Reagent Flow Rate Research Articles

Chemical Modification of Insulin Using Flow Chemistry.

Chemical modification of proteins is of growing importance to generate new molecular probes for chemical biology and for the development of new biopharmaceuticals. For example, two approved, long-acting insulin variants are lipidated at the LysB29 side-chain. Acylations of proteins have so far been performed in batch-mode. Here we describe the use of flow chemistry for site-selective acylation of a small protein, insulin. To the best of our knowledge this is the first report on flow chemistry for chemical modification of insulin. The first step was to develop reaction conditions for acylation of Lys B29 that gave a soluble mixture and thus was compatible with flow chemistry in a microreactor; this included selection of a soluble base. Secondly, the conditions, such as reagent ratios and flow rate were optimized. Third, the use of these conditions for the acylation with a wide range of acids was demonstrated. Finally, Boc-protected insulins were synthesized. Insulin remained stable towards these flow chemistry conditions. This use of flow chemistry for the chemical modification of insulin opens the prospect of producing chemically modified biopharmaceuticals by flow chemistry with fewer byproducts.

Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode

The paper presents the research results of the supercritical water oxidation (SCWO) of poultry manure continuously fed into a tubular reactor both in the absence and presence of methane as an auxiliary fuel. The tests were conducted at a temperature gradient along the vertical axis of the reactor (top to bottom: 390–600 °C), a pressure of 25 MPa, and varying reagent flow rates. It is shown that due to heat generation during methane oxidation the energy consumption from external sources is reduced by 1.3–1.5 times depending on the ratio of reagent flow rates. The gas products contain CO2, N2, and trace amounts of N2O. The ash residues are predominantly composed of calcite and hydroxyapatite. The addition of methane results in a reduction in the content of phenols and polycyclic aromatic hydrocarbons present in the aqueous effluent, while content of N-bearing aromatics increases. The formation of nitrophenols was observed at elevated oxygen concentrations in the reaction mixture. It was revealed that excess oxygen plays a pivotal role in the efficacy of organic nitrogen removal. The formation of mineral acids and a high level of ammonia in the reaction mixture during the SCWO of poultry manure result in corrosion of stainless steel and copper seals, which in turn leads to an increased concentration of chromium and copper in the aqueous effluent. The results obtained indicate the potential for utilizing natural gas in an environmentally friendly and resource-saving manner for poultry manure processing by SCWO in autothermal mode.

Flow injection analysis system with smart phone for the determination of total phenolic compounds in wastewater using Folin Ciocalteu reagent

Smart phones are playing a big role in daily life and are being employed as supporting hardware in a variety of chemical analysis applications. flow injection analysis method for the rapid, simple, and straightforward determination of total phenols using Folin-Cioclteu reagent .The sample or standard solutions were injection into a carrier stream to react with reagent and detected by spectrophotometer at 765 nm . The experimental conditions such as flow rate of reagent and carrier ,reagent volume ,length of reaction coil and concentration of reagent were optimized .A good linear calibration curve in the range of (250-2000 mg L-1 ) was obtained with regression equation ( y=0.0123 x + 0.1857) ,( R= 0.999 ), the limit of detection was in the amount of ( 0.0102 mg L-1) .The method was successfully applied for the determination of the total phenols in wastewater .

Winery and olive mill wastewaters treatment using nitrilotriacetic acid/UV-C/Fenton process: Batch and semi-continuous mode

In this work, both red and white winery wastewaters (WW) and olive mill wastewater (OMW) were submitted to a treatment by Fenton-based processes (FBPs). The main aim was to evaluate the most efficient and economic process. Initial tests, resorting to a batch reactor, demonstrated that UV-C/Fenton (λ = 254 nm) was the most effective process. Operational conditions such as pH, H2O2 and Fe2+ concentrations revealed to have a superior influence within dissolved organic carbon (DOC) removal as well as regarding the reactor's energy consumption. As a means to prevent iron precipitation, the addition of nitrilotriacetic acid (NTA) was tested. With experimental conditions pH = 3.0, [H2O2] = 194 mM, [Fe2+] = 1.0 mM, [NTA] = 1.0 mM, radiation UV-C (254 nm), time = 240 min, the kinetic rate related with DOC removal showed a kredWW = 0.0128 min−1 > kOMW = 0.0124 min−1 > kwhiteWW = 0.0104 min−1 and both the WW and OMW achieved the Portuguese legal limit values for wastewater discharge. Furthermore, comparative experiments were performed in a semi-continuous reactor, being that the results put in evidence that the concentration of H2O2 added and the flow rate of reagents' addition (F) had a significant effect on the efficiency of the reactor. Under an optimum experimental procedure pH = 3.0, [H2O2] = 97 mM, [Fe2+] = 1.0 mM, [NTA] = 1.0 mM, radiation UV-C (254 nm), F = 1 mL min−1, time = 240 min, there were observed higher DOC removal kinetic rates (kOMW = 15.20 × 10−3 min−1 > kredWW = 11.64 × 10−3 min−1 > kwhiteWW = 11.57 × 10−3 min−1) and a cost ranging between 0.0402 and 0.0419 €/g.DOC. These results showed that semi-continuous reactors have the potential to be applied to large scale treatments, with low reagents consumption and reduced energy requirements.

EVALUATION OF THE INFLUENCE OF MIXER ROTATION THROUGH COMPUTATIONAL FLUID DYNAMICS SIMULATION OF A CONTINUOUS STIRRED-TANK REACTOR FOR BIODIESEL PRODUCTION FROM EXPERIMENTAL KINETIC DATA

In the present work, a computer simulation was performed through computational fluid dynamics (CFD) for a Continuous Stirred-Tank Reactor, starting from experimental data on the kinetics of the transesterification reaction between soybean oil methyl acetate, using an enzyme as a catalyst, the Candida Antartica. A volume was proposed for the reactor so that the average residence time of the reaction mixture was sufficient for the expected yield, based on the data obtained by the Matlab®, was obtained at the exit of the reactor. The simulation of the reactor operation was of a continuous process with constant reagents flow rates made using commercial software ANSYS®. The impeller chosen was of the type inclined straight blades, the simulations were made by varying the rotation speed of the mixer where an increase in reaction yield was observed until the rotation of 120 RPM, above this speed, no real gain was observed in the amount of biodiesel obtained.

Microfluidic device-based synthesis of highly monodispersed dumbbell-shaped gold nanorods and their biocompatibility evaluation

Anisotropic gold nanomaterials have always fascinated the scientific community; however, controlling their synthesis to achieve desired properties and monodispersity is challenging in a conventional batch reactor. Here, we report the synthesis of highly monodispersed dumbbell-shaped gold nanorods (Ds-Au NRs) in a droplet microfluidic device. The device comprises a tapered T-junction for reagent droplet production, a winding structure to promote nucleation, and lengthy parallel microchannels to support the slow growth required for dumbbell shape morphology. After optimising the flow parameters and device geometry for uniform droplet production, the aspect ratio of Ds-Au NRs was tuned by controlling the total reagent flow rate, reagent flow rate ratio, and concentration of shaping reagent and reducing agent. Compared to batch counterparts, reaction time was reduced to one-fifth and revealed higher monodispersity. The cytotoxicity analysis showed that microfluidic synthesised Ds-Au NRs are non-toxic and have great potential for usage in biomedical applications.

Emergence of Power-Law Particle Size Distribution in Microfluidic Calcium Carbonate Precipitation: An Extended Yule Process with a Ripening Effect.

Precipitation of calcium carbonate in bulk solutions is well known to result in a bell-shaped or bimodal particle size distribution. However, it is unclear how the distribution behaves if precipitation occurs in a small, confined volume. In this Letter, we conduct microfluidic experiments where sodium carbonate and calcium chloride solutions are continuously injected into a microchannel to precipitate calcium carbonate particles. Results show that, regardless of the variations in reagent concentrations, mixing schemes, flow rates, and precipitation time, sizes of precipitated particles in the channel are power law distributed, with an exponent of 1.4. The data are described by an extended Yule process with the introduction of a ripening term. Since the Yule process is a general mechanism for power law generation, the extended Yule process proposed here provides a general model for systems where growth and ripening simultaneously present.

Gold recovery from pregnant thiosulfate solution by ion exchange resin: Synergistic desorption behaviors and mechanisms

The behaviors and mechanisms of gold desorption from its loading resin with the mixed solution of Na2SO3 and NaCl were studied. The desorbent displayed evident “synergistic role” on the gold desorption and had good desorption performance over wide ranges of reagent concentration, flow rate and gold loading amount. Based on the thermodynamic analysis, a two-step desorption mechanism was proposed: (1) SO32– reacted with [Au(S2O3)2]3– to generate [Au(S2O3)(SO3)]3–; (2) The resin had weak affinity for the two-ligand gold complex which was thus replaced by Cl– readily. SEM-EDS, characteristic color of gold complex, Raman spectra and binding energy calculation results indicated SO32– could react with [Au(S2O3)2]3– to form [Au(S2O3)(SO3)]3–, and the affinity of the resin for the newly-generated complex was weaker than that for Cl–, which demonstrated the above mechanism. The mechanism model of gold recovery from pregnant thiosulfate solution by ion exchange resin was finally constructed.

Semi – Automation Design Using Flow Injection Analysis System with Smart Phone for the Determination of Total Phenols in Wastewater

Smart phone used as supporting hardware in different applications in chemical analysis are becoming increasingly important in everyday life. Rapid, easy, and straightforward analytical system flow injection analysis system for the determination of the total phenols was conducted using 4-aminoantipyrine reagent. The detection method was based on the reaction total phenols with reagent in the basic media and subsequent formation of a yellow color product. The samples or standard solutions were injection into a carrier stream to react with 4-aminoantipyrine reagent and ammonium chloride with ammonium hydroxide to give yellow color product, which was detected by spectrophotometer at 510 nm. The experimental condition such as flow rate of reagent and carrier, reagent volume, length of reaction coil and concentration of reagent were optimized. A good linear calibration curve in the range of 250-2000 mg L-1 was obtained with regression equation (y=0.0108 x + 0.3453), (R= 0.9989). The limit of detection was in the amount of 0.0112 mg L-1. The method was successfully applied for the determination of the total phenols in wastewater.

Surface plasmon resonance tunable gold nanostar synthesis in a symmetric flow-focusing droplet device

Gold nanomaterials are known for their unique optical properties due to their localized surface plasmon resonance (LSPR). Controllable gold nanomaterials synthesis to tune LSPR of specific application demands is of great interest in the scientific community and is technically challenging to achieve in a conventional batch reactor. In this work, we tailored LSPR tunable gold nanostars (Au NS) using a symmetric flow-focusing droplet device after optimizing the flow parameters in 2D simulations. Simulations were used to represent the fluid interface within the device microchannels and helped to study the droplet evolution and their quantification. As nanomaterials synthesis in a droplet device demands the production of homogenous droplets and control over their size and production rate, we optimized the flow parameters from the simulation. By incorporating curved, sinusoidal geometries and semi-spiral microchannels, the mixing of reagents inside the droplet was improved for synthesizing heavily branched Au NS. The best performance was achieved when the flow rate of the shaping reagent was twice that of other reagents. As-synthesized Au NS are non-toxic, uniform and possess a small core diameter, large tip-to-tip length, negative surface zeta potential and red-shifted LSPR. These features are highly favourable for photothermal and photodynamic applications. Thus, our microfluidic platform can produce uniform droplets that provide sufficient mixing of reagents for the application-specific LSPR tunable synthesis of gold nanostars.

Development, characterization, and applications of a portable analyzer for continuous monitoring of H2S in gas streams

A bench-scale analyzer for continuous monitoring of H2S in gas streams was previously described (2012 Sens. Actuators B 162 377–83). The analyzer was based on the exothermic reaction between the scrubbed H2S, in alkaline solution, with hydrogen peroxide. The analyzer offers several advantages but suffers from a relatively slow response time (i.e. 7 min) and a relatively low sensitivity (limit of detection = 100 ppm). In the present work, a substantially improved detector design and direct mixing of the gas with the liquid reagents are described. The improved detector, in the form of a coiled thin-walled stainless-steel (SS) tube also acts as a compartment for direct gas absorption and reaction with sodium hydroxide and hydrogen peroxide reagents, which eliminates the need for a gas scrubber based on microporous hollow fiber membranes (HFMs). The average temperature of the SS coil was measured by three thermocouples attached to the outer surface of the coil with thermally conductive epoxy. The improved detector design and the simplified scheme proved very successful in achieving six times faster response (i.e. 70 s) and ten times more sensitive response (i.e. 10 ppm) in the gas stream and improved repeatability (coefficient of variation = 0.55%). In addition, the previously reported advantages, such as excellent signal stability, wide dynamic range (up to 5% H2S) and convenient tuning of the sensitivity and linearity by varying the ratio between the gas and reagent flow rates were perfectly retained. The improved detector is utilized to construct a compact portable version of the H2S analyzer (∼6 kg), which provides a stand-alone operation for real-time monitoring of H2S in the gas stream for up to 4 h prior to the need for reagent refill or battery recharge. The applications of the described portable analyzer in monitoring H2S removal from H2S–N2 gas stream using an HFM contactor and absorption solvent, and in the determination of sulfide ions in liquid samples are presented. A comparison between the response of the present portable H2S analyzer and a commercial analyzer is also presented.

Composite Structured M/Ce0.75Zr0.25O2/Al2O3/FeCrAl (M = Pt, Rh, and Ru) Catalysts for Propane and n-Butane Reforming to Syngas.

Here, we report the preparation, characterization, and performance of reforming propane and n-butane into a syngas of composite structured M/Ce0.75Zr0.25O2/Al2O3/FeCrAl (M = 0.46 wt.% Pt, 0.24 wt.% Rh, and 0.24 wt.% Ru) catalysts. The catalysts are composed of a high-heat-conducting FeCrAl block with preset geometry, with a surface nearly totally covered by θ-Al2O3. Afterwards, a layer of ceria–zirconia mixed oxide was deposited. The formed oxide coating was used as a support for 2–3 nm sized Pt, Rh, or Ru nanoparticles. The performance of the catalysts in propane steam reforming decreased in the order of Rh ≈ Ru > Pt. The reformates obtained in the propane steam reforming over Rh- and Ru/Ce0.75Zr0.25O2/Al2O3/FeCrAl at 600 °C and GHSV = 8300 h−1 contained 65.2 and 62.4 vol.% of H2, respectively, and can be used as a fuel for solid oxide fuel cells. In the oxidative steam reforming of propane at 700 °C and GHSV= 17,000 h−1, the activities of the Rh- and Pt-based catalysts were similar and the compositions of the outlet gas mixtures were quite close to equilibrium in both cases. Increasing the reagent flow rate to 25,600 h−1 showed stability of the Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl performance, whereas the Pt/Ce0.75Zr0.25O2/Al2O3/FeCrAl activity decreased. A mathematical model considering the velocity field, mass balance, pressure, and temperature distribution, as well as the reaction kinetics, was suggested for the propane steam and oxidative steam reforming over the Pt- and Rh/Ce0.75Zr0.25O2/Al2O3/FeCrAl catalysts. The model well described the experimental results.

Development of Sequential Injection Analysis for the Determination of Lead in Vegetables

A sequential injection analysis incorporated with spectrophotometric method was developed for determination of lead, based on reaction of dithizone with lead producing pink complex and absorbance of the complex was measured at 515 nm. The analytical parameters of the system were optimized by univariate method such as reagent concentration, fl ow rate of reagent and injection volume. Linear calibration curve over the range of 0.02-0.08 mg L-1 and 0.1-2.0 mg L-1 lead was obtained. The detection limit of lead was 0.012 mg L-1. The relative standard deviations for fi ve replicate injections was 0.77-1.54% for intra-day and 0.86-1.80% for inter-day. The recovery of 98.75-101.20% was achieved with sample throughput of 45 samples per hour. The proposed method has been applied to the determination of lead in vegetable samples. The obtained results were in good agreement with those obtained by the ICP-MS standard method, verifi ed by the student t-test at the 95% confi dence level.

Photocatalytic activation of peroxymonosulfate using ilmenite (FeTiO3) for Enterococcus faecalis inactivation

In this work, a raw and low cost mineral, ilmenite (FeTiO3), has been tested for the first time as a photocatalyst paired with peroxymonosulfate (HSO5-; PMS) for the inactivation of Enterococcus faecalis as an alternative to conventional treatments to disinfect wastewater for reuse. The influence of some operational parameters such as reagent dosage, catalyst concentration, initial pH, or flow rate was also studied and optimized. After several tests, the scarce pure photoactivity under UV-A was remarked by ilmenite because of its high iron content, which favors photogenerated charge recombination. However, ilmenite activity was highly promoted when combined with low concentrations of PMS and UV-A light, reaching total inactivation of Enterococcus faecalis in 120 min. Quenching tests were performed using methanol, tert-butyl alcohol, furfuryl alcohol, and Cu(II) to assess the main reactive species involved in the disinfection process determining the critical role of both HO·and SO4·- radicals in the process. Finally, the influence of the water matrix was also evaluated by studying the effect of water hardness and the presence of nutrients on the system. Overall, the PMS/Ilmenite/UV-A system yielded promising results with a total removal of Enterococcus faecalis in 120 min. However, it also showed the need for further study and understanding of the disinfection mechanism to achieve the same level of performance in real wastewater.

Optimization of the continuous coprecipitation in a microfluidic reactor: Cu-based catalysts for CO2 hydrogenation into methanol

CuO-ZnO-ZrO2 catalysts were synthetized by controlled continuous coprecipitation in a microfluidic reactor. CuO, ZnO and ZrO2 contents in catalysts were kept constant at 37.5 wt% of CuO (corresponding to 30% Cu0), 41.0 wt% of ZnO and 21.5 wt% of ZrO2. Numerous parameters of the continuous microfluidic coprecipitation, such as the nature of the carrier fluid, the residence time in the microfluidic synthesis reactor, the reagents flow rates during the synthesis and the pH, were studied in order to obtain perfectly homogeneous catalytic materials. All catalysts were characterized and then tested in methanol synthesis via CO2 hydrogenation on the REALCAT platform using high-throughput experiments. The optimum catalytic results were obtained for the catalyst synthesized by the continuous coprecipitation in a microfluidic reactor at following controlled parameters: water as carrier fluid, 30 s of residence time, low total reagent flowrate of 35 µL min−1 and pH equal to 8. This catalyst presented a good CO2 conversion of 21.4 % along with a methanol selectivity of 33 %, leading to a record methanol productivity of 1135 gMeOH kgcat-1 h−1 at 280 °C, 50 bar and a GHSV of 25,000 h−1 (STP).

Determination of the Quantity of Losartan Active Ingredient in the Medication Formulations via Turbidimetric-Flow Injection Technique

This study describes a rapid and sensitive method for determination of Losartan potassium (LOS-K) in pure and medication forms. The method is depended upon the reaction of LOS-K with Silicotungestic acid in salt medium for the formation of a white precipitate. The new precipitate was monitored and measured using homemade Ayah 6SXI-T-2D Solar cell analyzer in combination with a continuous flow injection technique. Reagent concentration, acid medium, flow rate, sample volume, purge time, and delay coil reaction are all chemical and physical characteristics that have been investigated and optimized. The linear dynamic range of LOS-K was 0.05-2 mMol/L with linearity percentage (r2%) 99.56 %. Limit of detection (LOD) was 3.62 µg/sample and LOQ=18.28 µg/sample. A comparison between developed method and classical methods (UV-Spectrophotometry at λmax= 232 nm) was made. The proposed method was successfully applied for determination of LOS-K in the pharmaceutical samples and can be used as an alternative method.

New sensitive turbidimetric method for determination of losartan potassium in pharmaceutical formulations using flow injection combined with homemade turbidimeter

This paper is describing a rapid and sensitive method for determination of Losartan potassium (LOS-K) in pure and drug forms. The method is based on the reaction of LOS-K with potassium hexacyanoferrate (III) in acidic medium to form a yellow precipitate. The precipitated product was monitoring and measurements using homemade (Ayah 6Sx1-T-2D solar cell) analyzer that combined with a continuous flow injection technique. Chemical and physical factors such as reagent concentration, acid medium, flow rate, sample volume, purge duration, and delay coil reaction were investigated and optimized. The linear dynamic range of LOS-K was 0.1-2 mmol/L with linearity percentage (r2%) 98.41%. Limit of detection (LOD) at a minimum concentration in the calibration graph was 5.8 µg/sample and limit of quantitation was LOQ=38.3 µg/sample. A comparison of developed method with reference methods (UV-Spectrophotometry at λmax= 232) was also made. These results indicate that the proposed method- which was successfully applied for determination of LOS-K in the pharmaceutical samples, can be used as an alternative for classical methods.

Characterizing Multidevice Capillary Vibrating Sharp-Edge Spray Ionization for In-Droplet Hydrogen/Deuterium Exchange to Enhance Compound Identification.

Multidevice capillary vibrating sharp-edge spray ionization (cVSSI) source parameters have been examined to determine their effects on conducting in-droplet hydrogen/deuterium exchange (HDX) experiments. Control experiments using select compounds indicate that the observed differences in mass spectral isotopic distributions obtained upon initiation of HDX result primarily from solution-phase reactions as opposed to gas-phase exchange. Preliminary studies have determined that robust HDX can only be achieved with the application of same-polarity voltage to both the analyte and the deuterium oxide reagent (D2O) cVSSI devices. Additionally, a similar HDX reactivity dependence on the voltage applied to the D2O device for various analytes is observed. Analyte and reagent flow experiments show that, for the multidevice cVSSI setup employed, there is a nonlinear dependence on the D2O reagent flow rate; increasing the D2O reagent flow by 100% results in only an ∼10–20% increase in deuterium incorporation for this setup. Instantaneous (subsecond) response times have been demonstrated in the initiation or termination of HDX, which is achieved by turning on or off the reagent cVSSI device piezoelectric transducer. The ability to distinguish isomeric species by in-droplet HDX is presented. Finally, a demonstration of a three-component cVSSI device setup to perform multiple (successive or in combination) in-droplet chemistries to enhance compound ionization and identification is presented and a hypothetical metabolomics workflow consisting of successive multidevice activation is briefly discussed.

Strategy for fast manufacturing of 3D hydrodynamic focusing multilayer microfluidic chips and its application for flow-based synthesis of gold nanoparticles

Fabrication of 3D microfluidic devices is normally quite expensive and tedious. A strategy was established to rapidly and effectively produce multilayer 3D microfluidic chips which are made of two layers of poly(methyl methacrylate) (PMMA) sheets and three layers of double-sided pressure sensitive adhesive (PSA) tapes. The channel structures were cut in each layer by cutting plotter before assembly. The structured channels were covered by a PMMA sheet on top and a PMMA carrier which contained threads to connect with tubing. A large variety of PMMA slides and PSA tapes can easily be designed and cut with the help of a cutting plotter. The microfluidic chip was manually assembled by a simple lamination process.The complete fabrication process from device design concept to working device can be completed in minutes without the need of expensive equipment such as laser, thermal lamination, and cleanroom. This rapid frabrication method was applied for design of a 3D hydrodynamic focusing device for synthesis of gold nanoparticles (AuNPs) as proof-of-concept. The fouling of AuNPs was prevented by means of a sheath flow. Different parameters such as flow rate and concentration of reagents were controlled to achieve AuNPs of various sizes. The sheet-based fabrication method offers a possibility to create complex microfluidic devices in a rapid, cheap and easy way.

One-step enzyme kinetics measurement in 3D printed microfluidics devices based on a high-performance single vibrating sharp-tip mixer

Measuring enzyme kinetics is of great importance to understand many biological processes and improve biosensing and industrial applications. Conventional methods of measuring enzyme kinetics require to prepare a series of solutions with different substrate concentrations and measure the signal response over time with these solutions, leading to tedious sample preparation steps, high reagents/sample consumption, and difficulties in studying fast enzyme kinetics. Here we report a one-step assay to measure enzyme kinetics using a 3D-printed microfluidic device, which eliminates the steps of preparing and handling multiple solutions thereby simplifying the whole workflow significantly. The assay is enabled by a highly efficient vibrating sharp-tip mixing method that can mix multiple streams of fluids with minimal mixing length (∼300 μm) and time (as low as 3 ms), and a wide range of working flow rates from 1.5 μL/min to 750 μL/min. Owing to the high performance of the mixer, a series of experiments with different substrate concentrations are performed by simply adjusting the flow rates of reagents loaded from three inlets in one experiment run. The Michaelis-Menten kinetics of the horseradish peroxidase (HRP)-catalyzed reaction between H2O2 and amplex red is measured in this system. The calculated Michaelis constant is consistent with the values from literature and conventional analysis methods. Due to the simplicity in fabrication and operation, rapid analysis, low power consumption (1.4–45.0 mW), and high temporal resolution, this method will significantly facilitate enzyme kinetics measurement, and offers great potential for optimizing enzyme based biosensing experiments and probing many biochemical processes.