Direct, multielement determinations from cotton swipes via plate express microextraction coupled to an inductively coupled plasma mass spectrometer (μEx-ICP-MS)
Cloth swipes are a fairly common sampling modality, having relevance across a wide variety of applications including environmental analysis, forensics, and bioassays. One of the biggest attractions of swipes (and related paper substrates) is the ease of sample collection and transportation, where just the swipe of a surface is required to collect particulates or solution-phase species, with the substrate then readily transported to laboratory facilities. Additionally, the possibility to sample low-volume analytes, such as blood, gunshot residue, etc., provides additional benefits. The modes for the analytical sampling of the immobilized material vary greatly based on the means of analysis. These vary from direct solid analysis by a variety of optical probing methods, to solvent rinsing/extraction, and complete ashing/digestion of the cloth to liberate adsorbed species. Of the methods applied for elemental (metals) analysis of swipe materials, inductively coupled plasma-mass spectrometry (ICP-MS) is the most versatile in terms of coverage and sensitivity. Recently, a direct microextraction approach has been described for uranium isotope ratio determinations. Here, we describe the initial methodology development towards the use of the Advion plate express microextraction device, coupled to an Advion Solation ICP-MS, for simultaneous, multielement analysis. Practical means of identifying test sites and evaluating elution quality are described. Methods of multielement quantification are identified with preliminary figures of merit presented. Finally, use of the method to quantify metals spiked into a synthetic urine matrix is demonstrated. While areas of improvement are clearly suggested, this rapid (<2 min) method of direct microextraction into the ICP (μEx-ICP-MS) shows great promise for use across diverse applications.