A rapid, reproducible method for coating Rotorod Sampler collector rods with silicone grease

The Rotorod Sampler (Sampling Technologies, St. Louis Park, MN) is a rotating-arm impactor that recovers airborne particles on two rapidly moving plastic collector rods. For decades, the standard method for applying silicone grease to collector rods has been with one's finger. Although this method can yield excellent results when performed by practiced investigators, a relatively high skill level is required, and significant intrapreparer variability has been reported in the medical and technical literature.

The purpose of this investigation was to develop and evaluate a new method for coating Rotorod collector rods with silicone grease.

Collector rods were coated with silicone grease by dipping them into a solution consisting of silicone grease and hexane. Pollen recovery by these dipped collector rods was compared with pollen counts obtained with hand-greased collector rods.

Twenty-three paired samples were obtained during five sampling periods. Pollen recovery by the hand-greased and dipped collector rods was similar (P = 0.410). Dipped collector rods generally offered a lower standard deviation than hand-greased collector rods, however, differences were not statistically significant (F = 1.782, P = 0.087). Dipped collector rods were also superior to hand-greased collector rods in several qualitative categories such as grease uniformity, time required for microscopic analysis, and visual quality.

Dipped collector rods offered a time-efficient means to obtain atmospheric samples with excellent visual quality. The resulting pollen counts were similar to data obtained via the standard, manual method. Allergists are encouraged to consider using this new method in their office practices and for drug studies.