Determination of arsenobetaine, arsenocholine, and tetramethylarsonium cations by liquid chromatography-thermochemical hydride generation-atomic absorption spectrometry

Presence and distribution of arsenical species in beers

The total content of arsenic and of its inorganic (As(III) and As(V)) and organic (monomethylarsonic acid, MMAA, and dimethylarsinic acid, DMAA) species were determined in a set of 21 alcoholic and alcohol-free beer samples using the technique of Hydride Generation Atomic Absorption Spectrometry. For total arsenic analysis, beer samples were dried and then microwave digested with nitric acid in polytetrafluoroethylene containers. For the speciation analysis, beers were previously subjected to ion exchange chromatography to elute the mentioned inorganic and organic arsenical species. Both microwave digestion and chromatographic separation methods were validated from certified reference materials and prepared standard solutions, respectively. The results obtained are presented in terms of the distribution and occurrence of arsenical species in the samples. The As levels of the beer samples were in the range of 1.5-12.4 micrograms/l. The influence of the production process for the alcohol-free beers in the speciation of arsenic is discussed. In alcoholic beers MMAA was the most abundant species, and for non-alcoholic beers inorganic As(III) was similar to the organic species. An estimated intake of total As of 0.47 microgram/person/day and 11.4 micrograms/person/day was obtained for average consumers and for heavy drinkers, respectively.

Short-column liquid chromatography with hydride generation atomic fluorescence detection for the speciation of arsenic

Increasing concerns over human exposure to arsenic and more stringent environmental regulations require rapid determination of trace levels of individual arsenic species, which presents an analytical challenge. We describe a method that is capable of speciating nanogram-per-milliliter levels of arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA) within 3 min. Speciation of two common inorganic species in drinking water, As(III) and As(V), is complete in 1.5 min. The method is based on a combination of fast high-performance liquid chromatography (HPLC) separation of arsenic species on 3-cm HPLC guard columns and the sensitive detection of arsenic hydride by atomic fluorescence spectrometry. Detection limits for the four arsenic species in urine samples are 0.4-0.8 ng/mL. This simple method allows for the direct speciation of arsenic present in natural water samples and in human urine samples from the general population, with no need of any sample pretreatment. Our results from the determination of arsenic species in urine and water standard reference materials are in good agreement with the certified values of total arsenic concentration. The method has been successfully applied to speciation studies of metabolism of arsenosugars following the consumption of arsenosugar-containing mussels by human volunteers. Speciation of arsenic in urine samples collected from four volunteers after the ingestion of musseles reveals significant increases of DMAA concentration, resulting from the metabolism of arsenosugars. These results suggest that the commonly used biomarkers for assessing human exposure to inorganic arsenic, which are based on the determination of urinary arsenite, arsenate, MMAA, and DMAA, are not reliable when arsenosugar-containing seafood is ingested.

Metabolism of arsenic after acute occupational arsine intoxication

Among the elements of toxicological relevance, inorganic arsenic (As) probably exhibits the most complex metabolism, and we deemed it interesting to identify and quantify the different As species excreted after an occupational acute intoxication with arsine. For this purpose total As and five As species were determined using an hybrid analytical method coupling liquid chromatography with inductively coupled plasma mass spectrometry. The highest urinary elimination of total As was observed in the first 5 d after admission. The As species mostly excreted were monomethylarsonate (MMA), dimethylarsinate (DMA), As3+, arsenobetaine (AsB), and to a lesser extent As5+. The amount of AsB excreted in urine by the subject does not appear to be completely justified by AsB intake through food. Arsenic is excreted mainly via the urine with a clearance of 7.8 ml/h/kg and follows a triphasic model with periods of 28 h, 59 h, and 9 d, respectively. The evidence that DMA excretion culminates after a few days, when the excretion of the inorganic form is substantially reduced (while that of MMA is still elevated), seems to confirm the existence of two successive methylating enzyme activities. Furthermore, the elimination rate of As from blood follows a three-phase model and the half-lives of different species vary from about 27 to 86 h with the following gradient As5+ < MMA < As3+ < DMA < AsB.

On-line speciation of arsenical compounds in fish and mussel extracts by HPLC-ICP-MS

The separation and determination of sub-μmol/l levels of six environmentally significant As compounds was accomplished by means of high performance liquid chromatography (HPLC) combined online with inductively coupled plasma mass spectrometry (ICP-MS). The species of interest (arsenite and arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine) were quantified in fish and mussel extracts after separation on a Dionex AS7 column equipped with an on-guard AG7 column using a bicarbonate buffer as the mobile phase in a gradient mode. The species thus eluted were directly forwarded to the ICP-MS detector. The detection power of the overall system allows each As form to be determined at concentrations as low a 0.0013-0.0027 μmol 1(-1).