Methods to reduce sample carrier contamination for luminescence measurements

Abstract

Equivalent doses derived from sediment measurements void of signal contamination are essential for accurate optically stimulated luminescence (OSL) dating of sediments. We identified dose-dependent luminescence signals originating from new and previously used stainless steel cups used for OSL measurements. The signal is not eliminated under typical measurement conditions for sedimentary quartz including pre-heating, infrared stimulation, and OSL stimulation at 125°C. While signals from sample carriers are typically small sources of error they may strongly contaminate sediment with low OSL sensitivities. We tested several cleaning methods on used and new stainless steel cups by measuring OSL signals after increasing irradiation doses between 0 and 100 Gy. The lowest signal from sample carriers was observed from cleaning with HF, Alconox (a detergent for silicone oil removal), and methanol. The cleaning methods that produce the lowest signal from the cups were combined to create two modified cleaning procedures that are effective in reducing the unwanted luminescence signal. Our newly modified cleaning methods are capable of reducing the luminescence signal of empty stainless steel cups to near background levels.