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• General information about MALDI analysis

  The MALDI analysis is a diagnostic tool, not a precise quantitative method. It cannot be used to confirm purity or identity of a compound, but it is great for fast analysis/comparison of multiple closely related samples. It consists of two parts: sample preparation and analysis using a mass spectrometer.
  
  The sample preparation is the most important part; it generally involves selection of an appropriate matrix, solvents, and methods for co-crystallization of analytes with a matrix compound on a plate. While our staff can help you with general guidance, it is the end user’s job to find the optimal conditions for the samples. While it might feel a little bit overwhelming and time consuming at the beginning, after the optimal conditions are found for a certain type of compounds, they can be used repeatedly.
  
  The second part involves analysis of the prepared samples using a mass spectrometer. The Bruker ultrafleXtreme mass spectrometer uses a 384 target plate. It is also capable of performing analysis in fully automated mode. The automated mode is highly customizable and can be fitted to your research project. It takes ~20 minutes to run one plate (384 samples) and to save results as pdf files. If your run requires additional adjustments, (e.g., calibration, laser intensity, beam position), it will take longer but the instrument can do it all by itself. That said, there is nothing wrong with analysis of a single sample or a small number of samples.

• How to get started with MALDI

  If you are curious about MALDI but not sure if it is the right fit for your research, please contact us. Our staff is available to give you a tour of the facility or a short presentation at your group meeting. Even if you do not need MALDI at the moment, keep in mind that easy access to the latest MALDI analytical instrumentation may allow you to start new research projects that were not feasible before.
  
  When or if you are ready to start using MALDI, your lab should purchase a target plate from Bruker. There are a few types but a ground steel plate (Part No.: 8280784) is a good first choice. If you prefer to try before you buy, our facility has two types of plates (ground steel and polished steel) available for you to try out.
  
  Using an appropriate matrix/technique, prepare your samples. At this point you may want to add some sort of standard or known compound to the plate as well. There are multiple techniques/conditions for sample preparation for MALDI analysis; it is a good idea to try as many as possible if you are just getting started.
  
  Once your plate is ready, reserve a time slot at https://calendly.com/uhms.

• How to prepare a sample for MALDI analysis

  Three factors are important for the success in MALDI: the matrix, sample/matrix concentrations, and preparation technique.
  
  The most popular matrix is α-cyano-4-hydroxycinnamic acid, but many different matrices are available and widely used. The best approach is to check the literature to determine a good starting point. Our facility has some common matrices in stock.
  
  In general, the analyte should be soluble to at least about 0.1 mg/mL in some solvent. (But MALDI analysis of insoluble compounds is possible!) The solvent should have a normal evaporation rate: a drop of 1 μL should evaporate in 5-10 min at room temperature. A matrix is dissolved in the same solvent to yield either a saturated solution or a concentration of about 10 mg/mL. Around 0.5-1.0 μL of the analyte/matrix mixture is spotted onto a metal target plate for analysis and allowed to dry. After drying, the mixture of the sample and the matrix co-crystallize to form a solid deposit of the sample embedded in the matrix. It is generally believed that the analyte is quite stable in the matrix; the sample plate can be prepared well in advance and stored for an extended period of time as long as any form of cross contamination is avoided. After you have prepared your plate, remember to keep it dry. Use some desiccant (e.g., USPak Silica Gel packets, 100 packets for ~$10 from Amazon), and a desiccator or a plate case to store your plate.
  
  Remember, if your sample plate is not completely dry, once you place it into the instrument under high vacuum, the remaining solvent will evaporate instantly, destroying your samples and contaminating the instrument.