Undersized (12.5 mm diameter) glass beads with minimal amount (11 mg) of geochemical and archeological silicic samples for X‐ray fluorescence determination of major oxides

Abstract

The small glass bead technique was developed to assay precious silicic samples for geochemical and archeological analyses. Undersized (12.5 mm diameter) glass beads were prepared for wavelength dispersive X‐ray fluorescence determination of major oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, and total Fe2O3). Synthetic calibration standards were prepared by compounding chemical reagents (oxides, carbonates, and diphosphate). For reliable calibration, recipe compositions of standard specimens were constructed on the basis of the evenness of plot intervals on a calibration curve. Calibration curves showed good linearity (correlation coefficient: r > 0.998). Analytical results of major oxides in granitic and basaltic rocks, obsidian, and ancient pottery were obtained with good precision (relative standard deviations were the following: <3% for more than 10.0 mass% of analyte, <5% for 1.0–10.0 mass% of analyte, and <15% for 0.1–1.0 mass% of analyte). Lower limits of detection were roughly a sub‐percentage of analyte in an unprepared sample: 0.3 mass% for Na2O, 1.0 mass% for SiO2, 0.01 mass% for MnO, and so on. The present preparation reduced the following analytical scales: (1) amount of sample from 400 mg to 11 mg (97% cutting out), (2) amount of Li2B4O7 as an alkali flux from 4000 mg to 396 mg (90% cutting out), and (3) weight of platinum crucible from 80 g to 12.5 g (84% cutting out). This small‐scale preparation might enable us to conduct destructive pretreatment of valuable and limited silicic samples such as archeological ceramics and stone tools, geochemical minerals in rock, and sediments and sand. Copyright © 2012 John Wiley & Sons, Ltd.

Development of undersized (12.5 mm diameter) low‐dilution glass beads for X‐ray fluorescence determination of 34 components in 200 mg of igneous rock for applications with geochemical and archeological silicic samples

“…As a result, low‐dilution melt causes poor agitating and shaping performances. Therefore, the new specimen preparation, with 12.5 mm diameter and a 1 : 1 sample‐to‐flux ratio, should be more difficult in comparison with conventional glass beads (regular‐sized specimen with a 1 : 1 sample‐to‐flux ratio and undersized specimen with a 1 : 36 sample‐to‐flux ratio).…”

“…The undersized specimen was obtained using a high frequency electromagnetic fusion machine (Bead Sampler NT‐2000, Nippon Thermonics Co. Ltd.). As it was equipped with a quartz glass holder for the regular‐sized glass–bead crucible, a special holder had to be designed . A preheating step at around 900 °C for 120 s, followed by a melting step at around 1250 °C for 120 s, and an agitating step at 1200 °C for 120 s were used to create a molten mixture in the crucible.…”

“…As it was equipped with a quartz glass holder for the regular-sized glass-bead crucible, a special holder had to be designed. [9] A preheating step at around 900°C for 120 s, followed by a melting step at around 1250°C for 120 s, and an agitating step at 1200°C for 120 s were used to create a molten mixture in the crucible. The molten mixture was then vitrified by air cooling for 1-2 min; a glass disk was spontaneously released from the crucible.…”

“…As a result, low-dilution melt causes poor agitating and shaping performances. Therefore, the new specimen preparation, with 12.5 mm diameter and a 1 : 1 sample-to-flux ratio, should be more difficult in comparison with conventional glass beads (regular-sized specimen with a 1 : 1 sample-to-flux ratio [7] and undersized specimen with a 1 : 36 sample-to-flux ratio [9] ). In the present work, we optimized the preparation conditions, amount of powdered sample, alkali flux, and releasing agent, for the undersized glass beads with a 1 : 1 sample-to-flux ratio, in order to enable preparation of the specimen using various silicic samples such as rock, soil, clay, pottery, and so on.…”

Rapid Borate Fusion Pre-treatment for ICP-AES Determination of Tungsten in High-speed Steel

“…Despite the smaller dilution factor, the borate mixture was successfully vitrified. In this study, a large bottom crucible having about 35 mm in diameter 8,9) was used, but smaller bottom crucible (for example, 12.5 mm in diameter 10) ) might be preferable to fuse 0.40 g of the flux. No precipitates were observed during the working solutions in preparation of high-speed steel and calibrating standards.…”