Line Source Atomic Absorption Spectrometry Research Articles

Spectral interferences of oxygen and water molecules in hydride generation atomic absorption spectrometry with quartz atomizers: Comparison of preconcentration and on-line atomization modes for As and Se determination

Absorption by molecular oxygen and gaseous water in the vicinity of As 193.7 nm and Se 196.0 nm analytical lines in quartz atomizers was studied by both line source atomic absorption spectrometry and high-resolution continuum source absorption spectrometry. Oxygen absorption has a structured spectrum whereas water has a pseudo-continuum structure in the studied range. The influence of relevant experimental parameters such as atomizer temperature, carrier gas flow rate, and oxygen/water concentration on absorption by oxygen/water molecules was investigated. Effect of molecular oxygen and water absorption on background correction and thus their influence on determination of As and Se by hydride generation atomic absorption spectrometry is discussed comparing two modes of operation: (i) conventional mode of hydride generation in absence of preconcentration and (ii) preconcentration (trapping) mode.

High-Resolution Continuum Source Atomic and Molecular Absorption Spectrometry—A Review

The present article gives an overview over the historic development, the instrumentation, the special features, and the applications of high-resolution continuum source atomic and molecular absorption spectrometry. The most obvious advantage is the need for only one single lamp for all elements and wavelengths, compared to one lamp for each analyte, as is necessary in line source atomic absorption spectrometry. The visibility of the spectral environment of the analytical line at high resolution greatly helps in method development and to avoid spectral interferences. The advanced simultaneous background correction automatically eliminates lamp flicker noise and continuous background absorption. Fine-structured background absorption may be removed using a reference spectrum and a least-squares algorithm. Because any wavelength between 190 nm and 900 nm can be accessed, the same equipment can be used for molecular absorption spectrometry, making possible the determination of non-metals, such as phosphorus, sulfur, and the halogens. Although commercial equipment for this technique has only been available for a few years, the technique has been accepted extremely well, and the number of applications that have been published using this technique has already reached an impressive number.

Investigation of artifacts caused by deuterium background correction in the determination of phosphorus by electrothermal atomization using high-resolution continuum source atomic absorption spectrometry

The artifacts created in the measurement of phosphorus at the 213.6-nm non-resonance line by electrothermal atomic absorption spectrometry using line source atomic absorption spectrometry (LS AAS) and deuterium lamp background correction (D 2 BC) have been investigated using high-resolution continuum source atomic absorption spectrometry (HR-CS AAS). The absorbance signals and the analytical curves obtained by LS AAS without and with D 2 BC, and with HR-CS AAS without and with automatic correction for continuous background absorption, and also with least-squares background correction for molecular absorption with rotational fine structure were compared. The molecular absorption due to the suboxide PO that exhibits pronounced fine structure could not be corrected by the D 2 BC system, causing significant overcorrection. Among the investigated chemical modifiers, NaF, La, Pd and Pd + Ca, the Pd modifier resulted in the best agreement of the results obtained with LS AAS and HR-CS AAS. However, a 15% to 100% higher sensitivity, expressed as slope of the analytical curve, was obtained for LS AAS compared to HR-CS AAS, depending on the modifier. Although no final proof could be found, the most likely explanation is that this artifact is caused by a yet unidentified phosphorus species that causes a spectrally continuous absorption, which is corrected without problems by HR-CS AAS, but which is not recognized and corrected by the D 2 BC system of LS AAS.

Progress in direct solid sampling analysis using line source and high-resolution continuum source electrothermal atomic absorption spectrometry

The literature about direct solid sample analysis of the past 10-15 years using electrothermal atomic absorption spectrometry has been reviewed. It was found that in the vast majority of publications aqueous standards were reported as having been used for calibration after careful program optimization. This means the frequently expressed claim that certified reference materials with a matrix composition and analyte content close to that of the sample have to be used for calibration in solid sample analysis is not confirmed in the more recent literature. There are obviously limitations, and there are examples in the literature where even calibration with certified reference materials did not lead to accurate results. In these cases the problem is typically associated with spectral interferences that cannot be corrected properly by the systems available for conventional line source atomic absorption spectrometry, including Zeeman-effect background correction. Using high-resolution continuum source atomic absorption spectrometry, spectral interferences become visible owing to the display of the spectral environment at both sides of the analytical line at high resolution, which makes program optimization straightforward. Any spectrally continuous background absorption is eliminated automatically, and even rapidly changing background absorption does not cause any artifacts, as measurement and correction of background absorption are truly simultaneous. Any kind of fine-structured background can be eliminated by "subtracting" reference spectra using a least-squares algorithm. Aqueous standards are used for calibration in all published applications of high-resolution continuum source atomic absorption spectrometry to direct solid sample analysis.

Investigation of chemical modifiers for phosphorus in a graphite furnace using high-resolution continuum source atomic absorption spectrometry

Phosphorus is not one of the elements that are typically determined by atomic absorption spectrometry, but this technique nevertheless offers several advantages that make it attractive, such as the relatively great freedom from interferences. As the main resonance lines for phosphorus are in the vacuum–ultraviolet, inaccessible by conventional atomic absorption spectrometry equipment, L´vov and Khartsyzov proposed to use the non-resonance doublet at 213.5 / 213.6 nm. Later it turned out that with conventional equipment it is necessary to use a chemical modifier in order to get reasonable sensitivity, and lanthanum was the first one suggested for that purpose. In the following years more than 30 modifiers have been proposed for the determination of this element, and there is no consensus about the best one. In this work high-resolution continuum source atomic absorption spectrometry has been used to investigate the determination of phosphorus without a modifier and with the addition of selected modifiers of very different nature, including the originally recommended lanthanum modifier, several palladium-based modifiers and sodium fluoride. As high-resolution continuum source atomic absorption spectrometry is revealing the spectral environment of the analytical line at high resolution, it became obvious that without the addition of a modifier essentially no atomic phosphorus is formed, even at 2700 °C. The absorption measured with line source atomic absorption spectrometry in this case is due to the PO molecule, the spectrum of which is overlapping with the atomic line. Palladium, with or without the addition of calcium or ascorbic acid, was found to be the only modifier to produce almost exclusively atomic phosphorus. Lanthanum and particularly sodium fluoride produced a mixture of P and PO, depending on the atomization temperature. This fact can explain at least some of the discrepancies found in the literature and some of the phenomena observed in the determination of phosphorus using line source atomic absorption spectrometry.

Determination of cobalt in biological samples by line-source and high-resolution continuum source graphite furnace atomic absorption spectrometry using solid sampling or alkaline treatment

Two procedures for the determination of Co in biological samples by graphite furnace atomic absorption spectrometry (GF AAS) were compared: solid sampling (SS) and alkaline treatment with tetramethylammonium hydroxide (TMAH) using two different instruments for the investigation: a conventional line-source (LS) atomic absorption spectrometer and a prototype high-resolution continuum source atomic absorption spectrometer. For the direct introduction of the solid samples, certified reference materials (CRM) were ground to a particle size ≤50 μm. Alkaline treatment was carried out by placing about 250 mg of the sample in polypropylene flasks, adding 2 mL of 25% m/v tetramethylammonium hydroxide and de-ionized water. Due to its unique capacity of providing a 3-D spectral plot, a high-resolution continuum source (HR-CS) graphite furnace atomic absorption spectrometry was used as a tool to evaluate potential spectral interferences, including background absorption for both sample introduction procedures, revealing that a continuous background preceded the atomic signal for pyrolysis temperatures lower than 700 °C. Molecular absorption bands with pronounced rotational fine structure appeared for atomization temperatures >1800 °C probably as a consequence of the formation of PO. After optimization had been carried out using high resolution continuum source atomic absorption spectrometry, the optimized conditions were adopted also for line-source atomic absorption spectrometry. Six biological certified reference materials were analyzed, with calibration against aqueous standards, resulting in agreement with the certified values (according to the t-test for a 95% confidence level) and in detection limits as low as 5 ng g −1.

Graphite furnace atomic absorption spectrometry using a linear photodiode array and a continuum source

A graphite furnace atomic absorption spectrometer is described based on a continuum source and a linear photodiode array detector (LPDA). Wavelength integrated absorbance is computed which asymptotically approaches a maximum as more pixels are used to cover the absorption profile. The read noise of the LPDA was 3800 electrons. Absorbance noise computed from the propagation of errors and LPDA read noise accurately predicts the experimental results. Absorbance noise decreases as the entrance slit is increased and increases as the number of pixels in the calculation is increased. The best detection limits were found with an entrance slit-width of 500 µm and 16–32 pixels. The detection limits for Cd, Cu and Ni were comparable to line source atomic absorption spectrometry. Gated detection was necessary to eliminate source flicker when large numbers of pixels were used and in the presence of background absorbance.