Systems for serial dilution in bags
In 2014, Inlabtec launched the Serial Diluter TA, the first system for serial microbiological sample dilution in bags (patented). This was followed by the Serial Diluter SA, which allows the use of pipette straws instead of 1 ml pipette tips. The Serial Diluter UA has been developed and launched due to the customer need to be able to freely use any type of pipette, including filtered pipette tips.
Read more about the individual models and their special features below.
Serial Diluter UA
Connect the diluent and a 10 ml pipette, insert bags and start diluting! The new Serial Diluter UA with integrated mixer and intelligent process monitoring guarantees reliable and efficient dilution of samples for viable cell counts.
The procedure is 100 % identical to the ISO method – instead of pipetting into a test tube filled with 9 ml of Diluent, pipette into a filled bag. The Serial Diluter UA is available in six or twelve-stage versions.
Videos Serial Diluter UA
Prices and scope of delivery Serial Diluter UA
Specifications Serial Diluter UA
Serial Diluter Demo Request
Serial Diluter TA
With the pioneer model Serial Diluter TA, the sample is placed in the bag together with the tip. The diluent then rinses the sample from the tip followed by a sterile air blast into the bag.
This proven method works reliably with all samples examined in a food control laboratory. The Serial Diluter TA is also available in six or twelve stage versions.
Please note that in contrast to the Serial Diluter UA, no pipette tips with filter can be used for diluting. The reason for this is that the diluent must flow unhindered through the pipette tip.
Videos Serial Diluter TA
Prices and scope of delivery Serial Diluter TA
Specifications Serial Diluter TA
Serial Diluter Demo Request
Serial Diluter SA
The method of operation is the same as with the Serial Diluter TA: Place the sample together with the straw tip into the first bag and attach the dosing arm for automatic dilution – it’s as simple as that! Like the Serial Diluter TA, the Diluent flows through the pipette straw for mixing and diluting.
Videos Serial Diluter SA
Prices and scope of delivery Serial Diluter SA
Specifications Serial Diluter SA
Serial Diluter Demo Request
Q&A about Serial Diluters
For which laboratories is the Serial Diluter intended?
The Serial Diluter is designed for users performing dilutions for the plate count method in microbiological testing of food, feed, cosmetica, etc.
The instrument supports the lab staff by providing them homogeniously diluted and mixed samples for accurate and precise testing results. Using it is very convenient, absolutely reliable and with nearly no prior work preparation. The instrument has the footprint of a vortex mixer and a test tube rack and can be placed on any existing lab bench where sample dilutions and plating are carried out.
For what sample throughput is the Serial Diluter wort using?
Testing labs having an average daily throughput of 30 samples for serial dilutions, the Serial Diluter will be normally amortized in about one year depending on the costs for the preparation of test tubes or the costs for prefilled ready-to-use dilution tubes or cups.
What do I save in costs and time using the Serial Diluter?
Cost and time savings are realized by eliminating the preparation of test tubes or the expensive pre-filled dilution tubes, by faster carrying out the dilutions as no manual vortexing and no handling of tubes and caps has to be performed, by reduced costs for transport, storage and disposal of the consumables.
Does the Serial Diluter improve the reliability and accuracy of test results?
With the Serial Diluter, the accuracy of the testing results is ensured regardless of sample throughput, time pressure, unplanned work peaks, employee experience, etc. The figure below shows the evaluation of interlaboratory tests with the Serial Diluter in comparison to the test tube method. With the Serial Diluter, all employees of the laboratory achieve z-score values of ± 0.1, i.e. all employees, regardless of their level of experience or individual differences in working technique, delivered almost identical test results.
How is the exact amount of diluent dispensed?
The Serial Diluter works similar to a pipeting aid. Vacuum aspirates the desired amount of liquid and an excess pressure dispenses the liquid into the Serial Dilution Bag with the sample. The aspirated volume is determined by an optical sensor placed on the side of a 10 ml pipette. Thus, the optical sensor simply replaces the human eye in the determination of the volume making the use of the Serial Diluter even simpler as of a pipeting aid.
Which steps are simplified with the Serial Diluter?
The Serial Diluter automates dilution and mixing with easy integration into existing workflows. No specially trained staff is required and the workflow continues as before. In addition, the cost of purchasing and maintaining the Serial Diluter is low.
Can I use the Serial Diluter without any training?
Yes, the Serial Diluter is very easy to install and use. The operating instructions are also illustrated in detail and various training videos are available in the section Support of this websiet.
What materials does the diluting solution in the Serial Diluter come into contact with?
The diluting solution comes into contact with silicone, stainless steel, glass or polystyrene (depending on the 10 ml pipette used), polyethylene and polypropylene.
Which directives and ISO standards were taken into account in the development of the Serial Diluter?
Serial dilution with the Serial Diluter complies with the standard method according to ISO 6887-1:2017 and the associated normative reference ISO 7218:2007.
The product is subject to the technical directives: 2006/42/EC, 2004/ 108/EEC. Normen: EN 61010-1:2001, EN 61010-2-081:2002 + A1:2003, EN 61326-1:2006.
How was compliance with the standards verified?
The serial dilution with the Serial Diluter was verified against the standard technique with dilution tubes according to ISO 6887-1 by the Zurich University of Applied Sciences (ZHAW Wädenswil). In addition, the Serial Diluter was tested by ISO 17025 accredited users of the Serial Diluter on the basis of direct comparisons with the test tube technique using various food samples (see test results Campden BRI). These accredited laboratories regularly take part in proficiency tests, which confirm the consistently high accuracy and reliability of the Serial Diluter (see Labo 11/2017).
Is there a quality certificate for the Serial Diluter?
The CE-certificate for the Serial Diluter is in the manual.
How is the sterility of the system ensured?
All parts in contact with the liquid are autoclavable. During operation, the system is ventilated via sterile filters to secure sterility. Since the Serial Diluter only dispenses sterile liquid and never aspirates liquid through the dispensing nozzle, the system sterility is efficiently ensured.
Are the sterile filters used hydrophobic or hydrophilic and are they autoclavable?
The PTFE (Teflon) filters used are hydrophobic and autoclavable. Difference between hydrophobic and hydrophylic filters: Trainings video
Attention: Do not install hydrophilic filters on bottles with diluent or on the Serial Diluter.
How fast can I work with the Serial Diluter?
The dilution of a sample added into a bag is made in approx. 3 seconds.
In other words: A serial sample dilution over three steps with the inoculation of two Petri dishes per dilution step (total 6 Petri dishes) takes about one minute.
What can be omitted if preparing decimal dilutions for plate counts?
Beside no handling of test tubes and cups as well as no manual vortex mixing for 5 s to 10 s, no test tubes have to be cleaned, dried, filled, sterilized and stored. Accordingly, time savings and savings of water, electricity and cleaning agents if Serial Dilution Bags are used. Also the need for storage space and cooling space is reduced by a factor of 20 to 30. Investment and maintenance in autoclaves, washing dishes and dispensers are lower because less operating cycles, wear, smaller equipment, etc.
What maintenance and service is required for the Serial Diluter?
There is no need for regular maintenance and service. The instrument itself detects e.g. clogged filters, leaks, etc. and reports these to the user. Maintenance is limited to changing the easily accessible filters and adhesion grippers.
How is the service of the products ensured?
Inlabtec products are sold through authorised distributors, who can perform all service work. The Serial Diluter is based on very solid, proven technology, which keeps service work to an absolute minimum.
What maintenance and service is required?
There is no need for regular maintenance and service. The instrument itself detects e.g. clogged filters, leaks, etc. and reports these to the user. Maintenance is limited to changing the easily accessible filters (see next question)
How reliable works the opening of the Serial Dilution Bags? Is there wear and tear?
A microstructured silicone is used to open the Serial Dilution Bags wear-free. If the adhesive force would decrease due to dirt, the adhesion gripper can be cleaned with water, 70 % ethanol, etc. and is then functional again. If not, the gripper can be removed and a new, self-adhesive adhesion gripper can be attached (see operating instructions).
Are there components that need to be replaced regularly?
According to the filter manufacturer, the sterile filters of the bottles containing the diluting solution should be replaced after eight autoclaving cycles. The sterile filter on the unit should be changed every 6 – 9 months.
How do I clean the Serial Diluter?
The liquid-bearing parts can be removed from the Serial Diluter after use, cleaned and autoclaved. The device surfaces can be cleaned with a commercial cleaner/soap water and disinfected with 70% ethanol.
Which system components can be autoclaved?
All parts in contact with the liquid can be steam sterilised: tubing set, dosing tip, connection cap GL 45 kpl, as well as the sterile filters.
How long is the warranty period of the Serial Diluter?
The warranty period for all device components is two years. Details can be found in our AGB (General Terms and Conditions).
How precisely can be dispensed with the Serial Diluter?
The volume is determined by the position of the optical IR sensor on the pipette scale. A set volume of 9 ml is dispensed with an imprecision of max. ± 0.6 %.
What is the difference between accuracy and precision?
Accuracy indicates how close the average actual value, i.e. the mean value, is to the target value. The deviation is also called systematic error. The precision indicates how close the individual measured values are to each other. The statistical measure of precision is the standard deviation, often called random error.
Under which conditions should the dispensed volume be checked and calibrated?
The accuracy of the pipettes used should be checked before using a new pipette type/pipette manufacturer or a new lot (batch number) of the pipettes used to ensure that the specified accuracy of the dispensed volume is maintained. The systematic error of the pipettes can be determined by calibration (check) and compensated for by the corresponding sensor position ( see Operating Manual chapter 9).
How can I be sure that the set volume was actually dispensed?
The volume can be checked visually before dispensing by reading the meniscus in the pipette. The sensor monitoring of the aspirated liquid ensures that dispensing of the liquid is only released when the correct volume is available in the pipette. Deviations caused by air bubbles, an empty bottle, etc. are detected immediately and reported to the user via the display. The internal pressure sensor also monitors the dispensing and ensures complete delivery of the dilution solution.
Which serological pipettes and graduated pipettes can be used with the Serial Diluter?
All 10 ml serological pipettes and graduated pipettes in the standard version can be used. Other pipette sizes are possible as long as the outer diameter of the pipette is between 8 – 15 mm and the length between 150 – 350 mm.
How do I make sure that the diluter is working properly and that the dilution was done correctly?
Simply briefly check the position of the meniscus before you start the dilution by pressing a button and pay attention to the air bubbles after dispensing the liquid. If the position of the meniscus is correct and air is released at the end of the dispensing, the sample is correctly diluted.
What influence do the serological pipettes used have on the accuracy of the Serial Diluter?
The volume determining element in the Serial Diluter is a pipette in combination with an optical sensor. Since the Serial Diluter dispenses exactly the volume that is aspirated into the pipette and indicated by the meniscus position of the liquid column, the accuracy of the dispensed volume depends on the accuracy of the scale / graduation of the pipette used. The inaccuracy of the volume indication of serological pipettes made of plastic is approximately ± 2 %, for graduated pipettes made of glass ± 0.5 % for class AS and ± 1 % for class B.
How do I check the volume dispensed by the Serial Diluter?
Volume testing of the dispensed liquid is most easily done with a measuring cylinder or with a balance, as is often done in the laboratory to check volume measuring devices. Dispensed liquid = weight of filled bag – weight of empty bag. The Serial Diluter manual contains detailed instructions for checking and the corresponding Excel template can be downloaded from.
How can I test whether the components used were sterile and the results obtained are correct?
A sterility check can be carried out before the actual start of work and at the end of the work. For this purpose, the first and last 9 ml dispensing is carried out without sample and one sample each is used for sterility control.
What do I do if the system is not sterile?
If the system is not sterile, it can be assumed that the bottle with the diluting solution or the tubing set with the dosing tip has not been completely autoclaved. For reliable sterilization of the tubing set and dosing tips in autoclaves, sterilization bags with a paper layer should be used to ensure the penetration of steam.
Can I leave the Serial Diluter operational overnight and continue working the next day?
The Serial Diluter can be left operational until the connected diluent is used up. Since the dosing tip is always flushed with sterile diluent in one direction only and never comes into contact with the sample, contamination risk of the dosing tip and diluent is very low. The dosing tip is shielded from the outside by the integrated protective sleeve. As an additional precautionary measure, the dosing tip can be parked in 70 % ethanol when not in use for a longer period of time, e.g. over the weekend. For details please refer to the operating instructions.
Can the system be operated in the sterile bench and UV-sterilized overnight?
The Serial Diluter can be operated in a sterial bench, laminar flow, etc. and the device is UV-resistant for regular surface sterilisation.
Which pipette tips can be used with the Serial Diluter TA?
Practically all known 1 ml pipette tips can be used, as the Serial Diluter can be adjusted accordingly. However, due to the speed and reliability of the process we recommend the use of our universal LO pipette tips with a wide opening (standard tips: 0.7 – 0.8 mm).
More information on how to use our products can be found in Support.