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|For whom is the Serial Diluter intended?|
|The Serial Diluter is designed for users performing dilutions for the plate count method in microbiological testing. The instrument supports the lab staff by providing them perfectly diluted and mixed samples in bags for accurate and precise testing results in a very convenient way, 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 the lab bench where sample dilutions and plating are carried out.|
|What is a reasonable sample throughput?|
|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.|
|How does the serial diluter work?|
|The Serial Diluter works similar to a pipeting aid. Vacuum aspirates the desired amount of diluent and an excess pressure dispenses the diluent into the Serial Dilution Bag with the sample for direct radial mixing. 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.|
|What improvements can be achieved with regard to accuracy of testing?|
|With the Inlabtec Serial Diluter accuracy of the findings is independent of sample throughput, time pressure, unplanned working peaks, professional experience of employees, etc. This is accomplished by the user-friendly standardization of the dilution process which eliminates the individual differences in sample mixing and minimizes the risk of errors during pipetting, as well as by ultrapure sterile dilution bags, which guarantee the highest sensitivity in microbiological detection.|
|Can I use the Serial Diluter without personal demonstration?|
|Yes, the Serial Diluter is an out-of-the-box system and easy to install and use. As support we offer well illustrated operating manual including short instructions. In addition we have several demo videos showing installation and use of the Serial Diluter. Further, we offer advice and tips on how to best start working with the Serial Diluter in the lab.
Like every new equipment, it takes a short time to get used to it. Afterwards you don't want to give it anymore (see Customer Experience)
|What exactely is automated?|
|The Serial Diluter automates sample mixing and dilution in a Serial Dilution Bag compliant to ISO 6887-1. The following transfer for the next dilution step and the inoculation of Petri dishes has to be carried out manually by the user. This degree of automation keeps on one hand the investment costs low and on the other hand improves productivity and testing reliability without the need for process reorganizations and validations or for special trained personal.|
|How fast can I work with the Serial Diluter?|
|Examples: A serial sample dilution over three steps with the inoculation of two Petri dishes per dilution (total 6 Petri dishes) with 1 ml of diluted sample each and including insertion of the Serial Dilution Bags, requires one minute or the serial dilution over six steps, including insertion of the bags, requires one minute.|
|How is a homogeneous mixture ensured in the Serial Dilution Bags?|
|The Serial Dilution Bags were developed together with the Serial Diluter especially for homogeneous sample dilutions by direct radial mixing and are characterized as following:
1. The bags are divided into an addition and removal zone to avoid cross contamination with higher concentrated samples.
2. Opened Serial Dilution bags can be penetrated directly with the pipette tip for easy sample handling.
3. 45 ° bevels on the bottom ensure a targeted deflection of the pressurized diluent stream, which forms immediately a perfect vortex counter clockwise.
4. The rising air blast at the end of the diluent stream causes a sudden reversal of the rotation of the vortex for additionanal turbulences for a final, perfect mixing (see demo).
|How accurate can be dispensed?|
|The volume is determined by the position of the optical IR sensor on the pipette scale. Hence, the accuracy of the dispensed liquid depends on the accuracy of the scaling of the pipettes used. The sensor is insensitive to interfering light and 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 value of a set of individual values is to the wished set value. This deviation is also known as systematic errors. The precision indicates how close the individual measured values are to each other. The statistical measure is the standard deviation of this, often referred to as a random error.|
|When should the system be calibrated?|
|The accuracy of the 10 ml pipettes used should be checked before using a new pipette type, new pipette manufacturer etc. or when a new lot (batch number) of the pipettes is used to ensure that the specified accuracy of the pipette is maintained. The systematic errors of the pipettes can be determined by a calibration in order to compensate for the systematic error by the corrected sensor position (see Operation Manual, Chap. 9)|
|What kind of diluents and solvents can be used?|
|The liquids used must be compatible with the silicone hoses, the material of the 10 ml pipette used and with the polyethylene of the Serial Dilution Bags. There are no other limitations known concerning the diluents or solvents used in combination with the Serial Diluter.|
|Materials in contact with the diluent in the serial diluter?|
|The materials to which the diluent comes into contact are silicone, stainless steel, glass or Polystyrene (depending on the used 10ml pipette), polyethylene and polypropylene.|
|What guidelines and ISO standards have been considered in the development?|
|Serial dilutions with the Serial Diluter are compliant with ISO 6887-1 and its normative reference ISO 7218.
The product itself complies to the guidelines: 2006/42 / EC, 2004/108 / EEC. Standards: EN 61010-1: 2001, EN 61010-2-081: 2002 + A1: 2003 EN 61326-1: 2006th.
|Which chapter of ISO 6887-1:2017 is relevant?|
For a decimal dilution series for use in enumeration tests, transfer, using a pipette (6.5), 1 ml ± 0,02 ml of the initial suspension into a tube containing 9 ml ± 0,2 ml of sterile diluent at laboratory ambient temperature (unless otherwise stated in the specific standard). Mix thoroughly, preferably by using a mechanical stirrer (6.3) for 5 s to 10 s, to obtain a 10^2 dilution.
COMMENTS ON CHAPTER 10:
The tolerance allowable on final diluent volumes of ± 2% is respected by the Serial Diluter (see specifications). Instead of the preferable, but not mandatory mixing of the test tubes by a mechanical stirrer, direct radial mixing in especially mixing optimized Serial Dilution Bags is applied. This efficient mixing technique by adding of pressurized diluent to the sample followed by an air pulse leads to immediate rotational circulation of diluent and sample, causing a strong vortex and turbulences in the bags leading to standardized homogeneous mixing (see demo).
|How was the compliance with ISO standards checked?|
|The ISO 6887-1 compliance of the Serial Diluter has been initially verified during product development by the Zürich University of Applied Sciences (ZHAW Wädenswil) and further confirmed by ISO 17025 accredited Serial Diluter users in comparison to test tubes by analysing many different food samples (see selection of analyzed samples) as well as by the participation of these labs on interlaboratory tests (see results proficiency tests )|
|Is there a quality certificate for the serial diluter?|
|The CE certificate for serial diluter is in the operation manual.|
|From what material the bags are made?|
|The Serial Dilution bags are manufactured of high purity, virgin polyethylene (PE) under clean room conditions. The bags meet the EU regulations. No. 10/2011 from 2011/01/14, 1935/2004 of 2004/10/27 and 2013/2006 from 2006/12/22 as well as U.S. FDA 21, CFF 04, Title 21 (plastic materials and articles intended to come into contact with food).|
|How is the sterility of the Serial Dilution Bags ensured?|
|The Serial Dilution Bags are manufactured under the cleanest conditions according to DIN EN ISO 13485 for medical device manufacturers. During extrusion of the film, the film side for the inside of the Serial Dilution bags (which is relevant for the subsequent filling) is at no time in contact with the environment. The process is completely closed and the process temperature is 190 ° C, thus excluding any microbiological contamination of the Serial Dilution Bags inside. The subsequent assembly of the bags is carried on a welding machine under sterile laminar air flow, so that it can be done free of contaminations. The prefabricated Serial Dilution Bags fall directly in the dispenser box, removed from the machine and sealed in a heat shrinkable film.
After manufacturing the sealed dispenser boxes are supplied for irradiation to our sterilization service. The irradiation process is validated by dosimetry. This will ensure that there is always completely irradiated with the same dose. An independent test laboratory has demonstrated by a dosimetric and microbiological validation that no microbial growth is detected and the Serial Dilution Bags are completely sterile. The sterility of the produced Serial Dilution Bags is continuously monitored by an independent test laboratory.
|How does the opening of the bags work?|
|The bags are opened by using adhesion force of special micro structured silicone strips. If the adhesive force would be reduced due to e.g. dust particles on the surface of the adhesion grippers, the surface can be cleaned with 70 % ethanol and then the micro structured silicone is again fully functional. If not, the grippers can be peeled off and new seld-adhesive adhesion grippers 100015 can be simply attached again.|
|How I am certain that the set volume was actually dispensed?|
|The volume can be visually checked prior to dispensing, by simply reading the position of the meniscus of the liquid within the pipette. The intelligent sensor monitoring will ensure that dispensing is only released when the correct volume is present in the pipette. Deviations due to air bubbles, an empty bottle, etc. are recognized immediately and reported to the user via the display of the Serial Diluter. An internal pressure sensor also monitors dispensing and ensures the full release of the diluent. For example, if a pipette tip is clogged and the fluid cannot be delivered in the usual time, the process is interrupted and a message on the display informs the user.|
|What type of serological pipettes and graduated pipettes can be used?
|All known standard 10 ml plastic serological pipettes and 10 ml graduated glass pipettes can be used. Different pipette sizes are possible if the outer diameter of the pipette is between 8 - 15 mm and the total length between 150 - 350 mm.|
|How do I ensure that the Serial Diluter is functioning properly?|
|Check before starting dispensing the position of the meniscus within the pipette and watch for air bubbles in the Serial Dilution Bags indicating that dispensing is completed. If the position of the meniscus was correct and air was discharged for one second at the end of dispensing, the sample is properly mixed and diluted (see demo video).|
|What is the impact of the serological pipettes used on the accuracy of the Serial Diluter?|
|The volume-determining elements of the Serial Diluter are a standard pipette in combination with an optical sensor. As the Serial Diluter accurately dispenses the volume that is aspirated and determined by the meniscus position of the liquid, the accuracy of the dispensed volume depends on the accuracy of the pipettes’ graduation in use. The accuracy of the volume specified for serological pipettes in plastic is about ± 2 %, for glass measuring pipettes ± 0.5 % for Class AS and ± 1 % for class B.|
|How do I check the volume dispensed by the serial diluter?|
|The liquid dispensed is easiest checked with a balance (three decimal places), as frequently performed in the laboratory to verify other volumetric instruments: Liquid dispensed = weight of filled bag - weight of empty bag.
In the operation manual of the Serial Diluter is a detailed guide for the verification and a Excel-template for comfortable execution of the verification can be downloaded from inlabtec.com/resources. (download Excel template)
|How is the sterility of the system ensured for reliable operation outside a laminar flow cabinet?|
|In operation, the sterile liquid-carrying components consisting of a bottle with diluent, the tubing set, a 10 ml pipette and the dispensing nozzle are vented via sterile filters. Therefore no contaminants can penetrate into the system. Further, the Serial Diluter only dispenses sterile diluent and is unable to aspirate any liquid via the dispensing nozzle and if no dilutions are executed than the dispensing nozzle is parked in a protection sleeve. The measures taken effectively prevent contaminations for reliable operation on any lab bench for that installation in a laminar flow cabinet is not necessary.
After operation, all components of the Serial Diluter in touch with the liquid can be removed and autoclaved as easy as the tubing of a peristaltic pump. Information for sterilization is included in the operation manual.
|How can I test that all components used have been sterile and the delivered results are correct?|
|Before starting and after finishing the dilution work a sterility control can be performed. For that the first and last 9 ml dispense of a working series are used without samples and aliquots of these blanks are plated out for sterility controls.|
|What do I do if the system is not sterile?|
|A system not sterile does indicate that the diluent itself or the tubing set together with the dispensing nozzle were not completely autoclaved. As a control use for autoclaving an indicator strip which indicates completed autoclaving.|
|Can I have the serial diluter ready to stand overnight and continue the next day?|
|The serial diluter can be left to stand ready until the connected bottle or bag with diluent is empty. Since the dispensing nozzle is always flushed in one direction with sterile diluent and never comes into contact with the biological sample, contaminations of the dispensing nozzle by the sample are excluded. In addition the dispensing nozzle is always protected against external contaminations by the connected pipette tip or by a protection sleeve. As a further precaution, the dispensing nozzle can be parked in 70 % ethanol when not in use e.g. over the weekend. See details in the operation manual.|
|Are the sterile filters hydrophobic or hydrophilic and autoclavable?
|The filter housing is made of PP (polypropylene) and the membrane filter made of PTFE (Teflon). PTFE filters are hydrophobic and used for sterile vents, as the filter is not blocked by aqueous solutions. The filter manufacturer recommends a filter exchange after about eight autoclavation cycles. Make before each autoclaving a mark in one of the eight filter housing segments to maintain control.
|What maintenance and servicing is required?
|There is no mandatory maintenance or service needed. The instrument recognizes itself clogged filters, leaks, etc. and reports them to the user. Sterile filters and the adhesion grippers can be exhanged by the user (see operation manual)|
|Are there parts that must be replaced regularly?|
|According to manufacturer the sterile filters on the diluent bottles should be replaced after eight autoclave cycles.
The sterile filter on top of the Serial Diluter should be exchanged after six to nine month.
If the silicone tubing set changes its mechanical consistency after a few hundered autoclavtion cycles the tubing set has to be replaced.
|How is the service of the products guaranteed?
|The instrumentation was designed with sufficient reserve for heavy use and therefore requires minimal maintenance, which is limited to the replacement of the externally accessible sterile filter. In the case instrument repair is needed your exclusive Inlabtec distribution partner will immediately take care of the needed support and service work. All our distribution partners have equipment for immediate exchange available to guarantee that users can continue with their work within hours. Inlabtec is in close contact with its distribution for providing immediate support if necessary.|
|How do I clean the Serial Diluter?
|All components in contact with the diluent can be removed after use, cleaned and autoclaved. All surfaces of the instrument can be cleaned with commercially available cleaners / soap and water and disinfected with 70 % ethanol.|
|What are the system components which can be autoclaved?
|All liquid contact parts are fully autoclavable: tubing set, dispensing nozzle, connector cap GL 45 cpl, sterile filters|
|Can the system be used in a cold room?
|The serial diluter can be used at an ambient temperature of 4 °C to 40 °C.|
|Can I store the filled bags?|
|Used Serial Dilution Bags intended for disposal or storage can be stored in the Bagshell. Two Bagshells are included in the scope of delivery.|
|How high is the evaporation rate in filled bags compared to classical dilution tubes?|
|The evaporation rate in the refrigerator for filled (used) Serial Dilution Bags stored in Bagshells is in the range of capped standard dilution tubes. The evaporation rate is about 5 - 10 µl water per 24 hours.|
|How long is the shelf life of the Serial Dilution Bags?|
|The durability and sterility of the Serial Dilution Bags is guaranteed for five years at room temperature from manufacture if the box is sealed in the original protective film.|
|How long can an opened box with bags be used?|
|After removing the protective film from the packaging, it is recommended to use the Serial Dilution Bags within three months.|
|What are the optimal storage conditions for the bags?|
|Protected from sunlight at 10 - 30 ° C storage temperature. Maximum rel. humidity 50 - 60 %.|
|Do the Bags contain any substances that could inhibit bacterial growth?|
|The bags are made of high-purity, virgin polyethylene. No substances are present which could inhibit the growth of microorganisms in contrast to incompletely cleaned test tubes. See News: Cleaned test tubes not always clean enough?! from June 7, 2016.|
|What kind of pipette tips can be used?|
|All known 1 ml pipette tips can be used, as the serial diluter can be adjusted accordingly (see operation manual). To achieve highest speed and reliability in doing serial dilutions, we recommend to use the universal Inlabtec LO pipette tips with a nozzle diameter of 1.9 mm (standard tips: 0.7 - 0.8 mm). The large opening reliably prevents clogging by particles in the food sample and ensures the highest possible processing speed.|
|What are the savings using the Serial Diluter?|
|Cost and time savings are realized by eliminating the preparation of test tubes or by eliminating 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.|
|What can be omitted in the preparation work for serial dilutions?|
|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.|
|How big is the energy consumption for the production of the Serial Dilution Bags?|
|The energy demand for the production of 1’000 Serial Dilution Bags is approximately 20 MJ. About 8 MJ (40 %) will be recovered in the waste incineration for heat and electricity production if the material is not recycled. Therefore the net energy demand is about 12 MJ for 1’000 Serial Dilution Bags. For comparison: A wash with a dishwasher needs about 5 - 7 MJ of energy, a 50 l autoclave consumes about 10 - 15 MJ per cycle. Therefore, cleaning and autoclaving of the test tubes needs more energy as the use of the one-way Serial Dilution Bags even if the Serial Dilution Bags cannot be recycled.|
|Is it ecologically sensible to use Serial Dilution Bags?|
|In our view, it is very useful to use Serial Dilution bags instead of glass tubes.
- The waste weight and volume produced by the use of the bags is minimal. For comparison: a shopping bag of medium size made of plastic corresponds to about 150 - 200 Serial Dilution Bags
- The energy consumption for the cleaning and sterilization of test tubes is higher than the energy demand for the production, use and disposal of Serial Dilution Bags (see above)
- Highest grade, virginal PE is a valuable energy storage free of pollutants, which is used in its combustion for energy production or which can be recycled
- The bags are stored at room temperature, therefore no space is needed in the refrigerator/ cold room
- The weight for transportation is about 16 x lower than for standards test tubes
|Is the supply secured with Serial Dilution Bags? How long are the delivery times?|
|We always have sufficient quantities of bags in stock and the target delivery is within five working days for a order. Due to the low storage capacity and low costs, it is advisable to have bags on stock for about four weeks to exclude problems with possible delays in transport, customs, etc.|
|How much space is saved with Serial Dilution Bags?|
|A box with 1'000 Serial Dilution Bags requires a storage volume of about 2.5 liters. For 1’000 prepared dilution tubes about 74 liters are needed.|
|How long is the warranty period?|
|The warranty period for all equipment components is two years. Details can be found in our terms and conditions on our website.|