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Ionophore-Based Titrimetric Detection of Alkali Metal Ions in Serum
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Ionophore-Based Titrimetric Detection of Alkali Metal Ions in Serum
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  • Jingying Zhai
    Jingying Zhai
    Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
  • Xiaojiang Xie
    Xiaojiang Xie
    Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518000, China
  • Thomas Cherubini
    Thomas Cherubini
    Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
  • Eric Bakker*
    Eric Bakker
    Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
    *E-mail: [email protected]
    More by Eric Bakker
Open PDFSupporting Information (2)

ACS Sensors

Cite this: ACS Sens. 2017, 2, 4, 606–612
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https://doi.org/10.1021/acssensors.7b00165
Published April 12, 2017

Copyright © 2017 American Chemical Society. This publication is licensed under these Terms of Use.

Abstract

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While the titrimetric assay is one of the most precise analytical techniques available, only a limited list of complexometric chelators is available, as many otherwise promising reagents are not water-soluble. Recent work demonstrated successful titrimetry with ion-exchanging polymeric nanospheres containing hydrophobic complexing agents, so-called ionophores, opening an exciting avenue in this field. However, this method was limited to ionophores of very high affinity to the analyte and exhibited a relatively limited titration capacity. To overcome these two limitations, we report here on solvent based titration reagents. This heterogeneous titration principle is based on the dissolution of all hydrophobic recognition components in a solvent such as dichloromethane (CH2Cl2) where the ionophores are shown to maintain a high affinity to the target ions. HSV (hue, saturation, value) analysis of the images captured with a digital camera provides a convenient and inexpensive way to determine the end point. This approach is combined with an automated titration setup. The titrations of the alkali metals K+, Na+, and Li+ in aqueous solution are successfully demonstrated. The potassium concentration in human serum without pretreatment was precisely and accurately determined as 4.38 mM ± 0.10 mM (automated titration), which compares favorably with atomic emission spectroscopy (4.47 mM ± 0.20 mM).

Copyright © 2017 American Chemical Society
In complex biological systems such as human serum, the determination of inorganic metal ions is of key importance because their levels are closely associated with patient health. (1−3) Numerous techniques and methods have been established for real sample measurements, including potentiometric and optical chemosensors, titrimetry, ion chromatography, mass spectrometry, and atomic spectroscopy. (4−9) An automated titration would be attractive because of the very high precision associated with such measurements. Its most significant challenge is to achieve sufficient selectivity for the target ion against interfering ones. For example, the measurement of K+ (in the range of 3.5 mM to 5.5 mM) in human serum is difficult because of a high Na+ background (135 mM to 145 mM) and the presence of other cations including Ca2+ (2.25 mM to 2.75 mM) and Mg2+ (0.7 mM to 1.1 mM). (4,5)
Complexometric titrations are normally performed in homogeneous aqueous phase, and for this reason chelators and indicators must be water-soluble. Chelators such as ethylenediamine tetraacetic acid (EDTA) and its derivatives diethylene triamine pentaacetic acid (DTPA) and ethylene glycol tetraacetic acid (EGTA) have been widely used in complexometric titration since 1945. (10−15) Commercially available dyes such as Eriochrome Black T and Murexide are classical dyes and function as indicators for many metal ions. (13,16,17) A rather rigid selectivity sequence and the presence of protonatable groups make it normally necessary to pretreat the sample and to use masking reagents, which is undesired.
For a lack of selective reagents, traditional titration methods for alkali metals such as K+, Na+, and Li+ are indirect and often based on salt precipitation of metals such as Zn2+, Co2+, and Ni2+. The metal can only then be determined with EDTA. (10,18) These methods are not applicable to complex physiological samples.
Recently, ion selective nanospheres, a new generation of titration reagents, moved the titration process from homogeneous to heterogeneous phase. (19−22) The use of nonpolar nanospheres makes the chelators and indicators no longer limited to water-soluble compounds. Ionophores with high selectivity to the desired metal ion can now conceivably be used in titrations, by simply doping them into the nanospheres. For example, chelating nanospheres, made of surfactant Pluronic F-127 and plasticizer, contain ion exchanger and ionophore in their core. Based on the principle of ion-exchange, the concentration of titrated analyte can be calculated by that of the ion exchanger without considering the stoichiometry between ionophore and analyte. The indicating nanospheres are formulated with similar components to the chelating nanosphere but contain an additional chromoionophore (lipophilic pH indicator) or a solvatochromic dye. This new titration priniciple based on nanospheres of high selectivity has been successfully applied to Ca2+ and Pb2+ ions. (19,20,22) Unfortunately, however, it cannot easily be extended to ionophores with lower binding affinity such as those for K+, Na+, and Li+, as the binding constants have been shown to be quite dramatically reduced in the more polar environment of the nanospheres compared to polymeric sensor materials. (23)
Two phase extractions have been widely used for separation, purification, and recovery of target products in biotechnology, food chemistry, and nuclear industry. (24−28) The two phases may be combinations of polymer/polymer, polymer/salt, polymer/water, and solvent/water systems. (29−31) In liquid–liquid systems, the extractants or ligands can be dissolved into one of the liquid phase while the analytes are present in the other phase. (32) The dissolution of the ion exchanger together with the extractants/ligands was shown to enhance the extraction efficiency and gave a reduced extraction time. (26)
To the best of our knowledge, two-phase extraction systems based on the ion exchange principle have never been applied as titration reagents in complexometric titrations. We introduce here a family of ionophore-based water-immiscible titration reagents for K+, Na+, and Li+. They function as both the chelator and indicator, dramatically simplifying the analytical procedure. These reagents not only extend the use of liphophilic compounds but also improve the capacity of the sensor components and maintain a higher affinity of the ionophore compared to nanosphere based reagents. The extraction of the analyte is rapid and the signals can be monitored by UV–visible spectroscopy or by analyzing the hue value from less expensive picture or movie acquisition data. A homemade automatic setup is introduced. The level of K+ in human serum, without the need for sample pretreatment, is successfully determined.

Experimental Section

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Reagents

Sodium tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (KTFPB), valinomycin (potassium ionophore I), 4-tert-butylcalix[4]arene tetraacetic acid tetraethyl ester (sodium ionophore X), N,N,N′,N′,N″,N″-hexacyclohexyl-4,4′,4″-propylidynetris(3-oxabutyramide) (lithium ionophore VIII), 9-(diethylamino)-5-(octadecanoylimino)-5H-benzo[a]phenoxazine (CHI), 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris), sodium chloride (NaCl), potassium chloride (KCl), lithium chloride (LiCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), dichloromethane (CH2Cl2), and hydrochloric acid (HCl) were obtained from Sigma-Aldrich. Human serum was provided by Hôpitaux Universitaires de Genève (HUG).

Preparation of Ionophore-Based Titration Reagents

Typically, for the potassium titration reagent, 0.90 mg NaTFPB and 1.60 mg potassium ionophore I were dissolved in 2.2 mL CH2Cl2 and mixed with 160 μL CHI stock solution, which was prepared by dissolving 0.2 mg CHI into 3 mL CH2Cl2. For the sodium titration reagent, 1.08 mg KTFPB and sodium ionophore X were dissolved in 2 mL CH2Cl2 and mixed with the CHI solution. For lithium titration reagent, 0.96 mg KTFPB and 2.30 mg lithium ionophore VIII were dissolved into 2 mL CH2Cl2 and mixed with the CHI solution.

Optical Titration

Typically, 2 mL of ionophore-based titration reagent was added into a quartz cuvette and mixed with 2 mL (or 1 mL) pH 7.0 (or pH 7.4) 10–2 M Tris-HCl buffer solution. The cuvette was shaken until the color of the solvent layer became blue. The back-titration was performed by gradually adding 10–2 M analyte (KCl, NaCl, LiCl) or human serum into the cuvette, each step followed by sufficient shaking. For the homemade automated titration, 10–2 M KCl or human serum was delivered from a syringe pump into a glass vial containing the titration reagent and buffer solution. The glass vial was kept vibrating throughout the experiment.

Instrumentation

Optical signals were measured with a UV–visible absorption spectrometer (SPECORD 250 plus, Analytic Jena, AG, Germany) or a digital camera (Canon EOS 5D Mark III). The homemade setup for automated titration was composed of a syringe pump (KD Scientific) and vortexer (Heidoph).

Results and Discussion

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The ionophore-based titration reagents combining the functions of chelator and indicator are shown in Scheme 1. The reagent contains excess amount of ion-exchanger (NaTFPB or KTFPB) and ionophore (potassium ionophore I, sodium ionophore X, or lithium ionophore VIII) relative to a small amount of CHI (lipophilic pH indicator) in the organic phase (CH2Cl2). The aqueous phase is a pH buffered solution. As the analyte ion is added into the aqueous phase, it is extracted into the organic phase to form a complex with the ionophore, which causes the initial counterion of the ion-exchanger to be exchanged out into the aqueous phase. Only after consuming all the counterions of the ion exchanger, the analyte ions will be exchanged with the more tightly bound hydrogen ions in the organic phase. This causes the deprotonation of protonated CHI, resulting in a drastic color change at the end point. The ionophore-based titration reagents function on the basis of the ion-exchange principle, which is briefly quantified here mathematically.

Scheme 1

Scheme 1. Working Principle of the Solvent Based Titration Reagentsa

a(a) Before end point. (b) After end point.

Before the end point, the titration process can be described by the overall equilibrium (1)
(1)
With the corresponding exchange constant K1
(2)
where I+ is the analyte ion (K+ or Na+ or Li+), L is the ionophore, and J+ is the counterion (interfering ion) of the TFPB. IL+ and JL+ are the complexed primary ion and interfering ion. NaTFPB is used for K+ titration whereas KTFPB served as cation-exchanger salt for Na+ and Li+ titration. The stoichiometry of monovalent analyte ion with ionophore complex is 1:1, while [IL+]org, [J+]aq, [I+]aq, and [JL+]org are molar concentrations of the indicated species.
At the end point, the process is described by equilibrium (eq 3)
(3)
With the corresponding exchange constant K2
(4)
Where Hind and ind are the protonated and deprotonated CHI, [ind]org and [Hind+]org are the corresponding concentrations, and [H+]aq is the concentration of hydrogen ions in the aqueous phase. Based on this theory, the theoretical titration curves are obtained to fit the experimental data (see eqs S1 to S9 in Supporting Information for details).
The experimental titration curves for K+, Na+, and Li+ and the corresponding spectra are shown in Figure 1. The ionophore-based titration reagents were readily prepared by dissolving the corresponding ionophores, ion-exchanger, and a very small amount of CHI in CH2Cl2. The titrations were performed at pH 7.0 for K+ and pH 7.4 for Na+ and Li+. As shown in Figure 1a,d, KCl was gradually added into the aqueous phase and each step was recorded by absorbance after equilibration.

Figure 1

Figure 1. Optical reverse titration curves (a, b, c) and corresponding absorption spectra (d, e, f) for K+, Na+, and Li+, respectively. Titrant: 10–2 M KCl or NaCl or LiCl. The dashed vertical lines indicate the expected end point. Buffer solution: 10–2 M Tris-HCl pH 7.0 for K+ titration; 10–2 M Tris-HCl pH 7.4 for Na+ and Li+ titration. Absorption spectra recorded at each titration point.

Based on the ion-exchange principle, the molar amount of ion exchanger corresponds to the one of K+ that can be consumed by the reagent. The ionophore is in excess of the ion exchanger, and for this reason, the stoichiometry between the K+ and potassium ionophore I does not necessarily need to be considered.
Before the end point, K+ will be exchanged into the organic phase by the counterion (Na+) of the TFPB and complexed with the potassium ionophore I. Here, CHI remains in the protonated state and the color of the organic phase is blue. After consuming all the Na+, K+ will exchange into the organic phase by expelling hydrogen ions bound to the indicator into the aqueous phase. At the end point, therefore, the color of the organic phase turns purple. Beyond the end point, CHI will become fully deprotonated and the color will change to red. During the titration, the volume of added analyte solution, i.e., the increase of the total volume of aqueous phase, should be taken into account, as done in our theoretical treatment (see SI for details).
Compared to ion selective nanosphere-based titration reagents (Figure S1), the titration curve for K+ shown in Figure 1a is much sharper and more accurate with an error of less than 1%. The titration based on nanosphere reagents only exhibited accurate and sharp transition (Figure S1a) when the ionophore had a sufficiently high effective binding constant, as with calcium ionophore II for calcium. Indeed, our efforts to achieve nanosphere-based K+ titrations with potassium ionophore I was not successful, as the experimental end point was found to be far from the correct one, with an error of about 48%. The logarithmic effective binding constants (logβ) of potassium ionophore I in the nanospheres has recently been determined as 6.1 ± 0.1, (23) about 4 orders of magnitude lower than those reported earlier in PVC-DOS membrane (logβ = 10.1 ± 0.2). (33) The corresponding value in CH2Cl2 was here experimentally determined as 10.2 ± 0.1 which is practically identical to that found in PVC-DOS by using a previously reported method. (34) It appears that only ionophores with high binding constants can be used for nanosphere-based titration reagents. Additionally, nanosphere-based titration reagents cannot be endowed with a high ion-exchange capacity, as increasing the nanosphere concentration results in aggregation and light scattering limitations. On the other hand, it is easier to dissolve sensor components in CH2Cl2 with the aim to increase the titration capacity and to allow for the analysis of even highly concentrated samples. In the configuration tested here, the equilibration time of the ionophore based assay was found to be around 4 s at the end point, likely limited by convective mixing.
For the Na+ and Li+ titrations shown in Figure 1b,c and e,f, the reagents contain similar sensor components as for the K+ titration (see Experimental Section). Both titration curves are sharp and accurate with small errors of less than 1%. The different shapes of the titration curves are due to the difference in the complex formation constants. Here, potassium ionophore I exhibits the highest binding constant compared to sodium ionophore X and lithium ionophore VIII and thus the K+ titration curve appears the sharpest. (33) All titration curves agree very well with theory (see Supporting Information).
The selectivity of the ionophore based reagents was evaluated; see Figure 2. To obtain sigmoidal calibration curves useful for visual selectivity analysis, the solvent contained ion exchanger and CHI at a 1:1 molar ratio instead of excess amount of ion exchanger over CHI, while maintaining an excess of ionophore. The response of the ion selective reagent to various cations is shown in Figure 2. The horizontal distance between the calibration curves for the primary ion and any interfering ion on the logarithmic concentration scale reflects the selectivity: the larger the separation, the more selective the reagent. For example, the distances between K+ and Na+, K+ and Li+ are 4.4, 4.8 logarithmic units, respectively (Figure 2a), and so the K+ reagent can tolerate more Li+ than Na+ in the sample. The distance is also indicative of the exchange constant (log K1) between the primary ion I+ and complexed interfering ion JL+. The log K1 values obtained from Figure 2 were used for theoretical predictions.

Figure 2

Figure 2. Response of the K+ (a), Na+ (b), and Li+ (c) selective reagents to various interfering ions, respectively. Buffer solution: (a)10–2 M Tris-HCl pH 7.0, (b,c) 10–2 M Tris-HCl pH 7.4. The horizontal distance between the calibration curve for primary ion and any interfering ions represents log K1.

The experimental K+ titrations with a background of 10–2 M (with accurate end point) and 10–1 M NaCl (with less than 1% error) are shown in Figure S2(a,b). Theory predicts an error of 1.3% for a 0.15 M Na+ background, which is adequate for K+ titration in human serum.
Figure S3(a,b) shows the Na+ titration and Li+ titration against a background of 10–3 M KCl and 10–1 M KCl, respectively. Both titrations are successful and give acceptable errors: the theoretical error prediction for Na+ titration against a 3.3 mM and 5.5 mM KCl background is 2.6% and 4.4%, respectively.
For Li titration, the Li selective reagent can tolerate a very high concentration of KCl, giving a calculated error of 1.1% for 10–1 M KCl. Unfortunately, it cannot tolerate a high concentration of Na+ because of limited selectivity and is not suitable for Li+ titration in serum.
The K+ selective ionophore-based titration reagent was chosen as an initial example to demonstrate the titrimetric assay in human blood serum. Considering the major cationic interfering species Na+ (135 mM to 145 mM), Ca2+ (2.25 mM to 2.75 mM), and Mg2+ (0.7 mM to 1.1 mM), the K+ selective reagent showed no response to Ca2+ and Mg2+ in the concentrations of interest, leaving Na+ as the major interferent. (35) In agreement with predictions, end point analysis gave a potassium concentration of 4.32 ± 0.10 mmol/L (Figure S4), which agrees with the results from atomic emission spectrometry (AES: 4.47 ± 0.20 mmol/L). Figure 3 shows photographic images of the K+ titration process. After each dose of KCl solution, the pictures were taken immediately after shaking but before separation of the two phases (Figure 3a). Figure 3b shows the corresponding pictures captured after complete phase separation.

Figure 3

Figure 3. Pictures of the K+ titration process after shaking (a) and after two phases separated (b) and the corresponding titration curves (c) and (d) based on the HSV analysis. The dashed vertical lines indicate the expected end points. Buffer solution: 10–2 M Tris-HCl pH 7.0.

The end points can equally be obtained by HSV (hue, saturation, value) analysis of images or videos captured with a digital camera, which is instrumentally convenient. HSV is a cylindrical-coordinate representation of pixels in an RGB (red, green, blue) color model where each pixel is defined by the hue (H), saturation (S), and value (V) coordinates in the color space. The use of the hue from images in HSV color space has been shown to be a robust parameter for quantitative analysis of the response of optical sensors. (36,37) The titration curves from pictures taken before and after phase separation are plotted as the computed hue value to the ratio of nK+:nTFPB– and shown in Figure 3c and d, respectively. The hue signals were extracted from the pictures by software (Wolfram Mathematica). The titration curves appear the same and the transitions are very sharp, independent of the two phases being mixed or separated. The titration curves agree with the model and result in errors of less than 1%. Serum titrations were also performed by analyzing the hue signals from the images; see Figure S5. Based on the total amount of the NaTFPB in the titration reagent and the volume of added human serum at the end point, the level of K+ was again determined as 4.40 ± 0.10 mmol/L.
From a practical point of view, an automated titration is preferred for routine analysis. For this purpose, a homemade automatic reverse titration setup was built; see Figure 4a,b. It comprises a syringe pump to inject accurate sample volumes and a vortex to efficiently mix the two phases (aqueous buffer and CH2Cl2). The syringe pump delivers precise volumes of the sample while a digital camera focuses on the colored CH2Cl2 part to record consecutive images or a single movie. The K+ titration curve from the movie hue signals is shown in Figure 4c. Sharp transitions were obtained successfully and the experimental end point agreed with the expected one. The K+ level in undiluted human serum was also successfully determined with this homemade automatic titration setup as 4.38 ± 0.10 mmol/L (see Figure 4d and video in the Supporting Information).

Figure 4

Figure 4. Setup of the automated titration: (a) before titration, (b) after the end point. (c) Titration analysis for K+ based on the hue signals retrieved from the frames in the video. (d) Serum titration based on the hue signals retrieved from the frames in the video. Organic phase: K+ selective titration reagent. Aqueous phase: 10–2 M Tris-HCl pH 7.0 buffer solution. The volume of the added serum at the end point is Vserum = 73 μL.

In conclusion, we describe here for the first time the use of ionophore based ion-selective titration reagents as combined chelator/indicator in complexometric titrations. This class of titration reagents exhibits higher binding constants and extraction capacity relative to the emulsion based approach reported earlier. Chemically selective K+, Na+, and Li+ titrations were successfully demonstrated. The K+ level in undiluted human blood serum was satisfactorily determined, which is promising for a possible clinical application. We note that with the current experimental setup, a complete K+ titration in serum takes about 30 min, which needs to be shortened for an application in routine practice.

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssensors.7b00165.

  • Detailed theoretical approach; additional results on optical reverse titration, experimental titration curve, and serum titration (PDF)

  • Automatic titration of potassium in human serum by using home-made setup (AVI)

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Author Information

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  • Corresponding Author
  • Authors
    • Jingying Zhai - Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
    • Xiaojiang Xie - Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518000, China
    • Thomas Cherubini - Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The authors thank the Swiss National Science Foundation (SNF) and the University of Geneva for financial support and Valentin Waeber for technical assistance in extracting color information from the movie frames. Jingying Zhai gratefully acknowledges support by the China Scholarship Council (CSC).

References

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This article references 37 other publications.

  1. 1
    Yu, S. P.; Canzoniero, L. M.; Choi, D. W. Ion homeostasis and apoptosis. Curr. Opin. Cell Biol. 2001, 13, 405411,  DOI: 10.1016/S0955-0674(00)00228-3
  2. 2
    Kuo, H.-C.; Cheng, C.-F.; Clark, R. B.; Lin, J. J.-C.; Lin, J. L.-C.; Hoshijima, M.; Trân, V. T. B. N.; Gu, Y.; Ikeda, Y.; Chu, P.-H.; Giles, W. R.; Chien, K. R.; Ross, J. A defect in the Kv channel-interacting protein 2 (KChIP2) gene leads to a complete loss of Ito and confers susceptibility to ventricular tachycardia. Cell 2001, 107 (6), 801813,  DOI: 10.1016/S0092-8674(01)00588-8
  3. 3
    Krishna, G. G.; Miller, E.; Kapoor, S. Increased blood pressure during potassium depletion in normotensive men. N. Engl. J. Med. 1989, 320 (18), 11771182,  DOI: 10.1056/NEJM198905043201804
  4. 4
    Zhang, S.; Zhang, R.; Ma, B.; Qiu, J.; Li, J.; Sang, Y.; Liu, W.; Liu, H. Specific detection of potassium ion in serum by a modified G-Quadruplex method. RSC Adv. 2016, 6, 4199942007,  DOI: 10.1039/C6RA04046B
  5. 5
    Yang, L.; Qing, Z.; Liu, C.; Tang, Q.; Li, J.; Yang, S.; Zheng, J.; Yang, R.; Tan, W. Direct fluorescent detection of blood potassium by ion-selective formation of intermolecular G-Quadruplex and ligand binding. Anal. Chem. 2016, 88, 92859292,  DOI: 10.1021/acs.analchem.6b02667
  6. 6
    Harrington, J. M.; Young, D. J.; Essader, A. S.; Sumner, S. J.; Levine, K. E. Analysis of human serum and whole blood for mineral content by ICP-MS and ICP-OES: development of a mineralomics. Method. Biol. Trace Elem. Res. 2014, 160, 132142,  DOI: 10.1007/s12011-014-0033-5
  7. 7
    Chuang, F. S.; Sarbeck, J. R.; John, P. A. S.; Winefordner, J. D. Flame spectrometric determination of sodium, potassium and calcium in blood serum by measurement of microsamples. Microchim. Acta 1973, 61 (4), 523531,  DOI: 10.1007/BF01217998
  8. 8
    Buchberger, W. W. Detection techniques in ion chromatography of inorganic ions. TrAC. TrAC, Trends Anal. Chem. 2001, 20, 296303,  DOI: 10.1016/S0165-9936(01)00068-1
  9. 9
    Moody, G. J.; Saad, B. B.; Thomas, J. D. R. Studies on bis(crown ether)-based ion-selective electrodes for the potentiometric determination of sodium and potassium in serum. Analyst 1989, 114, 1520,  DOI: 10.1039/an9891400015
  10. 10
    Schwarzenbach, G.; Flaschka, H. Complexometric titrations; Methuen: London, 1969.
  11. 11
    Salvatore, M. M.; Salvatore, F. Understanding complexometric titrations of metal cations with aminopolycarboxylic acids (EDTA and analogs) within the frame of the notion of reactions between groups of chemical species. Word J. Chem. Educ. 2015, 3, 521,  DOI: 10.12691/wjce-3-1-2
  12. 12
    Roy, N.; Nath, S.; Dutta, A.; Mondal, P.; Paul, P. C.; Singh, T. S. A highly efficient and selective coumarin based fluorescent probe for colorimetric detection of Fe3+ and fluorescence dual sensing of Zn2+ and Cu2+. RSC Adv. 2016, 6, 6383763847,  DOI: 10.1039/C6RA12217E
  13. 13
    Karita, S.; Kaneta, T. Chelate titrations of Ca2+ and Mg2+ using microfluidic paper-based analytical devices. Anal. Chim. Acta 2016, 924, 6067,  DOI: 10.1016/j.aca.2016.04.019
  14. 14
    Bian, X.; Lockless, S. W. Preparation to minimize buffer mismatch in isothermal titration calorimetry experiments. Anal. Chem. 2016, 88 (10), 55495553,  DOI: 10.1021/acs.analchem.6b01319
  15. 15
    Afshar, M. G.; Crespo, G. A.; Bakker, E. Coulometric calcium pump for thin layer sample titrations. Anal. Chem. 2015, 87 (19), 1012510130,  DOI: 10.1021/acs.analchem.5b02856
  16. 16
    Chakma, B.; Jain, P.; Singh, N. K.; Goswami, P. Development of an indicator displacement based detection of malaria targeting HRP-II as biomarker for application in point-of-care settings. Anal. Chem. 2016, 88, 1031610321,  DOI: 10.1021/acs.analchem.6b03315
  17. 17
    Männel-Croisé, C.; Meister, C.; Zelder, F. ″Naked-Eye″ screening of metal-based chemosensors for biologically important anions. Inorg. Chem. 2010, 49 (22), 1022010222,  DOI: 10.1021/ic1015115
  18. 18
    Swain, B. Recovery and recycling of lithium: A review. Sep. Purif. Technol. 2017, 172, 388403,  DOI: 10.1016/j.seppur.2016.08.031
  19. 19
    Zhai, J.; Xie, X.; Bakker, E. Ionophore-based ion-exchange emulsions as novel class of complexometric titration reagents. Chem. Commun. 2014, 50, 1265912661,  DOI: 10.1039/C4CC05754F
  20. 20
    Zhai, J.; Xie, X.; Bakker, E. Ion-Selective optode nanospheres as heterogeneous indicator reagents in complexometric titrations. Anal. Chem. 2015, 87 (5), 28272831,  DOI: 10.1021/ac504213q
  21. 21
    Zhai, J.; Xie, X.; Bakker, E. Anion-exchange nanospheres as titration reagents for anionic analytes. Anal. Chem. 2015, 87 (16), 83478352,  DOI: 10.1021/acs.analchem.5b01530
  22. 22
    Zhai, J.; Xie, X.; Bakker, E. Solvatochromic dyes as pH-independent indicators for ionophore nanosphere-based complexometric titrations. Anal. Chem. 2015, 87 (24), 1231812323,  DOI: 10.1021/acs.analchem.5b03663
  23. 23
    Xie, X.; Bakker, E. Determination of effective stability constants of ion-carrier complexes in ion selective nanospheres with charged solvatochromic dyes. Anal. Chem. 2015, 87 (22), 1158711591,  DOI: 10.1021/acs.analchem.5b03526
  24. 24
    Leong, Y. K.; Lan, J. C.-W.; Loh, H.-S.; Ling, T. C.; Ooi, C. W.; Show, P. L. Thermoseparating aqueous two-phase systems: recent trends and mechanisms. J. Sep. Sci. 2016, 39 (4), 640647,  DOI: 10.1002/jssc.201500667
  25. 25
    Buschmann, H.-J.; Mutihac, L. Complexation, liquid-liquid extraction, and transport through a liquid membrane of protonated peptides using crown ethers. Anal. Chim. Acta 2002, 466, 101108,  DOI: 10.1016/S0003-2670(02)00513-5
  26. 26
    Wang, J.; Su, D.; Wang, D.; Ding, S.; Huang, C.; Huang, H.; Hu, X.; Wang, Z.; Li, S. Selective extraction of americium(III) over europium(III) with the pyridylpyrazole based tetradentate ligands: experimental and theoretical study. Inorg. Chem. 2015, 54, 1064810655,  DOI: 10.1021/acs.inorgchem.5b01452
  27. 27
    Soares, R. R. G.; Silva, D. F. C.; Fernandes, P.; Azevedo, A. M.; Chu, V.; Conde, J. P.; Aires-Barros, M. R. Miniaturization of aqueous two-phase extraction for biological applications: from micro-tubes to microchannels. Biotechnol. J. 2016, 11, 1498,  DOI: 10.1002/biot.201600356
  28. 28
    Tang, S.; Zhang, H.; Lee, H. K. Advances in sample extraction. Anal. Chem. 2016, 88, 228249,  DOI: 10.1021/acs.analchem.5b04040
  29. 29
    Sviben, I.; Galić, N.; Tomišić, V.; Frkanec, L. Extraction and complexation of alkali and alkaline earth metal cations by lower-rim calix[4]arene diethylene glycol amide derivatives. New J. Chem. 2015, 39, 60996107,  DOI: 10.1039/C5NJ00805K
  30. 30
    Elçin, S.; Deligöz, H. Synthesis and metal extraction studies of a novel chromogenic 5,17-bisazocalix[4]arenes. J. Inclusion Phenom. Macrocyclic Chem. 2014, 80 (3), 337343,  DOI: 10.1007/s10847-014-0408-4
  31. 31
    Nacham, O.; Clark, K. D.; Anderson, J. L. Extraction and purification of DNA from complex biological sample matrices using solid-phase microextraction coupled with real-time PCR. Anal. Chem. 2016, 88, 78137820,  DOI: 10.1021/acs.analchem.6b01861
  32. 32
    He, Q.; Zhang, Z.; Brewster, J. T.; Lynch, V. M.; Kim, S. K.; Sessler, J. L. Hemispherand-strapped calix[4]pyrrole: an ion-pair receptor for the recognition and extraction of lithium nitrite. J. Am. Chem. Soc. 2016, 138, 97799782,  DOI: 10.1021/jacs.6b05713
  33. 33
    Qin, Y.; Mi, Y.; Bakker, E. Determination of complex formation constants of 18 neutral alkali and alkaline earth metal ionophores in poly(vinyl chloride) sensing membranes plasticized with bis(2-ethylhexyl)sebacate and o-nitrophenyloctylether. Anal. Chim. Acta 2000, 421, 207220,  DOI: 10.1016/S0003-2670(00)01038-2
  34. 34
    Bakker, E.; Willer, M.; Lerchi, M.; Seiler, K.; Pretsch, E. Determination of complex formation constants of neutral cation-selective ionophores in solvent polymeric membranes. Anal. Chem. 1994, 66, 516521,  DOI: 10.1021/ac00076a016
  35. 35
    Bakker, E. Selectivity comparison of neutral carrier-based ion-selective optical and potentiometric sensing schemes. Anal. Chim. Acta 1997, 350, 329340,  DOI: 10.1016/S0003-2670(97)00218-3
  36. 36
    Wang, X.; Qin, Y.; Meyerhoff, M. E. Paper-based plasticizer-free sodium ion-selective sensor with camera phone as a detector. Chem. Commun. 2015, 51, 1517615179,  DOI: 10.1039/C5CC06770G
  37. 37
    Cantrell, K.; Erenas, M. M.; Orbe-Payá, I. d.; Capitán-Vallvey, L. F. Use of the hue parameter of the hue, saturation, value color space as a quantitative analytical parameter for bitonal optical sensors. Anal. Chem. 2010, 82 (2), 531542,  DOI: 10.1021/ac901753c

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  • Abstract

    Scheme 1

    Scheme 1. Working Principle of the Solvent Based Titration Reagentsa

    a(a) Before end point. (b) After end point.

    Figure 1

    Figure 1. Optical reverse titration curves (a, b, c) and corresponding absorption spectra (d, e, f) for K+, Na+, and Li+, respectively. Titrant: 10–2 M KCl or NaCl or LiCl. The dashed vertical lines indicate the expected end point. Buffer solution: 10–2 M Tris-HCl pH 7.0 for K+ titration; 10–2 M Tris-HCl pH 7.4 for Na+ and Li+ titration. Absorption spectra recorded at each titration point.

    Figure 2

    Figure 2. Response of the K+ (a), Na+ (b), and Li+ (c) selective reagents to various interfering ions, respectively. Buffer solution: (a)10–2 M Tris-HCl pH 7.0, (b,c) 10–2 M Tris-HCl pH 7.4. The horizontal distance between the calibration curve for primary ion and any interfering ions represents log K1.

    Figure 3

    Figure 3. Pictures of the K+ titration process after shaking (a) and after two phases separated (b) and the corresponding titration curves (c) and (d) based on the HSV analysis. The dashed vertical lines indicate the expected end points. Buffer solution: 10–2 M Tris-HCl pH 7.0.

    Figure 4

    Figure 4. Setup of the automated titration: (a) before titration, (b) after the end point. (c) Titration analysis for K+ based on the hue signals retrieved from the frames in the video. (d) Serum titration based on the hue signals retrieved from the frames in the video. Organic phase: K+ selective titration reagent. Aqueous phase: 10–2 M Tris-HCl pH 7.0 buffer solution. The volume of the added serum at the end point is Vserum = 73 μL.

  • References


    This article references 37 other publications.

    1. 1
      Yu, S. P.; Canzoniero, L. M.; Choi, D. W. Ion homeostasis and apoptosis. Curr. Opin. Cell Biol. 2001, 13, 405411,  DOI: 10.1016/S0955-0674(00)00228-3
    2. 2
      Kuo, H.-C.; Cheng, C.-F.; Clark, R. B.; Lin, J. J.-C.; Lin, J. L.-C.; Hoshijima, M.; Trân, V. T. B. N.; Gu, Y.; Ikeda, Y.; Chu, P.-H.; Giles, W. R.; Chien, K. R.; Ross, J. A defect in the Kv channel-interacting protein 2 (KChIP2) gene leads to a complete loss of Ito and confers susceptibility to ventricular tachycardia. Cell 2001, 107 (6), 801813,  DOI: 10.1016/S0092-8674(01)00588-8
    3. 3
      Krishna, G. G.; Miller, E.; Kapoor, S. Increased blood pressure during potassium depletion in normotensive men. N. Engl. J. Med. 1989, 320 (18), 11771182,  DOI: 10.1056/NEJM198905043201804
    4. 4
      Zhang, S.; Zhang, R.; Ma, B.; Qiu, J.; Li, J.; Sang, Y.; Liu, W.; Liu, H. Specific detection of potassium ion in serum by a modified G-Quadruplex method. RSC Adv. 2016, 6, 4199942007,  DOI: 10.1039/C6RA04046B
    5. 5
      Yang, L.; Qing, Z.; Liu, C.; Tang, Q.; Li, J.; Yang, S.; Zheng, J.; Yang, R.; Tan, W. Direct fluorescent detection of blood potassium by ion-selective formation of intermolecular G-Quadruplex and ligand binding. Anal. Chem. 2016, 88, 92859292,  DOI: 10.1021/acs.analchem.6b02667
    6. 6
      Harrington, J. M.; Young, D. J.; Essader, A. S.; Sumner, S. J.; Levine, K. E. Analysis of human serum and whole blood for mineral content by ICP-MS and ICP-OES: development of a mineralomics. Method. Biol. Trace Elem. Res. 2014, 160, 132142,  DOI: 10.1007/s12011-014-0033-5
    7. 7
      Chuang, F. S.; Sarbeck, J. R.; John, P. A. S.; Winefordner, J. D. Flame spectrometric determination of sodium, potassium and calcium in blood serum by measurement of microsamples. Microchim. Acta 1973, 61 (4), 523531,  DOI: 10.1007/BF01217998
    8. 8
      Buchberger, W. W. Detection techniques in ion chromatography of inorganic ions. TrAC. TrAC, Trends Anal. Chem. 2001, 20, 296303,  DOI: 10.1016/S0165-9936(01)00068-1
    9. 9
      Moody, G. J.; Saad, B. B.; Thomas, J. D. R. Studies on bis(crown ether)-based ion-selective electrodes for the potentiometric determination of sodium and potassium in serum. Analyst 1989, 114, 1520,  DOI: 10.1039/an9891400015
    10. 10
      Schwarzenbach, G.; Flaschka, H. Complexometric titrations; Methuen: London, 1969.
    11. 11
      Salvatore, M. M.; Salvatore, F. Understanding complexometric titrations of metal cations with aminopolycarboxylic acids (EDTA and analogs) within the frame of the notion of reactions between groups of chemical species. Word J. Chem. Educ. 2015, 3, 521,  DOI: 10.12691/wjce-3-1-2
    12. 12
      Roy, N.; Nath, S.; Dutta, A.; Mondal, P.; Paul, P. C.; Singh, T. S. A highly efficient and selective coumarin based fluorescent probe for colorimetric detection of Fe3+ and fluorescence dual sensing of Zn2+ and Cu2+. RSC Adv. 2016, 6, 6383763847,  DOI: 10.1039/C6RA12217E
    13. 13
      Karita, S.; Kaneta, T. Chelate titrations of Ca2+ and Mg2+ using microfluidic paper-based analytical devices. Anal. Chim. Acta 2016, 924, 6067,  DOI: 10.1016/j.aca.2016.04.019
    14. 14
      Bian, X.; Lockless, S. W. Preparation to minimize buffer mismatch in isothermal titration calorimetry experiments. Anal. Chem. 2016, 88 (10), 55495553,  DOI: 10.1021/acs.analchem.6b01319
    15. 15
      Afshar, M. G.; Crespo, G. A.; Bakker, E. Coulometric calcium pump for thin layer sample titrations. Anal. Chem. 2015, 87 (19), 1012510130,  DOI: 10.1021/acs.analchem.5b02856
    16. 16
      Chakma, B.; Jain, P.; Singh, N. K.; Goswami, P. Development of an indicator displacement based detection of malaria targeting HRP-II as biomarker for application in point-of-care settings. Anal. Chem. 2016, 88, 1031610321,  DOI: 10.1021/acs.analchem.6b03315
    17. 17
      Männel-Croisé, C.; Meister, C.; Zelder, F. ″Naked-Eye″ screening of metal-based chemosensors for biologically important anions. Inorg. Chem. 2010, 49 (22), 1022010222,  DOI: 10.1021/ic1015115
    18. 18
      Swain, B. Recovery and recycling of lithium: A review. Sep. Purif. Technol. 2017, 172, 388403,  DOI: 10.1016/j.seppur.2016.08.031
    19. 19
      Zhai, J.; Xie, X.; Bakker, E. Ionophore-based ion-exchange emulsions as novel class of complexometric titration reagents. Chem. Commun. 2014, 50, 1265912661,  DOI: 10.1039/C4CC05754F
    20. 20
      Zhai, J.; Xie, X.; Bakker, E. Ion-Selective optode nanospheres as heterogeneous indicator reagents in complexometric titrations. Anal. Chem. 2015, 87 (5), 28272831,  DOI: 10.1021/ac504213q
    21. 21
      Zhai, J.; Xie, X.; Bakker, E. Anion-exchange nanospheres as titration reagents for anionic analytes. Anal. Chem. 2015, 87 (16), 83478352,  DOI: 10.1021/acs.analchem.5b01530
    22. 22
      Zhai, J.; Xie, X.; Bakker, E. Solvatochromic dyes as pH-independent indicators for ionophore nanosphere-based complexometric titrations. Anal. Chem. 2015, 87 (24), 1231812323,  DOI: 10.1021/acs.analchem.5b03663
    23. 23
      Xie, X.; Bakker, E. Determination of effective stability constants of ion-carrier complexes in ion selective nanospheres with charged solvatochromic dyes. Anal. Chem. 2015, 87 (22), 1158711591,  DOI: 10.1021/acs.analchem.5b03526
    24. 24
      Leong, Y. K.; Lan, J. C.-W.; Loh, H.-S.; Ling, T. C.; Ooi, C. W.; Show, P. L. Thermoseparating aqueous two-phase systems: recent trends and mechanisms. J. Sep. Sci. 2016, 39 (4), 640647,  DOI: 10.1002/jssc.201500667
    25. 25
      Buschmann, H.-J.; Mutihac, L. Complexation, liquid-liquid extraction, and transport through a liquid membrane of protonated peptides using crown ethers. Anal. Chim. Acta 2002, 466, 101108,  DOI: 10.1016/S0003-2670(02)00513-5
    26. 26
      Wang, J.; Su, D.; Wang, D.; Ding, S.; Huang, C.; Huang, H.; Hu, X.; Wang, Z.; Li, S. Selective extraction of americium(III) over europium(III) with the pyridylpyrazole based tetradentate ligands: experimental and theoretical study. Inorg. Chem. 2015, 54, 1064810655,  DOI: 10.1021/acs.inorgchem.5b01452
    27. 27
      Soares, R. R. G.; Silva, D. F. C.; Fernandes, P.; Azevedo, A. M.; Chu, V.; Conde, J. P.; Aires-Barros, M. R. Miniaturization of aqueous two-phase extraction for biological applications: from micro-tubes to microchannels. Biotechnol. J. 2016, 11, 1498,  DOI: 10.1002/biot.201600356
    28. 28
      Tang, S.; Zhang, H.; Lee, H. K. Advances in sample extraction. Anal. Chem. 2016, 88, 228249,  DOI: 10.1021/acs.analchem.5b04040
    29. 29
      Sviben, I.; Galić, N.; Tomišić, V.; Frkanec, L. Extraction and complexation of alkali and alkaline earth metal cations by lower-rim calix[4]arene diethylene glycol amide derivatives. New J. Chem. 2015, 39, 60996107,  DOI: 10.1039/C5NJ00805K
    30. 30
      Elçin, S.; Deligöz, H. Synthesis and metal extraction studies of a novel chromogenic 5,17-bisazocalix[4]arenes. J. Inclusion Phenom. Macrocyclic Chem. 2014, 80 (3), 337343,  DOI: 10.1007/s10847-014-0408-4
    31. 31
      Nacham, O.; Clark, K. D.; Anderson, J. L. Extraction and purification of DNA from complex biological sample matrices using solid-phase microextraction coupled with real-time PCR. Anal. Chem. 2016, 88, 78137820,  DOI: 10.1021/acs.analchem.6b01861
    32. 32
      He, Q.; Zhang, Z.; Brewster, J. T.; Lynch, V. M.; Kim, S. K.; Sessler, J. L. Hemispherand-strapped calix[4]pyrrole: an ion-pair receptor for the recognition and extraction of lithium nitrite. J. Am. Chem. Soc. 2016, 138, 97799782,  DOI: 10.1021/jacs.6b05713
    33. 33
      Qin, Y.; Mi, Y.; Bakker, E. Determination of complex formation constants of 18 neutral alkali and alkaline earth metal ionophores in poly(vinyl chloride) sensing membranes plasticized with bis(2-ethylhexyl)sebacate and o-nitrophenyloctylether. Anal. Chim. Acta 2000, 421, 207220,  DOI: 10.1016/S0003-2670(00)01038-2
    34. 34
      Bakker, E.; Willer, M.; Lerchi, M.; Seiler, K.; Pretsch, E. Determination of complex formation constants of neutral cation-selective ionophores in solvent polymeric membranes. Anal. Chem. 1994, 66, 516521,  DOI: 10.1021/ac00076a016
    35. 35
      Bakker, E. Selectivity comparison of neutral carrier-based ion-selective optical and potentiometric sensing schemes. Anal. Chim. Acta 1997, 350, 329340,  DOI: 10.1016/S0003-2670(97)00218-3
    36. 36
      Wang, X.; Qin, Y.; Meyerhoff, M. E. Paper-based plasticizer-free sodium ion-selective sensor with camera phone as a detector. Chem. Commun. 2015, 51, 1517615179,  DOI: 10.1039/C5CC06770G
    37. 37
      Cantrell, K.; Erenas, M. M.; Orbe-Payá, I. d.; Capitán-Vallvey, L. F. Use of the hue parameter of the hue, saturation, value color space as a quantitative analytical parameter for bitonal optical sensors. Anal. Chem. 2010, 82 (2), 531542,  DOI: 10.1021/ac901753c
  • Supporting Information

    Supporting Information


    The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssensors.7b00165.

    • Detailed theoretical approach; additional results on optical reverse titration, experimental titration curve, and serum titration (PDF)

    • Automatic titration of potassium in human serum by using home-made setup (AVI)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.