title: Development of a candidate certified reference material of cypermethrin in green tea.
abstract: This paper presents the preparation of a candidate certified reference material (CRM) of cypermethrin in green tea, GLHK-11-01a according to the requirements of ISO Guide 34 and 35. Certification of the material was performed using a newly developed isotope dilution mass spectrometry (IDMS) approach, with gas chromatography high resolution mass spectrometry (GC-HRMS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). Statistical analysis (one-way ANOVA) showed excellent agreement of the analytical data sets generated from the two mass spectrometric detections. The characterization methods have also been satisfactorily applied in an Asia-Pacific Metrology Program (APMP) interlaboratory comparison study. Both the GC-HRIDMS and GC-IDMS/MS methods proved to be sufficiently reliable and accurate for certification purpose. The certified value of cypermethrin in dry mass fraction was 148 μg kg(-1) and the associated expanded uncertainty was 14μg kg(-1). The uncertainty budget was evaluated from sample in homogeneity, long-term and short-term stability and variability in the characterization procedure. GLHK-11-01a is primarily developed to support the local and wider testing community on need basis in quality assurance work and in seeking accreditation.
authors.affiliation: Analytical and Advisory Services Division, Government Laboratory, Homantin Government Offices, Hong Kong, China.
authors.forename: Della W M
authors.initials: DW
authors.lastname: Sin
authors.forename: Pui-kwan
authors.initials: PK
authors.lastname: Chan
authors.forename: Samuel T C
authors.initials: ST
authors.lastname: Cheung
authors.forename: Yee-Lok
authors.initials: YL
authors.lastname: Wong
authors.forename: Siu-kay
authors.initials: SK
authors.lastname: Wong
authors.forename: Chuen-shing
authors.initials: CS
authors.lastname: Mok
authors.forename: Yiu-chung
authors.initials: YC
authors.lastname: Wong