Infrared spectrophotometric analysis of medicinal gases for trace impurities.

The feasibility of examining medical gases for trace impurities, using an infrared spectrophotometer in conjunction with a 10 m gas cell, was investigated. Many of the impurities for which the USP includes limits were detected and measured at concentrations at or below those permitted by the USP; these include sulfur dioxide, carbon dioxide, carbon monoxide, and water. However, others (hydrogen sulfide, nitric oxide, and nitrogen dioxide) were not detected at these levels by this technique. Methane was found at low levels in some samples.