Highly integrated flow assembly for automated dynamic extraction and determination of readily bioaccessible chromium(VI) in soils exploiting carbon nanoparticle-based solid-phase extraction

On- and off-line analysis by ICP-MS to measure the bioaccessible concentration of elements in PM10 using dynamic versions of the simplified bioaccessibility extraction test

Two dynamic versions of the simplified bioaccessibility extraction test (SBET) were developed-an off-line procedure and an on-line procedure coupled directly to ICP-MS. Batch, on-line, and off-line procedures were applied to simulated PM₁₀ samples prepared by loading NIST SRM 2711A Montana II Soil and BGS RM 102 Ironstone Soil onto 45-mm TX40 filters widely used in air quality monitoring. Three real PM₁₀ samples were also extracted. A polycarbonate filter holder was used as an extraction unit for the dynamic procedures. Arsenic, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined in the extracts using an Agilent 7700 × ICP-MS instrument. The residual simulated PM₁₀ samples following application of the SBET were subjected to microwave-assisted aqua regia digestion and a mass balance calculation performed with respect to digestion of a separate test portion of the SRM. Leachates were collected as subfractions for the off-line analysis or continuously introduced to the nebuliser of the ICP-MS for the on-line analysis. The mass balance was generally acceptable for all versions of the SBET. Recoveries obtained with the dynamic methods were closer to pseudototal values than those obtained in batch mode. Off-line analysis performed better than on-line analysis, except for Pb. Recoveries of bioaccessible Pb relative to the certified value in NIST SRM 2711A Montana II Soil (1110 ± 49 mg kg^-1) were 99, 106, and 105% for the batch, off-line, and on-line methods, respectively. The study demonstrates that dynamic SBET can be used to measure bioaccessibility of potentially toxic elements in PM₁₀ samples.

An automatic flow-through system for exploration of the human bioaccessibility of endocrine disrupting compounds from microplastics

This article reports on the first attempt towards investigating the leaching rates in the human gastrointestinal (GI) tract of plastic-borne contaminants that can be ingested accidentally using physiologically relevant body fluids. Oral bioaccessibility under fasted and fed states was determined in dynamic mode exploiting an automatic flow setup. The flow system is able to mimic the fast uptake of the released species from the polymeric matrix by absorption in the human digestive system by the in-line removal of the leached species. Complex GI extractants based on the Unified Bioaccessibility Method (UBM, fasted state) and Versantvoort test (fed-state) were brought through a microplastic-loaded metal microcolumn for semi-continuous leaching of plasticizers (phthalic acid ester congeners) and monomer/antioxidant species (bisphenol A, BPA) followed by in-line solid-phase extraction and clean-up of GI extracts prior to liquid chromatography analysis. The temporal extraction profiles were fitted to a first-order kinetic model for the estimation of maximum bioaccessibility pools and apparent leaching rates. Among all studied contaminants, only BPA, dimethylphthalate and diethylphthalate were appreciably released under dynamic GI conditions from high-density polyethylene pellets (average size of 110 μm), with average bioaccessibility values spanning from 51 to 84% and 48 to 87% for UBM and Versantvoort methods, respectively. No statistically significant differences in oral bioaccessibility pools were found under fed- and fasted-state dynamic extractions. The apparent kinetic constants under the fed state were greater by ≥30% as a consequence of the effect of the larger amounts of bile salts and digestive enzymes in the Versantvoort test on the leaching rates. The estimated average daily intake, in which bioaccessibility data are contemplated, indicated that plastic materials exceeding 0.3% (w/w) BPA might pose real risks to human health.

Complementary assessment of As, Cu and Zn environmental availability in a stabilised contaminated soil using large-bore column leaching, automatic microcolumn extraction and DGT analysis

Soil pollution with trace elements is a concerning issue worldwide. Monitoring of soil pollution and remediation protocols need still from valid complementary analytical approaches able to detect changes in speciation and lability of metals in soils (e.g. stabilization or mobility). In this work, we compare three different analytical approaches to assess potential changes in environmental availability of Cu, As and Zn in a Mediterranean polluted soil that was amended with different combinations of iron sulphate and alkaline paper sludge waste. The studied methods were: (i) a standard large-bore flow-through column system (macrocolumn), (ii) an automatic dynamic flow-through microcolumn extraction system, and (iii) the diffusive gradients in thin gels technique (DGT). The three analytical approaches tested showed immobilization of Zn and Cu in contaminated mine soils after co-application of paper sludge and iron sulphate, but they differ quantitatively in terms of As mobility. Interconversion between oxidation states of inorganic As is observed to occur to a larger extent in macrocolumn. Because this may only occur in very specific Mediterranean scenarios (i.e. organic matter application to intermittently flooded mine soils), macrocolumn extraction procedures might not appropriately mimic the environmental availability of As in soils with organic amendments (e.g., paper sludge waste). Microcolumn leaching is the fastest screening tool to ascertain the efficiency of chemical amendments, but DGT is a good alternative with less technical demands.

3D printed device for the automated preconcentration and determination of chromium (VI)

A 3D printed device for the fully automated disk-based solid-phase extraction (SPE) of Cr (VI) from water samples has been fabricated. The compatibility of the use of organic solvents for analyte elution with 3D printed flow devices based on polymers fabricated using stereolithograph​y has been evaluated. The developed methodology comprises the complexation of Cr (VI) with 1, 5-diphenylcarbazide (DPC) in acidic medium and the subsequent retention of the complex in a SBD-RPS disk contained within the 3D printed device. A multisyringe flow injection analysis system with online spectrophotometric detection has been used for the automation of the method. The fabricated 3D printed device integrates the different components of the flow analysis manifold, including connectors and mixers, being a powerful approach towards the reproducible construction of highly integrated flow-based manifolds. The extracted Cr (VI)-DPC complex is eluted with a mixture of methanol- sulfuric acid and quantified at 540 nm. The effect on the analytical signal and the optimization of variables were evaluated using multivariate and univariate techniques. A detection limit of 1 ng Cr (VI) and a linear working range of 3.2-600 ng Cr (VI) were obtained using a sample volume of 2 ml. The intra-day and inter-day RSDs were 4.8% (10 µg L^-1, n = 12) and 3.4% (n = 5, different day with a different disk), respectively. The applicability of the fabricated 3D printed device has been proved by the determination of Cr (VI) in groundwater, surface water and leachates.

New Insights into the Reliability of Automatic Dynamic Methods for Oral Bioaccessibility Testing: A Case Study for BGS102 soil

Dynamic flow-through extraction is attracting a great deal of attention for real-time monitoring of the bioaccessible fraction of metal species in environmental solid substrates compared to its batchwise manual counterparts. There is however a lack of studies on the harmonization and validation of in vitro dynamic methods for physiologically based extraction tests against in vivo bioavailability methods. This work is aimed at evaluating the reliability of dynamic flow-through extraction methods for estimation of oral bioaccessible fractions of Cu, Zn, Pb, Ni, Cr, and As under worst-case extraction conditions in the gastric compartment based on the BGS102 guidance soil using the in vivo validated Unified BARGE (UBM) test, commonly performed under batchwise mode. Good overall agreement between batch and dynamic UBM results was obtained for the tested elements, except for Pb, as a consequence of the slow leaching kinetics identified with the dynamic method and the contribution of readsorption phenomena in the course of the gastric digestion. Metal-soil phase associations and their relationship with gastric bioaccessible fractions were elucidated using the so-called Chemometric Identification of Substrates and Element Distributions method based on sequential extraction with a variety of chemicals of increasing acidity as applied to both static and dynamic bioaccessibility data.

Automated solid-phase extraction of organic pollutants using melamine–formaldehyde polymer-derived carbon foams

Solid-phase extraction of environmental pollutants is accomplished using carbon foams derived from melamine–formaldehyde polymer foams.