Particulate analysis, analytical methods

With analytical methods such as x-ray fluorescence (XRF), proton-induced x-ray emission (PIXE), and instrumental neutron activation analysis (INAA), many metals can be simultaneously analyzed without destroying the sample matrix. Of these, XRF and PEXE have good sensitivity and are frequently used to analyze nickel in environmental samples containing low levels of nickel such as rain, snow, and air (Hansson et al. 1988 Landsberger et al. 1983 Schroeder et al. 1987 Wiersema et al. 1984). The Texas Air Control Board, which uses XRF in its network of air monitors, reported a mean minimum detectable value of 6 ng nickel/m (Wiersema et al. 1984). A detection limit of 30 ng/L was obtained using PIXE with a nonselective preconcentration step (Hansson et al. 1988). In these techniques, the sample (e.g., air particulates collected on a filter) is irradiated with a source of x-ray photons or protons. The excited atoms emit their own characteristic energy spectrum, which is detected with an x-ray detector and multichannel analyzer. INAA and neutron activation analysis (NAA) with prior nickel separation and concentration have poor sensitivity and are rarely used (Schroeder et al. 1987 Stoeppler 1984). 

Analytical Methods. Many chemical and physical analysis methods exist to characterize particulate matter collected on a substrate. Though several methods are multi-species, able to quantify a number of chemical components simultaneously, no single method is sufficient to both quantify the maiorlty of the collected particulate matter mass and those components which serve to Identify and quantify source contributions. 

The aerosol samples collected by the SFU were analyzed both gravimetrlcally for total suspended particulate mass less than 15pm, and by particle induced x-ray emission (PIXE) for elemental content. The filters were weighed before and after sampling using a Cahn 25 electrobalance sensitive to Ipg. Typical precision of TSP determined by this analytical method is 0.5pg/m for samples collected under conditions of low aerosol concentrations ( ). After weighing, the filters were analyzed for elemental content (elements heavier than Na) using the UC Davis PIXE system. This analysis technique is described in Cahill al ( ). 

Table I summarizes the sampling media used in the last three years of the study. Previously, we have developed validated sampling and analytical methods for many of the common organic solvents that could be collected on charcoal, desorbed with carbon disulfide, and analyzed by gas chromatography. These procedures are usually nearly identical with the NIOSH method P CAM 127. Likewise, methods for substances that give well-behaved particulates both in collection and analysis had been validated. The substances summarized in Table I represent a wide variety of problems in sampling and analysis. Consequently, many of the samplers were charged with unusual collection media.

Macroscopic methods for chemical analysis essentially take either all of the particulate matter sampled or a significant protion of it for bulk analysis. Traditionally, this has been approached by the application of standard microchemical techniques of wet chemistry. The unique analytical requirement for aerosol particle samples is the microgram quantities collected. The analytical methods adopted must be capable of detecting these quantities in... 

Table I lists several XRD analytical methods recently developed in the NIOSH laboratories. For each analyte, the analytical range, detection limit and analytical precision are listed. The method numbers refer to the NIOSH Manual of Analytical Methods (2.). As indicated in the table, there are several NIOSH methods available for free silica analysis. Method No, P CAM 109 incorporates the internal standard approach as developed by Bumsted (3.), The other two methods S-315 and P CAM 259 are based on the substrate standard method. The major difference between the two is the direct sampling on silver membrane filters (S-315). This paper will address the various methods of quantitation, sample collection and procedures for matrix absorption corrections that have been used in this laboratory for the analysis of crystalline particulate contaminants in the workplace.

Tungsten. Both water-soluble and insoluble compounds are determined. Particulate tungsten on a filter is first extracted with water. One ml of 20% w/v sodium sulfate is added to the extract which is then dilute for analysis by rich nitrous oxide-acetylene flame at 255.1 nm. The filter is treated with 1 1 HC1 to remove iron and cobalt interferences before being nitric acid wet ashed and nitric/hydrofluoric acid wet ashed. The residue is heated with 0.5 N NaOH and treated as soluble tungsten. Tungsten carbide is determined at less than 100% recovery when cobalt is present. The detailed method for tungsten developed by Hull and Eller is in Volume Four of the NIOSH Manual of Analytical Methods to be published in Winter 1978. 

To evaluate the influence of given metals in oil products it is fortunate that analytical methods are available that are sensitive, accurate and informative. Analytical methods associated with oils involve step-by-step procedures from sample preparation to suitable solutions for measurements against certified standard calibration curves. The sample preparation step is very important in the analysis, and the method used is decided by the concentration of metal present and whether or not it is soluble in the oil or present as particulates. Preparation by simple dilution may not be sufficient for very low concentrations of elements as the dilution may inhibit the ability to measure low levels due to non-detection, precipitation or settling out of the metals of interest. 

In seawater systems, the oxidation method chosen for analysis of the organic carbon depends on the fraction (DOC, POC or VOC) of interest, the origin of the sample, and the type of information required. However, analytical results from different methods cannot be compared readily. By examining these various analytical methods for the measurement of the dissolved, particulate, and volatile fractions of the organic matter, the sources of the differences in the reported results may be better understood. 

A number of analytical methods [66, 67] involving pyrolysis of polymers have been reported in the literature. Michal and co-workers [68] developed a method using direct gas chromatography (GC)-mass spectrometry (MS) for their study of the combustion of polyethylene (PE) and PP. Morikawa [69] used GC to determine polycyclic aromatic hydrocarbons in the combustion of polymers. Liao and Browner [70] also described a method for the determination of polycyclic aromatic hydrocarbons. Many other workers have studied soot and smoke formation and their mechanisms in the combustion of polymers. Generally in these studies, relatively simple and specific methods were used, which were appropriate for the intended tasks. However, these methods are not suitable for complete analysis of the very complex smoke particulates resulting from combustion of many polymers. Most methods have been developed either for volatile compounds of low molecular weight or for polycyclic aromatic hydrocarbons. Joseph and Browner [71] developed a method that can be used to... 

The need to develop rehable analytical methods to determine the levels of both gaseous and particulate pollutants has gathered considerable impetus in the last 20 years or so and reliable, specific, rapid-response techniques are now available for many pollutants. In order to review the available methodology for the analysis of the various priority pollutants, it is necessary to classify them according to the physical form in which they are generally present in the atmosphere. The two classes of pollutant form are gaseous pollutants and particulate species. 

Samples of airborne particulates preferably are collected on glass fiber or membrane filters. The analytical method of choice is atomic absorption spectroscopy after acid digestion of the filter and appropriate dilution. However, other methods such as spectrography, polarography, spectrophotometry, neutron activation analysis, and anodic stripping voltammetry are also used. 

The analytical methods used for the determination of uranium in environmental samples are basically the standard methods reviewed in brief in Chapter 1. The main differences are in the sample preparation procedures required for the analysis of the variety of environmental samples that include soil of different types, sediments, diverse types of vegetation, water from different sources with a wide range of acidity, salinity, suspended matter, etc. In addition, the environmental samples may include airborne particulate matter, vapors, and gases, as well as special samples involved in the food chain that may affect humans. Einally, the interplay of uranium (and other contaminants) between the environmental compartments—for example, the transfer factors of uranium from soil-to-plant or from vegetation to food products (e.g., free-range grazing cattle) are also part of the media that need to be characterized. 

PN is included in the TON, if unfiltered samples are digested by these analytical methods, and it might be determined as difference between TON and DON. However, a more accurate determination of PN requires the analysis of the particulate collected by filtration independently with respect to the determination of dissolved nitrogen forms, as PN often constitutes only a small fraction of the total nitrogen in the natural waters. The digestion of PN collected on filters can be achieved by KD and PO methods, but the most important technique used for this analysis is the HTO method (Figure 14.1). 

Personal Diesel Particulate Sampling and Analysis Equipment and analytical methods to accu-... 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

Samples of particulate matter can be subjected to many of the above analytical techniques in chemical characterization. The following methods are, however, particularly applicable to analysis of physical characteristics of particulate matter isolated from air sampling. 

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