Total and inorganic arsenic in dietary supplements based on herbs, other botanicals and algae—a possible contributor to inorganic arsenic exposure

The content of total and inorganic arsenic was determined in 16 dietary supplements based on herbs, other botanicals and algae purchased on the Danish market. The dietary supplements originated from various regions, including Asia, Europe and USA. The contents of total and inorganic arsenic was determined by inductively coupled plasma mass spectrometry (ICP-MS) and anion exchange HPLC-ICP-MS, respectively, were in the range of 0.58 to 5.0 mgkg^?1 and 0.03 to 3.2 mg?kg^?1, respectively, with a ratio between inorganic arsenic and total arsenic ranging between 5 and 100 %. Consumption of the recommended dose of the individual dietary supplement would lead to an exposure to inorganic arsenic within the range of 0.07 to 13 μg?day^?1. Such exposure from dietary supplements would in worst case constitute 62.4 % of the range of benchmark dose lower confidence limit values (BMDL₀₁ at 0.3 to 8 μg kg bw^?1 kg^?1 day^?1) put down by European Food Safety Authority (EFSA) in 2009, for cancers of the lung, skin and bladder, as well as skin lesions. Hence, the results demonstrate that consumption of certain dietary supplements could contribute significantly to the dietary exposure to inorganic arsenic at levels close to the toxicological limits established by EFSA.     

Electrodeposition and stripping voltammetry of arsenic(III) and arsenic(V) on a carbon black–polyethylene composite electrode in the presence of iron ions

In this work, a new sensor is proposed for the stripping voltammetric determination (anodic stripping voltammetry—ASV) of total arsenic(V) or arsenic(III). The sensor is based on an Fe-modified carbon composite electrode containing 30 % carbon black–high-pressure polyethylene (CB/PE). The modification with iron is achieved by the addition of Fe(III) or Fe(II) ions to the sample solution and co-electrodeposition of iron and arsenic on the CB/PE electrode. In anodic stripping voltammetry, two peaks are observed: an Fe peak at ?0.45 or ?0.29 V and a peak at 0.12?±?0.07 V which depends on the arsenic concentration and corresponds to the As(0) → As(III) oxidation, as is the case with other solid electrodes. The optimum conditions proposed for ASV determination of As(V) and As(III) in solutions in the presence of dissolved oxygen are the following: the background electrolyte is 0.005 M HCl containing 0.5–1 mg/?L Fe(III) for As(V) and containing 1.0–1.5 mg/?L Fe(III) for As(III), respectively; E _dep?=??2.3 V; rest period at ?0.10 V for 3–5 s before the potential sweep from ?0.2 to +0.4 V; scan rate is 120 mV/?s. The detection limit (LOD, t?=?120 s) for As(III) and As(V) is 0.16 and 0.8 μg/?L, respectively. Various hypotheses on the effect of Fe ions and atoms on the electrodeposition and dissolution of arsenic are considered. The new method of determination of As(III) and As(V) differs from known analogues by its simplicity, low cost, and easy accessibility of the electrode material. It allows the voltammetric determination of total arsenic after chemical reduction of all its forms to As(III) or after their oxidation to As(V).     

Simultaneous determination of arsenic(III) and arsenic(V) by flow injection–inductively coupled plasma–atomic emission spectrometry (ICP-AES) with ultrasonic nebulization

A dual-column protocol for the sequential determination of As(III) and As(V) is described using inductively coupled plasma-atomic emission spectrometry (ICP-AES) with ultrasonic nebulization (USN). This procedure employed a 16-way valve containing two different homemade mini columns for selective preconcentration of As(III) and As(V). One column was filled with Muromac A-1, which selectively preconcentrated As(III) at pH 3 after complexation with ammonium pyrrolidine dithiocarbamate (APDC, 0.05%). The effluent of the first column was then passed through the second column, which was filled with an anion-exchange resin to collect As(V). By using 0.6 M sodium hydroxide, both species were eluted sequentially and measured by ICP-AES. Enrichment factors of 136 (17 for micro column x8 for USN) for As(V) and 160 (20 for micro column x8 for USN) for As(III) were achieved with 4 min preconcentration. With the proposed procedure, the detection limits were calculated to be 0.7 micro g L(-1) for As(V) and 0.8 micro g L(-1) for As(III) based on (3 sigma) blank determination ( N=10). The relative standard deviations for 20 micro g L(-1) of As(V) and As(III) were 5.8% and 6.5%, respectively. The recovery for spiked water samples was in the range of 85-112%.     

Could hydrolysis of arsenic substituted DNA be prevented? Protection arises from stacking interactions

Investigation of the hydrolysis of dinucleoside-arsenate-deoxyguanylyl-3',5'-deoxyguanosine (dGAsdG(-)) reveals that base-stacking in DNA increases the resistance of As-DNA towards hydrolysis. Base-stacking raises the activation energy of hydrolysis. Hydrolysis of As-DNA is found to be endothermic. The hydrolysis stability of As-DNA should be higher than that estimated based on arsenate diester models.     

Determination of trace arsenic(V) by catalytic solid substrate-room temperature phosphorescence quenching method

In the H2SO4 medium and in the presence of dodecylbenzene sulfonic acid sodiumsalt (DBS), dimethyl yellow (R) could emit strong and stable solid substrate room temperature phosphorescence (RTP) on filter paper. And NaIO4 could oxidize R to cause the RTP quenching. Arsenic(V) could catalyze the reaction of NaIO4 oxidizing R, which caused the RTP sharply quenching. The reducing value of phosphorescence intensity (△Ip) for the system with DBS is 3.3 times higher than that without DBS. Moreover, the△Ip is proportional to the concentration of As(V). Based on the facts above, a new RTP quenching method for the determination of trace As(V) has been established.     

Determination of arsenic species and arsenosugars in marine samples by HPLC–ICP–MS

Arsenic-speciation analysis in marine samples was performed by high-pressure liquid chromatography (HPLC) with ICP–MS detection. Separation of eight arsenic species—As^III, MMA, DMA, As^V, AB, TMAO, AC and TeMAs⁺—was achieved on a C₁₈ column with isocratic elution (pH 3.0), under which conditions As^III and MMA co-eluted. The entire separation was accomplished in 15 min. The HPLC–ICP–MS detection limits for the eight arsenic species were in the range 0.03–0.23 μg L⁻¹ based on 3σ for the blank response (n=5). The precision was calculated to be 2.4–8.0% (RSD) for the eight species. The method was successfully applied to several marine samples, e.g. oysters, fish, shrimps, and marine algae. Low-power microwave digestion was employed for extraction of arsenic from seafood products; ultrasonic extraction was employed for the extraction of arsenic from seaweeds. Separation of arsenosugars was achieved on an anion-exchange column. Concentrations of arsenosugars 2, 3, and 4 in marine algae were in the range 0.18–9.59 μg g⁻¹. This paper was presented at the European Winter Conference 2005     

Speciation of inorganic and organic arsenic in marine sediments from La Coruña estuary

The speciation of As(III), As(V), MMA and DMA in marine sediments from La Coruña estuary is described. The arsenic species have been separated by ion-exchange chromatography and detected by hydride generation atomic absorption spectrometry (HGAAS). The redox potential has been determined in order to relate the concentration of arsenic species to this parameter.     

Determination of arsenic by inductively coupled plasma mass spectrometry – comparison of sample introduction techniques

A comparison is made of four sample introduction techniques for the determination of As by inductively coupled plasma mass spectrometry. The techniques studied were 1) flow injection with pneumatic nebulization (FIA-PN), 2) direct electrothermal vaporization (ETV), 3) continuous hydride generation (HG) and 4) hydride generation with in situ trapping followed by electrothermal vaporization (HG-ETV). It was found that FIA-PN and ETV gave similar detection limits in concentration units (about 20 pg mL^–1), although ETV had a much lower absolute detection limit (0.2 pg). Sample introduction by hydride generation gave an inferior detection limit (100–200 pg mL^–1), also in combination with in situ trapping and ETV, owing to the blank signal from traces of As in NaBH₄ which is difficult to eliminate. The results indicate that the more elaborate sample introduction techniques based on ETV and HG may not offer significant advantages compared to normal solution nebulization for the determination of As in simple sample matrices such as natural fresh waters, where matrix removal is not required.     

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Analytical and Bioanalytical Chemistry -     

Adsorption of arsenic (V) from a water solution onto a surfactant-modified zeolite

In this study a surfactant-modified zeolite (SMZ) was prepared by adsorbing the cationic surfactant hexadecyltrimethylammonium (HDTMA) bromide on a clinoptilolite. The adsorption of the surfactant modified the surface properties of the clinoptilolite and enhanced the anionic capacity of the SMZ. The adsorption equilibrium data of As(V) from the water solution on the SMZ were obtained in a batch adsorber, and the Langmuir isotherm matched the data reasonably well. The As(V) adsorption capacity of the SMZ was 12.5 times greater than that of the clinoptilolite. The adsorption of As(V) on SMZ was mainly due to the interactions between the anionic sites of the SMZ and the As(V) anions in water solution. The adsorption capacity of the SMZ was dependent on the solution pH. The adsorption capacity was increased and decreased by augmenting the pH from 5 to 7 and from 7 to 12, respectively. This unusual behavior was due to the fact that the affinity of the As(V) for the SMZ was dependent on the As(V) species that were present in solution. The adsorption capacity of the SMZ was slightly favored by decreasing the temperature from 25 to 15 °C. The heat of adsorption was estimated to be ΔH _ads=−46.82 KJ/mol, indicating that the adsorption was exothermic and the As(V) was chemisorbed on the SMZ.     

Detection of arsenic and lead in chromite by alkali fusion-acid dissolvingatomic fluorescence spectrometryEI北大核心CSCD

A hydride generation-atomic fluorescence spectrometry （AFS） method was developed for the detection of arsenic （As） and lead （Pb） in chromite by alkali fusing and acid dissolving. The sample was fused by Na2O2 and acidification dissolved by HCl. As was quantified by AFS with 10% （V/V） HCl as the carrier flow agent, and KBH4（15 g/L） as reducing agent. Pb was quantified by AFS with 1% （V/V） HCl as the carrier flow agent, and KBH4（20 g/L）-KOH（10 g/L）-K3［Fe（CN）6］ （15 g/L） as reducing agent. Under the optimum conditions, the correlation coefficient （R2） was 1.0000 in the range of 0.5-10 μg/L, the limit of detection （LOD） was 0.05 μg/g with the relative standard deviations （RSDs） of 1.4%-6.0% and the recoveries of 96.2%-116.7% for As. And the R2 was 0.9998 in the range of 1.25-25 μg/L, the LOD was 0.2 μg/g with the RSDs of 1.5%-3.7% and the recoveries of 95.9%-112.2% for Pb. In addition, the method was validated by certified reference sample analysis and multi-laboratory test, which meets the requirements for the standardized quantitative analysis of trace As and Pb in chromite. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Automated system for on-line determination of dimethylarsinic and inorganic arsenic by hydride generation–atomic fluorescence spectrometry

A multisyringe flow-injection approach has been coupled to hydride generation-atomic fluorescence spectrometry (HG-AFS) with UV photo-oxidation for dimethylarsinic (DMA), inorganic As and total As determination, depending on the pre-treatment given to the sample (extraction or digestion). The implementation of a UV lamp allows on-line photo-oxidation of DMA and the following arsenic detection, whereas a bypass leads the flow directly to the HG-AFS system, performing inorganic arsenic determination. DMA concentration is calculated by the difference of total inorganic arsenic and measurement of the photo-oxidation step. The detection limits for DMA and inorganic arsenic were 0.09 and 0.47 μg L(-1), respectively. The repeatability values accomplished were of 2.4 and 1.8%, whereas the injection frequencies were 24 and 28 injections per hour for DMA and inorganic arsenic, respectively. This method was validated by means of a solid reference material BCR-627 (muscle of tuna) with good agreement with the certified values. Satisfactory results for DMA and inorganic arsenic determination were obtained in several water matrices. The proposed method offers several advantages, such as increasing the sampling frequency, low detection limits and decreasing reagents and sample consumption, which leads to lower waste generation.     

Preparation of new base-aluminum-chloride-loaded fiber as adsorbent for fast removal of arsenic(Ⅴ) from water

A new base-aluminum-chloride-loaded fiber[PET-AA-NN-Al₂（OH）_nCl_6-n]was prepared with polyethylene glycol terephthalate （PET） as adsorbent for fast removal of arsenic（Ⅴ） from water.This new fibrous adsorbent was characterized by using SEM and C NMR spectroscopy.Adsorption kinetic curve indicated that this new fibrous adsorbent could fast remove arsenic（Ⅴ） from water, and adsorption isotherm also indicated that PET-AA-NN-A1₂（OH）_nC1_6-n had high equilibrium adsorption capacity for arsenic（Ⅴ）.     

A comparison of different types of gold–carbon composite electrode for detection of arsenic(III)

A study has been conducted using abrasively modified basal and edge-plane graphite, carbon-paste, and carbon–epoxy electrodes to create gold–carbon composite electrodes. Using either nano or micro-sized gold particles their suitability for use in detecting arsenic(III) is assessed. It was found that gold arrays prepared from micron-sized particles gave the best performance for arsenic detection. In particular micron arrays produced in carbon-paste electrodes with an easily renewable surface work well for detection of arsenic, producing a detection limit of 5(±2)×10^–9 mol L^–1, with a high sensitivity of 10(±0.1) A mol^–1 L.     

Colorimetric and fluorescence dual-mode detection of arsenic（v） based on cobalt oxyhydroxide nanoplatesEI北大核心CSCD

The oxidase-like activity of cobalt oxyhydroxide （CoOOH） nanosheets is inhibited by arsenic （V） in the system, thereby attenuating the oxidation of p-phenylenediamine （PPD） by CoOOH nanosheets, and changing the absorbance of the solution. Based on this principle, and the fluorescence inner filter effect （IFE） of p-phenylenediamine oxide （oxPPD） on the dye acridine orange （AO）, a colorimetric and fluorescence dualmode method for the quantitative detection of As（V） was established. The variation of absorbance and fluorescence intensity of As（V） with different concentrations was investigated, and the effects of the concentrations of CoOOH nanosheet and PPD, pH of buffer solution, and temperature of reaction were optimized. The results showed that under the optimized conditions, the concentration of As（Ⅴ） had a good linear relationship with the corresponding signal intensity, and the detection limits of colorimetric and fluorescence method were 5 and 10 nmol/L, respectively. The method has been used for the determination of arsenic（V） in lake water located the city center. © 2023, Youke Publishing Co.,Ltd. All rights reserved.