Electrode positioner for laser-enhanced ionization spectrometry

Havrilla, George J.; Green, Robert B.

doi:10.1021/ac00224a038

Cited by 7 publications

(7 citation statements)

References 10 publications

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“…The present results emphasize the need for the control of the variables identified here for maximum sensitivity and reproducible results for valid comparisons. A versatile electrode positioner is a necessity for maximizing LEI signals (13). The LEI signal delay characteristics reported in this paper may be useful for monitoring flame processes.…”

Section: Discussionmentioning

confidence: 93%

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Evaluation of plate electrodes for laser-enhanced ionization spectrometry

Havrilla¹,

Green²

1980

Anal. Chem.

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Section: Discussionmentioning

confidence: 93%

“…The cathodes are 30 mm plates, VAC mode, centered at 23 mm above the burner head. Excitation height above the burner head: (a) 9.5 mm; (b)13 mm; (c) 18 mm; (d) 23 mm; (e) 28 mm; (f) 33 mm.excitation high on the plates, the indium LEI signal is suppressed at low sodium concentrations because the laser-related…”

mentioning

confidence: 99%

Evaluation of plate electrodes for laser-enhanced ionization spectrometry

Havrilla¹,

Green²

1980

Anal. Chem.

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“…The high fields near small-diameter rods accentuate the sheathing effects discussed earlier. Thus, flat electrodes (Figure 7d) are preferable to rods for LEI (19). As normally used, these parallel plates are held at high negative potential, and the burner head is used as the anode (Figure 6c).…”

Section: Organic Acid Organic Basementioning

confidence: 99%

“…The spaee-charge-based ionization interference has been a prime concern in developing analytical LEI (19,26). Although plate electrodes ( 19) and the water-cooled immersed electrode (24) have improved the tolerance of LEI to highly ionizable matrices, signal recovery still may vary with matrix composition.…”

Section: Analytical Properties and Applicationsmentioning

confidence: 99%

Laser-enhanced ionization spectrometry

Travis¹,

Turk²,

Green³

1982

Anal. Chem.

122

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“…The change in ionization rate is monitored experimentally by applying a high voltage across the flame and synchronously detecting current changes resulting from excitation with a pulsed or chopped laser. Previous research has developed theoretical (1-4) and instrumental aspects (5)(6)(7)(8)(9) and has demonstrated the analytical capabilities (6,10,11) and matrix effects (8,9,12,13) of LEI. Most of the analytical research has been carried out With pulsed dye lasers with pulse durations on the order of a microsecond or less.…”

Section: Literature Citedmentioning

confidence: 99%

Continuous wave excitation in laser-enhanced ionization spectrometry

Havrilla¹,

Weeks²,

Travis³

1982

Anal. Chem.

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consistently low values for the number of electrons, n, calculated from the Nerst plot, due to the poor electrode kinetics.In light of these results, a new cell was constructed with an electrode consisting of a platinum film vapor deposited on glass. With this electrode, cyclic voltammograms of ferricyanide in sodium nitrate showed more nearly reversible behavior (k,h = 1.6 X cm/s) vs. literature values near 6 X cm/s for reduction in phosphate buffer (24) and absorbance changes occurred much more rapidly than on tin oxide electrodes. In potential step experiments with 0.5 mM ferricyanide under diffusion controlled conditions, an absorbance change of 0.1 absorbance unit occurred in less than 1 s, and ca. 95% of the full absorbance change (0.402 absorbance unit) was observed within 30 s. Titration of ferricyanide on Pt gave an n value of 0.93 and Eo' = 431 mV vs. NHE from the slope and intercept, respectively, of a plot of log AA/ (AA,, -AA) vs. E , according to the Nernst equationthe applied potential, [O] and [R] are the concentrations of the oxidized and reduced species, respectively ([Fe(CN)6]3-and [Fe(CN),]'-), AA is the absorbance change relative to the fully reduced spectrum, and AAmm is the maximum absorbance change between fully oxidized and fully reduced states.It has been shown that the FOTL cell gives excellent spectral response and is capable of providing an optical pathlength of 1 cm with a volume of less than 20 pL. Since there is no need for a transparent or highly reflective electrode, virtually any planar electrode material may be used, although reasonably smooth electrodes will afford the best results. The cell is small enough to fit into the sample chamber of a commercial spectrophotometer and could be interfaced by the use of lenses to direct the sample beam into the entrance fiber and collect the cell output beam from the exit fiber. In a conventional double-beam-in-time instrument, it may be necessary to attenuate the reference beam with a neutral density filter to keep the spectral recording on scale, although this procedure may decrease the signal to noise ratio somewhat.The flow-through geometry used here is attractive for repetitive analysis of small samples by injection into the cell with a syringe. The volume of the cell could be readily reduced to ca. 6 ML while retaining the present thickness and optical pathlength, by simply reducing the fiber array width to 3 mm, and could be further reduced to less than 1 pL with a slight 5 4 , 2566-2570 sacrifice in optical sensitivty. Such a cell would be of great value as a flow-through detector, especially for applications requiring low dead volume, such as microbore liquid chromatography. The availability of such a detector would permit the separation and quantitation of mixtures of electroactive and/or optically absorbing analytes without dead volume associated with separate detectors.The ability to monitor spectrally a very thin film of solution at the surface of an electrode is of great importance in mechanistic and kinetic studies. The FOT...

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Electrode positioner for laser-enhanced ionization spectrometry

Cited by 7 publications

References 10 publications

Evaluation of plate electrodes for laser-enhanced ionization spectrometry

Evaluation of plate electrodes for laser-enhanced ionization spectrometry

Laser-enhanced ionization spectrometry

Continuous wave excitation in laser-enhanced ionization spectrometry

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