Title: The sensitivity of benzene cluster cation chemical ionization mass spectrometry to select biogenic terpenes

Abstract

Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and α-pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, α-pinene, β-pinene, D-limonene, ocimene, β-myrcene, farnesene, α-humulene, β-caryophyllene, and isolongifolene at atmospherically relevant mixing ratios (<100 pptv). In addition, we determine the dependence of CI-ToFMS sensitivity on the reagent ion neutral delivery concentration and water vapor concentration. We show that isoprene is primarily detected as an adduct (C₅H₈∙C₆H₆⁺) with a sensitivity ranging between 4 and 10 ncps ppt^-1, which depends strongly on the reagent ion precursor concentration, de-clustering voltages, and specific humidity (SH). Monoterpenes are detected primarily as the molecular ion (C₁₀H₁₆⁺) with an average sensitivity, across the five measured compounds, of 14 ± 3 ncps ppt^-1 for SH between 7 and 14 g kg^-1, typical of the boreal forest during summer. Sesquiterpenes are detected primarily as the molecular ion (C₁₅H₂₄⁺) with an average sensitivity, across the four measured compounds, of 9.6more » ± 2.3 ncps ppt^-1, that is also independent of specific humidity. Comparable sensitivities across broad classes of terpenes (e.g., monoterpenes and sesquiterpenes), coupled to the limited dependence on specific humidity, suggest that benzene cluster cation CI-ToFMS is suitable for field studies of biosphere–atmosphere interactions.« less

Authors:

Lavi, Avi; Vermeuel, Michael P.; Novak, Gordon A.; Bertram, Timothy H.

Publication Date:

Thu Jun 07 00:00:00 EDT 2018

Research Org.:

Univ. of California, San Diego, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF)

OSTI Identifier:

1441037

Alternate Identifier(s):

OSTI ID: 1502930

Grant/Contract Number:  

SC0006431; AGS-1151430

Resource Type:

Published Article

Journal Name:

Atmospheric Measurement Techniques (Online)

Additional Journal Information:

Journal Name: Atmospheric Measurement Techniques (Online) Journal Volume: 11 Journal Issue: 6; Journal ID: ISSN 1867-8548

Publisher:

Copernicus Publications, EGU

Country of Publication:

Germany

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES