Electrothermal atomic-absorption spectrometric analysis of lake waters for Mn, Fe, Pb and Cd

Analyses have been made for trace metals in surface waters from lakes known to be sensitive to inputs of acidic deposition. Electrothermal atomic-absorption spectrometry was used for direct measurement of the low metal concentrations. The studies revealed non-spectral interferences resulting from small amounts of inorganic material in the sample matrix that prevent accurate measurements of Mn and Pb. Several types of interferences were identified by means of a computer coupled to the atomic-absorption spectrometer and procedures to overcome them were evaluated. Matrix modification with nitric acid is required for the determination of Mn. Atomization from a platform inserted within the graphite tube is necessary for interference-free Pb determination.     

Development of reference materials for the analysis of acid-extractable metals in sludge

The development of reference materials to verify the determination of metals in sludge is described. Effluents from domestic and industrial treatment facilities were dried, size-reduced and homogenized. Multiple aliquots of each material were analyzed in two different government laboratories to determine reference values for the acid-extractable concentrations of more than 15 metals. These acid-extractable concentrations are distinct from total metal values. Different sample preparation and instrumental methods, along with internal quality assurance protocols, were used to confirm the results. The data show good agreement for most metals in the domestic material. Reference values for the leachable concentrations of several toxic metals and major constituents will become part of the Certificate of Analysis for Standard Reference Material (SRM) 2781 issued by the National Institute of Standards and Technology (NIST). Data for the candidate industrial sludge reference material are also presented and discussed.     

rf Spectroscopy with a single Ba+ ion

We have employed the method of shelving to measure Zeeman resonances of a single trapped Ba+ ion. We use optical pumping to place the ion in a selected magnetic sublevel of either the 6S(1/2) ground state or the 5D(3/2) metastable state. The ion is exposed to an rf field, and a probing/shelving mechanism detects whether spin-flip transitions have taken place. We have observed rf transitions with linewidths of 15 Hz, limited by magnetic-field noise. We have also observed the shift in the Zeeman frequency when the ion is illuminated by off-resonant light. A simultaneous measurement of such light shifts in two atomic states of Ba+ will permit a precise determination of the ratio of transition matrix elements.     

The determination of lead in total suspended air particulates by x-ray fluorescence spectroscopy

A method has been developed for the measurement of lead in air particulates collected on glass fiber filter paper with wavelength-dispersive x-ray fluorescence spectroscopy (WDXRF). Analyses conducted by both WDXRF and an EPA-approved procedure that employs acid sonication followed by analysis of the extract by atomic-absorption spectroscopy (AAS) shows excellent agreement between the two methods. WDXRF calibration was accomplished with standards prepared from known additions of Pb to unexposed glass fiber filter discs. Method equivalency has also been demonstrated by the analysis of several reference materials and the statistical analysis of quality control data. The WDXRF procedure has also been used to evaluate the distribution of Pb in the particulates across the surface of the filter.     

Optical clocks based on ultranarrow three-photon resonances in alkaline Earth atoms

A sharp resonance line that appears in three-photon transitions between the 1S0 and 3P0 states of alkaline earth and Yb atoms is proposed as an optical frequency standard. This proposal permits the use of the even isotopes, in which the clock transition is narrower than in proposed clocks using the odd isotopes and the energy interval is not affected by external magnetic fields or the polarization of trapping light. With this method, the width and the rate of the clock transition can, in principle, be continuously adjusted from the MHz level to sub-mHz without loss of signal amplitude by varying the intensities of the three optical beams. Doppler and recoil effects can be eliminated by proper alignment of the three optical beams or by point confinement in a lattice trap. Light-shift effects on the clock accuracy can be limited to below a part in 10(18).     

Observation of the 1S0-3P0 transition in atomic ytterbium for optical clocks and qubit arrays

We report an observation of the weak 6 1S0-6 3P0 transition in (171,173)Yb as an important step to establishing Yb as a primary candidate for future optical frequency standards, and to open up a new approach for qubits using the 1S0 and 3P0 states of Yb atoms in an optical lattice.     

Industrial sludge reference material for the analysis of acid-extractable metals

An interlaboratory study describing the assignment of reference values to the extractable concentrations of metals in industrial sludge using NJDEP and USEPA methods is presented. Industrial waste containing high concentrations of alkali, alkaline earth, ferrous and transition metals was dried, size-reduced and homogenized. Multiple aliquots of this material were analyzed in two different government laboratories by several different combinations of extraction and analysis methodologies. Reference values for the acid-extractable concentrations of more than 15 metals were determined and will be included in the NIST Certificate of Analysis for SRM 2782, Industrial Sludge.