ELISA Troubleshooting

FAQs

Please check out our FAQs below. If you don't see an answer to your question, please feel free to contact us.

Purified Allergens

Allergens on-Demand Videos

Check out our on-Demand videos about purified allergens. Dr.Sabina Wünschmann, Head of Allergen Manufacturing, R&D discusses advantages of using purified allergens, and provides insight into Indoor Biotechnologies Allergen Manufacturing processes. The 11 minute videos highlights Pros, Cons, and applications of natural and recombinant allergens.

            

How should allergens be stored?

Allergens should be stored frozen in a -20ºC freezer.

How are allergens purified?

The purification protocol varies for different allergens. We use affinity chromatography, ion exchange, hydrophobic interaction and size-exclusion chromatographic methods for purification of natural, recombinant and LoTox™ allergens.

In which buffer is the allergen supplied?

Our natural and recombinant allergens are supplied in preservative-free and carrier-free phosphate buffered saline, pH 7.4 and are sterile filtered.

LoTox™ allergens are supplied in Preservative and carrier-free sterile, endotoxin-free, phosphate buffered saline, pH 7.4.

MARIA® - General/Technical

What is MARIA®?

The Multiplex Array for Indoor Allergens (MARIA®) combines Indoor Biotechnologies proprietary panels of monoclonal antibodies with the Luminex xMAP® multiplexing technology. MARIA® technology uses polystyrene microspheres that are internally dyed with distinct fluorophores to create as many as 100 distinctly coded bead sets. Capture antibodies are covalently coupled to different bead sets and then used to develop quantitative immunoassays using biotinylated detector antibodies and a reporting fluorophore. Kits can be pruchased with magnetic or non-magnetic bead sets.

Up to 12 common allergens of dust mite (Der p 1, Der f 1 and Mite Group 2), cat (Fel d 1), dog (Can f 1), mouse (Mus m 1), rat (Rat n 1), cockroach (Bla g 2), Alternaria (Alt a 1), Aspergillus (Asp f 1) and the pollen allergens of birch (Bet v 1) and timothy grass (Phl p 5) can currently be measured simultaneously using this technology. The detection panel is continuously being enlarged to include other allergens, such as food allergens and other molds.

MARIA® offers major advantages compared to ELISA such as the time savings achieved by analyzing multiple allergens at once, as well as improved sensitivity, accuracy and reproducibility.

Should I choose non-magnetic or magnetic beads for my kit?

Depends on your available instrumentation for use with the Multiplex Array for Indoor Allergens (MARIA®).

Storage temperature of the kit?

Upon receipt of the MARIA® kit it is important that all reagents, except the standards and quality controls (QC-MRA-L and QC-MRA-H), are stored in the refrigerator at 4°C. Freezing will damage the microspheres, BI-MRA and SAP-MRA reagents. The standards and quality controls should be stored frozen at -20°C, unless used immediately.

Expiration date?

The kit will be under warranty for 6 months upon receipt, provided that it has been stored correctly.

Can I receive training on using the MARIA kits?

Yes. We offer biannual training courses at our facility in Charlottesville, VA. Please check our website for more information. We also offer custom training in MARIA® on a year-round basis.

MARIA® - Sample Collection/Preparation

What types of samples can I test with MARIA?
How do I collect a sample?
How do I prepare a sample to run on a MARIA plate?
How should I store my sample(s) if I cannot run them on MARIA right away?

Dust samples and air filters prior to extraction should be stored in a dry place at room temperature. Dust and air filter extracts should be stored frozen in a -20C freezer.

What allergen extraction protocol do you recommend for dust or air samples?

Please see Sample Extraction Procedure.

A1:If using the DUSTREAM™ and sampling for the recommended area and time yields very little or no dust, continue sampling until the filter is 1/4 full.  Our allergen results are not based on area, but on microgram of allergen per gram of dust.

A2:For allergen extracts or extracts of bulk dust or air filters, we need a minimum of 0.5 mL, especially if testing for multiple allergens.

A3:For air sampling cassettes, the whole filter is extracted with 1ml of PBS extraction solution and the results are reported as ng or µg allergen per filter.

Do I need to sieve dust samples?

Whether to sieve the dust or not is determined by the quality of the dust. We do not routinely sieve dust collected from beds and soft furnishings. Carpet samples are sieved (e.g. using a No.45 mesh screen, 355um diameter sieve) to separate the fiber and large particles from fine dust. We recommend the use of the DUSTREAM™ collector which greatly reduces the need for sieving dust. After collecting a dust sample using the DUSTREAM™ collector, remove the nylon filter containing the dust sample insert, invert the filter and tap the dust onto a piece of weigh paper. The fine dust falls before the fibers come out of the filter.

MARIA® - Protocol

Use of Bovine Serum Albumin (BSA)
Is it necessary to sterilize filter the assay buffer?

Yes! Unfiltered assay buffer has a high particle load that will interfere with measurement in the xMAP sytem. It will cause high bead aggregation ratios and may increase the time it takes to read the plate 3-4-fold.

How many samples can I analyze on one MARIA plate?

Depends on the number of dilutions per sample. Typically we run three dilutions per sample which means that 21 samples plus a duplicate sample can fit onto single MARIA plate.

Is it necessary to centrifuge samples to run in MARIA?

Yes. The MARIA® is a bead-based assay. Therefore, it is important to minimize the number of foreign particles in the sample by centrifuging all samples prior to plating.

Should the entire protocol be completed in one day?

The entire MARIA protocol requires that it be completed in a single day.

What sample dilutions should I use?

The recommended sample dilutions depend on the kind of sample you have and the level of sensitivity you require for your study:

For house dust extracts, we recommend diluting samples at 1/10, 1/100 and 1/10,000. This will give you access to lower limits of detection between 0.1-0.9ng/mL (equivalent to 0.002-0.012µg/g dust).If you do not need such high sensitivity, dilute samples only at 1/100 and 10,000 for sensitivity levels of 1-6ng/ml (0.02-0.12µg/g dust). This will allow you to assay 35 samples per plate.

Air filter extracts contain much lower allergen concentrations. We generally assay these samples undiluted, at 1/10 and 1/50.

How do I prepare serial dilutions?

A1: For serial dilutions of 1/10, 1/100 and 1/10,000: 

Prepare three microcentrifuge tubes per sample. Add 10µL of sample to 90µL of assay buffer for a 1/10 dilution in tube 1. Mix by vortexing. Add 90µL assay buffer into tube 2 and transfer 10µL of the 1/10 dilution (tube 1) into 90µL assay buffer. Mix by vortexing. Add 990µL of assay buffer into tube 3 and transfer 10µL of the 1/100 diluted sample from tube 2 into tube 3. Mix by vortexing. 50µL of each prepared dilution are used in the MARIA® assay.

A2: For serial dilution of 1/10 and 1/50:

Prepare two microcentrifuge tubes per sample: Add 90µL of assay buffer into tube 1 and add 10µL undiluted sample. Mix by vortexing. Add 80µL of assay buffer to tube 2 and transfer 20µL of diluted sample from tube 1 into tube 2. Mix by vortexing.

Can I use an ELISA plate washer for MARIA plates?

No. Inverting the plate or rinsing of the wells will wash away the microspheres. All washing steps have to be performed by filtration using a vacuum manifold and the filter plate provided with the kit.

Does the MARIA plate need to shake during incubations?

Yes and No. Before every incubation step of the assay, beads and reagents need to be mixed thoroughly by either vigorous pipetting or by rocking the plate during incubations. Either method will sufficiently mix your plate and there will result in no noticeable difference in the results.

Does the MARIA plate need to incubate in the dark?

All incubations have to be performed in the dark, otherwise the microspheres may lose their distinguishable fluorescent label. We generally cover the plate with the lid provided and place it in an empty drawer during the incubation periods or place the plate on a plate rocker under an opaque cover.

How many beads per analyte should be specified in the protocol?

We recommend counting 100 beads per analyte for maximum reproducibility.

What curve fit should I use?

We use a 5 parameter logistic (5PL) curve fit. (The fit can be chosen easily in the Bio-Plex Manager software.)

MARIA® - Interpreting Results

How do I determine the usable part of the standard curve?

A1: If the Fluorescent Intensity (FI) of the low end of the curve is close to the FI of the Blank, do not use values that fall within the FI of the Blank plus three times the Standard Deviation of the Blank.

A2: We generally do not use data that fall within the FI of the top flat part of the curve. This means that we normally exclude the top 2-3 points of the curve for Der p 1, Der f 1, Der p 2, Fel d 1, Can f 1, Rat n 1 and Mus m 1. The top part of the Bla g 2 curve is usable, whereas the 3-4 lowest points are too close to the blank (see above).

A3: Some software packets, such as the Bio-Plex Manager® (Bio-Rad, Hercules, CA) automatically show the ratio between expected and observed standard values in the exported Excel file. We use this function as additional quality control and only use values, where the observed/expected ratio is within 15% of 100%.

A4: The coefficient of variance (CV%) between duplicate standards should not exceed 15%. If this is the case, the accuracy of your pipettes and pipetting procedures should be checked.

Instructions for MARIA data processing
I get different results for each sample dilution. How do I choose the correct result?

Depending on the allergen concentration in your sample, you may get different results for different sample dilutions. There are a number of criteria that determine which result to choose:

Only select results that fall within the usable MFI range. If more than one dilution produces similar results: Average results. For all analytes but Der f 1: If results rise with increasing dilution factors: Choose the result based on the highest dilution factor A small percentage of Der f 1 samples show a low-level interference with substances within that particular dust extract that becomes amplified by the calculation of higher dilution factors. This effect is present if you observe results such as 1/10= 7ng/ml, 1/100=74ng/ml, 1/10,000=4500ng/ml. In this case, use the result from the 1/10 dilution, unless this result reaches ~100ng/ml, at which point you can rely on the results from the higher dilution factors. This aberrant effect has only been observed in <5% of our tested samples and only appears to occur in samples with low levels of Der f 1.

ELISA - General/Technical

What is ELISA?

Immunoassay technology uses allergen-specific monoclonal antibodies for the measurement of allergen levels in environmental and biologic samples.

What is the difference between a sandwich ELISA and a direct ELISA?
What is the difference between the Der p 1 ELISA kits, EL-DP1 and EL-DP1A?

A: INDOOR Biotechnologies markets two ELISA kits to measure Der p 1 which differ in the combination of monoclonal antibodies that are used in the assays:

EL-DP1: Uses capture mAb 5H8 and biotinylated mAb 4C1 for detection EL-DP1A: Uses capture mAb 10B9 and biotinylated mAb 5H8

The most widely used ELISA kit is EL-DP1 (5H8/4C1). The biotin 4C1 mAb is also used in the Der f 1 ELISA (EL-DF1). EL-DP1 is recommended for most routine analyses of dust and air samples for Der p 1. However, there is a degree of cross-reactivity for Der f 1 in the EL-DP1 assay, of about 2% (see Luczynska et al, J Immunol Meth, 1989). For routine analyses, this level of cross-reactivity is not significant.

The EL-DP1A kit shows <0.1% cross-reactivity with Der f 1 and is designed for applications that need absolute distinction between Der p 1 and Der f 1. For example, an allergen manufacturer who wants to be sure that they have no cross contamination between species in their dust mite cultures. The EL-DP1A assay has the same level of sensitivity as the EL-DP1 kit (1-2ng/ml).

What is the isoform specificity of the ELISA kits?
What is the chimeric ELISA?
Storage temperature?

The ELISA kit should be stored at 4°C and the standard at -20°C

Expiration dates?

The kit will be under warranty for 1 year upon receipt, provided that it has been stored correctly.

ELISA - Sample Collection/Preparation

What types of samples can I test with ELISA?
How do I collect a sample?
How do I prepare a sample to run on an ELISA plate?

Dust and air filter samples must be extracted prior to running on ELISA. Sample extracts can be analyzed directly on ELISA without any further extraction procedures.

How should I store my sample(s) if I cannot run them on ELISA right away?

We routinely keep house dust samples at 4°C prior to assay, but once extracted they should be stored at -20°C.

What allergen extraction protocol do you recommend for dust and air samples?
Do I need to sieve dust samples?

Whether to sieve the dust or not is determined by the quality of the dust. We do not routinely sieve dust collected from beds and soft furnishings. Carpet samples are sieved (e.g. using a No.45 mesh screen, 355um diameter sieve) to separate the fiber and large particles from fine dust. We recommend the use of the DUSTREAM™ collector which greatly reduces the need for sieving dust. After collecting a dust sample using the DUSTREAM™ collector, remove the nylon filter containing the dust sample insert, invert the filter and tap the dust onto a piece of weigh paper. The fine dust falls before the fibers come out of the filter.

ELISA - Protocol

How many samples can I analyze with one ELISA kit?

A1: Indoor Biotechnologies ELISA kits contain sufficient reagents (capture mAb, biotinylated detector mAb and allergen standard) for 10 plastic 96-well microtiter plates. The number of samples that can be analyzed per plate depends on the number of dilutions used for each sample.

A2: control curve in duplicate, with 4 control (PBS-T) wells, uses 24 microtiter wells, leaving 72 wells for samples on each plate. Typically, we use 4 doubling dilutions for each dust sample (1/10, 1/20, 1/40, 1/80 for mite allergens), which means that 18 samples can be tested on a plate. Under these conditions, one 20 plate ELISA kit could be used to analyse 18 x 20 = 360 samples.

A4: We use four dilutions per sample so that we can in most cases obtain results on >90% of the samples in a single assay. The four dilutions increase the probability of having at least two points on the linear part of the control curve for each sample. It may be possible to use fewer dilutions, if the samples are known to have allergen levels in a particular range. Other samples, e.g. allergenic extracts, may have very high allergen levels and have to be assayed at doubling dilutions starting at 1/100 or 1/1000, and may need to be serially diluted across the ELISA plate.

A5: Air samples usually contain low levels of allergen and are assayed at 1/2, 1/4, 1/8, and 1/16 dilution.

How many days are coated ELISA plates good to use?

The coated plates can only be stored for a short period e.g. over the weekend or up to a week. We usually leave plates coated with antibody solution and wrapped in plastic film in the lab fridge or cold room. We have not tried longer storage times.

After the coating step, should the remaining steps be completed in a day?

After the coating the plate and allowing it to incubate over night at 4°C, the remaining ELISA steps should be completed in a single day following the recommended incubation times.

Are the buffer pH measurements important?
How many dilutions of the sample should I test?

A1: We use four dilutions per sample so that we can in most cases obtain results on >90% of the samples in a single assay. The four dilutions increase the probability of having at least two points on the linear part of the control curve for each sample. It may be possible to use fewer dilutions, if the samples are known to have allergen levels in a particular range. Other samples, e.g. allergenic extracts, may have very high allergen levels and have to be assayed at doubling dilutions starting at 1/100 or 1/1000, and may need to be serially diluted across the ELISA plate.

A2: Air samples usually contain low levels of allergen and are assayed at 1/2, 1/4, 1/8, and 1/16 dilution.

Should I dilute all samples?

It depends on the type of samples being analyzed. Samples that are suspected to have low concentrations of the target allergen can start at a 1:2 dilution with double dilutions across the plate.

What temperature should I use for ELISA incubations?

Coating the ELISA plates with the capture mAb is carried out overnight at 4°C. All other steps are carried out at room temperature, usually 20-25°C.

Can we substitute ABTS substrate with TMB or OPD?

Yes. You can use OPD or TMB. We do not keep ABTS under Argon (it doesn’t appear to be necessary). We have good results with ABTS.

Is there a difference in the OD values between using ABTS or TMB with a stop solution when reading the plate?
Can I use stop solution?

The reaction can be stopped by adding 0.1ml 0.002M sodium azide to each well. Most ELISA readers scan plates in 5-20 seconds and plates can be read once the OD reaches 2.0-2.4 without stopping the reaction. Azide can be added if a large number (5-10 plates) are set up, or if the plates need to be preserved for any other reason e.g. taking photographs.

How long should a plate take to develop before being read?

Development time is variable between allergens, but it typically takes anywhere between 5 to 40 minutes for an ELISA plate to fully develop (target O.D 2.0-2.6 for the first standard)

ELISA - Interpreting Results

The duplicate standard curves have high %CVs, is this normal?

A1: After adding the ABTS shake gently by tapping the plate on the side occasionally and right before reading to ensure the color development is homogenous throughout.

A2: Pipetting is very important when running the ELISA assays.  Be sure that the pipettes being used, especially multichannels, are picking up and dispensing evenly during your doubling dilutions across the plate.  Also be sure that there are no air bubbles during your transfers. 

The sample dilution results have high %CVs, is this normal?

A1: After adding the ABTS shake gently by tapping the plate on the side occasionally and right before reading to ensure the color development is homogenous throughout.

A2: Pipetting is very important when running the ELISA assays.  Be sure that the pipettes being used, especially multichannels, are picking up and dispensing evenly during your doubling dilutions across the plate.  Also be sure that there are no air bubbles during your transfers. 

The optical density of the blanks seems high, what should they be?

A1: The background on the assay is usually higher in assays where the secondary antibody is a rabbit polyclonal. The background is usually around 0.15 OD. Other causes of the high background may be:

A2: The source of the peroxidase labeled Goat anti Rabbit IgG antibody. We use material from BioSource International and also Jackson Laboratories. Both work well with very low backgrounds. BioSource International Tel: 1-800-242-0607 (Cat # ALI4404) Jackson Laboratories Tel: 1-800-367-5296 (Cat # 111-036-045)

A3: How long is the ABTS substrate kept at 4°C? It is usually stable for about one month in the fridge. It can start to turn green and give high backgrounds if kept for longer periods. The ABTS solution should be more or less colorless for use in the assay. The same goes for the other solutions. We usually keep all solutions for less than a month at 4°C without Thimerosal.

A4: Block the plates for 30 minutes with 1%BSA/PBS-T before adding allergen solutions.

A5: In some cases a cause for high background or random high samples in a sample dilution series  where the first few sample dilutions are low or not detectable can be caused by plate washer contamination.  Plate washers should be cleaned on a regular bases to prevent random well contamination and plate washer blockages.

A6: If washing plates by hand, an increase in washes throughout the assay can help lower the backgroud.  Fill the wells completely without overflow and then dump the wells carefully not to contaminate.  Then gently tap the excess buffer from the plate on a paper towel.

What do my results mean?
How do I convert my ng/ml results into ug/g?

To convert from ng/ml to ug/g, the total amount sample extracted and the volume of extraction buffer used will need to be recorded. We recommend 2ml of extraction buffer for every 100mg of sample extracted. If this procedure was followed, then the ng/ml when multipled by 20 and divided by 1000 will convert the results to ug/g.

ELISA 2.0 - General/Technical

What are the benefits of the ELISA 2.0 compared to conventional ELISA?

The biggest benefit is time! The use of the ELISA 2.0 pre-coated plates means that the plates do not need to be coated the night before. Instead, they are ready when you are! ELISA 2.0 uses a modified protocol which enables the test to be done in two hours. Unlike the conventional kit, the ELISA 2.0 kit comes with all the necessary buffers, making the process easier for the user.  Also, the use of TMB as the developing substrate allows for increased sensitivity and lower background for many of our assays.

How long are the pre-coated plates stable? Do they remain stable after the plates have been removed from the package?

The pre-coated plates and all the reagents included in the kit are stable for up to 6 months after the kit’s shipment date. The plates must be kept in a sealed bag with desiccants until the time of use to maintain stability.

How long can the wash and assay buffers be used after they have been diluted?

Once diluted, the assay and wash buffers can be stored for up to one week at 4⁰C.

How do the results obtained using pre-coated plates compare to those obtained using the conventional ELISA?

All ELISA 2.0 kits have undergone both an independent validation procedure as well as a validation against our conventional ELISA. The results show that the ELISA 2.0 kits are able to detect allergens with the same accuracy and precision as our conventional ELISA kits.  

Do the plates need to be blocked to prevent non-specific binding?

No. The stabilizing buffer used to prepare the pre-coated plates also functions to block against non-specific binding.

Is a different dilution scheme recommended for testing samples with the ELISA 2.0 kit?

No. Samples should be run with the same dilutions as they would on a conventional plate.

Can ABTS be used to develop the plate instead of TMB?

While other substrates can be used, the plates have been validated using the TMB provided in the kit.

Should a higher background be expected when using the 2 hour protocol?

No. In fact, due to the use of a fast acting TMB developer, the background is often lower than what might be seen when using our conventional ELISA kits.

Can the ELISA 2.0 plate be read using the same instrument as the conventional ELISA?

Yes, as long as the instrument is capable of measuring absorbance at 450 nm.

Can the detection antibodies and standards purchased with the conventional kit be used with the ELISA 2.0 kits?

No. The concentrations of the reagents used in the ELISA 2.0 kits have been modified compared to our conventional kits in order to optimize assay performance.  

Why do ELISA 2.0 kits use stop solution?

The stop solution terminates the TMB enzymatic reaction and maintains a stable optical density.  This allows the plate to be read up to 30 minutes later, which is convenient if the plate reader is located away from where the experiment is performed.

Can I use part of the plate and reserve the remaining wells to use at a later date?

Although this may work, it is not recommended as the change in temperature moving the plate from 4oC to room temperature and back, may affect the coating stability.  Also, the kit includes enough assay standard to generate a single calibration curve (in duplicate).

Environmental Testing - General

What does ISO 17025 compliance mean?
Are you an accredited laboratory?
What is the typical turnaround time?

Our standard turnaround time for ELISA and MARIA analysis is 5 business days. Endotoxin and IgE-QBA analysis services have a standard turnaround time of 10 business days

Do you offer expedited service?

Yes, we do offered expedited service (2 business days turnaround time) at double the regular analysis price.

Environmental Testing - Sample Collection

What types of samples can be tested?
How much sample do I need?

A1: For the analysis lab to analyze for the allergen levels in bulk dust samples, we need 100mg of fine dust. Our recent findings (click link below) indicate that due to increased potential for variability, allergen analysis should not be attempted unless a minimum of 10mg fine dust is available. Samples with less than 10mg available of fine dust will not be analyzed and a handling charge will be applied. (NES - Not Enough Sample)

"Variability introduced into allergen immunoassays during the dust extraction process" 

A2: If using the DUSTREAM™ and sampling for the recommended area and time yields very little or no dust, continue sampling until the filter is 1/4 full.  Our allergen results are not based on area, but on microgram of allergen per gram of dust.

A3: For allergen extracts or extracts of bulk dust or air filters, we need a minimum of 0.5 mL, especially if testing for multiple allergens.

A4: For air sampling cassettes, the whole filter is extracted with 1ml of PBS extraction solution and the results are reported as ng or µg allergen per filter.

How do I collect a sufficient vacuum sample?
What are the advantages of dust samples over air filter samples?
How do I sample for laboratory animal allergens?
What air filter cassettes and membranes are acceptable?
Cat breeders - Should I test saliva or fur?
I've collected my samples, how should I store it?

Environmental Testing - Choosing the Proper Analysis Method and Allergens

Should I choose MARIA or ELISA - advantages/disadvantages?
What dust mite allergens should I test for, Der p 1, Der f 1 or Mite Group 2?
What cockroach allergen should I test for, Bla g 1 or Bla g 2?
Should I test my house for mold?

Environmental Testing - Shipping Samples to the Laboratory

Where do I ship my samples (US, UK or India)?
What shipping method should I use?
Do the samples need to be kept at a specific temperature?
Can you accept deliveries on Saturday?
Do you have a chain of custody?
Do you offer expedited analysis service?

Environmental Testing - Interpreting Analysis Results

What do my results mean?
What is Mite Group 1?
Are the high and medium guidelines for Fel d 1 and Can f 1 reversed?
How do we explain the Fel d 1 and Can f 1 guidelines to customers?
Why aren't there guidelines for Mus m 1 and Rat n 1?
Why can't I compare my air filter sample results to the guidelines?
Can I convert my air filter sample results to ug/g?
Can I use the standard curve on a plate and use it to analyze a different plate of the same allergen?

Endotoxin Testing - General

What does ISO 17025 compliance mean?
Are you an accredited laboratory?
What is the typical turnaround time?
Do you offer expedited analysis service?
What is endotoxin?

Endotoxin Testing - Sample Collection

What types of samples can be tested?
How much sample do I need to send?

A1: For the analysis lab to analyze for endotoxin levels in bulk dust samples, we need 100mg of fine dust.  Samples of bulk dust will not be processed if there is less than 20mg of fine dust.  If using the DUSTREAM™ and sampling for the recommended area and time yields very little or no dust, continue sampling until the filter is 1/4 full.  Our endotoxin results are not based on area, but on endotoxin Units per gram dust.

A2: It is very important that we receive samples that have not been extracted.  The extraction procedure must be performed in a clean environment with endotoxin free water containing 0.05% Tween.  Samples should be extracted and analyzed on the same day.  These steps are important in preventing endotoxin contamination from other sources. 

A3: Air filter samples can also be sent in for endotoxin analysis.  The whole filter is extracted in 1mL of endotoxin free water with 0.05% Tween.  Results are reported as endotoxin Units per filter.  We recommend sending in a blank filter for testing as well to provide a baseline for the specific filter being used.  

How do I avoid endotoxin contamination?
How do I collect a sufficient vacuum sample?
What air filter cassettes and membranes are acceptable?

Endotoxin Testing - Choosing the Proper Analysis Method

Should I choose LAL or rFC?

Endotoxin Testing - Shipping Samples to the Laboratory

Where do I ship my samples (US, UK or India)?
What shipping method should I use?
Do the samples need to be kept at a specific temperature?
Can you accept deliveries on Saturday?
Do you have a chain of custody?

Endotoxin Testing - Interpreting Analysis Results

What do my results mean?
Are my results high, medium or low?

IgE-QBA™ - General

What does ISO 17025 compliance mean?
Are you an accredited laboratory?
What is the typical turnaround time?
Do you offer expedited analysis service?

IgE-QBA™ - Sample Collection

What types of samples can be tested?
How much sample do I need?
How do I collect a sufficient vacuum sample?
What air filter cassettes and membranes are acceptable?

IgE-QBA™ - Choosing the Proper Analysis Method

What are the differences between IgE-QBA and MARIA?
Total IgE versus specific IgE?

IgE-QBA™ - Shipping Samples to the Laboratory

Where do I ship my samples (US, UK or India)?
What shipping method should I use?
Do the samples need to be kept at a specific temperature?
Do I need to enclose any extra paperwork when shipping serum samples?
Can you accept deliveries on Saturday?
Do you have a chain of custody?

IgE-QBA™ - Interpreting Analysis Results

What do my results mean?
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