Analysis of small droplets with a new detector for liquid chromatography based on laser-induced breakdown spectroscopy

• Published in: Spectrochimica acta. Part B: Atomic spectroscopy 2005-08, Vol.60 (7), p.993-1001
• Main Authors: Janzen, Christoph, Fleige, Rüdiger, Noll, Reinhard, Schwenke, Heinrich, Lahmann, Wilhelm, Knoth, Joachim, Beaven, Peter, Jantzen, Eckard, Oest, Andreas, Koke, Peter
• Format: Article
• Language: English
• Subjects: Droplet analysis; HPLC; LIBS
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/j.sab.2005.05.033

The miniaturization of analytical techniques is a general trend in speciation analytics. We have developed a new analytical technique combining high pressure liquid chromatography (HPLC) with laser-induced breakdown spectroscopy (LIBS). This enables a molecule-specific separation followed by an element-specific analysis of smallest amounts of complex samples. The liquid flow coming from a HPLC pump is transformed into a continuous stream of small droplets (diameter 50–100 μm, volume 65–500 pl) using a piezoelectric pulsed nozzle. After the detection of single droplets with a droplet detector, a Q-switched Nd:YAG Laser is triggered to emit a synchronized laser pulse that irradiates a single droplet. The droplets are evaporated and transformed to the plasma state. The spectrum emitted from the plasma is collected by a spherical mirror and directed through the entrance slit of a Paschen–Runge spectrometer equipped with channel photomultipliers. The spectrometer detects 31 elements simultaneously covering a spectral range from 120 to 589 nm. Purging the measurement chamber with argon enables the detection of vacuum–UV lines. Since the sample is transferred to the plasma state without dilution, very low flow rates in the sub-μl/min range can be realised.