Speciation of arsenic is crucial for assessing health
implications from arsenic ingestion and for effective removal
of arsenic from water. We report a method for the
speciation of submicrogram per liter levels of arsenic in
water. The method incorporates water sample collection
with on-site arsenic species separation. The method is based
on selective retention of arsenic species on specific solid-phase cartridges followed by selective elution and
hydride generation atomic fluorescence analysis of the
arsenic species. The use of a membrane filter, a resin-based strong cation-exchange cartridge, and a silica-based
strong anion-exchange cartridge allows for the speciation
of particulate arsenic and soluble arsenite, arsenate,
monomethylarsonate, and dimethylarsinate species. Detection
limit is on the order of 0.05 μg/L. The method is suitable
for direct water sample collection and on-site separation of
arsenic species by flowing a measured volume of water
sample through the filter and cartridges connected in serial.
A particular advantage of this approach is to maintain
the integrity of original arsenic species in the sample. It
overcomes the common problem of instability of arsenic
species after water sampling and during sample storage and
handling. Applications of the method are demonstrated
to the speciation of arsenic in well water, raw (untreated)
river water, bottled water, and a standard reference
material (SRM 1643d). Results agree well with the certified
values of the SRM.
Various solid phase extraction (SPE) cartridges were investigated for speciation of arsenite [As(III)], arsenate [As(v)], monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Cartridges containing different types of sorbent materials were tested for arsenic retention and elution characteristics. Alumina cartridges were found to completely retain all the four target arsenic species, and are suitable for removal and preconcentration purposes. For speciation analysis, different arsenic species were separated on the basis of their selective retention on and elution from specific cartridges. DMA was retained on a resin-based strong cation exchange cartridge and eluted with 1.0 M HCl. MMA and As(v) were both retained on a silica-based strong anion exchange cartridge and sequentially eluted with 60 mM acetic acid (for MMA) and 1.0 M HCl [for As(v)]. As(III) was not retained on either cartridge and remained in solution. Arsenic species in solution and those eluted from the cartridges were subsequently quantified by using flow injection with hydride generation atomic fluorescence spectrometry (FI-HGAFS) and hydride generation atomic absorption spectrometry (FI-HGAAS). A detection limit of 0.05 microg L(-1) arsenic in water sample was achieved using HGAFS. An application of the method was demonstrated at a drinking water treatment facility. As(III) and As(v) species were determined in water at various stages of treatment. The method is suitable for routine determination of trace levels of arsenic in drinking water to comply with more stringent environmental regulations.
In this study, material characteristics of historic oil paintings in a 19th century church in Ayvalık/Turkey were investigated to propose the treatments to be used in their conservation and protection. For this purpose, physical, chemical and mineralogical compositions and the microstructure of the paintings were determined by X-ray Diffraction, Scanning Electron Microscope, Thermo Gravimetric Analyzer, Differential Scanning Calorimeter, Infrared Spectroscopy and Laser Induced Breakdown Spectroscopy. Analysis results showed that the paintings were composed of very thin binding and white priming layers on which the pigments were applied. Binding layers were composed of polymerized vegetable oil with Zinc Oxide. Priming layers were composed of anglesite mineral in polymerized vegetable oil.Pigments used in paintings were mainly green earth, red chrome and iron oxide.
In this study, design and optimization studies of a sample introduction system based on ultrasonic nebulization of metal salts in aqueous environment for laser-induced breakdown spectroscopic detection were presented. The system consisted of an ultrasonic nebulizer connected to a tandem heater-condenser-membrane dryer unit that produces sub-micron size aerosols. Results indicate improvements in detection limits for some elements with the use of membrane dryer. Optimization studies were performed by systematical investigation of LIBS emission signal with respect to laser energy, carrier gas flow rate and detector timing parameters. Under optimized conditions, calibration graphs for Na, K, Mg, Ca, Cu, Al, Cr, Cd, Pb and Zn were constructed and detection limits were calculated. The applicability of the ultrasonic nebulization-LIBS system was tested on real water samples. This system establishes LIBS as an effective analytical tool for both qualitative and quantitative determination of metal aerosols in aqueous environments. This technique is sufficiently rapid to provide real-time monitoring of toxic metals.
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