Matrix effects in thermal lensing spectrometry:  determination of phosphate in saline solutions

Phillips, Charles M.; Crouch, S. R.; Leroi, G. E.

doi:10.1021/ac00121a024

Cited by 20 publications

(3 citation statements)

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“…61,62,81 Thermooptical spectroscopy methods were used for determining various organic compounds, primarily, those containing nitrogen or sulfur. 32 ± 36, 69, 71, 184, 379 In addition to studies of artificial mixtures serving for comparison of different modes of chromatographic separation, several studies were devoted to analysis of natural substances, 21,26,36,37 in particular, to analysis of industrial and household dyes, 306 and examination of the possibility of controlling products of organic synthesis. 25 Studies dealing with the determination of proteins at a level of 1 ± 100 ng 26,38,66,76,85,304,379 and amino acids at concentrations of y610 715 ± y610 712 mol litre 71 also deserve attention.…”

Section: Use Of Spectrophotometric Proceduresmentioning

confidence: 99%

“…Coarsely dispersed colloidal systems { Coarsely dispersed systems, viz., coarse slurries, suspensions and emulsions, are most often used in thermooptical measurements. 4,18,37,38 Several studies 54,295,529,555,556 were concerned with measurements of thermooptical deflection of the probe laser beam from the reflecting surface formed by large suspension particles. In the case of spontaneous formation of coarsely dispersed systems, the efficient power of the excitation beam decreases proportionally to the number of reflecting particles and, consequently, the detection sensitivity decreases, which limits the use of these systems in analytical practice.…”

Section: Colloidal Systemsmentioning

confidence: 99%

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Modern analytical thermooptical spectroscopy

Проскурнин¹,

Kononets²

2004

Russ. Chem. Rev.

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Section: Use Of Spectrophotometric Proceduresmentioning

confidence: 99%

Section: Colloidal Systemsmentioning

confidence: 99%

Modern analytical thermooptical spectroscopy

Проскурнин¹,

Kononets²

2004

Russ. Chem. Rev.

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“…The enhancement by the thermal lens effect, E (18,19), is presumably not an important factor in this case. This is due to the fact that even though the electrolyte (0.6 M K2[Sb2(d-tart)2]) provides up to 15% enhancement on the dn/dT value of the mobile phase compared to that of the pure water (20,21), the overall E value is very close to one because of the low laser intensity (i.e., 6 mW). This TL-CD LOD value is comparable with those obtained by using the FDCD and other home-built detectors which are based on optical rotation (22)(23)(24)(25)(26)(27).…”

Section: Resultsmentioning

confidence: 99%

Thermal lens-circular dichroism detector for high-performance liquid chromatography

Xu¹,

Tran²

1990

Anal. Chem.

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A novel and ultrasensitive chiral detector for high-performance liquid chromatography has been developed. This detector is based on the measurement of circular dichroism of chiral effluents by the thermal lens effect. In this instrument, the chromatographic effluent was sequentially excited by left circularly polarized laser light (LCPL) and right circularly polarized laser light (RCPL); both of these excitation beams were derived from the same argon ion laser whose linearly polarized output was transformed into circularly polarized light by means of a Pockels cell. The heat generated as a consequence of the sample absorption of the LCPL and RCPL was measured by the probe laser beam collinearly overlapping with the two excitation beams. A lock-in amplifier was used to measure the thermal lens-circular dichroism (TL-CD) signal which corresponds to the difference in the thermal lens signals produced by the LCPL and RCPL excitation beams. In addition to its high sensitivity, the advantages of this TL-CD chiral detector include its ability to provide, directly and in real time, information on the chirality (i.e., circular dichroism) and optical purity of chiral samples. A detection limit of 7.2 ng was achieved for (-)-tris(ethylenediamine)cobalt(III) (k' = 0.45) as well as for the (+)-tris(ethylenediamine)cobalt(III) (k' = 1.40) when these two enantiomers were chromatographically separated from the corresponding racemic mixture through the use of bis(mu-d-tartrato)diantiomonate(III) ion pair reversed-phase chromatography. This limit of detection was found by using a 10-microL flow cell and having 5-mm path length and 6-mW excitation laser beam (lambda = 514.5 nm) modulated at 2 Hz.

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Laser Spectrometric Techniques in Analytical Atomic Spectrometry

Axner

2000

Encyclopedia of Analytical Chemistry

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Laser light has a number of spectacular properties that make it useful for analytical spectrometry. One is that it has a high directionality (i.e. it looks like a real “beam”). This implies, among other things, that it can be focused down to micrometer‐sized spots. Another is that pulsed lasers can emit large amounts of light in very short pulses (often with a duration of 10 −9 − 10 −8 s). These two properties imply that laser light often can reach high irradiance (W m −2 ), which is of importance for a number of applications, not least when laser light is used for vaporization and/or atomization purposes of solid material. The most important attribute for spectroscopic applications, however, is that it often has a narrow frequency width (in the MHz–GHz range). This implies that laser light can induce one specific transition in one particular species at a time. The narrow frequency width is thus the basis for the high species selectivity that laser spectroscopic techniques possess. In addition, the combination of high irradiance and a narrow frequency width often gives laser light such staggering spectral irradiance (W m −2 Hz −1 ) that a significant fraction of the atoms under illumination can produce at least one detectable event during the interaction time (one or severalphotons or an ion–electron pair). This explains why laser spectroscopic techniques can benefit from high species sensitivity. The main purpose of this review article is to describe the theory and instrumentation for the field of laser spectroscopic techniques for analytical atomic spectrometry. This implies that techniques that use laser light for nonspectroscopic purposes, such as vaporization, and/or atomization purposes, e.g. laser ablation, laser‐induced plasma spectrometry, laser mass spectrometry and laser‐induced breakdown spectroscopy, will not be covered here. In addition, because atomic spectra in general consist of a few strong and narrow‐band transitions (whose widths often are comparable to those of the light from tunable laser systems and therefore seldom overlap with those from other atomic species) whereas those of molecules comprise a few broader, weaker and to a certain extent structured transition bands (which thus overlap more often with those of other molecular species), laser spectrometric techniques often show the highest sensitivity and selectivity when atomic species are detected. This is the main reason why this review focuses upon the use of laser spectrometric techniques for analytical atomic spectrometry. This implies, in turn, that laser‐based spectrometric techniques that predominantly detect molecules, e.g. Raman, thermal lensing and photoacoustic spectrometry, and spectrofluorometry, will not be discussed. This theory and instrumentation review focuses upon the most useful and versatile laser spectroscopic techniques for analytical atomic spectrometry. These techniques are based upon the concepts of fluorescence, ionization or absorption. Those based upon fluorescence are often referred to as either laser‐induced fluorescence (LIF) or laser‐excited atomic fluorescence spectrometry (LEAFS), whereas those based upon ionization are termed either laser‐enhanced ionization (LEI) or resonance ionization spectrometry (RIS). The working principles, instrumentation and present status of laser‐induced fluorescence/laser‐excited atomic fluorescence spectrometry (LIF/LEAFS) and LEI are covered in some detail in two separate sections, whereas RIS is covered more briefly. The reason for this is the broader versatility and applicability of LEI: it can be performed in a variety of atomizers, including those working under atmospheric pressure, whereas RIS has to be carried out in a vacuum and thus with significantly more complex instrumentation. However, because the laser instrumentation and the theoretical basis for all these techniques are quite similar, a short introduction to laser instrumentation and a theory section that outlines the common basic features of excitation of atoms by laser light precede the detailed descriptions. Those laser spectroscopic techniques that are based upon absorption and used for analytical atomic spectrometry are, nowadays, all performed in conjunction with some sort of modulation methodology (often wavelength‐modulation (WM)), frequently by the use of diode lasers owing to their rapid tunability. They are therefore often referred to as WM diode laser (atomic) absorption techniques and are covered in a separate section. Typical analytical qualities, e.g. limits of detection (LOD) and selectivity, as well as the typical strengths and limitations of each of these techniques, are given or discussed. It is concluded among other things that the most impressive performance of the LIF/LEAFS technique has been obtained together with the graphite furnace (GF) as atomizer, resulting in detection limits in the femtogram range and a very high selectivity for a large variety of elements. LEI, which has found its best use with the flame as atomizer, can provide LOD in the pg mL −1 range for many elements. It does not, however, show the same high selectivity as the LIF/LEAFS technique because it suffers from background effects when samples with high concentrations of easily ionized elements (EIEs) are analyzed. RIS combines a high sensitivity with an extraordinary selectivity, but instead has to pay the price of a more complex instrumentation. It was demonstrated earlier, for example, that the RIS technique is able to provide single atom detection (SAD). Because RIS in general is performed in a vacuum it can also provide good isotopic selectivity. Although not yet applied to a broad range of elements for analytical applications, it has shown impressive LOD (in the attogram range) and excellent isotopic selectivity (>10 9 ) under a few specific conditions. The wavelength‐modulation diode laser absorption spectrometry (WM‐DLAS) technique shows good promise for becoming a user‐friendly and widespread detection technique because it requires less complex instrumentation than most other laser spectroscopic techniques. Used with the GF as atomizer, LOD in the femtogram range have been achieved. The WM‐DLAS technique also has good ability to correct for various types of unstructured background absorption signals that might appear when samples with complex matrices are analyzed. One drawback, however, is that its applicability is still restricted owing to the limited availability of diode lasers that emit light in the visible and ultraviolet (UV) region. The WM‐DLAS technique, therefore, has been applied to only a limited number of elements so far. A common denominator for all these laser spectroscopic techniques is that they often have a large linear dynamic range (LDR). The LIF/LEAFS technique, for example, has demonstrated an LDR of 5–7 orders of magnitude. Finally, in addition to being used as sensitive and selective tools for analytical assessments, the laser spectroscopic techniques often show an excellent applicability to diagnostic studies (e.g. for the determination of processes such as atomization, diffusion, collision or ionization).

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Matrix effects in thermal lensing spectrometry: determination of phosphate in saline solutions

Cited by 20 publications

References 42 publications

Modern analytical thermooptical spectroscopy

Modern analytical thermooptical spectroscopy

Thermal lens-circular dichroism detector for high-performance liquid chromatography

Laser Spectrometric Techniques in Analytical Atomic Spectrometry

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