Electrospray as a new sample introduction technique for the flame photometric detector.
Date
1997
Authors
Khayamian, Taghi.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
In atomic and molecular flame spectroscopy, with combustion flames and plasma, the quality of analytical results for liquid samples is limited by the means of sample introduction, especially when sample flow rates are small. In this project, electrospray was examined as a method to introduce small liquid flows (typically 10 $\mu$L/min) into a flame photometric detector (FPD). This method was used to introduce ionic and nonionic sulphur and phosphorus compounds as well as ionic metal compounds into the FPD. Atomic lines or molecular band spectra from a variety of elements (K, Sr, Sc, S, P, Mn, Mg, Ni, Cu, B, Se, As) were recorded. To demonstrate the potential of electrospray as a new sample introduction technique for the FPD, mass detection limits of selected elements were measured. Detection limits varied from 0.6 ng Cu/s to 18 ng In/s. The dynamic range for Cu was about two and half decades. The application of the electrospray-FPD for phosphorus and sulphur analysis in biological samples was confirmed by obtaining the phosphorus spectra for adenosine 5$\sp\prime$-monophosphate (AMP), DNA, lecithin, and sulphur spectrum for glutathione. The phosphorus dynamic range (AMP) was more than two and half orders of magnitude while a quadratic response with two decades for sulphur (glutathione) was obtained. The detection limit for sulphur was 1 ng S/s. The signal to noise ratio for P and Cu increased at lower flow rates, suggesting that detection limits could be improved with lower flows.
The noise power spectrum was used as a diagnostic tool to obtain the limiting noise on the signal. Flicker noise and interference noise appeared to dominate and could be reduced by about a factor of two by using an internal standard in dual channel mode. It was also found that, at high voltages, the noise on the electrical current had a correlation coefficient of 0.806 with the optical noise, indicating that the electrical signal may be an interesting field for further investigation. At high voltages (ca. 5000 V) corona discharges caused strong emission of the nitrogen second positive system in the flame. This observation suggested that metastable nitrogen species in a flame may provide additional excitation pathways for the analyte.
Thesis (Ph.D.)--Dalhousie University (Canada), 1997.
The noise power spectrum was used as a diagnostic tool to obtain the limiting noise on the signal. Flicker noise and interference noise appeared to dominate and could be reduced by about a factor of two by using an internal standard in dual channel mode. It was also found that, at high voltages, the noise on the electrical current had a correlation coefficient of 0.806 with the optical noise, indicating that the electrical signal may be an interesting field for further investigation. At high voltages (ca. 5000 V) corona discharges caused strong emission of the nitrogen second positive system in the flame. This observation suggested that metastable nitrogen species in a flame may provide additional excitation pathways for the analyte.
Thesis (Ph.D.)--Dalhousie University (Canada), 1997.
Keywords
Chemistry, Analytical.