Analyte Recovery of Volatile Organic Compounds: A Passive Sampling Analysis via Photothermal Desorption Compatible Diffusive Samplers

TL;DR

Researchers tested a new method called photothermal desorption to recover volatile organic compounds from air samples, showing promising results for future industrial use.

Contribution

The study introduces a novel preanalytical technique, photothermal desorption, for improving VOC recovery in passive sampling.

Findings

PTD achieved recovery rates of 0.60% for toluene, 1.2% for n-hexane, 1.1% for trichloroethylene, and 14.0% for isopropyl alcohol per pulse.

Buckypaper sorbents showed adsorption capacities of 152 mg/g for toluene and 105 mg/g for isopropyl alcohol.

Variability in recovery is attributed to intermolecular forces and sorbent nonuniformity.

Abstract

Volatile organic compounds (VOCs) are common sources
of occupational
exposure throughout a variety of industries. To protect personnel
from overexposure, field industrial hygienists must conduct compliance
sampling. In efforts to improve upon analytical sensitivity and time-to-knowledge
of existing VOC exposure assessment methods, the industrial hygiene
research group at UAB has developed a preanalytical technique known
as photothermal desorption (PTD), which uses pulses of high-energy
light to desorb analytes from thermally conductive, carbonaceous sorbents.
To-date, the theoretical and conceptual groundwork for PTD have been
laid, and advances have been made toward a first-generation, PTD-compatible
diffusive sampler. However, additional characterizations of the prototype
sampler’s performance are needed before the method is ready
for in-field deployment. As such, the objectives of this study were
2-fold: (1) the primary objective was to determine the percent mass
recovered via PTD of samples collected for various VOC analytes (i.e.,
toluene, n-hexane, isopropyl alcohol, and trichloroethylene),
and (2) the secondary objective was to quantify the analyte adsorption
capacities of buckypaper (BP) sorbents for each VOC of interest. The
percent mass recovery of toluene, n-hexane, trichloroethylene,
and isopropyl alcohol were found to be 0.60 ± 0.09, 1.2 ±
0.09, 1.1 ± 0.1, and 14.0 ± 1.0% per PTD pulse, and analyte
adsorption capacities for BP sorbents were determined to be 152 ±
5 mg/g at 219 ppm toluene, 75 ± 42 mg/g at 292 ppm n-hexane, 104 ± 37 mg/g at 101 ppm trichloroethylene, and 105
± 19 mg/g at 413 ppm isopropyl alcohol. The observed differences
in desorption of analytes are likely attributed to varying types of
weak intermolecular forces acting on aromatic rings, aliphatic chains,
and polar moieties. While the large standard deviations in adsorption
capacities may be explained by nonuniformity of nanotube alignment
in respective sorbents. The early stage, prototype characterization
data presented in this study, demonstrates the promising nature of
PTD used with passive air samplers and provides a solid foundation
for future development of the preanalytical technique and accompanying
sampling devices.

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