What can in situ ion chromatography offer for Mars exploration?

Functionalization of High-Density Polyethylene Capillaries for Open Tubular Ion Chromatography

Ion chromatography is the anion analysis benchmark. A miniature form, Open Tubular Ion Chromatography (OTIC), has attractive attributes for efficient ion separations. Here, we fabricate and characterize high-density polyethylene (HDPE) open tubular anion exchange columns (OTCs). We attach positively charged latex particles onto negatively charged capillary surfaces. For efficient OTIC, column diameters need to be < ∼20 µm; functionalizing the bore is challenging. Methods to introduce acid groups to an HDPE capillary bore, e.g., sulfonation using chlorosulfonic or sulfuric acid solutions, with or without grafting of an aromatic ring through photo- or chemical grafting first, are explored. Following quaternary ammonium latex attachment, the ion exchange capacity and separating abilities of each OTC were measured as an index of OTC performance. Gradual loss of capacity was observed for many of these; high-resolution mass spectrometry confirmed the leaching of detached oxidized/sulfonated oligomeric fragments and consequent poisoning of the latex sites. Ways to ameliorate this and/or to rejuvenate the columns are also described.

Portable light weight open tubular ion chromatograph for field determination of environmental anions

We report a battery powered non-suppressed open tubular ion chromatograph (NSOTIC) that weighs less than 3 kg with on-board rechargeable lithium-ion batteries that provide power for 18 h of operation. It is contained in an aluminum case measuring 30 × 25 × 16 cm. Separation relies on open tubular (OT) chromatographic columns which eliminate the need for high pressure pumps, drastically reducing weight and complexity. Eluent consumption is less than 100 µL per separation. Eluent is supplied from a pressurized vessel via a voltage-controlled electronic pressure controller. Flow rates are typically <200 nL/min which allows a single 16-20 g gas cartridge to perform hundreds of separations. Two anions, chloride and nitrate, in Atacama soil samples were field determined by running the portable NSOTIC. More samples were lab analyzed by commercial IC and IC/MS-MS (only perchlorate due to its low concentration level). To demonstrate the feasibility of running NSOTIC on sample analysis, samples were tested by both non-portable and portable NSOTIC.

Extraction and Separation of Chiral Amino Acids for Life Detection on Ocean Worlds Without Using Organic Solvents or Derivatization

In situ instrumentation that can detect amino acids at parts-per-billion concentration levels and distinguish an enantiomeric excess of either d- or l-amino acids is vital for future robotic life-detection missions to promising targets in our solar system. In this article, a novel chiral amino acid analysis method is described, which reduces the risk of organic contamination and spurious signals from by-products by avoiding organic solvents and organic additives. Online solid-phase extraction, chiral liquid chromatography, and mass spectrometry were used for automated analysis of amino acids from solid and aqueous environmental samples. Carbonated water (pH ∼3, ∼5 wt % CO₂ achieved at 6 MPa) was used as the extraction solvent for solid samples at 150°C and as the mobile phase at ambient temperature for chiral chromatographic separation. Of 18 enantiomeric amino acids, 5 enantiomeric pairs were separated with a chromatographic resolution >1.5 and 12 pairs with a resolution >0.7. The median lower limit of detection of amino acids was 2.5 μg/L, with the lowest experimentally verified as low as 0.25 μg/L. Samples from a geyser site (Great Fountain Geyser) and a geothermal spring site (Lemon Spring) in Yellowstone National Park were analyzed to demonstrate the viability of the method for future in situ missions to Ocean Worlds.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Open tubular ion chromatography: A state-of-the-Art review

This review summarizes the progress in open tubular ion chromatography (OTIC) over the period from 1981 to 2020. Although OTIC columns provide superior column efficiency, require very little sample volumes, and consume a minimum level of eluents compared to regular packed columns, not many reports can be found from the literature mainly due to the difficulties in the preparation of OTIC columns and the harsh system requirements, such as pL-nL injections and extremely small detection volumes. However, technical advances, e.g., capacitively coupled contactless conductivity detectors (C⁴Ds), hydroxide eluent compatible polymer-based OTIC columns, electrodialytic capillary suppressors, and nanovolume gas-free hydroxide eluent generators (EGs), have removed the obstacles to OTIC. As such, in this review, the author focused on the development of the key components in an OTIC system from the perspective of instrument development. A brief revisit of open tubular (OT) column theory is first presented, followed by a discussion of the system configuration and component development. Attention is given to the advances in the development of the suppressed open tubular ion chromatography (SOTIC) system.

Complete capillary electrophoresis process on a drone: towards a flying micro-lab

Hazardous remote places exist in the world. Why should health or life be risked sending a scientist to the investigation site, as the remote analytical instrumentation exists? Different scientific fields require instruments that could be used on-site (in situ), therefore the purpose of this work was to design a fully automated chemical analysis system small enough to be mountable on a drone. Here we show an autonomous analytical system with sampling capability on a drone. The system is suited for the remote and autonomous analysis of volatile and non-volatile chemicals in the air. The designed system weighs less than 800 g. Data are transmitted wirelessly. Collected substances are separated automatically without the intervention of the operator using the method of capillary zone electrophoresis. The analytes are detected using a miniaturized contactless conductivity detector quantifying them down to less than 1 μM. In this work, we demonstrated sampling and separation of volatile amines (triethylamine and diethylamine) and organic acids (acetic and formic acids), non-volatile inorganic cations (K⁺, Ca²⁺, Na⁺), and protein (bovine serum albumin) in the aerosol state. It was shown that the capillary electrophoretic analysis can be performed on a hovering drone. We anticipate our work to be a starting point for more sophisticated, autonomous complex sample analysis. We believe that our designed instrument will enable the investigation of hazardous places in different research fields.

Hand-portable liquid chromatographic instrumentation

Over the last four decades, liquid chromatography (LC) has experienced an evolution to smaller columns and particles, new stationary phases and low flow rate instrumentation. However, the development of person-portable LC has not followed, mainly due to difficulties encountered in miniaturizing pumps and detectors, and in reducing solvent consumption. The recent introduction of small, non-splitting pumping systems and UV-absorption detectors for use with capillary columns has finally provided miniaturized instrumentation suitable for high-performance hand-portable LC. Fully integrated microfabricated LC still remains a significant challenge. Ion chromatography (IC) has been successfully miniaturized and applied for field analysis; however, applications are mostly limited to inorganic and small organic ions. This review covers advancements that make possible more rapid expansion of portable forms of LC and IC.