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Colorimetric determination of microquantities of fluorine in organic compounds
MICROCHEMICAL
Calorimetric
VOL. V, PAGES 617-624 (1961)
JOURNAL
Determination
Fluorine
in Organic
of Microquantities
of
Compounds
HAROLD J. FERRARI, FRANCIS C. GERONIMO, and LOUIS M. BRANCONE, Lederle Laboratories Division, American CyarLam,id Company, Pearl River, New York
Increased interest in organic compounds containing fluorine has emphasized the need for a quantitative procedure for fluorine with the accuracy and precision required in microanalysis. This fact is substantiated by the number of papers on the subject as well as statements in a recent review by Ma.’ Our own review of the literature led us to consider various methods which for one reason or another were not suitable for our use.z--Lo At the time that we initiated our work the samples of interest were in extremely short supply and cont’ained 3-47& fluorine. These factors necessarily limited us to the use of calorimetric methods, and the most feasible one seemed to be the one described by Megregian” which he employed to determine fluorine in water or on distillates containing fluoride ions. This method stressed the features that we were seeking, such as precision, accuracy, speed, rapid and stable color development, ease of manipulation, elimination of a distillation step, and permitted one t)o work in the microgram range. In view of these considerations we chose to adapt this method to the analysis of organic compounds by the inclusion of a combustion step; originally this was a sodium fusion and lat’er the Sch6niger flask combustion technique was adopted. Since we undertook our work in 1954 some newer methods have appeared that have circumvented the drawbacks of the procedures mentioned above. BelcheF describes a method utilizing aliaarin complexone (1,2-dihydroxyanthraquino1le-S-yl-methylamine-N,N-diacetic acid). This reagent represents the first time that a chemical has been 11sedthat reacts directly with the fluoride ion to develop a 617
G18
H. J. FERRARI,
F. C. GERONIMO,
L. M. BRilNCONE
color instead of relying on the bleaching effect of the fluoride ion on a colored metal complex.* Steyermark et a1.13 employed thorium nitrate titration of the fluoride ion with sodium alizarin sulfonate as the indicator. Fine and Wynne14 use lanthanum chloroanilate for the direct calorimetric determination of fluoride ion based on the earlier work of Bertolacini and Barney. l5 Senkowski et a1.16describe a procedure using the Megregian eriochrome cyanine R calorimetric method which is similar to one we have employed in our laboratory for some time. Our procedure differs from that of Senkowski’s as follows: (1) Smaller samples can be used (0.5-1.5 mg.) ; (2) sodium peroxide is not required in the combustion step; (3) a neutralization step is not necessary; (4) smaller volumes of solution reduce the overall manipulations; (5) the precision and accuracy of our method decreases on samples containing more than 20% fluorine. A few examples of the types of compounds assayed and the results obtained are listed in Table I. TABLE I Results Selected from Analysis of Routine
Research Compounds y. fluorine
Compound Fluorinated Steroid
piperaaine
Fluorobenzene sulfonamide Piperazine trifluoracetate Fluorinated piperazine Difluorochloroacetyl Amino fluoro acid
Theory
Found
5.90 4.38 3.95 4.37 3.95 5.60 18.00 20.90 13.82 9.60
5.93 4.16 3.88 4.65 3.93 5.87 18.37 21.02 13.72 9 .80
Experimental Reagents
Sodium Fluoride : Twenty to twenty-five milligrams of reagent NaF is dried for l-2 hr. at lOO”C., then accurately weighed and dissolved in 1 liter of HzO. * This information was presented in a talk to the Metropolitan Society in New York City on February 12, 1959. MICROCHEMICAL
JOURNAL,
Microchemical VOL.
V, ISSUE
4
MICRO&UANTITIES
OF FLUORINE
619
Zirconium Chloride : Two hundred and seventy milligrams of ZrOClz.8Hz0 is dissolved in 50 ml. of H20. Then 700 ml. of concentrated HCl is added and the solution is diluted to a liter with HZO. Eriochrome Cyanine R : Dissolve 1.8 g. of ECR dye in 100 ml. HzO. Reference Acid Solution: Seven hundred milliliters of concentrated HCl is diluted to a liter with HzO. Sodium Hydroxide (2N): Eighty grams of reagent NaOH is diluted to a liter with H20. Schiiniger Sample Carriers: No. 6471-F,* Arthur H. Thomas Co. Preparation of a Standard Curve Three aliquots containing 30 pg. F-/ml. are transferred to Nessler tubes and diluted to the 50-ml. mark with HzO. Then 5.0 ml. each of ECR and ZrOCls are added to each tube and the tubes are shaken well. The reference solution contains 50 ml. Hz0 plus 5.0 ml. of each ECR and HCl. The solutions are allowed to stand before reading to attain room temperature, and then read at 528 rnp using a Beckman DU Spectrophotometer. The average of these three aliquots is used to calculat,e the absorbance at 20 and 40 pg. concentrations (Table VI-4).
Analysis of an Unknown The following weight of sample is taken for the different percentages of fluorine : Weight, mg. “% o-5 5-20
1.0-1.5 0.5-1.0
A suitable weight of sample is transferred to a Schaniger” filter paper carrier and folded to fit the platinum grid of the Schijniger stopper. The flask containing 4 ml. of 2N NaOH is flushed with a stream of oxygen for 10-20 sec. The stem of the filter paper, contained in the platinum grid, is ignited and placed into the flask to complete the combustion in the usual manner. The contents of the SchGniger flask are transferred directly to the Nessler tube and diluted to the 50-ml. mark with HzO. If the * Fluoride
free.
G’LO
H. J. E’ERRARI,
F. C. GEIWNIMO,
L. M1. 1~11ANCONE
fluoride content exceeds 50 pg., then the contents are transferred to a loo-ml. volumetric flask made up to volume and an aliyuot is taken to obtain a content between 30-50 Mg. The color complexing reagents are added and the optical density determined spectrophotometrically using a Beckman DU. The concentration is obtained by referring to the standard curve.
Calculation :
where C = concentration obtained from standard curve, L, = dilut,ion factor, and X = sample weight.
Discussion Combustion Techniques. Prior to the introduction of the Schiiniger Flask combustion, the samples were heated with metallic sodium18 in a sealed Carius t’ube at 400°C. for 1 hr. The excess sodium is destroyed by dropwise addition of methanol. After all the sodium is destroyed, the content,s of the tube are quantitatively transferred by filtration into a lOO-ml. volumetric flask and diluted to the mark with H,O. A suitable aliquot is taken and the procedure for the color reaction is then followed as previously described. The overall time for sample preparation, combustion, and filtration by the sodium fusion requires approximately 21/2 hr. A filtration is always necessary to remove the carbonaceous residue. The SchGniger combustion requires 15-20 min. and the final solution is always clear, eliminating the need for filtration. TABLE II Standard Samples by Sodium Fusion and Schiiniger Combustion Techniques NO.
1 2 3 4 5 6
-
p-Fluorobenzoic acid (13.56% F) Na fusion Schijniger 13.88 13.74 13.37 13.10 13.57 13.53 MICROCHEMICAL
13.89 13.94 13.68 13 25 13.55 13.97 JOURNAL,
VOL.
V, ISSUE
4
MICROQUANTITIES
621
OF FLUORINE
Table II lists standard samples of p-fluorobenzoic acid combustion by the sodium fusion and the Schijniger combust,ion techniques.
Effect of Sulfate Using ECR (Geigy) the statistical data [Table VI, (3)] shows a slight positive bias when SO,--- is present in concentration up to I mg. Generally, the presence of SO,-- requires a separation by a Willard and Winters distillation. I0 However, the results obtained in Table III with t)his sulfate concent,ration are well within the allowable limits and require no addit.ional treatment for the removal of SO,--. TABLE III Effect of Sulfate Sample No.
Cont. SOa, mg.
Theory
Found
1 2 3 4 5
1.0 1.0 0.7 0.7 0.5
5.90 7.40 6.00 5.60 6.02
5.81 7.42 6.13 5.92 6.20
The presence of phosphate ions also interferes as reported by Megregian. l l Although these ions result in correspondingly higher fluoride values, this type of interference is not encountered as frcquently as the sulfate one. If the phosphate concentration is higher than the tolerance reported by Megregian a distillat’ion step as recommended by him will obviate this difficulty.
Effect of Temperature Megregian recommends that the reaction be carried out in the range of 22-28’C. and that the standard curve and the sample be read within ~2%. of each other. Temperature control is a very critical factor with some spectrophotometers. The instrument used in this work originally had a cell compartment temperature of 3% 35’C. Baffles were installed along the sides of the compartment to act as air condensers which reduced the temperature to about 26’C. Readings are taken over a IO-min. period until a constant optic&al density, within the limits of the instrument, is obtained.
622
H. J. FERRARI,
F. C. GERONIMO,
L. M. BRANCONE
Effect of pH on the Color Reaction The pH of the standard NaF solution is in the vicinity of while the solution following the Schijniger combustion is in the of pH 11. Three aliquots of standard NaF solution were run in the manner at pH 7, and three were adjusted to pH 11 with NaOH to the addition of the color-forming reagents. The results are in Table IV.
pH 7 range usual prior listed
TABLE IV Effect of pH on the Color Reaction for Standard NaF Solutions Cont. pg. NaF STD solutions
Cont. pg. at pH7
Cont. pg. at pH 11
30.00 40.00 50.00
30.20 39.91 50.62
30.30 39.90 50.25
Nine samples of p-fluorobenzoic acid were combusted by the Schiiniger Flask Technique using 4 ml. of 2N NaOH as the absorber. In three samples the pH was not adjusted (pH 11) ; three were adjusted to pH 7, and three were adjusted to pH 2 with HCl. Then the color-forming reagents were added and the results are listed in Table V. TABLE V Effect of pH on the Color Reaction for p-Fluorobenzoic Acid Samples By Schijniger Combustion
70 Fluorine Found
The following standard curve:
pH2
pH7
pH 11
13.30 13.47 13.02
13.35 13.59 13.11
13.40 13.47 13.49
expression is used to determine the value for the y = 7 + 0.11414[(3 - 2,]
where y = desired absorbance, 3 = mean absorbance for the 3.0 MICROCHEMICAL
JOURNAL,
VOL.
V, ISSUE
4
MICROQUANTITIES
OF FLUORINE
623
TABLE VI Statistical Analysis (I) Bias: For the 37 results submitted for statistical analysis the bias is zero. (2) Standard Deviation: The standard deviation of an assay is 0.255v0 fluoride. Therefore, the 95y0 confidence limits of an assay are as follows: 95oj, confidence limits
No. of determinations 1 2 3 4 5 6
f0.51% xtO.36% &O.OO~~ &0.26% f0.22% *o.al%
(3) E$ect of Sulfate: The presence of sulfate, in concentration up to 1 mg., causes an upward bias in the fluoride value. The bias is estimated to be 0.116ojo with the lower 95% confidence limits of 0.022%. (4) Standurd Curve: The fitting of the standard curve for sodium fluoride (10.95 @g./ml. F-) resulted in a linear relationship in the 20-40 fig. range. For the 37 cases involving several lots of dye, a slope of 0.11414 f 0.00251 pg./ml. was obtained. By taking the mean (j) optical density of three aliquots of a standard sodium fluoride solution (30 pg. F-), the midpoint of the line and the value of the slope, a standard curve can be obtained. Statistically, a curve determined in this manner should give greater precision.
ml. aliquot, milliliters.
0.11414 = calculated slope, and z = volume of aliquot, in
Assuming that ji = 0.655 then : ; 1 cp5; + 0.11414 (3-3) .
0.655 + 0.11414 (3-2) 0.655 + 0.11414 (1) 0.655 + 0.114 0.769
Summary A procedure based on the work of Megregian has been adapted to determine quantitatively fluorine in organic compounds, up to 20% fluorine. This procedure does not require the separation of the
624
H. J. FERRARI,
F. C. GERONIMO,
L. M. BRANCONE
fluoride ion by a time-consuming distillation. All types of compounds submitted so far have given satisfactory analysis, including those compounds containing a -CF, group. Statistical analysis of the data shows standard deviation of this method is 0.255%. The presence of sulfate, in concentration up to 1 mg., statistically demonstrates only a slight positive bias [Table VI - 31. We wish to thank R. Lamm of our Statistical evaluation of the work described in Table VI.
Laboratory
for the statistical
References 1. Ma, T. S., Micro&em. J., 2, 91 (1958). 2. Revinson, D., and J. H. Harley, Anal. Chem., 25, 794 (1953). 3. Powell, W. A., and J. H. Saylors, ibid., 25, 960 (1953). 4. Icken, J. M., and B. M. Blank, ibid., 25, 1741 (1952). 5. Price, M. J., and 0. J. Walker, ibid., 24, 1593 (1952). 6. Bumstead, H. L., and J. C. Wells, ibid., 24, 1595 (1952). 7. Batcheder, G., and V. W. Meloche, J. Am. Chem. SOL, 53, 2133 (1931). 8. Horton, A. D., P. F. Thomason, and F. J. Miller, Anal. Chem., 24, 548 (1952). 9. Clark, H. S., ibid., 23, 659 (1951). 10. Willard, H. H., and 0. B. Winters, Ind. Eng. Chem., Anal. Ed., 5,7 (1933). 11. Megregian, S., Anal. Chem., 26, 1161 (1954). 12. Belcher, R., M. A. Leonard, and T. S. West, J. Chem. Sot., 1959,3577. 13. Steyermark, A. L., R. R. Kaup, D. A. Petras, and E. H. Bass, Microchem. J., 3,523 (1959). 14. Fine, L., and E. A. Wynne, ibid., 3,515 (1959). 15. Bertolacini, R. J., and J. E. Barney, Anal. Chem., 30,202 (1958). 16. Senkowski, B. Z., E. G. Wollish, and E. G. E. Shafer, ibid., 31, 1575 (1959). 17. Schoniger, W., Mikrochim. Acta, 1955,123. 18. Elving, P. J., and W. B. Legett, Znd. Eng. Chem., Anal. Ed., 14, 499 (1942).
Received April 21, 1961
MICROCHEMICAL
JOURNAL,
VOL.
V. ISSUE
4
Calorimetric
VOL. V, PAGES 617-624 (1961)
JOURNAL
Determination
Fluorine
in Organic
of Microquantities
of
Compounds
HAROLD J. FERRARI, FRANCIS C. GERONIMO, and LOUIS M. BRANCONE, Lederle Laboratories Division, American CyarLam,id Company, Pearl River, New York
Increased interest in organic compounds containing fluorine has emphasized the need for a quantitative procedure for fluorine with the accuracy and precision required in microanalysis. This fact is substantiated by the number of papers on the subject as well as statements in a recent review by Ma.’ Our own review of the literature led us to consider various methods which for one reason or another were not suitable for our use.z--Lo At the time that we initiated our work the samples of interest were in extremely short supply and cont’ained 3-47& fluorine. These factors necessarily limited us to the use of calorimetric methods, and the most feasible one seemed to be the one described by Megregian” which he employed to determine fluorine in water or on distillates containing fluoride ions. This method stressed the features that we were seeking, such as precision, accuracy, speed, rapid and stable color development, ease of manipulation, elimination of a distillation step, and permitted one t)o work in the microgram range. In view of these considerations we chose to adapt this method to the analysis of organic compounds by the inclusion of a combustion step; originally this was a sodium fusion and lat’er the Sch6niger flask combustion technique was adopted. Since we undertook our work in 1954 some newer methods have appeared that have circumvented the drawbacks of the procedures mentioned above. BelcheF describes a method utilizing aliaarin complexone (1,2-dihydroxyanthraquino1le-S-yl-methylamine-N,N-diacetic acid). This reagent represents the first time that a chemical has been 11sedthat reacts directly with the fluoride ion to develop a 617
G18
H. J. FERRARI,
F. C. GERONIMO,
L. M. BRilNCONE
color instead of relying on the bleaching effect of the fluoride ion on a colored metal complex.* Steyermark et a1.13 employed thorium nitrate titration of the fluoride ion with sodium alizarin sulfonate as the indicator. Fine and Wynne14 use lanthanum chloroanilate for the direct calorimetric determination of fluoride ion based on the earlier work of Bertolacini and Barney. l5 Senkowski et a1.16describe a procedure using the Megregian eriochrome cyanine R calorimetric method which is similar to one we have employed in our laboratory for some time. Our procedure differs from that of Senkowski’s as follows: (1) Smaller samples can be used (0.5-1.5 mg.) ; (2) sodium peroxide is not required in the combustion step; (3) a neutralization step is not necessary; (4) smaller volumes of solution reduce the overall manipulations; (5) the precision and accuracy of our method decreases on samples containing more than 20% fluorine. A few examples of the types of compounds assayed and the results obtained are listed in Table I. TABLE I Results Selected from Analysis of Routine
Research Compounds y. fluorine
Compound Fluorinated Steroid
piperaaine
Fluorobenzene sulfonamide Piperazine trifluoracetate Fluorinated piperazine Difluorochloroacetyl Amino fluoro acid
Theory
Found
5.90 4.38 3.95 4.37 3.95 5.60 18.00 20.90 13.82 9.60
5.93 4.16 3.88 4.65 3.93 5.87 18.37 21.02 13.72 9 .80
Experimental Reagents
Sodium Fluoride : Twenty to twenty-five milligrams of reagent NaF is dried for l-2 hr. at lOO”C., then accurately weighed and dissolved in 1 liter of HzO. * This information was presented in a talk to the Metropolitan Society in New York City on February 12, 1959. MICROCHEMICAL
JOURNAL,
Microchemical VOL.
V, ISSUE
4
MICRO&UANTITIES
OF FLUORINE
619
Zirconium Chloride : Two hundred and seventy milligrams of ZrOClz.8Hz0 is dissolved in 50 ml. of H20. Then 700 ml. of concentrated HCl is added and the solution is diluted to a liter with HZO. Eriochrome Cyanine R : Dissolve 1.8 g. of ECR dye in 100 ml. HzO. Reference Acid Solution: Seven hundred milliliters of concentrated HCl is diluted to a liter with HzO. Sodium Hydroxide (2N): Eighty grams of reagent NaOH is diluted to a liter with H20. Schiiniger Sample Carriers: No. 6471-F,* Arthur H. Thomas Co. Preparation of a Standard Curve Three aliquots containing 30 pg. F-/ml. are transferred to Nessler tubes and diluted to the 50-ml. mark with HzO. Then 5.0 ml. each of ECR and ZrOCls are added to each tube and the tubes are shaken well. The reference solution contains 50 ml. Hz0 plus 5.0 ml. of each ECR and HCl. The solutions are allowed to stand before reading to attain room temperature, and then read at 528 rnp using a Beckman DU Spectrophotometer. The average of these three aliquots is used to calculat,e the absorbance at 20 and 40 pg. concentrations (Table VI-4).
Analysis of an Unknown The following weight of sample is taken for the different percentages of fluorine : Weight, mg. “% o-5 5-20
1.0-1.5 0.5-1.0
A suitable weight of sample is transferred to a Schaniger” filter paper carrier and folded to fit the platinum grid of the Schijniger stopper. The flask containing 4 ml. of 2N NaOH is flushed with a stream of oxygen for 10-20 sec. The stem of the filter paper, contained in the platinum grid, is ignited and placed into the flask to complete the combustion in the usual manner. The contents of the SchGniger flask are transferred directly to the Nessler tube and diluted to the 50-ml. mark with HzO. If the * Fluoride
free.
G’LO
H. J. E’ERRARI,
F. C. GEIWNIMO,
L. M1. 1~11ANCONE
fluoride content exceeds 50 pg., then the contents are transferred to a loo-ml. volumetric flask made up to volume and an aliyuot is taken to obtain a content between 30-50 Mg. The color complexing reagents are added and the optical density determined spectrophotometrically using a Beckman DU. The concentration is obtained by referring to the standard curve.
Calculation :
where C = concentration obtained from standard curve, L, = dilut,ion factor, and X = sample weight.
Discussion Combustion Techniques. Prior to the introduction of the Schiiniger Flask combustion, the samples were heated with metallic sodium18 in a sealed Carius t’ube at 400°C. for 1 hr. The excess sodium is destroyed by dropwise addition of methanol. After all the sodium is destroyed, the content,s of the tube are quantitatively transferred by filtration into a lOO-ml. volumetric flask and diluted to the mark with H,O. A suitable aliquot is taken and the procedure for the color reaction is then followed as previously described. The overall time for sample preparation, combustion, and filtration by the sodium fusion requires approximately 21/2 hr. A filtration is always necessary to remove the carbonaceous residue. The SchGniger combustion requires 15-20 min. and the final solution is always clear, eliminating the need for filtration. TABLE II Standard Samples by Sodium Fusion and Schiiniger Combustion Techniques NO.
1 2 3 4 5 6
-
p-Fluorobenzoic acid (13.56% F) Na fusion Schijniger 13.88 13.74 13.37 13.10 13.57 13.53 MICROCHEMICAL
13.89 13.94 13.68 13 25 13.55 13.97 JOURNAL,
VOL.
V, ISSUE
4
MICROQUANTITIES
621
OF FLUORINE
Table II lists standard samples of p-fluorobenzoic acid combustion by the sodium fusion and the Schijniger combust,ion techniques.
Effect of Sulfate Using ECR (Geigy) the statistical data [Table VI, (3)] shows a slight positive bias when SO,--- is present in concentration up to I mg. Generally, the presence of SO,-- requires a separation by a Willard and Winters distillation. I0 However, the results obtained in Table III with t)his sulfate concent,ration are well within the allowable limits and require no addit.ional treatment for the removal of SO,--. TABLE III Effect of Sulfate Sample No.
Cont. SOa, mg.
Theory
Found
1 2 3 4 5
1.0 1.0 0.7 0.7 0.5
5.90 7.40 6.00 5.60 6.02
5.81 7.42 6.13 5.92 6.20
The presence of phosphate ions also interferes as reported by Megregian. l l Although these ions result in correspondingly higher fluoride values, this type of interference is not encountered as frcquently as the sulfate one. If the phosphate concentration is higher than the tolerance reported by Megregian a distillat’ion step as recommended by him will obviate this difficulty.
Effect of Temperature Megregian recommends that the reaction be carried out in the range of 22-28’C. and that the standard curve and the sample be read within ~2%. of each other. Temperature control is a very critical factor with some spectrophotometers. The instrument used in this work originally had a cell compartment temperature of 3% 35’C. Baffles were installed along the sides of the compartment to act as air condensers which reduced the temperature to about 26’C. Readings are taken over a IO-min. period until a constant optic&al density, within the limits of the instrument, is obtained.
622
H. J. FERRARI,
F. C. GERONIMO,
L. M. BRANCONE
Effect of pH on the Color Reaction The pH of the standard NaF solution is in the vicinity of while the solution following the Schijniger combustion is in the of pH 11. Three aliquots of standard NaF solution were run in the manner at pH 7, and three were adjusted to pH 11 with NaOH to the addition of the color-forming reagents. The results are in Table IV.
pH 7 range usual prior listed
TABLE IV Effect of pH on the Color Reaction for Standard NaF Solutions Cont. pg. NaF STD solutions
Cont. pg. at pH7
Cont. pg. at pH 11
30.00 40.00 50.00
30.20 39.91 50.62
30.30 39.90 50.25
Nine samples of p-fluorobenzoic acid were combusted by the Schiiniger Flask Technique using 4 ml. of 2N NaOH as the absorber. In three samples the pH was not adjusted (pH 11) ; three were adjusted to pH 7, and three were adjusted to pH 2 with HCl. Then the color-forming reagents were added and the results are listed in Table V. TABLE V Effect of pH on the Color Reaction for p-Fluorobenzoic Acid Samples By Schijniger Combustion
70 Fluorine Found
The following standard curve:
pH2
pH7
pH 11
13.30 13.47 13.02
13.35 13.59 13.11
13.40 13.47 13.49
expression is used to determine the value for the y = 7 + 0.11414[(3 - 2,]
where y = desired absorbance, 3 = mean absorbance for the 3.0 MICROCHEMICAL
JOURNAL,
VOL.
V, ISSUE
4
MICROQUANTITIES
OF FLUORINE
623
TABLE VI Statistical Analysis (I) Bias: For the 37 results submitted for statistical analysis the bias is zero. (2) Standard Deviation: The standard deviation of an assay is 0.255v0 fluoride. Therefore, the 95y0 confidence limits of an assay are as follows: 95oj, confidence limits
No. of determinations 1 2 3 4 5 6
f0.51% xtO.36% &O.OO~~ &0.26% f0.22% *o.al%
(3) E$ect of Sulfate: The presence of sulfate, in concentration up to 1 mg., causes an upward bias in the fluoride value. The bias is estimated to be 0.116ojo with the lower 95% confidence limits of 0.022%. (4) Standurd Curve: The fitting of the standard curve for sodium fluoride (10.95 @g./ml. F-) resulted in a linear relationship in the 20-40 fig. range. For the 37 cases involving several lots of dye, a slope of 0.11414 f 0.00251 pg./ml. was obtained. By taking the mean (j) optical density of three aliquots of a standard sodium fluoride solution (30 pg. F-), the midpoint of the line and the value of the slope, a standard curve can be obtained. Statistically, a curve determined in this manner should give greater precision.
ml. aliquot, milliliters.
0.11414 = calculated slope, and z = volume of aliquot, in
Assuming that ji = 0.655 then : ; 1 cp5; + 0.11414 (3-3) .
0.655 + 0.11414 (3-2) 0.655 + 0.11414 (1) 0.655 + 0.114 0.769
Summary A procedure based on the work of Megregian has been adapted to determine quantitatively fluorine in organic compounds, up to 20% fluorine. This procedure does not require the separation of the
624
H. J. FERRARI,
F. C. GERONIMO,
L. M. BRANCONE
fluoride ion by a time-consuming distillation. All types of compounds submitted so far have given satisfactory analysis, including those compounds containing a -CF, group. Statistical analysis of the data shows standard deviation of this method is 0.255%. The presence of sulfate, in concentration up to 1 mg., statistically demonstrates only a slight positive bias [Table VI - 31. We wish to thank R. Lamm of our Statistical evaluation of the work described in Table VI.
Laboratory
for the statistical
References 1. Ma, T. S., Micro&em. J., 2, 91 (1958). 2. Revinson, D., and J. H. Harley, Anal. Chem., 25, 794 (1953). 3. Powell, W. A., and J. H. Saylors, ibid., 25, 960 (1953). 4. Icken, J. M., and B. M. Blank, ibid., 25, 1741 (1952). 5. Price, M. J., and 0. J. Walker, ibid., 24, 1593 (1952). 6. Bumstead, H. L., and J. C. Wells, ibid., 24, 1595 (1952). 7. Batcheder, G., and V. W. Meloche, J. Am. Chem. SOL, 53, 2133 (1931). 8. Horton, A. D., P. F. Thomason, and F. J. Miller, Anal. Chem., 24, 548 (1952). 9. Clark, H. S., ibid., 23, 659 (1951). 10. Willard, H. H., and 0. B. Winters, Ind. Eng. Chem., Anal. Ed., 5,7 (1933). 11. Megregian, S., Anal. Chem., 26, 1161 (1954). 12. Belcher, R., M. A. Leonard, and T. S. West, J. Chem. Sot., 1959,3577. 13. Steyermark, A. L., R. R. Kaup, D. A. Petras, and E. H. Bass, Microchem. J., 3,523 (1959). 14. Fine, L., and E. A. Wynne, ibid., 3,515 (1959). 15. Bertolacini, R. J., and J. E. Barney, Anal. Chem., 30,202 (1958). 16. Senkowski, B. Z., E. G. Wollish, and E. G. E. Shafer, ibid., 31, 1575 (1959). 17. Schoniger, W., Mikrochim. Acta, 1955,123. 18. Elving, P. J., and W. B. Legett, Znd. Eng. Chem., Anal. Ed., 14, 499 (1942).
Received April 21, 1961
MICROCHEMICAL
JOURNAL,
VOL.
V. ISSUE
4