1. Introduction.

Air quality is an important part of safe work conditions and human health. Technological processes that include work with chemicals of different danger classes cannot proceed without air quality monitoring for employees. Potential threats to human health should be defined and concentrations of hazardous chemicals need to be evaluated for implementation of safety measures and improvement of working conditions. Various technological processes are operated with utilization of organic materials and different types of oil products. Evaluation of work safety at the production sites where there is a large variety of organic, non-organic and complex materials can be very challenging due to limited capability of several determination and measurement methods. Selectivity is a key problem in analysis of samples with a complex chemical composition. Evaluation of work conditions safety can require a lot of resources when several construction materials are present in the air along with paint and its dissolvent. Vapors of numerous organic chemicals should be detected in the air and their concentration should be measured for proper environmental and safety management actions. In some cases requirements designation for chemical analysis can be possible only after the detailed research of potential hazardous components in specific conditions [8, 15].

Monitoring of workers’ exposure to hazardous chemicals is essential for determination of safety measures at facilities where oil products are implemented. Measurements of airborne concentrations require workspace air sampling that is compatible with analysis methods. Authorities, national or international standards, usually define criteria for exposure limits and controlled parameters. However, in specific cases results of the environmental and safety monitoring can be compromised by interconnections and side influences of different chemical components. For example, chemical compound of oil products in most cases is based on similar hydrocarbons such as naphthenes, paraffins and aromatics. Due to the fact, that for some studied substances (such as oil product contaminants in the air) it is impossible so far to develop a reference material, calibration of laboratory equipment is performed with application of indicator chemical.  [4; 6; 11].

2. Materials and methods.

Determination of concentration in the air for gasoline (petrol), solvent naphtha (petroleum) and Stoddard solvent (white spirit) can be performed by the implementation of gas chromatography method that is described in the Federal Environmental Regulatory document 13.1.8-97 “Method for chromatographic measurement of the concentration of gasoline, white spirit and solvent in industrial emissions using a universal disposable sampler”. This method is based on implementation of gas chromatography with flame-ionization detection, as a modern approach for determination of organic materials with high sensitivity. Even though the method is developed and certified for analysis of industrial emissions, it is common for laboratories to validate Federal Environmental Regulatory document 13.1.8-97 also for a workspace air. [3; 12].

According to the method 13.1.8-97, concentrations of gasoline, white spirit and solvent can be measured in the range from 1,0 mg/m³ to 15000 mg/m³. Precision of this method is 25% at the confidence interval of 95%. For measurements performance gas chromatography system with a flame-ionization detector and packed metal column is calibrated with application of hexane solutions. Hexane is introduced as a reference material and N,N-dimethylformamide is required as a solvent. Air samples are aspirated through the carbon samplers in accordance to the potential level of chemical exposures. Volume of air sample is defined by expected concentration of measured components. If expected concentration in the area is low and belongs to the range from 1 mg/m³ to 10 mg/m³, then the sample volume should be equal to 20 dm³. In case of high expected concentration (more than 5000 mg/m³), volume of the sample is minimal for this specific method and is equal to 0,1 dm³. In the laboratory studied components are extracted from samplers during the process of storing carbon fibers in N,N-dimethylformamide for 30 minutes. Then N,N-dimethylformamide with diluted chemical components is analyzed in a gas chromatography system. At this stage of analysis there is a high chance to receive conflicting results if there are several materials present at the studied area [3].

Combination of hazardous sources such as gasoline and white spirit will provide uncertain results of the analysis by the 13.1.8-97 method. Due to the fact, that calibration of a gas chromatography system is based on the hexane concentration, it will be impossible to distinguish concentrations of studied materials. In this case, average results cannot be used for determination of safety measures [2]. According to the Hygienic standards 2.2.5.1313-03, maximum permissible concentration (MPC) values for gasoline (petrol) and solvent naphtha (petroleum) are the same: MPC for a one-time exposure – 300 mg/m³, MPC for an average concentration in the air of the working area during the day – 100 mg/m³. For a concentration of white spirit, results should be converted to carbon before the evaluation. MPC for a one-time exposure for white spirit is equal to 900 mg/m³, and the MPC for an average concentration in the air of the working area during the day (conversion to carbon) is equal to 300 mg/m³. On another hand, if on the same facility concentrations for gasoline and solvent naphtha were to be defined for safety assessment, it would be possible to perform evaluation with the total concentration value. Gasoline and solvent naphtha have equal values for maximum permissible concentrations and similar evaluation of hazards [1; 2; 5; 13].

3. Results and Discussion

This example represents the problem of selectivity in determination of safety measures for facilities where complex materials with potential chemical hazards are implemented. Alternative methods with implementation of capillary columns or different analysis conditions can provide visible difference in results for each substance, but could also lead to uncertainties in calculations if the chromatogram profile determines the presence of various peaks. Results of the analysis can be accepted on the legal level only if methods are certified and approved by authorities. Therefore, current amount of available methods is limited. Selection of a suitable standard for evaluation of hazardous material concentration in a workplace air is a challenging process. For example, implementation of detector tubes is a more simple and cheap method than gas chromatography, but margin of error is significantly larger and selectivity problem is even more acute for areas with complex workplace air composition. [7; 9; 10]

Another analysis aspect that is important to consider is structural differences of hydrocarbons that can be present in workspace air during the performance of technological procedures with oil products. For example, benzene and dichloromethane are potential hazardous chemicals in an area of paint production or application. Different types of paints contain benzene and dichloromethane can be present in a solvent composition. Due to the fact, that benzene is a non-polar chemical and dichloromethane is polar, estimation of exposure level of a painter requires at least two different methods or a sophisticated gas chromatography system with two types of chromatographic columns [14].

Complex composition of materials leads to a challenge in designation of safety measures and requirements. Even with development of material safety data sheets evaluation of exposure level of employees at a production site can be very specific and require a research on a potential chemical compound of workspace air with sophisticated analytical methods such as gas chromatography-mass spectrometry, IR Fourier spectroscopy and nuclear magnetic resonance spectroscopy. Even though these modern methods can provide the best possible results in some cases, it is not practical to implement them for major part of environmental and safety monitoring due to high costs. Standardized measurements require optimal analysis methods in order to be available at different level of production facilities. Extreme prices may lead to neglect of proper working environment monitoring [11].

The problem of selectivity should be systematically revised for common analysis methods in the field of environmental and safety monitoring. Determination of hazardous components in the air at the workplace area is essential for prevention of emergencies and long-lasting health risks for human health. Selectivity problem of analysis methods may cover potential threats and cause bias in the research of work safety management. Development of technologies and analytical methods should motivate employers and authorities to consider periodical actualization of implemented methods and monitoring programs. Addition of standards for reference materials and research of possible interfering factors can significantly enhance reliability of monitoring measures.