Chemiluminescent species

The flame-photometric detector (FPD) is selective for organic compounds containing phosphoms and sulfur, detecting chemiluminescent species formed ia a flame from these materials. The chemiluminescence is detected through a filter by a photomultipher. The photometric response is linear ia concentration for phosphoms, but it is second order ia concentration for sulfur. The minimum detectable level for phosphoms is about 10 g/s for sulfur it is about 5 x 10 g/s. 

Anions of another group were derivatized with formation of gaseous chemiluminescing species. Chemical reaction - gas extraction has been used with chemiluminescence detection in the stream of canier gas in on-line mode. Rate of a number of reactions has been studied as well as kinetic curves of extraction of gaseous products. Highly sensitive and rapid hybrid procedures have been developed for the determination of lO, BrO, CIO, CIO, NO,, N03, CrO, CIO, Br, T, S, 803 with detection limits at the level of pg/L, duration of analysis 3 min. 

Emission of li t accompanying the passage of an electric current through aqueous solutions and arising from chemical reactions of chemiluminescent species produced during electrolysis. 

Apart from the obvious dependence of the output of a given detector to the concentration of the chemiluminescent species, several other factors also affect the output [13] ... 

It solely operates on the principle of photon emission. If P- or S-containing hydrocarbons are ignited in a hydrogen-rich flame, it gives rise to chemiluminescent species spontaneously which may subsequently be detected by a suitably photomultiplier device. Hence, FPD is regarded as a specific detector for P- or S-containing compounds. 

In a hydrogen-rich flame, combustion of samples containing phosphorus and/or sulfur results in the formation of chemiluminescent species which emit light characteristic of the heteroatom introduced into the flame. Selection of an interference filter with a 394- or 526-nm bandpass allows selectivities for sulfur and phosphorus respectively. Recent work by Krost and co-workers (27) found that a 690-nm filter showed selectivity for some nitrogen-containing compounds. 

The response of phosphorus in the FPD was determined to be linear while that of sulfur varied such that the square root of the response was proportional to concentration. This prompted researchers to propose a mechanism in which S2 was formed and was the chemiluminescent species. The following mechanism has been proposed (28) ... 

Luminogenic. These are known as fluoroimmuno assays (FIAs) [183,184]. Some features are (i) labeling is inexpensive and not dangerous, (ii) luminescence detection is simple and rapid. Three types of labels are (i) photo-luminescent species, (ii) biolumi-nescent species, (iii) chemiluminescent species. 

Systems undergoing lipid peroxidation accumulate malonyldialde-hyde (see Chapters 2 and 5), as has been observed in many biological systems. The amount of malonaldehyde accumulated correlates well with the chemiluminescence intensity observed, although the chemiluminescent species and the aldehydic lipid peroxidation product are formed by different pathways and at different times during the process of lipid peroxidation. 

Figure 15.1 Graphical representations of Metal-Enhanced Fluorescence (MEF) (Top and Middle) and for Metal-Enhanced Chemiluminescence (MEC) (Bottom). F - Fluorophore, C - Chemiluminescence species / probe and CL -Chemiluminescence.

An indirect chemiluminescence immunoassay is an assay, with another component than the primary chemiluminescent emitter coupled to the antigen or antibody. This can be a cofactor or a catalyst or even a molecule capable of converting a non-chemiluminescent precursor to a chemiluminescent or potentially chemiluminescent species. Most indirect assays are enzyme mediated. 

Flame Photometric (FPD) Flame excitation produces chemiluminescent species of S-and P-hydrocarbons 1-20 pg 103 for S lO-iforP High selective forS,P... 

When sulfur and phosphorus compounds are burned in an FDD-type flame, chemiluminescent species are produced that produce light at 393 nm (sulfur) and 526 nm (phosphorous). An optical interference filter passes the appropriate light to a photomultiplier tube, a sensitive photon detector. These detectors are known as flame photometric detectors (FPD).. ... 

A simple oxidative combustion does not generate a sulfur chemiluminescent species since SO2 does not chemiluminesce with ozone. Sulfur chemiluminescence detection has the advantage that SO is produced during FID operation. When SO reacts with ozone, a strong blue chemiluminescence signal is emitted by the resulting SOj. The signal is isolated from other radiations and detected by a photomultiplier tube. 

The electrogenerated chemiluminescence (ECl) of five l-amino-3-anthryl-9-propane derivatives has been studied in tetrahydrofuran. Emission from intramolecular exciplexes in ECl spectra and weak emission from the locally excited anthracene moiety were observed. The influence of triplet state interaction in ECl emission is discussed. The chemiluminescent decomposition of three a-peroxy-lactones gives CO2 and the corresponding ketone in high yield. The chemiluminescent species produced has been investigated in some detail by measurements of lifetime, energy-transfer activation parameters, and photochemical reactions. 

A schematic block diagram illustrating an entire DP-SCD detection system is shown in Fig. 2. An analytical system consists of a gas chromatogr h equipped with a split/splitless iigector with the option of a Pressurized Liquid Injection System (PLIS), wifli or without low diermal mass gas chromatogr q)hy apparatus, for sample introduction and sulfur speciation (if required) an electrically heated burner with an interface that controls the burner gas flows and temperature and a detector that contains a chemiluminescent reaction cell, ozone generator, optical filter, amplifier, and electronics. Lastly, a vacuum pump is used to keep file reaction cell under low pressure conditions to prevent loss of chemiluminescent species and to reduce collisional quenching. 

Similarly, the sulfur chemiluminescence detectors (SCD), namely fluorine-induced SCD (FSCD), ozone-induced SCD (O-SCD) and redox CD (RCD), work by first oxidising the organosulfur compound to give a species which may either react with fluorine or ozone to form a chemiluminescence species (HF and SOj, respectively). Reaction equations for O-SCD at 800-1100°C, developed by ref. [555], are ... 

---