Sample mineralisation

In ICP-AES and ICP-MS, sample mineralisation is the Achilles heel. Sample introduction systems for ICP-AES are numerous gas-phase introduction, pneumatic nebulisation (PN), direct-injection nebulisation (DIN), thermal spray, ultrasonic nebulisation (USN), electrothermal vaporisation (ETV) (furnace, cup, filament), hydride generation, electroerosion, laser ablation and direct sample insertion. Atomisation is an essential process in many fields where a dispersion of liquid particles in a gas is required. Pneumatic nebulisation is most commonly used in conjunction with a spray chamber that serves as a droplet separator, allowing droplets with average diameters of typically <10 xm to pass and enter the ICP. Spray chambers, which reduce solvent load and deal with coarse aerosols, should be as small as possible (micro-nebulisation [177]). Direct injection in the plasma torch is feasible [178]. Ultrasonic atomisers are designed to specifically operate from a vibrational energy source [179]. 

ThioglycoHc acid can be identified by its in spectmm or by gas chromatography. Most of the by-products and self-esterification products are also detected by liquid chromatography, eg, thiodiglycolic acid, dithiodiglycolic acid, linear dimers, and polymers. Iron content can be assayed by the red sensitive complex of 1,10-phenanthroline [66-71-7] and ferrous ion of a mineralised sample. Ferric ion turns an aqueous ammonia solution deep red-violet. 

Destructive solid sample preparation methods, such as digestion and mineralisation, are well known as they have been around for some time they are relatively cheap and well documented [13-15]. Decomposition of a substance or a mixture of substances does not refer so much to the dissolution, but rather to the conversion of slightly soluble substances into acid- or water-soluble (ionogenic) compounds (chemical dissolution). 

The metal content analysis of the samples was effected by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES Varian Liberty II Instrument) after microwaves assisted mineralisation in hydrofluoric/hydrochloric acid mixture. Ultraviolet and visible diffuse reflectance spectroscopy (UV-Vis DRS) was carried out in the 200-900 nm range with a Lambda 40 Perkin Elmer spectrophotometer with a BaS04 reflection sphere. HF was used as a reference. Data processing was carried out with Microcal Origin 7.1 software. 

That an asymmetric soil Cu profile and abundant fresh gold grains in C horizon soil samples most likely reflects mineralised bedrock entrained in till from a local source. 

Approximately 1400 samples were collected from predominantly farm wells and bores, although dewatering bores and groundwater monitoring bores were also sampled. Water was collected from the outflow pipe when the bore or well was operational, or bailed using a flow-though system with one-way valves. Additional samples were added to the assessment from previous work to enhance the study around key mineralised sites such as... 

This Gemini cationic surfactant could not be recovered from samples of biodegradation experiments performed in a lab-scale aerobic bioreactor [50] either because of complete biodegradation (mineralisation) or because of irreversible adsorption at the surface of the biodegradation device. 

In view of the inherent resistance of some surfactant metabolite isomers to complete mineralisation, efforts have to be mounted in order to obtain further insight into the reasons behind the persistence of these, such as the SPC and nonylphenol ethoxy carboxylates (NPECs). In order to achieve this, it would thus be indispensable to be able to fully elucidate the chemical structure of individual components, e.g. after isolation from environmental samples. Through the application of, for example, LC-ESI-MS-MS in combination with NMR analyses, this is now possible. 

Data from the Na-pyrophosphate partial extractions and estimates of organic C contained in humic and fulvic acids from spectroscopic determinations show poor reproducibility over time. Analysis of data from re-sampling in September 2007 show significantly lower results over bedrock mineralisation than the original orientation survey conducted in April 2007, although the general pattern appears to be preserved. Re-analysis of the duplicate field samples in the same batch indicates that this variation largely reflects seasonal variations in metal content of the soils, possibly related to rainfall patterns, but also includes a component of laboratory variation between batches. 

Soil samples were collected systematically down a 2 m deep colluvial soil profile located over Au mineralisation at the Bounty Gold Deposit (Yilgarn Craton, Western Australia), prior to mining. Bulk samples were analysed by ICP-AES, ICP-MS and XRD and further sub-sampled and analysed to ensure that they contained detectable Au prior to detailed analysis by LA-ICP-MS, SXRF and x-ray adsorption near edge spectrometry (XANES). 

Four surficial soils were collected from along a traverse across the projected position of the blind Northern Pods mineralisation (450 m below surface). This traverse was originally made to conduct a partial leach study over the Northern Pods, with samples 138538 and 138539 being soils with low mobile metal ion (MMI) response 250 m east of samples 138440 and 138441 which are directly over the mineralisation and show anomalous MMI response. 

Although Zn contents are highest in the fine fraction of the soils, the time needed to prepare such a soil fraction makes its use impractical. However, because fine generally makes up 35-50 % of the whole soil in the Endeavor, Hera and Wagga Tank areas, it may be able to be used directly. For example, Zn >150 ppm occurs in the highly anomalous samples above Northern Pods mineralisation relative to <40 ppm in a sample 250 m away. However, one would need to determine details of the soil size distribution in other areas being explored. 

All samples plot in the basalt to alkaline basalt fields of the Zr/Ti02 vs. NbA diagram of Pearce (1996) (Fig. 3). The NbA ratios define two distinct groups (1) tholeiitic metavolcanic rocks structurally underlying VMS mineralisation and (2) more alkaline ultramafic cumulates and metavolcanic rocks above VMS... 

Anomalous Cu concentrations in soil samples taken from the B horizon (60 cm to 90 cm) occurs between 40 m and 160 m from the mineralised outcrops with sample concentrations between 51 ppm and 98 ppm, and local maximum values up to 2,580 ppm along with barium and manganese anomalies. 

Mineralisation consists of the destruction of organic matter. Dry (oven) or humid (acid treatment) methods can be used for this purpose. Due to the absence of a universal method applicable to all mineral elements, it is necessary to adapt mineralisation to the sample being analysed. This stage, which is indispensable for the preparation of many types of samples, particularly those analysed by atomic absorption or emission, can be facilitated by the use of microwave digestion. 

The panned heavy mineral concentrates have not generally been analysed unless follow-up work has been carried out. However, all are inspected at site and observed minerals and contaminants are recorded. The samples are an excellent resource for identifying drainage catchment mineralisation and lithologies as well as anthropogenic contamination (Fig. 4.8). Indeed, all the G-BASE excess samples are stored at the National Geological Data Centre, Keyworth, UK, and are available for further study. The value of excess sample powders in research should not be underestimated. 

E. Vassileva, H. Docekalova, H. Baelen, S. Vanhentenrijk, M. Hoenios, Revisitation of mineralisation modes for arsenic and selenium determination in environmental samples, Talanta, 54 (2001), 187-196. 

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