Fluorescence interference method

Fluorescence Interference. The historical drawback to widespread use of Raman spectroscopy has been the strong fluorescence background exhibited by many materials, even those which are nominally nonfluorescent. This fluorescence often arises from an impurity in the sample, but may be intrinsic to the material being studied. Several methods have proved useflil in reducing this background. One of the simplest is sample purification. 

Pullin, M. J., and Cabaniss, S. E. (1995). Dissolved organic-matter fluorescence as a mixing tracer—Quantitation of interferences, method sensitivity, and preliminary data. Abstr. Papers Am. Chem. Soc. 210, 37-IEC Part 1. 

Fluorescence Of Monolayers Containing Pyrene-Labeled Probes. A fluorescence probe method was also used as a complementary technique to study the thermodynamics of SA film formation. Mixed monolayers containing the fluorescence probe pyrene hexadecanoic acid, Py-C16, in host fatty acids of different lengths were prepared by adsoiption from solutions containing mostly the host fatty acid and a small fraction of Py-C16 (approximately 1 to 5 mol %). All monolayers were prepared under equilibrium adsoiption conditions. For fluorescence measurements only A1 substrate was used because when glass is used an impurity fluorescence from glass interferes with the pyrene fluorescence. 

Time-resobed resonance Raman spectrometry is a technique that allows collection of Raman spectra of excited state molecules. It has heen used lo study in-lermediaies in enzyme reactions, the spectra of carotenoid excited slates, ultrafasi electron transfer steps, and a variety of olher biological and bioinoiganic processes, I inie discrimination methods have been used to overcome a major limitation of resonance Raman spectroscope, namelv. fluorescence interference either by the analyte itself or by other species present in the sample. 

The atomic absorption method for determining the concentration of metallic elements has now gained wide acceptance. Instrumentation is relatively inexpensive and simple to use. Analytical interferences are less prevalent than with most other techniques means of recognizing and combating the interferences that do exist are described. The article discusses the basic principles of atomic absorption and also describes the fundamental design and modern improvements in the major components of instrumentation hollow-cathode lamps, burners, photometers, and monochromators. Atomic absorption is compared with some of its rival techniques, principally flame emission and atomic fluorescence. New methods of sampling and the distinction between sensitivity and detection limit are discussed briefly. Detection limits for 65 elements are tabulated. 

Chlorophyll a fluorescence induaion is a widespread method to evaluate the photosynthetic activity. This method is noninvasive, highly sensitive, fast, and easily measured. When chlorophyll molecules in photosystem II absorb light, that light may be assimilated into the hght reactions of photosynthesis or may be released as fluorescence or heat energy. In vivo fluorescence increases when photosynthesis declines or is inhibited. Numerous environmental f ors can affect the rate of electron transport between photosystem II and photosystem I due to interference with electron carriers between the two photosystems. For example, when the diuton is added in the measured sample, electron transport from photosystem II to photosystem I is blocked resulting in maximum fluorescence. This method was often employed to detect the photosynthetic activity of immobilized photosynthetic material. ... 

Importantly it has been shown that these fluorescent staining methods do not interfere with subsequent protein identification by MS (Lauber et al., 2001 Patton, 2000). 

A simple and fast flow injection fluorescence quenching method for the determination of low levels of iron(III) in water has been developed. For this purpose, a preconcentration minicolumn consisting of cation-exchange resin was coupled to the FIA system. The use of mini-column in the system provided an improvement in sensitivity and the developed FIA method was successfully applied to the on-line determination of low levels of iron in real samples without the pre-concentration process. Fluorimetric determination was based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully applied to the determination of low levels of iron in real samples (river, sea, and spring waters). 

Munro et al. showed separation and detection of amino acids on microchips using an indirect fluorescence detection method. Figure 36.10 shows application of this method to urine samples with no pretreatment other than dilution in the appropriate separation buffer. Abnormal amounts of amino acids can easily be detected in the two patient samples compared to the healthy control sample. An absorbance detection based approach was utilized for the clinical analysis of calcium ion in serum, which is important in the regulation of a number of physiological processes. Beads with an immobilized calcium reactive dye were placed into the detection region, and the samples mobilized past the beads using electrophoretic flow. While a true separation was not intended, the interference... 

Fig. 7.19 Measurements of the hfs splittings in the 7 5 /2 ground state of Cs atoms with the pulse-train interference method. Excitation occurs on the D2 line aiX = 852.1 nm with a repetition rate f = Av/q with = 110. (a) Experimental arrangement (b) transmission of the probe pulse as a function of / (c) fluorescence intensity 7fi(/) as a function of / with a modulated small external magnetic field and (d) as a function of the delay time At at a fixed repetition frequency / [902]...

The fluorescence labeling method can be more informative and direct, because the data report on the phenomena of the subjects studied. It is applied in surfactant/polymer systems [31] and the study of lipid membrane [32], but is rarely used in surfactant/surfactant systems. Also, there is always a question of whether the fluorescent-labeled molecule interferes with the system under study. 

X-ray fluorescence (XRF) method. At first, an in-house probe reaction method was used to detect the presence of Pt within the SCR catalyst. The reaction system measured the conversion of ethylene to ethane at room temperature, allowing for detection of Pt metal below 0.(X)1 wt % (10 ppm). The presence of Fe, Cu, or Ni did not interfere with the ethylene hydrogenation technique. 

Open-column reversed-phase chromatography has also been employed for analysis of retinol from plasma extracts, either in micro mode (50-pm diameter C18 particles, column dimensions 0.5 X 5 cm) or macro mode (column dimensions 1.5 X 6 cm), using elution with methanol water (90 10) (122). Limit of detection (fluorometric determination in collected fractions) was 0.044 pM (1.25 pg retinol/dL) for the microcolumn method, with 0.1 mL serum used. The major fluorescent interference in serum (phytofluene) was retained on the column under these elution conditions. 

The intensity, lifetime of the excited state, and polarization of the fluorescence of organic molecules in solution point to electric dipole radiation. Direct proof of this was obtained for fluorescein by Selenyi (1911, 1939) using his wide angle interference method and has been recently confirmed by Freed and Weissman (1941). 

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