Water analysis

A single probe for solvent dependent optical recognition of iron(II/III) and arsenite: discrimination between iron redox states with single crystal X-ray structure evidence

The detection and discrimination of Fe2+ and Fe3+ ions have been investigated using a simple probe (L), produced by the condensation of ethylenediamine and 3-ethoxysalicyaldehyde. Single crystal X-ray structures demonstrate that L interacts with Fe2+ and Fe3+. In aqueous-DMSO media, the L recognises AsO2- by fluorescence and colorimetry techniques. The AsO2- aided PET inhibition and H-bond assisted chelation enhanced fluorescence (CHEF) boost fluorescence by 91-fold. The L can detect 0.354 ppb Fe2+, 0.22 ppb Fe3+ and 0.235 ppt AsO2-.

Sequential Fluorescence Recognition of Molybdenum(VI), Arsenite, and Phosphate Ions in a Ratiometric Manner: A Facile Approach for Discrimination of AsO2 - and H2PO4. ACS OMEGA 2019;4:10877-10890. [PMID: 31460185 PMCID: PMC6648501 DOI: 10.1021/acsomega.9b00377]

An amide-based smart probe (L) is explored for nanomolar detection of Mo(VI) ion in a ratiometric manner, involving hydrogen-bond-assisted chelation-enhanced fluorescence process through inhibition of photoinduced electron transfer process. The recognition of Mo(VI) is associated with a 17-fold fluorescence enhancement and confirmed by single-crystal X-ray diffraction of the resulting Mo(VI) complex (M1). Further, M1 selectively recognizes arsenite through green emission of their adduct (C1) with an 81-fold fluorescence enhancement. Interestingly, dihydrogen phosphate causes dissociation of C1 back to free L having weak fluorescence. The methods are fast, highly selective, and allow their bare eye visualization at physiological pH. All of the interactions have been substantiated by time-dependent density functional theory calculations to rationalize their spectroscopic properties. The corresponding lowest detection limits are 1.5 × 10-8 M for Mo(VI), 1.2 × 10-10 M for AsO2 -, and 3.2 × 10-6 M for H2PO4 -, whereas the respective association constants are 4.21 × 105 M-1 for Mo(VI), 6.49 × 104 M-1 for AsO2 -, and 2.11 × 105 M-1 for H2PO4 -. The L is useful for efficient enrichment of Mo(VI) from aqueous solution, while M1 efficiently removes AsO2 - from environmental samples by solid-phase extraction.

Dual anion colorimetric and fluorometric sensing of arsenite and cyanide ions

A naphthalene appended probe, 2-((2-hydroxynaphthalen-1-yl)methylene)hydrazine carbothioamide, was synthesized and found to recognize AsO₂⁻ and CN⁻ ions with turn-on emission fluorescence over different anions in DMF–H₂O (HEPES buffer, 7.2 pH) (9 : 1, v/v solution) medium.

Thiol-tolerant assay for quantitative colorimetric determination of chloride released from whole-cell biodehalogenations

Determination of inorganic chloride released from a chloro-organic compound by whole-cell or enzymatic dehalogenation can be affected by free thiols, phosphate, sugars, pH, the chloro-organic substrate, and its dehalogenation product. For these reasons a highly sensitive, colorimetric chloride assay on the basis of [FeCl]2+ (lambda(max) = 340 nm) formed in highly acidic medium which is insensitive to composition of culture medium, free thiols, substrate, and dehalogenation product was developed. It is applicable to both fungal and bacterial high-cell-density cultures. The [FeCl]2+ method provides reliable data and is convenient for the rapid and facile determination of dehalogenation kinetics.

Identification of the culturable and nonculturable bacterial population in ground water of a municipal water supply in Germany

AIMS

The identification of the culturable and nonculturable bacterial population in ground water of a municipal water supply in Mainz (Germany) during the year 2002.

METHODS AND RESULTS

Total counts varied between 3.5 x 103 and 2.2 x 104 cells ml-1, viable counts were approximately between 8.1 x 102 and 3.3 x 103 cells ml-1. After cultivation on different nutrient media (R2A, DEV, PCA, Endo, Standard) <1% appeared to be culturable on the media used. After denaturating gradient gel electrophoreses, up to 24 different bacterial species were detected in the ground water. With the aid of 16S rDNA isolation, amplification and sequencing, the isolated organisms and clones could be identified.

CONCLUSIONS

The isolated and cultured organisms mainly belonged to the Proteobacteria (alpha, beta and gamma), Flavobacteria or Actinobacteria. However, most of the noncultured micro-organisms were beta-Proteobacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study in which the identification of all culturable and nonculturable bacteria in a ground water has been attempted.

Optical sensors for detection of bacteria. 1. General concepts and initial development

The concept of using immobilized nucleic acid stains as detection chemistry to fabricate optical bacterial sensors is first demonstrated. SYTO 13 (a green fluorescent cell stain) is used as the molecular recognition element and fluorescent reporter in the sensor. The sensor responds to aqueous and aerosolized bacterial samples in 15 and 30 min, respectively. In addition, the sensor can discriminate a change in Pseudomonas aeruginosa (Pa) cell concentration of 1 order of magnitude or less and can detect down to 2.4 x 10(5) cells/mL of Pa cells. The utility of the sensor is demonstrated by monitoring the growth of a Pa cell culture over a period of 50 h.