This experiment observed the evolution of metabolite plumes from a human trapped in a simulation of a collapsed building. Ten participants took it in turns over five days to lie in a simulation of a collapsed building and eight of them completed the 6 h protocol while their breath, sweat and skin metabolites were passed through a simulation of a collapsed glass-clad reinforced-concrete building. Safety, welfare and environmental parameters were monitored continuously, and active adsorbent sampling for thermal desorption GC-MS, on-line and embedded CO, CO(2) and O(2) monitoring, aspirating ion mobility spectrometry with integrated semiconductor gas sensors, direct injection GC-ion mobility spectrometry, active sampling thermal desorption GC-differential mobility spectrometry and a prototype remote early detection system for survivor location were used to monitor the evolution of the metabolite plumes that were generated. Oxygen levels within the void simulator were allowed to fall no lower than 19.1% (v). Concurrent levels of carbon dioxide built up to an average level of 1.6% (v) in the breathing zone of the participants. Temperature, humidity, carbon dioxide levels and the physiological measurements were consistent with a reproducible methodology that enabled the metabolite plumes to be sampled and characterized from the different parts of the experiment. Welfare and safety data were satisfactory with pulse rates, blood pressures and oxygenation, all within levels consistent with healthy adults. Up to 12 in-test welfare assessments per participant and a six-week follow-up Stanford Acute Stress Response Questionnaire indicated that the researchers and participants did not experience any adverse effects from their involvement in the study. Preliminary observations confirmed that CO(2), NH(3) and acetone were effective markers for trapped humans, although interactions with water absorbed in building debris needed further study. An unexpected observation from the NH(3) channel was the suppression of NH(3) during those periods when the participants slept, and this will be the subject of further study, as will be the detailed analysis of the casualty detection data obtained from the seven instruments used.
Miniaturized ultra high field asymmetric waveform ion mobility spectrometry (ultra-FAIMS) combined with mass spectrometry (MS) has been applied to the analysis of standard and tryptic peptides, derived from α-1-acid glycoprotein, using electrospray and nanoelectrospray ion sources. Singly and multiply charged peptide ions were separated in the gas phase using ultra-FAIMS and detected by ion trap and time-of-flight MS. The small compensation voltage (CV) window for the transmission of singly charged ions demonstrates the ability of ultra-FAIMS-MS to generate pseudo-peptide mass fingerprints that may be used to simplify spectra and identify proteins by database searching. Multiply charged ions required a higher CV for transmission, and ions with different amino acid sequences may be separated on the basis of their differential ion mobility. A partial separation of conformers was also observed for the doubly charged ion of bradykinin. Selection on the basis of charge state and differential mobility prior to tandem mass spectrometry facilitates peptide and protein identification by allowing precursor ions to be identified with greater selectivity, thus reducing spectral complexity and enhancing MS detection.
A direct, ambient ionization method
has been developed for the
determination of creatinine in urine that combines derivatization
and thermal desorption with extractive electrospray ionization and
ion mobility-mass spectrometry. The volatility of creatinine was enhanced
by a rapid on-probe aqueous acylation reaction, using a custom-made
thermal desorption probe, allowing thermal desorption and ionization
of the monoacylated derivative. The monoacyl creatinine [M + H]+ ion (m/z 156) was subjected
to mass-to-charge selection and collision induced dissociation to
remove the acyl group, generating the protonated creatinine [M + H]+ product ion at m/z 114
before an ion mobility separation was applied to reduce chemical noise.
Stable isotope dilution using creatinine-d3 as internal standard was used for quantitative measurements. The
direct on-probe derivatization allows high sample throughput with
a typical cycle time of 1 min per sample. The method shows good linearity
(R2 = 0.986) and repeatability (%RSD 8–10%)
in the range of 0.25–2.0 mg/mL. The creatinine concentrations
in diluted urine samples from a healthy individual were determined
to contain a mean concentration of 1.44 mg/mL creatinine with a precision
(%RSD) of 9.9%. The reactive ambient ionization approach demonstrated
here has potential for the determination of involatile analytes in
urine and other biofluids.
A direct, ambient ionization method
has been developed using atmospheric
pressure thermal desorption–extractive electrospray–mass
spectrometry (AP/TD-EESI-MS) for the detection of the genotoxic impurity
(GTI) methyl p-toluenesulfonate (MTS) in a surrogate
pharmaceutical matrix. A custom-made thermal desorption probe was
used to the desorb and vaporize MTS from the solid state, by rapid
heating to 200 °C then cooling to ambient temperature, with a
cycle time of 6 min. The detection of MTS using EESI with a sodium
acetate doped solvent to generate the [MTS+Na]+ adduct
ion provided a significant sensitivity enhancement relative to the
[M+H]+ ion generated using a 0.1% formic acid solvent modifier.
The MTS detection limit is over an order of magnitude below the long-term
daily threshold of toxicological concern (TTC) of 1.5 μg/g and
the potential for quantitative analysis has been determined using
starch as a surrogate active pharmaceutical ingredient (API).
The direct extraction of urinary analytes deposited on reversed-phase thin-layer chromatography (RP-TLC) plates is demonstrated using a solvent gradient extraction procedure without prior chromatographic development. The surface sample probe TLC-MS interface used for the gradient extraction is compared to direct loop injection into the electrospray ion source for biofluid profiling. The gradient elution is shown to enhance ion intensities, as urinary salts are eluted in aqueous formic acid in the early part of the gradient reducing ion suppression. The retention of urinary components on the C18 RP-TLC plate was confirmed by monitoring analyte responses with, and without, an aqueous wash phase prior to the solvent gradient extraction. The use of gradient elution allows fractionation of the complex biological matrix as a result of differential retention of urine components on the undeveloped RP-TLC plate. The direct gradient analysis of TLC plates has also been combined with ion mobility-mass spectrometry to further resolve the complex urinary profile and identify co-eluting compounds.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.