SX20 Stopped-Flow Spectrometer - Specifications
Specifications
Description
The SX20 is purpose designed for high performance stopped-flow research. The standard system provides single mixing, absorbance and fluorescence (or light scattering) detection, scanning capability in steady-state and kinetic modes, all of outstanding sensitivity. It features a biocompatible and fully thermostated flow circuit and supports large ratio asymmetric mixing. Data acquisition, display and analysis is provided by our Pro-Data software running under Windows™ XP. Pro-Data provides an integrated and easy to use environment with flexible and powerful functionality for a wide range of stopped-flow kinetics applications. A comprehensive range of upgrade options are also available.
General information
- Measurement modes: Absorbance, Fluorescence, Fluorescence Polarisation/Anisotropy, Dual Fluorescence, Sequential Mixing, Quench-Flow. Optimised for both absorbance and fluorescence detection without the need for reconfiguration.
- Ultra stable Xenon lamp power supply with built-in 'SafeStart' igniter.
- 150W Air cooled xenon lamp housing fitted with either a low noise ozone-free Xenon lamp or ozone-producing Xenon lamp.
- Programmable monochromator enabling acquisition of equilibrium absorbance spectra and multi-wavelength kinetic data sets.
- Sample handling unit fitted with removable cell cartridges. The standard 20µL volume cell has a dead-time of 1.1ms, optical pathlengths of 10mm and 2mm, and is suitable for absorbance and fluorescence work. A shorter dead-time 5µL cell can also be fitted.
- Flow circuit materials are suitable for anaerobic experiments and resistant to aggressive reagents.
- Very wide temperature range (+60°C to -20°C).
- Minimum sample volume requirement of 40µL per syringe.
- Nine-stage side window absorption photomultiplier (Range 140 – 850nm).
- Eleven-stage end window emission photomultiplier (Range 280 – 650nm). Alternative tubes are available if extended wavelength ranges are required.
- Pro-Data Windows® XP™ control software with comprehensive acquisition, display and analysis tools. Standard features include: wavelength scanning, repeat drives for signal averaging, acquisition of time-resolved spectra (SpectraKinetic technique), linear, logarithmic and split timebase and digital oversampling capability.
- Flat-screen monitor and network ready PC.
- The SX20 stopped-flow spectrometer requires the following environmental conditions:
- Operating temperature: +5°C to +35°C
- Operating Humidity: 20% to 80% non condensing
- Storage temperature: -20°C to +50°C
- Storage Humidity: 5% to 80% non condensing
Instrument Overview
Light Source
| Type | 150W Xe arc or 150W Hg-Xe arc | ||
| Ignition | “Safe-Start” – lower RFI | ||
| Stability - short term (up to 200ms) | <0.001AU (peak-to-peak) | ||
| Stability – medium term (1s to 10s) | <0.001AU (peak-to-peak) | ||
| Stability – long term (10s to 1000s) | ~0.001AU (peak-to-peak) | ||
| Light source warmup - %max. intensity | 95% after 0.5hr; 98% after 1.0hr | ||
| 30min drift (after 1 hour operation) | <1% |
The light source comprises a high stability, power controlled lamp supply which is used to drive a 150W short arc lamp mounted in convection cooled housing. The combination of this high specification power supply and short arc lamp provides excellent stability over all data acquisition periods. These performance characteristics allow a single light source to be used for UV/Vis absorbance studies as well as for fluorescence excitation.
The standard instrument is supplied with a xenon “ozone-free” lamp which is a useful general purpose lamp. For enhanced operation alternative lamps can be fitted: a 150W xenon with spectrosil envelope (ozone-producing) will enable emission in the far-UV wavelength region (below 240nm) and a 150W mercury-xenon offers strong emission lines at specific wavelengths that can be of interest for specific fluorescence excitation applications.
Lamp ignition is via a novel “SafeStart” built-in igniter which minimizes RFI during lamp ignition and thereby ensuring that there is no possibility of damage to sensitive electronic equipment in the vicinity of the lamp.
Monochromator
| Optical layout | Symmetrical Czerny-Turner | ||
| Dispersive medium | Diffraction grating | ||
| Slits | Bilateral – infinitely variable up to 5mm | ||
| Dispersion | 4.65nm/mm | ||
| Minimum wavelength step | 0.1nm | ||
| Rate of change when setting to new wavelength | 1500nm/min | ||
| Standard wavelength range (detector limited) | 200nm to 850nm |
The programmable f/3.4 grating monochromator (Czerny-Turner optical configuration) has continuously variable bi-lateral slits and is supplied with a 1200 l/mm holographic grating (alternative gratings can be fitted). The monochromator is fitted with a stepper motor drive and wavelength selection is controlled from the workstation. Light output from the monochromator is coupled to the cell cartridge of the stopped-flow sample handling unit via a high quality spectrosil light guide.
Sample Handling Unit
| Number of view ports | Two transmission/emission; One dedicated emission | ||
| Cell volume (standard cell) | 20µL | ||
| Optical path (transmission) | 2mm and 10mm | ||
| Cell volume (optional cell) | 5µL | ||
| Optical path (transmission) | 1mm and 5mm | ||
| Dead time (standard cell) | 1.1ms (1:1 mix) 1.6ms (10:1 mix) | ||
| Maximum final reagent flow rate | 18.5mL/ms (1:1 mix) | ||
| Typical reagent volume per shot | 50µL of each reagent (1:1 mix) | ||
| Drive ratios using appropriate syringes | 1:1; 2.5:1; 5:1; 10:1; 25:1 | ||
| Drive mechanism | Pneumatic drive for fast response with automatic sample empty (multiple shots) | ||
| Sequential mixing operations | |||
| Age time range | 15ms to > 1000s (continuously variable) | ||
| Age time selection | Directly from control software (no hardware reconfiguration required) | ||
| Calculated dead time | Recorded with each drive | ||
| Calculated age time | Recorded with each drive | ||
| Drive profiles | Recorded with each drive | ||
| Drive volumes | Recorded with each drive | ||
The drive syringes, flow lines and optical cell are surrounded by a thermostat bath. The flow circuit is chemically inert and free of stainless steel and rubber. It is constructed of glass (syringe barrels), silica (optical detection cell), PEEK (sample flow circuit tubing and drive valves) and Teflon (syringe piston seals). A supply of compressed gas, usually nitrogen or air (8 bar pressure), is required to operate the rams.
Electronics & Software
| Data acquisition resolution | 16 bit | ||
| Data input range | +10V to –10V | ||
| Maximum digitization range | 100kHz | ||
| Acquisition period – timebase 1 | From 5ms to 360000s | ||
| Acquisition period – timebase 2 | From 1.25ms to 10000s | ||
| Logarithmic acquisition period | From 1ms to 10000s | ||
| Data oversampling | 100kHz data sampling on linear timebases, variable on log timebase | ||
| Auto-range | Automatic optimisation of range settings |
The Electronics Unit provides automated control of the sample handling unit and monochromator wavelength setting plus signal acquisition from the photomultiplier tube detectors and data processing. The modular design of the SX20 electronics means only required features need be installed and in the unlikely event of a fault, these are localised, readily identified and if necessary can be quickly and easily repaired by substitution of the appropriate module.
PC Workstation
The SX20 features a Hewlett Packard PC fitted with a fiber-optic interface card that is linked to the Electronics Unit of the SX20 to provide computer control of the instrument via the SX20 Pro-Data Control Software.
SX20 - the ultimate gold standard in stopped-flow
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