Nondestructive sampling methods, such as removal of feathers or hair for contaminant analysis, are desirable in ecological monitoring programs that seek to minimize impacts from harvesting organisms. Such techniques allow investigators to obtain larger ecologically sustainable sample sizes and repeatedly sample individuals over time with limited interference to the organism. Unfortunately, nondestructive sampling techniques have seldom been used for assessing contaminant exposure in reptiles, despite the fact that many reptiles are declining worldwide.

We have recently investigated several methods of nondestructively sampling tissues from snakes in an effort to detect contaminant exposure. The most innovative of our studies used laser ablation ICP-MS (LA-ICP-MS) to quantify As, Se, and Sr concentration in extremely small tail clip samples (~1-2 mg, 2-3 mm) from the banded water snake, Nerodia fasciata fasciata. LA-ICP-MS is a micro-sampling technique with laser spot sizes as small as 5 µm and is applicable to spatial analysis within a sample. Most previous biological applications of LA-ICP-MS have focused on spatial analysis of incremental or annular growth structures such as tree rings, mollusk shells, and fish otoliths. In fact, one of the only other reports of biological applications of LA-ICP-MS on non-mineralized tissue was the analysis of individual gut sacs of brine shrimp.

We used a frequency quintupled NdYAG laser (213 nm) for direct solid sampling of tail clips. The laser created a particulate aerosol that was swept into the ICP-MS for elemental analysis, obviating the need for the more traditional approach of acid digestion, which requires much larger (~100 mg) amounts of tissue. We then compared concentrations obtained by laser ablation to the more traditional approach of acid digestion and found that use of the laser provided an accurate measure of Se concentration in tissue (and, to a lesser extent As). Strontium was underestimated by laser ablation, presumably because Sr was heterogeneously distributed within multiple components of the tail (e.g., skin and bones) and the laser ablation is primarily a surface analysis technique.