Quantcast
Namespaces
Variants
Actions
Personal tools

ColorpHast vs pH meter

From HomeBrewTalk Wiki
(Difference between revisions)
Jump to: navigation, search
(EMD's respose)
 
Line 1: Line 1:
Taste problems in my beers after I moved to a new house, had to use new water and started measuring mash pH with EMD's colorpHast strips prompted me to compare tha pH determined by the pH strips with the pH measured by a pH meter. Though I later found that the taste problems had more to do with the hops I used I discovered an unexpected systematic error for the pH read from the pH strips which was also confirmed in an e-mail from EMD.
+
Taste problems in my beers after I moved to a new house, had to use new water and started measuring mash pH with EMD's colorpHast strips prompted me to compare the pH determined by the pH strips with the pH measured by a pH meter. Though I later found that the taste problems had more to do with the hops I used I discovered an unexpected systematic error in the pH read from the pH strips which was also confirmed in an e-mail from EMD.
  
 
===set-up===
 
===set-up===
Line 7: Line 7:
 
===experiment===
 
===experiment===
  
The pH meter was calibrated and each of the pH buffer samples were measured with the pH meter and the colorpHast strips. All measurements were taken at room temperature (70 *F / 20 *C). The colorpHast strips were submerged for 5 seconds until the color didn't change anymore. Leaving them in longer than that didn't change their reading. The strips color was matched against the provided color scale in tungsten light. The color that matched the strips color best was chosen as the reading and when a color seemed to fall between 2 colors the pH was read as the avarage of the pH given for the 2 colors on the color scale.
+
The pH meter was calibrated and each of the pH buffer samples were measured with the pH meter and the colorpHast strips. All measurements were taken at room temperature (70 *F / 20 *C). The colorpHast strips were submerged for 5 seconds until the color didn't change anymore. Leaving them in longer than that didn't change their reading. The strip's color was matched against the provided color scale in tungsten light. The color that matched the strip's color best was chosen as the reading and when a color seemed to fall between 2 colors the pH was read as the avarage of the pH given for the 2 colors on the color scale.
  
 
===results===
 
===results===
Line 45: Line 45:
 
  Based on the information below, I am assuming that you are using the  
 
  Based on the information below, I am assuming that you are using the  
 
  4-7 clorpHast pH parer, part number 9582. The sensitivity of the part  
 
  4-7 clorpHast pH parer, part number 9582. The sensitivity of the part  
  number is 0.2-0.3 pH units. A pH meter will always be more accurate than the pH
+
  number is 0.2-0.3 pH units. A pH meter will always be more accurate  
strips ecause the meter will eliminate any human error in determining
+
than the pH strips ecause the meter will eliminate any human error in  
  color. Because of the possibility of human error, the strips are consider
+
  determining color. Because of the possibility of human error, the strips  
  semi-quantitative but are more convenient that a pH meter when testing
+
  are consider semi-quantitative but are more convenient that a pH meter  
  in the field and pH meter is not easily accessible. If you need further assistance,
+
  when testing in the field and pH meter is not easily accessible. If you  
feel free to contact me.
+
need further assistance, feel free to contact me.
  
 
  D. S.
 
  D. S.

Latest revision as of 08:11, 7 March 2007

Taste problems in my beers after I moved to a new house, had to use new water and started measuring mash pH with EMD's colorpHast strips prompted me to compare the pH determined by the pH strips with the pH measured by a pH meter. Though I later found that the taste problems had more to do with the hops I used I discovered an unexpected systematic error in the pH read from the pH strips which was also confirmed in an e-mail from EMD.

Contents

[edit] set-up

For the test 10 pH buffer solutions were mixed using the 4.01 and 7.01 calibration buffers that are sold by morebeer (MT610). The pH of these buffer solutions was chosen to match the pH values on colorpHast's color scale. The pH strips (MT629) and the pH meter (MT601) were purchased at morebeer.com

[edit] experiment

The pH meter was calibrated and each of the pH buffer samples were measured with the pH meter and the colorpHast strips. All measurements were taken at room temperature (70 *F / 20 *C). The colorpHast strips were submerged for 5 seconds until the color didn't change anymore. Leaving them in longer than that didn't change their reading. The strip's color was matched against the provided color scale in tungsten light. The color that matched the strip's color best was chosen as the reading and when a color seemed to fall between 2 colors the pH was read as the avarage of the pH given for the 2 colors on the color scale.

[edit] results

targeted buffer pH actual buffer pH measured with pH meter pH measured with colorpHast strips difference
4.0 (4.01 buffer) 4.0 4.0 ~ 0.0
4.4 4.38 4.0 ~ -0.4
4.7 4.70 4.4 ~ -0.3
5.0 5.01 4.7 ~ -0.3
5.3 5.32 5.0 ~ -0.3
5.5 5.50 5.15 * ~ -0.3
5.8 5.78 5.5 ~ -0.3
6.1 6.14 5.8 ~ -0.3
6.5 6.47 6.3* ~ -0.2
7.0 (7.01 buffer) 7.0 7.0 ~ 0.0
  • ) these samples read between 2 colors

The resuls show that the strips that were used in this experiment show a systematic error of about 0.3 pH units which meas that a mash which measures 5.3 with the strips is actually at pH 5.6. The subsequent lautering can be higher and can easily exceed the 5.8 maxium pH for tannin safe sparging

[edit] EMD's respose

I sent these results to EMD and wanted to get an input on these findings. Here is the e-mail that I got back:

Based on the information below, I am assuming that you are using the 
4-7 clorpHast pH parer, part number 9582. The sensitivity of the part 
number is 0.2-0.3 pH units. A pH meter will always be more accurate 
than the pH strips ecause the meter will eliminate any human error in 
determining color. Because of the possibility of human error, the strips 
are consider semi-quantitative but are more convenient that a pH meter 
when testing in the field and pH meter is not easily accessible. If you 
need further assistance, feel free to contact me.
D. S.
Technical Service Rep
EMD Chemicals
1-800-xxx-xxx 
xxx.xxx@emdchemicals.com

--Kaiser 07:07, 7 March 2007 (CST)