Thirty years of cometary spectroscopy from McDonald Observatory

► We present spectroscopic data from McDonald Observatory covering almost 30 years and 130 comets. ► We find that 9% of the comets are carbon-chain depleted by the strictest definition (25% by a more customary definition). ► Jupiter Family comets are more likely to be depleted than Long Period comets. ► On average, there are few compositional differences with increasing orbital semi-major axis.