In liquid chromatography, gradient eluent means the alteration of the solvent composition over the entire duration of the analysis.
Gradient elution is used for optimizing the separation as well as the analysis time of complex sample mixtures with the possibility of using high or low-pressure gradient systems.
With low-pressure gradient systems a pump with sution-side controlled solenoid valves is used. These valves open time-controlled and alternately the appropriate eluent channels. The single fractions are mixed by a dynamic mixer and delivered by the HPLC pump into the chromatography system. The advantage of the low-pressure gradient technique is the excellent resolution of the gradient, independently of the pump's flow rate. The degassing of the solvent is very important, as gas bubbles from not degassed eluents or gas bubbles caused by solvent contraction after mixing these eluents will affect the flow stability of the pump.
High-pressure gradient system means the use of one dosing pump for each solvent and performing the gradient profile by altering the flow rate of these pumps with a resulting constant volume delivery.
Diode Array Technology, Photoconductor Optics and Dual Lamp Source.
- Diode Array Technology for wavelength change without any mechanical moving parts.
- Simultaneous detection of up to 4 wavelengths with 4 separate analog signal outputs.
- Online scan of wavelength and collection of spectra data without stopping the flow or interrupting the running analysis.
- Dual lamp (deuterium/tungsten) for a spectral range of 190 - 720 nm.
- Integrated peak detector with programmable delay time.
- Integrated soolvent recycling system (3-way solenoid valve optionally).
- External START, external AUTOZERO via TTL-signal.
- Serial interface (RS232C) for external control.
- Programmable change of wavelength (up to 10 steps).
- Full DAD operation mode with ChromStar software (optional).
190 - 720 nm |
Deuterium + Tungsten |
+/- 0.5 nm |
+/- 0.1 nm |
< 3.0E-05 AU (254 nm) |
< 5.0E-05 AU / hour (after warmup) |
6 nm |
Wavelength changing (up to 10 steps) spectra data collection and replay (optional) |
1.0 V |
TTL: Autozero, Start Serial Interface (RS232C) |
220 x 150 x 350 mm |
7.8 kg |
115 / 220 V; 50 / 60 Hz |
10 31 002 |
UV/Vis Detector Model S 3240 |
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UV/Vis Detector Model S 3240DAD (full DAD mode) |
10 32 002 |
Standard Flow Cell (10 mm pathlength), stainless steel |
10 32 003 |
Standard Flow Cell (10 mm pathlength), PEEK |
10 32 004 |
Micro Flow Cell (3 mm pathlength), stainless steel |
10 32 005 |
Preparative Flow Cell (1.5 mm pathlength), stainless steel |
10 32 006 |
Preparative Flow Cell (1.5 mm pathlength), PEEK |
10 32 006 |
Preparative Flow Cell (2 mm pathlength), stainless steel |
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X-Y-Z operated sample injecting and sample processing system.
The system can be upgraded at any time from the basic version for fixed volume injection with sample loop overfilling, up to variable volume injection mode for variable volumes from 1 - 100 µl (optional up to 500 µl) without changing the sample loop.
With the next upgrading step, the S 5200 can be used for fully automatic sample processing fro pre-column derivatization. In the derivatisating mode, up to three independent reagents can be added to a specified sample volume, mixed with sample and programmed with independent reaction times. In addition, the sample can be diluted with more than 100 times (depending on sample volume and syringe volume).
For temperature sensitive samples, the sample tray can be cooled or heated with the optional cooling system.
For chemical inert operation, the instrument can be delivered for fully metal-free sample handling (completely equipped with PEEK and FEP materials, including sample needle).
A wide range of sample racks and sample vials can be used for operation from 1 µl up to 5000 µl or by using micro titer plates.
Simple operation through large alphanumeric display menu.
- Fixed volume mode (standard) with 20 µl sample loop
- Variable volume (1st grade option) 100 µl sample loop
- Sample processing (2nd grade option) 100 µl sample loop
Standard: 500 µl syringe stepper motor driven with a resolution of 35 steps/1 µl.
Optional:
- 100 µl Syringe (resolution: 175 steps/1 µl)
- 250 µl Syringe (resolution: 70 steps/1 µl)
- 1000 µl Syringe (resolution: 16 steps/1 µl)
- 2500 µl Syringe (resolution: 6 steps/1 µl)
- 5000 µl Syringe (resolution: 3 steps/1 µl)
- Fix: 1.0 to 9.9 times sample loop volume in 0.1 increments programmable
- Variable: 1 - 5000 µl in 1 µl increments
- 3 reagents each one 1 to 5000 µl independently programmable
- 3 reaction times independently programmable
- needle wash after each processing step programmable
- sample mixing after each processing step 1 - 9 times programmable
- up to 5000 µl diluting solvent in 1 µl increments can be added to sample volume
- mixing after diluting 1 - 9 times programmable
- through purge position or inject position selectable
- wash program for selecting needle wash activity and washing volume 1 - 9 times of the syringe volume
- less than 1% upon injection of 10 µl variable volume
- less than 0.5% upon 100 µl variable volume and fix volume injection
- less than 0.01% depending on selected wash program
- 1 to 9 different volumes programmable for each injection
- up to 9999 programmable time base selectable in 1 minutes, 0.1 minutes or in seconds
- standard: 2 pcs. for 60 vials each; total of 120 for 1.5 ml glass vials or for plastic conical Eppendorf types
- optional:
- preparative version: 2pcs. for 24 vials each; total of 48 for 5 ml glass vials
- micro titer plates holder
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The degassing of solvents is very important in liquid chromatography, as oxygen and other in the solvent dissolved gases affect the analysis for various reasons; through the volume contraction (gradient mixing), different pressure ratio (in front and behind the column) and caused by different temperatures, the dissolved gases are released in course of time. This will influence the reliability of the analysis (pump) as well as the detection efficiency (measuring cell). Therefore, dissolved gases have to be removed from the solvent.
The known methods are ultrasonic and batch vacuum processing, flushing of the solvent with a stream of helium and continuous vacuum degassing devices.
The ultrasonic method is suitable for degassing organic eluents but is not adequate enough for aqueous solutions. For these kind of solutions, the solvent has to be degassed in a suction bottle placed under vacuum. But both of these methods are only shortterm solutions as after the degassing process, the solvent wil be continuously enriched with gases taken from the air. Furthermore, for gradient elution, the degassing quality is not sufficient enough.
Continuously usable and quite simple to handle is the method of flushing the eluent with a stream of helium. Hereby, the stable remaining He-molecules are displacing all other gases. An equal maintained gas pressure buffer prevents the helium from escaping and gradient elutions can be carried out without any problems.
The same solvent quality is achieved with the usage of the vacuum degasser. The great advantage when using the vacuum degasser is, that no further costs concerning the supply and consumption of helium arise. Furthermore, for some analysis methods, e.g. detection in the lower UV range or with RI-detection, the vacuum degassing method allows an operation with lowest possible detection limits due to more smooth and stable base line conditions.
In a vacuum chamber, the solvent to be degassed is distributed into several, parallel arranged, semi-permeable membrane chambers. When a high vacuum (more than -850 mbar) is applied, only the in the liquid dissolved gases are diffusing through the thin membrane. With a total solvent volume of 8 ml per degassing channel, the Sykam Degasser S 7510 achieves an extremely low remaining gas concentration of 0.5 to 5 ppm oxygen, depending on the degasser's flow rate (0 to 10 ml/min). With a given flow rate, the degassing quality can be further increased by coupling two or several membrane channels.
The digital display of the actual vacuum in Milibar makes the Sykam Degasser S 7510 the first vacuum degasser on the market which functions can be checked and documented at any time.
On top of that, the actual vacuum run can be continuously registered via an analogue DC output (-1 V for 1000 mbar). Through in integrated logic, any leakage in the vacuum system is detected (run time of the vacuum pump for defined vacuum range) and is not only optically displayed by a controll LED but is also indicated through a relay contact closure for peripheral systems. For removing possibly existing solvent traces, the vacuum pump's waste gases can be directed via a fixable tube connection to the laboratory's ventilation. The Teflon membrane packages are exchangable, in case of damage.
with an applied vacuum, dissolved gases are continuously removed through a semi-permeable membrane |
max. 10 ml/min. for each degassing channel |
0.5 ppm oxygen at 0.5 ml/min. |
PTFE and PEEK |
8 ml |
0 - 999 mbar |
0 - 1 V for 0 - 999 mbar |
visually over LED and through neutral relay contact |
220 / 110 V; 50 / 60 Hz |
110 x 150 x 350 mm |
5.6 kg |
10 71 001 |
Sykam Degasser S 7510 (2-Channel) |
10 71 002 |
Sykam Degasser S 7510 (3-Channel) |
10 71 003 |
Sykam Degasser S 7510 (4-Channel) |