Introducing a new era in ICP MS spectrometry – the SPECTRO MS

Scientific evidence plays a vital role in today’s justice system: many high profile criminal investigations reach their conclusions almost entirely on this evidence. Many branches of science are employed in accumulating forensic evidence, from highly publicized techniques like DNA profiling to pathology, botany and of course chemical analysis. Elemental analysis of an object found in the course of an investigation can yield valuable clues to its origin and history. The object itself may, however, need to be presented as evidence, so any technique used for this analysis should ideally be non-destructive. Variation in sample type and size may be almost infinite: from a soil sample to a bullet to a microscopic speck of gunshot residue or fragment of glass. Archaeometry, the application of scientific methods to archaeology, has very similar requirements. Energy Dispersive X-ray Fluorescence (EDXRF) spectrometry is a versatile analytical technique that can satisfy both of these needs: it is non-destructive, requires very little sample preparation and can be configured to handle any sample size from a large surface to a few microns. The wide range of EDXRF spectrometers from SPECTRO Analytical Instruments and EDAX, member companies of AMETEK Inc.‘s Materials Analysis Division, provide solutions to many elemental analysis tasks in forensic investigation and archaeometry. 

Elemental analysis and the measurement of the ratio of their isotopes are well established techniques in geochemistry, extensively used for geological dating and for “fingerprinting” rocks, minerals and ceramics. The so-called Rare Earth Elements (REE’s) are widely used as diagnostic indicators, requiring accurate measurements at extremely low concentrations. A related technique, isotope dilution, is an evaluation method that can provide extremely precise measurements of trace element concentrations in geological samples. Isotope dilution is also often used in the preparation of standard reference materials (SRM’s). Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a widely used analytical method for such measurements, in which a solution of the sample is introduced into the high temperature environment of inductively coupled plasma. The plasma atomizes the sample and then ionizes the atoms (isotopes). The resulting ions are then transferred into a mass spectrometer that separates them according to their mass/charge ratios. Most instruments scan across a range of mass numbers, measuring each isotope sequentially. Because only one mass/ charge ratio is measured at a time, any fluctuations due to the sample introduction process, the plasma, or the detection system can introduce errors in the observed isotope ratios. Furthermore it may be desirable to measure a range of elements to establish an elemental “fingerprint” of the sample and to allow evaluation of various calculation strategies using different isotope combinations. Today’s instruments often suffer from the limitation of measuring at best only a narrow mass range. Others work with a pulsed ion beam, limiting the sensitivity and the dynamic working range. Instruments that scan relatively slowly or over a limited mass range are also clearly at a disadvantage when handling transient signals, as in hyphenated measurements with techniques like HPLC or sample introduction by laser ablation. Instrument technology has evolved to reduce these problems, but until now the majority of ICP-MS instruments have relied on scanning to a greater or lesser extent, and its attendant problems. 

A fully simultaneous ICP-MS, based on a compact Mattauch-Herzog geometry with a permanent magnet and a large, spatially resolving semiconductor ion detector covering the complete inorganic relevant mass range from ⁶Li to ²³⁸U in a single measurement, has been used to determine isotope ratios and assess achievable isotope ratio precisions. Measurements of the ^235/238U isotopic ratio, chosen as example for an isotopic system with a disparate isotope ratio, yielded a precision of 0.05% relative. To evaluate the expected multi-isotope ratio measurement capabilities of the system used, several isotope ratios spanning a wide range (^6/7Li, ^84/86Sr, ^87/86Sr, ^88/86Sr, ^204/207Pb, ^206/207Pb and ^208/207Pb) were measured simultaneously, using a synthetic multi-element standard as sample. Very satisfying isotope ratio precisions, between 0.5 and 0.04% relative, depending on the isotope ratio in question were found during the simultaneous multi-isotope ratio measurements. Together with a brief description of the system and measurement procedures employed for this technical note, the results achieved are assessed in view of other existing ICP-MS-based isotope ratio techniques. 

Mass spectrometry has become a popular and widely used technique in the pharmaceutical industry for the analysis and identification of organic compounds. The same basic principle can also be applied to elemental analysis, and ICP-MS, in which a mass spectrometer is coupled with inductively coupled plasma as the ion source, is one of the most sensitive techniques available for the detection and quantification of metallic impurities and other inorganic substances in pharmaceutical products. Such substances can be present in pharmaceutical products for a number of reasons, occurring as active ingredients, as impurities in raw materials and as contaminants. Some, particularly the “heavy metals”, are known for their toxicity, and as such are tightly controlled by regulation. Because of the repetitive dosing involved in most treatment regimes, permitted levels have to take into account the cumulative exposure to toxic elements, driving down the Limits of Detection required from analytical procedures.

For quality control purposes, the ability to screen for a number of metallic elements at low levels may be required. On the other hand, in products such as dietary supplements, some elements may be present at relatively high concentrations. The ideal analytical technique for the elemental analysis of pharmaceutical products combines the ability to measure a wide range of elements at trace levels and the wide dynamic range needed to handle higher concentrations. Samples may vary from raw materials, intermediates, process chemicals and solvents to finished products, so analytical techniques must be able to handle a wide range of sample matrices. Any procedure used must also comply with the quality protocols used in the pharmaceutical industry such as US FDA 21 CFR Part 11. New proposed guidelines from the US Food and Drug Administration (FDA) describe elemental impurity limits in pharmaceuticals and analytical procedures.

The two analytical techniques described in these guidelines are Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma–Mass Spectrometry (ICP-MS). The new SPECTRO MS is the world’s first fully simultaneous ICP-MS system. Simultaneous ICP-MS has a number of advantages over conventional instrumentation, and this paper describes the design of this revolutionary instrument and gives some examples of its application in the pharmaceutical industry. ICP-MS can also be combined with other techniques such as HPLC and IC: this paper deals only with stand-alone applications. 

Air pollution is a continuous concern of industries, governments, and populations worldwide. Particularly the harmful health effects of the exposure to heavy metals such as lead, arsenic, or cadmium absorbed into particulate matter, carried through the air, and introduced into the lungs and body are within focus.

These particles are principally generated by processes such as combustion. Monitoring and analysis of the elements present in these airborne particles is performed by a variety of organizations, - by industry, environmental protection agencies, as well as research institutes and testing laboratories for environmental and occupational health and safety.

Fortunately, modern laboratory-grade spectrometric analyzers are available that can handle the necessary analyses. They provide accurate, efficient airborne elemental particle identification and measurement. This paper explains several of the methodologies commonly employed for these applications focusing on ED-XHE ICP-OES, and ICP-MS technologies and describes the desirable attributes of suitable analyzer models for each.

Click here to download this paper