An embodiment provides a method for measuring an alkalinity of an aqueous sample, including: introducing an aqueous sample to a voltammetric pH electrode; holding the potential of a voltammetric pH electrode at a pH end point potential; applying a voltage step waveform comprising at least one potential pulse to the voltammetric pH electrode; titrating the aqueous sample; and measuring a current output resulting from the voltage step waveform, wherein the measuring comprises square wave amperometry. Other aspects are described and claimed.

An embodiment provides a method for measuring a characteristic of an aqueous sample, including: introducing the aqueous sample to a titration region and a reaction region of a measurement device, wherein the titration region comprises a pH electrode and a protonator electrode contacting a first portion of an aqueous sample, wherein the reaction region comprises a counter electrode contacting a second portion of the aqueous sample; placing an electrolyte reservoir in a state of electrical continuity with the titration region and the reaction region, wherein the electrolyte reservoir comprises a reference electrode, wherein the volume of the electrolyte reservoir comprises a large volume of an electrolyte; and determining a characteristic of the aqueous sample by measuring an electrochemical characteristic between the reference electrode and at least one of: the pH electrode and the counter electrode. Other aspects are described and claimed.

An embodiment provides a method for measuring an alkalinity of an aqueous sample, including: introducing an aqueous sample to a voltammetric pH electrode; holding the potential of a voltammetric pH electrode at a pH end point potential; applying a voltage step waveform comprising at least one potential pulse to the voltammetric pH electrode; titrating the aqueous sample; and measuring a current output resulting from the voltage step waveform, wherein the measuring comprises square wave amperometry. Other aspects are described and claimed.

An embodiment provides a method for deriving an alkalinity measurement, including: introducing a fluid sample; measuring, a phosphate amount of the fluid sample using a colorimetric reagent; measuring a pH of the fluid sample, wherein the pH of the fluid sample correlates to a hydroxide amount of the fluid sample; introducing an acid to convert all the inorganic carbon to carbon dioxide; applying a positive potential to the SP3 substituted carbon electrode; introducing, prior to or substantially simultaneously during the application of the positive potential to the SP3 substituted carbon electrode and in the reaction chamber, at least one acid reagent comprising a metallic catalyst that converts the carbonate and the partially oxidized species to carbon dioxide; determining total organic carbon by detecting an amount of carbon dioxide produced by the oxidation; determining the total organic carbon from the oxidation of the organic carbon species, and determining a derived alkalinity based upon the phosphate amount, the hydroxide amount, and the amount of carbon dioxide generated from the inorganic carbon. Other aspects are described and claimed.

An embodiment provides a method for determining the alkalinity of an aqueous sample using an alkalinity sensor, including: monitoring the pH of an aqueous sample using a pH sensor in a sample cell, the pH sensor including a pH sensor electrode made of boron-doped diamond; generating hydronium ions, using a hydronium generator, in the aqueous sample in the sample cell, the hydronium generator including a hydronium-generating electrode; changing the pH of the aqueous sample by causing the hydronium generator to generate an amount of hydronium ions in the aqueous sample; quantifying and converting a current or charge to the number of hydronium ions produced to an end point of the electrochemical titration, the end point correlating to the alkalinity of a sample; and analyzing the alkalinity of the aqueous sample based on the generated amount of hydronium ions and the resulting change in pH monitored by the pH sensor.

An embodiment provides a method for determining the alkalinity of an aqueous sample using an alkalinity sensor, including: monitoring the pH of an aqueous sample using a pH sensor in a sample cell, the pH sensor including a pH sensor electrode made of boron-doped diamond; generating hydronium ions, using a hydronium generator, in the aqueous sample in the sample cell, the hydronium generator including a hydronium-generating electrode; changing the pH of the aqueous sample by causing the hydronium generator to generate an amount of hydronium ions in the aqueous sample; quantifying and converting a current or charge to the number of hydronium ions produced to an end point of the electrochemical titration, the end point correlating to the alkalinity of a sample; and analyzing the alkalinity of the aqueous sample based on the generated amount of hydronium ions and the resulting change in pH monitored by the pH sensor.

The invention generally relates to electrophoretic mass spectrometry probes and systems and methods of uses thereof. In certain aspects, the invention provides a mass spectrometry probe having a hollow body with a distal tip, an electrically conductive hollow conduit, and an electrode. The electrically conductive hollow conduit may be operably coupled to a reservoir and a power source, and the electrically conductive hollow conduit may be configured to transport a liquid sample into the hollow body and polarize the liquid sample as it flows through the electrically conductive hollow conduit and into in the hollow body. The electrode and the electrically conductive hollow conduit are disposed within the hollow body (e.g., at different heights within the hollow body).

Methods, systems and devices that generate differential axial transport in a fluidic device having at least one fluidic sample separation flow channel and at least one ESI emitter in communication with the at least one sample separation flow channel. In response to the generated differential axial transport, the at least one target analyte contained in a sample reservoir in communication with the sample separation channel is selectively transported to the at least one ESI emitter while inhibiting transport of contaminant materials contained in the sample reservoir toward the at least one ESI emitter thereby preferentially directing analyte molecules out of the at least one ESI emitter. The methods, systems and devices are particularly suitable for use with a mass spectrometer.

Provided are methods for producing a separation medium, where the method includes exposing a separation medium precursor solution to light from a light source through a photomask that includes a region with varied light transmittance to produce the separation medium. Systems that find use in performing the methods, microfluidic devices that include the separation medium, as well as methods of using the microfluidic devices, are also provided. Embodiments of the present disclosure find use in a variety of different applications, including detecting whether an analyte is present in a fluid sample.

An apparatus with a transducer having a first output signal and arranged to receive an electrical input. The transducer switches the first output signal between an ON and OFF state. The apparatus has a chemical sensing surface coupled to the transducer arranged to receive a chemical input. A signal generator oscillates one or more of said inputs to vary the switching point of the transducer. The oscillating input may be the chemical input and/or the electrical input. The output signal may be a pulse whose period ON or OFF is determined by the oscillating input modulated by the chemical input.