Petrochemical and Organic-Based Samples

In the production of petrochemicals and related products, it is critical for refineries and chemical plants to closely monitor trace element contamination levels at various stages of the manufacturing process. For example, in the refining of crude oil, some elements such as Ni and V, even at ppb levels, can act as catalyst poisons and cause enormous problems owing to the volumes of hydrocarbons that are processed. In addition, if the final product is intended for use by the food industry or the manufacture of electronic devices, the specifications for trace element contamination are even more stringent. 

The problem is that the analysis of petrochemical samples can be extremely difficult because of the complex nature of crude oils, distUlates, residues, fuel oils, petroleum products, organic solvents, and all the varions by-products from refining crude oil. These complex oil-based samples pose major problems for any analytical technique, owing to the difficulty of introducing them directly into the instrument. So, the analytical challenge for any trace element technique being used in the 

Practical Guide to ICP-MS A Tutorial for Beginners, Second Edition 

Comparison Data for the Determination of Ni and V in NIST 1618-Certified Reference Fuel Oil by ICP-OES, Using the Sulfated Ash Method and ICP-MS, Using a Simple 1 1000 Dilution in Toluene 

NIST 1618 CRM Total Sample Preparation/ Analysis Time Sample Weight (g) Ni (ppm) RSD (%) V (ppm) RSD (%) 

Avoiding these kinds of problans was among the reasons why the petrochemical conununity became interested in ICP-MS. Previously, ICP-OES was one of the preferred techniques for the multielanent analysis of oil-based samples. However, because of the achievable detection limits of ICP-OES, a sample preparation technique known as the sulfated ash method (SASH) usually had to be used. This approach, which involved oxidation of the oil sample with concentrated sulfuric acid and high-temperature ashing, took approximately 3 days to ensure all the analytes were in solution. When the use of ICP-MS was investigated, they found that because of its extremely high sensitivity, a simple dilution of the sample with a solvent such as toluene could be used. In other words, the lengthy sulfated ash method used to 

However, even if all these precautions are taken, some analytes are still problematic because the carbon-based polyatomic spectral interferences can never be totally eliminated. In addition, the small amount of oxygen in the nebulizer gas flow will add to the spectral complexity of the background by generating oxide-based interferences. Some of the elements that suffer from these types of spectral interferences in an organic matrix are shown in Table 19.14. 

For this reason, collision/reaction cell/interface technology is almost a necessity when analyzing petrochemical- or oil-based samples, especially if the analytes are at extremely low levels. To emphasize this, Abu-Shakra showed the benefits of using collision/reaction cell technology together with an optimized sample introduction 

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