commonaskedquestions_ise
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| =====Frequently Asked Questions (Ion-selective electrodes)===== | =====Frequently Asked Questions (Ion-selective electrodes)===== | ||
| ===How often do you need to calibrate? | ===How often do you need to calibrate? | ||
| - | Recalibrate at least once a week, or daily if in doubt of your | + | Recalibrate at least once a week, or daily if in doubt of your results being accurate or reproducible. Check the manual for more information on each ISE about the expected stability. |
| - | results being accurate or reproducible. | + | |
| ===How long after being opened or made are standards good?=== | ===How long after being opened or made are standards good?=== | ||
| - | The stock standard will last at least six months before | + | The stock standard will last at least six months before discarding, whereas diluted standards treated with ISA/pH buffer should be prepared weekly. |
| - | discarding, whereas diluted standards treated with ISA/pH | + | |
| - | buffer should be prepared weekly. | + | |
| ===How do you store the electrodes? | ===How do you store the electrodes? | ||
| - | It is best to store them dry when they are not to be used in | + | It is best to store them dry when they are not to be used in the next week or so. Empty out the filling solution in the gas-sensing electrode. For shorter periods, store in dilute standard approximating the sample concentration, |
| - | the next week or so. Empty out the filling solution in the | + | ===Can you do temperature compensation with ISE?=== |
| - | gas-sensing electrode. For shorter periods, store in dilute | + | Yes, it is possible, but somewhat difficult. |
| - | standard approximating the sample concentration, | + | - You have to know the isopotential point for a given electrode system. |
| + | - The concentration of the sample has to be similar in concentration to the isopotential point or else the temperature correction will be very inaccurate. | ||
| + | - The temperature of the sample can not exceed the operational temperature range of the ISE. | ||
| + | - Very little isopotential point data for ISE's is available at this time. | ||
| + | **It is best to standardize and measure samples at the same temperature without using temperature compensation.** | ||
| + | ===Can you do in-line continuous ISE measurement without treating the sample? | ||
| + | Yes, direct measurement is possible in many cases without ISA/buffer addition to the sample stream. However, Fluoride, Sulfide, Ammonia, and Sodium Electrodes do require pH adjustment and must have ISA/ buffer added to the sample stream. | ||
| + | ===Which standards should be used with the ISE?=== | ||
| + | The most obvious choice will be determined by what | ||
| + | concentration units are desired (e.g. ppm as what?). Also, if | ||
| + | an electrode is being used to measure another ion (e.g. | ||
| + | sulfate with a lead electrode), use a stock standard of the | ||
| + | ion to be measured (e.g. sulfate). | ||
| + | ===Why buy a combination electrode instead of separate ones?=== | ||
| + | Advantages: | ||
| + | * no external reference electrode needed | ||
| + | * more economical than price of both | ||
| + | * one less electrode to fit in the process. | ||
commonaskedquestions_ise.txt · Last modified: 22/02/2019 10:55 by pieter
