Method and apparatus for analyzing volatile chemical components in a liquid

A sample of a volatile chemical component-containing liquid is segmented in stream flow with a gas with the volatile components partitioning or separating into the two phases, the gas then being separated from the stream and the volatile components therein analyzed for identification and concentration.

TECHNICAL FIELD 
The invention relates to improvements in methods and apparatus for the 
partitioning of volatile chemical components between liquid and gaseous 
phases with ultimate separation of the phases and analysis thereof. 
BACKGROUND OF THE INVENTION 
Various procedures have been developed to identify volatile components and 
concentrations thereof in a flowing stream. Such procedures include the 
combining of a liquid with a gas containing the components to be 
identified, inducing a reaction product, and separating such product 
through dialysis. It also has been proposed to react the resultant product 
to form a colored product to permit analysis thereof by means of a 
colorimeter. Additional procedures involve purge and trap analysis which 
is relatively slow and somewhat complicated. For example, purge and trap 
analysis frequently requires as much as 45 minutes to one hour to 
complete. 
Head space analysis, although not being an on-line technique, is used 
extensively. This form of analysis is generally accomplished by partially 
filling a sealed vial with the liquid sample, placing the vial in a 
temperature controlled environment to permit the volatile components to 
come to equilibrium with the air or gas in the head space of the vial, and 
then sampling the head space gas and injecting the sample into a gas 
chromatograph to identify the volatile components and determine their 
concentrations. 
Flow-through purge vessels combined with a gas chromatograph or hydrocarbon 
analyzer have been used for on-line analysis of volatile chemicals in 
water. In this technique, slow response to excursions is a major 
disadvantage and arises from the fact that the vessel acts as a dilution 
flask requiring a resulting high humidity stream to be taken continuously 
to the analyzer. 
Still another procedure consists of a combined armored silicone hollow 
fiber and gas chromatograph for the analysis of volatile chemicals in 
aqueous solutions. Such a system can be used for trace environmental 
monitoring. Among the disadvantages of this type of system is that 
cryotrapping is required to reach low detection limits and the silicone 
fiber may accumulate higher boiling chemicals which are not readily swept 
away into the vapor stream. 
The known procedures do not readily adapt themselves to on-line 
determination of the identity and concentration of volatile chemical 
components in water such as process aqueous streams, scrubber solutions, 
sewer legs to treatment plants, agricultural fumigant distribution 
systems, or the like because of complexity and excessive cycle time. There 
is a distinct need for an improved method and apparatus for determination 
of such volatile compounds and their concentrations, such method and 
apparatus being particularly adapted for use in environmental services, as 
in the testing of waste water and/or the determination of distribution of 
volatile soil fumigants in irrigation water. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a method of 
analyzing volatile compounds in a first fluid, the method including the 
steps of establishing a flowing stream of segments of the first fluid 
spaced by segments of other fluids, partitioning the volatile compounds 
into the other fluid segments from the first fluid segments, separating 
the other fluid segments from the first fluid segments, and analyzing the 
separated other segments to quantitatively analyze volatile compounds 
therein. 
The present invention further provides an apparatus for analyzing volatile 
compounds in the first fluid, the apparatus including partitioning means 
for establishing a flowing stream composed of segments of the first fluid 
spaced by segments of the second fluid which partition the volatile 
compounds into the second fluid from the first fluid, separating means for 
separating the segments of the second fluid from the stream, and analyzing 
means for analyzing the separated segments of the second fluid to identify 
volatile compounds therein. Means are provided for delivery of the 
separated segments of the second fluid to the analyzing means.

DETAILED DESCRIPTION 
In a broad sense, the invention relates to a method and apparatus for 
forming a segmented flow stream of at least two fluids, partitioning 
volatile compounds from one segment to the other, separating the fluid 
segments and analyzing the separated fluid segments. The partitioning 
fluid is chosen so as to be able to remove the compounds from the other, 
as well as being easily handled for quantitation of the compounds therein. 
For example, if the compounds are in a water sample, the partitioning 
fluid can be a gas which has an ability to partition the compound from the 
liquid and can be analyzed by gas chromatography. In one embodiment, the 
system involves sampling water by means of a peristaltic pump and mixing 
the water with air to form the segmented air/water stream. The segmented 
stream is passed through a concentric hollow fiber unit, or the 
equivalent, where the segmented stream is debubbled. The water is then 
sent to waste, whereas the gas collected in the concentric hollow fiber 
unit is dehumidified and sampled for analysis by gas chromatography. 
FIG. 1 illustrates a preferred form of the apparatus wherein a peristaltic 
pump 10 having dual heads 11 and 12 is connected to an air supply line 13 
and a liquid or water sample line 14. The pumping head 11 delivers air 
from any suitable source through line 13 to a connecting fitting 15, and 
the pumping head 12 delivers water from a source 16 through line 14 to 
connecting fitting 15. While the water source 16 is illustrated as a large 
bottle-type container with line 14 being submerged below the water level 
therein, any suitable source of liquid to be sampled may be utilized. For 
example, in an on-line application liquid supply line 14 may be connected 
to a pipe or other liquid conduit to obtain liquid samples directly 
therefrom. 
Air supply line 13 may be connected to any suitable gas component source, 
such as air, nitrogen, or the like, the gas utilized being capable of 
combining with volatile compound compounds so as to act as a fluid medium 
in the operation of the system. 
Fitting 15 produces a segmented stream in line 17 which is graphically 
illustrated as including a segmented stream flow consisting of alternating 
gas and liquid segments. The length of line 17 may be varied depending 
upon the equilibration time desired. Optimum length would be just long 
enough to allow equilibration. Minimal length better accommodates analysis 
of excursions. 
During the flow portion of the segmented stream substantial transfer of 
compound components from the liquid segments to the gaseous segments 
occurs, the primary gradient or driving force accomplishing such transfer 
comprising the volatility of the compound components. For example, the 
apparatus functions effectively with volatile compound components 
exhibiting boiling points of up to approximately 180.degree. C. Secondary 
gradients or driving forces exist, such as pumping pressure and sizing of 
stream flow lines. While equilibration is the theoretical goal, very 
substantial transfer will occur and such transfer very closely approaches 
equilibration. This type of transfer is also referred to as partitioning. 
Additionally, water vapor, which exhibits sufficient driving force, also 
will be transferred from the liquid segments to the gaseous segments and 
preferably subsequently removed. 
The apparatus of FIG. 1 includes a concentric fiber transfer and 
dehumidifying unit 18 which may be made from any suitable material, such 
as glass. In a broad sense, unit 18 functions as a separation chamber and 
includes an elongated, generally cylindrical body 19 having opposite end 
neck portions 20 and 21, neck portion 20 being the inlet end of unit 18 
and neck portion 21 defining one of the outlets of unit 18. Generally 
centrally of the unit 18, the body 19 is provided with an upstanding 
cylindrical column 22 within which is a generally concentric sampling 
column 23. Column 22 is sealed at its upper end by a removable cap 24 of 
any suitable kind which accommodates the upper end 25 of sampling column 
23, such upper end defining a septum port 26 of known type. The base of 
sampling column 23 includes an area of reduce diameter 27 terminating at 
its lower end in a cylindrical foot portion 28 provided with oppositely 
directed, cylindrical, open ends 29 and 30. 
Cylindrical end 29 receives telescopically therein the inner end of an 
outer cylindrical fiber segment 31, the outer end of which is sealed in 
neck portion 20. A second segment 32 of the outer cylindrical fiber 
segment 31 also has its inner end telescopically received in cylindrical 
end 30, its outer end being sealed in neck portion 21. An inner, 
continuous, cylindrical fiber 33 extends through neck portions 20 and 21, 
outer fiber segments 31 and 32, and cylindrical foot portion 28 of 
sampling column 23. One end of fiber 33 projects beyond neck portion 20 
and is attached to segmented stream line 17, the opposite end of fiber 33 
projecting outwardly of neck portion 21 for suitable attachment to a 
conduit or the like (not shown) to conduit water from the system and 
discharge it to waste. Unit 18 is completed with the provision of an 
access port 34 supplied with a removable cap 35 for the purpose of 
introducing and replacing desiccant in body 19 in substantially 
surrounding relation with outer cylindrical fiber segments 31 and 32. 
Septum port 26 is preferably connected to any suitable type of sampling 
valve 36 which in turn is connected to a gas chromatograph 37 to complete 
the system. 
The segmented air/water stream is delivered into and through inner 
continuous fiber 33 which is selected to permit transfer of gaseous 
material, including water vapor, therethrough thus functioning as a 
hydrophobic membrane. Gaseous material is collected within outer fiber 
segments 31 and 32 for sampling, and segments 31 and 32 are preferably 
selected to function as very selective hydrophilic membranes to permit 
transfer of water vapor into body 19 and into contact with the desiccant 
therein. In this manner, the volatile compound components of the original 
liquid stream are isolated for analysis and simultaneously dehumidified. 
Sampling valve 36 is operated periodically to withdraw air enriched with 
compound components from column 23 which, in turn, is in communication 
with the interior of outer fiber segments 31 and 32 via foot portion 28. 
Each sample taken is transmitted to a known type of gas chromatograph 37 
which analyzes each sample to identify and determine the concentration of 
the compound component content thereof. 
The apparatus described thus far is capable of on-line utilization. It also 
is adapted for use as a portable field testing system. For example, 
sampling valve 36 may be replaced in the field with a suitable probe or 
gas-tight syringe for use in conjunction with septum port 26 to obtain 
periodic samples for introduction into a portable gas chromatograph. 
Transfer unit 18 may include the use of a microporous 
polytetrafluoroethylene (TFE) tubing as its inner continuous fiber 33. 
While any suitable type of hydrophobic microporous membrane, such as 
polypropylene, may be used, in the following examples the TFE fiber tube 
33 is incorporated in the test equipment and is commercially identified as 
GORE-TEX by its manufacturer, Gore, Inc. The tube has an inner diameter of 
1 mm., 3.5 micromillimeter pores, and 70% porosity. This material is 
hydrophobic and compoundly inert. Its hydrophobicity, along with the high 
surface tension of water, creates a phenomenon whereby air and vapors can 
pass through the fiber's pores while aqueous solutions remain in the fiber 
bore. 
The use of outer fiber segments 31 and 32 is not essential, but some 
effective form of dehumidification is desirable. The fiber used to form 
these segments may be a perfluorosulfonic acid product, such as that sold 
under the DuPont trademark NAFION. The fiber segments were formed from 
810X tubing having an inner diameter of approximately 2.75 mm. and an 
outer diameter of approximately 3.125 mm. This perfluorosulfonic acid 
product provides a membrane with a high capacity and high selectivity for 
water vapor. It is also inert to volatile, halogenated compounds. 
The desiccant used to fill body 19 of unit 18 was standard indicating 
silica gel. 
Any suitable type of pump 10, such as the FMI Lab-Pump Jr., may also be 
used. 
Tests conducted using the apparatus thus far described included the use of 
either a portable micro-gas chromatograph equipped with a u-thermal 
conductivity detector or a standard type laboratory gas chromatograph 
equipped with an electron capture detector. A suitable microchip gas 
chromatography unit for field use is a Model M500 or P200D analyzer 
obtainable from Microsensor Technology, Inc., Freemont, California. A 
conventional laboratory style chromatograph may be a Model 5890 obtainable 
from Hewlett-Packard, Novi, Michigan. The column used with such a unit may 
have a length of 15 m. to 30 m. with an internal diameter of 0.1 mm to 
0.53 mm. DURA-BOND coating 1301 as well as others with a thickness of 0.4 
to 5 microns may be used. Such a column and coating are available from J & 
W Scientific, Folsom, California. 
To illustrate the feasibility of monitoring the distribution of volatile 
solid fumigants in irrigation water, a water sample containing 100 
micro-grams per milliliter, of TELONE C-17 (a trademark of Dow Chemical 
Co., Midland, Michigan), was formed into a segmented stream in the manner 
previously described in connection with the apparatus of FIG. 1. This 
TELONE C-17 sample contained approximately 40 .mu.g/ml 
t-1,3-dichloropropene, 35 .mu.g/ml c-1,3-dichloropropene, and 17 .mu.g/ml 
chloropicrin. The water sample was placed in container 16, pumped through 
line 14, and combined with air at fitting 15. The segmented stream was 
passed through inner fiber 33 and the air phase, now containing the 
volatile compound constituents, was transferred through the membrane 
defined by fiber 33 along with water vapor into the annular space 
surrounding inner fiber 33 and confined within outer fiber segments 31 and 
32. During movement through unit 18 by pump 10, the selective hydrophilic 
properties of outer membrane segments 31 and 32 transferred water vapor 
into contact with the desiccant within body 19 while selectively retaining 
the remaining air and compounds mixture, such mixture ultimately filling 
sampling column 23 and being available for sampling through septum port 
26. 
Instead of using the sampling valve 36, a known sampling probe forming a 
part of a micro gas-chromatograph of the type previously described was 
used to transfer a sample of approximately 5 ml. of the gaseous mixture to 
the chromatograph where small micron-liter portions of the gas was 
injected into the 0.1 mm. internal diameter capillary columns for 
analysis. The gas sample was analyzed on one or more of the internal 
miniaturized gas chromatograph modules, simultaneously. This type of 
instrument was used to analyze over 120 different compounds (gases/vapors) 
with typical analysis times in less than 60 seconds. Such a chromatograph 
may be operated in an automated sampling mode, automatically sampling and 
analyzing the vapors at pre-selected sampling intervals and storing the 
results for subsequent recall. Such a microgas chromatograph utilizes 
miniaturized thermal conductivity detectors with high sensitivity. 
The chromatographic columns used with the micro gas-chromatograph were 0.3 
to 4 m. long, and of 0.1 mm. inner diameter. The capillary columns were 
coated with DURA-BOND 1701 phase at a thickness of 0.1 to 0.5 microns. The 
carrier gas utilized in the chromatograph was helium traveling at 
approximately 100 cm/sec. 
The results of the TELONE C-17 analysis are shown in FIG. 5 in the form of 
a chromatogram combined with a list of compounds and concentrations 
thereof identified by the chromatogram. In the typical chromatogram shown 
in FIG. 5, the ordinate denotes quantitative detection and the abscissa 
measures time of detection, or as is more commonly referred to, time of 
retention. Time of retention or identification of the constituents of the 
tricompound material took no more than a total of seven seconds and 
quantitative detection accurately confirmed known concentrations of the 
compound constituents. 
Additional tests were conducted not only to confirm the quantitative 
accuracy of the subject method and apparatus, but also to explore the 
speed of detection response in more complex systems. Such tests involved 
use of different combinations of volatile compounds in varying numbers and 
concentrations in water, the concentrations ranging from 4 to 1000 ng/ml. 
A typical test involved a water sample containing 24 volatile halogenated 
compounds, the results of which are shown in FIG. 6 consisting of a 
chromatogram combined with a list of the compound compounds detected, 
their respective concentrations and retention times. In tests such as that 
of FIG. 6, the laboratory gas chromatograph described above was utilized. 
Samples in quantities of 1 ml. were withdrawn from the apparatus of FIG. 1 
through septum port 26 using a sampling probe. 
The test results of FIG. 6 further illustrate the speed of detection of the 
subject method and apparatus thus permitting effective use thereof in a 
rather complex compound system. Of particular importance, the method and 
apparatus exhibit the desirable capability to detect concentrations 
including temporary excursions. 
The various tests conducted established that certain standards can be 
determined for each volatile compound compound of the type reasonably 
expected to be encountered in environmental monitoring of waste water, 
irrigation water and the like. It has been found that the detection 
sensitivity of the subject method and apparatus for an array of volatile 
compound compounds can be expressed in the form of enrichment factors with 
a single such factor being unchangeably assignable to each compound 
compound subject to detection. That is, each enrichment factor is a direct 
measure of the detection capabilities of the method and apparatus with 
respect to a specific volatile compound compound. The following table 
illustrates this discovery with respect to 22 volatile compound compounds: 
TABLE 
______________________________________ 
LOD 
in air EF LOQ 
(ppb - (air/ in water 
COMPOUND v/v) water (ng/ml) 
______________________________________ 
METHYL CHLORIDE 330 48 23 
METHYL BROMIDE.sup.(a) 
137 76 6.0 
VINYLIDENE CHLORIDE 6.8 12 1.9 
METHYLENE CHLORIDE 22 8.2 9.2 
t-1,2-DICHLOROETHYLENE 
200 16 42 
1,1-DICHLOROETHANE 270 6.7 130 
CHLOROFORM.sup.(b) 2.7 6.6 1.4 
1,1,-TRICHLOROETHANE 
2.5 6.8 1.2 
CARBON TETRACHLORIDE 
0.54 7.7 0.23 
1,2-DICHLOROETHANE 76 6.8 37 
TRICHLOROETHYLENE 2.8 9.9 0.94 
1,2-DICHLOROPROPANE 120 7.7 54 
BROMODICHLOROMETHANE 
3.0 7.7 1.2 
t-1,3-DICHLOROPROPENE 
26 7.2 12 
c-1,3 DICHLOROPROPENE 
30 3.6 28 
1,1,2-TRICHLOROETHANE 
15 3.9 13 
PERCHLOROETHYLENE 0.69 4.8 0.48 
CHLORODIBROMOMETHANE 
4.6 3.7 4.2 
CHLOROBENZENE 310 4.0 260 
BROMOFORM 9.4 2.0 16 
1,1,2,2-TETRACHLOROETHANE 
10 2.0 17 
1,2-DICHLOROBENZENE 90 1.7 170 
______________________________________ 
.sup.(a) ETHYL CHLORIDE is not included because it coelutes with METHYL 
BROMIDE 
.sup.(b) BROMOCHLOROMETHANE coelutes with CHLOROFORM. 
The foregoing table includes for each compound listed a measured detection 
limit in air (LOD), an extrapolated quantitation limit in water (LOQ), and 
a calculated enrichment factor (EF). Both the detection limit in air and 
quantitation limit in water will vary depending on the sensitivity of the 
analytical equipment used. Thus, at any given testing site the sensitivity 
of the particular gas chromatograph used will determine detection and 
quantitation limits. 
By way of example, the results of the subject tests listed in the foregoing 
table involved the use of the laboratory gas chromatograph identified 
above. With such an instrument, the LOD values are measurable at three 
times the signal-to-noise ratio. Since the actual analysis of the volatile 
compounds in the water samples involves measurement in the vapor phase, 
the LOD values establish the limits of sensitivity or detection for the 
instrument. 
Without benefit of known enrichment factor for each compound compound 
present, extrapolation of the quantitation limit (LOQ) for each compound 
was accomplished by multiplying the signal-to-noise ratio of the test 
instrument by ten. These quantitation limits are a reflection of both the 
detector sensitivity (LOD) and what can be referred to as the enrichment 
factor or magnification of the concentration into the air phase. Thus, an 
enrichment factor was calculated for each compound as follows: 
##EQU1## 
The enrichment factor depends on the volatility, water solubility, and 
diffusion coefficient of the particular compound. This factor has been, 
established to illustrate the measurement sensitivity of the compound 
which is usually enhanced by the use of the method and apparatus of the 
subject invention. Once the enrichment factor is determined for a given 
compound, a helpful constant which is independent of the type of detector 
used is provided to determine quickly and accurately quantitation limits 
in a water sample using the foregoing equation modified as follows: 
##EQU2## 
Enrichment factors may be relied upon to establish a range useful in 
identifying volatile compound compounds subject to detection and 
quantitation in a fluid medium such as water. The table set forth above 
establishes a range from 1.7 to 76 while interpretation of additional test 
results and consideration of properties of known compounds establishes a 
practical range of from 1 to 100. The more volatile and less water soluble 
compounds exhibit the higher enrichment factors. 
It has been found that equilibration for an upward change in concentration 
can be 90 to 100 per cent complete in approximately 10 to 15 minutes. This 
means that a shot or excursion concentration could be detected on the very 
next analysis. Cycle time with the laboratory gas chromatograph has been 
found to average approximately 12 minutes. This is a substantial 
improvement as compared to conventional purge and trap analysis which can 
require as much as 45 minutes to one hour per cycle. 
It has been found that the method and apparatus of the present invention 
permit full utilization of a wide range of concentrations of compounds, 
from low values in sub-parts per billion to substantial values in high 
parts per million. No supplemental sorbent trapping is necessary. 
The use of concentric hollow fibers in the manner described provides for 
increased component transfer area in a minimum of space. The primary 
driving force or gradient comprises essentially the volatility of the 
compound compounds in the waste water causing ready enrichment of the air 
segments. Transfer is also assisted by pressurized flow provided by pump 
10. The water, in effect, is debubbled. The desiccant located externally 
of fiber segments 31 and 32 provides a gradient or driving force assisting 
in transfer of water vapor through the membranes provided by the fibers. 
The precision deviation for repetitive analyses in water has been found to 
range from about 0.35% to 17%, averaging approximately 6.5%. Based on 
extensive evaluation, it has been established that the subject invention 
consistently requires less than 15 minutes per analysis. 
While the type of concentric hollow fiber unit described is preferred, the 
outer tube segments 31 and 32 may be eliminated, although dehumidification 
in some suitable manner preferably should occur inasmuch as temperature 
changes can cause condensation to occur which can slow the process. Thus, 
dehumidification speeds transfer and efficiency of transfer in a direction 
toward equilibration. 
When utilizing membrane segments 31 and 32 for removal of water vapor from 
the air/compounds mixture, a concentration radient may be established by 
continuously purging the interior of body 19 with dry air, thus 
eliminating the need for a desiccant. 
The versatility of the present invention is further illustrated in the 
embodiments of FIG. 2-4. FIG. 2 discloses a portion of a modified system 
including in particular a modified gas transfer unit 40. For ease of 
construction this unit includes a glass body formed from a pair of 
cooperating body portions 41 and 42, portion 41 including a socket 43 
within which is a cooperating ball 44. Body portion 41 is provided with a 
closed neck end 45 through which extends an inner hollow fiber 46 through 
which a segmented stream of air/water may flow into unit 40 in the same 
manner as shown in FIG. 1. Hollow fiber 46 extends through the combined 
body portions 41 and 42 and outwardly beyond a closed neck end 47 at the 
opposite end of body portion 42 in communication with a suitable water 
disposal system (not shown). Body portion 41 includes an upstanding 
cylindrical column 48 provided with a removable closure 49 through which a 
cylindrical, upwardly extending gas sampling column 50 extends 
Column 50 is provided with a bottom transverse foot portion 51 receiving in 
telescoped relation in opposite ends thereof segments 52 and 53 of an 
outer hollow fiber, the remaining end of segment 52 being fixed in closed 
neck end 45. This telescopic arrangement is similar to that disclosed in 
FIG. 1. Column 50 includes at the top thereof a septum port 58 connected 
to a sampling valve 59 which in turn is connected to a known form of gas 
chromatograph 60. Column 50 further includes a transversely extending gas 
flow line 61 equipped with a stopcock 62 operable selectively to release 
air/compounds previously sampled into a suitable disposal system (not 
shown). Body portion 41 is further provided with an access port 63 
provided with a removable cap 64 to enable the supply and removal or 
replacement of desiccant surrounding fiber segments 52 and 53. 
Body portion 42 is similarly provided with an upstanding cylindrical column 
65 having a removable closure 66 through which an upstanding cylindrical 
column 67 extends. The inner bottom of column 67 is provided with a 
transverse foot portion 68 of the type previously described which 
telescopingly receives adjacent ends of outer fiber segments 53 and 69. 
The remaining end of segment 69 is sealed in closed neck end 47. Inner 
hollow fiber 46 extends continuously through the outer hollow fiber 
segments 52,53 and 69 as well as through the foot portions 51 and 68. The 
top outer portion of cylindrical column 67 projecting above closure 66 is 
provided with a stopcock 70 (diagrammatically shown) and beyond such 
stopcock communicates with an air supply line 71 which extends through the 
single head 72 of a peristaltic pump 73. 
The apparatus of FIG. 2 is illustrative of one form of flow-through purging 
system. Such a system is of significance in on-line operation particularly 
where excursions are expected and are to be detected. 
As referred to hereinabove, substantial equilibration for an upward change 
in concentration has been found to be 90 to 100% complete in approximately 
10 to 15 minutes for all of the compounds tested. With this rate of 
reaction efficiency, a shot or excursion concentration should be detected 
as it occurs. However, in some instances recovery to zero after a 
concentration excursion can be relatively slow, even as long as 60 
minutes. This is because dead volume exists inside the concentric hollow 
fiber unit. This, combined with a withdrawal of a small sample, e.g. 1 ml, 
for analysis, tends to cause stagnation thereby requiring a substantial 
amount of time to clear out the system for subsequent effective operation. 
In the apparatus of FIG. 2, pump 73 on demand supplies air to the interior 
of the outer hollow fiber segments, especially segment 53, such air 
forcibly clearing out any stagnant gases through column 50 past stopcock 
62. This allows rapid downward recovery in concentration as well as 
upwardly increased detection of excursions. Thus, even for a 7 second 
analysis of the type previously described, the stopcocks 62 and 70 may be 
operated quickly and effectively to purge the system prior to further 
sampling. The concentric fibers disclosed in FIG. 2 are of the same type 
as referred to in connection with FIG. 1 and operate in the same manner. 
FIG. 3 illustrates another form of equilibration apparatus including a 
stainless steel membrane cell 80 subdivided into a top cell 81 and a 
bottom cell 82 separated by a transverse membrane (not shown) which may be 
formed from microporous polypropylene film. Top cell 81 includes an inlet 
83 for segmented air and water of the nature described previously, and a 
water outlet 84 connected to waste or the like after passing through a 
back pressure valve 85 of known type. Bottom cell 82 is provided with an 
air inlet line 86 which passes through the single head 87 of a peristaltic 
pump 88. Bottom cell 82 also includes an air outlet line 89 that is 
connected to a sampling valve 90 which in turn is connected to a 
dehumidifier 91 and a gas ohromatograph 92. Membrane cell 80 may be a 
modified Amicon CECl on-line column eluate concentrator available from 
Amicon Corporation, Lexington, Massachusetts. 
It is also is possible to use a microporous membrane between the upper and 
lower cells such as that formed from CELGARD 2400 (trademark of Celanese 
Corporation, Charlotte, North Carolina) microporous polypropylene film. 
Such a film is about 38% porous and has a thickness of 1 mil. 
The system of FIG. 3 provides a continuous flow of a segmented air/water 
stream through top cell 81 across the membrane separating top cell 81 from 
bottom cell 82, while additionally providing a continuous flow of air 
through bottom cell 82. The membrane selectively transfers the air 
segments containing the volatile compounds as well as water vapor, such 
transferred components being picked up by the continuous air flow through 
bottom cell 82 with periodic samples being taken therefrom via sampling 
valve 90, the samples being dehumidified to remove water vapor and then 
subjected to analysis in gas chromatograph 92. In a continuous 
flow-through system of this type or a stop flow system, stagnation is 
avoided, excursions are readily determined, and the speed of analysis is 
high. 
FIG. 4 illustrates a simplified form of a sampling system further 
illustrating the versatility of the present invention. The system of FIG. 
4 includes a solvent debubbler 94 which is in the form of a translucent 
reservoir 95 provided with an airtight cap 96. The debubbler 94 may be 
obtained from Anspec Co. and has been used to remove bubbles from the pump 
inlet line of a high pressure liquid component system. Debubbler 94 
includes a base 97 receiving therein a section of hollow fiber 98 prepared 
from microporous TFE of the type previously described. One end of fiber 98 
is attached to a segmented air/water sample supply line 99 and the 
opposite end is attached to a waste water line 100. Fiber 98 is in 
communication with reservoir 95. 
A segmented stream of the type previously described is supplied via line 99 
through hollow fiber 98. In base 97 of debubbler 94, air mixed with 
volatile compounds transfers through fiber 98 into reservoir 95. A 
suitable form of sampling valve 101 may be attached to debubbler 94 
through cap 96 to receive periodic samples with each being transferred to 
dehumidifier 102 and then for analysis to gas chromatograph 103. Thus, a 
very basic, uncomplicated, and inexpensive volatile compounds transfer 
system may be fabricated. As previously described, the use of a 
dehumidifier in the systems of FIGS. 3 and 4 is not essential, but is 
preferred. 
Another, simplified embodiment of the present invention is shown in FIGS. 7 
and 8. Tubing 106, such as 1/4 inch Teflon tubing leads from a scrubber 
and carries water therein. The tubing 106 includes a T-portion 107, the 
flow therethrough being controlled by valves 108,110,112. Valves 108 and 
112 control the flow of water through tubing 106 to a drain (not shown) 
while valve 110 controls the flow of fluid to tube 114 which leads to the 
fluid pump 116. In the preferred embodiment, FMI lab pump Jr., model 
RHSYOCKC, was used. The pump 116 pumps the fluid from tubing 106 to the T 
member 118. This member 118 can be a 1/8 inch Teflon T disposed down 
stream of the pump 116. An air source 120 is connected through valve 122 
and pressure gage 124 to a Watts regulator 126 which controls flow to a 
needle valve 128. The needle valve 128 is in fluid communication through 
tubing 129 to the Teflon T 118. Tubing 129 can be in the form of a 1/8 
inch Teflon tube. Of course, the sizes of tubing depend upon volumes and 
rate of fluid being moved therethrough. The Teflon T 118 is in fluid 
communication with the air source and the water being supplied from the 
scrubber. The two are fed together through the Teflon T 118. The air may 
be fed into the system from plant air or from other sources as previously 
described. As discussed with previous embodiments, the Teflon T 118 
produces a segmented stream in line 130. The length of line 130 may be 
varied depending upon the equilibration time desired. Optimum length would 
be sufficiently long so as to allow equilibration. Minimal length better 
accommodates analysis of the excursions. 
The air/water segments flow through line 130 into the glass phase separator 
generally indicated at 132 and shown in greater detail in FIG. 8. While 
the air/water segments are flowing to the glass phase separator, the 
volatile compounds in the water partition into the air and reach 
equilibration concentrations dependent upon the length of line 130, as 
discussed above. 
The glass phase separator 132 is a substantially S-shaped member including 
a water drain trap portion 134. The water drain trap portion 134 leads to 
an overflow drain portion 136, the drain portion 136 leading to piping 
138. Piping 138 carries overflow water to a drain (not shown). The 
separator 132 includes a gas outlet 140. 
As shown in FIGS. 7 and 8, water 142 is allowed to collect in the trap 
portion 134 and then drain through the overflow portion 136 into drain 
pipe 138. Coincidently, the vapors of the volatiles that have been 
separated collect in a small head space volume 144 above the water 142. 
The vapors in the head space 144 exit the outlet 140 into a neck portion 
146 having an air outlet 148. The outlet 148 is necessary because of the 
flow of water into the system causing a slight positive pressure of air 
exiting the glass phase separator 132. This slight positive pressure 
allows for real time analysis of the concentrations of the volatile 
compounds in the water as the positive pressure continues to displace the 
volume in the head space 144 which is being sampled. That is, the positive 
pressure is continually forcing newly separated volatiles into the head 
space 144 which then travels through the neck portion 146. Sampling is 
conducted in the neck portion 146, the gas not being sampled exiting the 
neck portion through outlet 148. 
A needle valve 150 and tubing 152 interconnect the neck portion 146 in 
fluid communication with a microchip gas chromatograph 154 and lap top 
personal computer 156. The tubing 152 can be a 1/16 inch tubing. The 
needle valve 150 consists of a needle 158 and septum 160, the needle being 
disposed through the septum 160 and into the neck portion 146. The tubing 
152 is connected through an adaptor to a needle 158. 
The microgas chromatography system is preferably a Michromonitor P-200 
which is a compact, portable unit containing two miniaturized gas 
chromatography modules, an internal sampling pump, a lead-acid battery, 
and an internal, rechargeable carrier gas supply. The gas chromatograph 
modules, constructed using silicon micro machining techniques, incorporate 
a solid state injection system, a short, high speed analytical column, a 
column heater and temperature sensor, and a 20 nL volume thermal 
conductivity detector. This system is preferred because it is capable of 
very high separating efficiencies with typically 10 to 45 second analysis 
time. When the P-200 is used with a lap top computer and EZCHROM software 
package, the system forms an automated, flexible gas/vapor analysis and 
data logging system. Of course, other microchip gas chromatograph systems 
could be designed and used in accordance with the present invention. The 
system described above can be configured for use in a wide variety of 
applications for the determination of over 200 gases and vapors. The 
instrument is suitable for measuring concentrations from one part per 
million - v/v to 100%, with linear response over five orders of 
magnitudes. The concentrations measured in the vapors are related to the 
concentrations of the components in the water, based on partition ratios, 
which were determined based on lab analysis of water standards and samples 
at 21.degree. to 22.degree. C. For field use, a portable, air purged, 
temperature-controlled box is used. 
In operation, a vapor sample is drawn into the instrument through the 1/16 
inch tube 152 or sampling probe with an integral sampling pump and, then, 
simultaneously injected into the two GC modules for analysis with the 
optimum resolution and speed. The chromatograms are processed using the 
external lap top microcomputer, calculating the concentration results 
within internally stored response factors. 
The system was evaluated initially by being set up for the determination of 
twelve compound compounds, and separating the compounds of interest in 90 
seconds. The test compounds included: methyl chloride, 1,3-butadiene, 
ethyl chloride, methylene chloride, acrylonitrile, carbon tetrachloride, 
chloroform, benzene, 1,2-dichloroethane, toluene, tetrachloroethylene, and 
styrene. 
The present invention is especially useful for in situ monitoring of 
process vapors for environmental waste reduction projects, material 
balance investigations, and evaluation of emission control equipment. With 
typical analysis times of between 10 and 45 seconds, the system has 
already been useful for generating time-concentration profiles on 
batch-operated processes. When coupled with flow data-logging, detailed 
emission rate profiles or material balance data can be generated. 
The method of the present invention provides an uncomplicated but highly 
effective procedure for analyzing the volatile components of a liquid 
stream by partitioning such component into a gaseous phase during 
segmented gas/liquid flow and then separating the gaseous phase from the 
segmented flow following which the gaseous phase is analyzed to identify 
the volatile components and concentrations thereof. Additionally, the 
apparatus of the invention functions as a useful interface between a water 
stream and a gas chromatograph for the on-line identification of volatile 
components and concentrations thereof in water.