TY - JOUR
T1 - Optimization of compound-specific chlorine stable isotope analysis of chloroform using the Taguchi design of experiments
AU - Asfaw, Berhane Abrha
AU - Sakaguchi-Söder, Kaori
AU - Bernstein, Anat
AU - Siebner, Hagar
AU - Schüth, Christoph
N1 - Funding Information:
This research was funded by the BMBF-MOST German-Israeli Water Technology cooperation (grant WT-1401. BMBF project funding reference number: 02WIL1386. MOST funding number: WT1401). The authors express their sincere thanks to the laboratory technicians at the Institute of Applied Geosciences (IAG), particularly Dr Thomas Schiedek and Dip.-Ing. Claudia Cosma, for their unconditional support. They would also like to thank the journal editor and two anonymous reviewers for their valuable comments that helped to improve the manuscript. Open access funding enabled and organized by Projekt DEAL.
Funding Information:
This research was funded by the BMBF‐MOST German‐Israeli Water Technology cooperation (grant WT‐1401. BMBF project funding reference number: 02WIL1386. MOST funding number: WT1401). The authors express their sincere thanks to the laboratory technicians at the Institute of Applied Geosciences (IAG), particularly Dr Thomas Schiedek and Dip.‐Ing. Claudia Cosma, for their unconditional support. They would also like to thank the journal editor and two anonymous reviewers for their valuable comments that helped to improve the manuscript. Open access funding enabled and organized by Projekt DEAL.
Publisher Copyright:
© 2020 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd
PY - 2020/12/15
Y1 - 2020/12/15
N2 - Rationale: Chloroform, a probable human carcinogen, is commonly detected in various concentration levels in many surface water and groundwater sources. Compound-specific chlorine stable isotope analysis (Cl-CSIA) is significant in investigating the fate of chlorinated contaminants in the environment. Analytical conditions should, however, be thoroughly examined for any isotopic fractionation. In this study, we simultaneously optimize three analytical parameters for a robust online Cl-CSIA of chloroform using the Taguchi design of experiments. Methods: For Cl-CSIA, a purge-and-trap autosampler coupled to a gas chromatograph in tandem with a quadrupole mass spectrometer, with electron ionization in selected ion monitoring (SIM) mode, was used. Using the Taguchi method, the dominant parameter affecting the results of Cl-CSIA for chloroform was identified through concurrent investigation of the signal-to-noise ratios (S/N) of three parameters, each at three levels: purging time (5, 10, 15 min), transfer time (80, 120, 160 s), and dwell time (20, 60, 100 ms). Moreover, the optimum combination of the levels was identified. Results: The purging time, with a maximum S/N, resulted in the highest influence on the isotope ratios determined. It was further refined through additional experiments to sufficiently extract chloroform from the aqueous phase. Accordingly, 8 min of purging time, 120 s transfer time and 100 ms dwell time were the optimum conditions for Cl-CSIA of chloroform. Post-optimization, a precision of ±0.28 ‰ was achieved for 8.4 nmol of chloroform (equivalent to 0.89 μg or approx. 25 nmol Cl-mass on column). Conclusions: A simple online method for Cl-CSIA of chloroform was optimized with the Taguchi design of experiments. The Taguchi method was very useful for the optimization of the analytical conditions. However, the purging conditions should be fine-tuned and selected so that sufficient extraction of a target compound is confirmed to acquire a stable and higher precision of the method.
AB - Rationale: Chloroform, a probable human carcinogen, is commonly detected in various concentration levels in many surface water and groundwater sources. Compound-specific chlorine stable isotope analysis (Cl-CSIA) is significant in investigating the fate of chlorinated contaminants in the environment. Analytical conditions should, however, be thoroughly examined for any isotopic fractionation. In this study, we simultaneously optimize three analytical parameters for a robust online Cl-CSIA of chloroform using the Taguchi design of experiments. Methods: For Cl-CSIA, a purge-and-trap autosampler coupled to a gas chromatograph in tandem with a quadrupole mass spectrometer, with electron ionization in selected ion monitoring (SIM) mode, was used. Using the Taguchi method, the dominant parameter affecting the results of Cl-CSIA for chloroform was identified through concurrent investigation of the signal-to-noise ratios (S/N) of three parameters, each at three levels: purging time (5, 10, 15 min), transfer time (80, 120, 160 s), and dwell time (20, 60, 100 ms). Moreover, the optimum combination of the levels was identified. Results: The purging time, with a maximum S/N, resulted in the highest influence on the isotope ratios determined. It was further refined through additional experiments to sufficiently extract chloroform from the aqueous phase. Accordingly, 8 min of purging time, 120 s transfer time and 100 ms dwell time were the optimum conditions for Cl-CSIA of chloroform. Post-optimization, a precision of ±0.28 ‰ was achieved for 8.4 nmol of chloroform (equivalent to 0.89 μg or approx. 25 nmol Cl-mass on column). Conclusions: A simple online method for Cl-CSIA of chloroform was optimized with the Taguchi design of experiments. The Taguchi method was very useful for the optimization of the analytical conditions. However, the purging conditions should be fine-tuned and selected so that sufficient extraction of a target compound is confirmed to acquire a stable and higher precision of the method.
UR - http://www.scopus.com/inward/record.url?scp=85095597416&partnerID=8YFLogxK
U2 - 10.1002/rcm.8922
DO - 10.1002/rcm.8922
M3 - Article
C2 - 32770575
AN - SCOPUS:85095597416
SN - 0951-4198
VL - 34
JO - Rapid Communications in Mass Spectrometry
JF - Rapid Communications in Mass Spectrometry
IS - 23
M1 - e8922
ER -