Flow injection methods of sample introduction for ICP-MS

This thesis is concerned with the application offlow injection techniques for on-line sample preparation for inductively coupled plasma mass spectrometry (ICP-MS). A comprehensive introduction to ICP-MS and the various sample introduction methods which have been applied for the technique is presented in Chapter 1. The advantages and disdvantages of the different sample introduction procedures are also considered and discussed. Since ICP-MS is a highly sensitive technique for multi-element analysis at trace levels, there are few methods which can compete with it. The methods which are available are compared with ICP-MS and the advantages and disadvantages of each are discussed in the context of the available literature.The second chapter contains a detailed review of the various reagents which have been used for the selective retention of trace element ions from solutions containing high concentrations of so called 'matrix species' (e.g. Na, Ca, K and Mg). The use of ion-exchange and chelating reagents for trace analyte retention is discussed together with an appraisal of the properties and applications of activated alumina as either a cation or anion exchanger. Most ion-exchange and chelating reagents consist of an organic functional group covalently immobilised onto a support material. The properties of polymer and controlled pore glass support materials are discussed with respect to their behaviour in on-line systems.In Chapter 3, the use of the chelating reagent 8-hydroxyquinoline, covalently immobilised onto controlled pore glass, for on-line preconcentration and matrix separation with ICP-MS detection, is described. A manually operated manifold, directly coupled to the ICP-MS, was developed for this work. The optimisation and analytical performance ofthis manifold is evaluated for Ti4+, V (as VO2+), Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+, Ce3+ and Pb2+ in saline matrix samples and reference materials. Following the development of the manual manifold described in Chapter 3, the construction of an automated preconcentration I matrix separation manifold, using a commercially available liquid handling system is described in Chapter 4. For this work, a novel iminodiacetate chelating reagent, immobilised onto a controlled pore glass support, was used for analyte retention. An initial manifold design is considered, followed by a refined version of the system, which is optimised for the retention of Mn2+, V (as VO2+), Co2+, Ni2+, Cu2+,Zn2+, Ag +, Cd2+, Ce3+, Pb2+ and U (as UO2+). The performance of the novel iminodiacetate chelating material is evaluated for the analysis of two saline reference waters and some saline industrial effluent samples.In Chapter 5, the effects of humic material in the sample on the on-line retention of Ti4+, V (as VO2+ ), Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+, Ce3+, Pb2+ and U (as UO2+) by the iminodiacetate reagent is explored. Humic material, which arises from soil and decaying vegetable matter, exists in fresh and saline waters at concentrations of typically 1 - 50 ppm. This complex material is composed of a number of different organic molecules which contain a variety of functional groups capable of forming chelates with the analytes of interest in the sample. For this reason, interference effects are expected to occur with increasing levels of humic material in the sample. The effect of increasing levels of elements which have an affinity for the iminodiacetate reagent is examined in terms of the retention efficiency of the analytes of interest.In Chapter 6, the subject of microwave digestion for sample preparation is studied. This work initially involves assessing the efficiency of a simple nitric acid digestion for the digestion of selected reference materials in a batch system. The study continues with an evaluation of on-line microwave digestion with off-line analysis using ICP-MS and concludes with an investigation into the feasibility of directly coupling the on-linemicrowave digestion system to the ICP-MS instrument. Finally, in Chapter 7, the general conclusions to the thesis and suggestions for future research are presented

Optimisation of a current generation ICP-QMS and benchmarking against MC-ICP-MS spectrometry for the determination of lead isotope ratios in environmental samples

© 2018 The Royal Society of Chemistry. Novel ANOVA methodology was used to benchmark ICP-QMS against MC-ICP-MS for Pb isotope ratios, demonstrating "fitness-for-purpose" in environmental source apportionment. The precision and accuracy of lead (Pb) isotope measurements obtained from quadrupole-based mass spectrometers (ICP-QMS) are considered to be limited by a number of factors originating in different components of the instruments. In this study, experimental and instrumental protocols were optimised for determining lead isotope ratios in urban soil digests. Experimental measures included individual dilution of all samples and isotopic standards (SRM-981, NIST) to a single Pb concentration intended to produce an intensity which was high enough to negate blanks and interferences but low enough to ensure the detector operated only in pulse counting mode. Instrumental protocols included batch dead time correction, optimisation of dwell time and the number of scans employed and correction of mass discrimination by sequential application of both internal ( 203 Tl/ 205 Tl ratio) and external (SRM-981, NIST) standards. This optimised methodology was benchmarked against multi-collector mass spectrometer (MC-ICP-MS) measurements of Pb isotope ratios using replicate digest solutions of the same soil; but after these had been subjected to Pb separation using an ion-exchange procedure. On the assumption that MC-ICP-MS measurements are more accurate, small additive and multiplicative differences were observed in only the 4 th decimal place. ANOVA was used to compare the precisions of the two techniques demonstrating equal precisions c. 0.08% for 207 Pb/ 206 Pb, suggesting a sample heterogeneity limitation. By contrast, for 207 Pb/ 204 Pb, the worst-case ratio, ICP-QMS had a 10-fold poorer precision, despite negligible interference from 204 Hg, implying an instrumental limitation. The study concludes that ICP-QMS can provide valuable source apportionment information for most Pb isotope ratios but further efforts should focus on improving assay of the 207 Pb/ 204 Pb ratio

Associations Between Radiation Oncologist Demographic Factors and Segmentation Similarity Benchmarks: Insights From a Crowd-Sourced Challenge Using Bayesian Estimation

PURPOSE: The quality of radiotherapy auto-segmentation training data, primarily derived from clinician observers, is of utmost importance. However, the factors influencing the quality of clinician-derived segmentations are poorly understood; our study aims to quantify these factors. METHODS: Organ at risk (OAR) and tumor-related segmentations provided by radiation oncologists from the Contouring Collaborative for Consensus in Radiation Oncology data set were used. Segmentations were derived from five disease sites: breast, sarcoma, head and neck (H&N), gynecologic (GYN), and GI. Segmentation quality was determined on a structure-by-structure basis by comparing the observer segmentations with an expert-derived consensus, which served as a reference standard benchmark. The Dice similarity coefficient (DSC) was primarily used as a metric for the comparisons. DSC was stratified into binary groups on the basis of structure-specific expert-derived interobserver variability (IOV) cutoffs. Generalized linear mixed-effects models using Bayesian estimation were used to investigate the association between demographic variables and the binarized DSC for each disease site. Variables with a highest density interval excluding zero were considered to substantially affect the outcome measure. RESULTS: Five hundred seventy-four, 110, 452, 112, and 48 segmentations were used for the breast, sarcoma, H&N, GYN, and GI cases, respectively. The median percentage of segmentations that crossed the expert DSC IOV cutoff when stratified by structure type was 55% and 31% for OARs and tumors, respectively. Regression analysis revealed that the structure being tumor-related had a substantial negative impact on binarized DSC for the breast, sarcoma, H&N, and GI cases. There were no recurring relationships between segmentation quality and demographic variables across the cases, with most variables demonstrating large standard deviations. CONCLUSION: Our study highlights substantial uncertainty surrounding conventionally presumed factors influencing segmentation quality relative to benchmarks

A survey on planar IMRT QA analysis

Quality assurance (QA) systems for intensity-modulated radiation therapy (IMRT) have become standard tools in modern clinical medical physics departments. However, because formalized industry standards or recommendations from professional societies have yet to be defined, methods of IMRT QA analysis vary from institution to institution. Understanding where matters stand today is an important step toward improving the effectiveness of IMRT QA and developing standards. We therefore conducted an IMRT QA survey. This particular survey was limited to users of an electronic two-dimensional diode array device, but we took care to keep the questions as general and useful as possible. The online survey polled institutions (one survey per institution) on a collection of questions about methods of IMRT QA. The topics were general to the IMRT QA analysis methods common to all IMRT systems; none of the questions was vendor- or product-specific. Survey results showed that a significant proportion of responding institutions (32.8%) use the single-gantry-angle composite method for IMRT Q

Evaluation of Detector Dead Time Calculation Models for ICP-MS.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Certification of the Lead Mass Fraction in Wine for Comparison 16 of the International Measurement Evaluation Programme.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Comparative Performance Study of ICP Mass Spectrometers by Means of U "Isotopic Measurements".

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel