Patent Publication Number: US-2004043499-A1

Title: Dissolved carbon measurement

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates generally to chemical instruments that measure the carbon content of a sample. More specifically, the invention relates to chemical instruments that can be used to measure one or more components of total carbon dissolved in a liquid sample.  
       BACKGROUND OF THE INVENTION  
       [0002] The measurement of carbon content in liquids such as drinking water, treated or untreated wastewater, and ultrapure water for pharmaceutical or clean room applications is a routine way to assess the purity of the liquid sample. Solid or semi-solid specimens such as soils, clays, or sediments can likewise be measured for carbon content using known analyzer accessories.  
       [0003] Known analyzers have a wet chemistry section with multiple complex flow paths. These analyzers require the use of a number of valves in the flow paths that require maintenance. There is a desire to reduce the complexity of the flow paths, reduce the number of valves, and reduce maintenance requirements for a wet chemistry section of a dissolved carbon analysis instrument.  
       SUMMARY OF THE INVENTION  
       [0004] Disclosed is an analytical instrument for measuring dissolved carbon in a sample liquid. The instrument comprises a valve having valve inlets that receive the sample liquid, liquid water and a base liquid. The valve has a valve control input and at least a first valve outlet.  
       [0005] The instrument also comprises a syringe pump coupled to the valve. The syringe pump selectively pumps the liquids from the valve inlets to one or more valve outlets. The syringe pump includes a pump control input.  
       [0006] A sparger is included in the instrument. The sparger receives the sample liquid and a quantity of the base liquid from the first valve outlet. The sparger provides a gas flow to remove purgeable organic carbon POC gasses during a first time interval.  
       [0007] A chemical reactor receives the purgeable organic carbon POC gasses. The chemical reactor generates carbon dioxide during the first time interval.  
       [0008] A control interface couples a control actuation sequence to the valve control input and the pump control input. The carbon dioxide is coupled to an analyzer that couples to a controller that generates a first analyzer output. The first analyzer output represents a concentration of dissolved purgeable organic carbon POC in the sample liquid. The controller also provides the control actuation sequence.  
       [0009] These and various other features as well as advantages that characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010]FIG. 1 illustrates a PRIOR ART liquid sample carbon analyzer arrangement.  
     [0011]FIG. 2 schematically illustrates details of the PRIOR ART liquid sample carbon analyzer illustrated in FIG. 1.  
     [0012]FIG. 3 illustrates a block diagram of a first embodiment of a liquid sample carbon analytical instrument.  
     [0013]FIG. 4 illustrates a block diagram of a second embodiment of a liquid sample carbon analytical instrument.  
     [0014]FIG. 5 illustrates a timing diagram of control actuations during purgeable organic carbon POC analysis.  
     [0015]FIG. 6 illustrates a timing diagram of control actuations during inorganic carbon IC analysis.  
     [0016]FIG. 7 illustrates a timing diagram of control actuations during non-purgeable organic carbon NPOC analysis.  
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS  
     [0017]FIG. 1 illustrates a PRIOR ART liquid sample carbon analyzer arrangement  10 . The arrangement  10  includes a non-dispersive infrared NDIR gas analyzer  12 , a wet chemistry section  14  and a computer  16 . An example of the internal operation of the wet chemistry section  14  can be found in U.S. Pat. No. 6,007,777 Purcell et al., which is hereby incorporated herein by reference.  
     [0018]FIG. 2 schematically illustrates details of the wet chemistry section  14  illustrated in FIG. 1. The wet chemistry section  14  includes a valve  16 , a syringe pump  18 , a sparger  20 , a UV reactor  22 , a gas-liquid separator  24 , a mist trap  26 , a nafion tube  28  and a halogen scrubber  30 . The components  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  are interconnected by a number of tubes  32  and valves  34  (hidden from view behind mounting plate  36 ) generally as set forth in U.S. Pat. No. 6,007,777 Purcell et al. The valves and tubes require maintenance. There is a desire to reduce the complexity of the flow path and maintenance requirements for a wet chemistry section. As described below in connection with FIGS.  3 - 7 , a wet chemistry section is provided that has a reduced number of valves and a simplified flow path for carrier gas.  
     [0019]FIG. 3 illustrates a block diagram of a first embodiment of an analytical instrument  100  connected to an analyzer  102 . The analytical instrument  100  receives a sample liquid  106  and measures dissolved carbon in the sample liquid  106 . Dissolved carbon in the sample liquid  106  is oxidized in a chemical reactor  150  to form carbon dioxide CO 2  gas that is delivered to outlet  108 . As the carbon dioxide gas at outlet  108  is produced over a time interval, the carbon dioxide at outlet  108  flows to the analyzer  102  for detection. A signal from analyzer  102  couples to a controller  104 . The controller  104  integrates and quantifies the signal from analyzer  102 . The controller  104  also couples to a control interface  110  to provide a control actuation sequence to the instrument  100 . The control actuation sequence is explained in more detail below in connection with an example shown in FIG. 5.  
     [0020] The instrument  100  includes a valve  112  that has a valve inlet  114  receiving the sample liquid  106 , a valve inlet  116  receiving liquid water  118  and a valve inlet  120  receiving a base liquid  122 . The liquid water  118  is preferably deionized water, and the base liquid is preferably sodium hydroxide NaOH. The valve  112  also has a first valve outlet  124  and a drain outlet  126 . The valve has a primary valve port  128  which the valve  112  can connect to a selected one of the other valve ports  114 ,  116 ,  120 ,  124 ,  126 . The valve  112  includes a valve control input  128  that connects to a valve positioning motor  129  that can be actuated to select one of the valve ports  114 ,  116 ,  120 ,  124 , 126  to connect to the primary valve port  128 .  
     [0021] A syringe pump  130  couples to the primary valve port  128 . The syringe pump  130  selectively pumps a selected one of the liquids from the valve inlets  114 ,  116 ,  120  to the first valve outlet  124 . The syringe pump  130  includes a pump control input  132  for actuating a syringe pump positioning motor  134 . The syringe pump  130  can draw in one or more selected liquids from the inlets  114 ,  116 ,  120  and then pump out the drawn in liquids to either the first outlet  124  or the drain  126 .  
     [0022] A sparger  140  (also called a sparging tube) receives a quantity of the sample liquid  106  and a quantity of the base liquid  122  from the first valve outlet  124 . Carrier gas is provided to the sparger  140  at sparger inlet  142 . The base liquid  122  and the inorganic carbon IC in the sample liquid  106  react with one another in the sparger  140  such that inorganic carbon IC is retained by the reaction and purgeable organic carbon POC is released by the sparge gas. The sparger  140  provides the purgeable organic carbon POC gasses during a first time interval to a chemical reactor  150 .  
     [0023] The chemical reactor  150  receives the purgeable organic carbon POC gasses. The chemical reactor  150  breaks down the purgeable organic carbon POC gasses to produce carbon dioxide CO 2 . The chemical reactor  150  generates carbon dioxide during the first time interval. The chemical reactor  150  can be any known chemical reactor which can break down organics and produce carbon dioxide. For example, the chemical reactor  150  can be a UV reactor, which does not use high temperatures, or can be a combustion reactor, which does use high temperatures.  
     [0024] A control interface  110  couples the control actuation sequence to the valve control input  128  and the pump control input  132 . The carbon dioxide flows from the chemical reactor  150  to the analyzer  102 . The analyzer  102  couples to the controller  104  that provides the control actuation sequence at control interface  110 . The controller  104  generates a first analyzer output  160  that represents a concentration of dissolved purgeable organic carbon POC in the sample liquid  106 . Depending on the needs of the application, the various actuation inputs can be electrical, pneumatic, optical or other know types of actuation. The first analyzer output  160  can be a display on a computer screen, data stored in memory, or an electrical output from the controller  104  depending on the needs of the application. The control actuation sequence during the first time interval is explained in more detail below in connection with an example timing diagram illustrated in FIG. 5.  
     [0025]FIG. 4 illustrates a block diagram of a second embodiment of a liquid carbon instrument  200  connected to an analyzer  202 . The instrument  200  includes many features that are similar to features in instrument  100 . Items in FIG. 4 that have the same reference numerals as items in FIG. 3 are the same or serve the same or a similar function. In addition to perfoming an analysis of POC, the analyzer  200  can also perform an analysis of inorganic carbon IC gasses and non-purgeable organic NPOC. In FIG. 4, a controller  204  coupled to the analyzer  202  includes an output  206  for actuating a gas valve  208  for controlling flow of the carrier gas at sparger inlet  142 . Also illustrated in FIG. 4, a UV reactor  250  is coupled to a second outlet  224  on valve  212 . The second outlet  224  receives oxidizing liquid  222  from valve inlet  220  and also receives liquid pumped back out of the sparger  140 . The oxidizing liquid  222  includes an acid. A moisture control system  260  and a chlorine scrubber  270  are included in the line from the UV reactor  250  to the outlet  108 .  
     [0026] The valve  212  includes the valve inlet  220  that receives the oxidizing liquid  222 . After the POC analysis is completed, the sparger  140  receives a quantity of the oxidizing liquid  222  and provides inorganic carbon IC gasses to the UV reactor  250  and on to the analyzer  202  during a second time interval. In the UV reactor  250 , the UV-promoted oxidation of organics is both physical and chemical in nature. The UV radiation boosts the energy state of molecules and makes them more reactive. In a preferred arrangement, the oxidizing liquid  222  comprises a persulfate, such as sodium, potassium or ammonium persulfate. The persulfate ion in aqueous solution is converted to a sulfate radical by the UV radiation. Hydroxyl radicals are produced by the UV radiation acting on the water molecules and additional hydroxyl radicals are formed by sulfate radicals reacting with the water. The hydroxyl radicals oxidize the carbon in the organic molecules to produce carbon dioxide.  
     [0027] The controller  204  generates a second analyzer output  261  representative of the concentration of dissolved inorganic carbon IC in the sample liquid  106 . Actuations during the second time interval are explained in more detail in connection with an example timing diagram illustrated in FIG. 6.  
     [0028] The liquids remaining in the sparger  140  after the second time interval is completed, i.e., during a third time interval, comprise remaining non-purgeable organic carbon NPOC. The liquids remaining in the sparger  140  are provided to the UV chemical reactor  250  during the third time interval. The UV chemical reactor  250  generates carbon dioxide during the third time interval. The controller  204  generates a third analyzer output  262  representative of the concentration of dissolved non-purgeable organic carbon NPOC in the sample liquid  106 . Actuations during the third time interval are explained in more detail in connection with an example timing diagram illustrated in FIG. 7.  
     [0029] The sparger  140  comprises a sparger outlet  144  and the UV chemical reactor  250  comprises a chemical reactor inlet  252 . A tube  254  connects between the sparger outlet  144  and the chemical reactor inlet  252 . The tube  254  forms a portion of a flow path that carries the purgeable organic carbon POC. The carrier gas flows along a flow path  280  from the sparger  140  to the UV chemical reactor  250  to the analyzer  202  and that flow path  280  is uninterrupted by valves.  
     [0030] The gas valve  208  has a gas inlet  209  that receives carrier gas. The gas valve  208  has a gas valve control input  210  that couples to the output  206  of the controller  204 . The sparger  140  has a sparger gas inlet  142  that receives the carrier gas from the gas valve  208 . The controller  204  provides the control actuation sequence, such as the one described below in connections with FIGS.  5 - 7  to the gas valve control input  210 .  
     [0031] The carrier gas flows along the flow path  280  from the sparger  140  to the UV chemical reactor  250  to the analyzer  202  that is uninterrupted by valves.  
     [0032] The moisture control system MCS  260  has an MCS inlet  264  coupled to a UV reactor outlet  256  to receive the carbon dioxide and has a MCS outlet  266 . The scrubber  270  has a scrubber inlet  272  coupled to the MCS outlet  266  and a scrubber outlet  274  providing the carbon dioxide to the analyzer  202 .  
     [0033] FIGS.  5 - 7  illustrate examples of control actuations of various components of the analyzer  200  during successive first, second and third time intervals. POC is analyzed during the first time interval, IC is analyzed during the second time interval, and NPOC is analyzed during the third time interval.  
     [0034]FIG. 5 illustrates a timing diagram during the first time interval  300  that shows control actuations during purgeable organic carbon POC analysis. The timing diagram illustrated in FIG. 5 is described below in connection with the instrument  200  in FIG. 4, however, portions of the timing diagram in FIG. 5 can also be considered in relation to corresponding similar features of the instrument  100  illustrated in FIG. 3.  
     [0035] At the start of the first time interval  300 , the gas valve  208  is opened as illustrated at time  302  in FIG. 5 and carrier gas is allowed to flow through the instrument  200  along flow path  280 . Also at the start, a UV lamp in the UV reactor  250  is turned on as illustrated at time  304 . First time interval  300  includes time phases A, B, C, D, E, F, G. During phase A, the valve  212  is first positioned to connect the syringe pump  130  with the oxidizing liquid inlet  220  as illustrated at time  306  and the syringe pump  130  draws in oxidizing liquid  222  as illustrated at time  308 . Next in phase A, the valve  212  is positioned to connect the syringe pump  130  with the second outlet  224  as illustrated at time  310  and the syringe pump  130  pumps out a quantity of the oxidizing liquid  222  to the UV reactor  250  as illustrated at time  312 . During phase B, liquid water  118  is drawn in at time  314  and pumped out to the UV chemical reactor  250  as illustrated at time  316 . During phase C, the pump is rinsed with water at  318 ,  320 . During phase D base liquid  122  is drawn in at time  322  and pumped out to the sparger  140  at time  324 . During phase E, the pump is rinsed with water at times  326 ,  328  and the controller  204  saves a baseline at time  330 . Saving the baseline is essentially a rezeroing of an integrator so that the integrator is ready to integrate a sample. During phase F, the carrier gas is shut off as illustrated at time  342  and a quantity of sample liquid is pumped into the sparger  140  at time  332 , and the analyzer  202  begins peak integration of the carbon dioxide at outlet  108  as illustrated at time  340 . During phase G, the carrier gas is turned back on at time  344  and peak integration continues to time  346  after substantially all of the POC has reacted in the UV chemical reactor  250 . At the end of first time interval  300 , the instrument  200 , but not the instrument  100 , is ready to begin a second time interval explained below in connection with FIG. 6.  
     [0036]FIG. 6 illustrates a timing diagram during a second time interval  400  that shows control actuations during inorganic carbon IC analysis. Second time interval  400  includes time phases H and I. During the phase H, the baseline is saved as illustrated at time  402 . During phase I, oxidizer is pumped out to the sparger  140  as illustrated at time  404  and peak integration is performed as illustrated at time  406 . Peak integration continues until after substantially all of the CO 2  produced by the inorganic carbon IC is integrated. At the end of second time interval  400 , the instrument is ready to begin a third time interval explained below in connection with FIG. 7.  
     [0037]FIG. 7 illustrates a timing diagram of control actuations during a third time interval  500  that shows non-purgeable organic carbon NPOC analysis. Third time interval  500  includes time phases J, K and L. During phase J, additional oxidizer liquid is pumped out to the UV chemical reactor as illustrated at time  502 . During phase K, the instrument  200  is allowed to stabilize and a baseline is saved at time  504 . During phase L, peak integration is started at time  506  as the remaining sample in the sparger  140  is pumped in by the syringe pump  130  through the first outlet  124  (which acts as an inlet) and pumped out by the syringe pump  130  through the second outlet  224  to the UV chemical reactor  250 . Peak integration continues until after substantially all of the CO 2  produced by a reaction of the non-purgeable organic carbon NPOC and the oxidizing liquid is integrated. At the end of the third time interval  500 , the analysis of the sample fluid is complete. The controller  204  can calculate a sum of POC+IC+NPOC to provide a measurement of total carbon TC.  
     [0038] It is to be understood that even though numerous characteristics and advantages of various embodiments of the invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary depending on the particular application for the dissolved carbon analysis while maintaining substantially the same functionality without departing from the scope and spirit of the present invention. The chemical reactor may be a UV persulfate reactor, a combustion reactor or other know type of reactor. In addition, although the preferred embodiment described herein is directed to a benchtop laboratory style of instrument, it will be appreciated by those skilled in the art that an embodiment as a process analyzer can be implemented as well. The teachings of the present invention can be applied to other chemical processing instruments without departing from the scope and spirit of the present invention.