Analytical Application of Layered Double Hydroxides as High-Capacity Sorbents in Dispersive Solid Phase Extraction for the Separation and Preconcentration of (Ultra)Trace Heavy Metals.

Separation/preconcentration procedures are of great importance in the elemental analysis. In this context, layered double hydroxides (LDH) have emerged as promising sorbents in dispersive solid phase extraction (DSPE) procedures. By optimizing the DSPE procedure, lower limits of detection (LOD) can be achieved, making less sensitive detection methods viable for accurate quantification of the (ultra)trace analytes. This is of significant importance from a financial standpoint, as it enables the utilization of cost-effective and readily available detection methods. The extraction procedures using LDH typically require only a few minutes to complete, with some procedures taking as little as 1.5 min. Many studies have reported techniques that eliminate the need for centrifugation, which results in time savings and reduced sample handling. This is particularly important for ultratrace analysis. However, it has been observed that the use of certified reference materials (CRM) to validate the reliability of the developed extraction procedures is often overlooked. The literature also demonstrates inconsistencies in the terminology and abbreviations employed for extraction procedures, which may cause confusion. LDH, extensively studied for various purposes, offer a wide range of modifications and can form composites with other materials, enhancing their surface characteristics and adsorption performance. The development of novel and effective nanocomposites will undoubtedly be a research objective in this field of analytical chemistry, aiming to advance the reliability of extraction procedures. Moreover, integrating of LDH-based DSPE procedures with appropriate detection methods can enable potential automation and pave the way for online applications.

Preconcentration and Separation of Gold Nanoparticles from Environmental Waters Using Extraction Techniques Followed by Spectrometric Quantification.

The quantification of gold nanoparticles (AuNP) in environmental samples at ultratrace concentrations can be accurately performed by sophisticated and pricey analytical methods. This paper aims to challenge the analytical potential and advantages of cheaper and equally reliable alternatives that couple the well-established extraction procedures with common spectrometric methods. We discuss several combinations of techniques that are suitable for separation/preconcentration and quantification of AuNP in complex and challenging aqueous matrices, such as tap, river, lake, brook, mineral, and sea waters, as well as wastewaters. Cloud point extraction (CPE) has been successfully combined with electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma mass spectrometry (ICP-MS), chemiluminescence (CL), and total reflection X-ray fluorescence spectrometry (TXRF). The major advantage of this approach is the ability to quantify AuNP of different sizes and coatings in a sample with a volume in the order of milliliters. Small volumes of sample (5 mL), dispersive solvent (50 µL), and extraction agent (70 µL) were reported also for surfactant-assisted dispersive liquid-liquid microextraction (SA-DLLME) coupled with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). The limits of detection (LOD) achieved using different combinations of methods as well as enrichment factors (EF) varied greatly, being 0.004-200 ng L-1 and 8-250, respectively.

Reliable Quantification of Ultratrace Selenium in Food, Beverages, and Water Samples by Cloud Point Extraction and Spectrometric Analysis.

Selenium is a trace element essential for the proper functioning of human body. Since it can only be obtained through our diet, knowing its concentrations in different food products is of particular importance. The measurement of selenium content in complex food matrices has traditionally been a challenge due to the very low concentrations involved. Some of the difficulties may arise from the abundance of various compounds, which are additionally present in examined material at different concentration levels. The solution to this problem is the efficient separation/preconcentration of selenium from the analyzed matrix, followed by its reliable quantification. This review offers an insight into cloud point extraction, a separation technique that is often used in conjunction with spectrometric analysis. The method allows for collecting information on selenium levels in waters of different complexity (drinking water, river and lake waters), beverages (wine, juices), and a broad range of food (cereals, legumes, fresh fruits and vegetables, tea, mushrooms, nuts, etc.).

Application of Metallic Nanoparticles and Their Hybrids as Innovative Sorbents for Separation and Pre-concentration of Trace Elements by Dispersive Micro-Solid Phase Extraction: A Minireview.

It is indisputable that separation techniques have found their rightful place in current analytical chemistry, considering the growing complexity of analyzed samples and (ultra)trace concentration levels of many studied analytes. Among separation techniques, extraction is one of the most popular ones due to its efficiency, simplicity, low cost and short processing times. Nonetheless, research interests are directed toward the enhancement of performance of these procedures in terms of selectivity. Dispersive solid phase extraction (DSPE) represents a novel alternative to conventional solid phase extraction (SPE) which not only delivers environment-friendly extraction with less solvent consumption, but also significantly improves analytical figures of merit. A miniaturized modification of DSPE, known as dispersive micro-solid phase extraction (DMSPE), is one of the most recent trends and can be applied for the extraction of wide variety of analytes from various liquid matrices. While DSPE procedures generally use sorbents of different origin and sizes, in DMSPE predominantly nanostructured materials are required. The aim of this paper is to provide an overview of recently published original papers on DMSPE procedures in which metallic nanoparticles and hybrid materials containing metallic particles along with other (often carbon-based) constituent(s) at the nanometer level have been utilized for separation and pre-concentration of (ultra)trace elements in liquid samples. The studies included in this review emphasize the great analytical potential of procedures producing reliable results in the analysis of complex liquid matrices, where the detection of target analyte is often complicated by the presence of interfering substances.

Impact of Bulk ZnO, ZnO Nanoparticles and Dissolved Zn on Early Growth Stages of Barley-A Pot Experiment.

Zinc is among the most in-demand metals in the world which also means that a considerable amount of this element is released to the environment each year as a result of human activities. A pot experiment was conducted to study the impact of low- and high-dose zinc amendments on plant growth and biomass yield, with Calcic Chernozem as a growing medium and barley (Hordeum vulgare L.) as a model plant. The distribution of zinc in various plant parts was also investigated. Zn (II) was added in powder as bulk ZnO and in solution as ZnO nanoparticles and ZnSO4 in two dosages (3 and 30 mmol kg-1 soil) prior to planting. The plants were harvested after 10 days of growth. The three sets of data were taken under identical experimental conditions. The application of zinc in aqueous solution and in particulate form (having particle sizes in the range of <100 nm to >500 nm) at concentration of 3 and 30 mmol Zn kg-1 to the soil resulted in decreased growth (root length, shoot length) and biomass yield; the only exception was the addition of 30 mmol Zn kg-1 in the form of bulk ZnO, which had a positive effect on the root growth. The dry weight reduction (sprout biomass) was lowest in plants grown in soil treated with dissolved zinc. There were no statistically significant changes in the content of chlorophyll a, chlorophyll b, and total chlorophyll, although flame atomic absorption spectrometry (FAAS) analysis indicated that plants bioaccumulated the zinc applied. This implies that the transport of zinc into the above-ground plant parts is controlled by the presence of effective mechanical and physiological barriers in roots. Crop performance under zinc stress in relation to biomass production and the growth of roots and shoots is also partly a reflection of the effects of soil properties. Our findings emphasize the importance of considering plant-soil interactions in research of potential toxicity and bioavailability of zinc in the environment.

Partitioning and stability of ionic, nano- and microsized zinc in natural soil suspensions.

Batch experiments aimed at solid-liquid distribution of 40 nm engineered zinc oxide nanoparticles (ZnO-NP), microparticles (bulk ZnO), and ionic Zn in ZnSO4 solution were conducted on eight field soil samples of different characteristics to identify how the form of Zn affects its distribution in soil. The concentration of Zn in different size fractions present in supernatant solutions obtained from centrifuged soil suspensions was also measured. The distribution between a liquid and a solid was different for the ionic Zn (ZnSO4) and particulate Zn (ZnO-NP and bulk ZnO). In acidic soil solutions, the partitioning coefficient (KdA) of the ionic Zn was in range of 14.7-15.9 compared to 133.4-194.1 for ZnO-NP and bulk ZnO. The situation was reversed under alkaline conditions resulting in a decreased retention of particulate forms of Zn by the solids, with ZnO-NP showing KdA of 8.5-23.4 compared to 160.0-760.1 of ionic Zn. Soil pH thus appears to be the predominant factor influencing the solid-liquid distribution of Zn in different forms. Even the distribution of Zn in different size fractions is heavily affected by the soil pH, causing dissolution of ZnO-NP and bulk ZnO in acidic soils. In alkaline soils, applied ionic Zn (ZnSO4) remained dissolved. This study shows that ZnO-NP are the most mobile of the three tested forms of Zn in alkaline soils. This may affect the spatial distribution of Zn in soil and potentially increase the effectivity of the application of Zn fertilizer when in nanoparticle form.