Ion chromatographic analysis of disinfectant by-products

The complete development of chromatographic methods to determine daily concentrations of the haloacetates (HAs) monochloro- (MCA), dichloro- (DCA), trichloro- (TCA), monobromo- (MBA), dibromo- (DBA), chlorodifluoro- (CDFA) trifluoro- (TFA), dichlorobromo- (DCBA) and chlorodibromoacetates (CDBA) as well as the oxyhalides bromate, chlorate, perchlorate and iodate are presented. This work is divided into seven sections. Firstly, Chapter 1.0 deals with a full understanding of the background to disinfectant by-product formation and analysis, including explanation of all instrumentation required to complete the area of research. Following this, a review of current technologies for the determination of HAs and oxyhalides in modern treated drinking water is discussed. Chapter 2.0 investigates a micro-bore Dionex lonPac AS11-HC as a possible column of choice for ion exchange chromatography of the first seven HAs listed only. The method utilises suppressed conductivity detection with a gradient of sodium hydroxide. Analytical performance characteristics for linearity, reproducibility and limits of detection are presented also. In a brief study, the effect of column temperature was investigated for the developed method with this column and van’t Hoff plots are included here. For determinations of HAs in real drinking water samples, Chapter 3.0 offers solid phase extraction as a possible solution and was investigated using a solid phase extraction cartridge with a stationary phase of hyper-crosslinked polystyrene-divinylbenzene copolymer. Selectivity, percent recovery, capacity and reproducibility studies were carried out on LiChrolut EN cartridges. Under optimised conditions average recoveries for MCA, DCA, TCA, MBA and CDFA spiked in dinking water samples ranged from 62 to 88 %, with an optimum preconcentration factor of 25. The reproducibility of recovery data for the above HAs was found to range from 12 to 29 % based upon six repeat recovery experiments. This method coupled with the IC method in Chapter 2.0 was then applied to the analysis of some real dinking water samples. Improvements in sensitivity are tackled in Chapter 4.0 with addition of Dionex eluent generation and carbonate removal modules. Noise levels decreased by a factor of one third with this new instrumentation. The reproducibility and accuracy of eluent preparation is assessed and compared with manually prepared eluents. The developed method was then applied to the analysis of 5 drinking water samples. Separations with a micro-bore Dionex lonPac AS16 are also shown here. Once more, analytical performance characteristics of linearity, reproducibility and limits of detection are presented along with a brief investigation of the effect column temperature on separation. This new method was then combined with the SPE method in Chapter 2.0 for the determination of HAs in a drinking water sample. Chapter 5.0 deals further with improvements in sensitivity with the use of a monolithic cation exchange type suppressor. Noise levels were dramatically reduced and direct detection of HAs was possible without preconcentration. However, some SPE was carried out along with this IC method and was sensitive to the range of HAs typically expected in drinking water. The effect of doubling the ethylvinylbenzenedivinylbenzene copolymer sorbent was investigated showing a requirement for double the reagent volumes for effective preconcentration and was virtually independent of eluting agent concentration. Chapter 6.0 presents results gathered from UV and MS detectors as alternatives to suppressed conductivity. UV wavelength optimisation, linearity, limits of detection and reproducibility are presented. For IC-MS a suitable interface for coupling the 1C eluate to the electrospray chamber is presented along with optimisation of all parameters for maximum sensitivity to HAs. The developed suppressed conductivity-UV-MS method was then applied to a spiked drinking water sample. Chapter 7.0 discusses the possibility of separating both oxyhalides and HAs on one column with the use of combined temperature and eluent concentration gradients. This chapter discusses in detail the effect of temperature on the separation of HAs and oxyhalides on the AS 16 column and measured versus actual column temperatures are presented. Full optimisation of the dual temperature and eluent concentration gradient for conductivity detection only are presented and applied to a drinking water sample. Following on from this, analytical performance data for reproducibility for n = 30 replicates, LOD and linearity for both suppressed conductivity and mass spectrometric detection is presented. The method was then applied to the analysis of HAs and oxyhalides in a soil sample and a drinking water sample using both detectors

Paired emitter-detector diode detection with dual wavelength monitoring for enhanced sensitivity to transition metals in ion chromatography with post-column reaction

The combination of post-column derivatisation and visible detection are regularly employed in ion chromatography (IC) to detect poorly absorbing species. Although this mode is often highly sensitive, one disadvantage is the increase in repeating baseline artifacts associated with out-of-sync pumping systems. The work presented here will demonstrate the use of a second generation design paired emitter-detector diode (PEDD-II) detection mode offering enhanced sensitivity to transition metals in IC by markedly reducing this problem and also by improving signal noise. First generation designs demonstrated the use of a single integrated PEDD detector cell as a simple, small (15 x 5 mm), highly sensitive, low cost photometric detector for the detection of metals in ion chromatography (IC). The basic principle of this detection mode lies in the employment of two linear light emitting diodes (LEDs), one operating in normal mode as a light source and the other in reverse bias serving as a light detector. The second generation PEDD-II design showed increased sensitivity for Mn(II)- and Co(II)-2-(pyridylazo) resorcinol (PAR) complexes as a result of two simultaneously acquiring detection cells - one analytical PEDD cell and one reference PEDD cell. Therefore, the PEDD-II employs two wavelengths whereby one monitors the analyte reaction product and the second monitors a wavelength close to the isosbestic point. The optimum LED wavelength to be used for the analytical cell was investigated to maximise peak response. The fabrication process for both the analytical and reference PEDD cells was validated by determining the reproducibility of detectors within a batch. The reproducibility and sensitivity of the PEDD-II detector was then investigated using signals obtained from both intra- and inter-day chromatograms

Assessing the reliability of uptake and elimination kinetics modelling approaches for estimating bioconcentration factors in the freshwater invertebrate, Gammarus pulex

This study considers whether the current standard toxicokinetic methods are an accurate and applicable assessment of xenobiotic exposure in an aquatic freshwater invertebrate. An in vivo exposure examined the uptake and elimination kinetics for eight pharmaceutical compounds in the amphipod crustacean, Gammarus pulex by measuring their concentrations in both biological material and in the exposure medium over a 96 h period. Selected pharmaceuticals included two anti-inflammatories (diclofenac and ibuprofen), two beta-blockers (propranolol and metoprolol), an anti-depressant (imipramine), an anti-histamine (ranitidine) and two beta-agonists (formoterol and terbutaline). Kinetic bioconcentration factors (BCFs) for the selected pharmaceuticals were derived from a first-order one-compartment model using either the simultaneous or sequential modelling methods. Using the simultaneous method for parameter estimation, BCF values ranged from 12 to 212. In contrast, the sequential method for parameter estimation resulted in bioconcentration factors ranging from 19 to 4533. Observed toxicokinetic plots showed statistically significant lack-of-fits and further interrogation of the models revealed a decreasing trend in the uptake rate constant over time for rantidine, diclofenac, imipramine, metoprolol, formoterol and terbutaline. Previous published toxicokinetic data for 14 organic micro-pollutants were also assessed and similar trends were identified to those observed in this study. The decreasing trend of the uptake rate constant over time highlights the need to interpret modelled data more comprehensively to ensure uncertainties associated with uptake and elimination parameters for determining bioconcentration factors are minimised

Measurement of the cosmic microwave background polarization lensing power spectrum from two years of POLARBEAR data

We present a measurement of the gravitational lensing deflection power spectrum reconstructed with two seasons of cosmic microwave background polarization data from the POLARBEAR experiment. Observations were taken at 150 GHz from 2012 to 2014 and surveyed three patches of sky totaling 30 square degrees. We test the consistency of the lensing spectrum with a cold dark matter cosmology and reject the no-lensing hypothesis at a confidence of 10.9σ, including statistical and systematic uncertainties. We observe a value of AL = 1.33 ± 0.32 (statistical) ±0.02 (systematic) ±0.07 (foreground) using all polarization lensing estimators, which corresponds to a 24% accurate measurement of the lensing amplitude. Compared to the analysis of the first- year data, we have improved the breadth of both the suite of null tests and the error terms included in the estimation of systematic contamination

Internal delensing of cosmic microwave background polarization B-Modes with the POLARBEAR experiment

International audienceUsing only cosmic microwave background polarization data from the polarbear experiment, we measure B-mode polarization delensing on subdegree scales at more than 5σ significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a means of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments

The impact of provider-initiated (opt-out) HIV testing and counseling of patients with sexually transmitted infection in Cape Town, South Africa: a controlled trial

<p>Abstract</p> <p>Background</p> <p>The effectiveness of provider-initiated HIV testing and counseling (PITC) for patients with sexually transmitted infection (STI) in resource-constrained settings are of particular concern for high HIV prevalence countries like South Africa. This study evaluated whether the PITC approach increased HIV testing amongst patients with a new episode of sexually transmitted infection, as compared to standard voluntary counseling and testing (VCT) at the primary care level in South Africa, a high prevalence and low resource setting.</p> <p>Methods</p> <p>The design was a pragmatic cluster-controlled trial with seven intervention and 14 control clinics in Cape Town. Nurses in intervention clinics integrated PITC into standard HIV care with few additional resources, whilst lay counselors continued with the VCT approach in control clinics. Routine data were collected for a six-month period following the intervention in 2007, on new STI patients who were offered and who accepted HIV testing. The main outcome measure was the proportion of new STI patients tested for HIV, with secondary outcomes being the proportions who were offered and who declined the HIV test.</p> <p>Results</p> <p>A significantly higher proportion of new STI patients in the intervention group tested for HIV as compared to the control group with (56.4% intervention versus 42.6% control, p = 0.037). This increase was achieved despite a significantly higher proportion intervention group declining testing when offered (26.7% intervention versus 13.5% control, p = 0.0086). Patients were more likely to be offered HIV testing in intervention clinics, where providers offered the HIV test to 76.8% of new STI patients versus 50.9% in the control group (p = 0.0029). There was significantly less variation in the main outcomes across the intervention clinics, suggesting that the intervention also facilitated more consistent performance.</p> <p>Conclusions</p> <p>PITC was successful in three ways: it increased the proportion of new STI patients tested for HIV; it increased the proportion of new STI patients offered HIV testing; and it delivered more consistent performance across clinics. Recommendations are made for increasing the impact and feasibility of PITC in high HIV prevalence and resource-constrained settings. These include more flexible use of clinical and lay staff, and combining PITC with VCT and other community-based approaches to HIV testing.</p> <p>Trial registration</p> <p>Controlled trial ISRCTN93692532</p

The geo-constitution: Understanding the intersection of geography and political institutions

This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this record.This paper draws on existing work in the discipline of human geography and cognate fields in order to develop the concept of the ‘geo-constitution’. This concept aims to: (1) highlight the importance of intersections between geography and political institutions in the constitution of government; (2) consider the path-dependent development of political institutions and their impact on statecraft and citizenship; (3) explore the implications of this for political reform. The paper provides an overview of current thinking in political geography and applies the concept of the geo-constitution to the example of devolution and localism in the United Kingdom

Comparative measurement and quantitative risk assessment of alcohol consumption through wastewater-based epidemiology: An international study in 20 cities

Quantitative measurement of drug consumption biomarkers in wastewater can provide objective information on community drug use patterns and trends. This study presents the measurement of alcohol consumption in 20 cities across 11 countries through the use of wastewater-based epidemiology (WBE), and reports the application of these data for the risk assessment of alcohol on a population scale using the margin of exposure (MOE) approach. Raw 24-h composite wastewater samples were collected over a one-week period from 20 cities following a common protocol. For each sample a specific and stable alcohol consumption biomarker, ethyl sulfate (EtS) was determined by liquid chromatography coupled to tandem mass spectrometry. The EtS concentrations were used for estimation of per capita alcohol consumption in each city, which was further compared with international reports and applied for risk assessment by MOE. The average per capita consumption in 20 cities ranged between 6.4 and 44.3. L/day/1000 inhabitants. An increase in alcohol consumption during the weekend occurred in all cities, however the level of this increase was found to differ. In contrast to conventional data (sales statistics and interviews), WBE revealed geographical differences in the level and pattern of actual alcohol consumption at an inter-city level. All the sampled cities were in the "high risk" category (MOE

Making maps of cosmic microwave background polarization for B-mode studies: The POLARBEAR example

Analysis of cosmic microwave background (CMB) datasets typically requires some filtering of the raw time-ordered data. For instance, in the context of ground-based observations, filtering is frequently used to minimize the impact of low frequency noise, atmospheric contributions and/or scan synchronous signals on the resulting maps. In this work we have explicitly constructed a general filtering operator, which can unambiguously remove any set of unwanted modes in the data, and then amend the map-making procedure in order to incorporate and correct for it. We show that such an approach is mathematically equivalent to the solution of a problem in which the sky signal and unwanted modes are estimated simultaneously and the latter are marginalized over. We investigated the conditions under which this amended map-making procedure can render an unbiased estimate of the sky signal in realistic circumstances. We then discuss the potential implications of these observations on the choice of map-making and power spectrum estimation approaches in the context of B-mode polarization studies. Specifically, we have studied the effects of time-domain filtering on the noise correlation structure in the map domain, as well as impact it may haveon the performance of the popular pseudo-spectrum estimators. We conclude that although maps produced by the proposed estimators arguably provide the most faithful representation of the sky possible given the data, they may not straightforwardly lead to the best constraints on the power spectra of the underlying sky signal and special care may need to be taken to ensure this is the case. By contrast, simplified map-makers which do not explicitly correct for time-domain filtering, but leave it to subsequent steps in the data analysis, may perform equally well and be easier and faster to implement. We focused on polarization-sensitive measurements targeting the B-mode component of the CMB signal and apply the proposed methods to realistic simulations based on characteristics of an actual CMB polarization experiment, POLARBEAR. Our analysis and conclusions are however more generally applicable. \ua9 ESO, 2017