ICP-MS Sample Preparation

Inductively coupled plasma mass spectrometry (ICP-MS) is applicable to a wide variety of sample types; therefore, it is used in many different industries.

To be processed efficiently in the plasma, samples must be in either gas or vapor (aerosol) form. So, while gases can be analyzed directly by the plasma (e.g., when separated by gas chromatography), solids and liquids have to be converted to aerosol form using either a nebulizer (for liquids) or an ablation device (for solids).

In most routine ICP-MS analyses, the sample is introduced as a liquid using a nebulizer and spray chamber. The nebulizer uses supersonic expansion of gas to turn the liquid into a fine mist, and the spray chamber then removes any droplets that are too large to be processed in the plasma. This occurs at the sample interface of the instrument.

Liquid samples are typically digested and then reconstituted in an aqueous matrix to stabilize elements as an ionic solution. The matrix typically contains 2% nitric acid, and may have 0.5% hydrochloric acid added to stabilize certain elements. The final composition of any matrix is highly dependent on the nature of the analytes being measured.

Liquids can be analyzed directly without dissolution using a standard ICP-MS introduction kit—provided the TDS (total dissolved solids) level is below ~0.5%. Above this level, the TDS may precipitate in the nebulizer or overload the plasma, either of which alter the way the sample is processed in the plasma. This can result in a data collection issue called drift. Specialized nebulizers and spray chambers may be required to counteract drift; more commonly, sample dilution is performed.

With solid samples, digestion in strong and hot acids is the typical protocol. The acids themselves range from simple nitric acid (for relatively simple matrices) to hydrofluoric acid (for samples containing high silicon dioxide content). Samples containing organic matter may also have hydrogen peroxide added to them during the digestion step because H₂O₂ breaks down organic matter efficiently.

Solid samples can also be directly turned into aerosols several different ways, the most common being laser ablation (LA), spark ablation, or electrothermal vaporization (ETV). In all of these methods, the samples are converted to an aerosol and transported to the plasma with inert gas.

• Laser Ablation Adaption Kit
• iCAP Q ICP-MS Laser Ablation Adaption Kit
• CETAC U5000AT+ Ultrasonic Nebulizer
• ELEMENT Series ICP-MS
• Neptune Plus High Resolution Multicollector ICP-MS