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A three-dimensional structure was constructed to demonstrate contact-free liquid addition and distribution to a conventional centrifugal microfluidic platform. The structure allowed a continuous stream of liquid to be added to the rotating platform where it was dispensed and metered to a series of reservoirs with 9% relative standard deviation of the volume. An off-platform generated gradient was used to demonstrate this design's potential to make gradient centrifugal microfluidic chromatography possible without the use of platform space for liquid storage. The system demonstrates a convenient and versatile 'World-to-Chip' or more appropriately, World-to-Disk, macro-to-micro interface. 10.1021/ac1024478

A prototype for solid sample preparation on centrifugal microfluidic devices has been designed and characterized. The system uses NdFeB magnets in both the centrifugal device and a fixed base. As the centrifugal device rotates, the magnets move and spin in their chambers creating a pulverizing mechanical motion. This technique was successfully applied to the dissolution of potassium ferricyanide ([K.sub.3][Fe[(CN).sub.6]), a hard colored crystal. A 0.10 g sample was completely dissolved in 3 s in 1.0 mL of water while rotating at 1000 rpm. This is a 300-fold improvement over static dissolution.

Abstract: We describe the inductively heated electrothermal vaporization of 8-hydroxyquinolne complexes of Cd, Pb, and Zn adsorbed onto [C.sub.18]-bonded silica gel with inductively coupled plasma atomic emission spectroscopic detection. The [...]

A high-pressure microwave digestion system has been designed based on the concept of using large-bore tubes as digestion vessels and capsules as a vehicle for sample introduction. Many of the design aspects are dictated by the use of a relatively large (8.4 mm o.d., 25 mm long) capsule, which in turn dictates the inner tube dimensions. A variety of materials were studied for use as the tubing material. PFA was selected as the best material for a demonstration arrangement. The cycle of operation involves insertion of the capsule by a flexible rod followed by addition of digestion reagent and then a heating/cooling/venting cycle for removal of gases. When the digestion is completed, the system removes the liquid with the same flexible rod and then cleans itself. The system is highly automated with computer-controlled venting, cooling, and reagent addition. Data indicate that performance is similar to that expected of a conventional microwave oven operated at the same temperatures.

This paper describes a pumping technique applicable to centrifugal microfluidic platforms, involving the use of a regulated stream of compressed gas to pump liquid radially inward and toward the center of the platform while spinning. This technique provides a noncontact method for pumping fluids and is highly efficient, requiring only approximately 60 s to reach completion. This pumping operation can be attained with an applied gas flow rate of 58.8 L [min.sup.-1], while the platform is rotated at frequencies less than 180 rpm (3.0 Hz). 10.1021/ac102071b

It is of considerable importance to be able to distinguish metallic species because their toxicity depends on their chemical form. Therefore, the analysis of environmental samples can be enhanced by the combination of high-performance thin-layer chromatography (HPTLC) with laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). In this study, [Cr.sup.3+] and [Cr.sup.6+] were separated on silica gel HPTLC plates using aqueous mobile phases. Separation was achieved in seconds with retardation factors ([R.sub.f]) of 0 and 1 for [Cr.sup.3+] and [Cr.sup.6+], respectively. LA was used to volatilize the chromium species directly from the chromatographic material prior to ICPMS detection. A linear calibration was obtained, and detection limits (3[sigma]) of 6 ng for [Cr.sup.6+] and 0.4 ng for [Cr.sup.3+] were achieved with precision ranging from 3 to 40% at the 95% confidence level. The silicon present in the stationary phase was used as an internal standard. This procedure allows for a rapid separation and quantification, requires only 0.5 [micro]L of sample, and lower detection limits can be achieved through preconcentration.

Describes an experiment designed to teach students to apply the same statistical awareness to instrumentation they commonly apply to classical techniques. Uses propagation of error techniques to pinpoint instrumental limitations and breakdowns and to demonstrate capabilities and limitations of volumetric and gravimetric methods. Provides lists of experimental procedures and equipment. (JM)