Page 7: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Arsenic
The U.S. EPA has approved several analytical methods, based on spectroscopy, for the analysis of total arsenic in drinking water. Table 2 outlines the various EPA-approved analytical methods, their respective detection limits, and their advantages and disadvantages. Total arsenic is defined as the concentration of arsenic present in the dissolved and suspended fractions of a water sample. In these methodologies, the arsenic is oxidized and analysed without regard to its chemical form (inorganic or organic) or oxidation state (i.e., As(III) or As(V)).
Atomic absorption via gaseous hydride formation (GHAA) is considered to be the most common method for the determination of arsenic in water, with a detection limit of about 0.001 mg/L (1 µg/L). Some of the other methods may have limitations and may not be appropriate for routine monitoring. These include graphite furnace atomic absorption spectroscopy (GFAA), stabilized temperature platform graphite furnace atomic absorption (STP-GFAA), inductively coupled plasma mass spectroscopy (ICP-MS), selective ion monitoring with ICP-MS, and inductively coupled plasma atomic emission spectroscopy (ICP-AES). For example, ICP-MS analysis may be subject to chloride interference when samples contain high levels of chloride. This method also requires a high level of skill and operator training, and the high initial cost of instrumentation may prevent smaller laboratories from using this method due to operational and financial considerations.
| Methodology | Reference Method | MDL (µg/L) |
Advantages | Disadvantages |
|---|---|---|---|---|
|
||||
| Inductively coupled plasma mass spectroscopy (ICP-MS) |
200.8 (EPA) | 1.4 | Multi-analyte Low MDL |
High capital cost High level of operator skill required Interferences from argon-chloride in high-chloride samples |
| ICP-MS with selective-ion monitoring | (modification) | 0.1 | Multi-analyte Low MDL Short analysis time |
|
| Stabilized temperature platform graphite furnace atomic absorption (STP-GFAA | 200.9 (EPA) | 0.5 | Widely used Low MDL |
Single analyte |
| Graphite furnace atomic absorption (GFAA) | 3113B (SM) | 1 | Widely used |
Single analyte |
| D-2972-93C (ASTM) | 5 | Low MDL | ||
| Gaseous hydride atomic absorption (GHAA) | 3114B (SM) | 0.5 | Low MDL | Single analyte |
| D-2972-93B (ASTM) | 1 | |||
The practical quantitation limit (PQL) for all EPA-approved methods, based on the capability of laboratories to measure arsenic within reasonable limits of precision and accuracy, is 0.003 mg/L (3 µg/L) (U.S. EPA, 1999).
EPA Method 1632 is a GHAA method that provides for direct analysis of drinking water and for speciation of arsenic. The method detection limit is 0.002 µg/L; however, this method requires a high degree of skill (U.S. EPA, 1999). Common methods used for identifying arsenic species include high-performance liquid chromatography or GHAA followed by detection using atomic absorption, atomic fluorescence spectroscopy, or ICP-MS.
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