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Water preparation and other industrial processes employ polymer flocculants, derivatives of quaternary ammonium salts, e.g., polydiallyldimethylammonium chloride (PC). The toxicity of PC requires the control of its residual concentration in tap water. As demonstrated in review [1], the problem of the rapid and reliable determination of polymer flocculants in waters is yet to be solved. A spectrophotometric procedure based on the interaction of PC with one of triphenylmethane dyes (TPM), namely, eosine is commonly used for this purpose. Previously the stoichiometry of the interaction of eosine with PC was determined and the conditions of the formation of the colored product (ion pair) were optimized [2,3]. Unfortunately, even under optimum conditions, the sensitivity of the reaction with eosine is insufficient for the determination of PC at a level of the maximum permissible concentration (MPC). Systematic studies of the interaction of other TPM with polymer flocculants could lead to the development of more sensitive procedures for the determination of polymer flocculants, with was the aim of this work.For the study, we selected the following TPM: Pyrocatechol Violet (PCV), Bromophenol Blue (BPB), Bromocresol Green (BCG), Bromothymol Blue (BTB), Phenol Red (PR), Thymol Blue (TB), aluminon (AL), Bromocresol Purple (BCP), Xylenol Orange (XO), fluoresceine (FL), fluorexon (FLX), erythrosine (ER), Bengal Red (BR), and eosine (EO). The reagents were selected for the following reasons: The above reagents are well studied, are used as indicators, and are available in the pure form. Their dissolution in water ( <10 − 3 M) yields true solutions stable on storage and intensely absorbing in the visible spectral region (log ε = 3.5-5.0). All of the reagents have functional groups of the donor character and are potential ligands. Anionic forms of TPM interact with cationic forms of monomeric quaternary ammonium salts yielding ion pairs [4]; hence, changes in absorption spectra are observed. It is expected that TPM will analogously react with polymer quaternary ammonium salts, e.g., with PC. However, the formation of ion pairs of polymer flocculants with dyes must have its specific features, which should be taken into account in the course of analysis. EXPERIMENTALStock 1 × 10 -3 M solutions of dyes were prepared by dissolving weighed portions of chemically pure reagents. Stock solutions of PC (25 mg/L) were prepared in the day of use from a weighed portion of the VPK-402 flocculant (TU 6-05-2009-86; AO Kaustik, Sterlitamak, Russia) containing 39.66% PC and inert impurities. Conventional buffer solutions were used to adjust pH 4-10, and 2 M HCl was added to adjust pH < 4. The absorption spectra of mixtures of TPM and PC were recorded in the range 380-650 nm with a step of 10 nm on SF-26 and KFK-3 spectrophotometers in glass cells (3.0 cm) with reference to a blank solution with the same concentration of TPM and the same pH. PC alone does not absorb in the visible spectral region. All experiments were performed at 20-22°ë withou...

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EinfluS einer Erwarmung verschiedener Eiweille auf ihre Spaltbarkeit durch proteolytische EnzymeAn 7 verschiedenen EiweiDprriparaten und Gemischen von ihnen wird ihre Spaltbarkeit bei aufeinanderfolgender Einwirkung von Pepsin und Pankreatin vor und nach der Erwarmung (30 min auf 95 "C; Abkiihlung auf 37 "C) untersucht. Die Ergebnisse zeigen: Nach der Empfindlichkeit gegen Erwlrmung werden die untersuchten Eiweik in zwei Gruppen unterteilt: In der ersten Gruppe von E i w e i h mit hohem Gehalt an Cystein Eillt deren Spaltbarkeit nach der Erwtirmung ab; in der zweiten Gruppe sind die Eiweik mi1 niedrigem Gehalt an Cystein und solche EiweiDe enthalten, die unter denaturierenden Bedingungen gewonnen worden waren. Diese Eiweik sind gegen Erwhung unemptindlich.Der Grad c'er EiweiDhydrolyse durch Pankreatin ist kaum abhangig von der Art des Ausgangseiweiks.

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