Trace Metals Analysis

Inductively Coupled Plasmas (ICP) can be used to create gas temperatures over 5000C. At these temperatures, nearly all metals exists as atomic gases as ions or in highly excited electronic states. Concentrations of the metals can be accurately determined by monitoring the light emission from the metals using optical emission spectroscopy (OES) or by monitoring the ions directly using mass spectrometry. Trace metals analysis can be used to measure metal levels in the parts per trillion (ppt) to parts per million range. These instruments are used for applications ranging from monitoring environmental contaminants, to determining stoichiometry of solids to research involving mechanisms of metal transport across cellular membranes. In the last year, ICP measurements enabled the Kanatzidis group to quantify the removal of Cs, Hg, U and other hazardous materials by layered chalocogenide compounds in the range of the EPA’s acceptable limits [Manos et al., Adv. Funct. Mater. 2009, 19, 1-6].

While the sensitivity of each instrument is dependent on the element of interest, the figure below shows typical detection limits. Each instrument requires approximately 10 ml of sample for analysis. Samples are typically prepared by digesting samples in nitric acid, diluting to 5% nitric acid and then filtering. ORGANIC SOLVENTS WILL POLYMERIZE AND DAMAGE THE INSTRUMENTS AND ARE NOT PERMITTED. Samples with low concentrations can be run after proper sample preparation. Contact a staff member before performing analyses on boilogical samples. The ICP-AES is an open access instrument that is available 24 hrs/day and 7 days/week. Due to the much higher sensitivity and increased complexity of the ICP-MS, super users must be trained for each group for ICP-MS analyses.

ICPLOD

ICP - AES (ICP - OES)

ICP is used for elemental analysis of most metals, sulfur and phosphorous in concentrations down to the ppb level. ICP offers a number of advantages over atomic absorption spectrometry: 1) a greater number of elements can be determined, 2) an array of elements can be analyzed essentially simultaneously, and 3) a wider dynamic range of concentration can be determined for each element. We have a Varian model ICP Spectrometer. It can cover the spectral range from 175-785nm. This means that elements with emission lines in the far UV, such as sulfur, phosphorous, and aluminum can be detected and determined. Samples must be prepared in a particle-free liquid. It is possible to analyze samples in some organic matrices and in aqueous matrices containing corrosive materials, such as hydrofluoric acid. However, the use of these matrices requires special instrument setups and should be approved by the staff. The specifications of the instrument are:

Wavelength range: 175-785 nm

Resolution:

	0.008 nm @ 160-335 nm
	0.015 nm @ 335-670 nm
	0.040 nm @ 670-850 nm

Detection limits: ppb range (by element by weight)

This instrument is controlled through a NEC 30 microcomputer (IBM PS2 clone) capable of storing analysis procedures and data, and capable of transferring them to the built-in spreadsheet on any other PC.

ICP - MS

Contact Saman Shafaie or Andy Ott for more information on the operation of this instrument.