Indium internal standard

Vandecasteele et al. [745] studied signal suppression in ICP-MS of beryllium, aluminium, zinc, rubidium, indium, and lead in multielement solutions, and in the presence of increasing amounts of sodium chloride (up to 9 g/1). The suppression effects were the same for all of the analyte elements under consideration, and it was therefore possible to use one particular element, 115indium, as an internal standard to correct for the suppressive matrix effect, which significantly improved experimental precision. To study the causes of matrix effect, 0.154 M solutions of ammonium chloride, sodium chloride, and caesium chloride were compared. Ammonium chloride exhibited the least suppressive effect, and caesium chloride the most. The results had implications for trace element determinations in seawater (35 g sodium chloride per litre). 

Choice of an Internal Standard. One of the difficulties in the spec-trometric trace analysis of coal ash samples, in addition to choosing a suitable comparison standard matrix, is choosing an internal standard. The first choice in both analytical methods was indium, which was used as a constant internal standard added to the graphite powder diluent-buffer. The results obtained had poor reproducibility, as previously... 

Electrode Preparation. Electrodes were prepared by mixing the samples with equal parts of pure graphite. To insure homogenous mixing and to determine the plate sensitivity, 50 ppm indium was added as an internal standard to the sample-graphite mixture. (In this paper, ppm are given in terms of weight.) The mixtures were pressed into... 

ICP-MS, even when using a internal standard (Indium), a bias of 8% was observed. 

Zeolite samples were digested using a mixture of HF, HNO3 and HCIO4 in screw-top teflon bombs (Savillex). Ruthenium analyses were performed using a VG PlasmaQuad II Inductively Coupled Plasma Mass Spectrometer. All samples were spiked with indium to serve as an internal standard. Atomic absorption was used to determine aluminum content. The results from the chemical analyses are shown in Table 1. 

A free flowing monomer, ethylene glycol dimethacrylate (EGD) stabilised with 0.1% hydroquinone is thickened with 0.0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0 and 16.0% of methyacrylate butadiene styrene (MBS). Two further samples of the same monomer are thickened with similar increasing concentrations of cellulose nitrate (CN) and silicone dioxide (SiCh) for comparison. An accurate weight of 10.0 g of each thickened monomer is dissolved in 25% n-propanol and 75% glacial acetic acid. Then 0.25 ml of 1000 ppm Zn metal stock standard solution is added to each mixture. These solutions are also spiked with 0.5 ml of 1000 ppm indium (In) metal as internal standard. All mixtures are diluted to mark with the 25% n-propanol/glacial acetic acid. The mixtures contain 2.5 ppm Zn and 5.0ppm In per ml. 

Today, ICP-MS permits very low detection limits (0.1 jgkg ) of tin in biological matrices. Sample preparation consists of reconstitution of the freeze-dried material or in microwave digestion, both followed by dilution in a solution of an internal standard (europium, indium, scandium, etc.) The main characteristic isotopes used for the determination of tin are Sn, Sn, Sn, and Sn. 

A membrane filter which can be dissolved in acetone, or a spectrochemically pure graphite filter which can be examined directly with a powder DC-arc technique, can provide passable results. After air has been drawn through a previously weighed filter, the membrane filter is dissolved in acetone, then centrifuged. The particulates are collected, dried, and weighed then a spectroscopic buffer is added composed of 1 part NaF and 1 part graphite powder, with 100 ppm indium oxide and 20,000 ppm tantalum oxide as internal standards. About 35 mg of the final mixture is placed in a graphite electrode and arced at 15 A for 60 sec in a controlled (90% At-10% O2) atmosphere. 

Alternatively, the graphite filter can be a standard porous-cup spectrographic electrode (Fig. 11.4) through which air is drawn. An indium internal-reference solu-... 

A 2.5-mm hole is drilled through the base of the electrode after sample collection and a technique utilizing argon saturated with HCl gas vaporizes the sample and carries it into a dc arc operating at 28 A. Indium is used as an internal standard. Fourteen elements are determined quantitatively in the particulate matter, including Al, Be, Cr, Co, Hg, Mg, Mn, Mo, Ni, Pb, Ti, V, W, and Zn. 

For determination, external standard method or internal standard method is used. In ICP-MS, an internal standard method is applied [9]. For internal standards, Thallium and Indium are generally utilized for heavy metals. In Table 3, element solutions are listed as internal standard solutions. The objective element is sandwiched by two internal standards as shown in Table 3. Usually, these solutions are purchased as reagents. After ascertaining that these elements are very low in an original sample solution, these internal standard solutions are put into a sample solution concentration of an internal standard should be almost 100 times higher than that of elements in the sample solution. 

Assignments of intensities and calculation of concentrations can be performed by general element survey and specified software. Precision (RSD) below 5% is commonly achieved for elements present at 25pgl . To correct for matrix-induced ion signal variation and instrumental drift, rhodium or indium in combination with panoramic analysis, based on full mass-spectra scan methods, is used as the internal standard (IS). Spectroscopic effects due to Cl, Na, Ca, Mg, S, and C were corrected with interference factors (IF) on the basis of a set of correction equations (see Table 5). 

The most witlely used quantitative method of ICPMS uses a set of calibration standards for preparing a calibration curve. Simple aqueous standards are usually adequate if the unknown solutions are sufticiently dilute — less than 2000 pg/mL of total dissolved solids. With higher concentrations of matrix elements, attempts are often made to match the matrix elements in the samples with those in the standards. To compen-.sate for instrument drift, instabilities, and matrix effects, an internal standard is usually introduced into the standards and the unknowns. The internal standard is an clement that is absent from the samples and that has an atomic mass and ionization potential near those of the analytes. Two elements frequently used for internal standards are indium and rhodium. Both produce ions in the central part of the mass range ( In, "In, and " Rh) and are not often found naturally occurring in samples. Generally, log-log plots of ion current, ion count, or intensity ratios for sample and internal standards are linear over several orders of magnitude of... 

Indium is often used as an internal standard element for semiquantitative analysis, because it is usually present at low concentration (or totally absent) in most types of samples it can be obtained at modest cost in a highly purified form it has two isotopes available for measurement at significantly different abundances (4.3% for m/z 113 and 95.7% for m/z 115) that are relatively interference free in most sample matrices and these isotopes fall in the middle of the mass spectrum, so they can be used for both low and high mass analyte elements. Typical semiquantitative analyses, using both calibration methods, are illustrated in Table 7.1. Other elements can also be used for internal standards. Internal standardization is described in more detail in the following section. 

International Committee For Standardization In Hematology (1988) Panel on diagnostic applications of radionuclides. Recommended method for indium-111 platelet survival studies. J Nucl... 

Cast alloys must be made from at least 99.99% purity zinc ingot to comply with the standards of the American Society for Testing and Materials (ASTM B6) and the International Organization for Standardization (ISO 752) a standard is in preparation by the Comit Europeen de Normalisation (CEN European Committee for Standardization). The harmful impurities, which occur naturally in zinc or as contaminants in the other alloying ingredients, are lead, tin, cadmium, indium, and thallium. These impurities are limited by specification higher contents than specified may make the alloys susceptible to intergranular corrosion, particularly when exposed to warm, moist environments. 

With optically transparent electrodes (OTE), molecular adsorbates, polymer films, or other modifying layers attached to the electrode surface or being present in the phase adjacent to the electrode can be studied. With opaque electrode materials, internal or external reflection may be applied. Glass, quartz, or plastic substrates coated with a thin layer of semiconductors (indium-doped tin oxide) or conducting metals (gold, platinum) are often used as OTE. The optically transparent electrode is immersed as working electrode in a standard cuvette. 

---