title: Applications of Hadamard transform-gas chromatography/mass spectrometry for the detection of hexamethyldisiloxane in a wafer cleanroom.
abstract: The Hadamard transform-gas chromatography/mass spectrometry (HT-GC/MS) technique was successfully employed for the detection of hexamethyldisiloxane (HMDSO, C(6)H(18)OSi(2)) at the sub-nL/L level in a semiconductor wafer cleanroom. Indoor air samples were collected from the room, according to EPA Method TO-17 using a Tedlar bag where the air samples were allowed to pass through an absorption tube for 24 h. The condensed components were then heated and simultaneously injected into a GC column through a Hadamard-injector, which was operated in accordance with the Hadamard codes. Compared to the single injection used in most GC/MS systems, the signal-to-noise (S/N) ratios were substantially improved after the inverse Hadamard transformation of the encoded chromatogram. Under optimized conditions, when cyclic S-matrix orders of 255, 1023 and 2047 were used, the S/N ratios of the HMDSO signals were substantially improved by 7.4-, 15.1- and 20.1-fold, respectively. These improvements are in good agreement with theoretically calculated values (8.0-, 16.0- and 22.6-fold, respectively). We found that when the HT-GC/MS technique was applied, HMDSO could be detected at the 0.1 nL/L level.
authors.affiliation: Department of Chemistry, National Taiwan Normal University, 88 Sec. 4, Tingchow Road, Taipei, Taiwan.
authors.forename: Yuan-Kai
authors.initials: YK
authors.lastname: Cheng
authors.forename: Cheng-Huang
authors.initials: CH
authors.lastname: Lin
authors.forename: Samuel
authors.initials: S
authors.lastname: Kuo
authors.forename: Jonathan
authors.initials: J
authors.lastname: Yang
authors.forename: Szu-Yuan
authors.initials: SY
authors.lastname: Hsiung
authors.forename: Jia-Lin
authors.initials: JL
authors.lastname: Wang
mesh_terms: D000388:Air / Q000032:analysis*; D000465:Algorithms; D004780:Environment, Controlled; D004784:Environmental Monitoring / Q000379:methods; D005583:Fourier Analysis; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D012833:Siloxanes / Q000032:analysis*
chemical_list: D012833:Siloxanes; C015917:hexamethyldisiloxane