Spectrochimica Acta Part B: Atomic Spectroscopy
Laser-induced breakdown spectroscopy, Bacteria concentration, Centrifugation, Filter
A metal cone device has been designed and fabricated for use with a custom centrifuge tube insert to allow the simple and rapid concentration of bacterial cells in a circular area with a diameter of 1 mm. The device concentrates cells suspended in up to 1 mL of liquid at the center of a highly flat disposable filter medium which can be easily removed from the centrifuge tube insert for subsequent testing with laser-induced breakdown spectroscopy. Two-dimensional elemental mapping of the filter evidenced a high concentration of bacteria on the filter under the location of the cone hole, as well as detection of reduced bacterial signal in peripheral areas slightly outside the footprint of the cone hole indicating some leakage of bacteria. Nine different dilutions of a suspension of E. coli were prepared and after measurement of the titer by optical densitometry, deposited on the filter media using the cone concentrator. A calibration curve constructed from forty spectra obtained from each of the nine different concentrations returned a LIBS bacterial limit of detection of 10,865 3,712 CFU per laser ablation event for bacteria deposited on filters using the metal cone. Limits of detection calculated using only certain elements observed in the LIBS spectra and present in very low concentrations in the filter were even lower: 1,070 272CFU for magnesium and 1,784 657 CFU for calcium. This represents a factor of 50 reduction in the limit of detection compared to our previously reported value.
Paulicka, Alexandra E.; Malenfanta, Dylan J.; and Rehse, Steven J.. (2019). Concentration of Bacterial Specimens During Centrifugation Prior to Laser-Induced Breakdown Spectroscopy Analysis. Spectrochimica Acta Part B: Atomic Spectroscopy, 157, 68-75.