The need for process control has led to the development of improved instrumentation for measuring chemical contents of process streams. In many instances, on-line X-ray Fluorescence (XRF) analysis represents a straightforward method to accomplish these kinds of analyses. The sample preparation is often easy compared to many other methods and the XRF analyzer can be calibrated with process stream or artificial standards. Results are obtained in a time frame suitable for closed-loop control strategies. The Courier 10 is a new, compact on-line XRF analyzer which has been developed for chemical and petrochemical process applications such as sulfur and/or lead in gasoline; calcium in polymers; and chrome, iron ,nickel in metal treatment baths.