevated levels of metals in the environment also occur as a result of human activities (municipal, residential, and traffic–related activities). A list of 15 metals chosen for this study included priority substances and those listed in the European Union Water Framework Directive 2000/60/EC. The concentrations of heavy metals in the environment are affected by several factors that must be taken into account when monitoring heavy metals released into the environment through wastewater treatment plants (WWPTs). This work examines the concentrations of metals found in WWPTs and the effects of treatment type on dissolved metal concentrations. Effluent samples were collected from the outflow of nine WWPTs in Dublin and Cork, Ireland from July 2009 to June 2011. All samples were found to contain priority metals that exceeded environmental quality standards in several cases. We present the frequency of occurrence and concentrations of metals in effluents of studied WWPTs and discuss relationships between the occurrence of heavy metals, the influence of factors such as industrial inputs, levels of treatment at WWPTs, and percentage urban area in an agglomeration. The results of this study are an indication that WWPTs may be contributing to the high levels of heavy metals found at discharge points back into river systems.

Development of a Risk Index for Use in Water Quality Monitoring

Risk indices have recently emerged as an effective and efficient tool in the area of water quality monitoring with new indices taking in vast quantities of data and facilitating the development of more targeted water monitoring programs. With the Water Framework Directive demanding that monitoring requirements for a list of priority substances be met, achieving ‘good’ status in all water bodies by 2015, there is a strong need for improved monitoring programmes. In order to improve future monitoring programmes by making the process more ‘targeted’ a simple risk-based index for the occurrence of priority substances in wastewater treatment plant effluent was devised. This index was developed through the collection of an extensive list of documents relating to priority substance emission factors. These included wastewater treatment licence applications, trade effluent licences, traffic data, rainfall data, and census data. It was found that by relating data from each of these sources to historic occurrence data, it was possible to conceptualise and develop a ranking of risk of occurrence of priority substances. Validation of this index was carried out using data from a 24-month sampling plan at nine sites in two counties in Ireland representative of different pressures, i.e. agricultural, industrial and domestic. This work has allowed for the compilation of a large dataset of emission factor and priority substance occurrence in Ireland where none previously existed. For the first time, a risk-based index has been developed for Irish wastewater treatment plant effluents. Together, the index and dataset can be used by policy makers and inform the development of future priority substance monitoring programmes.

A robust analytical method for the determination of pesticide residues in wastewater

Much research has been carried out on the analysis of chemical residue pollutants in the aquatic environment including drinking water, lakes, rivers, ground water, estuaries and coastal zones. However, few studies report the analysis of wastewater for the presence of chemical pollutants, including pesticides, even though this is an important issue because wastewater can be a major point source input of pollutants to the environment. The aim of this research was to develop an analytical method for the detection and confirmation of 13 pesticide residues in wastewater. All 13 pesticides are included on the EU priority pesticides list outlined the Water Framework Directive (2000/60/EC). Pesticides were extracted from wastewater using solid-phase extraction (SPE) on polymeric cartridges containing hydrophilic and lipophilic functional groups capable of retaining pesticides with diverse physico-chemical properties. The pesticides were eluted with organic solvent and concentrated by evaporation prior to analysis by liquid-chromatography coupled to tandem mass spectrometry (LC-MS/MS) operated in electrospray ionization (ESI) mode. LC-MS/MS runs both positive and negative modes were carried out for each sample. Recovery of the 13 pesticides was typically greater than 80%. All 13 pesticides were found to be linear over the concentration range 1 to 100 ng mL−1 with linear regression values (R2) typically greater than 0.99. The limit of detection (LOD) of the method was 1 ng mL−1, except for chlorpyrifos (5 ng mL−1). 11 isotopically labelled internal standards were included in the method to improve accuracy and precision. The final method was used to analyse wastewater samples collected from seven WWTPs over a period of four months. Several pesticides were found to be present in the samples tested at each WWTP. A total of 204 samples were collected from 68 sampling events between 2011 and 2012. Exceedances were detected at each of the seven sites in this study, with diuron, atrazine and simazine most frequently occurring.