Summary Attribute of OLIS RSM 1000 Systems

Designed and patented in the early 1990s for stopped-flow spectrophotometry, the RSM is the name given to a Rapid Scanning Monochromator capable of 1000 scans per second. Additional acquisition rates include 1000 points per half millisecond for microsecond kinetics (e.g., laser/ flash photolysis) and ‘normal, slow’ scanning.

Spectrophotometers designed around this monochromator have unique and highly desirable characteristics for kinetic studies as well as highest sensitivity measurements.  The designed-in and easily implemented modularity allows one optical bench to fulfill the functions of multiple spectrophotometers.

1. The monochromator is a subtractive double grating monochromator with all associated desirable characteristics (homogeneous output beam, zero temporal dispersion, and more)

2. Millisecond scanning is achieved by means of a moving intermediate slit, an aperture moving in space.

3. Milliabsorbance sensitivity is easily achieved during these millisecond spectral scans. The holmium oxide filter scan shown here is a one millisecond scan.

4. Microsecond acquisition is achieved using a fixed position intermediate slit. Shown is the capture of a one microsecond LED flash.

5. All electronics and detection are optimized for highest speed, highest sensitivity work.

6. The scan rate of 1,000 scans/second is continuous. The instrument is not scanning only when turned off. 

7. During data acquisition periods, the software is capturing true dual beam (sample-reference) readings at a rate of 1,000 scans per second.

8. Scans are 230 nm in breadth for 1 nm spectral resolution. For higher resolution, the breadth must be narrowed to 75 nm. For wider spans to 500 nm, resolution broadens. 

9. The spectral range of the monochromator is determined by a pair of 50 x 50 mm holographically blazed gratings. The number of lines per millimeter and the blaze wavelength are chosen for the experimental case at hand. Gratings are easily accessed and exchanged between measurements for optimization within the UV, Visible, and NIR spectral ranges. 

10. During both conventional speed scanning and millisecond spectral scanning, "dark" readings are made between every scan, such that correct readings can be made even on samples with fortuitous fluorescence induced by the (absorbance) measuring beam.

11. The 1000 scans per second must be signal averaged to a lesser number during data collection periods longer than 8 seconds. Signal averaging is available at 60 scans per second, 30, 10, 5, 2 and 1 scan per second are available. 

12. For microsecond work, the moving intermediate slit motorization is turned off.

13. Microsecond acquisition is achieved at a rate to 1,000 points per 500 microseconds. 

14. For non-kinetic studies, the instrument operates as a normal scanning Uv/Vis.

  15. Detection in all UV/Vis modes is by photomultiplier tubes; detection in the NIR is with InGaAs detectors.

   16. Detectors are easily accessed and exchangeable for optimization for response time, gain settings, and spectral ranges.  

  17. The spectrophotometer's sample compartment supports use of water jacketed cuvettes, Peltier cells, cryogenic flasks, magnets, stopped-flow mixing system, and/or other sample holders either directly or with available customization.

  18. The double grating monochromator is a "subtractive," which differs from the more common "additive" in producing a homogeneous output beam, particularly desirable when non-homogeneous samples such as solids, crystals, films, powders, and other heterogeneous samples are studied.

  19. As a pre-dispersive monochromator system, the spectrophotometer does not cause photolysis on even photolabile samples such as vitamins or visual pigments, since the sample sees only rapidly varying monochromatic light during the measurement. And, the measuring beam can be blocked from reaching the sample between measurements with a manual or computerized shutter.

  20. No optical components move during rapid-scanning. All rapid-scanning is achieved by a moving aperture in the midplane of the double monochromator. Thus, during millisecond spectral scanning, the only moving component in the instrument is a thin metal disk with 16 radially dispersed slits (apertures) being spun by a synchronous motor at 62.5 Hz.

  21. The intermediate slit can be one of three types: ScanDisk for 1,000 scans per second, StepDisk for 100 scans per second, or Fixed Slit. 

  22. When the ScanDisk or StepDisk is used, gratings are moved to the appropriate middle wavelength for the upcoming scan and then fixed in position.

  23. When the Fixed Slit cartridge is used, gratings are moved in the normal way to cause scanning.

  24. The ScanDisk is used for stopped-flow; the StepDisk is used for CLARiTY, and the Fixed Slit is used for microsecond fixed wavelength and conventional speed scanning.

  25. The spectrophotometer is fitted with a 75-watt xenon arc lamp when configured for absorbance spectroscopy. For fluorescence or CD, a 150-watt xenon arc lamp is standard.

  26. All components are mounted for precise positioning and perfect alignment on custom optical plates, rendering the components easily accessible and removable to support the modularity needed to realize luminescence, fluorescence emission and excitation, anisotropy, circular and linear dichroism, optical rotary dispersion, and variations on a theme, all on one optical bench.

  27. An optional computer-controlled shutter for protection of photolabile samples between measurements can also be opened and closed quickly, effectively producing an "actinic flash" from an otherwise steady-state measuring beam.

  28. All electronics to control the optical bench and accessories are external to the spectrophotometer, rendering diagnosis and repair as simple and economical as possible. Only the free-standing box needs be returned to OLIS if the repair must be done by Olis personnel; otherwise, the box can be opened by laboratory personnel under OLIS direction to access and repair/ replace any faulty power supply, amplifier, or circuitry.

  29. All software for collecting and analyzing data as a function of wavelength, time, temperature, concentration, and other processes is provided as part of the comprehensive OLIS SpectralWorks software package.

  30. The software supports signal averaging during rapid-scanning, effectively slowing acquisition while losing none of the photons (1000, 62, 31, 15, 10, 5, 2, or 1 scan/ second) and thereby also allowing for longer experiments.

  31. The 3D data analysis software includes the "Simplex Method," a linear fitting procedure which is applicable to linear and non-linear problems using linear optimization of the parameters until some convergence criterion is met. (The Simplex Method differs from the widely known and widely used Levenberg-Marquardt and Gauss-Newton methods in that it does not use derivatives of the function with respect to the parameters, and thus, is much less prone to find false minima.) In addition, the software includes the exact "Matrix Exponential Solution" method in kinetic analysis, which is markedly more precise than numerical integration methods and which does not have Runga-Kutta's stiffness.

  32. The software includes data compression algorithms which reduce the size of the raw data files by 40-fold while losing none of the information in the data files.

  33. The software includes Singular Value Decomposition ("SVD") to calculate the number of components which caused the data and to reduce random noise by three-fold.

  34. The software supports a dynamic, interactive 3D display of the data for graphical interpretation of the kinetic process.

  35. The software supports extraction of kinetics from any wavelength.

  36. The software supports ASCII file creation of any selected scans or kinetic traces; large 3D file storage is binary.

  37. The controlling computer is a Win 10 3 GHz processor or faster.

38. The software is Windows 10 with fast, modern, menu-driven features to support all instrument control, data analysis, data presentation, and data storage and handling. Export to Excel or comma delimited ASCII is single click for both single and multiple scans data

Optional Accessory, stopped-flow detail summary: 

1. The stopped-flow provides anaerobic performance with gas purging (for oxygen binding) available in three positions.

2. The stopped-flow has ceramic valve blocks for durability against all corrosive solutions, temperature ranges, and gas exchange. The novel development is unique to OLIS and has significant consequences for the robustness and longevity of the flow system, rendering it imperious to abuse which renders other stopped-flows useless.

3. The stopped-flow has a deadtime of approximately one or two milliseconds, adjustable to longer times.

4. The stopped-flow is fitted with five sensors to provide 100% security against misfiring, premixing, and damage to the hardware and operator. Feedback from these sensors will come from both the trigger box (LED display) and/or OLIS control software. This novel advance is unique to Olis and has significant consequences for the security of the hardware and the operator.

5. The stopped-flow uses syringes from 0.5 to 5 mL, matched or mixed, so that 1:1 up to 1:11 mixing can be achieved (unit will be delivered with one pair of 2.5 mL syringe unless prior arrangements are made).

6. The stopped-flow is useable over a temperature range of 10°C to 100°C, extendible with additional hardware to -30°C.

7. The stopped-flow is pneumatically driven for reliable performance, even when solutions of different viscosities are used.

8. The stopped-flow is useable with an optional Auxiliary Mixer for preparation of an unstable A + B mixture that will subsequently be one of the reagents used during stopped-flow.

9. The stopped-flow mixing apparatus remove easily from the Olis RSM 1000, so that the Olis RSM 1000 can be used as a research grade scanning absorbance, fluorescence, or circular dichroism spectrophotometer when stopped-flow mixing is not required.

Optional Configuration, use as a CD spectrometer:

1. The Olis method of "Digital Subtractive Method" ("DSM") is for the direct acquisition of absolute CD results. "DSM" detection is exclusive to OLIS and is the means to directly collect (not calculate) circular dichroism ("CD").

2. The DSM CD spectrophotometer requires no calibration, since CD data are acquired by definition (CD = abs(L) -abs(R)), instead of as a ratio of decoupled AC and DC intensities multiplied by a calibration constant.

3. Use of the CD spectrophotometer does not presume any prior knowledge about the sample by the operator, as there are no amplitude, sensitivity, or time constant settings to make prior to scanning the sample.

4. The resulting CD spectrophotometer supports variable data collection rates such that each datum is acquired over the exact length of time necessary to reach a user specified noise level. Using this optional variable data collection rate feature ensures that the best data are obtained in the least amount of time, saving time, nitrogen, and the need for repetitive scanning.

5. The resulting CD spectrophotometer provides useful light to 167 nm, with scanning to 450 nm standard and scanning extendible to 800, 1100, 1700, or 2600 nm without optical realignment or use of tools.

6. The CD spectrophotometer uses a dual beam phase coherent detection system, in which 100% of the light from the lamp is used, providing 100% more light for the measurement than a single beam, "modulation method" CD spectrometer.

7. The CD spectrophotometer supports read rates of 1000 readings per second in dual (or single) beam mode. Scan rates up to 200 nm/minute are supported in both dual (or single) absorbance and dual (or single) CD.

8. The CD spectrophotometer supports the option of rapid-scanning to rates of 62 CD scans per second.

9. The CD spectrophotometer is a dual beam, double monochromator based instrument which is fully usable as a research grade dual beam absorbance spectrophotometer.

10. The CD spectrophotometer supports the simultaneous detection of CD/2 with absorbance from 1 cm² and microvolume cells, as well as option of single beam fluorescence emission (photon counting) concurrent with CD and CD/2 detection.

11. The CD spectrophotometer sample compartment includes up to three jacketed cuvette holders, one for cylindrical and rectangular dual beam CD cuvette use and two for 1 cm² and microvolume single beam CD and dual beam absorbance cuvette use. Alternatively, and at higher cost, the CD spectrophotometer sample compartment can be fitted with a single thermoelectric heating/ cooling Peltier cells for electronic temperature ramping.

12. The CD spectrophotometer is installed with software for collecting and analyzing data as a function of wavelength, time, concentration, and/or temperature (3D global analysis, as well as 2D fits). This software uses the modern and correct methods of SVD, Downhill Simplex, and Matrix Exponentiation for fitting of changing ('kinetic') and non-changing ("equilibrium") samples.