No abstract

A simple, uncontaminated method was described for graphite furnace atomic absorption spectrophotometry used for determination of Cd and Pb in milk serum prepared by spontaneous souring. Samples of raw milk were collected from the bulk holding tanks of 107 dairy farms in six counties in Taiwan. Raw milk samples were placed at room temperature (28 degrees C) for 48 h, to allow the pH to decrease below 4.6 and the casein and fat to precipitate. Milk serum was filtered and then directly injected into a graphite tube. The standard addition method was employed, and .1% phosphoric acid was the matrix modifier. During ashing, a 15-s oxygen influx prevented charcoal accumulation on the graphite tube. The mean recoveries of Cd and Pb from three added concentrations were 93.7% and 94.5%, respectively. The analyzed Cd and Pb concentrations in milk powder using this method were close to the certified values. The mean Cd and Pb contents obtained from 107 samples were .044 ng/ml, ranging from .021 to .173, and 2.03 ng/ml, ranging from .98 to 4.45, respectively. There were no significant differences among the six counties.

Direct analysis of airborne particulate matter collected on PTFE-membrane filters using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS ) was performed. Laboratory prepared standard filter samples were analyzed. Several parameters, including the laser energy, pulse type and beam focus, thermal properties and homogeneity of the sample and the carrier gas flow rate, may affect the LA-ICP-MS measurement. The influences of these parameters were thoroughly examined. Empirical results obtained here demonstrated that applying LA-ICP-MS for multi-element analysis of airborne particulate matter collected on PTFE-membrane filter is feasible. More than 20 major, minor and trace elements in airborne particles on PTFE membrane filters can be determined. It was found that the optimum ablation efficiency can be achieved using a 160 mJ single shot laser operated in the free-running mode with a 6.5 mm defocus distance from the filter surface. The optimum transport efficiency for most of the elements can be obtained if the argon gas flow rate is kept at 0.8 L min−1.employed LA-ICP-MS to determine simultaneously 21

This study reports the analysis of Si in airborne particulate matter by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as well as X-ray fluorescence (XRF). It was found that Si concentration in airborne particulates collected on PTFE-membrane filters could be accurately determined with a laser beam operated at 160 mJ free running mode, 6.5 mm defocusing distance and 0.8 l/min carrier gas flow rate during the LA-ICP-MS measurement. Standard filters prepared by NIST SRM 1648 urban particulates were used for both XRF and LA-ICP-MS not only to establish the calibration curves of Si, but also to examine the proposed method's effectiveness. The capability of applying both methods for natural sample analysis was also examined. Particulate loaded filter samples collected from a heavily polluted metropolitan area of Kaoshiung, Taiwan were initially measured by XRF, then by LA-ICP-MS. An intercomparison between them was thus performed. As a result, both XRF and LA-ICP-MS proved to be the valid analytical methods for directly determining Si concentrations in airborne particulates on PTFE membrane filters.

No abstract