esc.fnwi.uva.nl · web viewvarious techniques are available to determine the chloride...

Chloride determinationComparison and improvement of different methods

Supervisor Quaker : Dr. J.M. van der VeerSupervisor UvA : Dr. W.T. KokProduced by : Dennis DrostDate : June 2012

Bachelor project 3rd year

Chloride Determination

1 Abstract

This research is focused on comparing data from different methods executed on different locations concerning chloride determination. The goal of this research is to find what influences the analysis of Quaker Chemical B.V. products and to search for a way to filter out/compensate for these matrix effects. This is done by comparing previous results with new data. Different methods like titration, ion chromatography and X-ray fluorescence are compared to give a clear picture about what influences the different methods and how they can be improved. In the end for both titration and ion chromatography raw materials are found that “act as if they are chloride”, and different methods and sample preparation methods are proposed to guarantee a better chloride determination.

1.1 Summary

Quaker Chemical B.V. is a worldwide leader in industrial lubricants. Among others they produce lubricants for metalworking and tube & pipe industries. If these lubricants contain high concentrations of chloride and other salts, the steel products made by those industries will be of low quality or not usable at all because of corrosion. Many maintenance tests are carried out to monitor the conditions of the emulsions. In this monitoring some tests give different readings when performed at different locations, of with different methods. One of these is chloride determination.

The purpose of my bachelor project is to compare the different ways of determining chloride concentrations, investigate what factors affect the measurement and to search for a way to compensate for these matrix effects or to eliminate these effects all together. The purpose of my bachelor project is:

To compare the different ways of determining chloride concentrations To investigate the factors that affect/interfere with this measurement To search for a way to compensate for the matrix effects or to eliminate the effects all

together

In this research I mainly focused at titration and ion chromatography, but also looked at X-ray fluorescence. It was found that with the titration not only the equipment can cause errors in the measurement, but some raw materials can too. These raw materials interact the same way as chloride in the titration and therefore are measured as chloride. Ion chromatography is initially not the best choice for Quaker products because it’s not possible to inject organic solvents or oils into most IC columns and most Quaker products are emulsions containing oil and organic compounds. This can be overcome by doing a separation step prior to the injection, then ion chromatography can be used to analyze these products. Then the problem arises that some raw materials interfere with the chloride peak by, or coming out at, almost the same time as chloride, or chancing the shape of the chloride peak. By chancing the column and the method, or even shifting to another setup with different possibilities a great improvement is achieved in the analysis with ion chromatography. Still the best results were gathered with X-ray fluorescence. This technique has almost no hindrance from the interference that disrupts the readings with the other methods and therefore probably can give the best results regarding the chloride concentration. At the end also a cost-benefit analysis is done for the found methods.

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Table of contents

1 ABSTRACT...............................................................................................21.1 SUMMARY..............................................................................................2

2 INTRODUCTION......................................................................................43 RESULTS..................................................................................................6

3.1 TITRATION..............................................................................................63.2 ION CHROMATOGRAPHY..........................................................................93.2.1 ION CHROMATOGRAPHY AT THE UNIVERSITY OF AMSTERDAM................133.3 OTHER METHODS...................................................................................153.3.1 SCANNING ELECTRON MICROSCOPE (SEM)............................................153.3.2 X-RAY FLUORESCENCE (XRF)..............................................................163.4 SEPARATION METHOD............................................................................16

4 DISCUSSION AND CONCLUSIONS.......................................................194.1 RECOMMENDATIONS..............................................................................21

5 REFERENCES........................................................................................236 ATTACHMENTS....................................................................................24

6.1 SOLID PHASE EXTRAXTION SEPARATION METHOD....................................246.2 TITRATION METHOD AND SETTINGS.........................................................246.3 PROJECT OUTLINE..................................................................................266.4 NAOH ELUENS CONCENTRATION SEARCH................................................276.5 CHLORIDE TITRATION IN FRANCE............................................................286.6 INTERNAL (UNPUBLISHED) DATA.............................................................29

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2 Introduction

Quaker Chemical Corporation is a leading global provider of industrial lubricants, hydraulic fluids, drilling fluids and metalworking fluids. They provide approximately 350 different process fluids and associated services to a wide range of industries including steel, aluminum, automobile, mining, aerospace, tube and pipe coatings and building materials. Quakers headquarters are located in Conshohocken, Pennsylvania. Since 1962 the European headquarters are based in Uithoorn, the Netherlands and from 1963 it has worldwide offices in England, Italy, Australia, Japan, Spain, South Africa, Mexico and Canada.

Many of the metal working products are emulsifiables. They consist of a lot of different, typically technical-grade, raw materials. These emulsions are offered as a concentrate to the customer, and mixed on site with water up to volumes between 1 and 100 m3. The water, used to emulsify these concentrates, is often not de-mineralized water, but on site available ground-, river-, or drinking water. This water is often a source of pollution in the emulsions. To ensure the quality and functioning of the emulsions for the long period of which they are used over (often several years), various properties of the emulsions are monitored. Think of daily pH control, weekly microbe tests and monthly difficult microbe tests and more extensive analysis including chloride determination. Various techniques are available to determine the chloride concentration, which vary from gravimetric and potentiometric methods like titration, to high-tech methods as ion chromatograph, X-ray fluorescence (XRF) or inductively coupled plasma-mass spectrometry (ICP-MS).

When chloride determination is applied to Quaker products varying of results are found. The variance is found between different methods, data from previous determinations, or data from other locations1. This often leads to unresolved debates about the conditions of the products and makes the exact condition of the product unknown, which can lead to improper maintenance with potentially adverse consequences for the customer, as can be seen in figure 1. These consequences can be very serious, regarding the replacements of entire systems, corroded or damaged machinery and claims addressed to Quaker.

Chloride determination has been an issue for quite some time at Quaker 1. Most of the time problems arise from differences between chloride concentrations measured by a costumer (who often not discloses its analytical methods), the analytical department at Quaker, and even between methods here2. There is no problem in analyzing transparent, low content samples with the Marcherey-Nagel equipment (photometric water analysis)3, Most Quaker products though are non-transparent emulsions, so this method does not work here. The most used method to determine the chloride concentration at Quaker is titration with AgNO3,. This because it is a very simple technique that can easily be done at the small labs, available at the fabric. It is based on the reaction of Cl- with Ag+ titration, is an old method to determine chloride concentrations 4 and can be influenced by a lot of other components that also react with silver.

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Figure 1 Example of corrosion on costumer products


Ion chromatography is also a method that is used to analyze chloride, other ions and almost any other charged or polar molecule5, it works good on different kinds of samples and especially on water6. This method is based on high pressure liquid chromatography (HPLC) but then with the interaction of ions with material in the stationary phase of a column7. So it would be very suitable to measure the chloride content of Quaker products, even though the columns for the ion chromatograph are not suited for injecting emulsions8.

Another method that can be used to detect chloride is X-ray fluorescence. What happens: Materials are exposed to short wavelength radiation (X- or gamma rays) to excite some of the atoms present in the sample. When an electron in the excited atom “falls down” in to a lower orbital, it emits a photon with the exact energy of the difference in energy of the two orbitals. This is effect is shown in figure 2. This photon is detected and from this exact energy the element, emitting this specific energy, can be identified and by the intensity of the photons the concentration can be measured9 .

Figure 2 simplified mechanism of XRF

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http://upload.wikimedia.org/wikipedia/commons/4/41/X-ray_fluorescence_simple_figu


3 Results

In this report names of products and components of Quaker Chemical B.V. are not given, this to protect their intellectual properties. These names are replaced by letters.

Different methods can be used to determine chloride concentrations in samples. The one most used by Quaker is titration with AgNO3, but this method is questioned due to its repeatability and accuracy with emulsion samples10. Other methods that are used in this research are ion chromatography and XRF.

3.1 Titration

At Quaker, chloride determinations are carried out by quality control (QSG). There they use a metrohm 655 dosimat with a metrohm 6.0130.100 Ag,AgCl, 3M KCl electrode, silver reference electrode, metrohm 657 control unit and a metrohm 672 titroprocessor as titration setup and titrate with 0.01N AgNO3. In theory this method is very suited to determine chloride concentrations11. The results gathered at QSG are in inconsistent when repeated. This is shown in chart 1, which shows the difference with the theoretical expected chloride value (based on the added NaCl), normalized to the value of the NaCl standard, so the zero value is the value theoretically expected. To a standard NaCl solution a variety of different raw materials was added to see if, and what kind of influence they have on the titration and the found Cl- concentration. These raw materials were also analyzed pure and mixed with industrial water containing chloride (product B). What is striking about these results, is that it seems that most raw materials (but mostly A and B) interfere with the titration and that the results are fluctuating a lot.

Chart 1 Titration results QSG

To see whether the titration method itself or the setup at QSG was the source of the inconsistent results, a new titration setup was build using a metrohm 716 DMS titrino with a metrohm 6.0130.100 (Ag, AgCl, 3M KCl) electrode, a silver reference electrode and a 0.01N AgNO3 solution. The method and settings can be found in the attachments. The results of this setup are shown in chart 2. The chemicals A and B give the greatest influence on the titration. Also a lot of

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raw materials cause multiple end points on the titration. Again material A and material B cause this most of the time, but others like material C and D have multiple end points also , while NaCl on the new titration setup always has one endpoint. The titration setup at QSG can also give multiple endpoints even for NaCl standard solutions.

Chart 2 Titration results own setup

To compensate for these matrix effects the standard addition method was performed. With the standard addition method known amounts of the analyte is added to a sample of unknown analyte. When the results are put in a graph a line can be plotted trough these points and where this line goes through the x-axis (y=0) the absolute value of that point is the concentration of the sample 12 . For this test a product of Quaker was chosen which gave the greatest fluctuations in previous analysis (product A). This product was tested as a 10% emulsion, which is close to its working parameters.

Chart 3 Results of standard addition method with titration

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In chart 3the results of the SA method on product A is shown. The first end point (EP) of the titration is clearly not the one caused by chloride, as it does not increase when more NaCl is added to the sample.

In an attempt to get better results a separation was performed using HNO3, about which more information can be found in paragraph 3.4. HNO3 was used because again the SA method was used to see if there was less interference. This is true when the 0 value is close to the calculated value, and if the now found value is close to the original value of the whole emulsion.

As can be seen in chart 4 the found value is quite low, but can be caused by two reasons. One; by adding the acid the water layer is diluted because the acid itself is also diluted in water and second; the 0 measurement is a lot lower than the rest of the line, so it can be a deviation. The chloride concentrations of product A ranges from 268-485 ppm when analyzed at QSG and with the new setup lying around 471 ppm, both with two endpoints. The difference is further explained in the conclusion but can be due to the equipment used at QSG

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.080

1020304050607080

f(x) = 983.637931034482 x + 2.60068965517242R² = 0.995293660352978

standaard additie methode

EP1Linear (EP1)

concentratie Cl toegevoegd (mg/ml)

ppm

Cl

Chart 4 SA method with titration on water layer

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3.2 Ion Chromatography

Ion chromatography has been used by Quaker in the past to determine chloride concentrations13. Then it was found that there are interfering peaks close to/ underneath the chloride peak and that titration at the moment was an easier option to determine chloride in emulsions because IC had too much interference1. Because ion chromatography should be very suitable to detect chloride7, this technique is also included again to check Quaker products to see if with different methods it can be used.

The Standard addition method was also done using the ion chromatograph. With the IC it has been unable to do a good analysis of the water layer after the previous used separation, because it is too acidic for the column. When trying to neutralize the water layer, as much base is needed that the detector of the IC gets overloaded by the Na+ or other ions in these bases. When separation by salt is done, it is found that multivalent salts work better. The salt that was used in the end was KAl(SO4)2. The same goes for separation by salt. Here again so much salt is needed that the detector gets overloaded, and the Cl- peak is undetectable, falls under the overloaded peak or deformed too much.

In chart 5 the standard addition method was done on the emulsion rather than on the water layer after a separation, because a suitable separation method was not found yet. This method gives a higher concentration than found with the titration. With this the concentration chloride in the 10% emulsion of product A is found 83 ppm.

product A standaard additie

y = 1008.6x + 16.795R2 = 0.9987

0

20

40

60

80

100

120

140

160

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14

concentration added Cl (mg/ml)

ppm

Chart 5 Results SA method 10% emulsion product A

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Chart 6 and 7 are product A compared to product A spiked with different raw materials. This was done to see if these materials affect the Cl- detection when using ion chromatography. It shows that material F (which is 45% material C diluted in TEA/water) clearly broadens the peak and also influences the area of the peak, making it 158 instead of 105 ppm. Material B is influencing the detection of Cl- in almost the same way, also broadening and shortening the peak.

-10

90 1 - vanaf 4-18 #16 [modified by Drostd] product A ECD_1µS

1

1 - Cl - 2.333

2 - 3.0333 - 3.783 4 - PO4 - 7.500

-5.0

35.0 2 - vanaf 4-18 #17 product A 10ml spiked met 1ml 10% F ECD_1µS

2

1 - Cl - 2.383

2 - 3.0833 - 3.817

4 - PO4 - 7.500

-10

90 3 - vanaf 4-18 #18 product A 10ml spiked met 1ml 10% G ECD_1µS

3

1 - Cl - 2.333

2 - 2.6503 - 2.9334 - 3.683 5 - 7.117 6 - 8.333

0.0 1.3 2.5 3.8 5.0 6.3 7.5 8.8 10.0 11.3 12.5 13.8 15.0-10

90 4 - vanaf 4-18 #19 product A 10ml spiked met 1ml 10% H ECD_1µS

min4

1 - Cl - 2.350

2 - 2.9003 - 3.650 4 - 6.983 5 - 682 - 8.083 6 - 10.283

Chart 6 Product A spiked with material F, G and H

-10

90 1 - vanaf 4-18 #20 product A ECD_1µS

1

1 - Cl - 2.383

2 - 3.0003 - 3.717 4 - 6.817

-10

90 2 - vanaf 4-18 #21 product A 10ml spiked met 1ml 10%I ECD_1µS

2

1 - 2.467

2 - 2.9673 - 3.6674 - 6.700

5 - 10.517

0.0 1.3 2.5 3.8 5.0 6.3 7.5 8.8 10.0 11.3 12.5 13.8 15.0-5.0

50.0 3 - vanaf 4-18 #22 product A 10ml spiked met 1ml 10% B ECD_1µS

min3

1 - Cl - 2.367

2 - 2.8673 - Br - 3.5334 - 6.067

5 - 6.567

Chart 7 Product A spiked with material I and B

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Because of the nice results gained at the University of Amsterdam (see chapter 3.2.1) the NaOH eluens used there was also tried at Quaker. Because of the different column, different concentrations where tried to see what concentrations worked best at Quaker. 15mM NaOH gave the best results as can be seen in the attachments (chapter 6.4), chart 9 shows the results of product A run with this eluens.

Chart 8 Product A and C compared with product C spiked with material F. Red arrow is the chloride peak, the blue arrow is the peak suspected from material I and the green arrow is probably from material F.

Chart 9 Product A run with the final eluens (15 mM NaOH)

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Chart 10 shows the spectrum of product A with one of the best separations of the chloride peak and the peak from material I. When a calibration line is made it is found that this sample contains 328 ppm chloride, but due to its bad shape and low plate of around 800 or even under 500 sometimes while at the University of Amsterdam (UvA) a plate number of over 3000 is average. The average chloride concentration found with ion chromatography is 272ppm but it varies a lot depending on the peak of other components that come out of the column at the same time as chloride most of the time.

0.26 1.00 2.00 3.00 4.00 5.00 6.00 7.00 7.85-3.8

0.0

5.0

10.0

15.0

20.0

25.0

29.5 15 mM NaOH eluens SPE #36 [modified by Drostd] PA concentraat 10x verdunt ECD_1µS

min

1 - 2.173

2 - 2.423

3 - Cl - 2.570

4 - NO3 - 5.757

Chart 10 Product A, only spectra where the peak underneath the chloride peak was seen as a separate peak

Product B (shown in chart 11) is industrial water and is mostly used to compare the chloride peak. This because it is closer to the real products than a standard solution, but still is clean enough to get good peaks.

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0-5.0

10.0

20.0

30.0

45.0 vanaf 4-18 #25 produc B ECD_1µS

min

1 - Cl - 1.983

2 - 3.300

3 - 6.667

4 - 682 - 7.950

Chart 11 Ion chromatograph product B

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3.2.1 Ion chromatography at the University of Amsterdam

At Quaker the ion chromatograph had been out of use for more than a year and also the used columns are over date. To see if this gave additional problems detecting the right amount of chloride at the UvA the ICS-1000 was used with a ionpac AS-11 column and AG-11 guard column, the IC was also equipped with a ASRS 300 4mm chemical suppressor. The result is shown in chart 12. Because here more peaks are shown before chloride than at Quaker and because the chloride peak at Quaker might have another peak underneath it. The molecules that are underneath the chloride peak can interact at almost the same way as chloride and therefore come out at the same time. To separate these, the eluens generator can give a better separation at the start of the chromatogram, where chloride comes out. Examples of this can be seen in chart 12 and 13 where the chloride peak is sharper when compared with results gathered at Quaker.

0.48 1.00 2.00 3.00 4.00 5.00 6.00 7.13-3.00

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00 40mM NaOH ionpac AS20 #2 Product A SPE ECD_1µS

min

1 - 1.617

2 - F - 2.050

3 - 2.220

4 - Cl - 2.600

5 - NO3 - 3.100

6 - 3.553 7 - 4.760

Chart 12 Chromatograph product A measured at the UvA

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0-4.0

0.0

2.5

5.0

7.5

12.0 40mM NaOH ionpac AS20 #3 PA & I SPEµS

min

1 - 0.453

2 - F - 2.0603 - 2.230

4 - Cl - 2.607

5 - NO3 - 3.110

6 - 3.587

Chart 13 Product A spiked with I measured at the UvA

In the last period of this research there also was access to an ion chromatograph with an eluent generator and herewith the ability to create a gradient. This was the DX500 consisting of a GS50

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gradient pump, CD25 conductivity detector, AS50 chromatography compartment and the AS50 auto sampler. The main use of this was to create an even better separation at the beginning of the run and flush out everything at the end without having to wait more than a hour for the last parts to come out. The eluens generator used a thermo scientific eluent generator cartridge EGCIII KOH to generate the gradient out of demi water. As can be seen in chart 14 the first part of the chromatogram is separated very well and after the chloride peak the rest comes out fast.

Chart 14 Standard solution measured with gradient

The measurement of product A itself failed. There was no time to run it again, but in chart 15 can be seen that the separation of material F is a lot better in comparison with a normal eluens.

Chart 15 Product A spiked with material B, F and I measured with eluens generator

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3.3 Other methods

3.3.1 Scanning electron microscope (SEM)

The electron microscope is used to analyze different salts created by reacting both material A and NaCl with AgNO3. The created precipitation was dried to a salt and analyzed. For the other materials of interest for analysis with the SEM I was unable to get a salt from the precipitation that meets the SEM’s requirements, being totally dry and being big enough grains.

Material A is an organic sodium salt containing a sulfur atom, which is bound to the sodium. Chloride is practically not present in this salt, but sodium, sulfur and carbon are present in high concentrations as can be seen in chart 16. Recognizable parts are that N:O ≈ 1:3 and N:Ag ≈ 1:1 (in %Atomic mass) which is probably from AgNO3. The fact that chloride is not seen means that, while this material gives a reaction like chloride in the titration, another reaction is taking place. This can be sulfate reacting with silver, because the sulfate is, like the chloride, charged negative and in salt form bound to sodium.

In the analysis of the reaction product of NaCl and AgNO3 it was found that this reaction occurs clean, we found no by-products. NaNO3 is very soluble in water, so it is probably washed away before drying the precipitation. Again N:O ≈ 1:3 and N:Na ≈ 1:1, also Ag:Cl ≈ 1:1 as found in chart 17

Chart 16 SEM spectrum reaction product of material A with AgNO3

Chart 17 SEM spectrum AgCl

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3.3.2 X-ray fluorescence (XRF)

The XRF was used as a reference method to determine the chloride concentration in different samples. XRF is a very good way to determine the precise amount of elements present in samples. The zero value due to the silver source, which has a line at the chloride place, is around 5900 and can differ 2% as was found doing the measurements.Table 1 shows the results for different samples gathered with XRF.

5500 6500 7500 8500 9500 10500 11500 12500 135000

100

200

300

400

500

600

700

f(x) = 0.0895906123056213 x − 531.603125434878R² = 0.999217314608758

XRF

Chart 18 Calibration curve XRF

Sample ppmMaterial A 534.08Material B 2477.49Product A 221.50Product B 72.33Product C 94.09Table 1 Results XRF

3.4 Separation method

Because most of the products tested are emulsions, a separation of the oil and water part of the emulsion is desirable, assuming that the chloride stays in the water layer and most of the interfering components stay in the oil part. To check for each method how much of the oil was separated a dry weight balance was used and all separations where tried on product A.

Because of the fact that the emulsions used by metalworking are micro emulsions (particle size < 200nm) centrifugation is not an option because the particles stay in emulsion. When centrifugation is tested and the top layer is measured in the dry weight balance 4.18% stays behind, which is very close to the initial emulsion concentration of 10% especially considering that the concentrates itself also contains water. The emulsifiers used by Quaker are a mix of ionic and non-ionic emulsifiers. This means that they can be destabilized by chancing their charge, to neutral or to having a charge. This can be done by adding special polymers designed to destabilize these emulsions. The problem is that they all have chloride as an ion, this means that using these polymers will make the chloride determination after separating a lot harder because now there is also chloride in it from the separation polymer. Another possibility to separate the emulsion is to

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change the charge of the emulsifiers by using strong acid or multivalent salt. Using HNO3 good results were achieved in separating product A. By titration one of the multiple endpoints disappeared, so some of the interfering substances are gone.

But when an emulsion is split with acid, the resulting water layer cannot be analyzed with ion chromatography. This is due to the pH of about 0 or lower of the water layer while most columns can handle between 1 and 12. When trying to neutralize the water layer as much base is needed that the detector gets overloaded (almost all bases contain salt). If the sample is diluted just enough so the detector does not get overloaded, the peak of chloride is so small it is not visible anymore. When using salt to separate the emulsion the same effect arises, the detector gets overloaded.

In the search for a good separation method within the parameters of the ion chromatograph it was found that hexane and 1-butanol can improve the separation. To test this and look for the best way to prepare the samples for the IC 5, different samples were made, all with different separation methods.According to table 2, sample 1 and 2 are the best ways to separate the emulsion. Sample 2 looked better separated visually and both looked almost the same on the ion chromatograph (chart 19). So a combination of the two was used, namely: 10ml sample with 5ml KAl(SO4)2, ½ drop of HNO3 (68%) with 4ml hexane and 5ml 1-butanol.

Sample nr Emulsion KAl(SO4)2 HNO3 68% hexane 1-butanol emulsion% pH of water layer1 10 ml 3 ml .5 drop 3 ml 3 ml 1.14 62 10 ml 5 ml .5 drop 1 ml 5 ml 2.2 63 10 ml 2 ml 1ml 5 ml 3.11 34 10 ml 2 ml 1ml 5 ml 3.14 35 8 ml 8 ml 1 drop 4 ml 3.09 5

Table 2 Content and resulting separation and pH of the different tubes

-0.50

0.60 1 - VANAF 4-18 #60 [modified by ARGLab] reageerbuis 13 ECD_1µS

11 - Cl - 1.783

-0.60


21 - Cl - 1.800

-0.60


31 - 1.817 2 - Cl - 2.033

-0.60


4 1 - F - 1.4672 - Cl - 2.017

0.36 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.08-0.50


min

51 - Cl - 1.800

Chart 19 IC spectra of tubes 1 to 5 focused on the chloride peak

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After some time it appears that the recovery of this method was not very good. The main reason being, that the water mixes with the 1-butanol. This causes a dilution factor that is not included in the calculations and so generating wrong data. Because the exact mixture is unknown and also the percentage of the chloride that stays in the water instead of in the hexane or 1-butanol is unknown, this method was found to be under expectations.

The most effective method that has been found to separate the emulsion is using a strata C-18 SPE column. The exact method can be found in the attachments. The separation is based on the principle that the oil has more interaction with the column than water and therefore comes out of the column later. Not having to add substances detectable by the ion chromatograph is one of the biggest advantages of this method. Another is that one does not (if executed correctly) dilute a sample in the separation process. The recovery is found to be around 95% as can be calculated from the data available in table 3 and can be seen by the almost identical peaks in chart 20. This can be both lower and higher though, depending on how much the column is flushed with sample before the sample is collected; the more the higher the recovery. The emulsion percentage of this method is found to be less than 1%.

0.45 1.00 1.50 2.00 2.50 3.00 3.72-0.6

2.0

4.0

6.0

8.0

9.7

1 - 15 MM NAOH ELUENS SPE #13 NaCl 38.279gr/250ml zonder SPE 10x verdunt ECD_12 - 15 MM NAOH ELUENS SPE #14 NaCl 38.279gr/250ml zonder SPE 10x verdunt ECD_13 - 15 MM NAOH ELUENS SPE #15 NaCl 38.279gr/250ml met SPE 10x verdunt ECD_14 - 15 MM NAOH ELUENS SPE #16 NaCl 38.279gr/250ml met SPE 10x verdunt ECD_1µS

min

4321

1 - Cl - 2.650

Chart 20 Chloride peak before and after SPE method

Sample No. Sample Name Ret.Time Area (min)

Height (µS*min) Amount (ppm)

13 NaCl 38.279gr/250ml zonder SPE 10x verdunt 2.617 16.132 81.834 142.23

14 NaCl 38.279gr/250ml zonder SPE 10x verdunt 2.600 16.376 87.745 144.23

15 NaCl 38.279gr/250ml met SPE 10x verdunt 2.617 15.968 89.473 140.90

16 NaCl 38.279gr/250ml met SPE 10x verdunt 2.650 16.954 92.862 148.97

Average: 2.621 16.358 87.979 144.08

Table 3: Data belonging to chart 20, chloride peak before and after SPE method

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4 Discussion and Conclusions

The now used titration by Quaker at QSG gives very fluctuating results which can be seen in chart 1. This is probably not just due to the method itself, but also due the way it’s used and the age of the equipment. When titration is done in another setup, or in another place the results constantly give more than one endpoint (EP). The multiple endpoint problem is smaller as can be seen in chart 2 and in the titration results at France in the attachments. One of the problems can be the auto sampler that is used, when the electrodes are still dripping from the cleaning the auto sampler already starts turning. This can be seen by the drips of water that are between the samples (figure 3). This causes some of the old samples to pollute the next samples. This can be one of the reasons for the multiple endpoints gathered to. Also it is possible that some of the raw materials can react with the silver surface of the reference electrode, and this needs to be sanded away.

Even so: Executed perfectly titration is not a very good method to determine the chloride content in Quaker products. Most Quaker products contain a lot of sodium salts containing sulfur groups, like material A and B. These, if diluted, charged sulfur groups react with silver in the same way as chloride does in the titration reaction and therefore is seen as chloride in the determination. This effect can be seen in chart 2 looking at material A and B. These values are higher than expected, based on the added chloride content. A small part of this can be due to the chloride present in the raw material itself (material B holds a maximum of 2% chloride) but mostly it is due to the reaction of sulfur with silver. This is supported by the data gathered with the electron microscope, which shows that if material A reacts with AgNO3, a different reaction product arises then in the reaction of sodium chloride with AgNO3. By looking at the ratio of the different atoms, silver chloride is most probably the reaction product of the titration of NaCl with AgNO3 as expected. But when material A reacts with AgNO3 the product is probably not AgCl but AgS- material A which can be concluded by the ratios of the atoms present in the sample.

Theoretically ion chromatography is a very good way to analyze samples for chloride. The problem with Quaker products is their complexity. Most of the products consist of over 20 different raw materials and intermediates of which some are salts. These materials and especially the salts can interfere with the reading. They can come out at almost the same time as chloride or change/shift the chloride peak so that it would be harder to get a clear measurement. Examples of raw materials changing/interfering with the peak of chloride can be seen in chart 6 and chart 7. Here it is shown that material B and F influence the height and the width of the chloride peak a lot. None of the peaks shown in these graphs are nice symmetrical peaks, which suggest that in all samples something else comes out of the column at almost the same time as chloride. This was confirmed when additional measurements were done at the UvA as can be seen in chart 12. It shows two clear peaks before the chloride peak which are not (clear) shown on the measurements at Quaker. The measurements at the UvA were done to check if the bad measurements could be due to the long time the equipment was not used and the fact that the columns are over date. The

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Figure 3 drop of sample on the auto sampler


data collected at the UvA shows that another method, equipment and column can greatly improve the analysis.

Another reason why ion chromatography is harder for Quaker products is that most IC columns cannot handle organic solvents or oils, and almost all Quaker products are emulsions. The separation method used at the titration included adding a lot of salt or strong acid. Both made it impossible to use these samples in the ion chromatograph because of the pH range of the column, or that the salt overloads the detector so the desired peaks cannot be seen. In the search for a separation method suitable for IC analysis different combinations of KAl(SO4)2, HNO3, hexane and 1-butanol are used to find a way to keep the pH in the range of the column, so the detector is not overloading but still giving a good separation. In table 2 the content of the different tubes is shown, and their level of separation and pH. Together with their IC spectra (chart 19) it was observed that tube 1 and 2 gave the best results, so a combination of these two was chosen namely: 10ml sample with 5ml KAl(SO4)2, ½ drop of (about 0.05 ml)HNO3 (68%) with 4ml hexane and 5ml 1-butanol. It was found that this method had a very poor recovery because of 1-butanol mixing with water and therefore diluting the water layer, and even worse introducing organic solvents to the ion chromatograph. After this solid phase extraction (SPE) a convenient way to separate the emulsion was found. This was done by using a C-18 SPE column. This method was found the best sample preparation for ion chromatography, because no particles detectible by the IC were added. The recovery is close to 100% because chloride does not interact with the material in the column and the sample is almost not diluted in the process.

X-ray fluorescence is the technique found to be the least affected by the matrix of the emulsion. One of the problems is that the silver radiation source has energy lines falling on the same place as the chloride lines. This makes the chloride peak change around 1%, but this is far less than the accuracy of the other methods due to matrix effects.

In table 4 the measurements considering products A and C with different techniques are summarized. It can be concluded that titration is not suited to determine the chloride concentration for Quaker products, because of the interference caused by different raw materials 2. These materials, mostly sulfur containing, react the same way with silver as chloride does and so are seen as chloride. Ion chromatography combined with the SPE separation method would be very suitable for the analysis of Quaker products, however the actual method needs to be studied further, as can be found in my recommendation. With the current methods there are other materials coming out of the column at the same time as chloride, and therefore it is difficult to get a good reading of the chloride concentration. Even with those other materials coming out at the same time though, the interference is smaller as can be reasoned from the lower concentration, found with ion chromatography than by titration. Still the best method tested was X-ray fluorescence, because there is no interference of other materials and the reading only changes due to the silver source which radiates at the chloride line to.

Method Chloride concentration product A Chloride concentration product CTitration QSG 268-485ppm 114 ppmTitration new setup 471 ppm -Ion chromatography 272 ppm 112.8 ppmx-ray fluorescence 221.5 ppm 72.3 ppmTable 4 chloride concentrations measured with different techniques

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It is hard to compare the found chloride concentrations to theoretical data, because there is not much known about this in most raw materials. So the calculations that can be made only contain data about 25% of the used raw materials and therefore give results that are a lot lower than the actual measured concentrations.

4.1 Recommendations

It is recommended to change the standard chloride measuring method to ion chromatography or X-Ray fluorescence. While ion chromatography needs more research to find the best method for analyzing emulsions, the method itself is very suited to find not only chloride but also most other ions that are now measured with other equipment (think of Marcherey-Nagel or reflectoquant). This method however may need some additional investments concerning columns and a leaking chemical suppressor. X-Ray fluorescence is the best option to detect chloride without matrix effects, also it can be used to detect some other of the elements that are now checked for in other tests, but it can’t detect (directly) the ions consisting of more than one atom, molecules. Another drawback of this method is that there is only one XRF available at Quaker Uithoorn and it is most of the time used by the steel department.

Concerning the now used method the recommendation is to check the titration setup of QSG, if it still gives good and repeatable results, based on the fluctuating data gathered there (chart 1). If used on a clean and good working setup titration it can still be used to give a good estimation for most Quaker products, but products containing raw materials that have (charged) sulfur groups will give higher values because of these raw materials.

loon chemist per uur 100

IC QuakerXRF quaker

XRF laten doen

titratie Quaker ICS-1600 ICS-2100

Time analysis (hour) 0.25 0.12 0.00 0.10 0.25 0.10Analyses per month 50 50 50 50 50 50Material cost per analysis 1.50 0.50 70.00 0.10 0.50 0.50Cost equipment 46000.00 0.00 0.00 35000.00 55000.00Depreciate time (year) 10 10 1 10 10 10Material/expenses p/y 2000.00 800.00 0.00 0.00 2000.00 2500.00

comment gradientautosampler

Cost per analysis 29.83 21.50 70.00 10.10 34.67 23.83Cost per year 4,150.00 6,300.00 42,000.00 560.00 7,050.00 8,800.00Table 5 Cost of different analysis

Based on table 5 and all other data gathered in this report switching to ion chromatography for standard emulsion analysis is a affordable option. To do this for example the ICS-2100 will be a suited system because it comes with the possibility of a gradient due to the eluent generator and the auto sampler makes the time of the analysis shorter which makes it cheaper per sample. Personally I recommend IC over XRF, because IC has the potential to do a lot of standard analysis done now with different methods all at once.

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To make ion chromatography the new method for (standard) analysis of emulsions, or other samples at Quaker, additional research needs to be done to the separation method so that no oil or organic solvents will be injected in the column. When a new ion chromatography is bought, research is needed to find the best columns, gradient and other specifications to get the best separation of the peaks from the analyte and other compounds.

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5 References

(1) Merkenstein, W. V. Comparison of chloride determination methods. can be found in the attachements 2006.

(2) Smit, E. Chloride content analyses. can be found in the attachements 2006.

(3) Schneider, R. Photometric water analysis. Suitability for companies self control; Photometrische Wasseranalytik. Eignung von Kuevettentesten zur betrieblichen Eigenkontrolle. GIT 2001, 45, 630-632.

(4) Zall, D. M.; Fisher, D.; Garner, M. Q. Photometric determination of chlorides in water. Anal. Chem. 1956, 28, 1665-1668.

(5) Hern, J.; Rutherford, G.; Vanloon, G. Determination of chloride, nitrate, sulphate and total sulphur in environmental samples by single-column ion chromatography. Talanta 1983, 30, 677-682.

(6) MUSMECI, L.; BECCALONI, E.; CHIRICO, M. Determination of Chloride in the Leachates of Stabilized Waste by Ion Chromatography and by a Volumetric Method - Analysis and Comparison. J. Chromatogr. A 1995, 706, 321-325.

(7) Haddad, P. R.; Jackson, P. E. In Ion chromatography: principles and applications; Elsevier Science: 1990; Vol. 46.

(8) Weiss, J. Handbook of ion chromatography, 2 Volumes. Recherche 2004, 67, 02.

(9) Beckhoff, B.; Langhoff, N.; Kanngiefer, B.; Wedell, R.; Wolff, H. In Handbook of practical X-ray fluorescence analysis; Springer Verlag: 2006; .

(10) Beau, J. Chloride titration in emulsions. can be found in the attachements 2011.

(11) ZANCATO, M.; PIETROGRANDE, A.; MACCA, C. Sequential Determination of Sulfur and Chlorine in Organic-Compounds by Potentiometric Titration of Sulfate and Chloride with an Automatic Titrator. Ann. Chim. 1990, 80, 445-451.

(12) Saxberg, B. E. H.; Kowalski, B. R. Generalized standard addition method. Anal. Chem. 1979, 51, 1031-1038.

(13) Butter, I. Determinatino of chloride and sulphate concentration in two products. can be found in the attachements 2006.

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6 Attachments

6.1 Solid Phase Extraxtion separation method

Using a C-18 strata SPE column under -10kPa vacuum, activate the column by flushing two bed volumes of MeOH.

To clean the column add a minimum of four bed volumes H2O, this is important, otherwise there will be chloride from the column in your monster!

Add at least 2 bed volumes of sample, if wanting to dilute it before injection in the ion chromatograph, add the diluted sample to the SPE this gives better results.

Wait until at least one bed volume of sample is absorbed by the column before collecting the actual sample, this to prevent diluting the sample with the H2O present in the column from the cleaning.

The collected sample can directly be injected in the ion chromatograph without a filter.

6.2 Titration method and settings

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6.3 Project outline

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6.4 NaOH eluens concentration search

0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0-2.0

0.0

2.5

5.0

7.5

10.0

12.5

16.0 15 mM NaOH eluens SPE #2 standaard zonder spe 3mMNaOH ECD_1µS

min

1 - 2.717

2 - 4.150

3 - 7.0174 - 8.650

0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0-2.0

2.5

5.0

7.5

10.0

12.5

15.0

17.5


min

1 - 1.8502 - 2.767

3 - Br - 4.6004 - NO3 - 5.633

5 - 10.450

6 - 25.617

0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0-5.0

0.0

5.0

10.0

15.0

20.0


min

1 - F - 1.617

2 - 2.300

3 - 3.6674 - Br - 4.433

5 - 13.067

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6.5 Chloride titration in France

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6.6 Internal (unpublished) data

Chloride content method Comparison of chloride determinations combined Chloride 40032-11 and 041208-05 Determination of chloride and sulfate concentration in two products

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Report to : Andre Hendriksen

Reported by : Julie Beau

Date of report : 19 December, 2011

Account : Internal / Klant

Subject :

Reference : EU-MG 2011-1527

Object : Chloride titration in emulsions

IntroductionIt was requested to MWCSLNL to perform two chloride titrations on two products (041837-01 and 043040-01) theoretically containing 170ppm chloride for Klant.

Materials and Methods

Materials043040-01041837-01

MethodThe analyses are performed according to standard QTN methods.

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ResultsFirst tests have been performed with the standard method (equipment used at QSG) using 10.00g of a 5% emulsion in demineralised water (meaning we should find a result around 8.5 ppm):

EP1 (ppm) EP2 (ppm) Average value (ppm)

043040-01 11 22041837-01 2 5

It has been asked to QSG how do they deal with two EPs and we have been told that they usually calculate the average.

Since the results were not really coherent, we have considered that it might be due to the fact that the concentration was too low. Thus, new titrations were performed with 20.00g of 10% emulsions (meaning we should find a result around 17 ppm):

EP1 (ppm) EP2 (ppm) Average value (ppm)

5% 043040-01 in demi

21 30 25.5

5% 041837-01 in demi

13 18 15.5

Generally speaking, we can say that between those two measurements, the tendency is that the chloride content in 041837-01 is lower than in 043040-01 but the values are not doubled compared to the first values which could have been expected.

It has been decided to perform 3 more times the same titration with the same 10% emulsion.EP1 (ppm) EP2 (ppm) Average value

(ppm)

10% 043040-01 in demi

21 30 25.519 24 21.527 44 35.511 21 16

10% 041837-01 in demi

13 18 15.57 11 913 26 1812 31 21.5

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There is no consistency in the results. The curves on the printed tickets do not have the same profile and the existence of two bending points is questionable. It seems that the titration is performed correctly but it might be that the detection equipment of the turning point is too sensitive and is set to stop after the second detected point.

Example:

In this case, the equipment detects a stable period that is too short to be a ‘real’ bending point. In this particular case, it would be suggested to only consider the second value given/calculated by the measuring device. This has been confirmed when known chloride salts samples have been titrated.

Considering this reasoning, the equipment gives the following results for the mentioned samples:

calculated value (ppm) measured value (ppm)0 0.2 (only one EP)10 7.6 (only one EP)50 46.7100 96.8

Unfortunately, it is not that clear and it can happen that we have two distinct bends or a linear line where the equipment detects already two stable periods and stops the measurement.

In order to determine the chloride content of the samples for Klant, measurements have been performed with the XRF equipment from BRUKER but at low concentration (<100ppm) the measurements are not accurate enough.

Ion chromatography has also been performed but this method is more adapted to water samples. It would require a complicated preparation of emulsion samples.

ConclusionsWith the standard method, the titration is done correctly but we have to be careful with the automatic result values that are given. The reading of the curve can help but when not possible, the values can be uncertain.Even though the performed tests were not very conclusive, the use of a handheld XRF might not be to exclude for chlorine content determination. The inaccuracy of the results is partly due to the fact that the chlorine peak is merged with the rhodium peak. This might be solvable with a particular set up of the equipment.Ion chromatography is not suitable for emulsion samples.In any case, a discussion should be initiated (also with QSG) on the accuracy of the results we get with the standard method and how we can improve it to give more reliable results in our reports.

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Report to : J. Hooijman

Reported by : E. Smit

Date of report : March 13, 2006

Account : Klant

Subject : 040032-11 and 041208-05

Reference : EU-MG 2006-1038

Object: Chloride content analyses

IntroductionKlant used the 040032-11 and the 041208-05. Both concentrates have been analysed by the customer on Chloride content by titration with Silver Nitrate solution. The customer found a result of 2000-3000 ppm in both products. The Chloride content will be analysed by Ion-Chromatograph (IC) and by titration with Silver Nitrate solution.

Materials and MethodsMaterials:Retain sample 040032-11 : lot# 96477.Retain sample 041208-05 : lot# 90636.Sample made at the lab; march 2006 (040308-07)

Methods:Standard QTN Methods.

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ResultsFor all three concentrates the Chloride content is analysed by IC and by titration with Silver Nitrate solution.

Description 041208-05 040032-11 Sample made at lab UOM MethodChloride by IC

287 601 502 ppm P012

Chloride by AgNO3

4265 3960 495 ppm Z026

Results customer

2000-3000 2000-3000 - ppm

When QTN Z026 is used (titration with Ag NO3 solution), only the 040032-11 gives a reasonably low amount of Chloride. The other two concentrates contain a copper inhibitor that reacts with the Silver Nitrate. It is analysed before that concentrates containing this raw material show an extreme high amount of Chloride when method Z026 is being used.

As can be seen in the table: the 040032-11 gives for both methods approximately the same amount of Chloride. The results for the 041208-05 differ almost 4000 ppm and the results of the 040032-11 differ more than 3000 ppm.

ConclusionsThe 040032-11 and the 041208-05 seem to contain around 4000 ppm Chloride when the titration with AgNO3 solution is performed (method QTN Z026).The 040032-11 and the 041208-05 contain 287 ppm, respectively 601 ppm when the IC is used for analysis.The difference between both measurements is enormous, but can be related to one raw material: the copper corrosion inhibitor. This raw material reacts with the AgNO3.The sample made at lab which is used as a reference shows approximately the same results for IC and titration: 500 ppm

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esc.fnwi.uva.nl · web viewvarious techniques are available to determine the chloride...

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