Determination of trace quantities of aluminum and chromium in uranium by gas phase chromatography

Rapid simultaneous determination of picogram quantities of aluminum and chromium from water by gas phase chromatography

“…The chelation of chromium occurs over a broad pH range (5) using a very large excess of chelating agent (6), whereas quantitative aluminum chelate formation requires a pH of about 5.5 (1,7). The chromium chelate is also quantitatively formed at 150-175 °C using a dilute hexane solution of the chelating agent (8), but in this work it was discovered that the aluminum chelate is destroyed at temperatures above 100 °C, with or without a buffer, and at 60-70 °C hexane and cyclohexane are inefficient in the extraction of the chelates, being about 10% low for both metals for a single extraction.…”

“…Buffering the system and using benzene as the extracting medium solves most of these problems. However, in attempting to use the buffer system reported by Genty et al (1), it was soon realized that chromium was not being completely extracted with one extraction at elevated temperatures, and that the components of the buffer system, which would seriously impair the sensitivity of the detector, were relatively slow in being washed from the sample prior to injection. Use of a less concentrated buffer system, and the use of sodium acetate in place of ammonium acetate solved both of these problems.…”

“…The aluminum chelate does deteriorate significantly over several hours of quiet contact time, and a portion of the chromium chelate is destroyed in seconds; noticeable in the 10~12 g Cr/µ range. If this demonstrates that ammonia can successfully compete with the chelate for chromium, it explains, the need to do a triple extraction when an ammonium acetate buffer system is employed (1).…”

“…The constants k i and k 2 were determined from the standard curve. Injection of a log c = k1 log h + k2 (1) known after every suite of four samples (every 12 minutes) was more than adequate to follow the drift in sensitivity. If the peak height of the standard varied more than 2%, a new value for k 2 was rapidly computed, or taken from a previously computed table, and used to determine the concentrations (c) from the peak heights (h) of the samples.…”

“…RECEIVED for review February The simultaneous analysis of aluminum and chromium has been reported by Genty and coworkers (1), but the procedure is lengthy, requires repeated handling, and, as a consequence the accuracy and precision, though good, suffers some deterioration. In our efforts to adapt fluorinated metal chelate gas chromatography to natural water samples, we have developed the improved procedure described in detail in this report.…”