{'fraction_non_alphanumeric': 0.030415125359638306, 'fraction_numerical': 0.02260583641594739, 'mean_word_length': 5.193384223918575, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Measurement of human levels of Dechlorane 602 by CZC-NCI-HRTOFMS

Dechlorane (Dec) 602 is part of the norbornene derivatives flame retardants family that has quite recently been reported in the environment 1 . Because very little is known about their potential bioaccumulation in human, we developed a GC-MS method for the measurement of 602, 603, 604 and Chlordene Plus (CP) in human serum. The particularity of the 600 family molecules is to exhibit a bicycle [2,2,1]-heptene halogenated structure. During mass spectrometric analysis, they can undergo retro Diels-Alder reactions and typically form hexachlorocyclopentadiene (HCCPD) fragments (m/z = 272). The quantification of those analytes is most of the time carried out on the most abundant ions of this fragment cluster (e.g m/z 271.8102/273.8072 for Dec 602) 2 . In the present report, we further investigated the use of a cryogenic zone compression negative chemical ionization high resolution time-of-flight mass spectrometry (CZC-NCI-HRTOFMS) method previously developed 3 to provide sensitivity and specificity for the target dechlorane compounds, presently focusing on Dec 602. One of the feature of this approach is that the molecular ion cluster is heavily present and the HCCPD cluster that is used for quantification in EI is barely present in NCI, although its dechlorinated product (pentachlorocyclopentadiene – PCCPD – C5Cl5) is present in high abundance and therefore both clusters can be used for selective quantification 3 . In addition of using CZC to enhance the instrumental detection limits (iDLs), two different GC phases were combined to reduce the risk of chromatographic co-elutions usually present in the complex blood matrix. Furthermore, the HRTOFMS instrument was equipped with a specific low thermal emission filament, coated with Yttria, that allowed to reproducibly perform in NCI mode at ion source temperatures as low as 140°C. The use of such reduced temperature was ideal to minimize dissociative electron capture (DEC) and enhance resonance electron capture (REC) to favor high MS signal for the parent ion cluster. This is important for isotope dilution (ID) (once 13 C labels will be available) accurate quantification, but also for enhanced specificity in the identification of the target molecule, and possibly untargeted emerging analogs. The use of full-scan HRTOFMS additionally allows performing elemental composition calculations.