Measurement of vapour–aerosol mixtures† Dietmar Breuer Berufsgenossenschaftliches Institut fu�r Arbeitssicherheit (BIA), Section Analytical Chemistry, Alte Heerstrasse 111, 53757 Sankt Augustin, Germany. E-mail: D.Breuer@hvbg.de Received 16th March 1999, Accepted 25th May 1999 A particular problem in connection with the measurement of hazardous substances is posed by substances or groups of substances which may occur simultaneously in vapour and aerosol form.It is possible that, during sampling, the distribution of the two phases on the sampling medium is subject to changes due to vaporisation of aerosol or condensation of vapour. For workplace assessment purposes, it makes sense to consider the sum of vapour and aerosol, which never changes. Only then can the results of diVerent sampling systems be compared.There are several ways in which vapour–aerosol mixtures can be sampled. Combining adsorption tubes or denuders with filters is the most important. Twofold requirements must be considered in the development of such sampling methods: those applying to sampling systems for aerosols as well as those for vapour sampling systems. To satisfy the requirements resulting from these substances and groups of substances, BIA’s personal sampling system (PGP) was extended.In addition to the sampling head for inhalable dust (GSP), originally designed for a flow rate of 3.5 L min-1, sampling heads for 0.5, 1 and 10 L min-1 were developed. Tests were conducted on these sampling heads, which all showed compliance with the requirements defined for inhalable fraction sampling.For the combined sampling of aerosol and vapour, a system was created which allows a filter and up to three usual adsorption tubes to be loaded simultaneously. The measuring methods for alkanolamines, inorganic acids and explosives are described to illustrate the use of the above PGP extensions and the framework conditions, account of which must be taken in the sample treatment.DiVerent types of separation system are used for particles, 1. Introduction while filters have proven to be particularly suitable. In addition, Within the framework of analytical determinations, the sam- cyclone dust separators or cascade impactors are applied. The pling procedure often poses particular problems. While, now- sampling of particles is usually carried out by active sampling, adays, most instrumental analytical methods allow errors to whereby the characteristics of diVerent particle sizes must be be limited to a few percent, serious errors may still be made taken into consideration. Nowadays, samples are taken of during the sampling procedure.inhalable or respirable dust fractions. The procedure applied to the sampling of hazardous sub- This paper will especially concentrate on aerosol–vapour stances in air primarily depends on the state of aggregation of mixtures or so-called mixed-phase aerosols, since they have the substance in the atmosphere.The following scenarios several peculiarities which must be considered in the sampling are possible. process as well as in the subsequent analytical determination.(i) At sampling temperature (room temperature), a sub- The framework conditions that must be observed will be stance is gaseous or suYciently volatile and only occurs in the treated in depth, and potential solutions will be discussed on gas phase. Examples include ethane and acetone. the basis of examples. (ii) At room temperature, a substance is not volatile and occurs as an aerosol.In this case, a solid matter may occur in 2. Sampling of gas–vapour mixtures: how can gas– the surrounding atmosphere in the form of a dust or fume, while a liquid may occur as droplets in the form of a mist. vapour mixtures be sampled? Examples include metal oxide dust and sulfuric acid. This situation may arise when a substance, because of its (iii) At room temperature, a substance is semi-volatile and physical properties, occurs at room temperature in a stable may occur as an aerosol and a vapour at the same time.vapour and particle phase over a certain period of time. The Possible distribution in the atmosphere in this case is solid– same would apply to a group of substances with similar gaseous or liquid–gaseous.chemical properties, but whose physical properties are so The first two examples are part of the routine of every air divergent that they occur as mixed-phase aerosols. This is true analyst. Numerous possibilities exist for collecting ‘pure for homologous series; classic representatives are the aliphatic vapours’ or ‘pure aerosols’. hydrocarbons and polycyclic aromatic hydrocarbons (PAHs).Gases and vapours can be bound reversibly to sorbent Highly volatile hydrocarbons, such as hexane and octane, material such as active charcoal, silica gel or tenax. They can only occur as vapour in the atmosphere, even if they are used either be separated on coated surfaces or absorbed in liquids. as liquids in the workplace. Low volatile hydrocarbons, such In active sampling, the air under examination is conducted by as eicosane (C20), only occur in particle form.The area in a pump through the sampling system. In passive sampling, between these two ends of the scale, reaching more or less separation is achieved by diVusion. from tetradecane to octadecane, is characterised by the transition from the gaseous into the particle phase. Since these hydrocarbons are always used as mixtures, it is diYcult to †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999.J. Environ. Monit., 1999, 1, 299–305 299take combined vapour–aerosol samples of high boiling mineral The total quantity of vapour and aerosols was similar for all sampling systems. oil mixtures. PAHs with three- or four-ring systems are volatile or semi- 2.2.Sampling techniques for mixed-phase aerosols volatile, while PAHs with five or more rings are non-volatile. Normally, a wide range of PAHs occur simultaneously at the In the case of combined vapour–aerosol sampling, the requireworkplace, so that combined vapour–aerosol sampling is ments of EN 481, 482, 1076 and 1232, applying to both useful. The known methods use a combined sampler with a aerosols and vapours, have to be met.4–7 For the sampling of filter for aerosol sampling and an XAD tube for vapour mixed-phase aerosols, there are various possibilities. sampling.1 2.2.1.Denuder and filter. This combination is easy to use. 2.1. Combined vapour–aerosol sampling It has to be observed, however, that the vapours must be separated first and that the intake of the denuder must comply During the last few years, a working group of CEN/TC 137 with the requirements for particle sampling systems.A serious has dealt with the problem of sampling of aerosol–vapour error can be made if the aerosol partly evaporates after being mixtures. The working group considered its main task to collected. It should be ensured that such fractions are also gather solutions for the sampling of mixed-phase aerosols.It collected. The sampling conditions applying to denuders on is intended to publish the results achieved by the working the one hand and filters on the other can be easily made group as a pre-standard.2 compatible. The following are the basic statements made by the working group. 2.2.2. Filter and pumped sorbent tube.This combination will (i) The actual phase distribution of mixed-phase aerosols in certainly be applied in most cases, as it is easy to handle and the atmosphere cannot be determined. The only indicative quite compact. Another advantage of this assembly is that the statement that can be made concerns the total vapour–aeroexperience obtained with filter sampling and tube sampling sol quantity.can be drawn upon. It can be considered a disadvantage, (ii) Although it is known that aerosols and vapour aVect however, that the quite deviating sampling conditions for people’s health diVerently, this concentration is determined filters and sorbent tubes need to be made compatible with in total. each other. (iii) The aerosol fraction of vapour–aerosol mixtures shod be collected on the basis of the inhalable dust fraction. 2.2.3.Impinger and filter. The intake of the impinger has to These basic statements derive from the knowledge that the meet the requirements for collecting aerosols. The secondary balance between the phases can easily alter with varying filter must collect small particles that may pass the impinger. sampling conditions: a high volume flow during the sampling Errors may also result from stripping eVects.procedure can entail the evaporation of collected aerosols, whereas a low volume flow can lead to the condensation of 2.2.4. Reagent-impregnated systems. This procedure is based vapours; changes in temperature can either lead to evaporation on surface-coated filters, foams or similar applications.It can (rising temperature) or condensation (falling temperature). only be used for reactive substances. Since vapour and aerosols The distribution between vapour and aerosols could be are collected on the same sampling medium, eVorts have to influenced to a certain extent by the type of sampling system be made to carefully match the sampling conditions for or could even be manipulated deliberately.A partly volatile the mixture. substance, for example, exclusively subject to an aerosol limit value, could be measured by a sampling system with an 2.2.5. Filter and diVusive sampler. In this case, the aerosol extremely high volume flow, which would lead to a ‘more is separated before the vapour. Normally, the air flow is split favourable’, but unrealistic, result. after the filter, and the minor flow is conducted past the Parallel tests on the sampling of mineral oils have led to the collector.The advantage of this procedure is the suitability of conclusion that the use of diVerent sampling systems may the aerosol collector for relatively high volume flows. distort the aerosol concentration (Table 1). The sampling system of Berufsgenossenschaftliches Institut fu� r 2.3.BIA sampling systems for mixed-phase aerosols Arbeitssicherheit (BIA) was compared with combined Millipore cassette/sorbent tubes. The obvious result was that, Applications can be developed for all the examples mentioned in simultaneous mixed-phase aerosol sampling, the BIA sam- above. The BIA, however, has concentrated on the following pling system PGP3, depletes the aerosol concentration.This three applications. can be explained by the relatively high volume flow of 3.5 L min-1 of this personal sampling system. The Millipore 2.3.1. Annular denuder. An annular denuder with a sampling head for inhalable dusts and a secondary filter holder has been cassettes with sorbent tubes were used under volume flows of 0.5 and 1.2 L min-1.The aerosol concentration obtained using developed. An application for sampling semi-volatile nitrosamines has so far been made available.8 these systems with lower volume flows was definitely higher. Table 1 Parallel sampling of metal working fluids in grinding processes Vapour+ Sampling combination Sampling rate/L min-1 Aerosol/mg m-3 Vapour/mg m-3 aerosol/mg m-3 Sampling of a water-mix metal working fluid Filter/charcoal Millipore 1.2 1.5 6.1 7.6 Filter/charcoal Millipore 0.5 4.3 3.2 7.5 Filter/XAD-2 GGP 3.5 0.6 7.2 7.8 Sampling of a mineral oil, flash point 172 °C Filter/charcoal Millipore 1.2 2.5 22.4 24.9 Filter/charcoal Millipore 0.5 6.6 18.0 24.6 Filter/XAD-2 GGP 3.5 <0.5 24.1 24.1 300 J.Environ. Monit., 1999, 1, 299–305The denuder is composed of five concentric glass tubes (Fig. 1). The tube surfaces were polished by sand blasters. The denuder can be operated under a volume flow of 8 Lmin-1. The inner surfaces have to be coated adequately. The particles are separated on the secondary filter. The intake complies with the requirements for inhalable dusts and is also supposed to ensure a laminar flow. These conditions allow a diVusion-controlled separation on the inner surfaces of the denuder.The denuder can be combined with the sampling system PGP. 2.3.2. Sampling system PGP. The sampling system PGP has been deliberately designed to allow the combination of the GSP (gesamtstaub-probenahme=inhalable dust sampling) sampling head with a vapour sampling system.3 The so-called GGP combination (gesamtstaub-gas-probenahme=inhalable dust/gas sampling), composed of a filter and a secondary sorbent tube, was developed. Initially, the only possible combination applied to a volume flow of 3.5 L min-1, implying that Fig. 2 GSP sampling heads for 0.5, 1.0, 3.5 and 10 L min-1 air flows. sorbent tubes had to be filled with suitable sorbents. This combination has proven successful for the sampling of mineral at the same time. Since no flow control has been placed oils.The experience gained with some substances, however, between the tubes, they can only be evaluated simultaneously. showed that a volume flow of 3.5 L min-1 led to a break- In cases where all three tubes are not used, the unused tubes through after a short sampling period. Consequently, the have to be shut by an unopened tube.The sorbent tube can system was further developed by inventing sampling heads for be squeezed into the seal and fastened by carefully tightening volume flows of 1 and 0.5 L min-1. the screws. The silicone insets have to be changed from time The innovative features of these combinations are the sam- to time (Fig. 3). pling heads for diVerent volume flows and the fixing for commercially available sorbent tubes. 2.3.3.Reagent-impregnated system in GSP. The sampling Our tests have shown that, by modifications, the sampling head GSP is fitted with a filter that is impregnated with a head will comply with the requirements for inhalable dusts in reagent. Sampling heads for volume flows of 3.5, 1.0 and the case of other volume flows.These modifications basically 0.5 L min-1 can be used. concern the size of the intake. Heads for volume flows of 10, 3.5, 1.0 and 0.5 L min-1 are already available, while the 3. Examples of combined vapour–aerosol sampling 10 L min-1 head was exclusively developed for particle sam- The following examples describe how mixed-phase aerosols pling (Fig. 2). are collected and analysed.It has to be considered, however, The new fixing for sorbent tubes can be adapted to every that under certain analytical conditions it may be advisable to type of tube by simply changing the plastic male fitting. There carry out combined vapour–aerosol sampling. The measure- is a whole variety of diVerently dimensioned tubes on the ment methods were developed in strict accordance with EN market.They are all compatible with the system. The tapering 481 and EN 482. The presented methods meet all requirements. seal is made of silicone. One to three tubes can be admitted 3.1. Inorganic acids In the technological field, the inorganic acids hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid are used in Fig. 3 New GGP combination (GGP-U 1.0) for sampling aerosol– Fig. 1 Annular denuder with sampling head for inhalable aerosols. vapour mixtures with commercially available sampling tubes. J. Environ. Monit., 1999, 1, 299–305 301Table 2 Physical properties and limit values of inorganic acidsa Hydrochloric acid Nitric acid Phosphoric acid Sulfuric acid Molecular mass/g mol-1 36.5 63.0 98.0 98.1 Melting point/°C -114.8 -42 42.4 10.4 Boiling point/°C -84.9 83 213 (-0.5 H2O) 338 Limit value (D) [mg m-3] 8 (CLV) 5 (CLV) No LV 1 E (CLV) [ppm] 5 (CLV) 2 (CLV) Limit value (S) [mg m-3] 8(CLV) 5 1 1 [ppm] 5 (CLV) 2 Limit value (DK) [mg m-3] 7(CLV) 5 1 1 [ppm] 5 (CLV) 2 Limit value (USA-ACGIH) [mg m-3] 7 (STEL/C) 5 1 1 [ppm] 5 (STEL/C) 2 aE, inhalable dust; STEL/C, short-term exposure limit/ceiling; CLV, ceiling limit value; D, Germany; S, Sweden; DK, Denmark.a whole variety of situations. It is quite common for several 0.5 L min-1 has proven to be adequate in this case. Two aligned silica gel tubes have to be used with the universal acids to occur simultaneously. When metal surfaces are coated in galvanic enterprises, fertilisers are manufactured or acids GGP. Acids are usually analysed by ion chromatography. This method is widely used in water chemistry and has become undergo orgic synthesis, e.g.nitrating acid, two or more acids are used at the same time. the standard method for analysing inorganic anions. A clear separation of all the occurring acids takes less than 15 min.9 The physical properties of acids, however, diverge greatly. While sulfuric acid and phosphoric acid always occur as The problem of blank values plays a special role in the context of this determination.Chlorides, in particular, are aerosols, hydrochloric and nitric acids usually occur in the working atmosphere as vapours. A common feature is their contained in numerous materials, so that an ongoing and careful control of blank values is indispensable.All receptacles, highly caustic and thus irritating eVect on the airways. In this context, it is important to note that, in Germany, the aerosol solutions and materials must be examined. This even includes the silica gel that was purified especially for this purpose. fraction that has to be collected is specified for all substances occurring in a particle form. As far as sulfuric acid is con- Teflon filters are the only non-problematic material.Another problem when sampling acids is caused by ubiqui- cerned, for example, the fraction that has to be collected is the inhalable one (Table 2). tously occurring chlorides, sulfates, nitrates or phosphates, because a distinction cannot be made through analysis. A combination of a filter and a secondary sorbent tube is used for the sampling of acids (Table 3).Teflon has proven DiVerentiation is only possible for hydrochloric acid and nitric acid, since these substances occur in the vapour phase, while the to be a suitable filter material. It is inert and the blank test shows more or less no numerical result. An especially purified salts occur in particle form. This diVerentiation does, however, not apply to sulfuric acid and phosphoric acid, so that the silica gel is used to absorb the vapours.A volume flow of measuring results always contain the ubiquitous salts as well. The measuring procedure has been conceived as flexibly as Table 3 Inorganic acids—measurement conditions possible. In working environments where acids only occur in Sampling particle form, the sorbent tube can be omitted and the volume GGP-U 0.5 0.45 mm Teflon filter/ORBO 53 silica gel tube flow can be raised to 1.0 L min-1.If no acids in particle form Flow rate 0.5 L min-1 are expected, the filter samples do not have to be analysed. In Sampling time 2 h this case, the filters are exclusively intended to collect ubiqui- Sample preparation tous salts. Filter 10 mL solution of NaHCO3 (0.0003 M)/Na2CO3 Measurements were conducted at all workplaces with expo- (0.0027 M) sure to inorganic acids.Silica gel 10 mL solution of NaHCO3 (0.0003 M)/Na2CO3 The limit value for sulfuric acid was shown to be exceeded (0.0027 M) Treatment 10 min ultrasonic bath, in two industries: lead accumulator manufacturing and electro- filtration Teflon filter (0.45 mm) plating. Excess concentrations were generally found to be only slightly above the limit value (cmax=1.2 mg m-3).Ion chromatography Injection volume 50 mL Concentrations of hydrochloric acids in chemical fibre pro- Column IonPac AS12A (Dionex) duction, however, achieved values up to twice the limit value. Mobile phase NaHCO3 (0.0003 M)/Na2CO3 (0.0027 M) Pickling plants (special steel ) and electroplating plants are Flow rate 1.5 mL min-1 workplaces where the limit value of nitric acid is frequently Detection Conductivity (chemical suppression) exceeded (five times the limit value).Reliability of the method Atmospheric workplace concentrations in other industries Detection limit HCl, HNO3 : 0.05 mg m-3 were generally in compliance with the relevant limit values.H3PO4: H2SO4 0.08 mg m-3 Precision HCl: 5–16% (blind value) HNO3 6–8% 3.2. Alkanolamines H3PO4 5–10% The alkanolamines 2-aminoethanol (ethanolamine, MEA), H2SO4 4–11% Recovery >95% diethanolamine (DEA) and triethanolamine (TEA) are used in Range 0.1–2.0 LV industrial technology in numerous areas. Technical soaps based Storage 4 weeks on alkanolamines are characterised by a lowlevel of alkalescence, Specificity High (interferences of ubiquitous salts) a high emulsifying eVect and solubility in organic solvents.These Remarks Blind values—control of all materials soaps are used as impregnating compounds for textiles, wood 302 J. Environ. Monit., 1999, 1, 299–305Table 4 Physical properties and limit values of alkanolaminesa 2-Aminoethanol Diethanolamine Triethanolamine Molecular mass/g mol-1 61.09 105.14 149.2 Melting point/°C 10.3 28 21 Boiling point/°C 170.58 271 277 (370 hPa) Vapour pressure/hPa 0.320 b <0.01320; 6138 b 2.7100 b Limit value (D) [mg m-3] 5.1 (CLV) 15 E 5 E [ppm] 2 (CLV) Limit value (S) [mg m-3] 8 15 5 [ppm] 3 3 Limit value (DK) [mg m-3] 2.5 2 3.1 [ppm] 1 0.46 0.5 Limit value (USA-ACGIH) [mg m-3] 8 2.5 5 [ppm] 3 aE, inhalable dust; CLV, ceiling limit value; D, Germany; S, Sweden; DK, Denmark.b0.320, vapour pressure at 20 °C. and leather, as well as in colouring vehicles, cleaning materials, diVerent countries. MEA only occurs in the vapour phase, whereas TEA solely occurs in particle form. DEA may occur medical soaps and creams. In water-miscible cooling lubricants, alkanolamines are either used freely as a protection against either as a vapour or as an aerosol depending on the sampling; it is thus a typical representative of a semi-volatile organic corrosion or in the form of fatty acid amides as compounds of emulsifying agents.In Germany, the use of DEA is prohibited, substance (Table 4). Samples of alkanolamines are taken by use of a glass fibre since this substance can easily be converted, as a secondary amine, into carcinogenic N-nitrosamines.filter impregnated with phosphoric acid. The amines are thus collected as ammonium salts. The glass fibre filter is impreg- Amines have a local caustic eVect on the skin, the eyes and the mucous membranes. nated by soaking it entirely in 0.1M phosphoric acid and sodium octanesulfonate, leaving it overnight to dry at room Amines are produced by transforming ethylene oxide with ammonia.All three amines are produced at the same time. temperature (Table 5). The dried filter is then fitted in the GSP and sampling is performed under a volume flow of The purification is performed by distillation. Industry mainly uses technically, less pure amines. In the majority of cases 0.5 L min-1.This low volume flow must be observed in order to avoid overcharging the filter. where these amines are used in industrial technology, it can be assumed that they occur simultaneously in the working The filter must be eluted immediately after the sampling procedure to anticipate a possible loss of MEA and DEA. environment. Mixtures are also quite frequently used.10 The physical properties of amines diverge greatly, in particu- Tests have shown that the loss of MEA within 24 h may reach up to 30% and up to 10% for DEA if immediate stabilisation lar as far as their volatility is concerned. The volatility was taken into consideration when limit values were fixed in of the sample in a solution is not ensured.The concentrated solvent agent used in ion pair chromatography serves as elution substance.The final ion pair chromatography is quite Table 5 Alkanolamines—measurement conditions simple and allows rapid separation of the alkanolamines.11 Sampling Measurements were carried out in the metal working indus- GSP 0.5 Glass fibre filter, impregnated with H3PO4 try in cases where cooling lubricants were used, as well as in (0.1 M)/C8H17SO3Na (0.02 M) the chemical industry for the manufacturing and further Flow rate 0.5 L min-1 processing of alkanolamines.While the results in the metal Sampling time 2 h working industry were clearly below the occupational exposure Filter Immediately after sampling: filter stabilisation (10 mL desorption solution) limit values, the concentrations found in the manufacturing and further processing of pure alkanolamines sometimes Sample preparation reached twice the limit value.Filter 10 mL solution of H3PO4 (0.005 M)/ C8H17SO3Na (0.001 M) Treatment 15 min ultrasonic bath, filtration Teflon filter 3.3. Explosives (0.45 mm) The last example involves the measuring procedure for the Ion chromatography explosives dinitrotoluene (DNT) and trinitrotoluene (TNT). Injection volume 50 mL Column Nucleosil 100–5C18 , L 125 mm, id 4 mm These explosives are still manufactured and used in large Mobile phase H3PO4 (0.005 M)/C8H17SO3Na (0.001 M) quantities, especially as military explosives or admixtures to Flow rate 1.0 mL min-1 commercial explosives for tunnelling or mines.In Germany, Detection Conductivity (electronic suppression) there is the additional problem of numerous military sites Reliability of the method dating from the Second World War or those of the former Detection limit MEA: 0.17 mg m-3 Russian army which await redevelopment.The soil and DEA, TEA: 0.33 mg m-3 groundwater of these sites are often highly contaminated by Recovery >90% explosives. During the redevelopment of soil, the upper layer Precision MEA: 1.5–3% of the soil is removed, cleaned and finally refilled.Germany DEA: 1.5–3% TEA: 1.5–4% must also deal with the huge ammunition pools of the former Range 0.1–2.0 LV Eastern German and Russian armies. The workers who will Storage 2 weeks (after stabilisation) be involved in these activities are likely to be exposed to large Specificity High quantities of explosives, while the type of exposure varies Remarks Sterile water is recommended considerably.J. Environ. Monit., 1999, 1, 299–305 303Table 6 Physical properties and limit values of explosivesa Dinitrotoluene 2,4,6-Trinitrotoluene Molecular mass/g mol-1 182.1 227.1 Melting point/°C 70 (2,4-DNT); 55–77 (technical mixture) 81 Boiling point/°C 319 (2,4-DNT, decomp.) 212 (16 h Pa) 287 (2,6-DNT, decomp.) Vapour pressure20 b/Pa 0.0113 (2,4-DNT) 0.74×10-3 0.031 (2,6-DNT) (0.05781) Limit value (D) [mg m-3] 0.05 (2,6-DNT) 0.1 1.5 (3,4-DNT) Limit value (S) [mg m-3] 0.15 (mixture) 0.1 Limit value (DK) [mg m-3] 0.15 (2,4-DNT) 0.1 0.15 (2,6-DNT) 0.15 (mixture) Limit value (USA-ACGIH) [mg m-3] 0.2 (mixture) 0.1 aD, Germany; S, Sweden; DK, Denmark.bVapour pressure20, vapour pressure at 20 °C.(i) In the manufacturing of military blasting charges, the DNT. Since the distribution of the substance in the soil is very heterogeneous, it is diYcult to predictwhere emissions will occur. propelling charge or the blasting charge is usually filled into the blasting cap when the material is liquid and hot. In such The requirements concerning the measuring procedure are quite diverse because of the diVerent possible uses.In order working environments, the explosives TNT and DNT normally occur as vapour or, less commonly, as a fume. to ensure the collection of all explosives, a combined vapour– aerosol sampling procedure had to be developed. Another (ii) When military blasting charges are being disposed of, the individual components (propelling charge, blasting charge diYculty that had to be tackled was the extremely low limit values applying in some of these cases (Table 6).Moreover, and ignition head for example) are manually separated and continuously burnt in small quantities. During the course of the measuring procedure had to be universally applicable, because a whole variety of explosives other than nitrotoluenes, this activity, the workers are sometimes exposed to high aerosol concentrations.with their own limit values, occur in all working environments [examples: tetryl, RDX (hexogen), HMX (octogen), picric (iii) During the redevelopment of former explosive factories, the removal of the upper soil layers may lead to high concen- acid ]. The procedure had to include the option of measuring these substances as well.trations of explosives contained in the dusts produced. Depending on the general conditions, these explosivesmay partly Finally, a combination of a quartz fibre filter and tenax tubes with a volume flow of 1 L min-1 proved to be suitable evaporate, especially in the summer and when the soil contains for sampling (Table 7). Stabilisation of the filter immediately after sampling is required to anticipate a possible loss of Table 7 Explosives—measurement conditions collected aerosol.An HPLC procedure was developed as an analysing method. Although presenting less indicative results, Sampling this procedure has the advantage of analysing nearly all GGP-U 1.0 Quartz fibre filter/tenax tube explosives simultaneously (Fig. 4). Flow rate 1.0 L min-1 Sampling time 2 h Remarks Immediately after sampling: filter stabilisation (4 mL methanol ) Sample preparation Filter 4 mL methanol Tenax 2 mL methanol Treatment 15 min ultrasonic bath Filtration Teflon filter (0.45 mm) Ion chromatography Injection volume 5 mL Column Hypersil-ODS, L 250 mm, id 2 mm Mobile phase Methanol/water 30/70 v/v Flow rate 0.2 mL min-1 Detection UV/VIS: TNT 230 nm, DNT 203 nm Reliability of the method Detection limit TNT: 0.007 mg m-3 2,4- and 2,6-DNT: 0.005 mg m-3 Precision TNT: 1.5–3% 2,4-DNT: 2–4% 2,6-DNT: 2–3.5% Recovery TNT: (95–80%) Fig. 4 Separation of explosives: HMX, octahydro- 2,4- and 2,6-DNT: >90% 1,3,5,7-tetranitro-1,3,5,7-tetrazoan; RDX, hexahydro-1,3,5-trinitro- Range 0.1–2.0 LV 1,3,5-triazin; Tetryl, N-methyl-N-2,4,6-tetranitroanilin; column, Storage 2 weeks (after stabilisation) Hypersil-ODS (250 mm), id 2 mm, particular size 3 mm; mobile Specificity High phase, methanol/water 30/70 v/v; flow rate, 0.2 mL min-1; tempera- Remarks Recovery of TNT varies with air humidity ture, 40 °C, injection volume, 5 mL; concentrations, TNT (decrease rel.humidity >40%) 0.75 mg mL-1, all others 1.25 mg mL-1. 304 J. Environ. Monit., 1999, 1, 299–305The measurements show the expected results. During the References course of hot processing, mainly vapours were determined; 1 NIOSH Manual of Analytical Methods, Polycyclic Aromatic TNT was detected and the concentration sometimes reached Hydrocarbons, Total (PACs), No. 5800, NIOSH publications, five times the limit value.The disposal of ammunition basically Cincinnati, 4th edn., 1998. required the determination of high aerosol concentrations for 2 CEN/TC137/WG3/N217, Workplace Atmospheres— TNT, sometimes up to ten times the limit value, and low Measurement of Chemical Agents Present as Mixtures of Airborne concentrations of DNT vapours. In the areas linked to the Particles and Vapour—Requirements and Test Methods, draft 1998. 3 H. Siekmann, H. Blome and W. Heisig, Staub–Reinhalt. Luft, redevelopment of soil, only traces of DNT vapours were found. 1988, 48, 89. 4 EN 482, Workplace Atmosphere—General Requirements for the Performance of Procedures for the Measurement of Chemical 4. Conclusion Agents, European Committee for Standardization, Brussels, 1994. 5 EN 481, Workplace Atmosphere—Size Fraction Definitions for The experience regarding the sampling of substances that Measurement of Airborne Particles, European Committee for occur in the vapour and aerosol phase can be summed up by Standardization, Brussels, 1993. 6 EN 1076, Workplace Atmosphere—Pumped Sorbent Tubes for the the following principles. determination of Gases and Vapours: Requirements and Test (i) The only indicative statement that can be made for Methods, European Committee for Standardization, Brussels, mixed-phase aerosols concerns their total quantity. 1997. (ii) The aerosol–vapour distribution depends considerably 7 EN 1232, Workplace Atmosphere—Pumps for Personal Sampling on the sampling conditions. of Chemical Agents: Requirements and Test Methods, European (iii) The storage and transport of collected aerosols have Committee for Standardization, Brussels, 1997. 8 B.Ha� ger and D. Breuer, GefahrstoVe–Reinhalt. Luft, 1997, 57, proven to be particularly critical, as the vapour pressure of 143. aerosols is not negligible. Therefore, immediate stabilisation 9 Flu� chtige Anorganische Sa�uren and Partikula�re Anorganische of the samples seems to be indicated. Sa�uren, in Analytische Methoden zur Pru�fung gesundheitsscha�d- When developing measuring procedures for mixed-phase licher ArbeitsstoVe–Wiley-VCH, Weinheim, 11th aerosols, particular attention has to be paid to the environmen- edn., 1998. tal conditions. 10 Ethanolamines and propanolamines, in Ullmann’s Encyclopedia of Industrial Chemistry, electronic release, Wiley-VCH, Weinheim, It is quite simple to combine filter sampling with secondary 1998, 6th edn. sorbent tubes. The same applies to impregnated sampling 11 W. Maurer, P. Nu�nnerich, E. Hohaus, B. Schleser and D. Breuer, media. These combinations have the advantage that the experi- Staub–Reinhalt. Luft, 1994, 54, 239. ence gained with the individual sampling media can be drawn upon. The ‘only’ requirement for such combinations are the additional tests to be carried out for the complete system. Paper 9/02081K J. Environ. Monit., 1999, 1, 299–305 3