Standard Solvent-Free Operating Procedure 

for Measuring Membrane Recoverable Oil and 

Grease using Infrared Determination

Based on ASTM D7575

Orono Spectral Solutions

689 Odlin Road

Bangor, ME 04401
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Table of Contents

Method Overview ..............................................................................................3

Sample Preparation Instructions.....................................................................4

Acidified Field Samples....................................................................4

Standards in Distilled Water & LCS ................................................5 

Matrix Spike Additions .....................................................................7

Instructions for Passing Sample Through OSS Extractor ............................8

Syringe pump....................................................................................8

Drying OSS Extractors Using Drying Manifold ............................................11

Acquiring Spectra...........................................................................................12
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Method Overview

The OSS method for measuring membrane recoverable oil and grease has 

many logistical advantages over the traditional 1664 and 1664A methods that are 

currently in place. Unlike traditional analytical methods for measuring oil and 

grease, which require a great deal of user expertise with wet chemistry, the critical

sample loading step of the OSS method is automated. The OSS system for 

measuring membrane extractable oil and grease is very straightforward and 

analyzes a homogeneous sample in three steps. The first step uses a syringe 

pump to quantitatively deliver sample through the OSS Extractor. After the sample 

is passed through the Extractor, it is dried on a drying widget. Once dry, the 

Extractor is analyzed using an infrared spectrometer outfitted with commercially 

available software. The entire process can take as little as 5 minutes per sample for 

easily dried samples.

The OSS Method for Measuring Membrane Extractable Oil and Grease

1. Load Extractor using 2. Dry Extractor using multi- 3. Analyze Extractor using

 syringe pump channel drying manifold IR spectroscopy
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Sample Preparation Instructions

Careful sample preparation is critical for accurate oil and grease 

determinations using the OSS method. Unlike EPA Method 1664A which uses an 

entire liter bottle of sample, the OSS method requires only 10 mL per replicate for 

samples above 5 ppm. The small volume required for the method allows a user to 

perform multiple replicates from a single sample bottle, thus increasing analytical 

confidence. Therefore it is critical to properly homogenize the sample prior to 

analysis and be very careful when making all volumetric measurements. Detailed 

instructions for different types of samples are found below.

Preparation of acidified field samples using an ultrasonic bath

1. Set Temperature of ultrasonic bath to 40°C. Allow bath to heat up to desired 

temperature. Place bottles in bath, ensuring that the water level is high enough to 

fully submerge the bottles. Press the On/Off button to start ultrasonic vibration. 

NOTE: Make sure bottles caps are sufficiently tightened.

2. After 20 minutes, remove the sample from the ultrasonic bath. Use a paper 

towel to dry the outside of the bottle. Carefully remove cap and drop an empty 10

mL syringe into the neck of the bottle. Quickly fill syringe (with more than 11mL), as 

shown below. If performing multiple replicates on the same bottle, shake bottle by 

hand for 10 seconds between syringe draws.

NOTE: Most 10 mL syringes have a diameter between 14.3 and 14.7 mm. The field sample 

bottles shall have an appropriate opening width so that standard syringes can fit in.
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3. Proceed to instructions for passing sample through OSS Extractor.

NOTE: Homogenization of many samples can be adequately performed by shaking the 

bottle for 30 seconds by hand. To determine whether or not the mechanical shaker is 

required, it is acceptable to first shake the sample bottle vigorously for 30 seconds, hold the 

bottle up to a light and visually determine whether or not the sample appears homogeneous. 

Then, if the sample does not appear homogeneous, it can be placed in an ultrasonic bath for

20 minutes. If the sample does not appear homogenous after 20 minutes, more time in the 

ultrasonic bath may be necessary. For a wide range of tested matrices and holding times, 

20 minutes of mechanical shaking has proven adequate to homogenize almost any sample.

Preparation of standards in distilled water, including MDL and LCS samples

1. Using a pipette, outfitted with a polypropylene tip, carefully add 1.0 mL of 

concentrated sulfuric acid (H2SO4) to an empty 1L volumetric flask. After pipetting, 

remove the polypropylene tip, and place tip in beaker full of deionized water. 

Caution: Sulfuric acid is an oxidizing strong acid and can cause chemical and 

physical burns on skin. Take appropriate precautions when using this substance.

2. Carefully fill 1L volumetric flask to roughly 1 cm below the volumetric line with 

distilled or deionized water. Carefully increase the volume to the volumetric line 

using a disposable pasteur pipette and bulb. Exactly one liter of solution is 

measured when the base of the meniscus is level with the volumetric line.
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3. Once 1L has been measured in the volumetric flask, decant the acidic solution 

into a certified clean 1L amber bottle. There should be roughly 1.5 inches of 

headspace. Shake bottle vigorously for 5 seconds to insure that acid is evenly 

dispersed in the bottle.

4. Carefully measure the appropriate volume of spiking solution to be added to 

the amber bottle. This can be done in two ways. A volumetric pipette can be used 

if the volume required is the same as the certified volume of the pipette. If the 

required volume falls between pipette sizes, a graduated cylinder can be used to 

measure the spiking solution. In this case, the fluid should be carefully transferred 

into a slightly larger volumetric pipette for dispersal in the acidic solution. 

NOTE: If the spike addition requires more than 15 mL of spiking solution, empty enough 

volume of acidic water from the amber bottle to compensate for the spike volume. It is 

essential to carefully measure and record the volume of the removed water in order for an 

accurate concentration to be calculated. Additionally, it is imperative that there is adequate 

headspace to allow for sample homogenization.

5. To disperse the spike into the acidic solution, quickly submerge the pipette tip 

roughly 1 inch below the surface of the solution, rapidly depress the plunger, and 

quickly remove the pipette from the solution to minimize the amount of oil that will 

coat the pipette. After the spike is completely dispensed, cap and vigorously shake 

the amber bottle for 10 seconds. 

NOTE If the volume of spiking solution is larger than the largest available volumetric 

pipette, it is acceptable to do multiple additions. In this case, work quickly to dispense the 

multiple additions, and do not shake the bottle until the entire volume of spiking solution has 

been dispensed.

6. After shaking is complete, quickly drop empty syringe into open amber bottle as 

previously described, and draw plunger to fill syringe. If performing replicates on a 

single bottle, shake bottle for 5 seconds in between each syringe draw. It is 

important to work quickly during this step.

7. Proceed to instructions for passing sample through OSS Extractor.
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Preparation of matrix spike additions in existing bottles:

1. Homogenize sample as previously described.

2. Carefully measure the appropriate volume of spiking solution to be added to the 

amber bottle. This can be done in two ways. A volumetric pipette can be used if 

the volume required is the same as a common pipette tip. If the required volume 

falls between pipette sizes, a graduated cylinder can be used to measure the 

spiking solution. If a graduated cylinder is used, the fluid should be carefully 

transferred into a slightly larger volumetric pipette for dispersal in the acidic sample. 

3. To disperse the spike into the acidic sample, submerge the pipette tip roughly 1 

inch into the sample and firmly push the plunger. After the spike is completely 

dispensed, cap and vigorously shake the amber bottle for 30 seconds. Be sure to 

wipe the tip of the glass pipette, to avoid cross contamination.

NOTE Some matrices will require more shaking than the 30 seconds instructed above for 

the matrix spike to be properly dispersed. In general, matrices with more particulate matter and/or a 

high background level of oil and grease (>100 mg/L) may require more shaking. As described in the 

ASTM Method, if the matrix spike recovery is outside of the QC parameters listed in the Method, the 

spiked sample should be shaken for another period of time and another aliquot from the same bottle 

tested. 

4. After shaking, quickly drop empty syringe into open amber bottle, and draw 

plunger to fill syringe. If performing replicates on a single bottle, shake bottle for 5 

seconds in between each syringe draw. It is important to work quickly during this 

step.

5. Proceed to instructions for passing sample through OSS Extractor.
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Instructions for Passing Sample Through OSS Extractor

The purpose of this step in the analytical process is to use a syringe pump to 

quantitatively process a known volume of sample through the OSS Extractor. This 

is a critical step in the procedure; therefore the OSS method uses a mechanical 

syringe pump to insure that the sample is delivered through the Extractor accurately 

and reproducibly, thus greatly minimizing the potential for error.

Using the syringe pump to process sample through Extractor

1. Tilt syringe pump on its side, as shown in pictures below.

2. Load syringes upright in syringe channels as shown below. If user suspects that 

there is heavy particle loading in the sample, it may be necessary to only use one 

channel at a time.

NOTE The syringe pump could be lying horizontally to facilitate syringes loading. However, 

the pump shall be brought back vertically for the next steps.

3. Once syringe(s) are locked in place, tap syringe to move air bubbles to top and 

center of syringe(s).

4. Slide the depressor end of syringe pump upward, completely dispelling any air 

bubbles from top of syringe(s), as shown below.
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NOTE This could be done using the program of the syringe pump to prevent an accidental 

over-push on the depressor end that could result in a small yet undesirable water jet. The program 

would then have to be reset. It is also advised to absorb this excess of water with some tissue to 

protect the syringe pump metal case from acidified water.

5. Connect the OSS Extractor(s) to the syringe(s) using the Luer-Lok®fittings. If 

any sample spills over during this process, immediately wipe the surface of the 

syringe pump with DI water and paper towels. Acid present in the samples can

corrode the metal and plastic parts of the syringe pump, as well as potentially harm 

the user. Furthermore, the sample itself may be considered a biohazard so 

appropriate caution is warranted.
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6. To dispense 10 mL of sample, press “Start”. It will take two minutes for the 

sample to be passed through the OSS Extractor.

NOTE 1: Samples are processed at 5ml/min, controlled by the syringe pump.

NOTE 2: Visually inspect the syringe to make sure ~10mL has been processed. If less than 10 mL 

has been processed, restart the procedure with another extractor/syringe. When constantly using the 

same syringes, the user should be aware of the usual level of water left in the syringe after 10 mL of 

water has been processed.

7. Once the sample is processed, remove syringe with OSS Extractor from syringe 

pump. Pour the processed water out of the reservoir of the Extractor into an 

appropriate waste container.

7. Stand the device with syringe still attached vertically, as shown below and 

carefully remove syringe. User will notice that there is still water in the headspace 

of the OSS Extractor. It is imperative that OSS Extractors are maintained vertically 

from this point until completely dry.

Drying OSS Extractor Using Drying Manifold

1. Attach OSS Extractor onto the Luer-Lok®fitting of the drying manifold, as shown 

below, making sure the Extractor remains upright throughout this process.
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2. Open the manual valve for the line to which you connected the Extractor, also 

ensuring that all valves between the compressed gas source and the Extractor are 

open.

3. Keep the Extractor perpendicular to the floor for approximately one minute, 

allowing the air pressure to completely pass the sample in the headspace through 

the membrane. Once the headspace is clear, tap or shake the Extractor to rattle 

out water that has collected under the backside of the membrane. Doing so will 

reduce the time it takes to completely dry the membrane.

4. Allow membrane to dry fully. A good first indicator of dryness is that the 

membrane appears white or opaque, a color that is different from the color prior to 

drying. Another potential indication of dryness is that if the user can feel airflow 

through the backside of the membrane, the Extractor is almost dry. It can take 

anywhere between 5 and 20 minutes for a spike sample Extractor to dry, while a 

Extractor used to process sample with an unusually high particle loading may take 

up to 2 hours to dry completely. 

5. Proceed to analysis by infrared spectroscopy section to definitively determine 

whether or not the membrane is dry, as well as for membrane recoverable oil and 

grease analysis.
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NOTE 1 The drying system comes with an inline desiccant filter and spares. If the desiccant 

material inside the filter changes color from blue/purple to light pink remove the desiccant filter and 

replace with a spare. 

Diluting Samples

NOTE: If the initial result is outside of the upper limit of the method (200mg/L) it is 

recommended to perform a dilution of the sample. It is important to note the dilution factor for future 

records. A dilution of 1:5 is recommended for a first attempt. If this does not produce a sample 

within the detection limits of the Method, a larger dilution factor can be used.

1. Ensure that the sample to be diluted is properly homogenized. Dilution is carried 

out in the standard syringe. Pull appropriate amount of sample into the syringe. 

Quickly fill the syringe the rest of the way with DI water. Follow the procedure for 

passing sample through the OSS extractor as written above.

Acquiring Spectra

Acquiring Spectra using the Horizon Software

Opening the Horizon Software and Collecting a Daily Background Spectrum

1) To open the software, double click on the “Horizon MB” icon found on the desktop.

2) Once the software opens, it is important to begin a “project”, which is where the data 

files for the day will be saved. To do this, select “New” from the “Project” dropdown menu 

at the top of the window. You are then prompted to name your project and save it.

3) It is now time to collect a 200 scan background. Place the premade Extractor labeled 

“Background” into the IR beam jig. 

4) Under the window with the header “MB3000 Series Instrument”, make sure that the 

“Acquisition” tab is pressed, and be sure that the settings match the table below
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5) Press the “Reference” button, which is found near the top of the “MB3000 Series 

Instrument” window. After a few seconds, the reference scan will begin, and you can track 

the progress in the lower left hand side of the screen.

Collecting a spectrum of a sample using the ABB MB3000 IR spectrometer

1) Change the “Acquisition Parameter” settings to they read:

Resolution 8

Scans 50

Measurements 1

Interval 0 min

Initial Delay 0 min

Acquisition Mode Absorbance

Display Full Spectral 

Range

Start Wavenumber 300

Stop Wavenumber 4000

Reference File

Detector Gain 27

2) In the area below the “Acquisition Parameter”, it is time to save the sample information. 

Resolution 8

Scans 200

Measurements 1

Interval 0 min

Initial Delay 0 min

Acquisition Mode Absorbance

Display Full Spectral 

Range

Start Wavenumber 300

Stop Wavenumber 4000

Reference File

Detector Gain 27
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3) Give the sample an appropriate name and make sure the “Save to Project” box is 

checked. 

4) Click within the “Project” box, and a tab with “...” appears. Click the tab and select the 

project that the spectra should be saved to. If you would like to designate a separate folder 

to save spectra within the project, there is a field for that as well. 

5) Place the Extractor in the infrared beam using the jig, and press the “Measure” button at 

the top of the “MB3000 Series Instrument” window. The scan progress can be monitored in 

the lower left hand corner of the screen.

6) If there is ever a need to abort the acquisition, it can be done by pressing the “Stop” 

button.

Quantifying Membrane Recoverable Oil and Grease Using Peak height

1) Sometimes when multiple spectra are taken in a short period of time, the data acquisition 

software merges all spectra together. However, to avoid potential software glitches, the 

spectra should be split before quantification. To split the merged spectra, click on the “Split 

Views” button that is found on the toolbar, below the “Window” dropdown menu . 

Now, each spectrum is separated, and the user can select the spectrum of interest by 

selecting the appropriate tab found below the toolbar.

2) It is often useful to zoom into a particular region of the spectrum to get a better look at 

the peaks. This is done by using the cursor to click and drag a box around the region of 

interest, which in our case is between roughly 2400 and 3300 cm-1.

3) To measure the peak due to hydrocarbons, the “Find Peak” function must be active in the 

“Mathematics” window.
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4) Once “Find Peaks” is selected, the user must select the peak of interest. This is done by 

holding down the “Ctrl” key on the keyboard and left clicking anywhere on the peak with 

the mouse. The peak that we care about is found between roughly 2800 and 3000 

wavenumbers, so click anywhere on that peak.
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5) The software very rarely picks the correct integration limits or peak location, so the user

must do this manually, in the field below the spectrum. In general, to set the baseline, the 

“begin” value should be 2800 and the “end” value should be 2990. As instructed by the 

Method, these integration limits should be chosen for the best results for each spectrum; i.e. 

if there is clearly an issue with the “end” value being 2990, the “end” value should be 

chosen differently. This situation is most likely to arise when the concentration is near the 

recommended reporting limits of 5 mg/L on the low end and 200 mg/L on the high end. For 

instance, if the concentration is below 10 mg/L, it may be necessary to choose an “end” 

value that is closer to 2970 (see example below).
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Similarly, if the concentration is over 150 mg/L, the peak may be so broad that the standard 

“begin” value of 2800 and standard “end” value of 2990 would cut off part of the peak. 

So it may be necessary to set the”begin” and “end” values to broader points, such as 2770 

and 3048 (see example below).
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It is ok if the software defaults to some decimal within 1 wavenumber. The “Maximum” 

value denotes the top of the highest part of the peak. The user must set this manually, and 

the values are typically 2912, 2916, 2920, 2924, or 2928 cm-1. This is done by trial and 

error, or by using the crosshairs to determine the peak max location. Although it is possible 

to drag the small red box to the peak location, it is usually easier to manually enter the peak 

maximum until it is found by trial and error. A properly integrated peak is shown below.
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6) The peak height is listed under the “Height [Abs]” heading. It is important to record the 

“Height”, not the “Absolute Height”, which does not take into account the location of the 

baseline. Record this value.
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Determining Membrane Dryness Spectroscopically

The major spectral interferent for this method is the presence of water on the 

membrane. Water absorbs strongly in the infrared, with a peak centered approximately at 

3400 cm-1. When too much water is present on the membrane, the peak due to water spills 

over into the region where peaks due to hydrocarbons appear, leading to inaccurate analysis. 

Moreover, the peak due to water can potentially influence the placement of the baseline 

points, also leading to inaccurate analysis. In this section, we provide a few spectra to help a 

user determine whether or not the membrane is adequately dry for analysis.

Spectrum #1: Not even close. In this spectrum, the bands due to hydrocarbons are not 

visible because the water peak dominates.
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Spectrum #2: Getting Close. In the spectrum below, the water peak is still visible, but the 

hydrocarbon peak can easily be seen. Typically at this point in the drying process, air is 

flowing through the membrane, and the membrane will only require a few more minutes 

until fully dry. In some cases, the membrane does not get drier than this, and it is 

acceptable to proceed with quantification. It should be known that spectrum #2 represents 

the minimum acceptable level of dryness.
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Spectra #3 and #4: These two spectra represent a membrane that is dry enough for 

analysis. The peak due to hydrocarbons is easily resolved from the peak due to 

hydrocarbons. Many membranes that have processed real samples never get drier than this. 
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AIRS Software and Data Collection

The AIRS software is automated and guides the user through the process of 

collecting data. The ASTM D7575 method has been implemented and can be 

performed through different menus in the software. The user will be able to do the 

following :

-Validate the instrument performance

-Calibrate the instrument with the help of calibration standard devices (this step is 

required to calculate the slope and intercept and implement it in the automated 

procedure)

-Perform the initial demonstration of laboratory capability

-Perform all quality control tests (may require an update of the low-range limit)

-Determine oil and grease concentration for various samples

An Excel template and a simplified procedure are provided. The template serves to 

calculate different values from the calibration and QC data that are to be 

implemented in the AIRS software (see AIRS Quick Guide). The simplified 

procedure shall be a guide through the different steps required to perform the daily 

routine of the OSS method.

The detailed software procedure is available in the AIRS software’s Quick Guide.