Chemiluminescence direct

Intense and analytically useful direct chemiluminescence (CL) has been observed from a rather limited group of organic compounds. These include diacylhydraz-ides, indoles, acridines and acridans, polydimethylaminoethylenes, anthracenes, and aroyl peroxides. A substantial number of other kinds of compounds, when... 

Table 3 Determination of Some Drugs Using Direct Chemiluminescence... 

Some drugs will emit light under specific reaction conditions. The discovery of these direct chemiluminescent reactions has come about through trial and error. Table 3 lists some of these drugs and the method used for analysis. Other drugs that are not themselves chemiluminescent can be easily analyzed using a chemiluminescent system (Table 4). 

A. Crowson, R.W. Hiley, T. Ingham, T. Mccreedy, A.J. Pilgrim, A. Townshend, Investigation into the detection of nitrated organic compounds and explosives by direct chemiluminescent emission during thermally induced gas phase decomposition reactions , Anal. Commun. 34 (1997) 213-216. 

In this part of the chapter, we will briefly outline the main types of CL reactions which can be functionally classified by the nature of the excitation process that leads to the formation of the electronically excited state of the light-emitting species. Direct chemiluminescence is the term employed for a reaction in which the excited product is formed directly from the unimolecular reaction of a high-energy intermediate that has been formed in prior reaction steps. The simplest example of this type of CL is the unimolecular decomposition of 1,2-dioxetanes, which are isolated HEI. Thermal decomposition of 1,2-dioxetanes leads mainly to the formation of triplet-excited carbonyl compounds. Although singlet-excited carbonyl compounds are produced in much lower yields, their fluorescence emission constitutes the direct chemiluminescence emission observed in these transformations under normal conditions in aerated solutions ... 

The thermolysis of peroxyacetate [28] and substituted peroxybenzoates [29] gives both direct and indirect chemiluminescence. Thermolysis of peroxyacetate [28] in benzene solution at 100° gives very weak direct chemiluminescence. The emission is so weak that an emission spectrum could not be obtained. When biacetyl, which has a considerably higher quantum efficiency for phosphorescence than acetophenone (Backstrom and Sandros, 1958), is used... 

Thermolysis of peroxide [29c] in benzene solution generates a chemiluminescent emission whose spectrum is identical to the fluorescence spectrum of photoexcited p-dimethylaminobenzoic acid under similar conditions. Thus the direct chemiluminescence is attributed to the formation of the singlet excited acid. The yield of directly generated excited acid is reported to be 0.24% (Dixon and Schuster, 1981). Since none of the other peroxybenzoates generate detectable direct chemiluminescence it was not possible to compare this yield to the other peroxides. However, by extrapolation it was concluded that the dimethylamino-substituted peroxide generates excited singlet products at least one thousand times more efficiently than does the peroxyacetate or any of the other peroxybenzoates examined. 

Undoubtedly, the most characteristic property of 1,2-dioxetanes and a-peroxylactones is the fact that they emit light on thermal decomposition. Since in liquid media in the presence of molecular oxygen triplet excited states are efficiently quenched, the observed direct chemiluminescence is ascribed to the fluorescence of the carbonyl product. This fluorescence occurs usually at 420 10nm and corresponds to n n excitation.The shortest wavelength emission has probably been observed for the indole-1,2-dioxetane (17) that occurs at 320 nm. ... 

The kinetics of the thermal decomposition of 1,2-dioxetanes and a-peroxylactones are first order and are usually unimolecular. A variety of experimental methods can be used to monitor the rates. These include direct chemiluminescence of the excited carbonyl product,energy-transfer chemiluminescence of the chemienergized excited carbonyl product to an efficient fluorescer, dioxetane consumption or carbonyl product formation by nmr spectroscopy iodometry of the cyclic... 

The direct chemiluminescence quantum yield is given by Eq. 35, where is the singlet excitation quantum yield and 0 is the fluorescence quantum yield of the singlet excited carbonyl product. The latter is directly responsible for the observed chemiluminescence. If 0 is known from photoluminescence work, determination of 0° allows us to calculate the desired 0 -parameter. Frequently 0 is not known and it is necessary to measure it, using routine fluorescence techniques. 

For the experimental determination of the 0, it is necessary to quantify the light output of the direct chemiluminescent process. The experimental definition of the direct chemiluminescence quantum yield is given in Eq. 36, that is, the initial rate of photon production (/q ) per initial rate of dioxetane decomposition k )[D]o). Alternatively, the total or integrated light intensity per total dioxetane decomposed can be used. The /t )[Z)]o term is readily assessed by following the kinetics of the chemiluminescence decay, which is usually first order. Thus, from a semilogarithmic plot of the emission intensity vs. time, the dioxetane decomposition rate constant kjj is obtained and the initial dioxetane concentration [Z)]o is known,especially if the dioxetanes have been isolated and purified. In those cases in which the dioxetanes are too labile for isolation and purification, [/)]o is determined by quantitative spectroscopic measurements or iodometric titration. 

Once the standardized and calibrated direct chemiluminescence quantum yield (0 ) has been acquired experimentally, the singlet excitation yield (0 ) can be calculated for the chemienergized process from Eq. 35. However, as already stated, this requires that the fluorescence quantum yield (0 ) be known under the same experimental conditions at which 0 was determined. This is not always the case... 

In the case of fluorescence, that is, chemienergized by energy transfer, an energy acceptor is chosen that exhibits efficient fluorescence, for example, polycyclic aromatic hydrocarbons and, particularly, 9,10-disubstituted anthracene derivatives. Consequently, in the presence of such fluorescers (FI), the feeble direct chemiluminescence emission intensity is significantly enhanced. Such a phenomenon is commonly referred to as enhanced chemOuminescence (EC). 

In view of the fact that triplet excited states do not generally phosphoresce, neither the direct chemiluminescence nor the enhanced chemiluminescence (via triplet-triplet energy transfer) techniques are of much help in counting chemi-... 

De Boever J, Kohen F, Usanachitt C, Vandekerckhove D, Leyseele D, Vandewalle L. Direct chemiluminescence immunoassay for estradiol in serum. Clin Chem 1986 32 1895-900. 

Chemiluminescence has been used to assess phosphatidylcholine oxidation, and to measure the kinetics of decomposition of hydroperoxides formed during the oxidation of soya phosphatidylcholine. The direct chemiluminescence method correlated well with other methods of determining oxidation status (chemical, UV, HPLC, and microcalorimetry), and it was concluded that chemiluminescence was an ideal method for estimating the oxidation of phosphatidylcholine (and phospholipids in general). Kinetics measurements revealed that... 

A direct chemiluminescence assay for urinary pregnanediol 3-glucuronide employs the isoluminol conjugate (31) as tracer, with monoclonal antibodies. Specificity is excellent, the assay being sensitive to 30 pg.143 A solid-phase chemiluminescence assay for plasma progesterone uses as tracer the isoluminol conjugate (32) derived from lla-hydroxyprogesterone.144... 

M. Catala-Icardo, M. Misiewicz, A. Ciucu, J.V. Garcia-Mateo, J.M. Calatayud, FI-on line photochemical reaction for direct chemiluminescence determination of photo-degradated chloramphenicol, Talanta 60 (2003) 405. 

B21. Bronstein, I., and Voyta, J. C., Application of a novel direct chemiluminescence substrate for alkaline phosphatase in the detection of herpes simplex I virus. Proc. San Diego Conf. Mol. Probes, 3rd, p. 18 (1988). 

De Boever, J., Kohen, F., Leyseele, D., and Vandekerckhove, D., Isoluminol-based direct chemiluminescence immunoassay for steroid hormones. In Luminescence Immunoassay and Molecular Applications (K. Van Dyke and R. Van Dyke, eds.), pp. 119-139. CRC Press, Boca Raton, FL, 1990. 

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