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Biomedical subjects

P Vardev

Publications and source records attributed to P Vardev.

5 recordsLinked to original sources
PubMed1993

[A rapid test for determining the content of residual monomer in polyvinyl chloride dust and granulate].

Rapid and cheap test is developed on the basis of colorimetric tubes "Hygitest", produced in Bulgaria, which could substitute, in a number of cases, the more expensive chromatographic procedure. The method of gas extraction of the examined material is used in the test, and as measuring instrument are used colorimetric tubes "Hygitest" type "Vinylchloride-1-A", which are supplied with reinforced filter for humidity and with special scale. A specially constructed flask is used for thermal desorption. The test has reproducibility and sensitivity significant for performing screening and routine control on the raw materials for production of packings from polyvinylchloride for nutrition purposes. The method "Vinyl-test" is standardized for control on the free monomer content in the packings for nutrition purposes with branch normal of the Ministry of Health and the State firm "Polychim" OH 02 77051-84 (Change No 1 of 8.07.1991).

Bulgaria↗
PubMed1993

[Diffusion indicator tubes for hydrogen chloride].

In order to define the mean shift exposure of workers in the environment of hydrogen chloride, we could use, besides long-term colorimetric tubes also colorimetric tubes on the principle of diffusion, named also passive monitors. Experiments are performed on different reactionary principles and recipes of indicator compositions for hydrogen chloride: with pH-indicators as bromphenol blau, dimethyl yellow and benzopurpurine 4B, and also reactions for discoloration of silver chromate or lead sulfate. The successful variants are metrologically evaluated by means of gas generating device for calibration gas mixtures. Special attention is given to the accuracy of the results at different air humidity. Recipes with minimum effect of the air humidity on the results are developed and is proved, that concentrations of hydrogen chloride could be significantly measured, also at higher humidity of the examined air of those given in the literature.

Air Pollutants, Occupational↗
PubMed1988

[Indicator tubes with a noncylindrical form for indicator packing].

A new type of system is made for determination of chemical pollutants in the air--indicator tubes with noncylindrical indicator filling--a subject of invention. The effect of the noncylindrical form on the metrological characteristics of the indicator tubes is studied. The noncylindrical filling is a way to influence these characteristics without changing the chemical receipt. There are a number of advantages: increasing more of 10x the sensitivity; linearization of the logarithmic characteristics of the indication dusts; possibility to lay two contrary scales on the conical indicator tubes for sucking respectively from the one or the other side of the asymmetric indicator filling, thus realising opportunities for defining of very low or very high accuracy. A new type of sampling system is established in practice. The dependences are given graphically.

Acetaldehyde↗
PubMed1983

[Current trends in improving the accuracy of indicator tubes].

The accuracy of the determinations made by the indicator tubes is constantly improved by the introduction of accurate dosage apparatuses for their calibration and due to the methods and criteria for the control of their quality. Modern dosage apparatuses for calibration were designed at RIHOD, reading the effect of air humidity and some other obstructive substances. A mathematical model was obtained, via a statistical way, of air humidity effect on the indices of some kinds indicator tubes for chlorine, hydrogen chloride, sulphur dioxide, etc. Correction coefficients were introduced reading air humidity effect, in this way guaranteeing the error of the determination not to exceed the allowable error, internationally accepted, of +/- 25%. In fact, the results obtained for the error were between 8 and 15% within the whole range of air relative humidities. With the accuracy attained some indicator tubes compete with the classical and apparatus methods for sanitary-chemical control of the air in the working environment.

Air Pollutants, Occupational↗