Lithium Ion-selective Electrode Research Articles

Enhancement of the cycling stability of an electrochemical lithium recovery system via state-of-charge (SoC) control

Based on the lithium ion selective electrode, electrochemical lithium recovery (ELR) is a promising lithium recovery technology in which lithium ions are adsorbed and desorbed on the electrode. However, the stability of the ELR system is not sufficient for continuous lithium ion recovery. Here, we report a novel approach for improving the stability of the ELR system through the state-of-charge (SoC) control scheme. In this system, the electrode is composed of lithium manganese oxide (LiMn2O4, LMO) and silver (Ag), and lithium ions are captured in the LMO electrode. The stability of the LMO electrode is improved by using 60 % of the maximum capacity via SoC control. After 50 cycles, the 60 % SoC discharge capacity is maintained at 85.4 %, showing better performance compared to the 100 % SoC approach (60.0 % discharge capacity). In addition, the performance of lithium recovery with 60 % SoC control was more energy efficient with similar lithium ion capacity and selectivity compared to the 100 % SoC operation method. These results suggest that the SoC control scheme could be an efficient method to enhance the stability of ELR techniques.

(Invited) Surface Electrochemistry and Physicochemical Behaviors of Carbon and Compound Electrodes in Electrochemical Separation Systems

In recent years, electrochemical separation systems have received a great attention due to their excellent capabilities in environmental remediation, water desalination, and resource recovery. The performances of electrochemical separation systems are often interpreted in terms of capacity and selectivity, both of which are highly dependent on electrode materials. For instance, capacitive deionization (CDI) used for desalination of water employs activated carbon electrodes, as it enables capture and release of sodium chloride in large amounts. In addition, lithium-ion selective electrode such as delithiated LiMn2O4 (i.e. λ-MnO2) or LiFePO4 plays an essential role in selectivity of electrochemical lithium recovery systems. However, although the importance electrode materials cannot be overemphasized for such electrochemical separations, it is also true that we are yet to achieve a sufficient level of understanding on their behaviors in the systems, which is necessary to establish rational electrode-design strategies to enhance capacity and selectivity of the electrochemical separation systems. In this talk, our recent findings on surface electrochemistry of carbon electrodes in electrochemical desalination will be introduced, together with an overview on the non-favorable Faradaic reactions thoroughly characterized with the assistance of various X-ray and electrochemical techniques. Additionally, development of heteroatom-doped carbon material and how it resulted in a highly stable CDI performance will be presented. Moreover, I will talk about our efforts on characterization of physicochemical behavior of λ-MnO2 in electrochemical lithium recovery systems, based on which a significantly higher utilization rate of the electrode materials could be achieved.

Use of lithium tracers to quantify drilling fluid contamination for groundwater monitoring in Southeast Asia

Drilling is widely used in groundwater monitoring and many other applications but has the inherent problem of introducing some degree of external contamination into the natural systems being monitored. Contamination from drilling fluid is particularly problematic for (i) wells with relatively low water flow rates which are difficult to flush; and for (ii) hydrogeochemical research studies of groundwaters hosted by incompletely consolidated shallow sediments, which are widely utilized as sources of drinking water and irrigation water across many parts of Asia. Here, we develop and evaluate a method that can be simply used to quantify the extent of drilling fluid contribution to a water sample either to optimize sample collection for reduced contamination, or to allow a correction for contamination to be made. We report the utility of lithium chloride tracers using both field and laboratory analytical techniques to quantitatively evaluate and correct for drilling fluid contamination of casing waters through an investigation of 15 sites in Kandal Province, Cambodia. High analytical errors limit the practicality and resolution of field-based lithium ion selective electrode measurements for purposes other than broad estimates of gross contamination. However, when laboratory analysis is integrated with the method (e.g. via inductively coupled plasma atomic emission spectrometry analysis), lithium tracers can provide a robust and accurate method for evaluating drilling-related contamination if appropriate samples are collected. Casing water is susceptible to contamination from drilling fluid which was shown to be significantly reduced within two to three well volumes of flushing but can still persist above background for greater than seven well volumes of flushing. A waiting period after drilling and prior to water sampling was shown to further decrease contamination due to dilution from the surrounding aquifer, particularly in more permeable wells. Contamination values were generally <3% for 34 monitoring wells across 15 sites after flushing a mean of 4.6 ± 3.8 well volumes, even when lithium-spiked water was directly injected during flushing to remove settled mud/debris. Operational issues can be encountered which can (i) lead to contamination being much higher than the mean if wells are highly unproductive and clay-dominated or (ii) lead to higher flushing volumes than the mean particularly in sandy areas where fine sand may enter the well screening. General correction factors have been provided for typical monitoring wells in poorly consolidated shallow aquifers in Southeast Asia, and examples provided for how to correct other groundwater data for contamination. For most analytes such as sodium or dissolved organic carbon (DOC), specific corrections may not be necessary for the typical magnitude of contamination encountered, particularly when the differences in concentrations between the drilling fluid and groundwater are relatively small. In the particular circumstance where drilling fluid may have much higher DOC than groundwaters, or vice versa with drilling fluid having much lower DOC than groundwaters in organic-rich alluvial sediments, corrections may still be necessary and significant. Similarly, for highly sensitive parameters such as 14C model age or other age-related parameters (such as tritium, chlorofluorocarbons (CFCs) or sulfur hexafluoride (SF6)), corrections can be significant in typical field scenarios particularly when contamination values are high and/or there is a large difference in age between groundwater and drilling fluid. The lithium method was verified with comparison to changes in concentration of a suite of representative and naturally occurring groundwater constituents as a function of well flushing from relatively low and high permeability groundwater monitoring wells to further illustrate the technique.

Synthesis of azacrown sulfonamides via ring closing metathesis and their evaluation in lithium ion selective electrodes

New diazapolyoxa macrocyclic ditosylates with 17–28-membered rings were synthesized by the application of the RCM technique to suitable α,ω-dienes. These compounds were employed as neutral carriers in Li-selective electrodes. The electrodes exhibited nearly Nernstian responses with relatively high selectivity for lithium over other inorganic cations.

A D2 symmetric tetraamide macrocycle based on 1,1′,4,4′-tetrahydro[3,3′(2 H,2′ H)-spirobiquinoline]-2,2′-dione: synthesis and selectivity for lithium over sodium and alkaline earth ions

Macrocyclic ionophores d, l- 3 and d, l- 4 with four amide carbonyl ligands were synthesized and investigated in lithium ion-selective electrodes. In solvent PVC membranes, ion selectivity of d, l- 3 and d, l- 4 for lithium relative to sodium was observed as log K Li , Na pot = − 1.4 and −1.23, respectively. Spiromacrocycle d, l- 3 and analogue dibenzospiromacrocycle d, l- 4 have similar ion selectivity patterns for alkali metal ions, but d, l- 4 could discriminate against alkaline earth metal ions better than d, l- 3. It is an example of an endopolarophilic/exolipophilic macrocyclic ionophore whose selectivity for monovalent cations over divalent cations is enhanced by thick lipophilic shells.

Practical Application of Lithium Ion-selective Electrode (ISE) Assay and Population Pharmacokinetic Approach to Therapeutic Drug Monitoring (TDM) Services in Psychiatry

Practical Application of Lithium Ion-selective Electrode (ISE) Assay and Population Pharmacokinetic Approach to Therapeutic Drug Monitoring (TDM) Services in Psychiatry

Lithium Ion-selective Electrodes Employing Tetrahydrofuran-based 16-Crown-4 Derivatives as Neutral Carriers

The potentiometric response characteristics of lithium ion-selective membrane electrodes employing three different THF-type 16-crown-4 derivatives as ionophores were investigated. Of the THF- based crown compounds tested, a cis-type isomer of the derivative with only methyl groups (H/CH3) at four bridged positions (cis-THF-I) was found to exhibit the best selectivity for Li+ over other cations. The composition of the cis-THF-I-based PVC-matrix membrane was optimized and its performance was compared with those based on lithium ionophores reported previously. The new cis-THF-I-based membrane exhibits remarkably enhanced selectivities for lithium over other cations: logKpotLi,Na = –2.8, logKpotLi,K = –4.6, logKpotLi,NH4 = –5.4, logKpotLi,Ca = –5.7 and logKpotLi,Mg = –5.4. Furthermore, it was found that serum components do not interfere significantly with the lithium measurements when the cis-THF-I-based electrode is used. The response of the electrode was found to be linear in the clinical range of interest.

Photocured polymers in ion-selective electrode membranes Part 6: Photopolymerized lithium sensitive ion-selective electrodes for flow injection potentiometry

A photocured lithium ion-selective electrode, based on the ionophore N, N-dicyclohexyl- N′, N′-diisobutyl- cis-cyclohexane-1, 2-dicarboxamide (ETH 1810), was developed and evaluated. The robust nature of the photocured membrane made it ideally suitable for measurements in flow injection potentiometry within a linear range 0.1–10 −3 M, detection limit of 5 × 10 −4 M, and sample throughput of 150 h −1. The electrode was used successfully to determine lithium levels in pharmaceutical lithium carbonate tablets.

ChemInform Abstract: New Class of Lithium Ion Selective Crown Ethers with Bulky Decalin Subunits

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Voltammetric Lithium Ion-Selective Electrodes Based on Ion Transfer at the Oil/Water Interface Facilitated by Neutral Ionophores

Voltammetric measurements were performed for the transfers of Li+ and Na+ at an oil/water interface facilitated by neutral ionophores including 14-crown-4 derivatives. For the organic solvent, nitrobenzene, o-nitrophenyloctylether (NPOE) and o-nitrophenylphenylether (NPPE) were examined. The interface between water and NPPE containing 20 mM dibenzyl-14-crown-4 was found to serve best for the ion-selective-electrode (ISE) surface for the voltammetric determination of Li+. A test of this voltammetric LiMSE using artificial serum showed that the interference from a large amount (ca, 140 mM) of Na+ in blood can be easily avoided by detecting the Na+ concentration simultaneously with the same electrode.

Lithium Ion-Selective Electrodes Based on 1,10-Phenanthroline Derivatives

The preparation of 1, 10-phenanthroline derivatives and 4, 7-diphenyl-1, 10-phenanthroline derivatives as neutral carriers for ion-selective electrodes and the properties of the title electrodes are described in detail. A log KPotLi, Na value of -3.1 was obtained for a Li+-selective PVC membrane electrode based on 2, 9-dibutyl-1, 10-phenanthroline. This value is superior to those reported so far. The electrodes also showed excellent selectivity coefficients for Li+ relative to K+, Mg2+, and Ca2+ The effects of substituents at the 2- and 9- positions of the carriers on the selectivity are discussed.

Lithium ion selective electrodes based on 14-crown-4 derivatives bearing lipophilic substituents as ionophores.

Eight 14-crown-4 derivatives carrying two, three or four bulky substituents have been synthesized in an attempt to improve the selectivity of the parent macrocycles for Li+ The bulky lipophilic substituents are expected to suppress the formation of stable 2 : 1 (crown ether/cation) complexes with Na+. The selectivity for Li+ against Na+ increased with bulkiness of the substituents up to bearing two benzyl groups and then leveled off with bulkier substituents. In the cases of multi-substituted 14-crown-4 derivatives, however, there was a pronounced drop in the Li+ preference over the other cations except for Na+, compared to dibenzyl- and/or dodecyl methyl-14-crown-4.

Synthesis and binding properties of lithium-selective [14]-O 4 macrocycles and their use in a lithium ion-selective electrode

The [14]-O 4 dibutylamide derivative 1 is a selective lithium ionophore

A comparative study of the effect of o-nitrophenyl octyl ether and o-nitrophenyl pentyl ether as plasticizers on the response and selectivity of carrier-based liquid membrane ion-selective electrodes

Lithium, potassium and caesium-selective microelectrodes were prepared by coating the tips of preconditioned silver wires, incorporated in a flow-cell, with PVC membranes containing four different ionophores. A dicarboxamide, a 14-crown-4 carboxylic acid, benzo-18-crown-6 and di-( tert-butylbenzo)-21-crown-7 ionophores were used in the electrode matrix. The first two ionophores were used in lithium ion-selective electrodes, the third in a potassium ion electrode and the fourth in a caesium ion electrode. Two different plasticizers, o-nitrophenyl octyl ether (NPOE) and o-nitrophenyl pentyl ether (NPP'E) were used. Enhancement of the signal and the slope of the calibration curve and improvement of the curve linearity were observed in all cases when NPP'E was used as plasticizer. A general trend of enhanced selectivity of the electrodes incorporating crown ether ionophores was also observed when NPP'E was the plasticizer.

Lithium determined in serum with an ion-selective electrode.

We evaluated the performance of the lithium ion-selective electrode (ISE) in the Du Pont Na/K/Li analyzer. Lithium concentrations in 106 serum samples from patients being treated with lithium were measured in duplicate with the ISE and by flame photometry. The slope of the regression line for the two methods was 1.004 with a standard error of the estimate of 0.049 mmol/L (x = flame photometry, y = ISE). Lithium measurements by the ISE method in serum or aqueous standards were linear to greater than 2.0 mmol/L. Within-run CVs for low (0.31 mmol/L) and high (1.15 mmol/L) lithium controls were 5.9% and 1.7%, respectively (n = 20). Day-to-day CVs for the same controls were 9.8% and 3.3%, respectively (n = 20). There was no significant interference when the concentrations of sodium, potassium, calcium, or magnesium were varied, nor did intervening urinary lithium analyses affect the measurement of serum lithium. Results for lithium measurement in four serum-based survey materials compared well with results by isotope dilution/mass spectrometry.

Lithium ion selective electrodes based on crown ethers for serum lithium assay.

Previous Li/sup +/-selective polymeric membrane electrodes based on 14-crown-4 derivative 1 have been improved in the Li/sup +/ selectivities against Na/sup +/ and K/sup +/ by using 2 and 3 as the neutral carrier. Examination of the membrane solvents for the electrodes allowed further enhancement in the Li/sup +/ selectivities. An excellent k/sub LiNa//sup Pot/ value of 1.3 x 10/sup -3/ was attained with the poly(vinyl chloride) membrane containing 2 as the neutral carrier and o-nitrophenyl phenyl ether/tris(2-ethylhexyl) phosphate (98/2) as the solvent. Serum Li/sup +/ assay was successfully achieved with an electrode containing a combination of the optimized membrane based on the crown ether and a dialysis membrane, which eliminated interference by proteins in the samples.

1,3-Bis(8-quinolyloxy)propane derivatives as neutral carriers for lithium ion selective electrodes

1,3-Bis(8-quinolyloxy)propane derivatives as neutral carriers for lithium ion selective electrodes

Flow injection study of the potentiometric lithium selectivity of cyclic dioxadiamides containing oxygen and nitrogen atoms

Four 15-membered ring cyclic compounds with two oxygen and two nitrogen atoms incorporated in the ring were prepared and evaluated as neutral carriers in lithium ion-selective electrodes. These ionophores, along with potassium tetrakis (p-chlorophenyl)borate and o-nitrophenyloctyl ether (NPOE), were included in the PVC matrix that coated the tip of a silver-wire electrode. The potentiometric selectivities of the electrodes towards lithium over sodium, potassium, calcium and magnesium were determined. Selectivity coefficients, K Li, Na pot ., as low as 9.5×10−3 were obtained and smaller coefficients for other metals, K Li, M pot ., were found. A calibration curve for lithium in the presence of 140 mmol/l sodium, with a linear portion having a slope of 51 mV/decade, was obtained. The effect of incorporating 1% trioctylphosphine oxide (TOPO) in the electrodes was studied. Comparison with the results obtained with 15-crown-4-ethers is made.

Lithium ion-selective electrodes containing TOPO: determination of serum lithium by flow injection analysis.

Trioctylphosphine oxide (TOPO) acts as a neutral lithium carrier in lithium ion-selective electrode membranes. When TOPO was used with 1% potassium tetrakis(p-chlorophenyl) borate in NPOE-PVC membranes, the electrodes exhibited a nearly Nernstian response and had a lithium to sodium selectivity of 1 : 60, which is better than some electrode sensors reported earlier. TOPO was also added to 14-crown-4, ETH 1810 and UWXC 10 electrode membranes, and the lithium to sodium selectivity of the 14-crown-4 electrode was dramatically improved. However, TOPO had a negative effect on the selectivities of the ETH 1810 and UWXC 10 electrodes. Diluted serum samples were analysed for lithium using the 14-crown-4-TOPO electrode in an FIA system. A statistical analysis of the ISE and corresponding AAS results indicated that these two methods have no statistical difference at the 95% confidence level. Because of the improved selectivity of the electrode and the elimination of the dialysis membrane from our original FIA design, the precision and accuracy of this determination were both improved, and the measurement time decreased.

3,7‐Dioxaazelaamides as Ionophores for Lithium Ion Selective Liquid Membrane Electrodes

AbstractLipophilic neutral carriers were synthesized which show Li+/Na+ selectivities of up to ca. 80 in highly lipophilic liquid membranes. The sensor membranes exhibit improved response times and increased lifetimes as compared to systems described earlier. They allow reliable measurements of Li+ in blood serum within the clinical concentration range. A 1:1 Li+/ionophore complex of one representative (N,N,N′,N′‐tetracyclohexyl‐5,5‐dimethyl‐3,7‐dioxaazelaamide) has been prepared, and its structure was elucidated by X‐ray analysis.