Determination of Arsenic Compounds by High-Performance Liquid Chromatography-Ultrasonic Nebulizer-High Power Nitrogen-Microwave-Induced Plasma Mass Spectrometry:  An Accepted Coupling

Abstract

To establish a sensitive, accurate, and precise determination of arsenic compounds, a high power nitrogen microwave-induced plasma (1.3 kW) mass spectrometer (N2-MIP-MS) has been successfully coupled with an ultrasonic nebulizer (HPLC-USN) that is attached to a high-performance liquid chromatograph. It is examined as an element-specific detector for its applicability to the optimization and determination of seven arsenic compounds [arsenic acid, methylarsonic acid (MA), dimethylarsinic acid (DMA), arsenobetaine (AB), arsenocholine (AC), trimethylarsine oxide (TMAO), and tetramethylarsonium ion (CMI)]. This HPLC-USN-MIP-MS coupling is an encouraging combination as an alternative method for mass spectroscopy for elemental speciation analysis. Interchanging of the MIP-MS fabricated nebulizer (concentric) with an ultrasonic nebulizer, increases 3-6 times the ion signals for the anionic and 6-12 times those for the cationic arsenic compounds as compared to traditional methods. The HPLC-USN-MIP-MS combination used is excellent, amplifying the ion signals about 1.5-2 times for cationic and 1.3-2.8 times for the anionic arsenic compounds as compared to the HPLC-ICPMS coupling. The detection limits for As(V), MA, DMA, AB, TMAO, AC, and TMI (in Milli-Q-water) obtained with the optimized HPLC-USN-N2-MIP-MS system are 0.46, 0.36, 0.73, 0.21, 3.64, 0.39, and 0.32 microg L(-1), respectively, about 13-50 times lower than the HPLC-MIP-MS and about 3-11 times lower than the HPLC-ICPMS. The detection limits of As(V), MA, DMA, AB, TMAO, AC, and TMI, which spike in the urine, are deteriorated by 1.7-4.2 times compared with the detection limits of the seven different As compounds, which are prepared in the Milli-Q-water. The repeatability (RSD for three successive analyses) and reproducibility (RSD for three successive analyses performed on three different days), considering peak area and peak height, achieved for seven different arsenic compounds are 0.5-7 and 0.7-8%, comparable with the HPLC-ICPMS (0.3-8.5%; 4-12%) and HPLC-MIP-MS (0.4-9%; 5-12%) systems. The combined HPLC-USN-N2-MIP-MS has been adequately applied to the determination of AB in NIES Candidate Human Urine CRM. The results agree with the HPLC-ICPMS values. Chloride interference as 40Ar35Cl+ is not found in the urine and with the high chloride matrix (10000 mg L(-1)).

Environmental Contamination of Arsenic and its Toxicological Impact on Humans

“…[55,65,66] Microwave-assisted solvent extraction has also been utilized for the extraction of arsenic species in oyster tissue. [67] Although this extraction procedure apparently yielded higher concentration for the sum of all arsenic species, it did not yield arsenocholine (AsC) but a much higher yield for trimethyl arsine oxide (TMAO) than the traditional solvent-extraction method. The recovery of individual arsenic species depended on the power of the microwave.…”

Application of atmospheric pressure dielectric barrier discharge plasma for the determination of Se, Sb and Sn with atomic absorption spectrometry

“…However, using ICP as an atomization cell for AAS measurement has some limitations [21]. Another plasma for the elements analysis is MIP; low detection limits also can be obtained [22]. However, directly coupling HG with MIP has encountered difficulties because of the intolerance of the MIP to the hydrogen gas and water vapor generated during the hydride formation reaction [23].…”

Plasma-source mass spectrometry for speciation analysis: state-of-the-art

“…Analysis of pesticides by this method is particularly attractive because the microwave plasma is capable of generating simultaneous quantitative information for carbon-, chorine-, sulfur-and phosphorous-containing molecules or can provide molecular ions to help identify the parent pesticide species [139]. In addition, a vast number of studies have focused on speciation of volatile compounds by coupling the microwave plasma with gas chromatography for the determination of arsenic [140], mercury [141][142][143], tin [141,142], and selenium [144], to name a few. A number of reviews have been prepared to cover speciation of a wide range of elements by MIPs and their use in both emission and mass spectrometry [134,145,146].…”

“…The tolerance of the MPT to molecular species permits direct analysis of materials containing high concentrations of organic compounds [151]. Also, coupling an ultrasonic nebulizer (USN) to the microwave plasma can help improve limits of detection and facilitate the analysis of aqueous sample solutions [140,152,153].…”