Analysis of solid samples

A stock of sub-boiled and blank-controlled acids is prepared and a dilution of a metal standard solution e.g., 100mg/L of gallium). Several separation procedures are performed to clean the Teflon bombs (refer to next section), until the blank values are constant and low. 

Filters are weighed to a precision of at least 0.1 mg. If any electrostatical charge of the filters occurs it must be neutralized (see Section 12.4.2.4-Apparatus.). 

Digestion of suspended particulate matter (see also Section 12.6) 

Amounts of 20 to 100 mg of a dried sediment sample are transferred into the Teflon bomb and the procedure given for samples of suspended material should be followed. 

A 20 pL aliquot of silicon oil (e.g., Serva, Heidelberg, Germany) is placed onto a cleaned sample carrier and allowed to dry, in order to prepare a hydrophobic surface on the quartz carrier to prevent bleeding of the water (acid) drop. Approximately 10 pL of the sample solution are deposited at the centre of the carrier (the volume depends on the type of sediment, its decomposed mass and the dilution after digestion) and dried on a heater adjusted to 100 °C. The special device should be used for positioning the spot correctly in the central area (8 mm diameter) of the carrier. 

Vdllkopf Z. Grobenski, R. Tamm, and B. Welz, Analyst (London), 1985, 110, 

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As already remarked in Sect. 4.5.1 (Introduction), LA was primarily designed as a technique for direct sampling in the bulk analysis of solid samples. The main advantages of LA are the possibility of ablating all types of solid material (metals, isolators, glasses, crystals, minerals ceramics, etc.), no special requirements on the... 

Nowka R, Muller H (1997) Direct analysis of solid samples by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer and D2-background correction system (SS GF-AAS). Fresenius J Anal Chem 359 132-137. 

Hoffmann E, Ludke C, Scholze H (1997) Is laser ablation-lCP-MS an alternative to solution analysis of solid samples Fresenius J Anal Chem 359 394-398. 

Noweoy R, Marr IL, Ansari TM, Muller H 1999) Direct analysis of solid samples by GFAAS -determination of trace hea-vy metals in barytes. Fresenius ( Anal Chem 364 533-540. 

Verrept P, Dams R, Kurfurst U 1993) Electrothermal vaporisation inductively coupled plasma atomic emission spectrometry for the analysis of solid samples contribution to instrumentation and methodology. Fresenius 2 Anal Chem 345 1035-1041. 

This relatively new method is quite different from other mass spectrometric techniques usually used for this topic. ToF-SIMS presents two main advantages. First, it permits the analysis of solid samples with minimal sample preparation. This avoids the necessity of extractions, and therefore, it can be very useful for small and precious samples. 

For analysis of solid samples, GC-MS/MS [45] and more frequently HPLC-MS have been used [46,63]. Limits of detection vary from 0.04 to 4 ng g. ... 

The matrix is the major component of the solution (or of the solid if using laser ablation or SEM). Matrix differences between standards and samples or between samples may result in differences of elemental sensitivity. Therefore, it is desirable that all the blanks, calibration standards, and samples have the same matrix (i.e., are matrix matched). This is relatively easy to achieve in solution, but can be a major problem with the analysis of solid samples. 

In the analysis of solid samples (e.g., LA-ICP-MS, SEM), synthetic standards cannot easily be prepared to the required concentrations, and accurate calibration of such techniques is often challenging. In some cases (e.g., SEM) pure element or single mineral standards are used, ideally with an appropriate standard for each element to be quantified. (It is possible in SEM, within limits, to use fewer standards than the number of elements to be determined, with the calibration for other elements being predicted from the response of the nearest element.) More often, however, multielement primary standards are used as the means of calibrating the instrument, e.g., for LA-ICP-MS of glasses, volcanics, and ceramics, two glass standards, NIST 610 and 612 (Pearce et al. 1996), are often used. It is always advisable to use more than one multielement standard in order to cover as wide a range of concentrations as possible, and to use at least one additional independent reference material as an unknown, for quality assurance purposes (see below). 

Elemental analysis of sample digests Non-destructive analysis of solid samples... 

The Dohrmann DX 20B system is based on combustion of the sample to produce the hydrogen halide, which is then swept into a microcoulometric cell and estimated. It is applicable at total halide concentrations up to lOOOpl-10 with a precision of 2% at the lOpg L-1 level. The detection limit is about 0.5pg L-1. Analysis can be performed in 5 min. A sample boat is available for carrying out analysis of solid samples. The instrument has been applied to waste waters, soils and sediments. 

Direct analysis of solid samples or analytes present on solid surfaces without any sample preparation has always been a topic of interest. Desorption electrospray ionization (DESI) is an atmospheric pressure desorption ionization method introduced by Cooks et al., producing ions directly from the surface to be analyzed, which are then sampled with the mass spectrometer [22, 37]. DESI is based on charged liquid droplets that are directed by a high velocity gas jet (in the order of 300 m s ) to the surface to be analyzed. Analytes are desorbed from the surface and analyzed by mass spectrometer (Eig. 1.15). 

Physical analysis of solid samples is incorporated into Level 1 because the size and shape of the particles have a major effect on their behavior in process streams, control equipment, atmospheric dispersion, and the respiratory system. In addition, some materials have characteristic physical forms which can aid in their identification. 

The application of atomic spectroscopic instruments as element-specific detectors in chromatography has been reviewed by van Loon More recently, Krull has extensively reviewed their use in high pressure liquid chromatography (HPLC). Atomic spectrometry has found wide acceptance in the field of liquid chromatography because, in most cases, the fractions can be directly analysed after elution from the column. However, it is possible to use the technique for the analysis of solid samples without first dissolving the matrix. This is particularly useful after electrophoresis, where the fractions are fixed either in a gel or on paper. Kamel et al. have shown that it is possible to cut the appropriate sections and insert them into the carbon furnace for analysis. The disadvantage of this approach is that the precision is usually poorer (about 10%) and it is difficult to calibrate the instrument. Nevertheless, this approach is very useful if it is used for qualitative speciation. 

The introduction of inductively coupled plasma (ICP) in inorganic mass spectrometry means that there is an effective ion source operating at atmospheric pressure. Whereas solid mass spectrometric techniques allow direct analysis of solid samples in ICP-MS, the determination of trace impurities or isotope ratios in solid samples is often carried out after digestion and dissolution of the material. For the determination of trace impurities and isotope ratios in liquids, an additional nebulization... 

LA-ICP mass spectrometry is becoming the method of the choice for trace and isotope analysis of solid samples and is already the most important laser induced technique in inorganic mass spectrometry due to the advantage of direct solid sampling by focused laser irradiation on the sample surface and its ability to provide microscale information. 

For measurements of isotope ratios or isotope abundances, any of the mass spectrometers discussed in the previous chapters, such as SSMS, LIMS, GDMS56 and LA-ICP-MS,6 are of benefit for the direct isotope analysis of solid samples. SSMS and LIMS are rarely applied in isotope analysis due to their relatively low precision. Several applications of the isotope dilution technique as a calibration strategy in SSMS, mostly on geological samples, are known.57-59 GDMS has been mostly applied in multi-element trace analysis and depth profiling and plays only a minor role... 

To an increasing extent, LA-ICP-MS is the method of choice for the direct analysis of solid samples with respect to the analysis of long-lived radionuclides. Most applications of LA-ICP-MS... 

Advantages brought about by the direct analysis of solid samples as compared with the analysis of dissolved samples include a shorter total analysis time (prior dissolution steps are not required), low cost (chemical reagents are not used), less risk of contamination and less destruction of the sample. In addition, some techniques can extract information about chemical speciation e.g. XPS provides information about oxidation states and chemical bonds) and spatial composition, i.e. information with lateral resolution allowing mapping of the surface and analysis with depth resolution, of particular interest for thin-film analysis. 

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