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Biofilms in the oral cavity can be visualized by fluorescence and a common assumption is that the endogenously produced porphyrins in certain bacteria give rise to this fluorescence. Porphyrin content in oral bacteria has been sparingly investigated, and non-selective detection techniques such as utilizing the Soret fluorescence band of porphyrins are often used. In the present study, a quantitative and selective method for the determination of porphyrins in oral bacteria has been developed and validated using high performance liquid chromatography-tandem mass spectrometry. Lysis of bacteria using Tris-EDTA buffer together with ultrasonication showed high microbial killing efficiency ≥99.98 %, and sample clean-up using C18-solid phase extraction resulted in low matrix effects ≤14 % for all analytes. Using this method, the porphyrin content was determined in the two oral pathogens Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, as well as for baker’s yeast, Saccharomyces cerevisiae. Uroporphyrin, 7-carboxylporphyrin, 6-carboxylporphyrin, coproporphyrin, and protoporphyrin IX were identified in the investigated microorganisms, and it was shown that the porphyrin profile differs between the two bacteria, as well as for S. cerevisiae. To our knowledge, this is the first time the porphyrin profile has been determined for the bacterium A. actinomycetemcomitans.Graphical AbstractDetermination of porphyrins in oral bacteria.Electronic supplementary materialThe online version of this article (doi:10.1007/s00216-015-8864-2) contains supplementary material, which is available to authorized users.

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The need for inexpensive, time-averaged, quantitative determination of pesticides and other organic pollutants in whole water is not matched by the field sampling procedures available. Our new Time-Integrating, MicroFlow, In-line Extraction (TIMFIE) sampler comprises a low-tech syringe pump driven by a rubber band and connected to a flow restrictor enabling low microliter per minute water flow through a solid phase extraction (SPE) cartridge. This allows target compounds to be continuously extracted in the field over 1 week. The extracted water ends up in the syringe, where sample volume is accurately determined. TIMFIE followed by online SPE-LC-MS/MS determination was validated for 72 selected pesticides, and, except for three compounds, detection limit was 0.1−1 ng/L. In a field study, concentrations in TIMFIE samples and in grab samples were compared. Following TIMFIE sampling, on average 19 pesticides per sample were quantified, compared with nine pesticides per sample with grab sampling, as a result of the extra in-field concentration step. Duplicate TIMFIE sampling showed Pearson's correlation coefficient r = 0.998. Comparing concentrations from TIMFIE sampling to grab sampling resulted in ratios between 0.05 and 16.5 (mean 1.7; r = 0.532), demonstrating a discrepancy between the two sampling strategies and possible underestimation of chronic exposure by grab sampling.