High standard additions procedure

This analytical method, based on TXRF, enables a large number of trace elements to be determined simultaneously. The range is suitable for different areas of the sea. The motivation to use TXRF resulted mainly from the characteristic features of the method its high detection power, its universal calibration curve, which eliminates the need for matrix-dependent standard samples or standard-addition procedures, the simple preparation of the sample films, and of course the possibility of multielement determination. 

Chemical interferences, which can be highly dependent on matrix type and the specific analyte element, are characterized by molecular compound formation, ionization effects, and solute vaporization effects. If such effects are observed, they can be minimized by careful selection of operating conditions, by buffering the sample, by matrix matching, and by standard addition procedures. 

Whereas carbonyl chloride itself is very moisture sensitive and requires the corresponding precautions such as efficiently dried glassware and solvents, the Box derivative is very stable and can be analysed by high performance liquid chromatography (HPLC) with ultra violet (UV) detection at 270 nm. Quantification is achieved by the standard addition procedure spiking carbonyl chloride into the test polymer solution. However, since Box is a commercially available chemical, it is advisable to work also with Box standards, especially when the method is used for the first time and when problems are experienced in the HPLC determination or the derivation procedure. The standards of the carbonyl chloride derivative are particularly useful to establish the analytical system and to check linearity of detector response as well as for the recovery check. 

In the case of e.g. voltammetric techniques, the high content of organic matter could lead to erroneous (too high) results even in case standard addition procedures are applied. 

Lower results (factor 2) were observed for ICP in comparison to ETAAS. It was assumed that interferences were taken into account in the calibration in the ICP measurement. However, when standard additions were used or Ca was added to the calibrants, ICP results agreed with those of ETAAS, which demonstrated the need to perform a matrix matching calibration or a standard addition procedure. The scatter of results observed in step 2 (0.73 to 1.66 mg kg ) was found to be high but not surprising considering the low Cr content in the extract. 

Matrix effects were evaluated by Gago-Ferrero et al. [23]. Both signal suppression and signal enhancement were observed. The extent of these effects was found to be fairly dependent on the UV filter. Thus, quantification should be performed by standard addition or internal standard calibration. Since standard addition is a high time-consuming procedure, internal standard calibration with appropriate isotopi-cally labeled compounds is the best option. 

Arsine is highly volatile and there is little risk of direct residual contamination. However, potential persistent decomposition products include arsenic and arsenic oxides. Wash the remains with soap and water. Pay particular attention to areas where agent may get trapped, such as hair, scalp, pubic areas, fingernails, folds of skin, and wounds. If remains are heavily contaminated with residue, then wash and rinse waste should be contained for proper disposal. Once the remains have been thoroughly decontaminated, no further protective action is necessary. Body fluids removed during the embalming process do not pose any additional risks and should be contained and handled according to established procedures. Use standard burial procedures. 

Often the chemical speciation of iron, and hence its availability, is significant in iron supplements. Thus atomic absorption may be preceded by separation procedures [96]. To measure total iron in multi-vitamin preparations the sample can be taken up in hydrochloric acid and the determination made in an air/acetylene flame. Care must be taken with high mineral content samples to avoid inter-element interferences and the method of standard additions may be employed. Similar comments may be made about the determination of manganese and copper [97, 98], except that interferences are here less likely, but there may be a requirement for lower levels to be determined. 

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