Atomic absorbance (AA) spectroscopy is one of the most common techniques for elemental analysis in the lab. Standard flame or graphite furnace AA can analyze most elements with little difficulty and with excellent detection levels. However, certain elements present particular difficulties with AA due to their atomic and chemical natures. On the periodic table, these elements generally lie along the boundary between the metals and the nonmetals. For these metalloid elements, the performance of AA can be improved with the introduction of an additional mechanism: hydride generation.

The hydride generation module carries out another important step in the treatment of the sample. In a standard flame AA instrument, the sample is typically dissolved, and the liquid sample is sprayed through a nebulizer into the flame, ionizing it for analysis. In the hydride generator, the aqueous sample is combined with acid and a strong reducing agent, such as sodium borohydride. The concentrations of the reducing agent and the acid are arranged to produce the optimal oxidation state in the element under scrutiny.

The result of the chemical reaction is to form a hydride, a binary compound containing just two elements: the element under investigation and hydrogen. For the elements for which this method is useful, these hydrides are gaseous and are liberated from the sample. The evolved gas then travels through an optical cell that is heated by the flame, allowing the spectrometer to measure the element. Both atomic absorption and atomic fluorescence are commonly used for the final measurement. By isolating the element of interest from potential interferences, the hydride generation method can provide a far better analysis of the element than would be possible with the raw sample.

The most important elements that can be analyzed with hydride generation are mercury and arsenic. Both are vital in environmental research. Hydride generation AA provides analysis that meets most global standards without the expense of more sensitive methods, such as ICP-MS. Mercury can exist in a gaseous state without the heating provided by the flame, so the technique is often referred to as “mercury cold vapor,” but it is essentially the same technique. Other elements that readily form hydrides and can be analyzed with the method include antimony, bismuth, germanium, lead, selenium, tellurium and tin. Detection using these methods is quite sensitive, with limits reaching sub-ppb levels for most of the relevant elements. Apart from environmental analysis and related safety testing, hydride generation applications are fairly minor.

All major AA vendors offer the option of hydride generation with their AA systems, making the top vendors in the overall AA market also the top suppliers for hydride generation AA. In addition to the major vendors, some smaller vendors place particular expertise emphasis on hydride generation systems. Among them are PS Analytical and Buck Scientific.

Hydride Generation AA at a Glance:

Leading Suppliers

• PerkinElmer

• Thermo Fisher Scientific

• Agilent

Largest Markets

• Environmental

• Academia

• Food

Instrument Cost

• $10,000–$40,000