There is sometimes confusion about water activity and how it relates to water content.  Water content is how much.  Water activity (aw) tells us about the energy of the water.  Both are measurable.  

Water Content

We know a lot about water content and how to measure it using various popular methods including loss on drying, Karl Fischer titration, capacitance and more.  Water content is typically expressed in % or Parts Per Million (PPM).

Water Activity

Water Activity is the amount of unbound water in a sample.  Water that is not bound to the ingredients themselves can be used by unwanted microorganisms which could lead to one of the contributing factors for food spoilage.  Water activity is a thermodynamic measure of water expressed as the vapor pressure of water in a sample divided by vapor pressure of pure water at a given temperature.  

Water Activity is based on a scale from 0.0 to 1.0 

The more unbound water we have the more likelihood we have for microbial spoilage. Water Activity (aw) Meters measure the unbound water vapor pressures to determine microbial spoilage, chemical and physical stability. 

Well documented and scientifically established guidelines that are also supported by FDA regulations outline these thresholds of microbial limits using a water activity (aw) range or scale.  This water activity (aw) range provides the lowest rating for inhibition of microorganism and other degradative chemical and physical reactions that effect shelf life in foods (see chart below).  

                                     

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Water Activity & Growth of Microorganisms in Food

Range of aw	Microorganisms generally inhibited by lowest aw in the range	Foods generally with this range
1.00-0.95	Pseudomonas,Escherichia,Proteus,Shigella,Klebsiella,Bacillus,Clostridium perfringens, some yeasts	Highly perishable foods and canned fruits, vegetables, meat, fish, milk, and beverages
0.95-0.91	Salmonella, Salmonella, Vibrio parahaemolyticus, C. botulinum, Serratia, Lactobacillus, Pediococcus, some molds, yeasts (Rhodotorula, Pichia)	Some cheeses (Cheddar, Swiss,Muenster, Provolone), cured meat (ham), bread, tortillas
0.91-0.87	Many yeasts (Candida, Torulopsis, Hansenula), Micrococcus	Fermented sausage (salami), sponge cakes, dry cheeses, margarine
0.87-0.80	Most molds (mycotoxigenic penicillia), Staphyloccocus aureus, most Saccharomyces (bailii) spp., Debaryomyces	Most fruit juice concentrates, sweetened condensed milk, syrups, jams, jellies, soft pet food
0.80-0.75	Most halophilic bacteria, mycotoxigenic aspergilli	Marmalade, marzipan, glacé fruits, beef jerky
0.75-0.65	Xerophilic molds (Aspergillus chevalieri, A. candidus, Wallemia sebi), Saccharomyces bisporus	Molasses, raw cane sugar, some dried fruits, nuts, snack bars, snack cakes
0.65-0.60	Osmophilic yeasts (Saccharomyces rouxii), few molds (Aspergillus echinulatus, Monascus bisporus)	Dried fruits containing 15-20% moisture; some toffees and caramels; honey, candies
0.60-0.50	No microbial proliferation	Dry pasta, spices, rice, confections, wheat
0.50-0.40	No microbial proliferation	Whole egg powder, chewing gum, flour, dry beans
0.40-0.30	No microbial proliferation	Cookies, crackers, bread crusts, breakfast cereals, dry pet food, peanut butter
0.30-0.20	No microbial proliferation	Whole milk powder, dried vegetables, freeze dried corn

*Adapted from L.R. Beuchat, Cereal Foods World, 26:345 (1981) 

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Pure water that is unencumbered has more energy and therefore can be available and used to do bad things by microorganisms.  As water comes in contact with a material substance the water's energy and water activity (aw) decrease. Water reacts differently with different material substances and can have a higher or lower water activity rating* (aw).  A water activity (aw) number closer to the top of the chart closer to 1.00 has a higher water activity while those lower have less.

Understanding and documenting how water activity is effected by different material substances provides valuable information.   Using this information provides a way for us to take proactive measures to lower water activity as we seek to improve microbial, chemical and structure stability of foods, pharmaceuticals, and other materials. 

Packaging to improve shelf life

 

 

 

 

 

Equilibrium of ingredients to make foods last longer

Explore multi-ingredient products where water activity in each ingredient will seek to equilibrate and change the overall water activity (aw) result of the product.  This can trick people who only look at water content of each ingredient and or even the water activity individually.

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WHY DO WE CARE ABOUT BROMINE NUMBER AND BROMINE INDEX ANYWAY?

The degree of unsaturated hydrogen carbide (Hydrocarbon) in oil and petroleum products is indicated by Bromine number or index. Hydrocarbons containing between 6 and 10 carbon molecules are the primary components of most fuels where the process of burning them produces energy. Saturated hydrocarbons are defined by molecular structure and are defined as Alkanes.  Alkanes are the basis for petroleum fuels.  Unsaturated hydrocarbons are also defined by their molecular structure and produce less energy when burned than do saturated hydrocarbons.  Mathematically it therefore requires a greater quantity of unsaturated hydrocarbons to be burned to equal the same amount of energy produced by burning the same amount of saturated hydrocarbons.  An un-friendly environmental side effect of burning hydrocarbons is the creation of carbon dioxide.  So from an environmental standpoint you could say we prefer the lesser of two evils and prefer to burn saturated hydrocarbons vs. unsaturated hydrocarbons. For these reasons alone it would make sense that we would want to measure and quantify these hydrocarbons. 

 

HYDROCARBONS AND SOME OF THEIR USES

NAME	USES
Methane	Fuel in electrical generation
Ethane	Chemical applications
Propane	Heating and cooking
Butane	lighters and aerosol
Pentane	Lab & production of polystyrene
Hexane	Glue
Heptane & Octane	Major contributor to gasoline
Nonane	Diesel fuel
Decane	Jet fuel, gasoline and diesel

 

Although the test method ASTM2710 describes the use of an automatic potentiometric titrator the coulometric Karl Fischer method is easier to perform (see ASTMD1492-08e1).  

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<BROMINE NUMBER AND INDEX BY COULOMETRIC KARL FISCHER TITRATION>

 

<PRINCIPAL OF MEASUREMENT>

Special notes to obtain correct measurement results:

1. Replace anolyte and catholyte reagent often (daily).
2. When anolyte turns to white color replace it with new anolyte.
3. Over use of anolyte and catholyte and not replacing it can cause results to be higher than expected.
4. Do not share Bromine titration cell with a moisture titration cell

 

Step 1: Preparation of Reagents

 

Step 2: Prepare Reagent for testing

Step 3: Measurement Procedure

Measure Bromine Number and Bromine Index

*Note that different Karl Fischer Titrator Models will have different button commands.  The MKC-710 series coulometric Karl Fischer titrators come standard with pre-programmed setup for running Bromine and follow the above button commands.

We hope this information helps you get started.  If you have any questions or would like some help please contact us by clicking on the button below.

 

 

 

How to Clean Karl Fischer Electrodes:

A Karl Fischer Titrator uses two electrodes.  The Inner burette (aka Generator Electrode) and the Detector Electrode.  We hope this information is helpful in giving some guidance on cleaing and caring for these Karl Fischer Titrator electrodes.

 

 

Cleaning with alcohol: general method

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ELECTRODE RINSE WITH SHOWER ACCESSORY:

Sample changers that are connected with automatic titrators generally are there for a reason.  Efficiency. From an operators point of view getting multiple tests done quickly while being able to take on other tasks in the lab is a key productivity booster.  Sample changers offer various sizes ranging from as few as 6 positions for samples up to some of the largest exceeding 50 sample positions.  Sample changers either have rotating carousels or an arm that moves electrodes and nozzles from sample to sample.  Each time a sample test is completed the electrode must be cleaned before moving on to the next test.  Many sample changers offer as standard a dip rinse between sample testing and as the name suggests it's really nothing more then dipping the electrode in clean water or solution.  For some samples this process is sufficent but for others it is not enough to effectively clean the electrode before the next test.  Luckily most manufacturers of sample changers offer additional cleaning power with the use of a shower rinse system.   Below is a video showing how a shower rinse process works.   Water is stored in a container and then is flushd and rinsed in one of the sample positions designated as the cleaning station.  Water is evacuated via tubes to a drain or sink.  

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There are MANUAL TENSIOMETERS that look like this:

PROS:

• >Great for hands-on learning
• >Can use virtually anywhere (does not require electricity)
• >Easy to learn how to use
• >Less expensive

CONS:

• >It's manual.  You have to twist the dials by hand
• >There is a technique to getting repeatable results
• >Human error potential is higher
• >Need to record results by hand

 

VIDEO DEMONSTRATION FOR MANUAL TENSIOMETER

There are AUTOMATIC TENSIOMETERS that look like this.

PROS:

• >Easy to operate.  Press a button and walk away
• >Run more tests quickly with high repeatability
• >Ability to record and report data results (store historical data too)
• >Dynamic testing features including time tests and Lamella length and more
• >Most handle both DuNouy Ring and Wilhelmy Plate

CONS:

• >More Expensive
• >Some models require a computer (some don't)

VIDEO DEMONSTRATION FOR AUTOMATIC TENSIOMETER

 

To help prospective users evaluate and compare the different types of models available in the market we have prepared a reference document we call the: 

                    "Tensiometer Selection Matrix"

This matrix is not necessarily brand specific as it was designed to help those seeking to compare capabilities and prices among popular manual Tensiometer models vs. popular Automatic or "digital" Tensiometer models. 

We hope you find the Tensiometer Selection Matrix helpful in your search and evaluation of Tensiometers.

 

                        

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From start to finish watch this short video to see how a sample of Jet Fuel Oil is tested for water content using a karl Fischer Titrator. For this training video we use:

1. The Aquapal III coulometric Karl Fischer Titrator (setup as a dual reagent configuration)
2. Reagents; Anolyte is coulomat AG and the catholyte is coulomat CG
3. A 4-place analytical balance SA-210
4. And a disposable syringe and disposable needle

In this video you will see the steps for running a test successfully including how to:

1. Extract your sample into the syringe
2. How to weigh your sample and tare the balance
3. How to inject a sample properly
4. How to input the sample weight and obtain a final result

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We hope you found the video helpful and informative!  If you think a colleague could benefit from this please share it with them!  Click on the twitter button to automatically share this video!

"How to test for moisture in Jet Fuel Oil using a Karl Fischer titrator"

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Thanks for Watching!

Many people use coulometric Karl Fischer Titrators to measure low level moisture at the part per million (PPM) level.  When it's time to start testing it's critical to have an understanding of how to:

1. Properly identify the glassware components
2. Assemble the glassware
3. Identify the reagents  (anolytes and catholytes)
4. Introduce the reagents required by the instrument and the sample being tested 

Once you have these concepts down you will have a strong working knowledge of how a Karl Fischer Titrator works and how to trouble shoot future problems.  Watch this short training video to learn more.

If you found this information helpful please share this with your colleagues!  Just click on the tweet this button.

  "Karl Fischer Glassware and reagents 101: Properly identify the glassware components, Assemble the glassware and Identify the reagents"

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We hope you find the training video helpful!
Thanks for Watching!

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Karl Fischer Glassware and Reagents 101:  How to setup.

 

It seems sometimes we overlook the obvious and forget to explain some of the most basic concepts.  Sorry about that.  So we thought it might be a good idea to show how Karl Fischer Glassware is setup and how we introduce or "charge" the vessel with reagents.  We hope you enjoy this short video tutorial!

 

 

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Review of KEM's new titration line 

I don't know about you but I have to admit that I enjoy learning about new technology.  Whether it's smart phones, cars, or kitchen appliances I think it's fun to find out about how a product has changed (hopefully for the better). For the most part a lot of consumer products see a change or upgrade about once every year. This is not really the case for titrators where maybe it's only every 6 to 8 years before we see a new generation unveiled.  I guess that's why I thought maybe it would be a good idea to take a look at this new 710 series that came out in February 2015.  I haven't actually ever written a "review" before so I decided to start by comparing what I know about some of the current titrator models and identify the things that pop out with the new titration line.   Here are my observations and comments.

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1. There are now three model levels; entry, mid-level, and flagship within each category (volumetric Karl Fischer, coulometric Karl Fischer, and automatic potentiometric titrator) 

My comment: I like the scale of the models as it can be helpful for those with varied budgets and needs.  I like the concept that you can start with getting only the basic model at first and then later bring in the flagship model and tie them all together into one system.  It will be interesting to see how people approach these options and whether the ability to expand a system is desirable or not.

2. All of the automatic titrators now can accommodate two burette drives

 

My comment: The automatic titrators come with one burette drive but being able to add a second burette drive allows an operator to run two separate titrations (titrants) without having to use an automatic piston burette.  Historically most titrator manufacturers offered only a single burette drive but it seems like this is changing.  It's kind of a big deal for those who run two different titrations and don't want to purchase an automatic piston burette.  I like this new capability.

3.  A new burette design for the automatic titrators and volumetric Karl Fischer titrators.

My comment: The burettes appear they will be easier to store and swap as the titrant bottle, burette and nozzles all go together as one smaller unit.   The burettes are now "smart" burettes and can store all of the reagent information within the head of the burette.  I like this.

4.  More Input/Output options for operators to move  and store data.  I/O options include LAN connectivity/URL, USB hubs, USB thumb drive ports, .CSV file format, .PDF file format, barcode readers, foot switches, and keyboards.

My comment:  More technology is built into these units. I think it was overdue so I am glad to see it finally arrive.

5.  Automatic Titrators now come with a propeller stirrer by default but can swap for a magnetic stirrer instead.

My comment: I like the option to do both but I think maybe the magnetic stirrer should have been the default and the propeller as the option.

 

6.  A new Wireless/ Wired 8.4 inch color touch panel controller (MCU).

My comment: This only comes with the mid-range and the flagship models.  The controller can sit next to the titrator or be carried around like a clipboard.  Operators can control the titrator through protective glass if necessary.  I'm not sure how many people will elect to use the wireless vs. the wired connection but it's nice to have the added capability.  Nice.

7.  Multi-titrator integration.  The wireless/wired MCU can control up to 4 different titrators simultaneously (any combination of Karl Fischer or automatic titrator) 

My comment: This feature is reserved for the flagship model.  I can see this being useful for those needing to run both moisture and acid for example.  Unfortunately the mid-level model MCU cannot be upgraded to the MCU flagship model so if you think you might expand later don't go with the S model.  Your better off getting the basic "B" model and then later tying them all together from the flagship model.

 

8.  Free method making software.

My comment:  All of the titrators now come with a CD that allows you to create methods on your PC and then transfer methods to the titrator.  You can also pull methods off of the titrator and edit it in the PC.  The software also comes with various popular methods pre-loaded to help get methods setup quicker.  I'm not so sure how robust this software is but free is nice.

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CONCLUSION:

Well I hope this was helpful in finding out quickly what the updates are for the new 710 series.  At this point since it's so new we will have to wait to evaluate how customers feel about their user experience and get their feedback on what they liked most and what they liked least.  If you have any questions or comments you can email me at info@scientificgear.com

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5 ways we use liquid density information

Some background:

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1. We live in a physical world

• >How much space does it take up?
• >How heavy is it?
• >How much of this can we put into that?
• >What is it?
• >Many everyday products are packaged by volume but sold by weight.
• >Predictive correlations can be made if you know the density.
• >If we change some of the ingredients that make up the fluid property will it change the weight?

The neat thing about understanding liquid density is that it can answer not only the three basic questions;

• >What is the mass of the liquid?,
• >what is the volume of the liquid?
• >What is the density of the liquid?

But also, What is the liquid?

2. You can use a liquids density to predict 

Fluid properties are probably even more telling where predictive

3. Density helps us better understand how to transport fluids

4. Density helps set petroleum prices

5. Density as it relates to gravity

Specific gravity

API gravity

⇒ Light crude oil has an API gravity higher than 31.1 degrees API
⇒ Medium oil has an API gravity between 22.3 degrees API and 31.1 degrees API
⇒ Heavy oil has an API gravity below 22.3 degree API
⇒ Extra Heavy oil has an API gravity less than 10 degree API

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CONCLUSION:

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