REPRODUCIBLE LIQUID JUNCTION POTENTIALS: THE FLOWING JUNCTION.<sup>1</sup>

Lamb, Arthur B.; Larson, Alfred T.

doi:10.1021/ja01447a004

Cited by 25 publications

(12 citation statements)

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“…Figure 8 shows the dramatically reduced response time of the present device compared to that of the glass electrode. We conjecture that the rapid response was accomplished not only by the fast response of the pH-FET sensor itself, but also the positive effect of the flowing junction [ 4 , 8 , 10 ]. The pH-FET used in this work is a catheter-tip type [ 21 ] with a gate region covered with a pH-sensitive layer of Ta 2 O 5 and a material enabling a response time of less than 100 ms [ 22 ].…”

Section: Discussionmentioning

confidence: 99%

“…The KCl solution used in the reference electrode keeps the electromotive force of the Ag/AgCl electrode constant [ 4 , 7 ]. LJ devices based on several principles have been developed, including a ceramic type, double junction type, free diffusion junction type, and flowing junction type [ 4 , 6 , 8 , 9 , 10 ]. The first three types mentioned can be used in combination with electrodes [ 6 , 8 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…LJ devices based on several principles have been developed, including a ceramic type, double junction type, free diffusion junction type, and flowing junction type [ 4 , 6 , 8 , 9 , 10 ]. The first three types mentioned can be used in combination with electrodes [ 6 , 8 , 11 ]. While the fourth type, the flowing LJ, obtains stable measurement conditions due to the flow of the solution, the outer body is too large to fit into a practical measurement apparatus [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

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A Microfluidic pH Measurement Device with a Flowing Liquid Junction

Yamada

Suzuki

2017

Sensors

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The pH values of aqueous solutions are conventionally measured with pH-sensitive electrodes such as glass electrodes or ion-sensitive field-effect transistors (ISFETs) used in conjunction with Ag/AgCl reference electrodes and KCl solutions. The speed of pH measurement with these systems can be deficient, however, as the glass electrode responds slowly during measurements of sample solutions with low buffering capacities. Our group has constructed a new pH measurement system using a microfluidic device and ISFET sensors. The device has a channel with two inlets and one outlet, with a junction connected to a Y-shaped channel on the same plane. Two ISFET sensors and an Ag/AgCl pseudo reference electrode are fitted into the channel to construct a differential measurement device. A sample solution and baseline solution supplied into the inlets by gravity-driven pumps form a flowing liquid junction during measurement. The small size and fast response of the ISFET sensors enable measurement of about 2.0 mL of sample solution over a measurement period of 120 s. The 90% response time is within 2 s. The calibrated sensor signal exhibits a wide range (pH 1.68–10.0) of linearity with a correlation factor of 0.9997. The measurement error for all solutions tested, including diluted solutions, was 0.0343 ± 0.0974 pH (average error ± standard deviation (S.D.), n = 42). The new device developed in this research will serve as an innovative technology in the field of potentiometry.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Microfluidic pH Measurement Device with a Flowing Liquid Junction

Yamada

Suzuki

2017

Sensors

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“…The formation of an electrical potential at the interface of two fluids that have different ionic compositions, the liquid junction potential (LJP), is a phenomenon that has been well studied experimentally and theoretically since the late 1800's [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Methods of predicting the magnitude of the liquid junction potential as well as ways to compensate for it have been developed [1,9,13,14,[17][18][19].…”

Section: The Liquid Junction Potentialmentioning

confidence: 99%

“…In this instance, the pH sensitivity of fluorescein mandates a significant buffer concentration in the low conductivity solution, thereby requiring a prohibitively high concentration of added salt in the high conductivity stream. However, it is well known that the magnitude of the junction potential depends only on the ratio of ionic strengths [1,[6][7][8][9]23] of the two solutions. Because the sodium salt form of the buffering compound was used, adding one molar salt to one of the streams leads to a concentration ratio of approximately 7700.…”

Section: Potential Applicationsmentioning

confidence: 99%

Passive electrophoresis in microchannels using liquid junction potentials

2002

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The formation of the liquid junction potential (LJP) is a well-studied phenomenon that occurs in the presence of ionic concentration gradients. Although the LJP has been well characterized, its impact has generally been overlooked in microfluidic applications. The characteristics of flow in microfluidic channels cause this phenomenon to be particularly important, both as a source of deviation from anticipated results and as a tool capable of being harnessed to perform useful tasks. It is demonstrated that LJPs formed in microchannels can induce appreciable electrophoretic transport of charged species without the use of electrodes or an external power supply. This process is demonstrated in an H-filter (an H-shaped microfluidic channel used to bring two fluids into contact allowing extraction of diffusing species from one stream to another) by generating junction potentials between two flowing streams containing different concentrations of strong electrolytes and observing the mass transport of the charged dye fluorescein between those streams. It is shown that the LJP can be controlled to either accelerate or decelerate mass transport across a fluid interface in the absence of an interposed membrane. A preliminary mathematical description of the phenomena is offered to support the hypothesis that the observed mass transport is a result of the LJP. Possible practical microfluidic applications of electrophoretic transport without electrodes are discussed.

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