The graph in the upper left shows that using a light source with a 650 nm wavelength there is no difference in the scattering patterns between a 0.05 and 0.07 µm particle. The graph in the upper right shows how there is a difference in the scattering patterns when using a 405 nm wavelength light source. Since there is a difference in the scattering pattern, we can distinguish between to two particle sizes. The graph to the lower left shows results when 30, 40, 50, and 70 nm latex standards are measured (individually) on the LA-950.
The LA-950 can accurately detect particles as small as the 40 nm latex shown on the left, and the 30 nm Ludox silica on the right. The Ludox is the sample we use to verfiy performance of the DT-1200 system. It is well characterized and accepted as being 30 nm in size. The LA-950 has the best small particle detection performance of any laser diffraction particle size analyzer.
This is the training screen when installing the DT-1200, showing the expected 30 nm result on the right.
The LA-950 also has excellent performance measuring large particles – typically dry powders. The graph on the top shows the data from the coffee application note. Anything over 2000 µm would be missed by the MS2000. The data below from the brochure shows data for 2700 µm alumina balls. Powder samples with any fine particles (<20 µm) are analyzed on the MS2000 using “Fine Powder Mode”. This cuts off ALL data above 250 µm. Otherwise many samples include ghost peaks around 1000-2000 µm. If Fine powder mode is used, the customer will never see any particles >250 µm even if they are really there.
The PowderJet dry powder feeder is a superior sampler than the Sirocco in many ways. The sample flow path is straight down from the nozzle through the cell where the measurement is made. With the Sirocco the powder makes a 90 degree turn within the sampler, then transport via a tube to the cell (possible cross contamination). 2. The PowderJet maintains a constant mass flow rate by varying the feed rate to keep transmission constant. The Sirocco only controls the vibration feed rate. The sample concentration changes dramatically – decreasing the robustness of the measurement. See next slide.
If there are particles < 20 micron in the sample Malvern uses the fine powder powder. When the MS2000 uses Fine Powder mode, it cuts off all data above 250 micron.
This is real world data running a pharmaceutical excipient – magnesium stearate. Note the COV levels are extremely low, all fractions of a percent.
The LA-950 provides two error calculations Residual R and chi square. Both provide information of how the final calculation matches the raw data – a good indicator of how good the RI choice was. The chi square calculation also includes –
Results from analyzing the Whitehouse PS202 polydisperse standard. Great results.
Results from analyzing the Whitehouse PS225 polydisperse standard. Great results.
Results from analyzing the Whitehouse PS181 polydisperse standard. Great results.
These results come from mixing 2 standards 50/50 – good resolution and assignment of proportions.
More data showing the ability to resolve peaks with accurate proportions.
Resolution is the ability of the instrument to measure small differences in particle sizes. Resolution is difficult to specify, because it can have many possible meanings. In the case of the user, it would be most important to test a series of samples that track the variables of interest used to characterize the performance of the instrument for that specific use.
Perhaps the most important measure of resolution is how small a difference in the sample itself will generate a difference in the measurement. These changes may come from additional processing (milling or agglomeration) or to differentiate between different batches of material. Polystyrene Latex (PSL) NIST traceable standards are the easiest standards to use, but are significantly different from a vast majority of the materials manufactured and used in industry. This example does show the ability of the instrument to differentiate between a 553nm and a 600nm material.
This is an example of a mixture of three distinctly different size materials. Can the instrument identify that there are distinct distributions within the total sample? If so, are the relative amounts of the different components reported properly? Some companies have focused on tests to show closely spaced polystyrene latex as individual peaks in the overall distribution. As this example shows, it is possible, but the user must decide if this is a valid test of the ability of the instrument to respond to their samples.
This is another example of a mixture of three distinctly different size materials, but at a much larger size range. Instrument response can vary over the measurement range. Experiments should be designed to characterize performance in the range of the final application.
Resolution can also be the ability of the instrument to determine small amounts of a material outside of the main range of the sample, whether larger or smaller. A small amount of fines or coarse material can be a very important indicator of process problems. The ability to respond to these small amounts of material before they become a large contributor to the total particle distribution is a very important feature.
Precision is the ability of the instrument to get the same answer for the same material in repeat tests. The data shown was 24 samplings on one instrument. The data shows the precision of both sampling and instrument. Repeat measurements of the same sample in the instrument would characterize the precision of this one instrument.
USP <429> is a new pharmaceutical standard for using laser diffraction. This test has many similarities to ISO13320.
The USP <429> calculations are being written into the LA=-950 software. When released the user will have automatic pass/fail calculations and displays.
USP <429> also sets pass/fail criteria when analyzing a polydisperse standard to determine if the system is working properly. Measure the sample 3 times – to pass the accuracy the d50 must be within 3% of the certified value, and the d10&d90 must be within 5%. In addition, the test requires the user to calculate the COV for the 3 measurements and sets repeatability goals as shown in the slide.
This is just a screen shot from the development of the USP software. Customers will be able to choose from three options: Comply with USP<429> requirements Comply with ISO13320 requirements (more strict) Or create custom user defined requirements. This is why all customers will benefit from the software features.
Here is a screen shot form the software development showing an example where the accuracy was tested using a standard. The system passed at the d10&d90, but failed at the d50. This just an example, of course the units normally pass this test – see next slides.
Here are the accuracy & precision specifications for the LA-950, along with example data in the next slide. Does the competition talk about their specifications?
Here is data from 20 LA-950’s testing the instrument to instrument variation using polydisperse standards. Excellent results.
The last slides comes from customer data. They wanted to compare the reproducibility of the LA-910 to LA-950. This slide shows the protocol for testing the precision.
Here is the precision data for the LA-910. Two instruments were used in this study as shown in the protocol on the previous slide. Note: %RSD is the same as COV, just another name for the same calculation. These values are acceptable and would pass the USP<429> requirements.
Here is data from 6-8 different LA-910’s, testing instrument to instrument variability. This data is again acceptable.
Next, a similar study was performed using 2 LA-950’s. Notice the extremely low RSD values. EXCELLENT!
Finally, a study was performed on 4 LA-950’s. Notice the excellent RSD values. We expect this is the best in the business.