Approaches for the unambiguous identification of lipophilic arsenic species in Saccharina latissima (sugar kelp) have been studied. Parallel use of high resolution ICPMS and electrospray ionization ...(ESI)-MS after separation revealed that Saccharina latissima contained three distinct classes of lipophilic As-species, a family of arsenic containing phospholipids (AsPL), all including As in the form of As–sugar–PO4, As-containing hydrocarbons (AsHC), and As-containing polyunsaturated fatty acids (AsFA). For detailed identification, the use of phospholipases, in particular phospholipase A2, was essential to define the fatty acid composition (determination of regioisomers) of the lipids without purification of the sample, while fragmentation of the molecules by MS2 measurements alone did not supply this information. Some of the identified AsPL contained unsaturated fatty acids (C16:1, C18:1 to C18:3), but saturated fatty acids dominated the AsPL. The fatty acid bound to the position 2″ was predominantly C16:0. Complete lipid hydrolysis showed that this alga did not contain arsenic containing fatty acids (AsFA) bound to complex lipids. Our investigations indicate that in addition to RP-HPLC-ICPMS/ESI-MS a range of different derivatization methods should be used for the comprehensive identification of unknown lipid-soluble arsenic compounds.
Nanoscale secondary ion mass spectrometry (NanoSIMS) is a dynamic SIMS technique, which offers high spatial resolution allowing the mapping of chemical elements at the nanometer scale combined with ...high sensitivity. However, SIMS for mercury analysis is a challenging issue due to the low secondary ion yield and has never been done on NanoSIMS. The introduction of an rf plasma oxygen primary ion source on NanoSIMS enabled higher lateral resolution and higher sensitivity for electropositive elements such as most metals. In this paper, for the first time, mercury analysis by NanoSIMS was developed applying the new rf plasma O– ion source. All mercury isotopes could be detected as Hg+ secondary ions and the isotopic pattern corresponded to their natural isotopic abundances. Furthermore, Hg+ detection in HgSe nanocrystals has been investigated where polyatomic interferences from selenium clusters were identified and separated by high mass resolution (ΔM/M ≥ 3200). However, in the presence of selenium a strong matrix effect was observed, decreasing the Hg+ secondary ion yield. In addition, a detection of Se+ ions was possible, too. The newly developed method was successfully applied to nanoscale localization by chemical imaging of HgSe particles accumulated in the liver tissue of sperm whale (Physeter macrocephalus). This demonstrated the applicability of NanoSIMS not only for mercury detection in surface analysis but also for mercury mapping in biological samples.
Arsenic (As) finds its way into soils used for rice (Oryza sativa) cultivation through polluted irrigation water, and through historic contamination with As-based pesticides. As is known to be ...present as a number of chemical species in such soils, so we wished to investigate how these species were accumulated by rice. As species found in soil solution from a greenhouse experiment where rice was irrigated with arsenate contaminated water were arsenite, arsenate, dimethylarsinic acid, and monomethylarsonic acid. The short-term uptake kinetics for these four As species were determined in 7-d-old excised rice roots. High-affinity uptake (0-0.0532 mM) for arsenite and arsenate with eight rice varieties, covering two growing seasons, rice var. Boro (dry season) and rice var. Aman (wet season), showed that uptake of both arsenite and arsenate by Boro varieties was less than that of Aman varieties. Arsenite uptake was active, and was taken up at approximately the same rate as arsenate. Greater uptake of arsenite, compared with arsenate, was found at higher substrate concentration (low-affinity uptake system). Competitive inhibition of uptake with phosphate showed that arsenite and arsenate were taken up by different uptake systems because arsenate uptake was strongly suppressed in the presence of phosphate, whereas arsenite transport was not affected by phosphate. At a slow rate, there was a hyperbolic uptake of monomethylarsonic acid, and limited uptake of dimethylarsinic acid.
Due to the increasing number of chemicals released into the environment, nontarget screening (NTS) analysis is a necessary tool for providing comprehensive chemical analysis of environmental ...pollutants. However, NTS workflows encounter challenges in detecting both known and unknown pollutants with common chromatography high-resolution mass spectrometry (HRMS) methods. Identification of unknowns is hindered by limited elemental composition information, and quantification without identical reference standards is prone to errors. To address these issues, we propose the use of inductively coupled plasma mass spectrometry (ICP-MS) as an element-specific detector. ICP-MS can enhance the confidence of compound identification and improve quantification in NTS due to its element-specific response and unambiguous chemical composition information. Additionally, mass balance calculations for individual elements (F, Br, Cl, etc.) enable assessment of total recovery of those elements and evaluation of NTS workflows. Despite its benefits, implementing ICP-MS in NTS analysis and environmental regulation requires overcoming certain shortcomings and challenges, which are discussed herein.
Six varieties of rice were exposed to low and high levels of arsenic in the same soil. Their individual responses of expressing phytochelatins have been correlated to inorganic arsenic uptake, ...transport, and accumulation in the rice grain.
We have developed a method to extract and separate phytochelatins (PCs)-metal(loid) complexes using parallel metal(loid)-specific (inductively coupled plasma-mass spectrometry) and organic-specific ...(electrospray ionization-mass spectrometry) detection systems-and use it here to ascertain the nature of arsenic (As)-PC complexes in plant extracts. This study is the first unequivocal report, to our knowledge, of PC complex coordination chemistry in plant extracts for any metal or metalloid ion. The As-tolerant grass Holcus lanatus and the As hyperaccumulator Pteris cretica were used as model plants. In an in vitro experiment using a mixture of reduced glutathione (GS), PC2, and PC3, As preferred the formation of the arsenite $\text{As}^{(\text{III})}-\text{PC}_{3}$ complex over GS-$\text{As}^{(\text{III})}-\text{PC}_{2}$, $\text{As}^{(\text{III})}-(\text{GS})_{3}$, $\text{As}^{(\text{III})}-\text{PC}_{2}$, or $\text{As}^{(\text{III})}-(\text{PC}_{2})_{2}$ (GS: glutathione bound to arsenic via sulphur of cysteine). In H. lanatus, the $\text{As}^{(\text{III})}-\text{PC}_{3}$ complex was the dominant complex, although reduced glutathione, PC2, and PC3 were found in the extract. P. cretica only synthesizes PC2 and forms dominantly the GS-$\text{As}^{(\text{III})}-\text{PC}_{2}$ complex. This is the first evidence, to our knowledge, for the existence of mixed glutathione-PC-metal(loid) complexes in plant tissues or in vitro. In both plant species, As is dominantly in non-bound inorganic forms, with 13% being present in PC complexes for H. lanatus and 1% in P. cretica.
Although it has been known for decades that arsenic forms fat-soluble arsenic compounds, only recent attempts to identify the compounds have been successful by using a combination of fractionation ...and elemental and molecular mass spectrometry. Here we show that arsenolipids can directly be identified and quantified in biological extracts using reversed-phase high-performance liquid chromatography (RP-HPLC) simultaneously online-coupled to high-resolution inductively coupled plasma mass spectrometry (ICPMS) and high-resolution electrospray mass spectrometry (ES-MS) without having a lipophilic arsenic standard available. Using a methanol gradient for the separation made it necessary to use a gradient-dependent arsenic response factor for the quantification of the fat-soluble arsenic species in the extract. The response factor was obtained by using the ICPMS signal of known concentration of arsenic. The arsenic response was used to determine species-specific response factors for the different arsenic species. The retention time for the arsenic species was utilized to mine the ES-MS data for accurate mass and their tandem mass spectrometry (MS/MS) fragmentation pattern to give information of molecular formula and structure information. The majority of arsenolipids, found in the hexane phase of fish meal from capelin (Mallotus villosus) was in the form of three dimethylarsinoyl hydrocarbons (C23H38AsO, C17H38AsO, C19H42AsO) with minor amounts of dimethylarsinoyl fatty acids (C17H36AsO3, C23H38AsO3, C24H38AsO3). One of the dimethylarsinoyl fatty acids (C24H38AsO3), with an even number of carbon in the fatty acid chain, was identified for the first time in this work. This molecular formula is unusual and in contrast to all previously identified arsenic-containing fatty acids with odd numbers of carbon.
Paired grain, shoot, and soil of 173 individual sample sets of commercially farmed temperate rice, wheat, and barley were surveyed to investigate variation in the assimilation and translocation of ...arsenic (As). Rice samples were obtained from the Carmargue (France), Doñana (Spain), Cadiz (Spain), California, and Arkansas. Wheat and barley were collected from Cornwall and Devon (England) and the east coast of Scotland. Transfer of As from soil to grain was an order of magnitude greater in rice than for wheat and barley, despite lower rates of shoot-to-grain transfer. Rice grain As levels over 0.60 μg g-1 d. wt were found in rice grown in paddy soil of around only 10 μg g-1 As, showing that As in paddy soils is problematic with respect to grain As levels. This is due to the high shoot/soil ratio of ∼0.8 for rice compared to 0.2 and 0.1 for barley and wheat, respectively. The differences in these transfer ratios are probably due to differences in As speciation and dynamics in anaerobic rice soils compared to aerobic soils for barley and wheat. In rice, the export of As from the shoot to the grain appears to be under tight physiological control as the grain/shoot ratio decreases by more than an order of magnitude (from ∼0.3 to 0.003 mg/kg) and as As levels in the shoots increase from 1 to 20 mg/kg. A down regulation of shoot-to-grain export may occur in wheat and barley, but it was not detected at the shoot As levels found in this survey. Some agricultural soils in southwestern England had levels in excess of 200 μg g-1 d. wt, although the grain levels for wheat and barley never breached 0.55 μg g-1 d. wt. These grain levels were achieved in rice in soils with an order of magnitude lower As. Thus the risk posed by As in the human food-chain needs to be considered in the context of anaerobic verses aerobic ecosystems.
The most common routes of arsenic exposure are ingestion and inhalation, whereas dermal uptake has been considered as a minor uptake route based on uptake experiments with arsenate. Here the kinetics ...of arsenite, dimethylarsinic acid (DMA(V)) and arsenosugar penetration through full thick human skin (from one volunteer) was determined using a Franz Cell design and compared to that of arsenate. The accumulation in the epidermis and dermis was performed by using laser ablation ICP-MS as a bioimaging method, and the biotransformation reactions through the uptake experiment were monitored by hyphenated elemental mass spectrometry. The penetration and accumulation of arsenic is strongly dependent on its speciation. While arsenosugars penetrated through the unbroken skin at a similar rate as arsenate, arsenite and DMA(V) were taken up percutaneously at a rate which was more than a factor of 29 and 59 higher than that of arsenate. The dermal uptake route of arsenic has been underestimated in risk assessments where exposure to arsenite or DMA(V) would occur. The accumulation potential of arsenosugars and DMA(V) was however minimal, whereas arsenate and arsenite accumulated in the epidermis and in the dermis. No significant species transformations were observed.
Anthropogenic emissions of mercury to the environment are of great concern due to its toxicity. The burning of coal contributes highly to Hg emissions and, as such, much lower effluent discharge ...limits for Hg in flue gas desulphurisation (FGD) wastewater have recently been proposed in the USA. Lower detection limits are required to meet the most demanding discharge limit of 10 ng L−1. Therefore, in this work, a new analyser for online monitoring of Hg in FGD wastewater based on syringe injections of chemicals combined with gold amalgamation – atomic fluorescence spectrometry has been developed. The instrument has been validated against international standard method ISO 17852, as well as an interference study with extreme levels of salts majorly present in FGD water. Detection limits of 1.8 ng L−1 as well as accurate performance in an on-site field trial indicate that the methodology is fit to meet the new legislation. HIGHLIGHTS LOD of 1.8 ng L−1 and LOQ of 3.7 ng L−1, with possibilities to further reduction by varying sample intake.; Successful analysis carried out on-site with a constantly changing effluent Hg concentration.; Interference study indicates the instrument is robust in high levels of extreme levels of salts present in FGD wastewater.;
PDF
