Plant Analysis Made Simple

Analyzing the chemicals within a plant is now as easy as snipping a leaf and jolting it with electricity. Researchers report a method called leaf spray to quickly ionize chemicals within or on the surface of plants for analysis by mass spectrometry (Anal. Chem., DOI: 10.1021/ac2020273).

Zheng Ouyang, R. Graham Cooks, and their colleagues at Purdue University develop mass spectrometry techniques to study biological samples with little sample preparation. After the researchers devised a method that ionizes biological samples adsorbed onto wet paper, called paper spray, they realized they could adapt the technique to study plants, Ouyang says.

Both the paper and plant techniques rely on applying an electrical potential across a wet surface to produce a spray of ionized chemicals within tiny liquid droplets. In the plant technique, the scientists attach copper clips to the plant tissue, apply a 4.5 kV jolt to it, and aim the tissue’s spray of chemicals at the inlet valve of a mass spectrometer.

To obtain better quality data, the researchers sometimes make small cuts in the plant tissue to give it a point. But otherwise the method is non-invasive. Also the only solvent needed is an occasional spritzing of water.

The researchers used the technique to analyze leaves, roots, seeds, and fruits from several types of plants, including green onions, peanuts, and cranberries. The method even worked on living potato and tomato plants.

With the technique, Ouyang and his team could measure alkaloids, sugars, lipids, amino acids, and other compounds in the plant tissues. Sample preparation takes seconds, which could allow researchers to routinely measure rapid chemical changes within plants, such as responses to stress. Traditionally, such studies have involved time-consuming sample preparation including chromatography, Ouyang says. “We want to make it really simple.”