Evaluation and application of static headspace–multicapillary column-gas chromatography–ion mobility spectrometry for complex sample analysis

Abstract

An evaluation of static headspace-multicapillary column-gas chromatography-ion mobility spectrometry (SHS-MCC-GC-IMS) has been undertaken to assess its applicability for the determination of 32 volatile compounds (VCs). The key experimental variables of sample incubation time and temperature have been evaluated alongside the MCC-GC variables of column polarity, syringe temperature, injection temperature, injection volume, column temperature and carrier gas flow rate coupled with the IMS variables of temperature and drift gas flow rate. This evaluation resulted in six sets of experimental variables being required to separate the 32 VCs. The optimum experimental variables for SHS-MCC-GC-IMS, the retention time and drift time operating parameters were determined; to normalise the operating parameters, the relative drift time and normalised reduced ion mobility for each VC were determined. In addition, a full theoretical explanation is provided on the formation of the monomer, dimer and trimer of a VC. The optimum operating condition for each VC calibration data was obtained alongside limit of detection (LOD) and limit of quantitation (LOQ) values. Typical detection limits ranged from 0.1ng bis(methylthio)methane, ethylbutanoate and (E)-2-nonenal to 472ng isovaleric acid with correlation coefficient (R(2)) data ranging from 0.9793 (for the dimer of octanal) through to 0.9990 (for isobutyric acid). Finally, the developed protocols were applied to the analysis of malodour in sock samples. Initial work involved spiking an inert matrix and sock samples with appropriate concentrations of eight VCs. The average recovery from the inert matrix was 101±18% (n=8), while recoveries from the sock samples were lower, that is, 54±30% (n=8) for sock type 1 and 78±24% (n=6) for sock type 2. Finally, SHS-MCC-GC-IMS was applied to sock malodour in a field trial based on 11 volunteers (mixed gender) over a 3-week period. By applying the SHS-MCC-GC-IMS database, four VCs were identified and quantified: ammonia, dimethyl disulphide, dimethyl trisulphide and butyric acid. A link was identified between the presence of high ammonia and dimethyl disulphide concentrations and a high malodour odour grading, that is, ≥ 6. Statistical analysis did not find any correlation between the occurrence of dimethyl disulphide and participant gender.

Solid phase extraction to enhance sensitivity when headspace-gas chromatography-ion mobility spectrometer is used: determination of phenol in environmental samples

“…Higher RSD values were obtained for intensity peak height (RSD < 15%). This occurred due to the fact that the headspace experimental conditions chosen (70 C for 20 min) led to the volatilization of other compounds from the matrix, as was observed by other authors, 37 and this affects mainly the phenol intensity signal.…”

Analysis of Listeria using exogenous volatile organic compound metabolites and their detection by static headspace–multi-capillary column–gas chromatography–ion mobility spectrometry (SHS–MCC–GC–IMS)

“…The relative drift time ( t r drift) for each of the two VOCs was calculated using the following Eq. (1) [13]. …”

“…A static headspace–multi-capillary column–gas chromatography–ion mobility spectrometer (SHS–MCC–GC–IMS) manufactured by G.A.S.—Gesellschaft für Analytische Sensorsysteme mbH (Dortmund, Germany) was used [13]. The SHS–MCC–GC–IMS was fitted with an automatic sampler unit (CTC-PAL; CTC Analytics AG, Zwin-gen, Switzerland) and a heated gas-tight syringe.…”

“…Following injection of the SPME fibre, 1 mL of the previously equilibrated sample was transferred by pipette into a 20-mL sterile headspace vial (Sage Analytical Ltd., Heywood, UK) and capped with a sterile bimetallic crimp cap (Sage Analytical Ltd., Heywood, UK) prior to sampling and analysis by MCC–GC–IMS. The experimental procedure has previously been reported for analysis of VOCs associated with malodour in laundry [13]. …”

Static headspace‐multicapillary column with gas chromatography coupled to ion mobility spectrometry as a simple approach for the discrimination of crude and processed traditional Chinese medicines

“…Ion mobility spectrometry (IMS) is an analytical technology for separately detecting complex compounds in a mixture of analytes . Separation is based on the specific drift time that ionized compounds need to pass a fixed drift tube in a defined electric field . The volatile compounds of TCM often demand a second and independent separation step to individually analyze the multiple compounds at low concentrations.…”