No abstract

No abstract

No abstract

Archived water samples collected on the International Space Station (ISS) and returned to Earth for analysis have, in a few instances, contained trace levels of heavy metals. Building on our previous advances using Colorimetric Solid Phase Extraction (C-SPE) as a biocide monitoring technique [I-31, we are devising methods for the low level monitoring of nickel(ll), lead(l1) and other heavy metals. C-SPE is a sorption-spectrophotometric platform based on the extraction of analytes onto a membrane impregnated with a colorimetric reagent that are then quantified on the surface of the membrane using a diffuse reflectance spectrophotometer. Along these lines, we have determined nickel(l1) via complexation with dimethylglyoxime (DMG) and begun to examine the analysis of lead(l1) by its reaction with 2,5-dimercapto-I ,3,4-thiadiazole (DMTD) and 4-(2-pyridylazo)-resorcinol (PAR). These developments are also extending a new variant of C-SPE in which immobilized reagents are being incorporated into this methodology in order to optimize sample reaction conditions and to introduce the colorimetric reagent. This paper describes the status of our development of these two new methods.

A new approach to electrostatic ion deflection is described where an electrostatic particle guide (EPG) operating with reversed polarity is used to deflect ions in a cylindrical geometry about the axis of a time-of-flight mass spectrometer. The method has advantages over the standard parallel-plate deflector geometry in that it is more effective in deflecting ion beams that have a significant radial velocity component. The device is being used in (252)cs Cf plasma desorption mass spectrometry ((252)cs Cf -PDMS) experiments in an on/off mode to record neutral particle spectra and in a synchronized pulsed mode to reduce the magnitude of the uncorrelated background in the time-of-flight spectrum. Radial distribution functions have been measured for various EPG voltages. Its use as a background suppression technique is demonstrated by using the (252)cs Cf-PDMS spectrum of insulin. (28-36).