Quantitative surface-enhanced Raman spectroscopy of dipicolinic acid - towards rapid anthrax endospore detection

Steven Bell, J.N. Mackle, N.M.S. Sirimuthu

Research output: Contribution to journalArticlepeer-review

138 Citations (Scopus)

Abstract

Dipicolinic acid (DPA) is an excellent marker compound for bacterial spores, including those of Bacillus anthracis ( anthrax). Surface-enhanced Raman spectroscopy (SERS) potentially has the sensitivity and discrimination needed for trace DPA analysis, but mixing DPA solutions with citrate-reduced silver colloid only yielded measurable SERS spectra at much higher (> 80 ppm) concentrations than would be desirable for anthrax detection. Aggregation of the colloid with halide salts eliminated even these small DPA bands but aggregation with Na2SO4(aq) resulted in a remarkable increase in the DPA signals. With sulfate aggregation even 1 ppm solutions gave detectable signals with 10 s accumulation times, which is in the sensitivity range required. Addition of CNS- as an internal standard allowed quantitative DPA analysis, plotting the intensity of the strong DPA 1010 cm(-1) band (normalised to the ca. 2120 cm(-1) CNS- band) against DPA concentration gave a linear calibration (R-2 = 0.986) over the range 0 - 50 ppm DPA. The inclusion of thiocyanate also allows false negatives due to accidental deactivation of the enhancing medium to be detected.
Original languageEnglish
Pages (from-to)545-549
Number of pages5
JournalAnalyst
Volume130
Issue number4
DOIs
Publication statusPublished - Apr 2005

ASJC Scopus subject areas

  • Analytical Chemistry

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