洗涤剂中阳离子表面活性剂含量检测方案(自动电位滴定)

智能文字提取功能测试中

阳离子表面活性剂含量的测定 应用资料表面活性剂分为阳离子表面活性剂、阴离子表面活性剂、两性表面活性剂和非离子表面活性剂。本应用资料使用两种检测方式(表面活性剂电极和粒子电荷检测器)测量洗涤剂中所含阳离子表面活性剂的含量。APAT-0162en京都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD. APAT-0162er Application Note Measurement of the cationic surfactants in bath detergentusing surfactant electrode and particle charge detector Industry Cosmetics & soap Instrument Automatic potentiometric titrator Measurement method Potentiometric titration/Ion association titration Standards QB/T 4969 1. Scope Surfactant is a compound having a hydrophibic parts in the molecule. Depending on theproperties of the hydrophilic part， surfactant is classified into cationic surfactant， anionicsurfactant， amphoteric surfactant， and nonionic surfactant. In these surfactants， cationic surfactants have a property which the hydrophilic group has apositive electric charge after ionic dissociation， whereas anionic surfactants have a negativecharge. Both of these electric charges react and produce association formation. The producedassociation formation is insoluble and precipitated in water by decreasing of electric chargeand increasing of hydrophobicity during the reaction. Potentiometric titration method uses thischemical reaction to directly titrate the ionic surfactant. This Application Note introduces thecase in which the cationic surfactants contained in bath detergent is measured by using twokinds of detectors (a surfactant electrode and a particle charge detector). 2. Precautions The sensing part of the surfactant electrode does not have a high resistance to organic solvents.Therefore this part should not be cleaned with organic solvents. After measurement， theelectrode should be rinsed with distilled water and wiped off water with paper towel from thesensing part of electrode. When the particle charge detector is used， immerse the probe in ethanol after eachmeasurement and clean by driving the piston for approximately 1 minute. After that，completely remove the ethanol by rinsing it out with distilled water before starting the nextmeasurement. 3. Post-measurement procedure When the surfactant electrode is used， remove the internal solution and rinse the inside withdistilled water several times by using dropper. After the water from inside， attach the suppliedprotective cap and keep it dry. In the case that the electrode is stored with distilled waterdeterioration of the electrode is accelerated due to elution of the ingredients elements of fromthe sensitive membrane into the solution. When the particle charge detector is used， immerse the probe into ethanol， and rinse by drivingthe piston for approximately 1 minute. Remove the ethanol by rinsing with distilled water， andwipe off away water with a paper towel from the probe and keep the probe dry. 4. Apparatus ·Automatic potentiometric titrator (preamplifier ： STD) ·Combined surfactant electrode (Internal liquid： 3.3mol / L potassium chloride solution) ·Particle charge detector 5. Reagents Titrant：0.002nmol/L Dodecylbenzenesulfonic acid sodiumSolvent ： Pure water 6. Procedure 1) Take 0.5 g of the bathwater detergent into a beaker. 2) Add 100mL of distilled water. 3) Titrate the sample solution with 0.002mol/L of Dodecylbenzenesulfonic acid sodium， anddetect inflection point as end-point in titration curve. 7.Calculation Cationic surfactant (%)=EP1xTFxC1xK1/S EP1…·Titration volume of 1st end point (mL) TF···Factor of titrant =0.9913(Surfactant electrode) *=1.0091(Particle charge detector) * C1···Coefficient of concentration conversion=0.874mg/mL K1··Coefficient of unit conversion =0.1 S…·Sample size (g) *The factor was measured using 0.002 mol/L benzethonium chloride standard solution. 8. Example -Titration parameter- *Below parameter was used when measurement by using a surfactant electrode wasperformed. ： Intermit (The above condition is an example. The setting condition depends on the titrator model.) 京都电子工业株式会社-可睦电子(上海)商贸有限公司电话：021-54488867 电邮： kemu-kem@163.com *Below titration curve was obtained by using a surfactant electrode -Titration parameter- *Below parameter was used when measurement by using a particle charge detectorwas performed. ： Intermit ： EP Stop Number of EP ：1 End Sense ：Auto Gain ：1 Max. Volume ：：20(mL) Data Sampling ：Set Channel/Unit(Ctrl.) ： Ch2，mV Data sampling pot. ：999mV Channel/Unit(Ref.) ：Off Data sampling vol. ：0.1mL pH Polarity ：： Standard Ctrl. Speed ： Set Titr. Type Check ： No Check Cut-off time ：7s Wait Time ：：30(s) Unit volume ：0.1mL Dose Mode ：None Dispense speed ：1s/mL Other Ctrl. ： Standard Auto Int. Mode ： Standard Piston Speed ：：7 Stirrer Speed ：4 Stirrer Speed ：4 (The above condition is an example. The setting condition depends on the titrator model.) -Titration curve一 *Below titration curve was obtained by using a particle charge detector Table 1 The measurement result of cationic surfactant in bath detergent By using Surfactant electrode By using Particle charge detector Sample(g) Titration amount(mL) Conc.(%) Sample(g) Titration amount(mL) Conc.(%) 1 0.5202 2.1884 0.364 0.5096 2.1613 0.374 2 0.5333 2.1768 0.354 0.5332 2.3273 0.385 3 0.5065 2.1469 0.367 0.5081 2.1433 0.372 Mean 一 一 0.362 一 一 0.377 S.D. 一 一 0.007 一 一 0.007 R.S.D(%) 一 一 1.987 一 一 1.844 9. Summary The concentration of the anionic surfactant contained in bath detergent was determined bypotentiometric titrator with using two detectors (surfactant electrode and particle chargedetector). The results by using both detectors were obtained with good repeatability which the both RSDvalues were less than 2%. Also， significant difference in these two measurement results werenot observed. The features of these detectors are summarized as follows： the surfactant electrode isreasonable Price compared to the particle charge detector， but the general lifetime is only from3 to 6 months. The particle charge detector is expensive than the surfactant electrode， butprobe part is chemically stable， and can be continuously used unless the main body of the unithave electrical/mechanical failure. Nevertheless， it has measurable limitation depending onsome surfactant structures. To measure surfactants by manual analysis， chloroform， which is hazardous， needs to be used.Also， the two-phase titration requires a complicated operation procedure. In automatic titration，the samples are directly titrated without using chloroform， which allows simple and quickmeasurement. 都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD.