An Inexpensive Autosampler to Maximize Throughput for an Ion Source that Samples Surfaces in Open Air

Rapid analysis of hundreds of wipe samples after a chemical dispersion event is essential for quickly characterizing the hazard posed to the public. An autosampler was built to pull 76 cotton swabs mounted along a 91-cm (3-foot) long, square aluminum rod in open air, through the ionizing beam of a direct analysis in real time (DART 1 1DART is a registered trademark of JEOL USA, Inc, Peabody, MA. ) ion source interfaced to a time-of-flight mass spectrometer. The rod and swabs mounted on N-scale model railroad flat cars were pulled through the ion source in 7.5 min by a 7-rpm motor. Percent relative standard deviations (%RSDs) of 18.5% to 21.3% were obtained for the chromatographic peak areas of the protonated molecule. Maximum-to-minimum ratios of the areas were between 2.22 and 2.71. Measured exact masses of analyte ions were always accurate to within 1 mDa.