ARSENIC SPECIATION
Arsenic and its compounds are known to have adverse health effects on humans, including cancers of the skin, bladder, kidney & lung, and diseases of the blood vessels of the legs and feet. The toxicity of arsenic depends very heavily on their physico-chemical form. Inorganic arsenic (arsenite, arsenate) containing ground water has caused tremendous epidemic poisoning across the globe. Methylated forms of arsenic (MMA, DMA) are the most common metabolites of the human body and are found to be much less toxic.
Some other arsenic forms which are very commonly presented and account for the majority of the arsenic abundance in the marine environment (arsenobetaine, arsenocholine, arsenosugars etc), are completely non-toxic. The total concentration of arsenic cannot be used solely to explain the toxicity of arsenic in the environment.
PSA 10.825 ISOCRATIC LC SYSTEM (HPLC HG AFS) USED IN CONJUNCTION WITH THE PSA MILLENNIUM EXCALIBUR FOR THE SPECIATION OF ARSENIC
The
PSA 10.055 Millennium Excalibur can easily be utilised for arsenic
speciation with the addition of a strong anion exchange
or a C18 ion-pairing separation system. A simple isocratic HPLC pump can be used
in conjunction with a strong anion exchange column
(PSA C1 or equivalent) to separate up to four arsenic species; arsenite (AsIII),
dimethylarsinic acid (DMA), monomethylarsonic acid (MMA) and arsenate (AsV). For
the determination of non-reducible arsenic species such as arsenobetaine (AsB),
arsenocholine and Trimethylarsine oxide ((TMAO) and arsenosugars; a PSA 10.570 UV oxidation system can be included.
This approach can be used for arsenic speciation in drinks, urine or any matrix after suitable extraction.
Detection limits in the region of 0.2ng ml-1 are readily achievable. With excellent l.o.ds, reproducibility, and ease-of-use arsenic speciation has never been so easy.
The system consists of a 1200 series Isocratic pump, manual injection valve and solvent cabinet. With the simple addition of the correct column, the analyser and hand held are ready to run.
The 1200 series pump is made of robust materials to withstand the most demanding of applications; stainless steel, titanium, gold, ruby, sapphire, ceramics, PEEK and PTFE. The seal wash option for high salt mobile phases keeps maintenance to a minimum, thereby providing lower operational costs.
The system can be enhanced by the C723I009 ChemStation base software. This software is the industries' most widely sold data system, handling all applications including LC, LC/MS, GC, CE and CE/MS. This base provides the ideal platform for labs that need an easy-to-learn and easy-to-use system, which can be scaled up and extended as the laboratory's needs grow.
Chromatogram of five injections of samples overlapped with a 10 ng ml-1 mixed arsenical standards 
Chromatogram of five Arsenic species obtained using HPLC-UV-HG-AFS
Determination of five arsenic species, arsenobetaine (AsBet), arsenite (AsIII), dimethylarsinic acid (DMA), monomethlyarsonic acid MMA and arsenate (AsV) was achieved by commercially available high performance liquid chromatography coupled to hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS).
Arsenic containing human urine samples was filtered using a 0.2μm syringe filter before it was injected into a C18 column (PSA C2 or equivalent). Five arsenic species can be separated using mobile phase (10 mmol l-1 phosphate buffer, 1 mmol TBAH at 0.9 ml min-1, pH 9.2).
The eluted species were then converted to volatile arsines by the addition of 50% concentrated HCl and 1% m/v NaBH4 solutions at a flow-rate of 0.5 and 1 ml min-1 respectively.
The volatile arsines were separated from the liquid phase using a gas-liquid separator and subsequently swept to the AFS detector via a hygroscopic dryer tube. Excess hydrogen from the reaction of reagents provided the hydrogen diffusion flame which atomised the arsenic species. Arsenic was then detected using atomic fluorescence spectrometry.
The speciation of arsenic species including the non-reducible arsenic species (arsenobetaine and arsenosugars) requires the use of UV oxidation system. This, in conjunction with an oxidising reagent, helps the breakdown of non-reducible arsenic species to a form that will react with NaBH4 so these can be quantified. As a result, a slight modification to the system is necessary.
To discuss particular requirements and for more detailed information on the above products please complete the Information Request Form.
Naturally occuring inorganic and organic As species
Name |
Synonyms (also known as) |
arsenate |
As III |
arsenite |
As V |
methylarsonic acid |
MA monomethylarsonic acid (MMA) |
dimethylarsinic acid |
cacodylic acid DMA |
trimethylarsine oxide |
TMAO |
tetramethylarsonium iodide |
TETRA |
arsenobetaine |
AB AsB |
arsenocholine |
AC AsC |
dimethylarsinoylribosides |
x |
trialkylarsonioribosides |
x |
dimethylarsinoylribitol sulfate |
x |
For information on the speciation of other elements please follow the appropriate link below:
