Kinetics of Ion−Molecule Reactions with Dimethyl Methylphosphonate at 298 K for Chemical Ionization Mass Spectrometry Detection of GX

Distinct Subgroups of Patients With Lung Cancer Receiving Chemotherapy: A Latent Transition Analysis

Objectives

To identify subgroups of patients with lung cancer receiving chemotherapy based on the severity dimension of symptom experience, and to examine changes in membership between these subgroups over time.

Methods

Patients who were scheduled to receive chemotherapy completed the Chinese version of the MD Anderson Symptom Inventory and the revised lung cancer module with a total of 19 symptom items. Data were collected at three time points: two weeks before chemotherapy (T1), after chemotherapy cycle 1 (T2), and after chemotherapy cycle 3 or above (T3). The latent profile analysis and latent transition analysis were used to identify underlying subgroups and describe changes in subgroup membership over time.

Results

From the total sample (N = 195), 160 patients completed the symptom assessment at T1, T2, and T3. Two distinct latent symptom profiles of patients could be identified at T1, T2, and T3, which were classified as "Mild" and "Moderate-Severe" profiles. From T1 to T2 and T3, members in the Mild profile were more likely to move to the Moderate-Severe profile. Chemotherapy protocols, prior surgery treatment, and level of education can predict the transitions.

Conclusion

Results provide a better understanding of the patient's different symptom experiences and characteristics. These could help clinicians to anticipate symptom patterns and develop interventions in lung cancer patients who were scheduled to receive chemotherapy for the first time.

Interrogating Proton Affinities of Organophosphonate Species Via Atmospheric Flow Tube Mass Spectrometry and Computational Methods

Within trace vapor analysis in environmental monitoring, defense, and industry, atmospheric flow tube mass spectrometry (AFT-MS) can fill a role that incorporates non-contact vapor analysis with the selectivity and low detection limits of mass spectrometry. AFT-MS has been applied to quantitating certain explosives by selective clustering with nitrate and more recently applied to detecting tributyl phosphate and dimethyl methylphosphonate as protonated species. Developing AFT-MS methods for organophosphorus species is appealing, given that this class of compounds includes a range of pollutants, chemical warfare agent (CWA) simulants, and CWA degradation products. A key aspect of targeting organophosphorus analytes has included the use of dopant ion chemistry to form adducts that impart additional analytical selectivity. The assessment of potential dopant molecules suited to enhance detection of these compounds is hindered by few published ion thermochemical properties for organophosphorus species, such as proton affinity, which can be used for approximating proton-bound dimer bond strength. As a preliminary investigation for the progression of sensing methods involving AFT-MS, we have applied both the extended kinetic method and computational approaches to eight organophosphorus CWA simulants to determine their respective gas-phase proton affinities. Notable observed trends, supported by computational efforts, include an increase in proton affinity as the alkyl chain lengths on the phosphonates increased. Graphical Abstract .

Selective Reagent Ions for the Direct Vapor Detection of Organophosphorus Compounds Below Parts-per-Trillion Levels

Real-time low to sub parts-per-trillion (ppt_v) vapor detection of some organophosphorous compounds (OPCs) is demonstrated with an atmospheric flow tube-mass spectrometer. The chemical species investigated included dimethyl methylphosphonate, triethyl phosphate, and tributylphosphate. The atmospheric flow tube provides ambient chemical ionization with up to several seconds of ionization time. With sensitivities in the parts-per-quadrillion (ppq_v) range, there are many background contaminants competing for charge with the target analytes. Initially, the OPCs were not observable in direct room air analysis, presumably due to other trace components possessing higher proton affinities. However, the addition of a trialkylamine as a dopant chemical served to provide a single reagent ion that also formed a proton-bound heterodimer with the OPCs. These asymmetric proton-bound dimers had sufficiently high hydrogen bond energy to allow the cluster to remain intact during the analysis time of several seconds. Changes in stability were observed for some of these asymmetric proton-bound dimers with a shorter half-life for adducts with a larger proton affinity differences between the amine and the OPC. Detection levels approaching low ppt_v to high ppq_v were correlated by three different methods, including use of a permeation tube, direct injection of a fixed mass into the sample air flow, and calculations based upon signal intensity ratios, reaction time, and an estimated reaction rate constant. A practical demonstration showed real-time monitoring of a laboratory environment initially with low ppt_v levels of vapor observed to decay exponentially over about an hour while returning to baseline levels.

Chemical gradients on graphene to drive droplet motion

This work demonstrates the production of a well-controlled, chemical gradient on the surface of graphene. By inducing a gradient of oxygen functional groups, drops of water and dimethyl-methylphosphonate (a nerve agent simulant) are "pulled" in the direction of increasing oxygen content, while fluorine gradients "push" the droplet motion in the direction of decreasing fluorine content. The direction of motion is broadly attributed to increasing/decreasing hydrophilicity, which is correlated to high/low adhesion and binding energy. Such tunability in surface chemistry provides additional capabilities in device design for applications ranging from microfluidics to chemical sensing.