An Automated Hydrodynamically Mediated Technique for Preparation of Calibration Solutions via Capillary Electrophoresis System as a Promising Alternative to Manual Pipetting

In this paper, a novel procedure for preparing calibration solutions for capillary electrophoresis (CE)-based quantitative analysis is proposed. Our approach, named the automated hydrodynamically mediated technique (AHMT), uses a capillary and a pressure system to deliver the expected amount of working solution and diluent directly to a sample vial. As a result, calibration solutions are prepared automatically inside the CE instrument, without any or with minimal manual operation. Two different modes were tested: forward and reverse, differing in the direction of hydrodynamic flow. The calibration curves obtained for a model mixture of analytes using AHMT were thorough compared to the standard procedure based on manual pipetting. The results were consistent, though the volume of obtained calibration solutions and the potential risk of random errors were significantly minimized by AHMT. Its effectiveness was further enhanced by the application of SCIEX® nanoVials, reducing the actual volume of calibration solutions down to 10 μL.

Determination of water content in municipal sludge by multiple headspace extraction gas chromatography

This paper reports a new method for the determination of sludge water content by a multiple headspace extraction gas chromatographic (MHE-GC) method. It is based on the water vapor signals in the sample vial from the first five extractions.

Preconcentration and Determination of Lead by Solidification of Floated Organic Drop Coupled with Nanodrop Spectrophotometry

The liquid-phase microextraction based on solidification of floating organic microdrop coupled with UV-visible spectrophotometer for preconcentration and determination of lead in the aqueous samples has been developed. In this technique, 20μL of 1-undecanol containing dithizone as the chelating agent (10-3mol L-1) was transferred to the water samples containing lead ions, and the solution was stirred for 25 min. The sample vial was cooled in an ice bath for 5 min. The solidified extract was transferred into a conical vial where it melted immediately, and then the organic phase was analyzed by Nanodrop spectrophotometer. Factors that influence the extraction and complex formation, such as pH, concentration of dithizone, extraction time, effect of ionic strenght, temperature and stirring rate were optimized. Under the optimized conditions, a preconcentration factor of 356, detection limit of 0.006 μgL-1, limit of quantification 0.018 μgL-1and a good relative standard deviation of 2.1% were obtained. The procedure was applied to sea water, mineral water and well water.

Headspace Solid-Phase Microextraction for Ethyl Carbamate Determination in Table Wine Samples

Ethyl carbamate is a pluripotent carcinogen, and most fermented foods and beverages, including table wine, contain trace amounts of ethyl carbamate. The optimized parameters of the solid phase microextraction of table wine were: sample pH was 10.2, and 9.0 mL sample and 2.0-2.5 g (20-25%) sodium chloride were added to the vial; A 70 μm CW/DVB fiber was inserted into the headspace for 35 min at 40°C, then the fiber removed from the sample vial and inserted into the injection port of the GC for 10 min. Under this extraction conditions, the recoveries and the precision were 93.4-101.0% and 3.73-7.10%, respectively. The limit of detection was 3.0 μg/L. The solid phase microextraction technique was successfully applied to determine the EC levels in table wines. The extraction method was rapid and simple, and without the need for any organic solvent. It was an environmental protecting extraction method.

In situ SAXS/WAXS of Zeolite Microwave Hydrothermal Synthesis

ABSTRACTThe microwave hydrothermal synthesis of silicalite zeolite was monitored in situ using small and wide angle X-ray scattering (SAXS and WAXS). A custom-built waveguide reactor provided the microwave heating at 2.45 GHz frequency. Microwave power up to 300 W was supplied by a SAIREM generator via a coax connection. A sample port in the waveguide section allowed a thin-walled glass sample vessel to be held in the microwave field. The sample vial was sealed with a fiber optic temperature probe used for monitoring the temperature. Silicalite zeolite precursor solutions were heated temperatures between 100 and 130°C for up to 120 minutes. The SAXS or WAXS patterns were simultaneously scanned during the reaction under microwaves via X-ray beam through slots in the side of the waveguide. The progress of silicalite zeolite formation was followed and the analysis of SAXS patterns showed the primary particles of 2 nm shifted to aggregates of 5.8 nm in diameter, in 120 minutes at 130°C.

Stability of a New, Multichannel, Low-Level Liquid Scintillation Counter System, Kvartett

Kvartett is a new liquid scintillation counting (LSC) system for radiocarbon dating that takes a radical departure from conventional systems to obtain a compact, low-level counting system measuring four samples simultaneously. Each sample vial, inside the well of a large NaI(Tl) guard-counter crystal (facing down), sits on top of a vertical PMT. The fourfold counting capacity can be used to increase the number of samples being dated or to get higher precision. The increased throughput helps to keep a rigid quality-control standard. We monitored the background count rate almost continuously for 7 months, and measured the count rate of a standard repeatedly for 2 months. The results show the background and system reproducibility to be stable.