Near Infrared protein analyzers have become a fixture in today’s agricultural business. The popularity and success of the NIR technique has led to a situation where companies make critical decisions based upon the information supplied by these instruments. Decisions on purchasing, payment, sorting, binning, blending and load-out are commonly based on the results supplied by NIR instruments.
No longer is it simply moisture or protein that is of interest, but other traits such as oil, fiber, starch and softer "quality" parameters are often analyzed with NIR instruments. Therefore data integrity and accuracy are critical to the success and long-term profitability of these decisions.
Recent developments in NIR technology help improve results and accuracy at both a hardware and user level, thus allowing even greater possibilities of control.
DIODE ARRAY TECHNOLOGY
The DA7200 from Perten Instruments is one of these new breeds of NIR technology. The DA7200 is the second-generation diode array based NIR analyzer from Perten.
The primary hardware differences from past technology are in the design of its optical bench. Traditional scanning instruments use a moving optical grating and a narrow slit passing sequential wavelengths of light onto a detector — thus the term scanning. A single spectrum/scan is collected in most instruments in about 45 seconds. Diode array technology allows the use of a stationary wavelength grating. The grating spreads the "light" (similar to a prism) onto a series of diodes or pixels. Each pixel represents an individual wavelength. In this way, it acts similar to a digital camera in that it collects all information simultaneously as opposed to sequentially.
A single spectrum is collected in about 15 milliseconds. It measures whole grain as well as intermediate products such as mash and slurry, and it is configured so that multiple products can be measured without changes to the instrument hardware setup.
ENHANCED SYSTEM ACCURACY
The optical benches of diode array based spectrometers are mechanically simple in that there are no moving optical components in the analyzer. This allows for accurate and reproducible production of spectra and, thus, analytical results. The improved optical accuracy makes development and subsequent transfer of calibrations simpler.
Instrument accuracy is often the only source of error taken into account, but there is an equally important and often greater source of error — operational or procedural errors caused by the user.
Operators can often influence test results. For example, sample cups/cells can have several sources of error, including variability from cell to cell or damage. But the largest source is of variability in packing the samples.
The DA7200 employs a pour-and-place design to remove that source of error. The sample is poured into an open-faced dish and placed under the instrument. When an analysis is performed the dish is rotated to present a large surface area for analysis — very important for analysis of heterogeneous products such as grains and feeds. The data collection speed allows the instrument to take advantage of averaging many results in a short time. The averaging effect provides a more accurate result.
The DA7200 also incorporates an in-line emission source that automatically monitors wavelength accuracy and corrects the wavelength scale if necessary.
Through use of the open-faced sample dish, there is no sample-to-instrument contact, thereby reducing possibilities for cross contamination of results by poor cleaning.
The analysis area of the DA7200 is 108 cm2 thus improving accuracy on non-homogen-eous products.
FASTER ANALYSIS AND SAMPLE THROUGHPUT
Overall analysis speed depends on two aspects: spectrometer speed and sample handling requirements. The DA7200 provides results in 3 seconds or less. The result is an average of approximately 300 individual readings. The open architecture and design of the DA7200 allows for enhanced sample throughput by speeding up the sample presentation and cleanup steps. The practical usage process — from opening a sample container, pouring out the sample into the dish, accessing the software on the instrument, actual analysis and placing the sample back into its container or throwing it away — results in a 15 to 20 second total analysis time. The sampling system requires no sample preparation, such as grinding, and since there is no sample-to-instrument contact, there is relatively little cleanup required, even on sticky, greasy or wet samples. The speed of analysis allows for not only quicker results but significantly greater sample throughput.
The DA7200 addresses reliability and maintenance in several ways. The stationary grating provides a stable, reliable optics bench, resulting in a sturdy instrument platform.
Most NIR instruments, including the DA7200, use a similar style of tungsten halogen lamp as the light source. However, the new design of the DA7200 improves energy throughput and allows the lamp to be run at lower power, thus increasing its lifespan. A user replaceable spare is located in the instrument housing to further reduce downtime and maintenance costs. The software and user interface operate under the Windows XP platform, enabling the instrument to be contacted remotely for technical diagnostics, calibration updates, transfer of data, or software upgrades.