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W Gottardi

Publications and source records attributed to W Gottardi.

34 records · Page 2Linked to original sources
PubMed1992

[Aqueous chloramine T solutions as disinfectants: chemical composition, reactivity and toxicity].

In aqueous solutions of Chloramine T (CAT), caused by dissociation, hydrolysis and disproportionation processes, seven different kinds of molecules emerge (HOCl, OCl-, R-NCl-, R-NHCl, R-NCl2, R-NH2, and R-NH- [R = CH3-C6H4-SO2]). Their equilibrium concentrations have been calculated using an iteration process (polynom of 4th degree) as a function of cCAT (0.003-10%) and pH (0-14): The (absol.) concentration of "free chlorine" ([HOCl] + [OCl-]) is surprisingly low showing a maximum concentration of HOCl in the whole concentration and pH range of only 2 . 10(-7) moles/l (0.014 ppm). The relative equilibrium concentrations of the N-chlorinated toluene sulfonamide species R-NCl-, R-NHCl, and R-NCl2, virtually alone responsible for the oxidizing and by this also disinfecting properties, owing to the extremely low concentration of free chlorine, are influenced in the concentration range relevant for practice (greater than 0.1%) only by the pH-value: At pH greater than 7 the whole oxidation capacity is present as R-NCl- (pH 7: 99.6%; pH 8: 99.96%), while at pH less than 3 it is formed by R-NHCl and R-NCl2.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloramines↗
PubMed1991

[Chlorine coatings on skin surfaces. II. Parameters influencing the coating strength].

Although active chlorine compounds have been used for more than 140 years (Semmelweis, 1848) as a skin disinfectant the phenomenon of the "chlorine covers" not earlier than 1988 has been described for the first time (Hyg. + Med. 13 (1988) 157). It deals with a chemical alteration of the uppermost skin layer which comes apparent in an oxydizing action against aqueous iodide. Its origin is chlorine covalently bound in the form of N-Cl functions to the protein matrix of the horny skin. Since the chlorine covers exhibit a persistant disinfecting activity which might be important for practice, the factors influencing their strength have been established. The most important are: the kind of the chlorine system, the concentration (oxydation capacity), pH, temperature and the volume of the used solution, the time of action, the application technique and the state of the skin. Variations of the latter can be observed at different skin areas of one and the same person as well as at the same areas of different persons, and result in differences of the cover strength up to 100%. The stability on dry skin is very good, showing a decomposition rate of approximately 1.2% per hour. However on skin surfaces moistened by sweat (e.g. hands covered by surgeons gloves) the chlorine cover is disingrated much more faster (decomposition rate: 40-50% per hour). Washing with soap as well as the action of alcohols cause virtually no decrease in the cover strength, while wetting by solutions of reducing agents (e.g. thiosulfate, cysteine, iodide) provokes a fast decomposition suitable for removing the chlorine covers.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohols↗
PubMed1990

[Chlorine covers on skin surfaces. I. Determination of the covering strength with the DPD cuvette method].

A new photometric micro method for the quantitative determination of "chlorine covers" on skin surfaces is presented. It is based on the formation of the dye emerging from the reaction of the bound chlorine with iodide and diethyl-p-phenylene diamine (DPD). In contrast to the already described "glove-method" (Hyg. + Med. 13 (1988) 157) it can be applied to all regions of the body and enables a valuation of the specific chlorine cover (micrograms Cl2/cm2). Further features of the method are a small demand of time and work, and--on grounds of the high sensitivity--only a small measuring area (approximately 1.5 cm2) which allows repeated measurements for improving the statistical safety. However, since the different skin areas take up variable amounts of chlorine this can be done only at limited areas. Founded upon a comprehensive error analysis a precision (calculated variation coefficient) of +/- 3-4% for flat and +/- 8-9% for curved (finger tips) skin areas with not too small chlorine covers (greater than 0.3 microgram Cl2/cm2) has been evaluated. Failing a reference method resp. standard areas with known chlorine covers the accuracy of the method could not exactly be ascertained. Owing to an estimation of the most important systematic errors the method might yield results slightly to low (deviation from the true value: approximately -5 to -10%). In spite of this restriction the DPD-cuvette-method is a very useful analytical procedure and the chlorine cover measured herewith and expressed as microgram Cl2/cm2 represents a new skin related parameter, which not only allows an estimation of persistent bactericidal effects on skin surfaces, but also might be useful as an indicator for the roughness of the skin.

Chlorine↗
PubMed1986

[Germicidal experiments with aqueous PVP-iodine-containing disinfecting solutions: effect of the content of free iodine on the bactericidal action against Staphylococcus aureus].

The bactericidal activity against Staph. aureus of three PVP-iodine preparations in different concentrations, and of 0.1 mol/L KI-solutions with concentrations of free iodine corresponding to the povidone-iodine preparations, was evaluated at reaction times of 7, 15, 30 and 60 seconds. The concentration of free iodine has been measured potentiometrically during the entire reaction time. In all cases it has been confirmed that the bactericidal activity is increasing with the concentration of free iodine. However, there have been found differing correlations between the logarithmic decrease of germs (RF-value), the concentration of free iodine and the reaction time (statistical evaluation of the results by means of linear multiple regression: RF = a0 + a1 log [I2] + a2 log t). Referring to the concentration of free iodine the bactericidal activity in the range of RF approximately equal to 4-6 is increasing as follows: Povidone-iodine washing concentrate much greater than iodine in KI (0.1 mol/l) greater than Povidone-iodine mucosal disinfectant greater than aqueous solution of povidone iodine. This sequence is explained by differences of composition. So it is assumed that the surface active ingredients facilitate the penetration of molecular iodine. The observed correlations show that there is probably no exact mathematical relation of general validity for iodine preparations of different composition between the concentration of free iodine and the RF-value. However, for one and the same preparation such a correlation can be derived and enables to make predictions about the bactericidal activity, which can be expected as a consequence of the concentration of free iodine.

Disinfectants↗
PubMed1981

[The formation of iodate as a reason for the decrease of efficiency of iodine containing disinfectants (author's transl)].

Methods are given to calculate the iodate equilibrium concentrations in aqueous solutions of iodine, containing additional iodide as well as the reaction times concerning the transformation of iodine to iodate. Using the results, which have been obtained evaluating in this manner solutions of triiodide (CI2 = CI- = 10(-6)--10(-1) M/l) as well as 0.03 M iodine solutions containing varying amounts of iodide (0--0.12 M/l) the following conclusions concerning the stability of iodine containing disinfecting agents can be made; 1. Below pH 6 a decrease of the disinfecting effectiveness owing to the formation of iodate can be excluded. 2. Above pH 7 the formation of iodate, whose extent depends extremely on the pH-value as well as the iodide concentration, has to be regarded very carefully. Raising the pH-value lowers the stability (iodate formation increases) while raising the iodide concentration improves the stability (iodate formation is reduced). 3. Because of the stabilizing effect of the iodide ion, provided that its concentration is high enough, the opposite effect of the pH-value can be overcompensated and as a result of this iodine containing agents can exhibit a stability sufficient for practice also in the weak alkaline range (pH less than 9).

Chemical Phenomena↗
PubMed1980

[Redoxpotential and germicidal action of aqueous halogen solution (author transl)].

Methods are given to calculate the equilibrium concentrations of both halogene solutions (chlorine, bromine and iodine) in the presence of additional halide and of chlorine solutions in the presence of chloride and ammonia. With the aid of these values and the redoxpotentials which have been determined from them is demonstrated that there is a very complicated connection between the latters and the total as well as the equilibrium concentrations. It depends on the kind of the halogene, the pH-value and the presence of substances which can react with the halogene (halides, NH-compounds) and can not be described by the simple formula: increase of the redoxpotential approximately increase of the equilibrium concentrations of germicidal hydrolysis products and as a consequence of the death rates. On the contrary a reduction of the total halogene concentration may cause an increase of the redoxpotential as well as the addition of halide may lower the redoxpotential while the concentration of strong germicidal "free halogene" remains unchanged. The redoxpotential therefore is not a mean to make reliable predictions concerning the germicidal action of halogene solutions.

Bromine↗
PubMed1979

[On the sporocidal action of dibromoisocyanuric acid (author's transl)].

Using the suspension test the action of dibromoisocyanuric acid (DBI) and--for the purpose of a comparison--elemental chlorine and Chloramine-T on three different spore strains at pH 7.0 and room temperature has been investigated. DBI proved to be a desinfecting agent by which at a concentration of 0.01 M positive halogene (= 1.45 g DBI/I) in 15--60 minutes (depending on the spore strain) a reliable kill can be achieved. Although using elemental chlorine shorter kill rates have been obtained (Chloramine-T was without any effect) DBI shows some advantages which also suggest its use in practice. As possible reasons for the differing efficiency of the three investigated substances the equilibrium concentrations of the hydrolysis products (HOCl resp. HOBr) and diffusion effects are discussed.

Bacillus↗
PubMed1978

[Aqueous iodine solutions as disinfectants: composition, stability, comparison with chlorine and bromine solution (author's transl)].

The equilibrium concentrations of aqueous iodine solutions in dependence of the total concentration and the pH-value have been calculated with and without regard of the iodate formation. The values obtained by the latter methode enabled by application of the known rate law to calculate the initial rate of the iodate formation and to draw from this conclusions concerning the stability of iodine solutions. On the grounds of these calculations to aqueous iodine solutions in the concentration and pH-range which is relevant for disinfection (greater than 10(-5) M/l, pH 6--9) one can attribute a stability sufficient for the use in practice and - unlike chlorine and bromine solutions - a content of bactericidal "free halogene" which is higher and independent of the pH-value. The disinfecting action of the iodine cation (H2O+J) which is supposed to be very powerful can be neglected because of its low concentration (10(-3)--10(-6%) of the total concentration). Hypoiodic acid which has already been converted into iodate by disproportionation is as good as lost for the disinfection because of the extremely slow reverse reaction.

Bromine↗
PubMed1978

[On the usability of N-iodo compounds as disinfectants (author's transl)].

The usability of N-iodo compounds for disinfecting purposes has been investigated with the help of the equilibrium concentrations in aqueous solution, which have been calculated both with and without regard of the iodate formation, and the rate of iodate formation, which has been deduced from the latter. The following conclusions can be drawn: Fresh and diluted aqueous solutions of N-iodo compounds exhibit HOJ-concentrations corresponding with the sum HOJ + J2 ( = "free halogene") in pure iodine solutions, which let expect a similar bactericidal behaviour of this class of compounds. Compared with iodine solutions, however, a higher rate of iodate formation and therefore a less stability of these solutions can be established, which is caused by the throughout higher HOJ-concentration. Observing certain conditions (pH less than 7; C less than 10(-5) M/l) and unless a not to long interacting time is required the stability should be sufficient for disinfecting purposes. Of particular interest is the possibility to investigate, virtually in absence of molecular iodine, the bactericidal action of the HOJ. A common use in practice will depend on the costs, which, as far as the purchasable N-iodo-succinimide is concerned, are very high, hence it should not come at present into consideration as an alternative of the much more inexpensive elemental iodine.

Disinfectants↗
PubMed1978

[The identification of mineral oil pollutions by the combination of IR-and fluorescence spectroscopy (author's transl)].

By evaluation of the quotient Q = intensity of fluorescence: intensity of C-H-vibration a relative number has been obtained, which, independend of concentration and largely substance specific, enables to make more exact statements on identifying oil spills than those derived only from IR-spectroscopic measurement. The Q-values of 33 different mineral oil products have been calculated and are compared with the intensity ratio V of the asymetric CH2- and CH2-stretching bands and the absorbtivity of these bands, which commonly are used. Q, exhibiting values from 0,0015 to greater than 5000 has proved to be a very sensitive number while the maximum ratio of the V resp. absorptivity values was only 1:13. The scope of Q is discussed on the basic of three examples.

Infrared Rays↗
PubMed1977

[Aqueous chloride and bromine solutions as disinfectants: composition, redox potential, differences of reactivity (author's transl)].

A method is given to calculate the equilibrium concentrations of the molecules and ions emerging from the hydrolysis and dissociation of chlorine and bromine in aqueous soltuion. The differing influence the pH value and the initial (total) halogene concentration exerts to the HOX- and X2-equilibrium concentration is discussed. From the calculated equilibrium concentrations and tabulated standard reduction potentials the redox potentials of chlorine and bromine solutions at various pH values are calculated. No correlation between the reactivity and the redox potential of the two halogens was observed. Two possible explanations for the differing reactivity of chlorine and bromine against proteins are presented.

Bromine↗
PubMed1976

[Concerning the question of the bactericidal action of organic N-bromoamines: experiments with N,N-dibromo-tert.-butylamine (author's transl)].

For the first time a defined N-fromoamine was examined on its bactericidal behaviour. In accordance with the "Richtlinien für die Prüfung chemischer Desinfektionsmittel" (3. Aufl. Stuttgart: Gustav Fischer Verlag 1972), the action of the substance (1,5 X 10(-3) - 1,5 X 10(-5) M aqueous solution) on the germs E. coli, Proteus vulgaris, Ps. aeruginosa und Staph. aureus SG 511 was tested. As can be seen in Tab. 1, N,N-Dibromo-tert.-butylamine (1,5 X 10(-3) and 1,5 X 10(-4) M/I is showing a bactericidal action on all tested germs.

Bacteria↗
PubMed1976

[On the bactericidal action of dibromoisocyanuric acid; experiments concerning the disinfection of hands (author's transl)].

The action of dibromoisocyanuric acid (DBI), C12, Br2, trichloroisocyanuric acid (TCI) and chloramine T against Staph. aureus SG 511 was compared. Using the suspension test DBI and Br2 showed the strongest, chloramine T however, the weakest bactericidal power (Tab 2). Under the conditions of the "Hygienic disinfection of hands" a 0.005 M solution of DBI met the requirements specified in the "Richtlinien für die Prüfung chemischer Desinfektionsmittel" (3. Ed., Stuttgart: Gustav Fischer Verlag, 1972), and was comparable to a chloramine T solution containing the same amount of active halogen (Tab. 3). The decrease of disinfection power compared with the suspension test can be attributed to a great error induced by protein.

Bromine↗
PubMed1976

[On the reaction of chlorine, bromine, iodine and some N-chloro and N-bromo compounds with peptone in aqueous solution (author's transl)].

The course of the reaction cited in the heading was investigated by determination of the decrease of iodometrically ascertainable oxidation capacity (pH = 7,00; initial concentration: 5 X 10(-3) M active Halogen/1, 0,5 g peptone/1). From the curves depicted in fig. 1 the following scale of reactivity can be derived: dibromoisocyanuric acid greater than bromine greater than 1,3-dibromo-5,5-dimethylhydantoin greater than N-bromo-N'-chloro-dimethylhydantoin greater than clorine greater than trichloroisocyanuric acid greater than 1,3-dichloro-5,5-dimethylhydantoin greater than iodine greater than chloramine T. The reactivity differences tentatively are explained by electronic, kinetic resp. thermodynamic effects.

Bromine↗