SAMPLING AND ANALYSIS OF COMMERCIAL FATS AND OILS
AOCS Standard Procedure Ck 2-09
Approved 2009
Determination of Various Properties of Biodiesel by the QTA® System Method
DEFINITION
This method provides a procedure for using the QTA System for rapid determination of a variety of properties of biodiesel using a QTA-specific infrared spectrometer that uses attenuated total reflectance (ATR). The QTA System maintains a proprietary database of calibration algorithms managed centrally, and accessed by individual method users via a secure website. The spectra of the biodiesel is collected on the local spectrometer, and then transmitted to QTA’s central database, where the algorithms are used for prediction. Results are then transmitted back to the user’s computer.
SCOPE
This procedure describes the method that QTA Users follow when analyzing a biodiesel sample using the QTA System. A validation procedure is included, as prescribed by QTA and followed by QTA Users. The scope of this procedure does not include the development of the calibration algorithms, which is done in a proprietary process by QTA.
Calibration development by FT-IR requires knowledge of chemometric principles. This method avoids calibration development by the user, by employing a single central calibration that is used by all users. The calibration installed on the QTA Server is the result of a comprehensive calibration development program using the prescribed ASTM D6751 method for each component or property. The QTA calibrations have undergone extensive validation and have been subjected to round robin studies, as described in an AOCS Collaborative Study Report. The spectrometer specifications and operating parameters are set by QTA, and the use of central calibrations, ensure that all users access the calibrations whose performance is documented in the Collaborative Study Report. The QTA participants of the round robin were required only to scan samples and report results; the wet chemistry labs used the prescribed ASTM or EN methods.
The QTA System method is applicable to a variety of biodiesel component analyses and properties. Predictions for moisture, methanol, total glycerin, and free glycerin content, as well as acid number and cloud point are included. The same method may be used for other biodiesel properties when additional calibration algorithms are developed, commercialized and validated by collaborative study. This method is applicable to biodiesel B100 samples that are homogeneous, derived from animal, vegetable and/or waste feedstocks. Non-homogeneous samples cannot be analyzed using this method. The feedstocks evaluated in this international collaborative study for B100 characterization by the QTA System included two soybean oils (separate facilities), two different canola oils (separate facilities), a blend of tallow and chicken fat, two blends of choice white grease, tallow, and poultry fats (same facility but separate batches), and two blends of soybean oil and poultry fat (same facility but separate batches).
APPARATUS
1. QTA –specific spectrometer, provided by QTA
2. Internet-enabled computer
3. Disposable plastic pipets
4. Soft white paper towels
REAGENTS
1. 50% solution of isopropyl alcohol in distilled water
PROCEDURE
1. Log on to www.qta.com
2. Enter your secure username and password and allow system to initialize
3. On the Select Material screen, select B100 NA
4. Select the properties to be analyzed by checking the appropriate boxes
5. Click Identify Sample to be taken to the Identify Sample screen
6. Enter your sample ID information
7. Click Analyze Sample
8. When prompted by the system, clean the sampling surface. Place one drop of the isopropyl alcohol solution on a soft white paper towel. Wipe the ATR crystal with the wetted paper towel. Use a dry section of paper towel to wipe the ATR crystal three times, using a clean dry section of paper towel each time.
9. After the ATR crystal is clean, click OK. The system will collect a background file.
10. When prompted by the system, place one drop of biodiesel on the ATR crystal. Ensure that there are no bubbles in the liquid on the ATR crystal.
11. Begin the analysis.
12. Results will be returned to the computer screen within less than one minute.
CHECK SAMPLES
It is recommended that at least once per week a reference sample having known values be analyzed on QTA. The known values should be generated by a QTA-approved laboratory that utilizes approved methods.
The check sample results returned by QTA should be within 2 standard deviations of the reference value. If it does not, QTA support should be contacted.
VALIDATION
Perform the validation protocol for each new QTA System, when there are any significant changes in feedstock, and annually thereafter. The validation verifies that the sample matrix is included in the QTA central calibration, by comparing the primary method results to the QTA results to ensure that the variability is less than two standard errors. The validation includes:
1. Upon start up, send at least 4 samples of biodiesel from 4 different batches to an approved QTA primary laboratory for primary method analysis. One additional sample will be required annually. Repeat when necessary or when there is a significant feedstock or process change.
2. Analyze an aliquot of each of the above samples on the QTA System.
3. Upon completion of the primary data analysis, the QTA results should fall within two standard errors of the primary result. If true, then the system is validated for use.
If false, then
1. Check the primary data and the QTA spectra for accuracy, and repeat the process defined in step 3.
2. Check the homogeneity of the sample. If non-homogeneous, discard the sample and data and re-validate with homogeneous sample.
3. QTA will adjust the calibration to include the additional sample matrix, provided that: (a) the standard error of the system does not increase; and (b) the error of the prediction results of the other QTA Systems does not exceed two times the standard error.
4. If none of the above enables validation, then the QTA System will not be validated for that facility/process/feedstock.
PRECISION
Table 1 is the list of fuel matrices evaluated in the validation of this Standard Procedure.
REPEATABILITY
The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within a short interval of time, will in not more than 5% of cases be greater than the values given in Tables 2–7. If the difference is greater than the limit indicated in Tables 2–7, obtain two other test portions. Analyze one as before and keep the other for a fourth determination if necessary. In this case, take as the result the arithmetic mean of the result obtained from the third analysis and the nearest result obtained from the previous analyses, provided that the difference does not exceed the allowed limit. Failing this, analyze also the fourth test portion and take as the result the mean of the four determinations.
REPRODUCIBILITY
The absolute difference between two single test results, obtained using the same method on identical test material in different laboratories by different operators using different equipment, will in not more than 5% of cases be greater than the values given in Tables 2–7. Table 8 contains the precision data generated by the ASTM D6708 statistical evaluation.
