Applicability of a commercial twisted-nematic liquid-crystal display is examined at approximately 400 nm. Different modulation modes predicted by Jones-matrix calculus are experimentally tested. High contrast amplitude modulation with negligible loss, high contrast and low loss hybrid ternary modulation, and 1.5pi continuous phase delay without intensity modulation and with low loss are presented. Simulation results of a 4f holographic system prove the usefulness of the high contrast for amplitude modulation, and the importance of pi phase difference between high transmission white levels in a hybrid ternary modulation.

Project Aquafluosense was designed to develop prototypes for a modular fluorescence-based instrumental setup for in situ measurement of major water quality parameters. A fluorometer was developed for algal density estimation based on the fluorescent excitation of chlorophyll. The appropriate type of sample holder microplate was determined, along with the need for dark acclimation, prior to the measurements during the instrument’s development. Model species of green (Raphidocelis subcapitata) and blue-green alga (Microcystis aeruginosa) were applied in forms of pure monocultures and their mixtures, and improved analytical limits of detection were achieved (3.70 × 103 cell/mL and 1.13 × 105 for R. subcapitata and M. aeruginosa, respectively). The fluorescence-based determination of algal density was validated by conventional methods, such as cell counting in a Bürker chamber, optical density measurement, and chlorophyll extraction with ethanol. The signals obtained by the fluorometer correlated well with the conventional methods. Pearson r coefficients (applied where the correlation was linear) were ≥0.988 and Spearman ρ coefficients (applied where the correlation was not linear) were >0.976, indicating a strong and positive correlation. The applicability of the developed fluorometer was demonstrated in a growth inhibition ecotoxicity assay on R. subcapitata using the herbicide active ingredient isoxaflutole. During the assay, light intensity (continuous, 104.9 ± 14.9 µE/m2/s), temperature (22 ± 2 °C), pH of algal media (pH = 6–7 for Zehnder and Allen media, as well), and intensity of stirring (continuous, 100 rpm) were controlled. The results indicated that the FluoroMeter Module is applicable for screening algal toxicity: the observed ratio of fluorescence decrease determined by fluorescence induction provided significantly lower toxicity values (EC50: 0.015 ± 0.001 µg/mL) compared to values determined by the optical density (EC50: 0.034 ± 0.004 µg/mL) and chlorophyll a content (EC50: 0.033 ± 0.000 µg/mL).

Project Aquafluosense is designed to develop prototypes for a fluorescence-based instrumentation setup for in situ measurements of several characteristic parameters of water quality. In the scope of the project an enzyme-linked fluorescent immunoassay (ELFIA) method has been developed for the detection of several environmental xenobiotics, including mycotoxin zearalenone (ZON). ZON, produced by several plant pathogenic Fusarium species, has recently been identified as an emerging pollutant in surface water, presenting a hazard to aquatic ecosystems. Due to its physico-chemical properties, detection of ZON at low concentrations in surface water is a challenging task. The 96-well microplate-based fluorescence instrument is capable of detecting ZON in the concentration range of 0.09–400 ng/mL. The sensitivity and accuracy of the analytical method has been demonstrated by a comparative assessment with detection by high-performance liquid chromatography and by total internal reflection ellipsometry. The limit of detection of the method, 0.09 ng/mL, falls in the low range compared to the other reported immunoassays, but the main advantage of this ELFIA method is its efficacy in combined in situ applications for determination of various important water quality parameters detectable by induced fluorimerty—e.g., total organic carbon content, algal density or the level of other organic micropollutants detectable by immunofluorimetry. In addition, the immunofluorescence module can readily be expanded to other target analytes if proper antibodies are available for detection.

An enzyme-linked fluorescent immunoassay (ELFIA) method has been developed for the quantitative analytical determination of the herbicide active ingredient glyphosate in environmental matrices (surface water, soil, and plant tissues). Glyphosate, as a ubiquitous agricultural pollutant, is a xenobiotic substance with exposure in aquatic and terrestrial ecosystems due its extremely high worldwide application rate. The immunoassay developed in Project Aquafluosense is part of a fluorescence-based instrumentation setup for the in situ determination of several characteristic water quality parameters. The 96-well microplate-based competitive immunoassay method applies fluorescence signal detection in the concentration range of 0–100 ng/mL glyphosate. Application of the fluorescent signal provides a limit of detection of 0.09 ng/mL, which is 2.5-fold lower than that obtained with a visual absorbance signal. Beside the improved limit of detection, determination by fluorescence provided a wider and steeper dynamic range for glyphosate detection. No matrix effect appeared for the undiluted surface water samples, while plant tissues and soil samples required dilution rates of 1:10 and 1:100, respectively. No cross-reaction was determined with the main metabolite of glyphosate, N-aminomethylphosphonic acid, and related compounds.

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