Quantitative analysis of the elements in powder samples by LA-ICP-MS with PMMA powder as the binder and Cs as the internal standard

Abstract

A fine powder of poly(methyl methacrylate) resin (PMMA) was obtained by freezing pulverization and passing through nylon sieves with a pore-size of 250 μm. The PMMA powder was then mixed with an aqueous solution of CsCl to adsorb Cs, which was used as the internal standard for subsequent analysis by laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). The Cs-adsorbed PMMA powder was used as the binder to make sample disks for analysis by LA-ICP-MS. The sample and the binder were simply mixed in a centrifuge tube and put into a laboratory-made disk presser, which was then put into an oven and heated at 110 °C for 2 h. After optimization of the operating conditions, the linear correlation between each of the signal intensities of 11 elements (Al, P, Ca, Mn, Fe, Ni, Cu, Zn, Rb, Sr, Ba) and the mass fractions of the sample was investigated with a certified reference material (CRM) of tea leaf powder issued by the National Metrology Institute of Japan (NMIJ), i.e. NMIJ CRM 7505-a. The square of the correlation was in the range from 0.78 for Fe to 0.92 for Zn. After the internal standard correction using Cs, the square of each correlation for all of the elements investigated was better than 0.99. The usefulness of the present method was confirmed by the analysis of a tea leaf candidate reference material (RM), a white rice flour CRM, and a seaweed CRM.