Reflectoquant® Lipase Test, Catalog No. 5851/1
1. Method
Lipases convert a specific substrate to form a blue dye, the concentration of which is
determined reflectometrically.
2. Measuring Range and Number of Determinations
| Measuring Range |
Number of Determinations |
| 10 - 400µg/l H1) |
50 |
| 4 - 160U/l |
1) relative to lipoprotein-lipase from Pseudomonas (400U/mg, acc. to the certificate
of analysis for Merck KGaA, Darmstadt, Germany, Cat. No. 1.05389.0001) at 25°C.
3. Applications
Sample Material:
Foods, e.g. milk and dairy products, cereals, and cereal products
Biological samples (not for clinico-chemical diagnostics)
4. Influence of Foreign Substances
This was checked in solutions containing 200µg/l lipase.
The concentrations of foreign substances given in the table lie below the limit at which the
determination is interfered with:
| Concentrations of Foreign Substances in mg/l or % |
| Ascorbic Acid |
10 |
Benzoic Acid |
0.25% |
| Cr2O72- |
100 |
Urea |
5% |
| Formaldehyde |
200 |
NaCl |
1% |
| H2O2 |
100 |
Saccharose |
5% |
| I2 |
1 |
Sorbic Acid |
1% |
Foreign activities in milk were tested using esterase from porcine liver. 100µg/l esterase yields
a signal corresponding to approximately 13µg/l lipase.
5. Reagents and Auxiliaries
| The analytical test strips are stable up to the date stated on the pack when stored
in the closed tube at +2 to +8°C. |
| Protect strips and reagents from light! |
Package Contents:
Tube containing 50 analytical test strips 1 Bar code strip "Lipase Milk"
1 Bar code strip "Lipase" 2 bottles of reagent Lip-1 1 bottle of reagent Lip-2
6 semi-microcuvettes
Accessories:
Block heater or water bath (25°C) or thermometer for the measurement of the ambient
temperature
Variable pipette for 1ml and 250µl volume
Disposable test tubes for the dilution of the samples
Stop-watch
Note: The bar code strip "LIPASE-MILK" requires the RQflex 2 instrument. This bar code
strip will not work in the older RQflex instruments.
6. Preparation
- Adjust the reagents Lip-1 and Lip-2 to room temperature (20-25°C) prior to
measurement
- For liquid milk samples use the bar-code strip "Lipase Milk" only; for all other samples
use the bar-code strip "Lipase"
- Extract solid sample materials by an appropriate method
7. Procedure
Observe the instructions for the RQflex
Reflectometer. The following applies to the Lipase Test:
Measurement procedure A Stored reaction
time: 5 sec.
- Fill reagent Lip-1 into the bottom part of the semi-microcuvette (0.8-1ml or approximately
40 drops, respectively) and adjust to 25°C (e.g. in a water bath)
- Place 0.25ml of sample solution and 1ml of reagent Lip-2 in a disposable test tube
and mix (dilution 1:5)
In the case of raw milk, mix 0.1ml of sample solution and 1ml of
reagent Lip-2
- Remove 1 analytical test strip and immediately reclose the tube.
- Immerse both reaction zones of the test strip in the test tube containing the
diluted sample solution for approximately 2 seconds
- Vigorously shake off excess liquid from the test strip
- Within 10 seconds, place this test strip in the semi-microcuvette containing the
pretreated and 25°C warm reagent solution and start stop-watch
- After 15 minutes, remove the test strip immediately and vigorously shake off excess
liquid
- Switch on the RQflex reflectometer and press the START button once, then insert
the test strip all the way into the strip adapter with the reaction zones facing the display
- Immediately press the START button again. After the reaction time has elapsed,
read off the result from the display in µg/l lipase.
The result is stored automatically.
8. Evaluation
If the sample is analyzed at a temperature other than 25°C, it is necessary to correct
the displayed result by a corresponding factor:
Temperature (°C) |
Correction Factor |
Temperature (°C) |
Correction Factor |
| 15 |
2.2 |
23 |
1.2 |
| 16 |
2.05 |
24 |
1.1 |
| 17 |
1.9 |
25 |
1.0 |
| 18 |
1.75 |
26 |
0.9 |
| 19 |
1.6 |
27 |
0.85 |
| 20 |
1.5 |
28 |
0.8 |
| 21 |
1.4 |
29 |
0.75 |
| 22 |
1.3 |
30 |
0.7 |
The lipase values shown in the display are valid for UHT milk with 1.5% fat.
For other types of milk, as well as for milk with a fat content other than 1.5%, it is necessary
to correct the displayed result by a corresponding factor:
Fat Content (%) |
Raw Milk |
UHT Milk |
Pasteurized Milk |
| 0 |
1.4 |
0.6 |
0.8 |
| 0.5 |
1.5 |
0.7 |
0.9 |
| 1.0 |
1.5 |
0.9 |
1.0 |
| 1.5 |
1.5 |
1.0 |
1.2 |
| 2.0 |
1.6 |
1.1 |
1.3 |
| 2.5 |
1.6 |
1.3 |
1.4 |
| 3.0 |
1.6 |
1.4 |
1.5 |
| 3.5 |
1.6 |
1.5 |
1.6 |
| 4.0 |
1.7 |
1.7 |
1.7 |
| 4.5 |
1.7 |
1.8 |
1.8 |
| 5.0 |
1.7 |
2.0 |
2.0 |
|