William KouJonathan Mertz

Each sample can cost $200 - $400 for one sample, for one isotope ratio.

Standards are precious and expensive

The data varies from site to site

If comparing two samples, the error associated with each sample must be outside the margin of the error of the second sample.

Another problem with stable isotope analysis is that standardization proves to be difficult

The IAEA standard (International Atomic Energy Agency) is the primary standard which is used to calibrate the instrument in the laboratory, and is very expensive and hard to obtain.

Not many laboratories in the world that can do it. (only 4 in the U.S. as of 2008)

Not as effective for compounds that are water soluble

There are two methods that can easily confound the analysis CSIR data:

1. Heterogeneity in flow paths2. Proximity to other sources of

contamination

As stated in the article, “…has been criticized for being too costly, requiring greater interpretation, and being too variable from site to site.”

Sampling from site to site can be found to be inconsistent.

In the uptake of a groundwater sample, contaminants are easily taken from an undesired area.

Contaminant degradations along flow paths are not always the same.

Sources of new contamination to ground water allow fresh (unfractionated) material to dissolve into water to replace the material that was removed by degradation

This dilutes the fractionated material and reduces the overall value of δ13C.

Isotopic analysis works best for volatile compounds, but is not as reliable for water soluble compounds.

The detection limit for water soluble compounds increases by an order of magnitude or more.

Spectrophotometers are cheap, fast, and extremely easy to use.

They are accurate in quantifying the amount of contaminant within a sample.

Most widely used around the world

Very little training required to operate

Stable Isotopic Analysis is an interesting technique requiring far more refinement. It is a costly and difficult process in which few laboratories in the world are capable of completing. The results also can vary from site to site.

Cheaper and much more common alternatives are available such as Spectrophotometry.