Luminescent analysis

Luminescent analysis - a set of methods of analysis based on the observation of luminescence. For excitation of luminescence (see) investigated object is exposed to ultraviolet light (mercury-quartz lamp). Observation of a luminescence is produced in a dark room visually or with the help of special instruments (fluorometric).
Quality fluorescent analysis based on the difference of color luminescence produced by the substances of different chemical nature; quantitative fluorescent analysis - on measuring the intensity of luminescence by fluorimetric or by registration of luminescence spectra special spectrograph. Luminescent analysis is widely used for determination of vitamins, hormones, antibiotics, carcinogenic substances, drugs, etc. in different materials, including biological objects (blood, urine, tissues and others).
Luminescent analysis in health. In hygienic practice luminescent analysis has spread in assessing the quality of food products (the presence of impurities, spoilage of products). Depending on fresh meat, fish and other food products there are many different shades and intensity of fluorescent glow. For the analysis it is possible to use water extract of the products (minced sample is mixed with a diet with water in the relation 1 : 10 and shaken). Hoods placed in fluorometer that allows you to measure the intensity of luminescence. For example, the intensity of the luminescence of the extract of fresh meat (fresh or chilled) is so low, that is not measured in the unit. In extracts of meat, relatively good, the intensity of the luminescence is much higher and varies between 18 to 30 conventional units. The readings over 30 characterize meat as stale. When determining the freshness of fish and fish products fluorescent quantitative methods of analysis allow to fix the initial stage of product spoilage.
Proposed fluorescent detection method the proteins in the milk with which without the cost of reagents, you can analyze for 3-5 minutes (instead of 8-12 hours by the method of celdas). The method is based on measurement of the integral intensity of the glow of tryptophan milk proteins, divorced ten times the water, when excited by ultraviolet light (wavelength of 250 - 290 MMK). To determine water quality can also be used luminescent analysis. The luminescent glow of the waters caused contained organic substances, and aquatic organisms, cells of algae and the remnants of aquatic plants. For pure water water lines and artesian wells characterized by poorly-violet luminescence. The water in the Moscow and Leningrad water fluorescent very weak; distilled water practically does not light. Samples of waters with blue and bluish tint glow typical for waters with various degree of pollution. Water with high color glow yellow-green. Wastewater food industry have bright blue, purple, blue, red) light. The glow of humic compounds masks the luminescence of organic compounds, which are contained in the water with pollution.
Quantitative fluorescent analysis based on the dependence that exists between the intensity of luminescence and concentration lyuminestsiruyushchikh substances. At low concentrations of the substances in solution, the intensity of luminescence proportional to its content. At high concentrations lyuminestsiruyushchikh substances of this proportionality is broken. The technique of quantitative fluorescent analysis is to empirically determine the relationship between the concentration of the analyte and the intensity of the fluorescent glow. Pre-install the same dependence for a series of standard solutions with known number of analyte. According to the data obtained when measuring a series of standard solutions using calibration schedule, according to which the intensity of fluorescent radiation of the analyzed solution define him as the concentration of a substance. In some methods of quantitative fluorescent analysis are not predetermined calibration schedule, as defined in the course of analysis of the intensity of the luminescence of a standard solution.
Luminescent analysis can be used to determine the carcinogenic substances, uranium in various objects of the environment, insecticides and oil products in the water of open reservoirs and other Cm. also fluorescence microscopy.

Luminescent analysis - a set of methods of analysis based on the phenomenon of luminescence (see).
The advantage of the method of fluorescent analysis is very high sensitivity. So, the colouring fluorescein can be found in his glow in the concentration in the solution of about 10-8 mol/l, and by the absorption of light on the spectrophotometer - only at concentrations of 10-5-10-6 mol/L. In a wide range of concentrations not exceeding maximum at which absorption) solution of exciting light, and the reabsorption of fluorescent glow become significant, the intensity of the luminescence of a substance is proportional to its concentration. Therefore, by measuring the intensity of the luminescence of a solution of known concentration of a substance can then easily identify the concentration of this substance in the solutions under consideration. Advantages of the method of luminescent analysis of the impact is even greater when working with multi-component media, if it's fluorescent only defined the substance or at least have a region of the spectrum (it can be identified using optical filters), in which it primarily's fluorescent. To this end, apply the photovoltaic fluorimeters.
For excitation of luminescence of substances that absorb in the UV part of the spectrum, the use of mercury-quartz, hydrogen and deuterium lamps, emitting significant part of luminous power in this part of the spectrum. For excitation of substances that absorb visible waves, optical incandescent bulbs with compact, "point" spirals. The allocation of the full light output radiation of a given spectral plot, well absorbed investigated connection (and a little absorbed other lyuminestsiruyushchikh substances, if available, is achieved by using different optical filters. Most selective interference filters that can skip the strip just 10 MMK. Unknown connections is determined by the removal of luminescence spectra using spectrofluorimeter.

A significant number of unpainted organic compounds characterized by the absorption in the ultraviolet part of the spectrum (for example, proteins, amino acids, nucleic acids, carbohydrates and their metabolites), give wide, malobalykskoe band luminescence in the range close (ultraviolet, purple and blue) wavelengths; their identification by the spectra of luminescence is often difficult. In these cases the investigated material freeze up-100A (sometimes freezing can be replaced by suspendirovanie in oil); this luminescence spectra are narrowing and find specific thin structure.
Spectra of luminescence sensitively react sometimes to minor changes in state of matter (aggregation, change of redox potential, changes molecules associated with a change in pH changes in the secondary structure, and others). With this change, and other characteristics of compounds. So, when aggregating chlorophyll is shifting its luminescent glow in the direction of long waves, and the yield of luminescence and its duration are falling in several times. Pyridinylmethyl in the transition from the restored state in oxidized generally ceases luminesce. Fluorescence flavins highly dependent on pH of the medium, etc.
In addition to the direct methods of fluorescent analysis, there are several indirect. For example, normally not fluorescent blood gets this property adding to it sulfuric acid. Oxygen is known as an effective cositel luminescence of many compounds; this phenomenon is used as the indicator on the oxygen content.
Are developed and special methods of fluorescent analysis. For example, from insects fireflies produce the enzyme luciferase, which may, in the presence of ATP oxidize luciferin with chemiluminescent emission of light. The intensity of the latter when taken in excess luciferin-luciferase system is proportional to the concentration of ATP in the test suspension. At colouring of nucleic acid dyes proflavanol series fluorescent characteristics of the latest vary with changes in the structure of biopolymer. Methods of luminescent analysis of recently used in the study of compounds belonging to classes of purines, porphyrins (especially chlorophyll, vitamins, steroid hormones, amino acids, proteins, and various drugs. In addition, luminescent analysis used in fluorescent paper chromatography, when fluoropropiophenone, the titration and in fluorescent microscopy (see).