FAQs

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FAQs

A few hints that may save you a phone call.

Questions

  1. What time is it in Indiana?
  2. Could I get a copy of your catalog mailed to me?
  3. How do I place an order?
  4. What methods of payment are accepted?
  5. How will Bangs Labs be shipping my package?
  6. I just received my order, but can't see any beads in the suspension. Where are they?
  7. Do you have......?
  8. Is the microsphere suspension sterile?
  9. What charge do microspheres carry?
  10. What is the difference between surface titer and parking area, and how are values determined?
  11. What do COOH/1, COOH/2, and COOH/5 signify?
  12. What is the density of your microspheres?
  13. What is the refractive index of your microspheres?
  14. How spherical are the particles?
  15. How smooth are the surfaces of microspheres?
  16. How do you size your microspheres?
  17. What is the "coefficient of variation?"
  18. Are microspheres heat-resistant?
  19. What solvent(s) will microspheres tolerate?
  20. How stable are microspheres?
  21. How do I download and view PDF files?
  22. Why do I have to register every time I visit the Product Selection Guide or TechNotes?

Answers

  1. What time is it in Indiana?

    Indiana is in the Eastern time zone and we now observe Daylight Savings Time, so whatever time it is in New York is what time it is here.

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  2. Could I get a copy of your catalog mailed to me?

    Absolutely! Simply contact our Customer Service Department via phone (317-570-7020 or 800-387-0672) or email (info@bangslabs.com). The catalog is available in both a print version and a .pdf file. We would be happy to send you our catalog by snail mail, email, or both; just let us know your preference. Don't forget to also request our free quarterly newsletter, Painless Particles®.

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  3. How do I place an order?

    Orders may be placed via phone (317-570-7020 or 800-387-0672), fax (317-570-7034), website, or email (info@bangslabs.com). Please have shipping and billing information available.

    Our customers may place orders directly with Bangs Laboratories or with one of our distributors.

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  4. What methods of payment are accepted?

    Orders may be placed using a purchase order or credit card. Payment must be in U.S. dollars by check (cheque) drawn on a U.S. bank, or by wire transfer. (Note that bank wire charges are the responsibility of the originator, not the receiving party.) Visa and MasterCard are also accepted. For credit card orders, we require the account number, name as it appears on the card, and the expiration date on the card.

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  5. How will Bangs Labs be shipping my package?

    Unless otherwise arranged, all shipments will be transported with United Parcel Service (UPS); freight and insurance charges are prepaid and added to the invoice. If you wish to use a courier account, please specify the courier and account number at the time of ordering. Customer shall pay all taxes, assessments, duties, custom charges, and other government fees of any nature whatsoever that are levied on products for each shipment.

    If you'd like to know where your package is, please contact us and we will be happy to track your package for you.

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  6. I just received my order, but can't see any beads in the suspension. Where are they?

    Particles that are ~50µm or larger (about the size of a grain of salt) can generally be seen with the naked eye. Microscopy must be used to visualize individual smaller particles.

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  7. Do you have......?

    buoyant or neutrally buoyant microspheres

    That depends upon the specific gravity of the suspending solution; to be buoyant, microspheres must have a lower density than that of the suspending solution; to be neutrally buoyant, the density of the microsphere must match that of the suspending solution (see Question 12 for the densities of common microspheres).

    glass microspheres

    We recommend that you try our silica (SiO2) microspheres, available in sizes from ~0.2µm - 5µm with plain (silanol, SiOH) surface. See our TechNote 104, Silica Microspheres, and silica product brochure for more information, and our Product and Ordering Section for specific availability.

    hydrophilic microspheres

    Yes, our silica microspheres may be utilized when a hydrophilic microsphere is needed. See TechNote 104, Silica Microspheres, for more information and our Product and Ordering Section for specific availability.

    hydrophobic microspheres

    Polymeric microspheres are hydrophobic. See our Product and Ordering Section for specific availability.

    standards

    Yes, we actually specialize in flow cytometry standards; please visit our Flow Cytometry Catalog. We also have NIST Traceable Particle Size Standards and confocal microscope standards available. See TechNotes 105, Microsphere Size Standards, and 106, Confocal Standards, for technical information.

    surfactant-free

    Yes, we have a few lots of polymeric microspheres that were synthesized without surfactant. Suspensions are charge-stabilized by the presence of microsphere surface groups, typically sulfate (SO4) or carboxyl (COOH). See our Product and Ordering Section for available products.

    We also have a wide selection of polymeric (functionalized or non-functionalized), silica, magnetic, dyed (colored and fluorescent), and protein-coated microspheres. We encourage you to explore our online Product and Ordering Section and downloadable TechNotes and product brochures, or to contact us directly with any questions.

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  8. Is the microsphere suspension sterile?

    We do not provide a guarantee of sterility with our microspheres. Microspheres may be pasteurized, sterilized (e.g. gamma irradiation), or thoroughly washed (e.g. 3X wash in sterile medium - see TechNote 203, Washing Microspheres) prior to use.

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  9. What charge do microspheres carry?

    We expect that most of our microspheres bear some charge, although we do not characterize them in this respect (e.g. via electrophoretic mobility, zeta potential, etc.). Charge will depend upon the specific surface groups that are present, the numbers in which they are present, and buffer composition and pH. We expect that non-functionalized polymer microspheres will bear a weak negative charge at neutral pH, due to negatively charged surface groups from the initiator. Microspheres that have been specifically functionalized will likely bear the greatest charge, e.g. from copolymerization of functional monomer, such as acrylic acid or methacrylic acid.

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  10. What is the difference between surface titer and parking area, and how are values determined?

    The 'surface titer' value speaks to the level of functionalization for a defined mass of functionalized microspheres. Surface titer values are available for many, but not all, lots of functionalized microspheres. In some instances, when material was not titrated, theoretical surface titer values may be available. We report surface titer values in whole numbers as microequivalents per gram microspheres (µeq/g). NOTE: µeq/g is equal to micromole/gram.

    • Polymeric/COOH: Surface titer is determined by conductometric (usual) or potentiometric titration.
    • Polymeric/NH2: Amino-functionalized microspheres are often not titrated, due to concerns regarding reliability of the resultant data, i.e. it is believed that H+ ions penetrate the surface, or 'fuzzy layer,' of the microsphere, resulting in titration of functional groups that are not truly available for covalent coupling reactions. When performed, 'titration' is typically accomplished through a ninhydrin or other colorimetric assay for determination of amine content.
    The 'parking area' describes the density of the functional groups, or 'brush,' i.e. how much space is occupied by a single functional group. The parking area is inversely related to the surface titer value, and is calculated from it. An equation for calculating parking area (if a surface titer value is available) is presented in TechNote 206, Equations. A more detailed description of parking area is provided in "The Particle Doctor®" section of our March 2001 issue of Painless Particles®.

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  11. What do COOH/1, COOH/2, and COOH/5 signify?

    The method of functionalization is specified for COOH-functionalized microspheres:

    COOH/1: Made by copolymerization of styrene with unsaturated short-chain mono-carboxylic acids, like acrylic or methacrylic acid.
    COOH/2: Made with styrene and maleic acid. The anhydride hydrolyzes with time to maleic acid, with two adjacent carboxylic acid surface groups.
    COOH/5: Indicates a post-synthesis modification.

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  12. What is the density of your microspheres?

    Within our product line, microsphere densities range from ~0.9 g/cm3 - 2.2 g/cm3, depending upon composition. The table below lists expected densities for microspheres of different compositions. Values are as reported in the literature for the bulk material, or as determined from the analysis of a few representative lots.

    Composition Approximate
    Density (g/cm3)
    PMMA 1.19
    PS 1.05
    P(S/2%DVB) 1.062
    P(S/10%DVB) 1.067
    P(S/20%DVB) 1.074
    P(S/55%DVB) 1.097
    P(S/80%DVB) 1.110
    Silica 2.0
    Superparamagnetic ~1.089-2.2,
    depending on % iron oxide

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  13. What is the refractive index of your microspheres?

    Within our product line, refractive indicies range from ~ 1.4-1.6 at 589nm, depending upon composition. The table below provides expected refractive indices for microspheres of different compositions. Values are as reported in the literature for bulk material, or as determined from the analysis of a few representative lots.

    Composition Approximate RI
    (589nm)
    PMMA 1.489
    PS 1.59
    P(S/DVB) Higher than PS,
    see PDVB
    PDVB 1.615
    Silica 1.43-1.46
    Superparamagnetic Unknown

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  14. How spherical are the particles?

    Although we do not characterize beads in terms of sphericity, we expect that most lots of polymeric and silica material contain highly spherical beads. Provided that microspheres are of sufficient size, they undergo optical microscopic examination. SEM and TEM images of representative lots of very small particles (nm) have also revealed their highly spherical nature. Silica microsphere populations will likely include a low level of permanent doublets (i.e. fused small microspheres) due to the nature of the synthesis process.

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  15. How smooth are the surfaces of microspheres?

    The surfaces of most of our products are considered to be fairly smooth (with the exception of BioMag®); although, surface morphology is not specifically characterized.

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  16. How do you size your microspheres?

    Sizing methods include: dynamic light scattering, single particle optical sensing, optical microscopy, granulometry (laser diffraction), Coulter principle, scanning electron microscopy, transmission electron microscopy, and sieving. See our TechNote 208, Microsphere Sizing, for further information on sizing methodologies. Products have the sizing method that was used to determine the mean diameter documented on the Certificate of Analysis.

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  17. What is the "coefficient of variation?"

    The coefficient of variation (CV) typically refers to the size variation of a bead population. The CV may be determined by dividing the standard deviation by the mean diameter, i.e.: CV = Standard Deviation/Mean Diameter.

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  18. Are microspheres heat-resistant?

    The tolerance of microspheres for heat will depend upon their composition and the length of time they are exposed to elevated temperature. The approximate glass transition temperatures (or softening points) of different materials are provided in the table, below.

    Composition Approximate Density
    (Glass Transition Temp) °C
    PS 95
    P(S/2%DVB) 99
    P(S/10%DVB) 114
    P(S/20%DVB) 136
    P(S/55%DVB) 250
    P(S/80%DVB) 405
    PMMA 105
    silica >>1000

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  19. What solvent(s) will microspheres tolerate?

    Microspheres are generally suspended in deionized water or a biologic buffer (e.g. borate buffer). Compatibility of microspheres and solvents will depend upon their respective solubility parameters (SPs) (numeric values). Numbers that are near one another indicate solubility, whereas disparate numbers indicate solvent resistance, or insolubility. For example, the SP of polystyrene is 9.1; if the SP of a solvent is very similar, e.g. in the range of ~8.6-9.6, it will probably dissolve the microsphere with ease. If the SP is <7 or >11, it may swell the polymer, or dissolve only with extended exposure and/or heat. Microspheres that are crosslinked (e.g. DVB is commonly utilized to "crosslink" polystyrene), will possess some solvent resistance. A listing of common solvents and non-solvents of polystyrene is provided for convenience. Solubility parameters of other solvents and polymers may be obtained from the literature, e.g. Polymer Handbook, J. Brandrup and E.H. Immergut (Eds).

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  20. How stable* are microspheres?

    Provided that microspheres are stored in the supplied buffer, and in accordance with our recommendations, they should have the following stabilities:

    • Non-functionalized (plain polymer) and COOH-, or NH2-functionalized microspheres are considered to be stable indefinitely.
    • Pre-activated microspheres - 6 months from the date of manufacture.
    • Magnetic microspheres are considered to be stable indefinitely.
    • Dyed (colored) microspheres are considered to be stable indefinitely (color and surface for coating).
    • Fluorescent microspheres are considered to be stable indefinitely, although photobleaching from exposure to light could limit the shelf life, particularly for those with surface-attached fluorophore (see also comments for Flow Cytometry products, below).
    • ProActive® (protein-coated) products - 2 years from date of coating (see Certificate of Analysis). A minimal decrease in activity (generally 10% or less) may be observed over the full two-year period.
    • Flow Cytometry products - 12 months from the date of purchase.

    *Please note that the term 'stability' refers to stability of the surface (e.g. surface functional groups, protein) for bead coating purposes, or to the color/fluorescence of dyed microspheres. The colloidal stability of the suspension will depend upon a number of factors including bead size and composition, storage conditions, suspending solution/buffer, etc. See our TechNote 202, Microsphere Aggregation, for tips on preventing and reversing aggregation.

    Storage: We recommend that microspheres be stored in the dark at refrigerated temperatures (generally 2-8°C), with continuous rolling where possible (particularly for magnetic microspheres). Fluorescent microspheres should be stored in opaque bottles. We recommend that microspheres be handled using aseptic techniques to safeguard against microbial contamination (which generally results in a lowering of binding ability). Freezing of polymeric microsphere suspensions may cause irreversible aggregation, and should be avoided.

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  21. How do I download and view PDF files?

    As you may now have discovered, Bangs Laboratories has many technical documents that require the use of Adobe® Reader®. To view our TechNote library and other documents, you must first download the Adobe Reader. And don't worry, Adobe Reader is absolutely free of charge at adobe.com! With this viewer, you will be able to view, print, and save any of the documents in our library.

    Please click on the Adobe icon to the left and follow the instructions to download and install the viewer specified for your particular computer's operating sytem.

    When you return to our website, please choose the TechNote or another document to view and click on the title. The Adobe Viewer will automatically start and load the document. From that point you can view the document online. You can also print the document (FILE-PRINT) or save a copy of the document on your hard drive (FILE-SAVE AS).

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  22. Why do I have to register every time I visit the Product Selection Guide or TechNotes?

    Bangs Labs' Product and Ordering Section, online ordering, and TechNotes sections require that you register with us first. This helps us track who is visiting our site. We have tried to keep this as unobtrusive as possible.

    Please be assured that we will not sell your name or our mailing list to any other company. You won't start getting more annoying e-mail messages every morning as a result of registering here. We will, however add your name to our mailing list, and you will receive our quarterly newsletter "Painless Particles®".

    These sections make use of internet "cookies" to save some of your registration data until your next visit. This information (your name, e-mail address, and country) is saved on your computer as cookies (contained in a text file within your browser's folders). We use these data to customize your browsing experience and to ensure you get all the correct information, based on where you live. No web site you visit, other than Bangs', has access to these particular cookies.

    If you have noticed that you have to register every time you re-visit the TechNotes section or the Product Selection Guide, you might be using a browser that does not accept cookies (or perhaps cookies are disabled in your browser preferences).

    We suggest you view this site using the most recent version of Netscape, Firefox, or Internet Explorer. You may download any of these browsers for free.

    If you are currently using one of these browsers, but are still having trouble, please make sure that cookies are enabled in your browser preferences. Also keep in mind that if you surf the internet using more than one browser or on more than one computer, you will have to re-register. Netscape saves its cookies in a different location than Internet Explorer.

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If you aren't able to locate answers to your microsphere application or handling/use questions within the above FAQ's, or our TechNotes, References, Product Brochures, and Product Data Sheets, we invite you to call us directly, or to contact "The Particle Doctor®" through our website.