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Qels Sop Dec 2007
BrowseUploadSign inJoinBooksAudiobooksComicsSheet MusicWelcome to Scribd! Start your free trial and access books, documents and more.Find out moreQuasi-Elastic Light Scattering Instrument (Brookhaven)
Laser Safety Instrument Operation Data Handling
December, 2006 Revised, December, 2007
Section 1: Laser Safety Part 1: Part 2: Part 3: Part 4: Part 5: Part 6: Part 7: Part 8: Part 9: Part 10: Eye Protection Laser Hazard Classification Laser Safety and the Eye Specification Sheet for Melles Griot 25 LHP 928 Laser Registration Form for Laser Laser Eye Protection Selection Table (from American National Standard Z136.1) Spectral Characteristics of Laser Eyewear Specification Sheet for Laser Eyewear D14 Sample Certificate for Laser Eyewear D14 Specification Sheet for Laser Eyewear KOS-6102
Section 2: Instrument Operation Part 11: Part 12: Part 13: Part 14: Part 15: Detector System Operation Laser Operating Instructions Laser Operation and Information Manual Packing List Dynamic Light Scattering (i.e. QELS) Operating Instructions
Section 3: Data Handling Part 16: Part 17: Part 18: Simple Introduction to DLS Data Analysis Molecular Weight Determination Using Zimm Plot QELS Operational Considerations
Section 1 Laser Safety
EYE PROTECTION Do NOT look directly into the laser beam. Wear protective eyewear when working near the laser beam. The protective eyewear must be appropriate for the wavelength and power of the laser beam. The eyewear provided in the lab (B122) is appropriate for this laser- it provides an optical density of at least +5 at 632.8nm. The eyewear specifications are described in the next sections.
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Laser Hazard Classification Classes of Lasers (adopted from ANSI Z-136.1-1993*)
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Class 1 1. Not capable of emitting in excess of the Class 1 AEL 2. Most lasers in this class are lasers which are in an enclosure which prohibits or limits access to the laser radiation Class 2a 1. Lasers in the visible region of the spectrum which do not exceed the Class 1 AEL for exposure less than or equal to 10E3 s 2. The output of the laser is not intended to be viewed 3. An example of a Class 2a laser is a supermarket point-of-sale scanner Class 2 1. All Class 2 lasers are in the visible region of the spectrum 2. Continuous wave lasers which can emit accessible radiant power which exceeds the Class 1 AEL for the maximum duration inherent in the laser, but do not exceed 1 mW 3. Pulsed lasers which can emit accessible radiant power which exceeds the Class 1 AEL for the maximum duration inherent in the laser, but not do not exceed the Class 1 AEL for an exposure of 0.25 s Class 3a 1. Have output that is greater than or equal to 5 times Class 2 AELs Class 3b 1. Continuous wave - between the Class 3a limits and 500 mW 2. Repetitively pulsed - radiant energy between 30-150 mJ per pulse for visible and infrared, otherwise greater than 125 mJ per pulse; average power less than 500 mW Class 4 r Limits exceed Class 3b limits
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Biological Safety | Chemical Safety | Radiation Safety | Home | UIUC | About RSS | Contact Information | Training | Fact Sheets | Rad Safety Manual | Rad Materials | X-Ray | Laser Information concerning Division of Research Safety programs of the University of Illinois at UrbanaChampaign is intended as guidance for University of Illinois at Urbana-Champaign students, staff, and faculty engaged in activities related to their education, research, and/or employment. The information is subject to change and updating at any time. Copyright © 2003 University of Illinois at Urbana-Champaign Division of Research Safety. Contact webmaster.
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http://www.ehs.uiuc.edu/rss/laser/laserhazard.htm8/9/2004 10:35:59 AM
dermatology. B. Vancouver Hospital & Health Sciences Centre. FRCPC
From the Lions Laser Skin Centre. Presented at the American Academy of Dermatology Annual Meeting Poster Session. Washington.html (1 of 7)8/9/2004 10:33:58 AM
. Division of Dermatology. MD.Laser Safety and the Eye
Osama Bader. Vancouver.C. D.org/laser/eyesafety. MD. 1996
Abstract What are the effects of laser energy on the eye? Are there any specific symptoms of laser eye injuries? What types of laser safety eyewear are available? What are the technical considerations for eye safety? What factors should be considered when selecting specific eyewear? Practical Pearls in Laser Eye Safety References
http://www. and University of British Columbia. February 10-15.C. and Harvey Lui.
exposure duration. As laser retinal burns may be painless and the damaging beam sometimes invisible. and beam size.. As LSE often look alike in style and color. visual transmittance.org/laser/eyesafety.
http://www. assistants. Protective eyewear in the form of goggle. Ignorance of any of these factors may result in serious eye injury.html (2 of 7)8/9/2004 10:33:58 AM
. industry and research. laser operator. every facility must formulate and adhere to specific safety policies that appropriately address eye protection.1400 nm (the majority of lasers used in dermatology) contributes to the so-called "retinal hazard region" and can cause damage to the retina.dermatology. while wavelengths outside this region (i.Laser Safety and the Eye
(Click the images below for a magnified view. field of view. Color coding of laser handpieces and LSE may help to minimize confusion. In accordance with the ANSI Z136. and shields provides the principal means to ensure against ocular injury. LSE should not move between laser rooms. nor should they be carried in lab coat pockets between use. each laser requires a specific type of protective eyewear. The site of ocular damage for any given laser depends upon its output wavelength. while transmitting sufficient light for good vision. and impact resistance. glasses. comfort.e. especially in multi-wavelength facilities where more than one laser may be located in the same room. Laser safety eyewear (LSE) is designed to reduce the amount of incident light of specific wavelength(s) to safe levels. maximal care should be taken to provide protection for all persons in the laser suite including the patient.3 (1988) guidelines. and observers. effects on color vision. it is important to specifically check both the wavelength and OD imprinted on all LSE prior to laser use. and must be worn at all times during laser operation. ultraviolet and far infrared spectrum) are absorbed by the anterior segment of the eye causing damage to the cornea and/or to the lens. Laser light in the visible and near infrared spectrum 400 . optical density (OD). and factors that must be considered when selecting LSE include: laser wavelength and peak irradiance.)
THE UNPROTECTED HUMAN EYE is extremely sensitive to laser radiation and can be permanently damaged from direct or reflected beams. With the enormous expansion of laser use in medicine. The extent of ocular damage is determined by the laser irradiance. absence of irreversible bleaching of the filter. The integrity of LSE must be inspected regularly since small cracks or loose fitting filters may transmit laser light directly to the eye.
a green 532 nm laser light would produce a green flash followed by a red after-image). This wave band is also know as the "retinal hazard region". heavier than spectacles or wraps
fit tightly on the face typically worn over vision-correcting prescription eye glasses usually constructed with frame vents to minimize lens fogging larger.400 nm) or far infrared (1400 .
Exposure to the invisible carbon dioxide laser beam (10. 400 .e. Photoacoustic retinal damage may be associated with an audible "pop" at the time of exposure.1400 nm) can cause damage to the retina resulting in scotoma (blind spot in the fovea).org/laser/eyesafety.600 nm) can be detected by a burning pain at the site of exposure on the cornea or sclera.. there may be difficulty in detecting blue or green colors secondary to cone damage.dermatology.10.html (3 of 7)8/9/2004 10:33:58 AM
. Laser light in the ultraviolet (290 .g. Exposure to a visible laser beam can be detected by a bright color flash of the emitted wavelength and an after-image of its complementary color (e. and pigmentation of the retina may be detected.Laser Safety and the Eye
Laser light in the visible to near infrared spectrum (i. When the retina is affected. Visual disorientation due to retinal damage may not be apparent to the operator until considerable thermal damage has occurred. Exposure to the Q-switched Nd:YAG laser beam (1064 nm) is especially hazardous and may initially go undetected because the beam is invisible and the retina lacks pain sensory nerves.600 nm) spectrum can cause damage to the cornea and/or to the lens..
dermatology.Laser Safety and the Eye
a frame that usually has two separate lenses with side shields can be made with vision-correcting prescription eye glasses
a frame with a single lens that covers both eyes usually lighter than spectacles/goggles
There are two important concepts: 1. the longer the exposure time. the higher the MPE. LSE must be worn within the NHZ. MPE levels are determined as a function of laser wavelength. exposure time and pulse repetition.1 standard defines MPE levels for specific laser wavelengths and exposure durations.org/laser/eyesafety.
In practical terms. reflected or scattered laser radiation exceeds the MPE.
2. The MPE is usually expressed either in terms of radiant exposure in J/cm2 or as irradiance in W/cm2 for a given wavelength and exposure duration.
Exposure to laser energy above the MPE can result in tissue damage. when using dermatologic lasers the entire laser procedure room should be considered to be within the NHZ because the laser fiber or handpiece can be directed anywhere in the room. Maximum permissible exposure (MPE). Generally. the lower the MPE. The Nominal Hazard Zone (NHZ) is the physical space in which direct. The ANSI 136.html (4 of 7)8/9/2004 10:33:58 AM
http://www. is the level of laser radiation to which a person may be exposed without hazardous effects or biological changes in the eye. the longer the wavelength.
. Impact resistance. 3. It can be expressed by the following formula: OD = log10(Ei /Et) Ei = incident beam irradiance (W/cm2) for a "worse case exposure" Et = transmitted beam irradiance (MPE limit in W/cm2) Example: OD of 4.
http://www. The required OD for any given laser can be determined by: (a) calculation.
1.g. For example. ANSI 136. etc. The OD of the LSE will decrease if the LSE is damaged. (b) consulting nomograms or tables (e. certain LSE may interfere with visualizing monitoring equipment or detecting cyanosis during general anesthesia.10 seconds following noticeable melting or flame.0 allows 1/10. 2.org/laser/eyesafety. Optical density (OD) of the LSE for the wavelength being used.Laser Safety and the Eye
1..000 of the laser light energy to be transmitted. Comfort of the design to enhance compliance. 4. or (c) consulting the laser manufacturer. Effect on color vision: the colored filter material may reduce color vision and contrast. Laser warning signs must be placed at the entrance to laser operating rooms. Absence of irreversible bleaching when the LSE filter is exposed to high peak irradiance. Field of view provided by the design of the eyewear. heat. LSE must be resistant to dust. 5. Laser wavelength at which protection is afforded. so that they will not loose their effectiveness.1 guidelines). 1.dermatology. 2. OD refers to the ability of a material to reduce laser energy of a specific wavelength to a safe level below the MPE. The damage threshold refers to the maximum protection that the LSE will provide for at least 5 .html (5 of 7)8/9/2004 10:33:58 AM
. creating additional hazards.
Health Devices 1993. Safety procedures should be in accordance with ANSI and OSHA guidelines (and others. Laser Institute of America.org/laser/eyesafety. Orlando FL. so proper care and handling is mandatory. Access to the laser operating room should only be granted to those individuals who have been appropriately educated in laser safety. LSE can be very expensive. 5. 8. Anonymous. 3. 1988. Whenever laser energy is used in the immediate vicinity of the eye (e. Color coding of the laser handpiece and LSE may help to minimize confusion especially in facilities where multiple laser wavelengths are available.7.g. United States Department of Labor. Laser energy and its dangers to eyes. Lasers in Surg Med 1995. it is mandatory to check the wavelength and optical density imprinted on each pair of LSE prior to its use. Laser Institute of America. Great care must be taken to avoid accidentally exposing the straps of the patient goggles to laser light. 2. OSHA Instruction PUB 8-1.
http://www. Occupational Safety and Health Administration.html (6 of 7)8/9/2004 10:33:58 AM
1. 1986.Laser Safety and the Eye
2. Guidelines for laser safety and hazard assessment.1 (American National Standards Institute ) American National Standard for the safe use of lasers. 16:215-225. 6. 5.dermatology. ANSI 136. appropriate opaque "mini" goggles must be worn. Washington DC. 7. 22:159-204. Plastic patient eye shields cannot be expected to withstand the thermal and mechanical effects of pulsed lasers. Laser safety. The integrity of the LSE must beinspected regularly since small cracks or loose fitting filters may permit the laser beam to reach the eye directly. As LSE often looks alike in style and color. Each laser facility must develop its own Safety Procedures to be enforced by an appropriately trained Laser Safety Officer for the facility. 4. Sliney DH. ANSI 136. The patient's eyes must always be protected from laser energy. and should never be used. treating eyelids) a stainless steel or lead eye shield should be positioned on the surface of the orbit after the application of a topical ophthalmic local anesthetic. 3. 1991. where appropriate).3 (American National Standards Institute ) The safe use of lasers in health care facilities. nor should they be carried in lab coat pockets between use. If the patient is awake. since this can ignite them. Orlando FL. [1995 revision will be released soon] 4. LSE should not move between laser rooms.
dermatology.html (7 of 7)8/9/2004 10:33:58 AM
This poster reproduction is hosted by DermWeb at UBC We invite your comments & suggestions. Created 10Feb96 Revised: 24Dec96
http://www.Laser Safety and the Eye
We thank the Massachusetts General Hospital Dermatology Laser Center for providing us with some of the photographs used in this poster.org/laser/eyesafety.
23 Beam Divergence (1/e2) (mrad) 0.5% rms <1.66 0.0 Beam Diameter (1/e2) (mm) 0. -249 for 115 Vac. fast scanning. and 35 mW.
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.115 Vac.03 mrad after 30 minutes Long-Term Drift : 82% per hour Noise (rms) : <1% Noise Frequency : 30 Hz to 10 MHz Input Voltage : 100 Vac. The 25 LHR/P 925. or 230 Vac outlets. including power supply $ CE compliant (230-Vac version only) The Melles Griot family of high-power helium neon lasers exhibit the long life. or 230 Vac810% (specify) Input Frequency : 50–60 Hz Shock : 25 G for 11 msec Operating Temperature : 420°C to =40°C Nonoperating Temperature : 440°C to =80°C Operating Humidity : 0% to 90% non condensing Nonoperating Humidity : 0% to 100% CDRH Class : IIIb IEC Class : 3B CE Compliance : Compliant (230-Vac version only)
Air-Cooled Ion Lasers Helium Cadmium Lasers Helium Neon Lasers
cw Output Power (mW) 17.
57 OUTPUT 42.74 1029.4 cable length 1.4 f44.8
4 holes 4-40!6.8 m 10 10
laser power indicator FRONT VIEW
161 remote interlock 54 SIDE VIEW 637.3 241
25 LHR/P 925 high-power helium neon laser head
High-power helium neon laser power supply
40.Air-Cooled Ion Lasers
SHUTTER 78.97 OPEN COOLING VENTS CLOSED
75.4 on 36 circle
25 LHP 828 and 928 high-power helium neon laser head
mounting area plane of polarization SHUTTER indicated by of linearly polarized shading lasers CLOSED OPEN 4 holes 4-40!6.4 deep on 36 circle 25.5 25.
dyes/solvents. noise. Hazard Class(3b. fire explosions. robotics. ergonomics
Signoff: original on file signed by Robert Pelton Date: February 20.4) Year Manufactured Type (CW or Pulsed) Lasing Medium Maximum Output Operational Wavelength(s) [nm] Pulse width/repetition rate Beam Divergence Emergent Beam Diameter Active/Inactive Purpose List non beam hazards: Laser-generated air contaminants. 2007 Each laser requires an SOPS to accompany the unit for operation and maintenance
.66 mrad 1. Serial No. electrical. 2006 CW Helium-Neon 35 mW 632.23 mm Active Source for Quasi-Elastic Light Scattering instrument NA
Manufacturer Model No.Registration Form for Class 3b and 4 Lasers
Complete this registration form for each laser Department: Room: Chemical Engineering B122 Building: JHE PI/Supervisor: Robert Pelton Melles Griot 25-LHP-928-249 9541EQ-1 3b August.8 NA 0. collateral & plasma radiation. compressed gasses.
Not recommended as a control procedure at these levels.4 and 1.6.
.1-1993
Table 4 Simplified Method for Selecting Laser Eye Protection for Intrabeam Viewing (Wavelengths Between 0.2 for other wavelengths. See 4.AMERICAN NATIONAL STANDARD 2136. The skin also needs protection at these levels. These levels of output power could damage or desfroy the attenuating material used in the eye protection.f
Q-Switched Lasers Non-Q-Switched Lasers Continuous-Wave Lasers Continuous-Wave Lasers Long-Term Staring (less than 1 hr) Beam
Use of this table may result in optical densities (OD) greater than necessary.4 pm).
9746 * 734.00
DYE 7 6 5 4 3 2 1 0 200
EN207 Wavelength 190-380 nm yes 606-694 nm
OD 5+ 5+
%VLT 18% Blue
Per Pair $120.5+
%VLT 15% Purple
Wavelength 180-315 180-400 >315-400 576-600 582-598
Mode D R D DI I
Rating L6 L4 L4 L4 L6
Per Pair $140.00
DI4 9 8 7 6 5 4 3 2 1 0 200
EN207 Wavelength 190-400nm pend 680-710nm 685-705nm
OD 5+ 5+ 6+
%VLT 56% Teal
Per Pair $150.00
EN207 Wavelength 576-600 nm yes 585-595 nm
OD 5+ 6.5565 * fax 734.KRY
EN207 Wavelength 190-579 nm KRY
%VLT 10% Red
Per Pair $120.noirlaser.1708
.lasereyeprotection.769.00
KRR 8 7 6 5 O D 4 3 2 1 0 200
EN207 Wavelength 190-400nm yes 625-850nm 662-835nm 633nm
OD 5+ 4+ 5+ 5+
%VLT 12% Blue
Wavelength 180-315 180-315 >315-400 >315-400 625-830 830-850 625-670 800-830 670-800 Wavelength pending
Mode D R D R DR DIR I I I Mode
Rating L7 L3 L4 L6 L4 L3 L4 L4 L5 Rating
Per Pair $140.com
8 7 6 5 4 3 2 1 0 200
w ave le ngth
www.com * www.769.521.
www.NoIR
P.800.O. Box 159 South Lyon Michigan 48178 Phone: 1.com Product Specification LaserShield DI4 Customer: Product Designation (OPN): Luminous Transmittance: Date of Revision: Edited by: L-Rating 180-315 D L7 + R L3 >315-400 D L4 + R L6 DR 625-830 L4 DIR 830-850 L3 I 625-670 / 800-830 L4 I 670-800 L5
Varied DI4 11% 2/12/06 David W.769. Bothner
Graphs represent nominal filter characteristics
Optical Density 190-390nm 5+ 625-850nm 4+ 662-835nm 5+ 633nm 5+
5 OD 4 3 2 1 0 200 300 400 500 600 700 800 900 1000 1100 Wavelength (nm)
#35 Wrap-Around
#39 Large Fitover
#33 Universal
#31 Small Fitover
#700 Universal
#36 Adjustable Universal
.521.769.9746 734.5565 Fax:734.noirlaser.
>800 to 830 nrn * L 4 625-670.
Composition: Front side: Intermediate layer: Inner ride:
Spectral range In nm
180 to315nrn
625 to 870.05
. M I 48178 USA NOlR Dl4 Laser Eye Protactor.10.DINCERTCO EC TYPE-EXAMINATION CERTIFICATE
NolR Laser Company 6 155 Pontiac Trail SOUTH WON.Olk
DIN CERTCO Eye Protection and Personal Protective Equipment
06. Filter DIN EN 207 Annex II of the Dirlective 8918861EEC 77650-PTB-03 and 114311-PZA-05 Poly m r
Manufacturer's code: Model: Type of product: Test specifications:
Materhl: Configuration: Prescrtptlon lens: Total thickness:
2 l mm .>800-830 1 L4 NOlR CE >670 to 800 nm * L5 >670-800 1 L5 NOlR CE OIR * >a30 to 850 nm L3 * >830-850 DIR t 3 NOlR CE DIR * >850 to 860 nm L2 >850-860 DIR L2 NOlR CE 0 1 10600 nm * L2 * 10800 0 L2 FtOlR CE 1
>316 to 400 nm L4 L6 >316-400 D L4 825 to 830 nrn L4 625-830 DR L4 NOlR CE
* L7 +
180-315D L7
+ RL3NOlR CE
+ R LB NO1R CE
We herewith cwtify that the above-mentioned model fulfills the basic requirements for health and protection laid down in the Directive of the European Communky on Personal Protective Equipment 8916881EEC.
© 2005 The Kentek Corporation.com/diode-ruby-overspec-kos-6102...00
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Section 2 Instrument Operation
3) Wipe the sample vial with a Kimwipe to remove dust and insert into sample chamber. 6) Turn on the power supply for the photomultiplier tube (located just on the photomultiplier tube).
. and type additional identification information regarding your sample in the “Notes” box. Select the length of your experiment (typically between 1 and 3 minutes for standard particle size measurements) in the “elapsed time” box. and re-pressing SET/ENTER. Set the desired temperature by pressing SET/ENTER.8 nm on the wavelength selector wheel on the photomultiplier tube and the OPEN position on the laser shutter. 11) Click on the “Params” button in the control window (upper left). particle size distributions as calculated by exponential (top right) and CONTIN (mid right) sampling. 4) Turn on index matching fluid pump for ~30s to remove any dust from the fluid. • Give your sample a name (sample ID). LASERGARD GOGGLES MUST BE WORN STARTING AT THIS STEP THROUGHOUT THE OPERATION! 10) Return to the computer. If air bubbles are observed in the lines. the cumulant particle size calculation window (mid left). 8) Click on “File – Database”. and the count rate history window (bottom right). Click on the “Dur” button in the control window (upper left). add more decalin (by pipette) to the sample chamber. the autocorrelation function window (bottom left).DYNAMIC LIGHT SCATTERING OPERATING INSTRUCTIONS
Todd Hoare – September 2004 Revised by Yuguo Cui – December 2006 WARNING: DO NOT ADJUST THE KNOBS ON THE PINHOLE BETWEEN THE LASER AND THE SAMPLE CHAMBER OR ON THE PHOTOMULTIPLIER TUBE – ADJUSTMENTS WILL DE-ALIGN THE LASER! PART A – START-UP 1) Ensure the laser shutter (on laser) is CLOSED and the photomultiplier tube wavelength selector wheel is CLOSED (in the C position) 2) Turn the key control switch on the laser and wait for 30 min for the laser to warm up. enter your name as the operator ID. 7) Double click on the Brookhaven Instruments folder on the desktop of the computer. Double click on the BIC Dynamic Light Scattering icon to open the program. Leave all other boxes unchecked. 5) Turn the temperature bath ON. Double click on your data folder so that all data you save is directed to this folder (your previously saved files should be visible in the sample ID window when your folder is active)
PART B – SAMPLE MEASUREMENTS 9) Open up the laser by selecting 632. • Input the test temperature (note: the actual test temperature may be different from the setpoint temperature at T<15°C or T>35°C – measure your sample temperature directly using a thermocouple in those cases). typing in the temperature (including the first decimal point). The default windows which appear are your control window (top left).
If spikes are observed in the curve. Increase the slit size on the photomultiplier tube – the 100. The viscosity and refractive index will be automatically inputted. If kcnts/s reading is too low: i. The correlation data curve should look like a sigmoidal decay curve. Data points which lie outside the “acceptable” region you defined using the dust cutoff number will appear in grey in the count rate history window and will not be considered in the particle size calculations. so use with care! The “Use Dust Filter” box should remain unchecked (at least initially) in a standard experiment.8nm. stop the measurement (red dot in the control window) and click on the “Layout” button in the control window. a factor of 104) exists between the first and last delays. The default intensity distributions generated by the program will not be affected by the values you input here. b. decrease if the baseline is too long) to a new. select the dust filter cutoff number. Do not change any other parameters in the “Layout” window. first calc. only number and weight distributions. Increase the concentration of your sample ii. • Input the angle – 90° for standard samples. bottom left) being a flat baseline. If the baseline is too long or too short. Typical numbers which could be used range from 25 (a relatively sensitive filter) to 100 (a relatively unsensitive filter removing only the biggest spikes in the count rate history graph). iii. Check the following parameters (stop the measurement by clicking on the red dot button in the control window if necessary to correct any of these parameters): a. • If desired. • Keep all other boxes at their default values (wavelength = 632. Change the last delay time (increase if the baseline is too short. channel = 2) 12) Start a measurement by clicking on the green dot button in the control window. c. WARNING: since light scattering relies on the natural variation in the count rate in order to measure particle size. If your suspension medium is not in the list or is a mixture of solvents. Adjust the first delay such that approximately 4 decades (ie. Increase the filtering percentage of the laser beam. The count rate history (bottom right window) should look like a random residual plot in statistics – if a baseline trend is observed (a) your temperature may not yet be stable or (b) your sample is aggregating. Delay times are properly set. you have dust or aggregates in your sample and you may want to (a) remake your sample with a filtered solvent or (b) apply the dust filter to your data by clicking on the “Params” button in the control window and checking the “Use Dust Filter” box. Repeat this process as necessary to achieve a proper baseline. • Input the real and/or imaginary refractive indicies of your particles if you know them or keep the default values if you do not (as is typically the case).• Select the suspension fluid (“aqueous” works for all water-based buffers). select “unspecified” as your liquid and manually input the appropriate viscosity and refractive index. use of a sensitive dust filter may artificially skew your result. Accept changes by clicking “OK” and restart the measurement by clicking on the green dot in the control window. self-beating laser. guessed value.
. The average kcps (the “A CR (cur. 200. This will allow you to filter out data points which are significantly different than previous data points already collected.)” value in the control window) should be between100-250. with approximately the last 1/6 of the curve (on the righthand side of the correlation data window. Do the opposite for kcnts/s readings which are too high. and 400 micron slit sizes may be used for DLS. • Select “Measured Baseline” as your normalization method.
time of use. c. Repeat steps 9-15 to run your next sample. The effective diameter (Eff Dia) of your particle is also given in the control window along with the estimated polydispersity of your sample. Close laser shutter. upstairs lab JHE 365 ext. d. 16) To perform replicate measurements on the same sample. select “ISDA – Double Exponential (Dblexp) – New Graph Window” from the top menu and click on the “Fn List” button in the new window which is opened. 14) Click on the “Summary” box in either of the particle size distribution windows to see the mean diameter as calculated using the exponential (top left window) or non-negative least squares (CONTIN. 17) To change samples (MUST BE DONE IN THIS ORDER!): a.ca. c. Sign log book with date. and double click on the file you want to review. select your folder (see step 8). click on “File – Database”. Turn the temperature bath off. A good measurement should have a “Base diff” of <0. Turn the key control switch off the laser. while exponential may work better for multi-modal systems. office JHE 138 ext. 27036)
. f. operator. CONTIN is appropriate for relatively monodisperse samples. b. contact Cui (e-mail cuiy3@mcmaster. To review this data later. Select the data source (the title of your control window) to see the distribution. Typically. PART C – SHUT-DOWN 18) If you are then finished with the machine: a. and comments on any problems you had with the equipment. the word “STOPPED” will appear in the top left corner of the control window. Close the laser shutter (on laser) and the photomultiplier tube wavelength selector wheel (in the C position). Remove your sample and repeat steps 3 and 4 to insert a new sample. main lab JHE 139 ext.1% (as given in the control window). Close photomultiplier tube wavelength selector wheel (should read “C”). e. 15) Save your data if desired by clicking on “File – Save Correlation Function”. b. Exit the program – leave the computer on. If you know you have a bimodal distribution. 26073. middle left window) methods. Use the same method to view the distributions generated by any of the statistical packages listed under the “ISDA” tab. 27020. click on the “Clear” button in the control window to clear the existing data and restart the correlator by clicking on the green dot button in the control window. If you have any questions.13) When a measurement is complete. d. Turn off the power supply for the photomultiplier tube. 5-6 repeat measurements are done.
Section 3 Data Handling
I look for trends as a function of fit order. Double Exponential Fit There is no literature reference. AND. however. A true bimodal requires at least 3 degrees of freedom: one for each of the modes in size and a third representing the ratio by intensity of the amount in each mode. an easily solvable situation. ref. In our version you must choose the baseline (PARAMS command button to select Calc. nonlinear least squares fit to an assumed double exponential in G1. Let me know if you need more information. or. Diam. The parameters of each fit appear in columns as a function of the fit order. and we can supply the other source codes at your request. This. quartic. and two exponential decays. and we assume no Mie scattering corrections (light scattering corrections) apply. none are annotated. any of the books on PCS/DLS (Chu. is D. We stop the fit at the first normalized point that is not positive. and Poly from a quadratic fit. Koppel. cubic. for example) show the development. quadratic. NNLS. of course. Cumulants The original lit. This is a standard. J.. Then we have two measured parameters and two unknowns. The Lognormal fit is by intensity. Our Lognormal fit (a Gaussian in log space) requires two parameters: the median and the geometric standard deviation.Phys. three pieces of information that can be reclaimed for the fits. and I stop believing the fit when the trends reverse. before I believe a bimodal fit in CONTIN. so any changes you wish to make you will have to work at it. sometimes. II. The decays. I. Or.BASE command button to select which measured baseline) and the number of channels to fit(Layout).. for Meas. a unimodal distribution. never say what the shape of the distribution function looks like. depends on the baseline you have chosen. we use the Eff. The source code for CONTIN has always been included on the hard disk. With these two parameters we can plot any value on a Lognormal curve.. Schmitz.Chem. So there are four parameters: two pre-exponentials that represent the relative intensities. M. I want to see that at least the Cubic fit in Cumulants is required. of course. With a polynomial fit one can. 57(1972)4814. Brookhaven Instruments) Here are some hints for running and interpreting the BI-ISDA software. Our version is really four separate fits: linear. The Lognormal is. two. etc.Simple Intro to DLS Data Analysis (Bruce Weiner. However. To calculate these two parameters. contact us and we can guide you to that part of the program you need to look at most to affect your changes. Thus. Gamma. Berne&Pecora. This usually tells me if there are one. Therefore we are fitting G1 not G2.
. or Meas. by definition.
the problem of fitting was attacked from the point of view of information theory. from which we calculate the particle size. ref.yield the assumed translational diffusion coefficients. In this paper and references therein. Samp. As the fit proceeds you watch N. (Again. Using the positivity constraint. The first cumulant is used to determine the zeroth order mean size for iteration. Optica Acta. Over the years it has generally been agreed that the forced. very good reason to believe that only two exponentials are a good model for the scattering system. the distribution shape is determined as an envelope over a function determined by the number of exponentials. III. and Omega equal 2 is its first order guess. There is no analog solution. any number of numerical solutions gave a fit that are about the same from a chi-square test point of view. Sornette. seems to broaden distributions more than the other two fits. a grid search is performed to maximize N and Omega (a larger omega means a relatively higher resolution). a parameter which relates the closest approach of the exponentials. Omega. and Mean Size change. for details.Parker.
. see the literature. is N. This explained early failures to distinguish between fits of two or three exponentials. then this fit may not converge.). See the lit. BUT. or to distinguish fits between different assumed functional forms. Sampling suffers less than CONTIN or NNLS from artifacts at high and low diameters. 28 (1981) 1059. N equal 2 is the first order guess. Ostrowski. D. From the theory it was shown that there was a very limited amount of information that could be obtained. ref. P. you have a very. Exponential Sampling (also known as the Pike/Ostrowski Method) The lit. and E. and an uncertain baseline. or if the measured function will not easily be constrained to fit the sum of two exponentials. Omega. Exp. or if the baseline selected is very far from accurate. All this was true even though the shape of the various fits >could be very different: a bimodal or a broad unimodal fit equally well.R. and. worse. unless. If the data is noisy. In this technique one varies the following parameters: N the number of exponentials. At the end. The fit is not just a sum of exponentials. and a mean size. was basically an insoluble problem. double-exponential fit is the least useful. It was shown that a sum of exponentials.Pike. maybe only 2 or 3 parameters. This fit has a characteristic advantage and disadvantage: Exp. with experimental noise.
or a group of 1 to 32 channels that the user can move to a flat portion of the ACF.Herb. Disadvantages: Same as NNLS. 1 (1985) 496. Here a fixed sum of exponentials. ref. Comm. Provencher original suggested the constant should be 0. If the peak at the low end follows the manually selected low size. the user may select an upper and lower limit or let the automatic guess prevail. but the user can override that.Morrison. the authors of NNLS made the spacing between the upper and lower size limits linear. In our program we make a guess based on the initial decay of the function for the lower limit and 100 times that for the larger limit. So the problem is reduced to a linear fit of the pre-exponentials using the positivity constraint: all the pre-exponentials must be positive. is S. You can also refit the same data. In CONTIN the function that is minimized is the sum of two terms: the normal sum of residuals squared plus a term that is the sum of residuals cubed. CONTIN is only one of many. otherwise. Advantage: When it works well.Grabowski. Then they changed it to quadratic in recognition of the Pike work showing that limited resolution is all one can ever get out of a sum of exponentials. Computer Phys. That can be changed. a baseline error may produce an artifact in the high size end. Repeating the measurement will show this artifacts either disappear. In our fit we use 0.5 as the constant. it is probably an artifact. Like NNLS. V. but other workers have preferred 0. Try fitting with the measured baseline as either the "autobaseline" in the 9000AT Windows software. NNLS probably gives the highest resolution in particle sizing than any of the other algorithms. Advantages: Very well known algorithm. Provencher.] Tends
. manually choosing a lower size limit. they have no physical meaning. At the high end. CONTIN The lit. is I.IV. [This may be a disadvantage depending on the continent you admire most for scientific thinking. NNLS. ref. Originally. Choose the portion closer to where the curve seems to have decayed into the noise.2 or 0. Non-negatively Constrained Least Squares The lit. say 50 in all. The problem is linearized by having the user select an upper and lower limit for the particle sizes. So much depends on the "a priori" knowledge of the distribution shape.5. many types of regularization fits. It varies from zero (then CONTIN is equal to NNLS) to one (then the second term is as important as the first term. Europeans love it. E. In addition. There is a constant in front of this second term. CONTIN tends not to resolve peaks as well. or shift size considerably.3. Disadvantage: A slightly noisy ACF will yield artifacts of a few nanometers. 27 (1982) 213 & 229. and C. Langmuir. but one must use the source codes and recompile. is chosen.
for one set of data. roughly. and peaks much larger than expected (usually due to baseline errors. physical point of view)? If yes. say. but it does not create as many artifacts as NNLS or CONTIN. unimodal distributions of. changes in baseline. WARNING: the more you play with the parameters. bias. But the next type of sample doesn't work as well. suggested for polymer distributions. You can sometimes get more than a mean and measure of width. repeat. These are all. the original CONTIN has a large number of variables that can be tweaked. YOU CAN NEVER. then they are probably real. Then we can place some confidence in them. but only if they are not too broad. NNLS works well for particle size distributions. If you want access. EVER hope to get complete distribution information from DLS. Also. let BIC know and we can show you how to do that. Sampling tends to broaden any peaks it finds. polymers in solution. meaning they appear with different first/last delay settings. CONTIN penalizes multimode fits. Are they repeatable? Are they robust. ROUGHLY. and is best for broad.? Do they make sense (chemical. Be wary of bi and trimodals. all in the source code.to give smoother results. Therefore. although often mistaken for aggregate sizes). say no more than 5:1 in size.
. EVENTUALLY. The Exp. Bias. the position of each peak and ratio by intensity of the two peaks. angles.
VI. Result: Your tweaking satisfied what you believed to be true before you made the measurements. and you probably know. These artifacts are of two types: a peak well below any size that can be explained from the chemistry (always due to noisy ACFs). etc. Summarizing Some Statements Above Over the years we found that different fits work well for different >situations. bias is the word that comes to mind. the better the fit. So we like it very much when at least two of these algorithms agree.
Set the goniometer to 90o by clicking on Set Detector Angle button. however. whereas numbers 100. Click on the Dark Count Rate button. If air bubbles are observed in the tubing. dn/dc. March 2005. 1. If you have not set up your folder. Click on the Experimental Parameters button in the lower part of the screen. 2. A calibration liquid. 1. When the dark count rate is measured. Click on Exit button.01 to 10 mg/ml. updated March 2007) Prior to measurement of MW. do not filter your sample. Note: the numbers 1. Remember each time you insert a vial into the sample chamber. just create one now. Solvent and calibration liquid should be filtered.
3. 4. 100 kDa). click on Hardware. usually toluene. Double click on the BIC Zimm Plot Software icon to open the program. if filtration removes some polymer.Procedures for Molecular Weight Determination through Zimm Plot (Xianhua Feng. the Dust Rejection Ratio to 1. Low concentration for high MW (e. Polymer stock solution may be filtered. Click on File − Database. Note that the filter you use must resist the solvent and calibration liquid. Take care not to bring dust into the sample when you make polymer solution. Solvent for background subtraction. the Dust Rejection Multiplier to 3.g. 5. add more decalin to the sample chamber. set the Duration/Repeat back to 1 second. and 400 are in micrometer. 7.
. Rotate the aperture wheel on the detector optics to the “C” position. 6. and 3 on the wheel are in millimeter. Double click on your data folder so that all data you obtained later will be automatically saved in this folder. turn on index matching fluid pump for ~30s to remove any dust from the fluid. Make sure that the actual pinhole is the same as what you have set. Double click on the Brookhaven instruments folder on the desktop of the computer. 200. 2. In the menubar of the main window. Click on the Experimental Parameters button and then
3. Enter 10 seconds in the Duration/Repeat field.33. Number of samples: polymer − at least 5 samples with different concentrations. Set the Number of Repeats to 10. Hardware Configuration. Select None for Polarization Analyzer and Out for Interference Filter. above 1 mDa) and high concentration for low MW (e. Polymer refractive index increment. and the pinhole at 1 or 2 or 3 mm. Click on Motor. Polymer concentration: 0. Insert the highest concentration sample and set the lowest angle (30o) by clicking on Set Detector Angle button.
Operation Please refer to DLS operating instructions for start-up before measurement. 2. you should know the following information. Click on OK button to return to the main menu.
Otherwise. Click on Save List As and enter a filename up to 8 characters so that next time you can use this list by simply clicking on the Load List button and selecting it. 12. Fill in the Sample Identification. Otherwise. Select a liquid from the pull down box or select Unspecified and then fill in the refractive index for the sample liquid if it is not among those listed. the Ref. Click Delete All to remove the default list. the calibration constant is 1 ~ 4 × 10-9 for count rate as low as 10 kcps.
. you may correct the refractive indices by selecting Apply reflection correction. Then click on OK to accept the changes. Enter the first angle. click on Done button. In that case. If you have set angles before. Once one sample is done. Index of Vat Liquid (1. Note: the difference between the last angle and the angle preceding it may not be equal to the increment entered. click File/Save As and enter a file description. Adjust the laser power and/or pinhole size to obtain maximum count rate ~ 106 cps. click on the angle in the list and type over it. Insert the calibration liquid. you may need to change angles in the list. Click on OK to return to main menu. 11. 13. Index of Sample Cell (1. After solvent run. Click on Yes button to initiate a solvent run at the various angles you set before. Click on the Sample Parameters button in the lower part of the screen. 9. but keep it less than 1. To change any angle in the list. click on Set List Range button. or 1 ~ 4 × 10-10 for count rate of 100 kcps.
10. When finished.474).Intensity button. Select the calibration liquid and click on Calibrate Instrument button. last angle. Fill in the value for dn/dc. The goniometer will automatically change to 90o. If the sample liquid is water. For toluene.5). Fill in 633 in the Wavelength field. 14.5 Mcps. Click Edit Measurement Angles List. and Depolarization Ratio (0). Click on OK button to save the setting. click on Exit. Operator Identification. and Notes fields. Keep default numbers for Ref. Also notice that a minimum of 7 angles is required. Usually the angles are set between 30o and 150o. you will be reminded to change the sample and input new concentration. Click on OK button to return to the main menu. Note: do not change laser power and pinhole after you have calibrated the instrument since calibration constant is dependent on these parameters. If you know the depolarization ratio for your sample. click on Load List button and select the file you need. enter your value instead of default value. and increment. you will be asked for running your sample and entering the sample concentration. If not. although the reflection correction is small. Click on Start button to initiate a measurement. A window on sample liquid measurement appears. Click Angles in the menubar at the top of the screen. Select Auto Save Results. Check if the data are saved by clicking on File/Database.
Finally. 3.
4. To return to the main menu. You can change the plotting constant to determine which data points are good and which are bad.Data analysis 1. highlighted line in the list of angles. You can delete any single point by clicking on the point in the plot and then double clicking on the blue.
2. Usually the default plotting constant is OK. Double clicking again will restore the data and plotting point. You can fit constant angle and constant concentration data to straight lines or to polynomials up to 5th order by choosing numbers in the list boxes labeled Fit Angles and Fit Concentrations.
5. You can restore the original plotting constant simply by clicking on the Default button. click on Settings button. return the goniometer to 90o. You can edit the concentration simply by overwriting it in the list box and then save the changes by clicking on File/Save or File/Save As. To print the results. Clicking on Calculate button to obtain molecular weight. Shut down the instrument. click on File/Print Report. 6.
A larger value (necessitated by the section of the Gaussian fit algorithm that minimizes chi squared) indicates large particle contamination (e. dust. 1.4 Baseline Adjust Value The contents of the long delay bins should be very close to zero (as indicated by a 0. Probably the best solution to plot size choice is to use a large value (e.g. Too few bins will effectively act as a smoothing filter obscuring any true multimodal detail that may be present. 1. bins containing no collected data). the reliable upper limit is usually considered to be 0.g. 1.e. Size Range Light scattering techniques are good for particles down to 10 nm size. 1. The presence of dust is also indicated by a large (e. One micron is pushing the upper limit a bit.1. Reliable results for multimodal distributions require fit errors less than 1. greater than 10) residual.0% baseline adjust).g. 45-60) and simply collect enough data to avoid any artifact holes in the distribution.5 Minimum Diameter and Range The minimum diameter and range must be chosen so that the bins holding counts for the largest and smallest particle sizes are empty in the intensity weighted plot.3 Fit Error Results for unimodal distributions with fit errors greater than 2 may not be reliable.5 micron. High values (too many bins) can lead to apparent (but false) multimodal distributions. Going below 10 nm would require a very good signal to noise ratio (such small particles scatter very little light) and perhaps is best done with a multiple angle instrument.2 Channel Width The Channel Width must be increased for larger (slower diffusing) particles to ensure that about 2 exponential decays are collected (this is an optimal value).
. QELS OPERATIONAL CONSIDERATIONS The considerations enumerated below must be considered together: all the provisos must be met (e.g. Too many bins can result in holes in the distribution (i. If more data is collected the results may oscillate or may snap between unimodal and bimodal or trimodal. a large residual value is not indicative of dust unless the fit error is adequately small). Choosing the plot size brings with it the usual problems associated with histograms. agglomeration) which may not be visible on the plot of PSD (depending on the minimum diameter and range values chosen). 1.
If the standard deviation is large with a poor fit to the Gaussian model the distribution is probably bimodal.8 Intensity Weighted Distribution Although the volume weighted distribution is usually of most interest one should always inspect the intensity weighted distribution. This value is appropriate for polystyrene but for lower refractive index polymers the target count rate should be 200 KHz. 1.
. For small particles the difference in weighting function is significant. greater than 20%) with a small Gaussian chi squared value the distribution is probably a broad unimodal. low diameter peaks in the volume weighted distribution correspond to definite.g. for the same data set a large smoothing value can yield a broad unimodal distribution. but because of the very strong weighting given to the small particles during the conversion from intensity weighted results to volume weighted results these may end up appearing as sizable peaks in the volume weighted distribution.6 Smoothing for Unimodal versus Bimodal Choosing smoothing values can be difficult especially if one does not know whether to expect a unimodal or bimodal distribution. If the standard deviation is large (e.9 Optimal Count Rate We have found that the optimal count rate for some polymer particles is significantly lower than the 300 KHz suggested by the manufacturer. Not only should it be ensured that the intensity weighted distribution not contain any counts in the largest and smallest diameter bins (indicating off-scale particles) but also the distribution should be checked for low count number peaks of small diameter. The solution is to collect more data and ensure that any small. well defined peaks in the intensity weighted distribution.7 Weighting for Solid or Vesicular Particles In choosing between solid particle or vesicular weighting there is little difference for large particles. These may be noise. 1.10 Round versus Square Cells Disposable round cells give poorer reproducibility and broader apparent distributions than the square cells with optically parallel sides.1. 1. For a given data set a low smoothing value can yield a bimodal distribution. In that case the best approach (probably the only approach other than guessing) is to collect more data to allow better estimates of standard deviation and chi squared to be made. One can encounter data sets which are on the borderline between these two situations. 1.
For example. approaching one hour or more) or if your spin fluid increases temperature
. every aspect of the data appears normal). This results from the following considerations: the conversion from intensity to volume weighting amplifies the small particles' scattering intensity greatly to compensate for their low scattering intensities compared to large particles. greater than one micron) particles (so much light is scattered by the very large particles that it overpowers the light scattered by the small particles.e. Unfortunately. evaporative cooling can occur or a rise in temperature due to friction can happen). The important parameters are: particle density.g. the intensity weighted distribution is strongly dependent on scattering angle. lack of detection of the larger particle size mode in a bimodal distribution (the smaller mode is amplified much more strongly during the conversion from intensity to volume weighting). After investigating this we concluded that the only way to determine the accuracy of results indicating particle sizes below 200 nm is by consideration of several of the operational parameters in conjunction. Small errors in measurement of scattering intensity can lead to huge errors in the volume weighted distribution. for some polymers 140 nm particles may give the same instrument output as 60 nm particles (for the small particles the signal to noise ratio appears fine. 3 DISC CENTRIFUGE CONSIDERATIONS For low density polymer particles disc centrifugation seems to be able to give accurate results only for diameters greater than 200 nm. rotation speed. Low density particles less than 200 nm move by diffusion distances comparable to the migration due to the applied field in the disc centrifuge (the manufacturers usually claim that the minimum size limit for low density particles should be 60 nm). above 8. In practice these deficiencies lead to the following effects: incorrect volume weighted distributions for skewed particle size distributions. the detector effectively does not see the small particles).e. time required for separation.g. If you spin at high speeds (e. lack of detection of sub-micron particles in the presence of very large (i. Multiple angle QELS instruments are typically about twice the cost of fixed angle machines. there is no easy way to determine from the nature of the raw or derived data whether the results are reliable or not when the indicated diameter is less than 200 nm.2 SINGLE ANGLE QELS DEFICIENCIES QELS techniques measure an intensity weighted distribution (angle dependent) which must be converted to the more physically meaningful volume weighted distribution (angle independent). QELS techniques have rather low inherent resolution. Many of these problems can be overcome by measuring at several angles. This confounds the results.000 rpm) for long times (e. the resolution appears fine. temperature change of spin fluid during separation (i.
Do all of these companies have facilities nearby? The disc centrifuge is good for larger size particles but below 200 nm the results can be invalid for low density polymers. We have not used the Brookhaven ZetaPlus so we do not know whether the addition of zeta potential measurement would degrade its PSD measurement capabilities. QELS instruments are good from 10 to 500 nm but the single angle instruments suffer from the problems enumerated above. The results from the different techniques are seldom exactly the same (the differences become more pronounced as the PSD becomes greater). The methods we usually apply are: a light scattering technique. Coulter. breadth. One does expect the results of the average sizes obtained from the various techniques to be close. one expects the shape of the distribution (i. The Coulter unit was not really designed for PSD measurements. A QELS instrument that measures at multiple angles and also does zeta potential certainly sounds attractive provided the particle sizing has not been compromised in favour of the zeta potential measurement. CONCLUSIONS The choice between the various suppliers of particle sizing instruments (Brookhaven. Malvern..e. ELECTROPHORETIC MOBILITY MEASUREMENTS We previously used use a Coulter Delsa 440 electrophoretic mobility analyzer (from which the zeta potential can be calculated if desired) . This instrument can give approximate particle size values but the quality of the measurements are not as good as those from QELS instruments specifically meant for particle sizing.more than a couple of degrees you should suspect the results (you should also be aware that the temperature indicated by some of the disc centrifuges is not the spin fluid temperature but the temperature of the compartment the rotor sits in). modality) to be similar for the various techniques. 4. Nicomp) frequently is made on the basis of who will be able to provide the best service. We feel most comfortable if we measure the particle size distribution (PSD) using at least two methods based on different measuring principles. electron microscopy. This instrument has been replaced with a Brookhaven Zeta Plus. Does this instrument give you the electrophoretic mobility data or does it give you the zeta potential (derived from the mobility data based on assumptions)?
. further. a physical separation technique.
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