Filter cellulose ester

Collect asbestos on a special, 0.8 micrometer pore size, 25 mm diameter mixed cellulose ester filter, using a back-up pad. 

SRM 1876b is intended for use in evaluating transmission electron microscopy (TEM) techniques used to identify and count chrysotile fibers. This SRM consists of sections of mixed-cellulose-ester filters containing chrysotile fibers deposited by an aerosol generator. 

RM 8411 consists of a section of collapsed mixed-cellulose-ester filters with a high concentration (138 fibers/o.oi mm) of chrysotile and a medium concentration (43 fibers/o.oi mm) of amosite. It is intended for use in evaluating the technique used to identify and count asbestos fibers by TEM. 

Experimental studies of the adsorption of polyelectrolyte have been reported by several authors Pefferkom, Dejardin, and Varoqui (3) measured the hydrodynamic thickness of an alternating copolymer of maleic acid and ethyl vinyl ether adsorbed on the pore walls in cellulose ester filter as a function of the molecular weight and the concentration of NaCl. Robb et al. (4) studied the adsorption of carboxy methyl cellulose and poly (acrylic acid) onto surfaces of insoluble inorganic salts. However, their studies are limited to the measurements of adsorbance and the fraction of adsorbed segments. 

A Typical Profile of Elements Measured by X-Ray Fluorescence in Cotton Dust Collected by a Vertical Elutriator on a Cellulose-Ester Filter (20)... 

Sampling and Analytical Precision and Accuracy. The accuracy of results obtained from a sampling and analytical method are determined by comparison with an independent method. The aerosols of phosphoric and sulfuric acids were collected on mixed cellulose ester filters (14 ) and analyzed by ion chromatography. Table V shows the collection efficiency of the 7-mm O.D./700-mg silica gel collection tubes with respect to the results obtained from filter samples, and the precision obtained from calculation of the pooled relative standard deviation. 

The method developed for sodium fluoroacetate is based on collection of the sample with cellulose ester filters especially low in extractables (Toyo-cel cellulosic ester membrane filters from Nuclepore were used). The samples were extracted with water and analyzed by ion chromatography. Other MCE filters contained high levels of extractables Cfrom wetting agents, surfactants) that... 

The first of the set is chlordane (Figure 2). In this case chlordane was collected primarily on the mixed-cellulose ester filter with about 10% collected on the sorbent. If the sampling device was only tested over the proposed sampling period, one hour in this case, vapor collected on the sorbent may not have been detected. Hence, extended sampling periods are necessary to realistically test collection efficiency of the individual sampling media in the train. Also, at higher temperatures and lower chlordane concentration, the fraction collected on the sorbent may be substantially increased. 

In the first experiment, a total of 5 cellulose ester filters were spiked with the equivalent of 1.5 yg of arsenic from each of the 5 species, MMA, DMA, p-APA, As(lll), and As(V). The filter spikes were allowed to dry and were then extracted ultrasonically in 25 mL of deionized water. The resulting extracts were stored at room temperature and analyzed three separate times over a period of one week. The first analysis was performed the same day that... 

Table II. Stability at room temperature of aqueous extracts of spiked cellulose ester filters as a function of time.

Over the 7-day period, the percent recovery for MMA decreased to 23%9 while the percent recovery for unresolved DMA and As(ill) increased to VL50. (The filter extracts were not analyzed a second time to quantitate DMA and As(ill) individually.) Since these phenomena occurred only for extracts containing cellulose ester filter material, it appeared that the filter material itself in solution caused chemical changes. This same phenomenon might occur also on the cellulose ester filter under ambient sampling conditions, with the rate of such a reaction dependent upon the temperature and relative humidity of the sampled air. 

As shown above extracts of organoarsenicals obtained from cellulose ester filters and analyzed by the developed method suffer severely from lack of stability. To evaluate conclusively and also to find an appropriate filtering medium, experiments were performed to simultaneously test the stability of organoarsenicals on cellulose ester, Fluoropore, and Mitex filters. The experimental design is outlined in Figure 1. 

The percent recoveries of MMA and p-APA from cellulose ester filters which were stored three days before extraction and... 

Removal of the undissolved cellulose ester filter material from aqueous extracts did not appear to improve the stability of the organoarsenicals. 

Prior to high-performance liquid chromatography (HPFC), samples were filtered through a 0.2-gm pore size mixed cellulose ester filter (Schleicher Schuell, Dassel, Germany). Buffer components such as acetic acid, citric acid, maleic acid, and succinic acid were separated on an Aminex HPX-87H (Bio-Rad, Hercules, CA) organic acid column at 65°C using a... 

Air (total chromium) Particulate matter collected on cellulose ester filter, digested with aqua regia ICP-AES 1 pg/m3 87-102% at 0.5-100 pg Lo and Arai 1988... 

Air (total chromium) Air particulate collected on cellulose ester filter, wet wash with HCI/HNO3 Flame atomic absorption 0.06 pg/sample 98% at 45-90 pg/sample NIOSH 1994c (Method 7024)... 

Asbestos samples are collected by drawing contaminated air at a flow rate of 1.5 liters of air per minute through an open-face 37mm filter holder containing an 0.8 micron cellulose ester filter. (The filter is housed in a three-piece filter holder or cassette. 

These atomization techniques are used in NIOSH, AIHA, and APHA approved (recommended) methods (5-7). Although the purpose of this discussion is MS techniques, one must briefly consider collection of samples. The primary method of collecting metal dust samples and fume samples are 0.8 urn and 0.45 urn mixed cellulose ester filters. The filter is dissolved in acid or leached with dilute base, acid, or distilled water to give an analyte for MS analysis. A general procedure P CAM 173 (5), was developed by NIOSH for the analysis of metals. This method provides a starting point and standard of comparison for the analysis of metals. 

Chromium. Chromium is not an easily analyzed element because three distinct standards are listed by OSHA (Tables IV and V ). One standard exists for hexavalent chromium, chromic acid and chromates, another standard for soluble chromium compounds and chromous salts, and another standard for insoluble chromium compounds and chromium metal. The permissible amount of chromium in air decreases as the oxidation state increases. The analysis of chromium is further complicated by the multiplicity of NIOSH methods for chromium compounds. Hexavalent chromium shall be collected on PVC filters, although a criteria document for chromic acid (14) specifies mixed cellulose ester filters. The analytical method described in the hexavalent... 

Light Microscopic Method. Phase contrast microscopy (PCM) accurately assesses fiber exposure levels for fibers 5 pm in length and >0.25 pm in diameter. Furthermore, PCM cannot differentiate between asbestos and nonasbestos fibers. Currently, the standard method for the determination of airborne asbestos particles in the workplace is NIOSH Method 7400, Asbestos by Phase Contrast Microscopy (NIOSH 1994a). OSHA considers that sampling and analytical procedures contained in OSHA Method ID-160 and NIOSH Method 7400 are essential for obtaining adequate employee exposure monitoring. Therefore, all employers who are required to conduct monitoring are required to use these or equivalent methods to collect and analyze samples (OSHA 1994). In NIOSH Method 7400, asbestos is collected on a 25 mm cellulose ester filter (cassette-equipped with a 50 mm electrically-conductive cowl). The filter is treated to make it... 

In order to distinguish between soluble and insoluble Pt in air, the British Health and Safety Executive employed leaching of air dust in workplace atmosphere collected on cellulose ester filters in 0.07 M HCl to solubilize the soluble Pt fraction (MDHS 46,1985). Alt et al. (1993) also used this procedure to determine soluble Pt in milligram... 

---