Hazardous Chemicals Handbook 2 Episode 9 ppt

the test sample is aspirated into a flame where chemical reduction of metal ions to metal atoms occurs. Light is emitted at the discrete absorption wavelength for the metal. A disadvantage is the need for a separate lamp for each element. Emission spectrometry is therefore preferred. Here test material is heated and vaporized using a DC or inductively-coupled plasma generator, after which an optical emission spectrum as a function of wavelength is recorded. An advantage of this technique is that a range of metals or metalloids can be analysed simultaneously. Chemiluminescence Here a chemical reaction produces a molecule with electrons in an excited state. Upon decay to the ground state the liberated radiation is detected. One such example is the reaction between ozone and nitric oxide to form nitrogen dioxide emitting radiation in the near infra-red in the 0.5–3 µ region. The technique finds use for measuring nitric oxide in ambient air or stack emissions. Chromatography This technique permits the separation of a mixture of compounds by their partition between two immiscible heterogeneous phases, one of which is stationary. It detects substances qualitatively and quantitatively. The chromatogram retention time is compound-specific, and peak-height indicates the concentration of pollutant in the sample. Detection systems include flame ionization, thermal conductivity and electron capture. With gas chromatography the mixtures to be separated are in the vapour phase under the operating conditions of the equipment. A gas is used as the mobile phase to carry the sample over a column of stationary phase. Flame ionization detection operates by ionisation of molecules in a hydrogen flame and detection of the current change using a pair of biased electrodes. The current signal is directly related to the number of carbon atoms in the sample. Thermal conductivity detectors measure the change in electrical resistance of a heated filament as gas flows over it. It is most suitable for gases with very high, or very low, conductivity. Traditionally gas chromatography is a laboratory analysis but portable versions are now available for field work. In classical liquid chromatography a solution of solute percolates under gravity through a column packed with finely-divided solid when different compounds elute at different rates. In high-performance liquid chromatography (HPLC) the liquid is eluted from a packed column under high pressure using solvent. Detection systems include differential refractive index, diode array, electrochemical and ultra-violet-visible absorption. HPLC is used for analysis of less volatile compounds in liquid samples than those in gas chromatography. Because of its sensitivity (<1 ppm), ion chromatography has become extremely popular for analysis of ions in solution. It is a column-based method for separating ions similar to HPLC but using ion exchange columns and either high- or low-conductivity eluent. The most common detectors are electrical conductivity and ultra-violet absorption. It finds wide use in air pollution monitoring of rain waters, impinger solutions and filter extracts for anions such as sulphate, nitrate, chloride, and cations, including ammonia and metals. Colorimetry Use is made of colour changes resulting from reaction of pollutant and chemical reagents: colour intensity indicates concentration of pollutant in the sample. Reaction can take place in solution or on solid supports in tubes or on paper strips, e.g. litmus or indicator paper. Quantitative assessment of colour formation can also be determined using visible spectroscopy. Instruments are calibrated GASES AND VAPOURS 309 310 MONITORING TECHNIQUES such that colour intensity is directly related to concentration of contaminant in the test sample. Arguably the technique could also embrace simple acid-base titrations which utilize colour indicators to determine the end-point. Electrochemical techniques In electrochemical cells sample oxidation produces an electric current proportional to the concentration of test substance. Sometimes interferences by other contaminants can be problematic and in general the method is poorer than IR. Portable and static instruments based on this method are available for specific chemicals, e.g. carbon monoxide, chlorine, hydrogen sulphide. Coulometry measures the amount of current flowing through a solution in an electrochemical oxidation or reduction reaction and is capable of measuring at ppm or even ppb levels of reactive gases. Thus a sample of ambient air is drawn through an electrolyte in a cell and the required amount of reactant is generated at the electrode. This technique tends to be non-specific, but selectivity can be enhanced by adjustment of pH and electrolyte composition, and by incorporation of filters to remove interfering species. Ion-selective electrodes are a relatively cheap approach to analysis of many ions in solution. The emf of the selective electrode is measured relative to a reference electrode. The electrode potential varies with the logarithm of the activity of the ion. The electrodes are calibrated using standards of the ion under investigation. Application is limited to those ions not subject to the same interference as ion chromatography (the preferred technique), e.g. fluoride, hydrogen chloride (see Table 10.3). Table 10.3 Examples of applications of ion-selective electrodes Electrode Measurement range (ppm) Major interference Ammonia 0.01–17 000 Ionic – none Bromide 0.08–80 000 CN – , I – , S – – Chloride 0.35–3500 CN – , I – , Br – , S – – Cyanide 0.003–2600 I – , S – – Fluoride 0.02–1900 OH – Iodide 0.013–127 000 CN – , S – – Nitrate 0.6–62 000 I – , Br – , SCN – , ClO 4 – Sulphide 0.32–32 100 Ag + , Hg + Infra-red spectroscopy The basis of this technique is absorption of IR radiation by molecules over a wide spectrum of wavelengths to give a characteristic ‘fingerprint’ spectrum providing both qualitative and quantitative data on the substance. This versatile technique owes its success in occupational hygiene to the development of a portable spectrometer of the non-dispersive type which focuses on specific parts of the spectrum in which the pollutant shows peak absorption as opposed to scanning the entire spectrum. Table 10.4 identifies principal absorption peaks for selected gases. One advantage of IR is that the detector does not ‘react’ with the gases and the major functional components are protected and easily removed for maintenance. Since IR detection is potentially sensitive to temperature, the instrument requires approximately 15 minutes to equilibrate prior to use. Water vapour can seriously affect performance. Table 10.4 Main IR absorption peaks for selected gases Chemical Wavelength (micron) Carbon dioxide 4.35 Carbon monoxide 4.60 Methane 3.30 Nitric oxide 5.30 Nitrogen dioxide 3.70 Nitrous oxide 4.50 Sulphur dioxide 4.00 Table 10.5 UV wavelengths for selected gases Gas Wavelength (nm) Ammonia 200 Chlorine 280–380 Hydrogen sulphide 200–230 Nitrogen dioxide 380–420 Oxygen/ozone 170 Sulphur dioxide 285 Compound specific analysers Several instruments are available that are designed to monitor a specific compound rather than a wide range of substances. The detection system varies according to the pollutant. A selection is given in Table 10.6. Mass spectrometry This technique relies on the formation of ions by various means in a high-vacuum chamber, their acceleration by an electrical field and subsequent separation by mass/charge ratio in a magnetic field and the detection of each species. It can be used for both inorganic and organic substances, be very sensitive, and be of value in examining mixtures of compounds especially if linked to glc. Usually this is a laboratory technique but portable or ‘transportable’ models are now available. Ultra-violet spectrometry Outermost valency electrons in atoms are excited by ultra-violet radiation. The excited electrons return to the ground state liberating energy by disassociation, re-emission, fluorescence, or phosphorescence. The level of UV radiation absorbed follows the Beer–Lambert law (page 312). The peak wavelength for selected gases is given in Table 10.5. Photo ionization detectors (PIDs) use ultraviolet light to ionize gas molecules such as volatile organic compounds; the free electrons collected at electrodes result in a current flow proportional to the gas concentration. The lamp requires constant cleaning and hence may have limited life expectancy. GASES AND VAPOURS 311 312 MONITORING TECHNIQUES Particulates 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. Mass concentration Simple gravimetry of the sample is likely to be an integral component of the determination of, e.g., the concentration of, or exposures to, airborne dust. Care is required to avoid errors arising from absorption of atmospheric moisture. This can be avoided by using blank filters, by conditioning the filters in an atmospherically-controlled room, or use of a desiccator. Automatic aerosol mass concentration can be achieved directly by collecting particles on a surface followed by use of a piezoelectric or oscillation microbalance, or by β-attenuation sensing techniques, or indirectly using light scattering. The piezoelectric microbalance contains an electrostatic precipitator to deposit particles onto a vibrating silica crystal. The change in resonance frequency is converted into mass concentration using a microprocessor. Oscillating balances operate on the principle that air at 50°C (to avoid condensation) passes through a filter attached to the top of a tapered glass tube which vibrates at its natural frequency. As material is deposited on the filter the oscillation frequency changes directly in proportion to the increased mass. Beta gauges rely on the principle that when low-energy β particles pass through a material the intensity of the beam is attenuated according to Beer–Lambert law: Table 10.6 Selected examples of compound specific instruments Compound Detection system Ammonia Coulometry (e.g. Nessler method) Ion selective electrode Oxidation to NO x and chemiluminescence Carbon monoxide Polarography Infra-red Chlorine Ultraviolet spectroscopy Hydrogen chloride Polarography Ion-selective electrode Hydrogen fluoride Polarography Colorimetry Inorganic cyanides Colorimetry Ion-selective electrode Oxides of nitrogen Chemiluminescence Coulometry Oxygen Polarography Paramagnetic susceptibility Fluorescence Ozone Ultraviolet spectroscopy Chemiluminescence Coulometry Phosgene Ultraviolet spectroscopy Phosphorus and its compounds Flame photometry Toluene Ion-mobility spectroscopy Total hydrocarbons Flame ionization Sulphur compounds Flame photometry Coulometry UV fluorescence I = I o –ux where I and I o are the initial and attenuated beam intensities, u is the mass absorption coefficient and x is the absorber thickness. Light scattering Optical particle counters provide information on the particles present in different size ranges. A beam of light is collimated and focused onto a measurement cell. Light impinging on a particle is scattered and reaches a photomultiplier tube and converted to an output proportional to particle size. Particle size distributions are computed by appropriate software. Electrostatic sampling Particles become positively charged by a corona discharge and travel out of the charging chamber and collect on a substrate such as a microscope slide. Thus, the method is useful for particles which are to be examined by optical or electron microscopy. Optical microscopy This technique is invaluable for measurement of particle size, for counting the number of particles and for identification of particles by: • morphology, e.g. by comparison with standard particles, and • refractive index using polarized light microscopy. Electron microscopy With a resolution of 0.01 µm this technique outperforms optical light microscopy (0.1 µm) and is used, e.g., to examine fine particles such as metal fume. When linked to other facilities such as dispersive X-ray analysis, quantitative data can be obtained. X-ray techniques Crystals produce different diffraction patterns when subjected to bombardment of monochromatic X-ray sources and thereby provide unequivocal identification of crystalline materials. In X-ray fluorescence incident radiation induces electronic fluorescent emission in most atoms. The effects can be used both qualitatively and quantitatively for metals, alloys etc. Monitoring water quality Water is essential to man both directly and indirectly through agriculture and industry in which vast quantities are used for cooling, energy production, irrigation, refrigeration, washing, solvents etc. Risk of contamination can render water dangerous, unpleasant, or unusable. Point sources of water pollution include domestic and industrial waste whilst non-point sources include agricultural and urban run-offs. Analysis of water is important for estimating the nature and concentration of contaminants and hence fitness for use. Artificial contaminants are mainly of domestic and MONITORING WATER QUALITY 313 314 MONITORING TECHNIQUES industrial origin, and are increasing in similarity because of the expanding domestic use of chemicals (cosmetics, detergents, paints, garden insecticides and fertilizers). Water quality can be assessed by direct analysis of chemical substances or by indirect effects, e.g. pH, colour, turbidity, odour, impact on dissolved oxygen content. Chemical pollutants are classified as inorganic or organic. The former include metals (e.g. Mn, Fe, Cu, Zn, Hg, Cd, As, Cr), anions (e.g. Cl – , SiO 3 2– , CN – , F – , NO 3 – , NO 2 – , PO 4 ––– , SO 3 –– , SO 4 –– , S –– ), and gases (Cl 2 , NH 3 , O 2 , O 3 ). Methods for the examination of waters and associated materials published by the UK Department of the Environment are listed in Table 10.7. Selected methods for metal analysis are summarized in Table 10.8. Sampling protocols are described in, e.g., BS 6068 and BS EN 2567. Examples of BS methods for analysis of chemical contaminants in water are illustrated by Table 10.9. Biological methods are also given in BS 6068. Monitoring land pollution Sources of land pollution include transport accidents, spillage during chemical handling, loss of containment from storage tanks, leakage and landfill of waste effluent. An appreciation of the processes governing retention, degradation and removal of pollutants and the behaviour of specific pollutants in soil are essential in devising correct sampling and analytical strategies for assessing land contamination. Even soil itself varies in dynamics and composition from one site to another. Constituents include solid phase materials (such as complex mixtures of clays, minerals, organic matter), liquid aqueous phase of solutions (e.g. natural minerals, fertilizers, pesticides and industrial wastes) and gaseous phase components (e.g. oxygen, nitrogen, carbon dioxide, oxides of nitrogen, ammonia, hydrogen sulphide). The determination of toxic elements and organic substances in soils is a requisite of some EC directives as a means of controlling environmental pollution. Analyses are important when certain types of waste are recycled, e.g. by spreading sludge from water purification units on land, composting from household refuse. The choice of analytical method will be dictated by accuracy, sensitivity etc. Some key techniques are summarized in Table 10.10 and selected BS methods for monitoring soil quality are listed in Table 10.11. Monitoring air pollution Sampling Differences exist between the monitoring of pollution levels in ambient and workplace air. These reflect the differences in levels of contaminant, environmental standards, purposes for which data are used, etc. (see also Table 16.8). Thus, although similarities may exist in detection techniques, the sampling regimes, analytical details and hardware specifications may differ for assessment of the two environments. In general, atmospheric levels of contaminants are much lower in ambient air than those encountered in the workplace. As a result larger volumes of sample are often needed for ambient air analyses. This can be achieved using pumps of larger flow rate capacities, or by longer sampling times. Atmospheric monitoring involves first obtaining samples of the air with subsequent analysis of the samples collected. Examples of sampling techniques for gases and vapours are given in Table 10.12. Air samples can be pumped into instruments for direct analysis and data readout. Alternatively, they are collected in air-tight bags, or absorbed in liquids, or onto solid sorbents, for subsequent laboratory analysis using techniques such as those described on page 308. Common solid sorbents Table 10.7 Methods for the examination of water and associated materials published by the UK Department of the Environment A review and methods for the use of epilithic diatoms for detecting and monitoring changes in river water quality, 1993 Chlorphenylid, Flucofuron and Sulcofuron Waters (Tentative Methods based on methylation and GC-ECD, ion-pair HPLC and hydrolysis of Sulcofuron to 4-chloro-3-trifluoromethylaniline by GC-ECD), 1993 Cyanide in Waters etc. (by Reflux Distillation followed by either Potentiometry using a Cyanide Selective Electrode or Colorimetry, or Continuous Flow Determination of Cyanide or Determination by Microdiffusion), 1988 Determination of Aldicarb and other N -methyl carbamates in Waters (by HPLC or Confirmation of total Aldicarb residues and other N -methyl carbamates in waters by GC), 1994 Determination of the pH Value of Sludge, Soil, Mud and Sediment; and the Lime Requirement of Soil (Second Edition) (by Determination of the pH Value of Sludge, Soil, Mud and Sediment or by Determination of the Lime Requirement of Soil), 1992 Flow Injection Analysis, An Essay Review and Analytical Methods Information on Concentration and Determination Procedures in Atomic Spectrophotometry, 1992 Isolation and Identification of Giardia Cysts, Cryptosporidium Oocysts and Free Living Pathogenic Amoebae in Water etc., 1989 Kjeldahl Nitrogen in Waters [including Mercury Catalysed Method, Semi-automated Determination of Kjeldahl Nitrogen (Copper Catalysed, Multiple Tube, Block Digestion Method followed by Air Segmented Continuous Flow Colorimetry) Determination of Kjeldahl Nitrogen in Raw and Potable Water (Hydrogen Peroxide, Multiple tube, Block Digestion Method followed by Manual or Air-Segmented Continuous Flow Colorimetry) Semi-automated Determination of Kjeldahl Nitrogen (Copper/Titanium Catalysed, Multiple Tube, Block Digestion Method followed by Distillation and Air Segmented Continuous Flow Colorimetry), Air-segmented Continuous Flow Colorimetric Analysis of Digest Solutions for Ammonia], 1987 Linear Alkylbenzene Sulphonates (LAS) and Alkylphenol Ethoxylates (APE) in Waters, Wastewaters and Sludges by High Performance Liquid Chromatography, 1993 Phenylurea herbicides (urons), Dinocap, Dinoseb, Benomyl, Carbendazim and Metamitron in Waters [e.g. determination of phenylurea herbicides by reverse phase HPLC, phenylurea herbicides by dichloromethane extraction, determination by GC/NPD, phenylurea herbicides by thermospray LC-MS, Dinocap by HPLC, Dinoseb water by HPLC, Carbendazim and Benomyl (as Carbendazim) by HPLC], 1994 Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry- phosphomolybdenum blue method, Phosphorus in Waters and Acidic Digests by Spectrophotometry- phosphovanadomolybdate method, Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1-amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method, Pretreatment Methods to Convert Other Forms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992 Sulphate in Waters, Effluents and Solids (2nd Edition) [including Sulphate in Waters, Effluents and Some Solids by Barium Sulphate Gravimetry, Sulphate in waters and effluents by direct Barium Titrimetry, Sulphate in waters by Inductively Coupled Plasma Emission Spectrometry, Sulphate in waters and effluents by a Continuous Flow Indirect Spectrophotometric Method Using 2-Aminoperimidine, Sulphate in waters by Flow Injection Analysis Using a Turbidimetric Method, Sulphate in waters by Ion Chromatography, Sulphate in waters by Air-Segmented Continuous Flow Colorimetry using Methylthymol Blue], 1988 Temperature Measurement for Natural, Waste and Potable Waters and other items of interest in the Water and Sewage Disposal Industry, 1986 The Determination of 6 Specific Polynuclear Aromatic Hydrocarbons in Waters [Using High-Performance Liquid Chromatography,Thin-layer Chromatography], 1985 The Determination of Taste and Odour in Potable Waters, 1994 Use of Plants to Monitor Heavy Metals in Freshwaters [Methods based on Metal Accumulation and on Techniques other than Accumulation], 1991 MONITORING AIR POLLUTION 315 316 MONITORING TECHNIQUES Table 10.8 Methods for analysis of metal content of water Method Comment Sensitivity Spectrophotometry–Colorimetry One of most useful and versatile 10 –5 to 10 –7 M methods but can be time consuming (10 –9 with pre-concentration) Kinetic analysis (metal ion acts Sensitive, highly selective, only 10 –8 to 10 –9 M as catalyst) needs small samples Atomic absorption spectrophotometry: • Flame Simple, versatile; measures total 10 –6 to 10 –7 M • Flameless metal content. Knowledge of 10 –8 to 10 –9 M interfering effects important. Flame and spark emission Not very accurate. Gives multi- 10 –5 to 10 –8 M spectroscopy element analyses Neutron activation analysis Specialized, expensive 10 –9 to 10 –10 M Ion-selective electrodes Highly selective but insensitive 10 –5 to 10 –6 M and imprecise Polarography: Restricted to electroactive metals • Conventional 10 –5 to 10 –6 M • Modified 10 –6 to 10 –8 M Anodic stripping voltametry Applicable to few metals and 10 –8 to 10 –10 M dependent on metal speciation for gases and vapours (Table 10.13) include silica gel, activated charcoal, or organic resins. Silica gel is most useful for polar compounds whereas charcoal finds wide use for non-polar substances. Subsequently, the pollutant is generally removed from the solid phase by thermal desorption or by solvent extraction. The advantages and disadvantages of the two desorption techniques are summarized in Table 10.14. Their versatility is illustrated by Table 10.15 for use of charcoal. Pumps vary from large, stationary high-volume versions to pocket-size devices for use in personal dosimetry when operators wear sampling devices in the form of tubes or badges in lapels to collect air sampled in their breathing zone. Passive samplers are also available for monitoring gases and vapours in air. These are inexpensive devices which do not require a mechanical pump but rely on the concentration gradient between the air and sorbent material and the resultant molecular diffusion of the pollutant towards the sorbent according to Fick’s law: Q = DdC/dZ where Q = molar flux (mol cm –2 s –1 ), D = diffusion coefficient (cm 2 s –1 ), C = concentration (mol cm –3 ) Z = diffusion path length (cm). Because of the low rates of molecular diffusion, assessment of workplace air quality using passive samplers usually entails sampling for a working shift, and exposure periods of one to four weeks tend to be needed to measure concentrations in ambient air. Gases and vapours Analyses of gases and vapours tend to utilize the techniques described on page 308. Many of these methods were traditionally limited to laboratory analyses but some portable instruments are now available for, e.g., gas chromatography (Table 10.16) and non-dispersive infra-red spectrometry (Table 10.17). Table 10.9 Selected British Standard methods for monitoring water quality BS reference Substance Method BS 1427 General guide to methods for field and on-site techniques analysis of water BS 2690 free EDTA hydrazine spectrophotometry silica cyclohexylamine spectrophotometry morpholine spectrophotometry long-chain fatty acids spectrophotometry BS 6068 mercury flameless atomic absorption ammonium distillation and titration ammonium potentiometric ammonium manual spectometry phenol index spectrometric cyanide diffusion at pH6 cyanogen chloride ammonium automated spectrometry nitrate spectrometry using sulphosalicylic acid inorganically bound total fluoride digestion and distillation pH iron photometric calcium and magnesium EDTA titrimetric nonionic surfactants Dragendorff reagent anionic surfactants methylene blue titration arsenic, cadmium, cobalt, atomic absorption spectrometry copper, lead, magnesium, spectrometry nickel, zinc arsenic (total) spectrometry manganese formaldoxime spectrometry chemical oxygen demand sulphate barium chloride gravimetry borate spectrometry sodium and potassium atomic absorption spectrometry and by flame emission spectrometry selenium atomic absorption spectrometry aluminium spectrometry herbicides gas chromatography and mass spectrometry organochlorine compounds gas chromatography dissolved anions (bromide, liquid chromatography chloride, nitrate, nitrite, phosphate, sulphate, chromate, iodide, sulphite, thiocyanate, thiosulphate, chlorate, chlorite) liquid chromatography organic nitrogen and gas chromatography phosphorus 33 elements inductively coupled plasma atomic emission spectrometry nitrogen chemiluminescence mercury enrichment by amalgamation free and total chlorine titrimetric or colorimetric chlorophenols gas chromatography organophosphates gas chromatography dissolved oxygen iodometry or electrochemical probe phosphorus spectrometry MONITORING AIR POLLUTION 317 318 MONITORING TECHNIQUES chromium atomic absorption spectrometry hydrocarbon oil index solvent extraction and gas chromatography halogenated hydrocarbons gas chromatography (volatile) total organic carbon and dissolved organic carbon organically bound halogen alpha and beta activity suspended solids filtration through glass fibre electrical conductivity turbidity BS EN 11732 ammonium nitrogen flow analysis and spectrometry BS EN 12020 aluminium atomic absorption spectrometry BS EN 1483 mercury BS EN 1484 total organic carbon and dissolved organic carbon BS EN 12338 mercury enrichment by amalgamation BS EN 14911 dissolved sodium lithium ammonium, potassium, manganese, calcium, magnesium, strontium, barium ion chromatography BS EN 25663 nitrogen Kjeldahl BS EN 26777 nitrite molecular absorption spectrometry BS EN 7887 colour BS EN 1622 odour BS EN ISO 12020 aluminium atomic absorption spectrometry BS EN 13395 nitrate and nitrite nitrogen flow analysis and spectrometry BS EN ISO 9377 hydrocarbon oil index solvent extraction/gravimetry Table 10.9 Cont’d BS reference Substance Method Table 10.10 Common instrumental techniques for soil analysis Pollutant Method • Phosphorus or mineral nitrogen Spectrophotometry • Alkaline earth metals and transition metals Flame atomic absorption spectrometry • Alkali metals Flame emission spectrometry • Aluminium, boron, silicon Inductively coupled plasma atomic emission spectrometry • Lead in soil slurries Electrothermal atomic absorption spectrometry • Toxic organic compounds High pressure liquid chromatography One of the most commonly used portable, gas detection systems is based on colour indicator tubes employed, in the main, for grab sampling. Tubes are available to detect over 300 substances (Table 10.18) and, using a combination of tubes, a range of concentrations can be measured. The technique relies on a manually-operated bellows or piston pump to aspirate a fixed volume of atmosphere through a glass tube containing crystals (e.g. silica gel or alumina) impregnated with a reagent which undergoes a colour change upon reaction with a specific pollutant or class of pollutant. The length of stain that develops is proportional to the concentration of contaminant and the tube is generally calibrated to permit direct read-off in parts per million. Sample lines of several metres between the pump and tube allow atmospheres to be sampled, e.g., inside vessels. A smaller number of special tubes (Table 10.18(b)) are available for longer-term monitoring and these [...]... 5 .25 20 .25 20 .25 2. 25 2. 25 20 .25 20 .25 5 .25 20 .25 20 .25 20 .25 20 .25 20 .25 0.58 0. 39 0.33 0.5 0.015 0.04 0.06 0.17 0. 12 0. 62 0.58 0.1 0. 02 0. 0 29 0 .93 0. 12 0. 026 0.035 0.07 0. 09 0.03 0. 02 0.04 0 .2 0 .2 0.3 1.0 0 .2 0 .2 0.8 0.03 0.06 0 .2 0.8 0. 02 0.5 0.08 0.4 0.1 0.3 11.8 20 .25 0. 12 0.4 8.1 11 .9 8.5 3.58 8 .9 13.3 9. 8 9. 9 20 .25 0.75 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 0.4 1.7 0.086 0.015 0.055 0.05 0. 09. .. 10.5 9. 8 10.8 9. 1 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 0.0047 0.00 02 0.005 0.0055 0.00 32 0.08 0.1 0.3 0 .2 0.3 0 .2 0.07 10.4 8.0 9. 3 4.66 20 .25 0.75 20 .25 20 .25 0.14 0. 12 0.011 0.0003 0 .2 0. 02 0.3 0.1 14.87 20 .25 0.08 0.3 7 .9 20 .25 0.00 12 0.4 8 .99 6.8 8.7 11.0 10.36 20 .25 20 .25 20 .25 2. 25 20 .25 0.0016 0.006 0.005 0.46 0.03 0 .2 0.5 0.05 0 .2 3.0 8.5 8 .9 8.1 9. 9 9. 9 9. 6 10.1 8 .2 13.0 20 .25 9. 75 3.75 9. 75 9. 75... 0 .2 0.06 0. 02 9 .2 8.1 20 .25 9. 75 0 .26 0 . 29 0 .2 0 .2 9. 0 5 .25 0.17 0. 02 13.0 12. 4 8.1 11.5 11.4 9 .24 8.6 8.7 9. 75 4.7 3.4 9. 3 8.3 8.8 3.68 5 .25 20 .25 5 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 2. 25 20 .25 20 .25 20 .25 20 .25 0.45 0.04 0.7 0.0 02 0.08 0.04 0.0066 0.01 0.031 0.016 0.56 0 .28 0.054 0. 12 0.067 0.06 1.0 0. 02 0.05 0.4 0.06 0.3 0.1 0.7 3.0 0.03 0.10 0.5 0.3 1.0 8.5 20 .25 0.335 0.08 3 .9 8 .27 ... 9. 0 9. 5 9 .2 20 .25 20 .25 2. 25 0 .2 0.11 0.36 0.1 0.05 0. 02 8.6 8.5 8.8 20 .25 20 .25 5 .25 0. 12 0. 026 0.3 0 .2 0.1 0.1 9. 9 8.7 20 .25 20 .25 0. 02 0. 02 0.3 0.5 8.6 20 .25 0.015 0 .2 9 .2 20 .25 0.063 0.1 9. 9 9. 0 8 .9 20 .25 20 .25 5 .25 0.04 0.5 0.38 0. 02 0 .2 0.05 8.7 11.8 20 .25 20 .25 0.10 0.013 0.01 0.3 12. 1 13.0 8 .9 20 .25 20 .25 2. 25 0.15 0.0017 0 .24 3.0 1 .2 0.06 Analytical Wavelength (µm)(1) 2- Ethoxyethyl acetate... 8.5 7 .9 8.6 8.7 5 .25 0.75 20 .25 20 .25 20 .25 0.065 0.13 0.0 09 0.6 0.053 0 .2 0. 02 0.4 0.04 0 .25 11.6 8.8 3.38 8.5 20 .25 20 .25 20 .25 2. 25 0.00003 0.1 0.008 0 .21 0.6 0.3 0.4 0.03 11.1 7 .9 9.0 4.86 5.3 11.8 9. 0 6.17 11.0 9. 3 11.8 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 20 .25 0.3 0.007 0.05 0.0003 0.015 0.005 0.08 0.048 0.35 0.056 0.0076 0.3 0 .2 0 .2 0.005 2. 0 0 .2 0.6 0.1 0.03 0 .9 0.7... (m) (2) Absorbence(3) Minimum Detectable Concentration (ppm)(4) (20 metre cell) 3.04 20 .25 0.0083 0.4 9. 4 9. 4 8 .2 9. 6 9. 6 8 .25 3.4 11 .2 8.0 8.7 8.5 8 .9 3.4 8 .2 7.65 9. 75 9. 75 2. 25 8 .25 20 .25 20 .25 20 .25 5 .25 2. 25 6.75 20 .25 0.75 0.75 20 .25 20 .25 0 .27 0 .22 0.4 0.30 0 .25 0.07 0. 12 0.078 0.63 0.45 0. 025 0.17 0 .24 0.06 0.0 72 0.14 0.13 0. 02 0.08 0.3 0. 02 0.4 0 .2 0. 02 0. 12 0.1 0.07 0.4 0 .2 0 .2 12. 0 20 .25 0.03... 0.03 0 .9 0.7 4.50 3.4 3.4 8.5 10 .9 3.4 8.1 20 .25 0.75 0.75 5 .25 5 .25 2. 25 20 .25 0.3 0.40 0. 42 0 .23 0.63 0.65 0.011 0.07 0. 02 0. 02 0.1 0.05 0. 02 0.04 8.5 11.8 10.1 20 .25 20 .25 20 .25 0.0 0 29 0.0 027 0.0003 0 .9 0.03 1.0 3.35 8.1 9. 4 7 .9 10.4 9. 8 12. 0 2. 25 0.75 9. 75 20 .25 20 .25 20 .25 20 .25 0. 79 0.18 0. 39 0 .2 0.11 0. 12 0. 32 0.03 0. 02 0 .2 0.7 0.1 0.3 0.3 14 .2 20 .25 0.05 0 .2 Table 10.17 Cont’d Compound Quinone(5)... 50 20 0 50 20 0 25 100 50 100 50 50 10 50 5 100 5 100 10 100 25 50 5 20 0 100 20 0 100 50 100 25 100 25 100 25 100 10 100 25 50 50 50 25 100 25 50 1 50 25 100 25 100 10 50 25 50 25 25 5 25 1 50 1 50 5 50 10 25 1 100 50 20 0 50 25 50 10 50 10 50 10 50 5 7 5.7 14 99 ± 5 14 2 CS2 91 ± 5 CS2 9. 3 95 ± 10 CS2 14.8 88 ± 5 CS2 21 CS2 15 93 ± 5 CS2 9 96 ± 5 CS2 88 ± 5 CS2 29 95 ± 5 CS2 12. 3 96 ± 5 CS2 0.6 12. 5 90 ... 157.5 21 00 23 .5 –3 52 3 52 –4700 15 29 5 29 5 – 590 0 3.5 26 3 26 3 –1400 6.8 –1 02 1 02 –13 62 20 –300 300 –4000 0.38 –7.6 3.8 –38 0.35 –14 3 24 12 – 120 4 .2 –315 315 –1680 2. 5 –184 184 98 0 4.6 –70 70 –700 2. 4 –36 36 –480 20 0 100 20 0 20 0 20 0 100 20 0 100 100 10 20 0 100 20 0 100 20 0 50 20 0 100 20 0 100 100 25 100 10 20 0 10 20 0 25 20 0 50 100 10 – 20 0 – 20 0 100 20 0 50 20 0 50 20 0 50 20 0 25 20 0 50 100 100 100 50 20 0... 12. 0 20 .25 0.03 0.07 9. 5 7 .9 8.4 9. 5 9. 5 3.4 5 .25 20 .25 20 .25 0.75 5 .25 20 .25 0.31 0.77 0.15 0.43 0.3 0. 02 0 .2 1.0 0.03 0.05 0.1 0.1 8.6 7.6 9. 75 20 .25 0.14 0. 021 0 .2 0.4 8.8 8.0 13.4 9 .2 3.4 9. 5 8 .9 20 .25 20 .25 20 .25 2. 25 2. 25 20 .25 20 .25 0. 19 0. 39 0.14 0.4 0.84 0 .24 0.18 0.05 0. 02 1.5 0.06 0.04 0 .2 0.3 13.4 0.75 0 .25 0 .2 Analytical Wavelength (µm)(1) Methyl ethyl ketone (MEK), see 2- Butanone N-methyl . 5–100 24 .8– 495 100 50 25 (Freon 12) 100 20 00 495 99 00 10 5 1 1,1-Dichloroethane 1–15 4–60 100 100 50 7.5 100+ CS 2 15 20 0 60–300 50 25 10 1 ,2- Dichloroethylene 2 25 7 .9 99 100 50 25 5.1 100+ CS 2 25–400. 5–75 17.5 26 3 100 50 25 12. 5 90 ± 10 CS 2 75–800 26 3 28 00 25 10 5 Ethyl acrylate 0.5–5 2 20 20 0 20 0 100 <5 95 ± 5CS 2 5–50 20 20 0 20 0 100 50 Ethyl alcohol 5–100 9. 4–188.5 100 50 25 2. 6 77 ±. 0.5–10 2. 3–46 20 0 100 50 >5.5 93 ± 51 10–100 46–460 50 25 10 Ethyl chloride 10–150 26 – 390 100 50 25 9. 7 CS 2 150 20 00 390 – 520 0 10 5 1 Ethyl ether 5–75 15 22 7 100 50 25 7.5 98 ± 57 75–800 22 7 24 20