Preservation of accuracy and precision in the analytical practice of low power ICP-AES

In an inductively coupled argon plasma (ICAP) matrix effects caused by elements constituting major inorganic components in samples of widely different nature have been studied under experimental conditions not primarily aimed at achieving maximum detection power and minimum matrix effects but at optimum reproducibility of the analytical signals. Separate and combined matrix effects on thirteen ICAP analysis lines were investigated. From the results conclusions could be drawn of interest for the practice of ICP analysis. A close examination of acid effects revealed the appearance of an “adaptation” effect.     

Spectral-domain optical coherence phase microscopy for quantitative phase-contrast imaging

We describe a novel microscopy technique for quantitative phase-contrast imaging of a transparent specimen. The technique is based on depth-resolved phase information provided by common path spectral-domain optical coherence tomography and can measure minute phase variations caused by changes in refractive index and thickness inside the specimen. We demonstrate subnanometer level path-length sensitivity and present images obtained on reflection from a known phase object and human epithelial cheek cells.     

Intranasal irradiation with the xenon chloride ultraviolet B laser improves allergic rhinitis

We earlier reported that the 308 nm xenon chloride (XeCl) ultraviolet B (UVB) laser is highly effective for the treatment of inflammatory skin diseases. Since UVB irradiation has been shown to exert both local and systemic immunosuppression, we investigated the clinical efficacy of UVB irradiation in allergic rhinitis. In an open study, groups of patients with severe allergic rhinitis received intranasal irradiation with a 308 nm XeCl UVB excimer laser for two weeks. In the low-dose group (n=10), treatment was given twice weekly, starting with 0.25x the individual minimal erythema dose (MED), whereas patients in the medium-dose group (n=8) were treated four times weekly, starting with 0.4x MED. In each group, the dosage was gradually increased. Evaluation was based on the symptom scores. The effect of the XeCl laser on the skin prick test reaction was also studied. In the low-dose group, seven patients completed the study, and there was no improvement in the nasal symptoms. In the medium-dose group, the XeCl UVB irradiation significantly inhibited the rhinorrhoea, the sneezing, the nasal obstruction and the total nasal score (p<0.05). The XeCl UVB excimer laser also inhibited the allergen-induced skin prick test in a dose-dependent manner. These results suggest that the XeCl UVB excimer laser might serve as a new therapeutic tool in the treatment of allergic rhinitis.     

In vivo human retinal imaging by ultrahigh-speed spectral domain optical coherence tomography

An ultrahigh-speed spectral domain optical coherence tomography (SD-OCT) system is presented that achieves acquisition rates of 29,300 depth profiles/s. The sensitivity of SD-OCT and time domain OCT (TD-OCT) are experimentally compared, demonstrating a 21.7-dB improvement of SD-OCT over TD-OCT. In vivo images of the human retina are presented, demonstrating the ability to acquire high-quality structural images with an axial resolution of 6 microm at ultrahigh speed and with an ocular exposure level of less than 600 microW.     

In situ shear investigation of the Synperonic A7-water system by small-angle X-ray scattering and freeze fracture

A shear cell was constructed in two variants for simultaneous small-angle X-ray scattering and freeze fracture. Using this cell, the changes in the layer structure and the domain formation of the Synperonic A7-water system were investigated under shear. The reconstructions of both the layer and domain structures were not observed in the steady state after 1 h (following a 2 h long shear period). Destruction of the lamellar arrangement and formation of aggregates occurred during the stress. It was concluded that the tixotropic behavior originates rather from the change of the domain structure with a typical size range of microm than from the changes of the inner structure of domains with lamellar arrangement.     

Improved signal-to-noise ratio in spectral-domain compared with time-domain optical coherence tomography

A signal-to-noise ratio (SNR) analysis is presented for optical coherence tomography (OCT) signals in which time-domain performance is compared with that of the spectral domain. A significant SNR gain of several hundredfold is found for acquisition in the spectral domain. The SNR benefit is demonstrated experimentally in a hybrid time-domain-spectral-domain OCT system.     

Comparative tests to improve the gas chromatographic analysis of chlorobornanes in fish samples

A comparison was made between electron capture negative ionization quadrupole mass spectrometry (ECNI-MS) and electron capture detection (ECD) with regard to repeatability and reproducibility for the gas chromatographic (GC) analysis of toxaphene congeners [chlorobornanes (CHBs)]. The tests, including standard solutions and several cleaned fish extracts, showed larger relative standard deviations (RSDs) for the repeatability of ECNI-MS but no differences in the reproducibility of the 2 techniques. The sensitivity of the GC-ECNI-MS was considerably better than that of GC/ECD. Four stepwise-designed comparative tests were also conducted on GC analysis, cleanup, and the complete method. The results showed that, according to the current state-of-the-art, coefficients of variation for the between-laboratory performance were not < 20% and were usually between 20 and 30%. In spite of separation problems, e.g., for CHB 26, which cannot be separated into a single-component peak, a 95% methyl 5% phenyl polysiloxane (CP Sil 8) column was preferred to more polar columns for the analysis of CHBs 26, 40, 41, 44, 50, and 62. CHB 62 was more difficult to determine than CHB 26 and 50. Addition of the CHBs 40, 41, and 44 to the standard set of 3 chlorobornanes (26, 50, and 62) resulted in more separation problems. A 3-step cleanup method was recommended.