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  • 1. Elliott, John F.
    et al.
    Ramzy, Ahmed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Moffat, Wayne
    Suzuki, Kunimasa
    Severe intractable eyelid dermatitis probably caused by exposure to hydroperoxides of linalool in a heavily fragranced shampoo2017In: Contact Dermatitis, ISSN 0105-1873, E-ISSN 1600-0536, Vol. 76, no 2, p. 114-115Article in journal (Other academic)
  • 2.
    Gamal Ramzi, Ahmed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Analytical methodologies for common skin allergens: Organic thioureas, isothiocyanates and fragrance hydroperoxides in everyday life products2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes analytical methodologies for the determination of important skin-sensitizing chemicals in two types of commercial items: chloroprene rubber and fragrance products which are both well-known to be associated with contact allergy.

    Chloroprene rubber (neoprene) is widely used in different applications and products, such as bags, gloves, wetsuits, braces, mouse pads et c. Exposure to chloroprene rubber materials has resulted in numerous cases of allergic contact dermatitis. Organic thioureas have been considered the main culprits, even though they at the same time have been classified as weak or non-sensitizers in the murine local lymph node assay (LLNA). Previous findings indicate that a possible reason for sensitization is that organic thioureas are being metabolized in the skin into more reactive electrophiles, such as isothiocyanates and isocyanates, after skin exposure. In this thesis, chemical analyses of a number of chloroprene products from the European open market showed the presence of diethylthiourea in all analyzed items, while other organic thioureas could not be detected. The levels of diethylthiourea varied, with the highest at 158 µg cm-2 in a used back support that had previously caused allergic contact dermatitis in a patient. Furthermore, it was discovered that all the examined items emitted ethyl isothiocyanate. LLNA showed that ethyl isothiocyanate is a strong skin sensitizer, as has been shown earlier for other tested isothiocyanates. Isothiocyanates were shown to be thermally formed from diethyl, diphenyl and dibutylthiourea at a temperature as low as 35 °C, i. e. around skin temperature. Altogether, the results from these experiments, patch tests and chemical analyses revealed that isothiocyanates are important haptens in contact allergy to chloroprene rubber.

    Fragrances constitute one of the main causes of contact allergy, next to nickel and preservatives. The most widespread fragrances in cosmetics and perfumes on the market are monoterpenes, such as linalool and limonene, which at air exposure easily oxidize to hydroperoxides, which are strongly skin sensitizing compounds and the main haptens. Despite this, there is so far no EU regulation concerning fragrance hydroperoxides in products, which may be due to lack of analytical methods which can reliably measure them in fragrances. Presented in this thesis is a toolbox of different analytical methods, applied on essential oils, shampoo, patch test preparations and different types of perfumes. Furthermore, one of our studies elucidated the first case (to my knowledge) of allergic contact dermatitis as being correlated to a product that contains a fragrance hydroperoxide.

    Taken together, the thesis shows the importance of developing analytical methods for the identification, measurement and detection of important haptens in contact allergy. 

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  • 3.
    Ramzi, Ahmed
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ahmadi, Hamid
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    A two-dimensional non-comprehensive reversed/normal phase high-performance liquid chromatography/tandem mass spectrometry system for determination of limonene and linalool hydroperoxides2018In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1566, p. 102-110Article in journal (Refereed)
    Abstract [en]

    A two-dimensional non-comprehensive high-performance liquid chromatographic (HPLC) system coupled to electrospray ionization tandem mass spectrometry was developed for the determination of skin allergenic hydroperoxides of limonene and linalool. These compounds are some major components behind skin sensitization and contact (skin) allergy to fragrances.

    Fragrance hydroperoxides usually occur in complex compositions, often as constituents of the natural essential oils added to a large number of commercial products. Their similarities to interfering compounds, many with identical elemental composition, make the determination difficult even when using selective detection methods like mass spectrometry. In this work, a first-dimension chromatographic heart-cut isolation of the hydroperoxides on a reversed-phase HPLC system was combined with a second-dimension normal-phase HPLC system for separation of the hydroperoxides. The intersystem transfer was made by trapping the heart-cut fraction on a short graphitized carbon column, exchanging the mobile phase and back-flushing the hydroperoxides into the second dimension.

    Each analysis was performed within 60 min without any pretreatment, except dilution, prior to injection. The obtained instrumental limits of detection (LODs) at a signal-to-noise ratio of 3 were lower than 1.2 ng injected on column and method LODs were below 0.3 ppm. An after-shave product was shown to contain the highest concentrations of the measured hydroperoxides, with 445 ± 23 ppm of total linalool hydroperoxides. This level is likely able to elicit skin reactions in already sensitized individuals.

  • 4.
    Ramzy, Ahmad G.
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Hagvall, Lina
    Pei, Mansoureh N.
    Samuelsson, Kristin
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Investigation of diethylthiourea and ethyl isothiocyanate as potent skin allergens in chloroprene rubber2015In: Contact Dermatitis, ISSN 0105-1873, E-ISSN 1600-0536, Vol. 72, no 3, p. 139-146Article in journal (Refereed)
    Abstract [en]

    Background

    Exposure to chloroprene rubber has resulted in numerous cases of allergic contact dermatitis, attributed to organic thiourea compounds used as vulcanization accelerators. However, thiourea compounds are not considered to be strong haptens.

    Objectives

    To analyse common commercial chloroprene materials for their contents of diethylthiourea (DETU), dibutylthiourea (DBTU), diphenylthiourea (DPTU), and their degradation products, isothiocyanates; and to investigate the sensitization potencies of possible degradation products of the mentioned thiourea compounds.

    Methods

    Liquid chromatography/mass spectrometry (MS) was used for quantification of organic thiourea compounds in chloroprene products, such as medical, sports and diving gear; isothiocyanates were measured by solid-phase microextraction/gas chromatography/MS. Sensitization potencies were determined with the murine local lymph node assay (LLNA).

    Results

    DETU was identified at concentrations of 2.7-9.4 mu g/cm(2) in all samples, whereas neither DBTU nor DPTU was detected. At 37 degrees C, degradation of DETU in the materials to ethyl isothiocyanate (EITC) was detected. EITC and ethyl isocyanate showed extreme and strong sensitization potencies, respectively, in the LLNA.

    Conclusions

    DETU can act as a prehapten, being degraded to EITC when subjected to body temperature upon skin contact. EITC could thus be the culprit behind allergic contact dermatitis caused by chloroprene rubber.

  • 5.
    Ramzy, Ahmad G.
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Lammintausta, K.
    Matura, M.
    Bråred Christensson, J.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hagvall, L.
    Isothiocyanates are important as haptens in contact allergy to chloroprene rubber2017In: British Journal of Dermatology, ISSN 0007-0963, E-ISSN 1365-2133, Vol. 177, no 2, p. 522-530Article in journal (Refereed)
    Abstract [en]

    Background Contact allergy to chloroprene rubber products is well known. Thiourea compounds are considered the cause of allergy. Diethylthiourea commonly occurs in this type of product and can decompose to the sensitizer ethyl isothiocyanate. Objectives To investigate the clinical importance of degradation products and metabolites from organic thioureas in contact allergy to chloroprene rubber with a focus on isothiocyanates and isocyanates. Methods Patients with contact allergy to diphenylthiourea were patch tested with phenyl isothiocyanate and phenyl isocyanate. Patients with known contact allergy to diethylthiourea were retested with diethylthiourea, while chemical analyses of their chloroprene rubber products were performed. The stability of diethylthiourea, diphenylthiourea and dibutylthiourea in patch-test preparations was investigated. Liquid chromatography/mass spectrometry and solid-phase microextraction/gas chromatography were used for determination of organic thioureas and isothiocyanates. Results All patients allergic to diphenylthiourea reacted to phenyl isothiocyanate, two of eight reacted to phenyl isocyanate and six of eight reacted to diphenylthiourea. Four patients allergic to diethylthiourea reacted at retest; diethylthiourea was detected in all chloroprene rubber samples, with levels of 2-1200 nmol cm(-2). At 35 degrees C, ethyl isothiocyanate was emitted from all samples. Patch-test preparations of diethylthiourea, diphenylthiourea and dibutylthiourea all emitted the corresponding isothiocyanate, with diethylthiourea showing the highest rate of isothiocyanate emission. Conclusions Thiourea compounds are degraded to isothiocyanates, which are generally strong or extreme sensitizers, thus acting as prehaptens. This process occurs in both chloroprene rubber products and patch-test preparations. Positive reactions to phenyl isocyanate indicate cutaneous metabolism, as the only known source of exposure to phenyl isocyanate is through bioactivation of diphenylthiourea.

  • 6.
    Ramzy, Ahmed
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Ahmadi, Hamid
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    A two-dimensional reversed and normal phase high-performance liquid chromatography/tandem mass spectrometry system for determination of linalool and limonene hydroperoxidesManuscript (preprint) (Other academic)
  • 7. Rudbäck, Johanna
    et al.
    Ramzy, Ahmed
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Ann-Therese
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of allergenic hydroperoxides in essential oils using gas chromatography with electron ionization mass spectrometry2014In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 37, no 8, p. 982-989Article in journal (Refereed)
    Abstract [en]

    Fragrance monoterpenes are widely used commercially due to their pleasant scent. In previous studies, we have shown that air-exposed monoterpenes form hydroperoxides that are strong skin sensitizers. Methods for detection and quantification of the hydroperoxides in essential oils and scented products are thus desirable. Due to thermolability and low UV absorbance, this is a complicated task. We have recently developed a sensitive LC-ESI-MS method, but with limited structural information and separation efficiency for positional isomers and stereoisomers. In the present study, we investigated derivatization with a trimethyl silyl reagent and subsequent GC with electron ionization MS for the determination of monoterpene hydroperoxides. All investigated monoterpene hydroperoxides could be chromatographed as thermostable trimethyl silyl derivatives and yielded the fragment m/z 89 ([OSi(CH3)(3)](+)) at a higher extent compared to corresponding alcohols. Limonene-2-hydroperoxide and four other hydroperoxide isomers of limonene were separated and detected in sweet orange oil autoxidized for two months. The concentration of limonene-2-hydroperoxide isomers was found to be 19 g/mg in total. Also isomers of linalyl acetate hydroperoxide and linalool hydroperoxide were detected in autoxidized petitgrain oil (two months). The presented GC-MS method showed concentrations in the same order as previous LC-MS/MS analysis of the same type of oils.

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