Cations

Key words: cations, Kationen, CE, indirect detection, indirekte Detektion

Inorganic cations can be determined in uncoated capillaries with indirect UV detection. As the EOF migrates in the same direction as the cations short analysis times are possible. For the separation of ammonium and potassium it is necessary to add 18-crown-6 ether, which slows potassium down in relation to ammonium due to a selective komplexation of the crownether and potassium. The UV acitve co-ion of the electrolyte can be adapted due to the desired peak symmetry and the matrix. For the determination of fast cations like ammonium, potassium and sodium the electrolyte system based on imidazole is the most appropriate. For the determination of the slower cations an electrolyte based on aminopyridin or the cation buffer (Agilent) are available. These systems are equally suitable for the separation of aliphatic amines (see also chapter „Amine“). The optimization of the sensitivity can be achieved by increase of the injection.

Cation standard solution – 10 mg/l

• Mode: CZE
• Electrolyte: Aminopyridine
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 260 nm
• Description: The standard solution contains 10 mg/l ammonium, potassium, calcium, sodium, magnesium, strontium and barium each as well as 2 mg/l lithium.

Download: Standardlösung10-pdf

Cations in fruits (tangerine, banana, strawberry)

• Mode: CZE
• Electrolyte: Aminopyridine with 2 mM 18-crown-6
• Capillary: fused silica, 50 µm ID, 56 cm effective, 64 cm in total
• Injection: 15 s, 50 mbar
• Detection: indirect UV, 260 nm
• Separation: 25°C, +30 kV
• Description: Tangerine. The juice was collected from a piece of the tangerine using a pipette. Before the injection the juice was diluted 1:20 and centrifugated.

In the PDF the e-grams of the cations of a standard solution, tangerine, banana and strawberry are summarized. All fruits contain high amounts of potassium and magnesium and low amounts of sodium. Further it can be seen that the strawberry additionally has a relevant concentration of calcium.

Download (218 KB): cations-fruits

Magnesium in food supplements

Magnesium is a very important fabric for our body. It participates in our muscles and nerve functions. It is found in many different vegetables and corn products. In case of a deficiency, you feel sleepy and have muscle cramps. If you have too much magnesium, your blood pressure will lower and you might get some diarrhea.

• Mode: CZE
• Electrolyte: Aminopyridine
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Detection: indirekt UV, 260 nm
• Description: The three samples were weighed 100 mg/20 ml.

Download: Magnesium.pdf

Zinc in food supplements

The determination of zinc and other cations in different food supplements is shown.

• Mode: CZE
• Electrolyte: Aminopyridine
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Detection: indirekt UV, 260 nm
• Description: Zinc was analyzed in an evervescent tablet and in capsules (see pdf).

Download: zinc1.pdf

Cation standard solution – 1 mg/l

• Mode: CZE
• Electrolyte: Aminopyridine
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 260 nm
• Description: The standard solution contains 1 mg/l ammonium, potassium, calcium, sodium, magnesium, strontium and barium each as well as 0,2 mg/l lithium.

Download: Standardlösung-1.pdf

Cation standard solution – 1 mg/l with optimized Injection

• Mode: CZE
• Electrolyte: Aminopyridine
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 30 s, 50 mbar
• Detection: indirect UV, 260 nm
• Description: The standard solution contains 1 mg/l ammonium, potassium, calcium, sodium, magnesium, strontium and barium each as well as 0,2 mg/l lithium. Due to the increase of the injection time the sensitivity is drastically improved.

Download: Standardlösung-1-optimiert.pdf

Cation standard solution – 10 mg/l

• Mode: CZE
• Electrolyte: Imidazole with 2 mM 18-crown-6
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 215 nm
• Description: The standard solution contains 20 mg/l cesium, 10 mg/l ammonium, potassium, calcium, sodium, magnesium, strontium and barium each as well as 2 mg/l lithium.

Download: Standardlösung10-Imidazol.pdf

 

Cations in tap water

• Mode: CZE
• Electrolyte: Imidazole with 2 mM 18-crown-6
• Capillary: fused silica, 50 µm ID, 64 cm in totalt
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 215 nm
• Description: The tap water was diluted 1:2.

Download: Kationen-in-Leitungswasser.pdf

Cations in juice

• Mode: CZE
• Electrolyte: Imidazole with 2 mM 18-crown-6>
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 215 nm
• Description: The apple juice was diluted 1:10.

Download: Kationen-in -Saft.pdf

Cations in fruits

• Mode: CZE
• Electrolyte: Imidazole with 2 mM 18-crown-6
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 215 nm
• Description: The determination of cations was done with a mango. The fruit was mashed and 250 mg of the pap were diluted in 10 ml pure water. This suspension was homogenized in an ultra sonic bath. The received solution was directly injected without filtration.

Download: Kationen-in-Mango.pdf

Cations in a soft drink

• • Mode: CZE
  • Electrolyte: Imidazole with 2 mM 18-crown-6
  • Capillary: fused silica, 50 µm ID, 64 cm in total
  • Injection: 10 s, 50 mbar

• Detection: indirect UV, 215 nm
• Description: The determination of cations was done in cola. It was diluted 1:10 before injection.

Download: Kationen-in-Cola.pdf

Cations in coffee

• Mode: CZE
• Electrolyte: Imidazole with 2 mM 18-crown-6
• Capillary: fused silica, 50 µm ID, 64 cm in total
• Injection: 10 s, 50 mbar
• Detection: indirect UV, 215 nm
• Description: The determination of cations was done in instant coffee. For this 10 mg of the powder were diluted 10 ml pure water before injection.

Download: Kationen-in-Kaffee.pdf

Cation standard solution with calibration

• Mode: CZE
• Electrolyte: Cation Buffer, Agilent 5064-8203
• Capillary: fused silica, 75 µm ID, 64 cm in total
• Detection: indirekt UV, Sig. 350 nm, Ref. 215 nm
• Description: The standard solution contains 5 mg/l ammonium, sodium and triethylamine, each. The pdf also shows the calibration curves found for the single ions.

Download: Kationen-TEA.pdf