Trace level organics in hydrofluoric acid determined by attenuated total internal reflection infrared spectroscopy

Trace levels of organic impurities in the hydrofluoric acid solutions were measured by a multiple internal reflection infrared spectroscopic (MIRIS) technique. The MIRIS utilizes a clean attenuated total reflection (ATR) silicon crystal to extract organic impurities from the HF solutions. An open beam single-channel background spectrum combined with statistical analysis was used to ensure the reproducibility of absorbed organics measurement. The hydrofluoric acid samples were analyzed under an ultrapure nitrogen blanket to avoid airborne organics interferences. The adsorbed organic contaminants were found to randomly orient on the silicon ATR probe surface. A higher level of organic impurities was found in the more concentrated hydrofluoric acid solutions.