Ulrich Pinkernell

Eawag: Das Wasserforschungs-Institut des ETH-Bereichs, Duebendorf, Zurich, Switzerland

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Publications (13)60.73 Total impact

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    ABSTRACT: Inactivation of B. subtilis spores with ozone was investigated to assess the effect of pH and temperature, to compare the kinetics to those for the inactivation of C. parvum oocysts, to investigate bromate formation under 2-log inactivation conditions, and to assess the need for bromate control strategies. The rate of B. subtilis inactivation with ozone was independent of pH, decreased with temperature (activation energy of 42,100 Jmol(-1)), and was consistent with the CT concept. B. subtilis was found to be a good indicator for C. parvum at 20-30 degrees C, but at lower temperatures B. subtilis was inactivated more readily than C. parvum. Bromate formation increased as both pH and temperature increased. For water with an initial bromide concentration of 33 microgl(-1), achieving 2-logs of inactivation, without exceeding the 100 microg l(-1) bromate standard, was most difficult at 30 degrees C for B. subtilis and at midrange temperatures (10-20 degrees C) for C. partum. pH depression and ammonia addition were found to reduce bromate formation without affecting B. subtilis inactivation, and may be necessary for waters containing more than 50 microgl(-1) bromide.
    Water Research 09/2001; 35(12):2950-60. DOI:10.1016/S0043-1354(00)00577-7 · 5.53 Impact Factor
  • Ulrich Pinkernell · Urs von Gunten ·
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    ABSTRACT: Bromate formation during ozonation of bromide-containing natural waters is somewhat inversely connected to the ozone characteristics: an initial fast increase followed by a slower formation rate. During the initial phase mostly OH radical reactions contribute to bromate formation,whereas in the secondary phase both ozone and OH radicals are important. To minimize bromate formation several control options are presented: ammonia addition, pH depression, OH radical scavenging, and scavenging or reduction of hypobromous acid (HOBr) by organic compounds. Only the two first options are applicable in drinking watertreatment. By both methods a similar effect of a bromate reduction of approximately 50% can be achieved. However, bromate formation during the initial phase of the ozonation cannot be influenced by either method. Ammonia (NH3) efficiently scavenges HOBrto NH2Br. However, this reaction is reversible which leads to higher required NH3 concentrations than expected. The rate constant kNH2Br for the hydrolysis of NH2Br by OH- to NH3 and OBr- was found to be 7.5-10(6) M(-1) s(-1). pH depression shifts the HOBr/ OBr- equilibrium to HOBr and also affects the ozone chemistry. The effect on ozone chemistry was found to be more importantfor bromate formation. For a given ozone exposure, the OH radical exposure decreases with decreasing pH. Therefore, for pH depression the overall oxidation capacity for a certain ozone exposure decreases which in turn leads to a smaller bromate formation.
    Environmental Science and Technology 07/2001; 35(12):2525-31. DOI:10.1021/es001502f · 5.33 Impact Factor
  • Source
    Ulrich Pinkernell · Bernd Nowack · Hervé Gallard · Urs von Gunten ·
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    ABSTRACT: New methods for the determination of reactive bromine and chlorine species are presented. Hypobromous acid (HOBr) and all three bromamines species (NH2Br, NHBr2, NBr3) are analyzed as a sum parameter and hypochlorous acid (HOCl), monochloramine (NH2Cl) and chlorine dioxide (ClO2) can be determined selectively. However, no distinction is possible between HOCl and the active bromine species. The bromine and chlorine species react with ABTS (2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid-diammonium salt) to a green colored product that is measured at 405 or 728 nm. Free chlorine and NH2Cl can be measured in the presence of ozone. The method is therefore suitable if combinations of disinfectants are used, such as chlorine/chlorine dioxide or chlorine/ozone. In natural waters, the method provides a detection limit for all chlorine/bromine species of less than 0.1 μM. The colored reaction product is very stable and allows a fixation of the chlorine/bromine species in the field and subsequent determination of the absorption in the laboratory.
    Water Research 12/2000; 34(18-34):4343-4350. DOI:10.1016/S0043-1354(00)00216-5 · 5.53 Impact Factor
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    U Von Gunten · U Pinkernell ·
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    ABSTRACT: The occurrence of Cryptosporidium in raw waters and bromate formation during ozonation of bromide-containing waters leads to a difficult optimisation of ozonation processes. On the one hand inactivation of Cryptosporidium requires high ozone exposures, on the other hand under these conditions bromate formation is favored. In order to overcome this problem we need information about (i) the oxidant concentrations (ozone and OH radicals) during an ozonation process, (ii) kinetics of the inactivation of Cryptosporidium, (iii) kinetics and mechanism of bromate formation, and (iv) the reactor hydraulics. The strong temperature dependence of the inactivation of Cryptosporidium which results in a higher ozone exposure (time-integrated action of ozone) at low temperatures makes it more difficult to fulfil disinfection and bromate standards at low temperatures. Under these conditions control options for bromate formation can be applied. Depression of pH and addition of ammonia have been selected to be the best options. For a given ozone exposure both measures lead to a reduction of bromate formation in the order of 50%.
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    Diedrich Harms · Ulrich Pinkernell · Uwe Karst · Roberto Than · Michael Schmidt · Bernt Krebs ·
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    ABSTRACT: A selective method for the determination of hydrogen peroxide in the presence of other oxidants is presented. The formation of a coloured adduct in the reaction of a dinuclear iron( iii) complex with hydrogen peroxide is used for the quantification of the peroxide. The reaction product is detected at wavelengths between 570 and 600 nm. The major advantage of the method is the immediate reaction. Other peroxides exhibit little interfence, typically contributing to an error of 0.1% for the same concentration. The method was optimized for the determination of hydrogen peroxide in household products using microplate spectrophotometry. The limit of detection is 3 mmol l21 (100 ppb) under these conditions. Calibration functions are linear over the range 9-300mmol l21 (300 ppb-10 ppm). The method was compared with established methods for peroxide analysis, including the spectrophotometric titanyl method and an HPLC method based on the oxidation of triphenylphosphine. The method described is suitable for the analysis of real samples.
    The Analyst 11/1998; 123(11):2323-2327. DOI:10.1039/a806432f · 4.11 Impact Factor
  • S. Effkemann · U. Pinkernell · R. Neumüller · F. Schwan · H. Engelhardt · U. Karst ·
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    ABSTRACT: The first liquid chromatographic method with postcolumn derivatization for the simultaneous determination of peroxycarboxylic acids is described. Aliphatic peracids with chain lengths from C2 to C12 are separated by HPLC on a reversed-phase C18 column with acetonitrile/water gradient elution. For improved peak shape, tetrahydrofuran and acetic acid are added to the aqueous eluent. After chromatographic separation, the peroxycarboxylic acids react with 2,2‘-azino-bis(3-ethylbenzothiazoline)-6-sulfonate, a popular substrate for the enzyme peroxidase. Iodide traces are added as catalyst. The oxidation product, a green radical cation, is determined using a UV/visible detector in four characteristic regions of the visible and near-infrared spectrum in the range 405−815 nm. The advantages of the new method are detection limits in the low micromolar range, negligible matrix interferences, high reproducibility, and the possibility for simultaneous determination of several peroxycarboxylic acids.
    Analytical Chemistry 08/1998; 70(18). DOI:10.1021/ac980256b · 5.64 Impact Factor
  • Stefan Effkemann · Ulrich Pinkernell · Uwe Karst ·
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    ABSTRACT: Liquid chromatographic (LC) studies have been conducted to investigate the formation and decomposition of peroxyacetic acid (PAA) and hydrogen peroxide in laundry detergents: Both, methyl-p-tolylsulfide (MTS) and methyl-phenylsulfoxide (MPSO) are suitable reagents for the selective LC determination of peroxycarboxylic acids in the presence of a large excess of hydrogen peroxide. MTS is oxidized in acidic media to the corresponding sulfoxide (MTSO) and MPSO is oxidized in alkaline media to methyl-phenylsulfone (MPSO2). In both cases, triphenyl phosphine (TPP) can be used for the subsequent determination of hydrogen peroxide using LC. TPP is oxidized to the corresponding phosphine oxide (TPPO). The formation and the decomposition of PAA and hydrogen peroxide in laundry detergents with time have been observed using both methods. Acidification prior to analysis and subsequent application of MTS and TPP for the simultaneous determination of PAA and hydrogen peroxide in alkaline samples has been identified to be best suited as means for preservation of the original sample composition.
    Analytica Chimica Acta 05/1998; 363(1):97-103. DOI:10.1016/S0003-2670(98)00040-3 · 4.51 Impact Factor
  • Ulrich Pinkernell · Stefan Effkemann · Uwe Karst ·
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    ABSTRACT: The first instrumental method for simultaneous determination of peroxyacetic acid (PAA) and hydrogen peroxide has been developed. The successive quantitative reaction of PAA with methyl p-tolyl sulfide (MTS) and hydrogen peroxide with triphenylphosphine (TPP) yields the corresponding sulfoxide MTSO and phosphine oxide TPPO. The reagents and their oxides are separated by HPLC on reversed-phase columns with acetonitrile/water gradient elution within 5 min. External calibration with the solid standards of MTSO and TPPO leads to a very accurate and reliable method. Samples are stable and can be stored after derivatization for several days prior to analysis. Real samples from brewery disinfection were analyzed in comparison to titration with excellent correlation.
    Analytical Chemistry 09/1997; 69(17):3623-7. DOI:10.1021/ac9701750 · 5.64 Impact Factor
  • Ulrich Pinkernell · Hans-Joachim Lüke · Uwe Karst ·
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    ABSTRACT: A method for determining peroxycarboxylic acids, as exemplified by peroxyacetic acid (I) determination, is described. A sample (20 µl) was mixed with 3.5 ml 1M-acetic acid/100 mg/l KI/1 mg/ml 2,2'-azino-bis-(3-ethylbenzothiazoline)-6-sulfonate (4:1:2) and the solution was diluted to 10 ml with H2O. After 10 min, the absorbance was measured at 405 nm. The calibration graph was linear from 0.19-7.6 mg/l I and the detection limit was 76 µg/l. The method was applied to disinfection solutions. The results obtained agreed with those obtained by HPLC. Microplates were used for the analysis of large numbers of samples.
    The Analyst 06/1997; 122(6):567-571. DOI:10.1039/A700509A · 4.11 Impact Factor
  • Burkhard Eulering · Michael Schmidt · Ulrich Pinkernell · Uwe Karst · Bernt Krebs ·

    Angewandte Chemie International Edition 09/1996; 35(17). DOI:10.1002/anie.199619731 · 11.26 Impact Factor
  • Burkhard Eulering · Michael Schmidt · Ulrich Pinkernell · Uwe Karst · Bernt Krebs ·

    Angewandte Chemie 09/1996; 108(17):2102-2104. DOI:10.1002/ange.19961081726
  • Eulering B · Schmidt M · Pinkernell U · Karst U · Krebs B ·

    Journal of Inorganic Biochemistry 07/1995; 59(2):403-403. DOI:10.1016/0162-0134(95)97501-G · 3.44 Impact Factor
  • Source
    U. Pinkernell · U. Karst · K. Cammann ·
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    ABSTRACT: A new method for the determination of peroxyacetic acid (PAA) in aqueous solutions is described. Methyl p-tolylsulfide (MTS) is oxidized by PAA, forming the corresponding methyl p-tolylsulfoxide sulfoxide (MTSO), which can be separated easily by high-performance liquid chromatography on a reversed-phase column and detected by ultraviolet spectroscopy at a wavelength of 230 nm. MTSO is a commercially available solid substance which can be used as an external standard for calibration. Therefore, calibration with the unstable PAA can be avoided. This method is characterized by a high reproducibility, low detection limits at 4 x 10(-7) mol/L (30 mu g/L), an applicable concentration range of more than two decades, and negligible cross reactivity toward hydrogen peroxide.
    Analytical Chemistry 08/1994; 66(15). DOI:10.1021/ac00087a028 · 5.64 Impact Factor