Noise reduction by multiple referencing in surface plasmon resonance imaging.

The analytical performance of surface plasmon resonance imaging with charge coupled device detection can be improved significantly by splitting a macroscopic sensing surface into multiple microscopic neighboring sensing and referencing subareas. It is shown that such a multiple referencing reduces intensity fluctuations across the total sensing area and, therefore, improves the signal/noise (S/N) ratio proportional to the splitting factor. The approach is demonstrated by detection of biotin binding to a monolayer of streptavidin.

Recent applications of near-infrared spectroscopy in cancer diagnosis and therapy.

In recent years, near-infrared spectroscopy (NIRS) has gained importance for non-invasive or minimally invasive diagnostic applications in cancer. This technology is based on differences of endogenous chromophores between cancer and normal tissues using either oxy-haemoglobin or deoxy-haemoglobin, lipid or water bands, or a combination of two or more of these as diagnostic markers. These marker bands provide a basis for the diagnosis and therapy monitoring of several cancers.

Bedside monitoring of subcutaneous interstitial glucose in healthy individuals using microdialysis and infrared spectrometry.

An IR-spectroscopy-based bedside device, coupled to a subcutaneously implanted microdialysis probe, is developed for quasicontinuous glucose monitoring with intermittent readouts at 10-min intervals, avoiding any sensor recalibration under long-term operation. The simultaneous estimation of the microdialysis recovery rate is possible using an acetate containing perfusate and determining its losses across the dialysis membrane. Measurements are carried out on four subjects, with experiments lasting either 8 or 28 h, respectively.

Enhancement of the detection power of surface plasmon resonance measurements by optimization of the reflection angle.

The detection limit of surface plasmon resonance (SPR) measurements has been improved by a factor of approximately 2-3.5 if the angle of incidence was near to the reflection minimum of the SPR resonance curve instead at the position of the steepest slope, the standard alignment in SPR imaging. The enhancement of the detection power, a result of signal-to-noise optimization, is demonstrated by applying a photodiode and a CCD camera for SPR detection.

Recent progress in analytical instrumentation for glycemic control in diabetic and critically ill patients.

Implementing strict glycemic control can reduce the risk of serious complications in both diabetic and critically ill patients. For this reason, many different analytical, mainly electrochemical and optical sensor approaches for glucose measurements have been developed. Self-monitoring of blood glucose (SMBG) has been recognised as being an indispensable tool for intensive diabetes therapy.

Differential surface plasmon resonance imaging for high-throughput bioanalyses.

A new imaging technique for high-throughput surface plasmon resonance (SPR) measurements is described. It is the application of a CCD camera for simultaneous processing of two images at two different wavelengths provided by two laser diodes. The two lasers are brought to resonance by tuning of the angle of incidence so that the detection power and the dynamic range are optimized for the wavelength pair selected.

Infrared transmission spectrometry for the determination of urea in microliter sample volumes of blood plasma dialysates.

Application of mid-infrared spectroscopy for the determination of urea in blood plasma dialysates of microliter sample volumes using a transmission microcell was investigated. Infrared spectra of the dialysates of plasma samples collected from 75 different patients using CMA 60 microdialysis catheters were evaluated with multivariate partial least squares regression. Using the absorbance spectral data from 1520-1420 cm(-1) and 1220-1120 cm(-1), a minimum standard error of prediction (SEP) of 0.

Production of ultrafine particles by nanosecond laser sampling using orthogonal prepulse laser breakdown.

The particle size distribution and composition of nanosecond laser-generated aerosols from brass samples in atmospheric argon has been measured by low-pressure impaction and subsequent quantitative analysis of the aerosols by total reflection X-ray fluorescence. Ablation was performed applying a Nd:YAG laser at 1.06 microm both without and with a prepulse plasma breakdown generated by a second Nd:YAG laser at 2-60 micros prior to the ablation pulse.

Spectral variable selection for partial least squares calibration applied to authentication and quantification of extra virgin olive oils using Fourier transform Raman spectroscopy.

The limits of quantitative multivariate assays for the analysis of extra virgin olive oil samples from various Greek sites adulterated by sunflower oil have been evaluated based on their Fourier transform (FT) Raman spectra. Different strategies for wavelength selection were tested for calculating optimal partial least squares (PLS) models. Compared to the full spectrum methods previously applied, the optimum standard error of prediction (SEP) for the sunflower oil concentrations in spiked olive oil samples could be significantly reduced.