Speciation of gold nanoparticles and total gold in natural waters: A novel approach based on naked magnetite nanoparticles in combination with ascorbic acid

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.

Analytical Performance and Validation of a Reliable Method Based on Graphite Furnace Atomic Absorption Spectrometry for the Determination of Gold Nanoparticles in Biological Tissues

Gold nanoparticles (AuNPs) have a wide-ranging application and are widespread in samples with complex matrices; thus, efficient analytical procedures are necessary to identify and characterize this analyte. A sensitive analytical method for determination of AuNPs content in biological tissues, based on microwave-assisted acid wet digestion and graphite furnace atomic absorption spectrometry (GFAAS) validated in accordance with the requirements of Eurachem guideline and ISO 17025 standard, is presented in this study. The digestion procedure was optimized, and the figures of merit such as selectivity, limit of detection (0.43 µg L-1), limit of quantification (1.29 µg L-1, corresponding to 12.9 µg kg-1 in tissue sample, considering the digestion), working range, linearity, repeatability ((RSDr 4.15%), intermediate precision (RSDR 8.07%), recovery in accuracy study (97%), were methodically evaluated. The measurement uncertainty was assessed considering the main sources of uncertainties and the calculated relative expanded uncertainty (k = 2) was 12.5%. The method was applied for the determination of AuNPs in six biological tissues (liver, small intestine, heart, lungs, brain and kidneys) and the found concentrations were generally at low levels, close or lower than LOQ.

Magnetic Solid Phase Extraction as a Promising Technique for Fast Separation of Metallic Nanoparticles and Their Ionic Species: A Review of Recent Advances

The widespread use of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) in a wide variety of industrial as well as medical sectors is indisputable. This leads to a new concern about their presence in various environmental compartments. Since their negative effect and potential toxicity impact have been confirmed, analytical chemists focus on the development of different procedures for their reliable detection, identification, characterization, and quantification, not only in homogenous and simple matrices but also in complex environmental matrices. However, nanoparticles and their ionic species can coexist and their toxicity may differ; therefore, novel analytical approaches are necessary to monitor not only the nanoparticles but also their ionic species. The aim of this article is to bring a review of recent works where magnetic solid-phase extraction (MSPE) procedures in connection with spectrometric methods were used for separation/preconcentration and quantification of (1) silver and gold ions in various environmental samples, (2) AgNPs and AuNPs in real water samples in the presence of various coexisting ions, and (3) both species (it means Ag ions and AgNPs; Au ions and AuNPs) in real water samples. The results presented herein show the great analytical potential of MSPE procedures in connection with spectrometric methods used in these fields and can be helpful in guiding analytical chemists who aim to work on this subject.

Phosphoric acid functionalized magnetic sorbents for selective enrichment of TiO2 nanoparticles in surface water followed by inductively coupled plasma mass spectrometry detection

Phosphoric acid functionalized superparamagnetic iron oxide was synthesized, and different adsorption behavior of TiO₂ NPs and titanium ions on it was found. By means of dispersion-corrected density functional theory (DFT-D), the adsorption mechanism of TiO₂ NPs and titanium ions on the functionalized sorbents was explored, and the difference in the adsorption behavior was attributed to the different deprotonated forms of phosphates and the competitive adsorption of OH^- anion with respect to either TiO₂ NPs or aqueous titanium ions. Based on the different adsorption performance of phosphoric acid functionalized sorbents for TiO₂ NPs and titanium ions under pH 3, a method by combining magnetic solid phase extraction (MSPE) with inductively coupled plasma mass spectrometry (ICP-MS) was established for the selective quantification of trace TiO₂ NPs in environmental water. Under the optimal experimental conditions, the detection limit of TiO₂ NPs was 17 ng/L with an enrichment factor of 400. The developed MSPE-ICPMS method was applied to the detection of trace TiO₂ NPs in the Yangtze River and the East Lake water. Sub μg/L level of TiO₂ NPs was found in the tested water samples, and recoveries of 91-110% and 90-110% were obtained for TiO₂ NPs at three concentration levels in spiked water samples, respectively. The developed method exhibited high adsorption capacity and low detection limit for target TiO₂ NPs, and was demonstrated with great potential for monitoring TiO₂ NPs in the environment.