Featured Application: Creatine and Creatinine in Plasma and Urine on Raptor HILIC-Si
Fast, Simple LC-MS/MS Analysis of Creatine
- Simple isocratic method, no complex mobile phases.
- Fast, 1.5 min analysis without additional equilibration time.
- Highly reproducible results.
Creatine is a compound that is made primarily in the liver and then transported to muscles where it is used as an energy source. Once in the muscle, some of the creatine is spontaneously converted to creatinine. It is important to monitor creatine and creatinine because these compounds can be used as biomarkers of renal, liver, and heart health. Historically, colorimetric and enzymatic assays have been used, but LC-MS/MS is a better technique because it reduces interferences. Although LC-MS/MS analysis of creatine and creatinine using an alkyl-bonded (e.g., C18) column is the usual approach, these highly polar analytes are very difficult to retain and separate from each other using a reversed-phase column. When a reversed-phase method is employed, complex ion-pairing reagents (e.g., tetrabutylammonium hydroxide) are generally required to increase analyte hydrophobicity.
Using HILIC, ion-exchange, or other newer LC phases can be a better alternative to reversed-phase methods because these phases employ different mechanisms of interaction. Some non-C18 columns do provide increased retention, but analysis times can be long (e.g., 10 min) and may require the use of complex mobile phases and gradients. Labs needing faster LC-MS/MS analysis of creatine and creatinine should consider adopting the HILIC method shown here. Good separations in both plasma and urine samples were obtained in just 1.5 min using a Raptor HILIC-Si (2.7 μm, 50 mm × 2.1 mm) column and a simple, isocratic mobile phase. Results during in-house testing were highly reproducible, making this fast, simple LC-MS/MS analysis a good procedure for high-throughput labs.