The Hyphenation of High-Performance Liquid Chromatography with X-ray Fluorescence for Universal, Flow-Through,...

Current detectors used in liquid chromatography are still lacking in what is desired of an ideal detector. One of those characteristics is the universal response. In this work, the novel use of X-ray fluorescence as a complementary, flow-through, universal detector was developed in hyphenation with reversed-phase chromatography. Monte Carlo simulations were performed to aid in the creation of the HPLC-XRF setup and study the influence of parameters involved. A proof of principle was established for the analysis of organobromines of environmental concern, and calibration curves were created, which show LODs below 0.3 mM for all tested compounds and good linearity between 0.2 and 20 mM (R² > 0.99). The relative standard deviation of the peak areas varied between 10.47 and 1.06% with an average of 3.67%. The universal character of XRF was shown via flow injection analysis, allowing the use of element-based calibration curves instead of compound-specific ones. This conclusion can be further extended to other elements detectable by XRF. Sensitivity is currently a limitation but can be further improved through multidetector setups, improved acquisition hardware and software, and techniques such as stop-flow chromatography and preconcentration. The isocratic and gradient separation of brominated species was also performed to illustrate the potential of HPLC-XRF in separation studies. While simulations predicted a minor influence of mobile phase composition on the response, this effect proved to be negligible under the experimental conditions.