Methods that measure PM 2.5 mass, total particulate NO 3 -, and elemental carbon (EC) were evaluated in seven U.S. cities from 1997 to 1999. Sampling was performed in Bakersfield, CA; Boston, MA; Chicago, IL; Dallas, TX; Philadelphia, PA; Phoenix, AZ; and Riverside, CA. Evaluating and validating methods that measure the components of fine mass are important to the effort of establishing a speciation-monitoring network. The Harvard Impactor (HI), which measures fine particle mass, showed excellent agreement (r 2 = 0.99) with the PM 2.5 Federal Reference Method (FRM) for 81 24-hr samples in Riverside and Bakersfield. The HI also showed good precision (4.8%) for 243 24-hr collocated samples over eight studies.The Aethalometer was employed in six of the sampling locations to measure black carbon (BC). These values were compared to EC as measured from a quartz filter using thermal analysis. For the six cities combined, the two methods were highly correlated (r 2 = 0.94; 187 24-hr samples); however, the BC values were approximately 24% less than the EC measurements consistently across all six cites. This compares well to results observed for EC/BC IMPLICATIONS The evaluation of existing methods that measure specific characteristics of fine PM is imperative to the successful implementation of the speciation-monitoring network. PM 2.5 FRM sampling artifacts occur due to the volatilization of NH 4 NO 3 (negative artifact) or the adsorption of HNO 3 to particles already collected on filter (positive artifact). Nitrate losses are most significant in areas with high NO 3 -levels and warmer temperatures. The HI is a suitable, cost-effective alternative to the FRM for measuring particle concentrations and is an excellent candidate to be evaluated for a Class II equivalent method. After correcting the manufacturer's conversion factor, the Aethalometer agrees well with the traditional, thermally measured EC in a typical semi-urban site. Obvious advantages to using continuous monitoring techniques, such as the Aethalometer, include improved time resolution and cost-effectiveness. measurements observed in other semi-urban areas. Particulate NO 3 -was measured using the Harvard-EPA Annular Denuder System (HEADS). This was compared to the NO 3 -measured from the HI Teflon (DuPont) filter to assess NO 3 -artifacts. Significant NO 3 -losses (approximately 50% of total NO 3 -) were found in Riverside, Philadelphia, and Boston, while minimal artifacts were observed in the other sites. Two types of HEADS configurations were employed in five cities. One system used a Na 2 CO 3 -coated glass fiber filter, and the other type used a nylon filter to collect volatilized NO 3 -from the Teflon filter. The HEADS with the Na 2 CO 3 -coated filter consistently underestimated the total particulate NO 3-by approximately 20% compared to the nylon HEADS.

2.5The principle of this method is based on the measurement of the increase in ( TM ) pressure drop across a membrane lter Fluoropore during particle sampling.The monitor consists of a conventional impactor r r r r r inlet to remove particles larger than 2.5 m m, a diffusion dryer to remove particle-bound water, a lter tape to collect particles, a lter tape transportation system to allow unassisted sampling, ( and a data acquisition and control unit. For each sampling period typically 30-) 60 min , a new segment of the lter tape is exposed so that particles remain close to equilibrium with the sample air during their collection. This results in minimization of volatilization and adsorption artifacts during sampling. Furthermore, since the required ow rate for the ne particle mass monitoring channel is only 0.3 L r r r r r min, the relative humidity of the air sample can be easily reduced to 40%or less using a Na on TM diffusion dryer to remove particle-bound water. The CAMM has a detection limit of -5 m g r r r r r m 3 for PM concentrations averaged over 1 h. 2.5The performance of the newly developed monitor was investigated through laboratory and eld studies. Laboratory tests included a calibration of the CAMM ( ) using polystyrene latex PSL and silica particles. A series of eld studies were conducted in 7 cities with presumably different PM chemical composition. The 2.5 24 1-h CAMM measurements were averaged and compared to Harvard Impactor ( ) HI 24 h PM integrated measurements. Based on 211 valid sampling days, the 2.5 measurements obtained from the Harvard Impactor and the CAMM were highly ( 2 ) correlated r s 0.90 . The average CAMM-to-HI concentration ratio was 1.07 ( ) " 0.18 .

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Topicality. The use of selenium-protein dietary supplements (SPDS) is relevant from a medical and economic point of view, as it can provide consumers with the required amount of selenium, and increase the value and attractiveness of food products. The diet of a modern person is very diverse in the composition of fatty ingredients. Of all natural fats, dairy is the most complex and unique one in its chemical composition. SPDS “Syvoselen Plus” contains up to 10% fat in its composition, therefore, studies of its composition are of certain scientific interest in view of the above. In many scientific studies, gas chromatography is used to determine the composition of not only the fat fraction of additives containing vegetable oils and animal fats, but also organic acids. The study of the fat fraction and the fraction of organic acids of additives by this method allows determining and predicting the composition of similar fractions in the final product from SPDS. This, in turn, allows for comprehensive control of the quality and composition of such final products. The aim of the article is to determine the quantitative and qualitative composition of fatty and organic acids in the SPDS “Syvoselen Plus” by the gas chromatography method, and to compare the results of the determination with the indicators of a hypothetical ideal fat. When writing the article, statistical and physico-chemical research methods were used, namely, the gas chromatography method, with the help of which the following problems are solved: the composition of the fat fraction of SPDS is determined quantitatively and qualitatively; the degree of correspondence of the main indicators of the fat “Syvoselen Plus” to the hypothetical ideal is established; the composition of organic acids in the additive is determined. Results. The fatty acid composition of milk fat, milk whey and SPDS was studied. Dietary supplement “Syvoselen Plus” contains a significant amount of palmitic (3117.71 mg/kg), stearic (1618.61 mg/kg), oleic (1397.95 mg/kg) and meristic (1296.69) mg/kg) fatty acids, which is confirmed by chromatograms of fat fractions of milk fat and SPDS. The main indicators of hypothetically ideal, milk, whey fats and DDBS were presented. As a result, it was established that the composition of fat, which is most similar to the ideal one, among the objects of the study, has SPDS “Syvoselen Plus” (the indicator of the ratio of the sum of oleic and linoleic acids to the sum of pentadecanoic and stearic acids coincides with the indicator of ideal fat, and the indicators of the ratio of linoleic to linolenic acids and linoleic to oleic acids are close to the values of the indicators of ideal fat). The study of the composition of organic acids of SPDS was carried out. Fractions of succinic, azelaic, and levulinic organic acids are predominant, which may be due to the type of dairy products from which the serum was obtained, the storage conditions of dairy products and the serum itself, the type of microorganisms that carry out the fermentation process and can produce various organic acids, and the production process of dairy products and their composition. Conclusions and discussion. The analysis of the fatty acid composition and the quality content of organic acids in “Syvoselen Plus” dietary supplement confirmed the feasibility of using a dietary supplement in health food technologies, since the latter contains enough polyfunctional fatty and organic acids.