Pre-analysis Treatment Research Articles

Utilizing metal cation reactions with carbonyl sulfide to remove isobaric interferences in tandem inductively coupled plasma mass spectrometry analyses

Carbonyl sulfide (OCS) was used as a reaction gas to investigate gas phase metal (M+) ion-molecule reactions using the Agilent 8900 inductively coupled plasma tandem mass spectrometer (ICP-MS/MS) to yield insight on how this gas may be used to remove isobaric interferences in analytical measurements. The experimental work was paired with density functional theory (DFT) calculations of the reaction enthalpy to predict whether M+ will react with OCS. A multi-element standard containing 46 elements ranging from 9 to 208 u was analyzed in the presence and absence of OCS. When a reaction was observed, the dominant product was the sulfide (MS+). Oxide products were also observed for many M+ but formation was less efficient with OCS than previously observed with other reaction gases. This is likely due to the weaker OC-S bond that makes MS+ formation more favorable. Increasing the flow rate from 0.1 to 0.2 mL/min (corresponding to a change in reaction gas pressure from 0.35 to 0.53 Pa (2.6 to 4.0 mTorr)) generally resulted in greater MS+ production, including the secondary product MS2+ for a few cations. The early lanthanide series ions (La+, Ce+, Pr+ and Nd+) produced greater quantities of MO+ at the higher pressure, although MS+ products were still the dominant product. The DFT-predicted reaction enthalpies were consistent with the observed sulfide formation, with an accuracy >90%; however, model predictions were less accurate for the minor and higher order products (< 77% for MO+). The work presented here continues a systematic study of ion-molecule reactions in ICP-MS/MS to understand and develop new and novel ways to analyze complex mixtures with minimal pre-analysis treatment.

Quality Control and Pre-Analysis Treatment of the Environmental Datasets Collected by an Internet Operated Deep-Sea Crawler during Its Entire 7-Year Long Deployment (2009-2016).

Deep-sea environmental datasets are ever-increasing in size and diversity, as technological advances lead monitoring studies towards long-term, high-frequency data acquisition protocols. This study presents examples of pre-analysis data treatment steps applied to the environmental time series collected by the Internet Operated Deep-sea Crawler “Wally” during a 7-year deployment (2009–2016) in the Barkley Canyon methane hydrates site, off Vancouver Island (BC, Canada). Pressure, temperature, electrical conductivity, flow, turbidity, and chlorophyll data were subjected to different standardizing, normalizing, and de-trending methods on a case-by-case basis, depending on the nature of the treated variable and the range and scale of the values provided by each of the different sensors. The final pressure, temperature, and electrical conductivity (transformed to practical salinity) datasets are ready for use. On the other hand, in the cases of flow, turbidity, and chlorophyll, further in-depth processing, in tandem with data describing the movement and position of the crawler, will be needed in order to filter out all possible effects of the latter. Our work evidences challenges and solutions in multiparametric data acquisition and quality control and ensures that a big step is taken so that the available environmental data meet high quality standards and facilitate the production of reliable scientific results.

Aging three-spined sticklebacks Gasterosteus aculeatus: comparison of estimates from three structures.

In order to assess the accuracy and reliability of age estimates from calcified structures in the three-spined stickleback Gasterosteus aculeatus, we evaluated intra and inter-reader repeatability from three structures: otoliths, gill covers and pelvic spines). Average age estimates were also compared between the structures. The overall intra-reader repeatability of age estimates were highest for otoliths (69%), lowest for gill covers (53%) and intermediate for spine cross-sections (63%). Although four of the seven readers had the highest intra-reader repeatability score for spine cross-sections, the inter-reader variance in this structure was much higher than in others. Otoliths were the easiest in terms of their pre-analysis treatment and exchange of materials (as digital images) between readers. In addition, otoliths are more well-studied compared with the other structures with respect to their development through ontogenesis; hence, age estimates based on otoliths should be the most reliable. Therefore, our recommendation is that whenever possible, analysis of otoliths should be the preferred approach for aging G. aculeatus.

How long is enough: CO2 -H2 O equilibration for δ(18) O analysis in saline formation waters?

The equilibration of H2 -H2 O and CO2 -H2 O is a commonly used method for δ(2) H and δ(18) O analyses in water. Problems with these analyses of formation water include the presence of petroleum contaminants and the slow exchange of oxygen isotopes between CO2 gas and the saline waters collected from petroleum exploration and production wells. Therefore, it is crucial to understand whether isotopic equilibrium between water and CO2 has been reached, how long it takes, and how to deal with contaminants. This study investigates how long it takes to reach isotopic equilibrium between gas and hypersaline brine, and how to deal with petroleum-contaminated formation water, in order to produce good quality δ(2) H and δ(18) O data. The δ(2) H and δ(18) O values of six natural waters with a variety of salinities were determined by isotope ratio mass spectrometry after different periods of H2 and CO2 equilibration with the samples. Hydrocarbon and non-hydrocarbon gases present in formation brines were pre-treated prior to the H2 - and CO2 -H2 O interaction to minimize their interference with the isotope analyses. Water samples with different salinities required different times for the oxygen isotopes to reach equilibrium. Salinity does not affect the equilibration of H2 with saline brines. Hydrocarbon gases present in formation waters can interfere with the isotope analysis, but this can be minimized with pre-analysis treatment. The described procedures should be applied for stable hydrogen and oxygen isotope analyses in waters with high salinities and petroleum contaminants. In particular, waters collected from petroleum exploration and production wells, and from evaporative environments, should go through these procedures. Copyright © 2016 John Wiley & Sons, Ltd.

The comparison and application of silicone casting material for trauma analysis on well preserved archaeological skeletal remains

The analysis of tool marks in bone is important in both archaeological and forensic examination to enhance our knowledge of the funerary context. Some tool mark characteristics are difficult to identify macroscopically and often additional imaging equipment is needed. Microscopic analysis of trauma has proven to be beneficial in determining individual characteristics of tool marks. However, due to the sample size restrictions or pre-analysis treatment of the sample, microscopy is not commonly used to analyse trauma on archaeological skeletal remains. The creation of casts of the tool marks is an obvious solution, but often the perceived risk of damaging the skeletal remains deters its use. Casting materials are used by many forensic scientists but there is little mention within the literature on the effectiveness of using these products to record tool marks on archaeological skeletal remains. This research used three commonly used silicone-based casting products, Xantopren L blue, Mikrosil, and Alec Tiranti RTV putty silicone, to record tool marks in modern and archaeological bones. Forty-five casts were analysed to identify which product is the least destructive and most effective in recovering tool characteristics from the skeletal remains. The results show that all of the products tested were able to replicate blade trauma and allowed the affected area to be analysed in greater detail. A comparison of the application and the effect of the products on bone revealed that Alec Tiranti putty was the best product to use on well preserved archaeological remains. Although the creation of casts using Alec Tiranti putty took longer in comparison to the other products, it did not damage the cortex of archaeological bone whereas this was not the case with Xantopren and Mikrosil. To demonstrate these results on human skeletal remains, Alec Tiranti putty was used to cast peri-mortem modification on an Iron Age cranium from Peterborough, Cambridgeshire. These casts were non-destructive and allowed for previously unidentified tool marks to be discovered.

The effects of acidification on the stable isotope signatures of marine algae and molluscs

Carbon ( 13C) and nitrogen ( 15N) stable isotope analysis has become increasingly important in the study of energy flow and tropho-dynamics in many ecosystems. Prior to analysis, samples are often pre-treated with acids to remove inorganic carbonates which may bias the results. The effects of pre-analysis acidification on isotopic values are, however, still poorly understood for marine producers (e.g. algae and cyanobacteria), and consumers (e.g. molluscs), which may confound the comparability of different studies. In this study, such effects (untreated vs. decalcified samples) were examined at two different sampling periods (summer and winter). Acidification did not seem to affect the isotopic composition of consumers, but reduced both δ 13C and δ 15N of producers. This effect was consistent for the two sampling periods, although both producers and consumers had more enriched δ 13C and δ 15N values in summer. Acidification had the most distinct, negative effect on the isotopic values of samples which had low carbonate contents. It is, therefore, important to be aware of temporal variations in sample isotopic values and especially the effects of sample treatment when attempting to compare different studies. As an attempt to standardize protocols, it is recommended that only acid-washing carbonate-rich samples is adopted as the most appropriate pre-analysis treatment.

Separation and Quantification of Tl(I) and Tl(III) in Fresh Water Samples

The two oxidation states of thallium, Tl(I) and Tl(III), were quantified by IC-ICP-MS using complexation of Tl3+ with DTPA (penta-carboxymethyl-diethylenetriamine) and separation on a cation exchange column according to a modification of the method devised by Coetzee et al. In order to avoid successively lowered separation efficiency and loss of resolution during a run, a gradient elution was made using HCl instead of HNO3. With an ultrasonic nebuliser instead of a V-groove nebuliser the limit of detection for Tl(I) and Tl(III) could be lowered from 25 ng/L and 3.0 ng/L to 9.0 ng/L and 0.7 ng/L, respectively, which is adequate for many fresh water systems. The stability of Tl(III) in acidic solutions was found to be concentration dependent, with an initially high reduction rate of Tl(III). Exposure of the sample to light further increased the reduction rate. Addition of DTPA (0.01 mM) and acid (HNO3, 1%) to a sample with 1 μg/L Tl(III) stabilised the Tl(III) content for at least 48 h. Analysis of field samples showed that only acidification is inadequate to maintain the original distribution of Tl(I) and Tl(III). Internal calibration (standard addition) and correction of the analytical signal (205Tl) with a non-ionic internal standard (11B) yielded almost quantitative recoveries of both Tl(I) and Tl(III). A scheme for field sample preparation is proposed, including sampling, storage and pre-analysis treatment.

Comparison of two methods for the determination of water-soluble organic carbon in atmospheric particles

In this work, we have compared two methods for the determination of water-soluble organic carbon (WSOC) in ambient aerosols, one based on a total organic carbon analyzer (TOC) and the other based on an aerosol carbon analyzer (ACA). The two instruments entail different pre-analysis treatment of aerosol water extracts. Standard compounds spiked onto filters showed satisfactory recovery ranging from 75% to 105% by the two methods, demonstrating that the extraction procedures and subsequent pre-analysis pre-treatment are quantitative in both methods. Measurements of standard compounds and aerosol samples show that the two methods give equivalent results by paired t-test. The TOC method offers a limit of detection (LOD) of 2.6 μg/sample, whereas the ACA method gives a LOD of 4.8 μg/sample. Acid treatment to remove carbonate carbon was found unnecessary for the determination of WSOC in PM2.5 aerosols. Although the sample treatment procedures and the detection limits of these two methods are different to some extent, both are suitable for the determination of WSOC in aerosol samples. The TOC method has the advantages of requiring less time in sample pre-treatment and offering slightly lower detection limit. The TOC instruments also have the additional advantage of automated sample analysis while the ACA instruments require manual operation.

European soil sampling guidelines for soil pollution studies

The soil sampling guidelines used in European countries (ESSG), as kindly provided by the national institutions which participated in the project, have been recorded, studied, evaluated and presented in this paper. The aim has been to ascertain what soil sampling guidelines exist in Europe; to detect similarities and differences (comparable results), advantages and deficiencies; to identify incompatible strategies and evaluate how methodologies might affect data quality; to investigate sources of deviations or uncertainties; to improve comparability and representativeness of soil sampling; to investigate the need for harmonised sampling guidelines; and to develop suggestions for standard operating procedures (SOP). Soil sampling guidelines throughout Europe differ as to whether they are applied by law, or used throughout the country. In some countries these are ISO/DIS related or based ( ISO 10381-1, 1995; ISO 10381-2, 1995), or are produced by a scientific society or a standardisation body. As far as sampling strategy is concerned, not all sampling guidelines clearly describe the sampling scale, the specifications for contamination risk precautions, the sampling plan and protocol structure and the pre-analysis treatment of the soil samples. The purpose for sampling, in descending order of frequency, is soil pollution, soil fertilisation, general soil monitoring, background risk assessment, or else it is not specified. The majority of countries do not sample the top organic matter separately. Sampling depth is either related to the morphogenetic horizon or to ad hoc sampling depth, which is not specified in all cases. They suggest mass- and volume-related soil sampling, while the sampling pattern is not presented in all national guidelines. The criteria for area, site, unit, sub-unit, and point selection are mainly based on pedology and land use, following the history and pre-screening information or geology, or is site related. Some guidelines suggest the division of sampling units into sub-units. The sampling pattern is mainly grid sampling, grid and random sampling, or not mentioned. Sampling density inside the sampling unit either varies greatly or it is not mentioned, while the size of the sampling unit varies widely. Most guidelines require the collection of composite instead of simple samples, while some prefer sampling soil profiles. In the European SSG many technical details and steps are either not defined or vary, while in the pre-analysis treatment quality assurance (QA) and quality control (QC) approaches are used either both in the lab and in the field, or only in the field, or are not mentioned. The common points and the points in which harmonisation could be started or achieved are discussed.

Levels of cadmium in bone tissue (femur) of industrially exposed workers - A reply

Interest in the biological effects of trace metals has initiated a considerable number of investigations of their concentrat ions and distribution in the human body. Some tissues or body fluids have been extensively studied due to accessibility to analysis wi thout serious interferences from pre-analysis treatment. The mineralised tissues present a series of difficulties in the analysis of main and trace elements. Consequently, reliable data on the concentration and distribution of important heavy metals as cadmium and mercury are scarce (e.g. Iyengar et al., 1978). It is therefore of utmost importance that studies are initiated in this respect so as to present reliable background data for different kinds of mineralised tissues in the human body. In the following is presented a reply to and discussion of Brown et al.'s (1981) comments on our paper Levels of Ant imony, Arsenic, Cadmium, Copper, Lead, Mercury, Selenium, Silver, Tin and Zinc in Bone Tissue of Industrially Exposed Workers (Lindh et al., 1980).

Suspended particulate matter: collection by pressure filtration and elemental analysis by thin-film X-ray fluorescence

Thin-film X-ray fluorescence, using an energy dispersive system, allows for the determination of the major rock-forming elements (Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe) in suspended phases of marine particulate matter. The method is rapid, non-destructive, entails no pre-analysis treatment of the sample, and requires as little as 25 to 50 μg of sample. Particulate samples for this and other analyses are filtered quickly and without post-collection transfer of the water sample by a simple pressure filtration technique employing standard plastic sampling bottles.