Diffuse Reflectance Accessory (external) Note: This document is also available in PDF format for improved print quality. PDF files are stored in the "\Manuals" folder on the Help & Videos CD-ROM.
• • • • • • • • • Operation o Routine DRA installation o Removing the DRA from the instrument o Collecting baseline scans o 8°/h Reflectance Factor Measurements (Comparison Method) o 8°/d Reflectance Factor Measurements (Comparison Method) o 8°/h Reflectance Factor Measurements (Single Beam Mode) o 0°/h Transmission Measurements (Comparison Method) o 0°/d Transmission Measurements (Comparison Method) o Variable Angle Reflectance Measurements (Center-Mount Sample Holder) o Absorbance Measurements (Cuvett
Introduction The traditional use of the spectrophotometer is to measure the absorbance or transmission of a clear or translucent liquid or solid. Typically UV/VIS/NIR spectroscopy applications include reaction kinetics, quantitative analysis or the identification of the chemical constituents in a substance.
exhibits NIR performance that is superior to traditional coatings(1), whilst maintaining UV-Vis performance. Warning If the DRA is not used in the manner specified by the manufacturer, the protection provided by the accessory may be impaired. Theory Reflection consists of two components: specular and diffuse. Specular reflectance is the mirror-like reflection off a sample surface. Diffuse reflectance occurs when the surface reflects light in many different directions, giving the surface a matt finish.
integrating sphere usually depends on the wavelength capabilities demanded by the reflectance application. The integrating sphere configuration offers some distinct advantages over the standard sample compartment.
Transmittance measurements Figure 4: Collection of scattered light by an integrating sphere. Io = incident light, Is = scattered light. In order to perform useful measurements on scattering samples, it is necessary to collect a high proportion of the scattered radiation. The integrating sphere is a highly efficient collector of scattered radiation.
Factors affecting accuracy or precision Below are the major factors that may affect the accuracy of measurements when using the DRA. Aperture area/total surface area ratio Some of the reflected light escapes through the ports. This has the effect of reducing the signal to noise ratio, and thus the precision of the measurement. The Commission Internationale de l’ Eclairage (CIE) recommendation is a ratio of <10%. This figure is < 10% for the Cary External DRA.
Sample recess Theory assumes that the sample is placed coincident with the inside of the sphere wall, however the sample is placed against the outside of the sphere wall. The porthole edges have a finite thickness, and some part of the beam reflected at wide angles may be intercepted by the sphere wall. Figure 6: Some of the wide-angle reflection is intercepted by the sphere wall The edges of the reflectance port are feathered to reduce this error.
Differences between the standard and sample It is important that the reference material be of a similar reflectivity and have similar properties to the sample. Otherwise large errors can be introduced, if for example a poorly reflecting material is measured relative to a highly reflective PTFE reference plate. The table below lists the appropriate reference materials that are recommended for use.
Description of the accessory Accessory design The DRA accessories are designed specifically to measure the reflectance or transmission of solids, liquids, powders, or other small objects that can fit at the transmission or sample reflectance ports. Except for the sphere detectors, the construction of each version of the DRA is identical. Basic components of the accessory include the base plate, integrating sphere, optics chamber and detector chamber. The basic components are illustrated in the figure below.
Figure 10: The optical design of the external DRA. Integrating sphere An integrating sphere is an optical device used to collect and measure electromagnetic radiation. The radiation sampled by the DRA integrating sphere is provided by the spectrophotometer reference and sample beams present inside the sample compartment. Upon entering the sphere, the light strikes the sample surface and the highly reflective walls of the cavity, undergoing many diffuse reflections.
Optics The optics chamber houses the transfer optics of the DRA accessory that direct the spectrophotometer reference and sample beams to their respective ports on the integrating sphere. The sample beam is the rear beam in the accessory. Mirrors labelled M1, M2 and M3 guide the sample beam through the sample transmission port of the integrating sphere and onto the sample reflectance port at an 8° angle of incidence.
Figure 13: Mirror M2. Figure 14: Mirror M3. Mirror M3 is a spherical mirror that condenses the sample beam onto the target sample. The mirror can be mounted at any of three different positions on the base plate of the DRA. These positions correspond to the transmission port, centre mount sample holder and sample reflectance port, and are labelled "T", "C" and "R" respectively.
Figure 15: Mirror M4. The accessory is shipped from in a protective wooden case. The accessory should be stored in the case when the DRA is not being used. Detector The detector chamber attaches to the bottom of the base plate and is located directly underneath the integrating sphere. Reflectance standards The DRA is shipped with three Spectralon reflectance standards. If a standard is calibrated, a calibration certificate that lists the reflectance data across the wavelength spectrum will be included.
data in the comma separated variable format (.CSV) and paste the file into the Scan data directory. Consult the online help for more details. Transmission sample holder The external DRA accessory uses either a clasp-style or cuvette-style sample holder that fits over the dovetail mount at the transmission port of the integrating sphere. The claspstyle device, shown below, is best suited for solid samples large enough to completely fill the transmission port.
Purge gas connections Clean flexible tubing of 6 mm (1/4") inside diameter (Tygon PVC or equivalent). Size packed W x L x H, 500 mm x 840 mm x 470 mm Size unpacked W x L x H, 330 mm x 660 mm x 300 mm Weight packed 35 kg Weight unpacked 12 kg * Thermoelectrically cooled. # The optional small spot kit, with the aperture kit, permits the measurement of samples down to approximately 5mm. The accessory is suitable for indoor use only. Suitable for Installation Category I and Pollution Degree 2.
Item Description Part number 3 x Uncalibrated PTFE Three PTFE plates for collecting baselines and XXXX reference plates performing calibrations. 1 x Accessory cover (installed) XXXX 2 x Magnetic sample port covers (installed) Magnetic covers for the reflectance and reference ports. XXXX 1 x Light seal/guillotine I metal plate to seal the join between the DRA and the sample compartment. XXXX 1 x Lockdown pin Metal pin to hold DRA into place.
1. Unpack M3 and screw it into the "R" position. Set the mirror alignment pins into the correct locator holes and secure the mount with the mounting screw. Refer to figure 19. 2. Remove the accessory cover. Figure 16. Removing the accessory cover. 3. Remove the light seal/guillotine. Figure 17. Removing the light seal. 4. Remove the magnetized covers from the reference and reflectance ports. 5. Install the centre mount port plug into the top of the sphere. Refer to figure 19. 6.
7. Use the "T" handle and the corner (marked "Lift Here") to lift the DRA out of the box. See figure 18. Warning The accessory is heavy (32.5 kg). Safe lifting procedures should be used. When the accessory is in its box, two people are required to do the lifting. There is a handle at each end of the box to assist in the lifting. Figure 18. Lift the DRA from the wooden packing case as shown. One hand on the "T" handle, the other under the corner marked "Lift here".
will induce optical scattering and may reduce reflectance or transmission of these components at certain wavelengths. 1. Turn off the spectrophotometer and remove any cell holders or other accessories from the sample compartment (the PC can be left on). 2. Turn the power to the spectrophotometer on and allow time for the instrument to warm up (about two hours). 3. Fully open the sample compartment lid and remove the front panel. 4.
Figure 20. Install the specular port plug. 7. Remove the accessory from the wooden container by lifting the accessory by the "T" handle and the corner marked "Lift Here". Figure 21. Lift the DRA from the wooden packing case as shown. One hand on the "T" handle, the other under the corner marked "Lift here". 8. Slide the DRA into the sample compartment at a 20° angle.
9. Take care to align the metal edges of the DRA with the guide tabs on the edge of the instrument sample compartment. This will correctly align and engage the rear lockdown pins into the the sample compartment floor. The following two photos illustrate how to line up the tabs, note inparticular the red circle indicating where the tabs should sit. Figure 22. Align the tabs on the DRA with those on the instrument sample compartment.
Figure 23. Place the front lock down pin into position. 10. Place the front lockdown pin into the hole in the DRA floor next to the "T" handle. 11. Gently manoeuvre the DRA until the pin falls into place. 12. Flick the lockdown lever on the front instrument panel to the left. Do not connect the accessory cable to the instrument. Caution The spectrophotometer must be turned off before plugging in the DRA, or serious damage may result. 13. Install the light seal. 14.
Figure 24. The sample holder fits onto the dovetail at either the reference or reflectance port. 16. Install the transmission sample holder at the transmission port, it should slide easily into the dovetail cut-out (just behind the sphere) with the metal clips pointing up. 17. Click the Windows Start button, then Programs, then Cary WinUV, and then Align. 18. The first time you install the DRA you must check the optical alignment of the accessory as described in the Alignment check section.
Figure 25: DRA socket 21. Click the Windows Start button, then Programs, then Cary WinUV, and then Validate. Turn on the spectrophotometer. If the instrument will not initialize, proceed to the Troubleshooting section. 22. Close the Validate application. 23. If desired, confirm the proper operation of the accessory by performing the diagnostic scans described in the Diagnostic Scans section of the online help. You may wish to perform these tests on the initial installation of the DRA. 24.
Alignment check This procedure can be used to check the optical alignment of the accessory without disturbing any mirror adjustments. A one inch square of translucent paper (e.g., tissue) is required. 1. Open the Align (if it is not already running) by clicking the Windows Start button, then Programs, then Cary WinUV, and then Align. 2. Darken the room and set the instrument for white light operation as follows: Cary tab Beam Mode Double Y Mode %R Ave Time 0.
Figure 27. Checking the beam at the reference port. 5. Mount or hold the translucent paper directly in front of the transmission port. Check that the sample beam is confined to the surface area inside the transmission port. 6. Repeat the previous step for the reference beam at the reference beam entrance port. 7. If the reference and sample beam profiles meet the criteria specified in the previous steps, the accessory optics are aligned properly and no further alignment is necessary.
Figure 28: The optics of the DRA. 1. Click the Windows Start button, then Programs, Cary WinUV and then Align. 2. Click the Setup button. 3. Darken the room and set the instrument for white light operation by setting the following parameters: Cary tab Beam Mode Double Y Mode %R Ave Time 0.1 SBW 2 Slit Height Full 4. Select the Zero Order checkbox and click Apply. Place a piece of translucent paper in the sample beam path in front of M1 to check that the beam is centreed.
• • Check that that DRA is correctly locked down onto the instrument sample compartment floor. If the DRA is correctly installed, and misalignment persists, contact your local Varian service representative. Place a piece of translucent paper in the sample beam path in front of M2. Turn the adjustment screws of mirror M1 until the beam is centred on M2. 7. Place the translucent paper in the sample beam path in front of M3. Adjust M2 until the beam is centreed on M3.
11. Alternately adjust mirrors M4 and M5 to centre the reference beam on both the reference beam entrance and the reference ports such that the beam is not clipped by the cente mount sample holder. The reference beam is now aligned. 12. Return to Step 7 of Installation. Error checks and diagnostic scans The following section describes the procedures for a series of diagnostic scans or error checking.
Cary tab X mode: Mode X mode: Start/Stop Nanometers User-set range Y mode: Mode %R Y mode: Y min -5.00 Y mode: Y max 110.00 Scan controls: Ave time (s) 1.000 Scan controls: Data interval (nm) 0.500 Scan controls: Scan rate (nm/min) 30.000 Options tab SBW/Energy: Fixed SBW ON SBW/Energy: SBW (nm) 2.00 SBW/Energy: Beam mode Double SBW/Energy: Slit height Reduced Source: Lamps UV-Vis Source: Source changeover (nm) 350.
Zero %R error check - alignment check 1. With the transmission ports uncovered, place the large reference plate over the reflectance port. 2. From the main ’Scan’ dialog box box, click the Zero button and wait for the instrument to zero. 3. Remove the reference plate so the beam is going straight through the sphere into the sample cover. Close the sample compartment, the reading should not be greater than 0.5%R.
4. Click the Zero button and wait for the instrument to zero. 5. Place a mirror over the reflectance port, and close the sample compartment. Note the reading. If the reading is greater than 1.5%R, then either the specularly reflected beam is not entering the light trap, dirt on the lens is scattering the beam and creating a ’halo’ effect on the reflectance port, or the sample mirror does not have a good specular surface. If the reading is greater than 1.
Figure 29: The cuvette holder Installation and alignment To install the cuvette holder: Slide the cuvette holder over the dovetail so that it fits securely into the clips. Check the sample beam alignment before proceeding with transmission measurements. To record transmission data with the cuvette holder, refer to the 0°/d Transmission Measurements Using the Comparison Method.
Centre-Mount Sample Holders A centre-mount sample holder offers two distinct advantages over the external sphere sample holders on the DRA. One is the ability to vary the angle of incidence for reflectance and transmission measurements. The other advantage is the ability to measure the transmission and reflectance of a sample together (transflectance). There are several centre-mount designs, depending on the reflectance or transmission application intended.
Alignment Occasionally, the requirement exists to conduct fine tune alignment of the beam inside the integrating sphere. Use white light operation and observe the beam path adjustments through the accessory cover opening. To check white light alignment: 1. Alternatively block the beam at the reference and transmission entrance ports and view the alignment through the opposite port. 2. Click the Windows Start button, then Programs, then Cary WinUV, and then Align.
Figure 31: The clip style variable angle sample holder. Figure 32: The jaw style centre mount. The width limitation of the jaw style sample holder depends on the thickness of the sample and the maximum angle of incidence the application requires. The jaws protrude 12 mm from the frame of the sample holder. If possible, the reflectance standard and sample should be loaded so the reflecting surface is even with the front edge of the jaws.
Alignment Upon first time use, the sample holder should be loaded into the centre-mount port and checked for proper angle alignment to the sample beam, the beam should strike at normal incidence when the dial is set at 0°. If it does not, rotate the knob until the angle is normal to the sample beam, loosen the four screws along the perimeter of the dial and rotate the dial so it reads 0°. The reflecting surface of the standard should be the same angle of incidence as the intended sample.
bottom tip of the clip and the baffle. There is no need to use a diffuse reference standard with the clip style sample holder, the sphere wall serves as the reference. After loading the sample holder into the accessory, view the sample from the reference port, making sure the reference beam is not clipped by any part of the assembly at the incidence angles required.
Caution Exercise great care when loading the centre-mount cuvette holder into the integrating sphere, the sample holder is bulky and spilled sample solutions may damage the interior surfaces of the sphere. Small Spot Kit A sample loaded at the DRA reflectance port or other sample site should be the same size as the focused sample beam. If the sample is smaller than the beam spot, the accuracy of the results will be reduced.
Figure 34: The small spot kit lens holder, rail and lens. Note The small spot kit replacement for mirror M3 must be used instead of the standard accessory mirror. The two mirrors look similar, but the small spot kit mirror is visibly less concave than the standard accessory M3 and is marked "M-3 SSK". Installation and Alignment The small spot kit requires an initial installation. Once installed, the user can refer to the Operation section for details regarding reflectance measurements.
Figure 35: Installing the small spot kit. 2. Install the iris assembly in the position shown above. The mounting plate for the iris is magnetized to hold the iris firmly in place. Two adjustment controls are provided on the iris, one for adjusting the iris position laterally and one for controlling the aperture size. Open the iris fully. 3. Remove the lens holder from the dovetail base and mount the rail onto the accessory base plate as shown.
4. Turn on the instrument on and allow it to warm up (approximately 2 hours). 5. Set the instrument to Zero order using the Align application. See Installation step 14. 6. Once the instrument is warmed up, remove the reflectance standards from the ports (if they are currently loaded). Load the reflectance lens into the small spot kit lens mount. The reflectance lens is marked "R", the transmission lens is marked "T", and the centremount lens is marked "C".
Figure 37. The beam from the small spot kit with the iris partially open. 14. Remove the beam blocker from the reference beam path. 15. Replace the reflectance plug. The small spot kit is now aligned. 16. Turn off the instrument. 17. Plug in the DRA using the connector at the back of the sample compartment. 18. Fully open the iris and replace the accessory cover. 19. Turn on the instrument and allow it to initialize. 20. Return the iris to the position noted in step 13.
Figure 38. The powder cell fits into the sample holder at the reflectance port. Figure 39. The powder cell in position at the reflectance port. The design of the PCH-150 sample holder does not facilitate an accurate means of loading a powdered sample to an accurate packing density. An approximate packing density and reflectance measurement can be obtained using the following procedures. Prior to loading, the sample should be ground to the desired particle size.
Sample Preparation Using the PCH-150 Powder Cell Holder Figure 40. An exploded view of the powder cell. 1. Disassemble the powder cell holder. DO NOT disassemble the reference cell holder. Place the front cover onto the flat surface of a balance scale, face down, and load the quartz window into the cover. 2. Record the weight of the two sample holder components. 3. Load a portion of the sample into the powder cell cavity over the quartz window.
Figure 41. Calculating the packing density. 8. Calculate the packing density using the sample weight recorded in the previous steps. Reflectance Measurements Using the Powder Cell Holder To perform reflectance measurements using the Powder cell holder, proceed as follows. 1. Load the powder cell containing the Spectralon insert against the reflectance sample port of the sphere. There should be a Spectralon reflectance standard mounted at the reference port. 2.
• • The sample reflectance depends upon sample handling factors, such as the packing density, surface uniformity, and characteristics of the sample. Finely ground powder samples will give different reflectance results than the same sample when measured in its coarse, granular, or pressed powder form. The spectrum shape of the sample reflectance does not change with packing density, that is, the peak location does not change.
Figure 42: The optics of the double aperture accessory.
Figure 43. The double aperture attachment on the polarizer mount. The accessory optics should be aligned according to the Installation instructions before installing the double aperture. The base mount for the double aperture apparatus is the same base used for the polarizer. Install the double aperture accessory as follows: 1. Remove the DRA from the instrument sample compartment. Locate mirror M3 at the "R" position. 2.
8. Block the reference and sample beam entrance ports to the integrating sphere and configure the sample beam for white light operation. 9. Observe the beam profile as it strikes the aperture plate, adjust the height of the plate so the rectangular apertures are centreed on the sample beam. 10. Remove the beam blocker from the sample beam path. Observe the reflectance port from the open centre-mount port, mount a piece of translucent paper in the sample holder against the reflectance port.
Figure 44.
Figure 45. The polarizer attachment in the DRA. The polarizer assembly uses the same base mount as the double aperture apparatus. Install the polarizer assembly into the accessory as follows: 1. Insert the base mount for the polarizer into the locator holes in the accessory base plate as shown in the figure below. Fasten the device to the accessory base plate using the M5 socket head screw provided and a 4 mm hex wrench. 2. Click the Windows Start button, then Programs, then Cary WinUV, and then Align.
7. Suspend white light operations and remove the blocking device from the reference beam. The accessory is aligned for polarizer operations. The base mount can remain installed in the accessory when the polarizer is not being used. If adjustment to the sample beam alignment is required, an alignment check should be performed whenever the polarizer is removed. Note The polarizer is an attenuation device and may reduce significantly the signal-tonoise ratio of the accessory during use.
7. Flick the lockdown lever on the front instrument panel to the left. 8. Install the guillotine/light seal. 9. Load a reflectance standard at the reference and sample reflectance ports. Remove any centre-mount sample holders installed in the sphere and install the centre port plug. 10. Connect the accessory detector cable to the connector at the rear of the sample compartment. Make sure the detector cable does not obstruct the beam path inside the optical chamber of the accessory.
Figure 47. Removing the light seal. Note The lockdown lever is accessible just underneath the DRA base plate. 5. Slide the lever on the instrument front panel to the right. 6. Remove the front lockdown pin. 7. Tilt the front end of the accessory. Using the accessory handle, lift the DRA up and out of the sample compartment and store it in the accompanying wooden box. 8. Replace the sample compartment front panel.
An integrating sphere is sensitive to small-angle scatter from the sample beam coupling optics. Sometimes, the scattered radiation strikes the wall of the integrating sphere near the reflectance sample port, creating a "halo" surrounding the port. This halo-effect causes a small error in the measurement of the reflectance factor that is most significant when measuring samples of very low reflectance. This error is easily corrected by using the light trap zero baseline correction method discussed above.
4. Click the Baseline button. 5. At the 100%T scan prompt, select OK. The standard at the reflectance port serves as the 100%R reference. 6. At the 0%T scan prompt when running reflectance scans, either block the sample beam at the transmission port or replace the reflectance standard at the sample port with a light trap. When running transmission scans, the sample beam should be blocked for the 0%T scan. The recorded baseline correction will be effective until replaced by a follow-up baseline scan.
4. Click the Start button. 5. If the standard reference option was used for the baseline scan, the reflectance spectra is generated automatically. If the simple or zero baseline correction was selected, multiply the sample scan data by the spectral reflectance factors for the calibrated reflectance standard. 8°/d Reflectance Factor Measurements (Comparison Method) The DRA integrating sphere is fitted with a specular exclusion port.
3. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan. If using a previously defined baseline correction, retrieve the correct baseline. 4. Click the Start button. 5. If the standard reference option was used for the baseline scan, the reflectance spectra is generated automatically.
1. Collect a Baseline scan, following the procedures specific to transmission measurements. If the sample resides on a substrate, load an untreated substrate blank at the transmission port for the baseline scan. If the transmission sample is suspended in solution, load a blank cuvette at the transmission port for the baseline. 2. Load the sample at the transmission port and replace the reflectance standard at the reflectance port with a light trap.
Variable Angle Reflectance Measurements (Centre-Mount Sample Holder) The DRA can collect variable angle of incidence reflectance data when a centre-mount sample holder is installed inside the integrating sphere. Shift mirror M3 to the centremount position and align the transfer optics before proceeding with either of the following procedures. The centre-mount sample holder should be employed only when operating the instrument in double beam mode.
5. Remove the sample from the sample holder clip and load the empty sample holder into the centre-mount port. 6. Load Spectralon reflectance standards at the reference and sample reflectance ports. Install the magnetic covers over each respective port. 7. Collect a Baseline scan. 8. Mount the sample into the centre-mount sample holder and load the assembly into the integrating sphere. 9. Click the Setup button and check the parameters.
Figure 49. The beam falling on the reference mounted in the jaw style centre mount. 4. Examine the path of the reference beam inside the integrating sphere. The beam should strike the reference port without clipping any part of the sample or sample holder. 5. Remove the sample holder from the sphere and replace the sample with a calibrated diffuse reflectance standard. If a calibrated standard is not available, use an uncalibrated Spectralon standard.
Absorbance Measurements (Cuvette Centre-Mount Sample Holder) The following procedure can be used for obtaining absorbance measurements with a centre-mounted cuvette. In the centre-mount configuration, normally reflected light exits the sphere through the transmission port and is not counted. 1. Darken the room and drive the instrument to 500 nm. 2. Fill a clean cuvette with the pure solvent used as the sample preparation. Note If the intended sample is turbid, use an empty cuvette for the baseline scan.
7. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan. If using a previously defined baseline correction, retrieve the correct baseline. 8. Click the Start button. The value displayed by the instrument is the combined transmission. No data correction is required.
Transmission Measurements (Small Spot Kit) At the transmission port location, the DRA small spot kit can be used to measure a small test sample, or to measure a small portion of a larger sample. Prior to entering this procedure, the small spot kit should be installed and aligned. Mirror M3 must always be installed at the "T" position for small spot kit measurements. 1. Install the transmission lens, marked “T”, into the small spot kit lens holder.
6. Load the sample at the transmission port. Do not change the configuration of the integrating sphere in any other way. 7. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan. If using a previously defined baseline correction, retrieve the correct baseline. 8. Click the Start button. 9. The value displayed by the instrument is the sample transmission. No data correction is required.
of incidence. If the beam is off centre or will not fit on the sample, either adjust the sample mounting in the sample holder or re-adjust the sample beam optics using M3 to achieve the correct alignment. If any adjustments are made to the optics, make sure the sample beam still fits within the small spot lens aperture. Figure 52. The small spot kit beam falling on a sample using one of the centre mount options. 8. Examine the path of the reference beam inside the integrating sphere.
14. If the standard reference option was used for the baseline scan, the reflectance spectra is generated automatically. If the simple or zero baseline correction was selected and the jaw style sample holder was employed, multiply the sample scan data by the spectral reflectance factors for the calibrated reflectance standard or the data in Appendix B. If using the clip style centre-mount sample holder, no correction is required.
9. Click the Setup button and check the parameters. Normally, the setup parameters for the application should match those used for the baseline scan. If using a previously defined baseline correction, retrieve the correct baseline. 10. Click the Start button. 11. If the standard reference option was used for the baseline scan, the reflectance spectra is generated automatically.
problem. Impact of these factors can be minimized if you can localize the beam to the target area of the sample using the small spot kit so the beam just barely fits over the edges of the mask. Large sample reflectance measurements When measuring large samples that cannot be accommodated within the sample reflectance port cover, you will need to follow the steps below: Prior to recording the scan, make sure that mirror M3 is located in the correct position. To measure a sample:: 1.
Applying a Nitrogen Purge The Cary 4000/5000/6000i instruments are fitted with connection points for purging the optical system with nitrogen to enhance the performance of each instrument at extremes of its range. More details are provided in the Cary Hardware operation manual (part number 8510197200), supplied with the instrument. Nitrogen supplies are not available from Varian but may be obtained from commercial suppliers.
1. 2. External Instrument * DRA 3. Tubing 4. Flow meters 5. Shut-off 6. Manifold valves 7. Pressure 8. Nitrogen regulator control valve *Refers to the purge inlet labelled "Instrument". The DRA accessories each have an inert gas purge capability for reducing water vapour absorption inside the integrating sphere. The gas nozzle is located underneath on the lefthand side of the overhanging accessory. A nitrogen purge can be applied as follows: 1. Install the accessory into the instrument sample compartment.
NIR reflectance measurements (not for Cary 4000) Note Parameters activated by a radio button that are not specifically mentioned in the following procedure should be set to ’Off’ (e.g. the Signal-to-noise mode radio button). These parameters will not affect the procedure. 1. Click the Windows Start button, then Programs, then Cary WinUV, and then Align. 2. Click the Setup button. 3.
Data interval (nm) 1.000 Scan rate (nm/min) 600.00 SBW (nm) 2.00 NIR controls Ave time (s) 1.000 Data interval (nm) 2.000 Scan rate (nm/min) 120.00 Energy level 3.00 Baseline tab Correction Zero correction Autostore tab File Storage: Storage Storage on (prompt at start) Note The NIR detector is noisier than the UV-Vis detector, so a higher Signal Averaging Time (Ave time) may need to be set in the NIR.
7. Select the Baseline button from the Scan dialog. Follow the on-screen prompts to perform a 100%T baseline scan and a 0%T baseline scan. Hot Tip When performing reflectance measurements, remove the PTFE reference disk from the sample port and allow the light to be trapped by the magnetic port covers. 8. Once the baseline correction is complete, the Ordinate status display in the top left corner of the dialog will show ’Zero baseline’ in red text. 9. Clamp the sample over the sample port.
Options tab SBW/Energy: Fixed SBW ON SBW/Energy: SBW (nm) 2.00 SBW/Energy: Beam mode Double SBW/Energy: Slit height Reduced Source: Lamps UV-Vis Source: Source changeover (nm) 350.0 Baseline tab Correction Zero baseline/correction Autostore tab File Storage: Storage Storage on (prompt at start) 2. Place the specular port plug into position. 3. Place the appropriate PTFE reference plate over the sample port. 4. Select the Baseline button from the Scan dialog.
8. Remove the specular port plug and install the light trap in its place and click the Start button to collect the diffuse-only data. 9. From the main Scan window, click on the Calculator icon Maths dialog. to open the open the 10. On the graph displayed, highlight the first scan (of the total reflectance), by clicking on it. When the scan is selected, it will be highlighted in red. 11. From the Maths dialog choose Selected Trace and then the ’-’ (minus) sign. 12.
UV/VIS 0%T Correction This calibrates the photomultipliers for 0%T (electronic zero) effects. This is executed every time the instrument is switched on except if a DRA is installed (where the DRA correction factors stored in the DRA EEPROM are used). Instrument check: If high precision is needed at high absorbance, measure the 0%T error at 500 nm in the UV-VIS (blocked sample beam). The error should be less than 0.01 %T. Calibrate with the instrument fully warmed up.
instrument is fully warmed up would be beneficial. NIR 0%T correction This closes the shutter and calibrates the NIR detector for 0 %T errors. If a DRA is connected a mask must be placed in front of the transmission port (rear instrument beam) during the calibration process. The software will prompt you for this. Auto calibrate Will perform all the calibrations relevant to the instrument and DRA combination being used. User interaction is required if a DRA is in place.
Show status display ON Options tab SBW/Energy: Beam mode Double SBW/Energy: Slit height Reduced Source/Detector: Lamps UV-Vis Source: Source changeover (nm) 350.0 Source: Detector changeover (nm) 800.0 Independent tab Independent control ON Measurement mode Auto UV-Vis controls Ave time (s) 0.1 Data interval (nm) 1.000 Scan rate (nm/min) 600.00 SBW (nm) 2.00 NIR controls Ave time (s) 1.000 Data interval (nm) 2.000 Scan rate (nm/min) 120.00 Energy level 3.
1. Select the Baseline button in the Scan dialog box. Follow the on-screen prompts to perform a 100%T baseline scan and a 0%T baseline scan. Hot Tip When collecting the 0%T baseline scan do not block the beam instead, remove the PTFE reference disk from the reflectance port and allow the light to be trapped by the magnetic port covers. 2. Once the baseline correction is complete, the Ordinate status display in the top left corner of the dialog box will show ’Zero baseline’ in red text. 3.
1. Remove the accessory from the wood container and set it on a flat surface. 2. Check that each mirror mount in the optics chamber is fastened securely to the base plate. 3. Blow clean air or nitrogen over the transfer optics to remove any dust lying on the mirror surfaces. 4. Examine the surface of each mirror using a flashlight. Look for dust particles or film damage that might scatter the incident radiation. 5. Remove the reflectance standards and centre mount plug from the integrating sphere or box.
Standards Reference surfaces for reflectance and transmission in the solar wavelengths are available from (among others) Labsphere in the USA, the National Institute of Standards and Testing (NIST) in the USA, and from the National Physics Laboratory (NPL) in the UK. Labsphere provide reference surfaces with reflectances varying from 2%R to 99%R. Labsphere may be contacted at: P.O. Box 70 Shaker St, North Sutton, N.H.
Division of Electrical Science National Physical Laboratory Teddington, Middlesex TW11 OLW UK. Troubleshooting Warning This instrument contains electrical circuits, devices, and components operating at dangerous voltages. Contact with these circuits, devices and components can cause death, serious injury, or painful electrical shock. To avoid electrical shock operators and other unauthorized personnel must never remove the main cover.
References 1. Weidner V.R., Hsia J.J: J.Opt.Soc.Am. 71/7 (1981) 2. Zwinkels J., Dodd C.X.: Workshop on Optical Property Measurement Techniques, Commission of the European Communities. (1988). 3. Weidner V.R., Hsia J.J., Adams B.:Applied Optics 24/14 (1985) Alignment targets l (nm) 250 260 270 275 280 290 300 310 320 325 330 340 350 360 370 375 380 390 400 450 500 550 600 650 R 0.973 0.976 0.978 0.979 0.980 0.982 0.984 0.985 0.987 0.988 0.988 0.989 0.990 0.990 0.991 0.991 0.991 0.992 0.993 0.993 0.994 0.
(clip) difference angles. Samples are clipped into place. Centre mount cuvette holder Centre mount holder for cuvettes. Fits into the top of the sphere. 79 100387 00 Transmission cuvette holder Holds standard 10 mm quartz cuvettes in %T port of DRA. Mounts to the transmission port holder. 79 100383 00 Solid sample holder Aperture kit 79 100478 00 Kit containing 3 x apertures (1 mm, 2 mm and 5 mm), 4 small spacers and 1 large spacer.
