If you are looking for optimized HPLC method to analyze Guanidine check our HPLC Applications library

For optimal results in HPLC analysis, it is recommended to measure absorbance at a wavelength that matches the absorption maximum of the compound(s) being analyzed. The UV spectrum shown can assist in selecting an appropriate wavelength for your analysis. Please note that certain mobile phases and buffers may block wavelengths below 230 nm, rendering absorbance measurement at these wavelengths ineffective. If detection below 230 nm is required, it is recommended to use acetonitrile and water as low UV-transparent mobile phases, with phosphoric acid and its salts, sulfuric acid, and TFA as buffers.
For some compounds, the UV-Vis Spectrum is affected by the pH of the mobile phase. The spectra presented here are measured with an acidic mobile phase that has a pH of 3 or lower.

Guanidine is highly basic (pKa 12.5), and a polar compound is formed by the oxidation of guanine. In the human body, guanine is a byproduct of protein metabolism and can be found in urine. Guanine can be retained by the cation-exchange mechanism on Primesep 100 column. Guanine is slightly UV active and can be observed at 200 nm. A better detection technique is ELSD, which allows you to see low concentrations of guanine. The temperature of the ELSD must be maintained relatively low to insure proper sensitivity of the method. This method can be used for analysis of other guanidine-based compounds. If substituted guanidine has hydrophobic properties, it will retain based on ion-exchange and reverse phase mechanisms.

Primesep 100 separates guanidine from its sodium counterion on a short 50 mm column by cation exchange. Guanidine is found in urine as a product of protein metabolism and is also used in the manufacture of plastics and explosives. Guanidine is detected by UV detection at 200 nm, but UV cannot detect the sodium ion. If an evaporative light scattering detector (ELSD) is used, both components can be detected. The separation method uses a mobile phase mixture of water, acetonitrile (MeCN, ACN) and trifluoroacetic acid (TFA).