Teledyne Leeman Labs Blog

In this edition of the blog, we will continue to examine various methods of sample preparation.

Dry Ashing

Samples containing a high percentage of organic matter (biologicals and foodstuffs, for example) can be prepared by a procedure known as "dry ashing" With this technique, an amount of sample is heated in a crucible over a flame or in a muffle furnace. The use of a muffle furnace is preferred as it permits greater control of the temperature. The sample residue is then dissolved, and the analysis is performed.

What Is ICP Heavy Metal Analysis?

Heavy metals, including arsenic (As), cadmium (Cd), chromium (Cr), lead (PB) and mercury (Hg) occur naturally in nature, and in low concentrations pose little health risk. When concentrations increase however, their presence can be toxic to plants, animals and humans. Because they are systemic toxins, routine testing is used to determine their presence and concentration. The United States Environmental Protection Agency (U.S. EPA), and the International Agency for Research on Cancer (IARC), classifies these metals as either “known” or “probable” human carcinogens.¹

This is part 2 of the Inductively Coupled Plasma Optical Emission Spectrometry series.  Part 1 described what ICP-OES is and how it works.  Part 2 will be an overview and cover some of the components.

Overview

Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) is a multi-element, trace-analysis technique used to measure the concentration of various elements in a variety of sample matrices. Also known as Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), the technique is capable of measuring the majority of the elements in the Periodic Table and is currently one of the most widely used methods for elemental analysis today.

A majority of samples analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) are introduced to the instrument as solutions. Sample preparation for analysis by ICP-OES may be as simple as filtering and adding acid to a liquid sample or be a lengthy, complex procedure to dissolve a solid. In order to obtain the best possible analytical results, an appropriate technique must be used to convert the sample into a usable solution. Part 1 and 2 of this blog will briefly examine some of the more commonly used sample preparation techniques, and highlight their respective advantages and disadvantages.

For most applications, the ICP-OES requires the sample be in liquid form. Solid samples can be acid digested or dissolved in a solvent suitable for use with the ICP.

Liquid samples are delivered to the ICP using a sample introduction system, which is made up by the torch, spray chamber, nebulizer, peristaltic pump and tubing. In this blog post, we will look at the nebulizer.

Inductively Coupled Plasma Optical Emission Spectrometry is a multielement technique that uses a high temperature plasma to excite atoms within the sample to the point where they emit wavelength-specific photons of light.  Each element emits its own characteristic wavelengths and the number of photons emitted is directly proportional to the concentration of that element in the sample.