# Frequently asked questions

Hier finden Sie Anworten auf häufig gestellte Fragen. Bei weiteren Fragen kontaktieren sie uns bitte.

**1. How can I place an order?**

**2. What methods of payment are accepted?**

**3. How will the shipment be arranged?**

If you wish to use an own courier account, please specify the courier and account number at the time of ordering.

**4. Do you have any distributors in other countries?**

CHINA

Hannotech Co. Ltd. (www.hannotech.com.cn)

HyperCyte Biomedical Co. Ltd. (www.hypercyte.com)

Shanghai Biochemical Co. Ltd. (www.shbcbio.com)

INDIA

Clementia Biotech (www.clementiabiotech.com)

JAPAN

Corefront Corporation (www.corefront.com)

Funakoshi Corporation (www.funakoshi.co.jp)

Nacalai Tesque Inc. (www.nacalai.com)

SINGAPORE

Scientific Procurement (S) Pte Ltd. (www.scientificprocurement.com)

SOUTH KOREA

JYSCO Ltd. (www.jysco.com)

TAIWAN

KYS Technology Co., Ltd. (www.kyst.com.tw.com)

**5. How can I get a copy of your print catalog?**

**6. How is the relation between nominal and measured mean particle diameter?**

**7. How do you measure the size of your microparticles?**

^{®}Multisizer II. This is a multichannel particle size analyzer, which employs the electrical impedance method to provide a particle size distribution analysis. The method is based on the change of the impedance, when a particle passes the measurement zone. This change is proportional to the particle volume.

**8. What is the “Coefficient of Variation (% CV)”?**

Our micromer

^{®}particles with diameters between 2 and 10 µm have CV values ≤ 5%.

**9. How do you measure the size of your nanoparticles?**

The Zetasizer determines the size by first measuring the Brownian motion of the particles in a sample using Dynamic Light Scattering (DLS) and then interpreting a size from this using established theories.

There are four different types of data analysis of the PCS measurement:

- the cumulants analysis
- the multi exponential analysis,
- the CONTIN analysis and
- the non negative least squares analysis.

The Z-average Size is the most important and stable number produced by the technique. This is the size to use if a number is required for quality control purposes.

The Z-average Size is obtained by the cumulants analysis. This analysis gives only two values, a mean value for the size and a width parameter known as Polydispersity Index (PDI). This mean size is an intensity mean and directly calculated from the signal intensity.

According to our experiences we use different types of analysis for the evaluation of our nanoparticles. Especially the different scattering properties of fluorescent or magnetic nanoparticles require on optimal adjustment of the analytical methods.

**10. What is the Polydispersity Index (PDI)? Can the standard deviation of the size distribution be calculated from the PDI?**

Under the assumption of a Gaussian distribution the standard deviation can be calculated from the PDI value and the hydrodynamic particle diameter (Z-Average, ZD) as follows:

**11. How do you measure the surface charge of your particles?**

**12. Which magnetic separation device do you recommend for larger volumes of magnetic particle suspensions?**

**13. Why is the zeta potential of silica particles with amino groups on the surface negative?**

Comparison of the zeta potential-pH functions of plain and amino functionalized silica particles (diameter: 1 µm)