ABSTRACT
Thyroid disease is the second most endocrinopathy during pregnancy 1. Thyroid dysfunction affects 2-3â% of pregnant women 2. Early diagnosis and initiation of therapy are important due to the potential complications in both mother and fetus. This article provides an overview of current recommendations regarding thyroid diagnostics and constellations during pregnancy that require therapy.
Subject(s)
Pregnancy Complications , Thyroid Diseases , Female , Humans , Pregnancy , Mothers , Pregnancy Complications/diagnosis , Pregnancy Complications/therapy , Thyroid Diseases/diagnosis , Thyroid Diseases/therapyABSTRACT
The carcinogenic compound N-nitrososarcosine (NSAR) is found in foods and tobacco products, and its quantification is of great interest. Although the presence of two stereoisomers, E- and Z-NSAR, is well-known, individual investigation of the isomers has not been reported so far. The present study by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) reveals that (i) the mass spectrometric responses of the isomers differ by a factor of approximately two and (ii) the isomer ratio is unstable in freshly prepared standard solutions. As a consequence, NSAR concentrations determined by LC-ESI-MS/MS are biased if those facts are not taken into account. The method described here overcomes the difficulty of stereospecific response by adjusting the isomer ratio and was applied to 100 tobacco products and fully validated for moist and dry snuff reference materials showing expanded measurement uncertainties of ~20% and limits of quantification of ~20 ng/g.
ABSTRACT
The mass spectrometric behavior of four pairs of stereoisomers was investigated by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). The E- and Z-isomers of the pesticides chlorfenvinphos, dimethomorph, mevinphos and phosphamidon-each with one double bond-were chosen for this study. The MS response of the individual isomers was investigated by infusing the isomers individually into the MS or after the separation of isomer mixtures via high-performance liquid chromatography (HPLC). In the case of dimethomorph, the same MS response was found for the two isomers. In contrast to that, the individual isomers of chlorfenvinphos, mevinphos and phosphamidon showed different MS response both in the single ion monitoring (SIM) mode in single quadrupole MS and multiple reaction monitoring (MRM) mode in tandem MS. The MS response of the isomers partly depends on (1) the declustering potential of the precursor ion in the SIM mode, (2) the selected transition and (3) the collision energy in the MRM mode. Consequently, quantification by summation of the peak areas of the isomers is inaccurate due to over- or underestimating of one of the stereoisomers. Accurate quantitative results can only be achieved when the compound-specific MS parameters are separately determined for each isomer. This can be done by using pure isomers or by the determination of the MS parameters after HPLC separation and the measurement of the actual isomer ratio with an independent technique.
ABSTRACT
A method was developed for the quantitative determination of alachlor, benalaxyl, clomazone, diflubenzuron, dimethomorph, diphenamid, ethofumesate, metalaxyl, methoprene, metobromuron and piperonyl butoxide on tobacco. The pesticides were extracted with water and methanol from five different types of tobacco. The extracts were purified by partition on an extraction cartridge containing diatomaceous earth. The purified extracts were analysed by reversed-phase high-performance liquid chromatography connected to an atmospheric pressure ionisation-electrospray-triple quadrupole mass spectrometer operating in the positive ion mode. Two different transitions and their relative intensities were monitored for unambiguous identification. All pesticides presented overall recovery rates between 35% and 110%. The trueness is near 100% and the interday precision is below 15%. The limits of quantifications are equal or below the guidance residue levels proposed by the Agrochemical Advisory Committee of CORESTA, an association of organisations having scientific research relative to tobacco.
