LC-MS CHROMASOLV Solvents – Water and Pre-Blended Mobile Phase Additives
By: Shyam Verma, Reporter US Vol 27.1
Fast-LC methods or high-efficiency separations on HPLC systems, especially in combination with mass spectrometers, require high-quality solvents. High purity of chemicals for sample preparation, mobile phase, and post column treatment is necessary to meet demands on sensitivity, specificity, and speed of analysis.
Water is frequently used in LC-MS experiments as a solvent or a pre-blended mobile phase additive. Impurities in a mobile phase solvent are the most common source of extraneous peaks and unstable LC-MS baselines. Solvent driven impurities do not condition out over time. Potential LC-MS contaminants from water may include inorganic ions, microbes, and the compounds they excrete, particulate matter from improper filtration and precipitation, compounds adsorbed from the atmosphere, and packaging materials. These contaminants adversely impact the analysis by: 1) collecting on the head of the HPLC column and elute as a distinct peak or as baseline rise, 2) causing lower sensitivity, 3) damaging sensitive instrument components, and 4) resulting in cluster ion formation that prevents reliable identification and quantification.
Sigma-Aldrich offers LC-MS CHROMASOLV Water with quality suitable for both gradient HPLC and MS applications. This product offers tremendous advantages over other quality grades. It can be used in both UV and MS detection methods, without any compromise. Figure 1 clearly shows differences between LC-MS CHROMASOLV Water and non-gradient grade water.
Figure 1. UV Gradient at 205 nm, LC-MS Water (Cat. No. 39253) and Non Gradient Grade Water
The mobile phase composition plays a critical role in the success of an LC-MS experiment. Precise formulations provide accurate and reproducible results. Sigma-Aldrich offers pre-blended solutions of most commonly used LC-MS mobile phases prepared with precision and unsurpassed attention to quality. The water quality mentioned above also applies to all its blends. These pre-blended solvents offer: 1) time savings, 2) accurate composition, 3) minimized baseline and artifacts, and 4) ensured high quality.
LC gradient testing in UV and MS, metal impurities (Na<2 ppm, K, Mg, Ca <0.5 ppm), UV-transmittance, additive content: 0.93-0.107TFA, FA, AA (v/v), ammonium acetate (w/v), pH: effective +/- 0.1.
Acetonitrile and Methanol Blends:
LC gradient testing in UV and MS – similar to water blends; solvent content: (GC): >99.0% (Cat. No. 34669 – acetonitrile with 0.1% ammonium acetate; solvent content (GC)>98%).
The LC-MS solvents undergo 34 distinct tests to ensure quality for sensitive LC-MS analyses. Detailed analysis is available at sigma-aldrich.com/lc-ms-solvents