Chemistry: analytical and immunological testing – Including sample preparation – Liberation or purification of sample or separation of...
Reexamination Certificate
1995-01-25
2004-07-13
Alexander, Lyle A. (Department: 1743)
Chemistry: analytical and immunological testing
Including sample preparation
Liberation or purification of sample or separation of...
C436S052000, C422S069000, C422S088000, C055S423000
Reexamination Certificate
active
06762060
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to apparatus and methods for monitoring the concentrations of hazardous airborne substances, especially lead in fire ranges, in and around lead-smelting or lead-fabricating facilities, lead-acid battery or pottery and ceramic plants, radiator repair and other soldering shops, dwellings contaminated with chipping lead paint, and other locations were elevated respirable levels may pose a hazard to human health.
According to recent estimates, in the State of California alone, almost 400,000 workers have elevated lead blood levels, of which some 60,000 persons may have potentially toxic lead levels. Similar data from Texas, New York, and New Jersey, “show that there is an epidemic of occupational lead poisoning in the United States” (Chicago Tribune, Aug. 30, 1990, Sec. 1, Page 4).
It is therefore the purpose of this invention to provide a cost-effective method and instrumentation for monitoring airborne lead concentrations in said locations to help prevent lead poisoning among exposed persons. The need for “practical, low-cost ways of monitoring lead concentrations at firing ranges” has been well recognized (D. J. Schaeffer, R. A. Deem, and E. W. Novak, Am. Ind. Hyg. Assoc. J., 51(2):84-89 (1990)). The Occupational Safety and Health Administration's permissible exposure limit to airborne lead is a concentration of 5×10
−5
g Pb/m
3
averaged over an 8-hour period. An experimental ambient-air lead monitor based on X-ray fluorescence spectrometry has demonstrated a detection capability of 5×10
−5
g Pb/m
3
in 40-60 min and of higher concentrations in shorter times. Comparable or longer periods of time are required by the present NIOSH Method 7082 (issued by the National Institute of Occupational Safety and Health on Feb. 15, 1984), which is based on atomic absorption spectroscopy. The NIOSH method calls for a sampling flow rate of 1-4 L/min and a minimum volume of 200 L, which necessitates a minimum sampling time of 200 L/4 L-min
−1
=50 min. It is thus obvious that shorter sampling times and higher detection sensitivities are needed for more cost-effective lead monitoring.
It is therefore another object of this invention to provide an inexpensive, portable, and rapid means for estimating airborne lead concentrations.
Other objects of the invention will become apparent to professionals in the health monitoring, industrial safety and hygiene, environmental, metallurgical, and related areas following perusal of the complete specification.
SUMMARY OF THE INVENTION
Briefly, the invention consists of sampling air at a rate in excess of 100 L/min, preferably at 200-300 L/min, and collecting therefrom a substantial fraction, i.e., at least 20%, preferably 60-100%, of airborne particulates, rapidly solubilizing the hazardous substance of interest (analyte), such as lead, from the collected particulates into a sample of liquid extractant, and determining the concentration of the analyte in the extractant sample. The high-rate air sampling and particulate collection may be effected with a high-throughput filter cartridge or with a recently developed portable high-throughput liquid-absorption air sampler, wherein an asymmetric air inlet is so designed as to impart a partly downward and rotational motion to the in-rushing air. Rapid solubilization of lead is achieved by a liquid extractant comprising 0.1-1 M of acetic acid or acetate, preferably at a pH of 5 or less and preferably with inclusion of 1-10% of hydrogen peroxide. Rapid determination of the lead content in the liquid extractant may be effected with an indicator tape or an electrochemical analyzer.
REFERENCES:
patent: 5173264 (1992-12-01), Zaromb et al.
Microgon Inc., “MiniKap 225/500 Microfitration Modules”, Jul. 1990.*
DeAngelis et al. “Differential Pulse Anodic Stripping Voltammetry in a Thin-Layer” Analytical Chemistry, vol. 48, No. 14, Dec. 1976.*
Gunasingham et al. “Computer Automation of Anodic Stripping Voltammetry with a Mercury Film Wall—Jet Electrode”, J. Electroanal. Chem. 186(1985) 51-61.*
Heijne et al. “The Formation and Properties of Mixed Lead Sulfide-Silver Sulfide Membranes for Lead(II)-Selective Electrodes” Analytica Chimica Acta, 100(1978) 193-205.*
Fleet et al., “Performance and Evaluation of a Handheld Electrochemical Monitor for Toxic Metals”, No Source or Publication Date Supplied.*
Lawson et al., “Evaluation of Chemical Reaguts For Quick Estimation of Air-Borne Lead Concentrations”, NCEL Contract Report (CR91.009), Aug. 1991.*
Zaromb et al., “Portable High-Throughput Liquid-Absorption Air and Aerosol Sampler” Abstract Present at the Haztech Int.Conf. Pittsburgh, Pa. 5/14-16/91.*
Product cover letter col Product Lit. of “MinikKap 225/500” from Microgon, Inc., Laguna Hills, Ca. (No Date).*
Oakton Electrascon (EC-1 Series) product liteture with a price list effective Mar. 1, 1991.
Alexander Lyle A.
Zaromb Solomon
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