KinTek Corporation, USA
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NEW SF-300X Stopped Flow

New SF-300X Stopped Flow

The new SF-300X stopped flow has a smaller footprint than its predecessor (the SF-2004) as well as a new user interface and added features with improved performance. The KinTek light source (standard with every SF-300X) now incorporates automatic wavelength selection and a programmable shutter that can be added to prevent photo bleaching on experiments with long collection times.

Servo Motor Drive System

The SF-300X Stopped-Flow has a powerful, computer-controlled servo motor drive that provides precise and reproducible mixing. Double mixing experiments can be performed easily while consuming minimal volumes of precious samples. The motor is digitally controlled with a high torque, low inertia, brushless motor and high performance, digital power supply to provide essentially instantaneous starts and stops of the drive syringes. A major advance over older stepper motor technology, the servomotor affords repeated or sequential mixing to be performed with precision and ease, completely under software control. The KinTek motor drive system provides the utmost in performance and reliability. Unlike air-drive instruments, the dead time does not depend on temperature of the solution or age of the syringes.
For ease of use and to help in the expulsion of air bubbles, the SF-300X stopped-flow uses a solid vertical drive mount. This arrangement places the sample syringes in a position where they are easy to load and to observe through the transparent water jacket during the course of an experiment. Various sample chambers can be easily interchanged or removed for cleaning.


Fluorescence - Absorbance Cells

The SF-300X stopped-flow instrument uses interchangeable observation cells. The user can select from a variety of cells to optimize data collection to meet special needs.  Each comes complete with syringe assembly and integral sample loading valve, so changing the observation cell is easy.

A choice of four observation cells is available and each provides not only optimal fluorescence measurements but also unique features, which can greatly improve data collection under different conditions. All four cells can record either absorbance or fluorescence or both simultaneously. An optional CCD array detector allows spectra to be recorded every millisecond for truly outstanding performance.

Dead Time for Mixing

KinTek SF-2004 Observation Cell

The new SF-300X stopped-flow is capable of producing a dead time of 0.85 millisecond. View the data! With its precision, high torque servo motor drive, the performance of the SF-300X is repeatable and reliable year after year. The SF-300X also has excellent performance reliability due to the precision manufacturing of all parts and with proper care will give many years of service. We use our proprietary microjet mixers to achieve efficient mixing. In both cases, test reactions have proven that mixing is completed in the KinTek SF-300X Stopped-Flow before the sample enters the cell.

Sample Loading Valve

A unique two-position valve is used to allow easy and efficient sample loading. In one position, the three syringes are connected to their individual sample load ports. In the other position, the three syringes can be driven to force the mixing of reactants into the observation cell. Optical sensors read the position of the sample load valve and tell the computer whether the valve is in the proper position for loading or firing. The computer will not fire a shot if the valve is in the wrong position. This safety feature further conserves precious samples.

Sample Volume

Designed to conserve precious samples, the KinTek SF-300X requires only 20 microliters of each reactant per shot. Moreover, by minimizing the volume of the sample lines connecting the loading ports to the sample syringes, the instrument requires a small load volume. Typically, only 50 microliters of reactant is wasted in loading each syringe.

Three Syringe - Double Mixing Experiments

The KinTek SF-300X Stopped-Flow comes with three drive syringes. In the normal mode of operation, only two syringes are connected and used to drive the mixing of two reactants. Alternately, the third syringe can be connected to perform a double mixing experiment. Two reactants are mixed and then flow into a delay line. The motor then stops for the desired reaction time and then on the next push the solution is mixed with the third reactant and forced into the observation cell. The reaction time is under precise computer control, allowing reactant times as short as 5 milliseconds and up to many minutes. Double mixing experiments allow new experiments to explore reaction mechanisms that cannot be accomplished with other commercially available instruments.

T-Format Fluorescence Anisotropy!

The SF-300X can be easily and economically equipped to perform fluorescence anisotropy measurements. A second optional PMT is added to the instrument along with an easy to use filter set and the instrument becomes an optimal anisotropy instrument. View the data!


KinTek SF-300X is noted for the ease of use and reliability of its software. Running under Windows 7, the SF-300X operating system utilizes menus to access all of the computer-controlled instrument setup, data collection, analysis and plotting. Data and computer-generated fits are displayed on the display and can be printed on any printer supported by Microsoft Windows. The SF-300X system software allows data to be easily exported to other programs in ASCII spreadsheet format — at the click of a mouse! Moreover, the data can be exported to the popular KinTek Explorer™ software for rigorous data fitting directly to the model, not to equations!

Computer Control

The KinTek SF-300X is entirely under computer control, making the operation of the instrument easy and convenient to use. The computer controls the instrument's drive system, the detector gain and checks to see that the sample load valve is in the right position. It is also programmed to assist in a simple calibration of the instrument. The instrument and software have been integrated into a system that is easy and convenient to use, leaving the operator free to concentrate on the data collection and analysis.

Data Collection and Analysis

KinTek Corporation is constantly upgrading the control computer and A/D converter to afford rapid data collection and analysis. Data fitting is accomplished within the data collection software by nonlinear regression. Data can be fit to one, two or three exponentials or to a burst equation. Data can also be fit by computer simulation to the reaction mechanism by global fitting methods using KinTek Global Kinetic Explorer™. Data can also be easily exported for import into the data fitting and graphics presentation program of your choice.

Computer Specifications: (as of 3/3/2014)

Keep in mind that KinTek Corporation is constantly upgrading the computer that controls the stopped-flow instrument. The instrument is shipped with the latest model computer available.

Light Source for Optimal Signal

KinTek SF-2004 light source

Optimal signal-to-noise is provided through several unique advances. A high intensity, stable arc lamp source illuminates the sample using a parabolic mirror and lens-free optics to provide optimal throughput to a monochromator. The optical path is free of lenses, which would limit light throughput. The electronic circuits have been designed to provide the most noise-free amplification possible.


Wavelength range: 220 - 800 nm.
Wavelength accuracy: 1 nm.
Stray light: less than 0.02%
Spectral bandwidth: : Multiple variable slit widths providing a bandwidth of 4 nm/mm of slit width.
Temperature range: 0 - 70° C range of temperature is maintained by circulating water bath (not provided).
Dead time: Less than 1 millisecond.
Syringe volume & range:2.5 ml standard, 0.25, 0.5, 1.0, and 5.0 also available.
Computer operating system: Windows 7
A/D Converter: 1.0 MHz, 16-bit, 6 channels

Physical Dimensions

Component Width × Depth × Height Weight
Stop-flow stand:
32 × 28 × 74 cm
17.5 kg
Motor controller
24 × 30 × 29 cm
9.0 kg
Light Source:
19 × 68 × 18 cm
9.0 kg
Lamp power supply:
14 × 30 × 19 cm
7.8 kg
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