摘要:

ANALYST, SEPTEMBER 1986, VOL. 111 1099 Titrations in Non-aqueous Media Part II.* Basicity Order of Aliphatic Amines in Nitrobenzene Solvent Turgut Gunduz,t Necld Gunduz, Esma Kiliq, Adnan Kenar and Gulay Getinel Department of Chemistry, Faculty of Science, University of Ankara, Ankara, Turkey The relative basicity order of methyl-, ethyl-, propyl- and butylamines has been determined potentiometric- ally with perchloric acid in nitrobenzene solvent and found to be R3N > R2NH > RNH2 > NH3, where R = Et, n-Pr or n-Bu. However, for the methylamines, the order is Me2NH 2 Me3N > MeNH2 > NH3. The orders in primary, secondary and tertiary amines are EtNH, > MeNH2 > n-PrNH2 > n-BuNH2 > NH3; Et2NH > Me2NH > n-Pr2NH > n-Bu2NH > NH,; and Et3N > n-Pr3N 3 n-Bu3N > Me3N > NH3.These results show that, in general, an increase in the number of alkyl groups increases the basicity of the amine, and that an increase in the size of the alkyl group decreases the basicity. n-Butylamine is a stronger base than branched-chain primary butylamines. Keywords : Non-aqueous titration; potentiometric titration; amines; nitrobenzene solvent; basicity order The basicity orders of amines have been a source of considerable confusion for many years,1-12 as there are many factors which influence basicity. The factors influencing the basicities of aliphatic amines are relatively limited, although the most significant factors, such as molecular properties and solvent effects, are still operative. In the work reported in this paper, the basicities of aliphatic amines have been determined in nitrobenzene solvent by potentiometric titration with perchloric acid, one of the strongest non-aqueous media acids available.Four different series of aliphatic amines have been titrated with perchloric acid, namely methyl-, ethyl-, n-propyl- and n-butylamine. In addition to these, isopropylamines and some branched-chain butylamines have also been titrated. All the amines showed good S-shaped potential vs. mequiv. acid or mequiv. base (milliequivalent of acid or milliequivalent of base) titration graphs. An example of the titration graphs for n-butylamines is given in Fig. 1. Q 0.0 1 .o 2.0 Mequiv. acidhequiv. base Fig. 1. Potentiometric titration graphs of n-butylamines with per- chloric acid in nitrobenzene. A, n-BuNH,; B, n-Bu,NH; and C, n-Bu,NH * For Part I of this series, see Analyst, 1986, 111,949.t To whom correspondence should be addressed. As is evident from the shapes of the titration graphs, no homo-conjugation reactions took place during the titra- tions.1.2 This indicates that nitrobenzene is a good solvent for ionic organic compounds. Half-neutralisation potentials have been determined from the titration curves. As the half-neutralisation potentials of the amines are slightly concentration dependent (we have carried out a number of experiments in this area), the titrations were carried out with dilute solutions (0.001 M). Also, in order to minimise the errors that would originate from the dilution of solutions during titrations, 0.034 M perchloric acid was used.The end-points were reached after the addition of about 0.5 ml of acid solution. This amount of acid solution allowed at least fifteen readings to be taken before the end-point of the ti tration was reached. Half-neutralisation potentials of the amines versus the number of alkyl groups on the amines have been plotted in Fig. 2 . It can be seen that there is a fairly good correlation between the basicity of amines and the number of alkyl groups in the amine series, with the exception of the methyl series. Ethylamines are the most basic compounds of the amines. Isopropylamine and branched-chain butylamines are not included in Fig. 2 . Another set of experiments was performed in a nitroben- zene - light petroleum (1 + 3) system. All the experiments were repeated under identical conditions and almost the same series order was found.The anomaly observed in the methylamine series remained unchanged. > E a' z I 40 20 10 -10 - 20 B 0 1 2 3 No. of alkyl groups I I I I Fig. 2. Half-neutralisation potentials of the aliphatic amines in nitrobenzene versus number of alkyl groups. A, Methyl; B, ethyl; C , n-propyl; and D, n-butyl1100 ANALYST, SEPTEMBER 1986, VOL. 111 Experimental Apparatus and Chemicals Potentiometer and accessory. An Orion Model 801 A digital pH meter equipped with glass and calomel electrodes was used throughout this work. The saturated KCl solution of the calomel electrode was removed and the electrode washed several times with anhydrous methanol. After drying, the electrode was then filled with saturated KCl solution in non-aqueous methanol.A pressure of 20 mmHg was applied to the solution in the calomel electrode in order to prevent the diffusion of the solution into the electrode. After each titration the electrode was washed twice with anhydrous methanol to remove nitrobenzene solution from the surface of the electrodes. Pure anhydrous methanol dries easily without leaving any stains. Before using again, electrodes were dipped into pure nitrobenzene solvent to remove any traces of methanol. A magnetic stirrer was used in the titrations and titrations were carried out in a 50-ml beaker wound with copper wire. The copper wire and all other electrical equipment were earthed. A semi-microburette, which could be read to 0.01 ml, was used for the titrations.Nitrobenzene. Nitrobenzene (Merck) was used after purifi- cation in the following way: 10 g of P2O5 were introduced into 11 of nitrobenzene. After shaking, the mixture was left overnight and then distilled twice at reduced pressure by the aid of a suction pump equipped with a liquid air-cooled trapper. The solvent prepared in this way was straw-yellow and its refractive index was 1.5513. Purified nitrobenzene is a fairly good solvent for molecular and some ionic compounds. It has a large titration interval extending from -700 mV (basic side) up to +800 mV (acidic side). Perchloric acid solution. Anhydrous 0.034 M perchloric acid solution was used in all the titrations. This was prepared by taking 0.072 ml of 70% perchloric acid (Merck) with a micro-pipette and adding this dropwise to 5 ml of ice-cooled pure acetic anhydride.At higher temperatures, a vigorous reaction takes place and a dark brown solution is obtained instead of a light yellow solution. The resulting light yellow solution was left for 5-6 h at room temperature, and then 1.00 ml of solution was taken from it and introduced into a 50.0-ml calibrated flask before being diluted to 50.0 ml by the addition of nitrobenzene. The concentration of the final solution was determined against a primary standard, diphenylguanidine , and was found to be 0.034 M. This solution was stable for 3-4 months, if kept under refrigeration in a dark flask. Amines. The amines used were all of analytical-reagent grade. Diethylamine was obtained from Riedel de Haen and the others from BDH Chemicals.Methylamines were pre- pared from their hydrochlorides. Each hydrochloride was treated with aqueous sodium hydroxide and the gas evolved was passed over dry NaOH and then introduced directly to the solvent. Amine solutions were titrated immediately after prepara- tion. Results and Discussion Until now, no simple explanation of the basicity orders of aliphatic amines has been given.2.4-17 This is probably because of the number of factors that influence the basicity of the amines. Potentiometric titrations of ammonia solution and aliphatic amines with perchloric acid in nitrobenzene have shown some interesting and unexpected relative basicity orders: Et3N > Et2NH > EtNH2 > NH3; n-Pr3N > n-Pr2NH > n-PrNH2 > NH3; n-Bu3N > n-Bu2MH > n-BuNH2 > NH3.These relative basicity orders are identical with the orders found by other workers in the gas phase.5JlJ2J5,18 (It is very difficult to give a theoretical explanation of these similarities, because one set of experiments were carried out in the gas phase and the other set of experiments were carried out in the condensed phase. In the gas phases intrinsic electronic factors affect the basicity without the interference of the solvent.) There are also interesting orderings among the primary, secondary and tertiary amines, although these orderings are in conflict with the results of other worker~5?7-’~: EtNH, > n-PrNH2 > n-BuNH2 > NH,; Et2NH > n-Pr2NH > n-Bu2NH > NH,; Et3N > n-Pr3N 2 n-Bu3N > NH3.For the methylamine series, a different order was found: Me2NH > Me3N > MeNH2 > NH3. This order unexpectedly parallels the order found in water by Brown.4 In water there are two main opposing effects influencing the basicities of the amines, namely hydration and inductive effects. The hydra- tion effect decreases with an increase in the number of alkyl substitutions, whereas the inductive effect increases with an increase in the number of alkyl substitutions. However, in nitrobenzene solvent , this explanation is not applicable. The order determined for the methylamines disagrees with the findings of Benoit and co-workers in dimethyl sulph- oxide .9JO The relative basicity orders of primary, secondary and tertiary amines, including methylamines, are as follows: EtNH2 > MeNH2 > n-PrNH2 > n-BuNH2 > NH3; Et2NH > Me2NH > n-Pr2NH > n-Bu2NH > NH,; Et3N > n-Pr3N > n-Bu3N > Me3N > NH3.The extended primary and secondary amines, including isopropylamine and branched-chain butylamines, give the following orders: EtNH2 > MeNH2 > iso-PrNH2 > n-PrNH2 > n-BuNH2 > sec-BuNH2 > tert-BuNH, > iso-BuNH2 > NH3; Et2NH > Me2 NH > n-Pr2NH > n-Bu2NH > iso-Pr2NH > NH3. Unfortunately, a good theoretical explanation as to why ethylamines are stronger bases than their methyl anal- ogues has not been found. Conclusions From the investigations described above, the following conclusions can be drawn. (1) F-strain seems to be very likely because any ethylamine is a stronger base than its propyl and butyl analog~es.4~16~19 EtNH2 > PrNH2; Et2NH > Pr2NH; Et3N > Pr3N.Identical orderings hold true for butylamines. (2) B-strain is not observed in this work because tri-n- propylamine is more basic than n-propylamine. The same sequence is true also for tri-n-butylamine and n-butylamine. (3) Basicity decreases with increase in size of the alkyl group, with the exception of methylamines. This finding is the opposite of findings reported in the literat~re.7,~’2 (4) n-Butylamine is more basic than the branched-chain butylamines. This is also in disagreement with data in the literature.7JC-12 (5) It is concluded that the order of basicities of amines may be entirely opposite when the titrations are carried out in different media.7-’2.19 1. 2.3. 4. 5. 6. 7. 8. 9. References Fritz, J. S., “Acid - Base Titrations in Non-aqueous Solvents,” Allyn and Bacon, Boston, 1973. Streuli, C. A., Anal. Chem., 1958, 30, 997; 1959,31, 1652. Feakins, D., Last, W. A., and Shaw, R. A., J. Chem. SOC., 1964, 2387. Brown, H. C., J. Am. Chem. SOC., 1945, 67, 374 and 378. Munson, M. S., J. Am. Chem. SOC., 1965, 87, 2332. Clark, J., and Perrin, D. D., Q. Rev. Chem. Soc., 1964, 18, 295. Dzidic, I., J. Am. Chem. SOC., 1972, 94, 8333. Reyes, A., and Scott, R. M., J. Phys. Chem., 1980,84, 3600. Mucci, A., Domain, R., and Benoit, R. L., Can. J. Chem., 1980,58, 953.ANALYST, SEPTEMBER 1986, VOL. 111 1101 10. Benoit, R. L., Mackinnon, M. J., and Bergeron, L., Can. J. Chem., 1981,59, 1501. 11. Brauman, J. I., and Blair, L. K., J. Am. Chem. SOC., 1968,90, 5636 and 6561. 12. Brauman, J. I., and Blair, L. K., J. Am. Chem. SOC., 1971,93, 3911 and 3914. 13. Brown, H. C., and Cahn, A , , J. Am. Chem. SOC., 1950, 72, 2939. 14. Brown, H. C., and Kanner, B., J. Am. Chem. SOC., 1966,88, 986. 15. Kebarle, P., Annu. Rev. Phys. Chem., 1977, 28, 445. 16. 17. 18. 19. Brown, H. C., Krishnamurthy, S . , and Hubbard, J. L., J . Am. Chem. SOC., 1978, 100, 3343. Marsh, J., “Advanced Organic Chemistry,” Wiley, New York, 1985. Lau, Y. K., Saluja, P. P. S., Kebarle, P., and Alder, R. W. J., J . Am. Chem. SOC., 1978, 100,7328. Gunduz, T., and Kiliq, E., unpublished results. Paper A6154 Received February 19th, 1986 Accepted March 3rd, 1986

ISSN:0003-2654    

DOI:10.1039/AN9861101099

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1986, VOL. 111 1103 Titrations in Non-aqueous Media Part Ill.* Basicity Order of Aniline, N-Alkyl- and N-Aryl-substituted Anilines and Pyridine in Nitrobenzene Solvent Turgut Gunduz,t Necli Gunduz, Esma Kilq and Adnan Kenar Department of Chemistry, Faculty of Science, University of Ankara, Ankara, Turkey The relative basicity order of ammonia, pyridine, aniline and N-methyl-, N,N-dimethyl-, N-ethyl-, N,N-diethyl-, N-aryl- and N,N-diaryl-substituted anilines have been determined potentiometrically with perchloric acid in nitrobenzene solvent and found to be NH3 > Py > PhNEt2 > PhNMe2 > PhNHEt > PhNHMe > PhNH2 > Ph2NH > Ph3N. This order in general conflicts with the results observed by other workers in either the gas phase or in the condensed phase.N-Alkyl substitution increases the basicity of the aniline, and N-aryl substitution decreases its basicity. Moreover, the number and size of the substituent influence the basicity of aniline. N-Ethyl-substituted anilines are more basic than the corresponding N-methyl-substituted anilines. The position of pyridine in the order is surprising and difficult to interpret. Keywords: Non-aqueous titration; potentiometric titration; anilines; nitrobenzene solvent; basicity order It is well known that two main effects influence the acidity or basicity of molecules, namely, structural and solvent (medium) effects.1.2 Unfortunately, in most molecules, there are two or more structural effects and it is usually difficult to decide how much each contributes to the acidity or basicity of the molecules.Small differences in acidity or basicity between similar molecules are also extremely difficult to interpret , and one must be very careful in deciding which structural effect is the main influence on the acidity or basicity. Solvent or medium effects are also very important, and the acidity or basicity of a molecule usually varies when its solvent is changed. For example, the basicity orders of n-butylamines against the Bronsted acids are Bu3N > BuzNH > BuNH2 in chlorobenzene solvent,3 Bu2NH > Bu3N > BuNH2 in benzene solvent3 and BUN& > Bu2NH > Bu3N in cyclohex- ane solvent.4 Hence a change of solvent may completely reverse the basicity order. The relative basicity orders of N-alkylated and N-arylated anilines , including pyridine, have been determined in differ- ent solvents or media,5-7 but have not as yet been determined in nitrobenzene solvent.In this work, the relative basicity orders of ammonia and eight amines have been determined potentiometrically with perchloric acid in nitrobenzene sol- vent. The amines titrated were pyridine (Py), aniline (PhNH2) , N-methylaniline (PhNHMe) , N, N-dimethylaniline (PhNMe2) , N-ethylaniline (PhNHEt), N, N-diethylaniline (PhNEt,), diphenylamine (Ph2NH) and triphenylamine (Ph3N). Titration graphs of these are given in Fig. 1. As is evident from the titration graphs, no homoconjugation reaction took place during the titrations and all but diphenyl- and triphenylamine gave good S-shaped potential vs. mequiv. acid or mequiv.base graphs. Half-neutralisation potentials of the amines have been determined by means of the graphs. Half-neutralisation potentials of the diphenyl- and triphenyl- amines, which did not give proper titration graphs, have been determined stoicheiometrically, i. e., the volumes of the titrant acid needed to reach the equivalence points have been calculated from the milliequivalent numbers of the titrated samples, and then the potentials at the half-volumes of the acid used have been taken as half-neutralisation potentials. As the half-neutralisation potentials are slightly concentra- tion dependent, titrations have been carried out on solutions with identical concentration, and also on dilute solutions (0.001 ~ ) . 8 , 9 In order to minimise the errors that might arise from the dilution of the solutions during the titrations, 0.034 M perchloric acid was used.* For Part 11 of this series, see p. 1099. t TO whom correspondence should be addressed. -100 0 100 200 > 300 E 400 500 600 700 800 0.0 1 .o Mequiv. acid/mequiv. base Fig. 1. Potentials versus mequiv. aciddmequiv. base. Base: A, ammonia; B, pyridine; C, N,N-diethyianiline; D, N,N-dimethylani- line; E, N-ethylaniline; F, N-methylaniline; G, aniline; H, diphenyl- amine; and I, triphenylamine Experimental Apparatus All apparatus used was as under Potentiometer and accessory in Part 11, and the electrode was washed and filled in an identical manner. Chemicals Nitrobenzene and perchloric acid were prepared and stored as described in Part 11. Ammonia. Ammonia was generated from NH&l (Merck, Pure).1104 ANALYST, SEPTEMBER 1986, VOL.111 Pyridine. Pyridine was purchased from Merck (Pure) and was used without further purification. Aniline and N-rnethyluniline. Aniline and N-meth ylaniline were purchased from Riedel de Haen (Pure) and were used without further purification. N,N-DiethyZuniline. N, N-Diethylaniline was obtained from Riedel de Haen (fur Analyse) and was distilled twice under vacuum before use. N , N- Dirnethy luniline. N, N-Dime t h ylaniline was purchased from Fluka (Puriss) and was used without further purification. Diphenylamine. Diphenylamine was purchased from BDH Chemicals (Indicator) and used without further purification. Triphenylurnine. Triphenylamine was purchased from BDH Chemicals (GPR) and used without further purification. All amines and ammonia solutions were titrated immedi- ately after preparation. Results and Discussion It is generally held that the relative basicity order of amines in a series does not change with a change of Bronsted acid titrant in the same solvent because the proton itself is too small to cause any appreciable steric hindrance.10 Therefore, the differences observed in the relative basicity order of the same series, titrated with different Bronsted acids in different solvents, can be attributed to the change of the solvent. For this reason, when comparing the relative order of the amines in a series, only the change of solvent is taken into account. As can be seen from the titration graphs obtained in nitrobenzene solvent given in Fig.1, ammonia is more basic than the eight amines titrated in this work, and is followed by pyridine. Including ammonia, the over-all order of the amines is NH3 > Py > PhNEt, > PhNMe2 > PhNHEt > PhNHMe > PhNH2 > Ph2NH > Ph3N (I). All N-alkyl-substituted anilines are more basic and all N-aryl-substituted anilines are less basic than aniline. More useful relative basicities can be extracted from sequence (I) above: PhNMe2 > PhNHMe > PhNH2 (11); (IV); Py > PhNMe2 > PhNHMe (V); and NH3 > Py > PhNH2 WI). As is evident from Fig. 1, diphenylamine and triphenyl- amine do not give clear end-points. The order (I) shows that N,N-diethylaniline is a stronger base than N-ethylaniline and N, N-dimethylaniline is a stronger base than N-methylaniline in nitrobenzene solvent. Moreover, N-ethyl-substituted anilines are more basic than their N-methyl-substituted aniline analogues.This means that an increase in the number or in the size of an alkyl group increases the basicity of the aniline. This is in good agreement with the results found by Brauman and co-workers in the gas phase with other compounds.5,6Jl The order (11) disagrees with the order PhNH2 > PhNHMe > PhNMez found by Benoit et ul. in dimethyl sulphoxide solvent.’ In addition, the order (V) also disagrees with the order PhNH2 > Py > PhNHMe > PhNMe2 found by the same workers.’ Moreover, sequence (V) is also at variance with the order PhNMe2 > Py > PhNHMe > PhNH2 observed by other workers in the gas phase,12J3 and the order (IV) does not fit the order Ph3N > PhNH2 obtained by others in the gas phase.SJ4 According to Dzidic,s the phenyl group is electron- donating relative to the proton in the gas phase, whereas it is electron-attracting relative to a saturated system.On the other hand, the order (V) is consistent with the order Py > PhNH2 observed in the gas phase by other investigators.5J2.13 As is evident from order (I), pyridine is more basic than even N,N-dialkyl-substituted anilines, which are expected to be highly basic.15-17 Hence, pyridine acts in nitrobenzene as if it was in the gas phase. This is a surprising observation, because the general belief is that the sp3 hybrid orbital is more basic than the sp2 hybrid orbital. As the nitrogen atom in PhNEt2 > PhNHEt > PhNH2 (111); PhNH2 > Ph2NH > Ph3N \o PhNHEt 1 I t PhNEt, o Y 0 2 4 6 8 1 0 1 2 No.of H atoms Fig. 2. Half-neutralisation potentials of amines versus number of hydrogen atoms pyridine is sp2 hybridised, it should show a lower basicity than aniline, which is sp3 hybridised. The higher basicity of pyridine relative to aniline in the gas phase can be interpreted as intrinsic basicity (in the absence of solvent effects), but the same property observed in nitroben- zene is very difficult to interpret. This is because nitrobenzene is not an inert solvent, and yet it has no similarity with the gas phase. It has a dielectric constant of 36. Hence, the gas-phase basicities of the amines may not be diagnostically useful in studying the basicities of the com- pounds.The order (VI) is the reverse of the result Py > NH3 found by Dzidic in the gas phase.5 The order between pyridine and aniline in dimethyl sulphoxide is in the opposite sense (PhNH2 > Py) to that in nitrobenzene solvent. This is another unexpected result, as dimethyl sulphoxide and nitrobenzene solvents are not at first sight so different in character as to reverse the order of basicity. Finally, another surprising result is the regular increase in basicity of the anilines with the number and the size of N-alkyl substitutions, e.g., PhNEt, > PhNMe2 > PhNHEt > PhNMe > PhNH2. In this series, if the number of hydrogens in aniline is arbitrarily taken to be zero, then the number of hydrogens in N-methyl- , N-ethyl- , N, N-dimethyl- and N, N-diethylanilines becomes 3, 5, 6 and 10, respectively.When the number of hydrogen atoms is plotted versus the half-neutralisation potentials of the amines, a nearly straight line is obtained (Fig. This relationship is very difficult to explain. It is as if each carbon-hydrogen bond gives a small part of its electron density to the nitrogen atoms of the amine. An increase in basicity implies a greater polarisability of the lone pair of electrons on the nitrogen atom, and a greater polarisability means that the lone pair of electrons on nitrogen is more easily donated. This results in a stronger attraction of the proton, and hence a greater basicity. 2) * We express our sincere thanks for the valuable assistance of Dr. Ziya K i l i ~ who helped us in writing the manuscript and in drawing the graphs.References 1. 2. 3. 4. Taft, R. W., Prog. Phys. Org. Chem., 1983, 14, 247. Hine, J . , “Structural Effects on Equilibria in Organic Chem- istry,” Wiley, New York, 1975. Boyles, J. W., and Taylor, A. F., J. Chem. SOC., 1961, 417. Giindiiz, T., and Kiliq, E . , unpublished results.ANALYST, SEPTEMBER 1986, VOL. 111 5. 6. 7. 8. 9. 10. 11. Dzidic, I., J. Am. Chem. SOC., 1972, 94, 8333. 12. Mucci, A., Domain, R., and Benoit, R. L . , Can. J. Chem., 13. 1980,58, 953. Benoit, R. L., Mackinnon, M. J., and Bergeron, L., Can. J . 14. Chem., 1981, 59, 1501. 15. Feakins, D., Last, W. A., and Shaw, R. A., J . Chem. SOC., 16. 1964,2387. Fritz, J., “Acid - Base Titrations in Non-aqueous Solvents,” 17. Allyn and Bacon, Boston, 1973. Brown, H. C . , Krishnamurthy, S., and Hubbard, J. L., J. Am. Chem. SOC., 1978, 100, 3343. Reyes, A., and Scott, R. M., J. Am. Chem. SOC., 1980, 84, 3600. 1105 Kebarle, P., Annu. Rev. Phys. Chem., 1977,28,445. Lau, Y. K., Saluja, P. P. S., Kebarle, P., and Alder, R. W. J., J. Am. Chem. SOC., 1978, 100,7328. Ikuta, S., and Kebarle, P., Can. J . Chem., 1983, 61, 97. Munson, M. S . , J . Am. Chem. SOC., 1965, 87, 2332. Brauman, J . I., and Blair, L. K., J . Am. Chem. SOC., 1968,90, 5636. Brauman, J. I., and Blair, L. K., J. Am. Chem. SOC., 1971, 93, 3911 and 3914. Paper A6155 Received February 19th, I986 Accepted March 3rd, I986

ISSN:0003-2654    

DOI:10.1039/AN9861101103

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

ANALYST, SEPTEMBER 1986, VOL. 111 1107 Problems in the Dissolution of Silicates by Acid Mixtures Celia Maqueda and Jose Luis Perez Rodriguez Centro de Edafologr& y Biologl& Aplicada del Cuarto, Apartado 1052, Seville, Spain and Angel Justo Departamento de Qulinica Inorganica, Facultad de Farmacia, Apartado 874, Seville, Spain The decomposition of silicate rocks using mixtures of mineral acids has been studied. The conventional acid method of dissolving rocks with hydrofluoric - perchloric - nitric acid mixtures is unsatisfactory when pyrophyllite is present. This mineral is not destroyed by acid attack, whereas other silicates such as mica, kaolinite, quartz, feldspars, smectite and interstratified illite - smectite are decomposed. If the acid attack is carried out in a pressure vessel, pyrophyllite is dissolved completely, but with more difficulty than the other silicate minerals present.Keywords : Pyroph yllite; silicate dissolution; acid mixtures One of the main concerns of silicate analysis over the years has been the development of a procedure to decompose the silicate minerals. Conventional methods used are based on the use of acids or fusion techniques. Various workersl-4 have described schemes for the total decomposition of silicates using a hydrofluoric - perchloric - nitric acid mixture. Clays are composed mainly of silicate minerals and are usually easily decomposed by this mixture of acids. However, we have found that when pyrophyllite is present in a clay, dissolution is incomplete and a white residue is left after reaction.Similar problems occur when the samples are attacked with a hydrofluoric - sulphuric - nitric acid mixture. In this work we studied the decomposition of clay samples by acid mixtures when pyrophyllite is present in varying proportions. Experimental Methods of Acid Attack Method I Samples were treated as described by Bennett et aZ.5 Weigh 0.250 g of the finely ground samples, add 5 ml of HN03 (1 + 4), 5 ml of HC104 (1 + 4) and 10 ml of HF (40% mlm) and evaporate to dryness. Cool the residue, add 5 ml of HC104 (1 + 4) and evaporate to dryness again. To the cool, dry residue, add 1-2 ml of HCl (37% mlm) and distilled water (approximately 25 ml) and warm. Cool, centrifuge, filter and wash several times with distilled water. Determine the different elements in solution by atomic absorption spec- trometry.Method 2 Transfer 0.20 g of finely ground samples into a PTFE-lined bomb, add 0.25 ml of HN03 (65%), 0.75 ml of HCl (37%) and 5 ml of HF (40% mlm) and heat at 50,100,125 and 140 "C for 60 min each. Cool to room temperature, dilute with distilled water, add 5 g of H3B03 and heat at 60 "C in a plastic beaker until the sample has dissolved. Dilute the sample to 250 ml in a plastic flask with distilled water. Silicate Analysis Phosphorus was determined by the spectrophotometric method of Murphy and Riley6 and the other elements present were determined by atomic absorption spectrometry. Mineralogy The mineralogical composition of the samples was determined using a Siemens X-ray diffractometer with Cu Ka radiation.Results and Discussion The major minerals present in the samples as deduced by X-ray diffraction are pyrophyllite, mica, kaolinite, feldspars and rutile; some quartz, smectite and interstratified mica - smectite are also present. The samples, after treatment with HF - HN03 - HC104 acid mixtures, were not completely dissolved as is usual in clay minerals, and a white residue was left that did not dissolve even after several treatments. It is evident from these results that the triacid treatment does not completely dissolve these particular samples. The concentrations of the elements liberated by this method are shown in Table 1. Table 1. Results of chemical analysis. A, Raw materials attacked by digestion bomb; B, raw materials attacked by HN03 - HC104 - HF mixture; and C, residues of B dissolved in the digestion bomb.Results quoted as percentage of the total mass of the sample Sample 1 Sample 2 Element (quoted as oxide) A B C A B C Si02 . . . . . . 54.79 A1203 . . . . . . 33.13 Fe203 . . . . . . 0.23 Ti02 . . . . . . 1.25 CaO . . . . . . 0.26 MgO . . . . . . 0.25 Na20 . . . . . . 0.78 K2O . . . . . . 2.76 P205 . . . . . . 0.15 Lossonignition . . 5.93 - 65.50 21.26 28.09 0.23 - 0.10 6.02 0.25 - 0.25 - 0.76 - 2.75 - 0.14 - 90.22 4.73 0.86 0.69 0.93 0.07 0.10 0.27 0.02 1.95 - - 3.36 67.68 0.80 29.05 0.05 3.15 0.93 - 0.07 - 0.10 - 0.27 - 0.02 - Total . . . . . . 99.53 99.841108 ANALYST, SEPTEMBER 1986, VOL. 111 After the original samples and the residues from the acid method had been attacked in a digestion bomb at 140 "C for 60 min, the dissolutions were complete in all instances.The total element concentrations and the proportions of elements dissolved by the acid mixtures are shown in Table 1. The mineralogical composition of the two samples in Table 1 are different. Sample 1 is composed of pyrophyllite (40%), mica (52%), kaolinite (5%), feldspar (<5%) and trace amounts of interstratified illite - smectite, whereas sample 2 is composed of pyrophyllite (NO), mica (20%) and quartz (75%). However, although the mineralogical composition of the two samples is different, the elements remaining undis- solved after the triacid attacks are the same, although in different proportions. Iron, calcium, magnesium, potassium and phosphorus are completely dissolved by the acid treat- ment, whereas silicon, aluminium and titanium are dissolved only in part.The proportion of Si02 and A1203 remaining undissolved in both samples is different, but the ratio between the two oxides in the residues (Table 1) is very similar (ca. 2.33). These results suggest that the residues have a similar composition. The X-ray diffraction results show that the material not dissolved is composed of pyrophyllite accompanied by rutile. In order to determine the influence of the different acids used in the attacks, another sample (sample 3) composed of mica (68%), kaolinite (13%), feldspar (7%) and pyrophyllite (12%) has been treated following Method 1 described under Experimental, using a HN03 - HC104 mixture without HF. The results show that this mixture dissolved only a small proportion of the silicates present (Table 2).The influence of hydrofluoric acid on the decomposition of this sample has been determined by using different propor- tions of this acid (0.5-10 ml) with the same concentrations of HN03 (1 + 4) and HC104 (1 + 4). Fig. 1 shows the concentration of aluminium in p.p.m. in solution versus the volume of hydrofluoric acid used in the attacks. The concentration of aluminium in solution increases as the proportion of hydrofluoric acid increases, but above volumes of 4 ml of HF the aluminium concentration remains in- variable. The results from 0.5-4 ml give a straight line with correlation coefficient r = 1.02 and the equation y = 1 1 . 3 2 + 95.73. These results show that for volumes of 1-4 ml of HF the aluminium in solution comes from the silicate minerals that accompany pyrophyllite, but for volumes greater than 4 ml of HF, the proportion of aluminium in solution does not increase because the pyrophyllite that constitutes the white residue remaining is not decomposed.Attacks on pure pyrophyllite with HN03 - HC104 - HF mixtures show that this mineral is hardly dissolved. Sample 1 was attacked in the pressure vessel with the same amounts of acid (5 ml of HF) and heated at 50, 100, 125 and 140 "C in order to determine the influence of temperature. The silicon and aluminium liberated are shown in Table 3. The dissolution of silicon and aluminium increases with temperature, and the sample is completely dissolved when heated at 125 "C Table 2. Percentages of elements dissolved by HN03 - HC104 attack on sample 3 Element (quoted Total element as oxide) dissolved, Yo A1203 .. . . . . 2.29 Fez03 . . . . , . 0.17 K2O . . . . . . . . 0.29 MgO . . . . . . . . 0.14 CaO . . . . . . . . 0.23 TiOz . . . . . . . . 0 Table 3. Percentages of Si02 and AI2O3 dissolved by HF in a pressure vessel at various temperatures Temperature/"C Si02 dissolved, YO AI2O3 dissolved, YO 50 26.75 20.60 100 41.20 27.59 125 54.85 33.02 140 54.79 33.13 0 0 v c $140 1 C I 1 1 0 u Volume of HF used for attacldrnl I . 1 2 3 4 5 6 7 8 9 v Volume Fig. 1. Concentration of dissolved aluminium in solution versus volume of hydrofluoric acid used in the attack not effective when the mineral pyrophyllite is present. However, total decomposition does occur in a pressure vessel at temperatures above 125 "C. References 1. Abbey, S., Geol. Surv. Can. Pap., 1967, No. 67-37. 2. Abbey, S., Geol. Surv. Can. Pap., 1968, No. 68-20. 3. Belt, C. B., Anal. Chem., 1967, 37, 676. 4. Bennett, H., and Reed, R. A., "Chemical Methods of Silicate Analysis," Academic Press for British Ceramic Research Association, London, 1971. 5. Bennett, H., Early, R. P., Hawley, W. G., and Thwaites, I., Trans. Br. Ceram. SOC. , 1962, 61, 636. 6. Murphy, J., and Riley, J. P., Anal. Chim. Acra, 1962, 27, 31. Conclusions The methods conventionally used to decompose silicate rocks using mixtures of hydrofluoric - perchloric - nitric acid are Paper A6125 Received January 24th, 1986 Accepted March 8th, 1986

ISSN:0003-2654    

DOI:10.1039/AN9861101107

出版商:RSC    

年代:1986

数据来源: RSC

摘要:

1109 ANALYST SEPTEMBER 1986 VOL. 111 BOOK REVIEWS lmmunoassays in Food Analysis Edited by B. A. Morris and M. N. Clifford. Pp. xxii + 222. Elsevier. 1985. Price f25. ISBN 0 85334 321 7. This book is based on the papers presented at the first UK Symposium on Immunoassays in Food Analysis which was held at the University of Surrey in 1983. It is divided into three sections that cover the principles of immunoassay its appli-cation to the analysis of macromolecules and to the analysis of small molecules. The first published application of an immunoassay to food analysis appeared in 1970 and in the first chapter M. N. Clifford traces the development of this topic. As an appendix to this chapter Dr. Clifford has compiled a bibliography of papers (160 papers up to 1983) on food analysis by immunoas-say and this provides a most valuable source for the novice in this area.In Chapter 2 (B. A. Morris) the principles and practical aspects of immunoassay development are skilfully expounded. This chapter is packed with useful information on all aspects of assay development (labelling antibody pro-duction assessment of antisera assay conditions separation systems). The coverage is extended to enzyme immunoassay (EIA) in Chapter 3 which includes brief practical details of assay protocols in tabular form. No book on immunoassay would be complete without a chapter on non-isotopic labels, and in Chapter 4 G. W. Aherne surveys fluorescent chemi-luminescent and bioluminescent labels. Time-resolved fluor-escence immunoassays and chemiluminescent immunoassay have made considerable progress since 1983 and so this chapter is rather out of date in places but nonetheless provides a useful overview.The remainder of the book covers specific applications. Food analysis is complicated by the complexity of the sample and the multi-step sample preparation procedures (e.g. meat mixtures must be minced homogenised centrifuged and filtered in order to produce a sample suitable for analysis). Various applications are described including EIAs for animal albumins. These are used for species identification of meat (EIA ensures that the meat in your beefburger really is beef and not kangeroo!). DetaiIs of assays are also presented for arnyloglucosidase in beer (this enzyme is used to produce low-calorie beers) and staphylococcal enterotoxins in food.The third section of the book is devoted to the analysis of small molecules such as ochratoxin A (a toxic secondary metabolite of fungal species such as Aspergilius) anabolic hormones (e.g. diethylstilboestrol) and glycoalkaloids (e.g. a-solan-me). Overall this book provides a good introduction to the scope and problems of EIA in food analysis. L . J . Kricka Ion Solvation Yizhak Marcus. Pp. vii + 306. WiIey-lnterscience. 1985. Price f42. ISBN 0 471 90756 1. The author well known for two earlier works on solution chemistry “Ion Exchange and Solvent Extraction of Metal Complexes” (with Kertes) in 1969 and “Introduction to Liquid State Chemistry” in 1977 continues this theme with the present volume. Following an introduction ion solvation in the gas phase studied largely by mass spectrometry is briefly dealt with.The author then discusses various interactions that take place during liquid-phase solvation followed by an analysis of structural and kinetic aspects; here the use of X-ray infrared and NMR methods makes interesting reading. Chapter Five is devoted to the particular case of ion hydration. Chapters Six and Seven deal with ion - solvent interactions in non-aqueous and mixed solvents Chapter Eight with ion-pairing reactions (some in molten hydrated salts) and the final chapter discusses applications. The work is interspersed with excellent compilations of relevant data such as appropriate AGO AW and ASo values solvent - ion size parameters and hydration numbers.This well written and assembled book can be warmly recommended to any chemist concerned with an understand-ing of ionic reactions in solution although a good grip on basic thermodynamics would be a prerequisite for a full apprecia-tion of the theory involved. The final chapter on applications where for example pH scales in non-aqueous solvents, solvometallurgy topically interesting nuclear fuel reprocess-ing reactions ion-exchange resin behaviour in mixed solvents and relevance to organic synthesis are discussed acts as a pleasant leavening of the earlier theoretical rigour. M. A. Leonard Spectroscopic Properties of Inorganic and Organo-metallic Compounds. Volume 17 Senior Reporters G. Davidson and E. A. V. Ebsworth. Specialist Periodical Report.Pp. xvi + 395. Royal Society of Chemistry. 1985. Price f95; $138. ISBN 0 85186 153 9; ISSN 0584 8555. This book is a review of the spectroscopic properties of inorganic and organometallic compounds summarising the chemical literature to the end of 1983. It is produced to the high standard that is normally associated with RSC publi-cations with clear figures and chemical structures. The book is sub-divided on a technique basis into seven chapters by different authors viz. NMR by B. E. Mann with 2856 references in 154 pages; NQR by K. B. Dillon with 96 references in 17 pages; Rotational Spectroscopy by S. Cradock with 105 references in 10 pages; Characteristic Vibrations of Main-group Elements by S. Cradock with 344 references in 21 pages; Vibrational Spectra of Transition-element Compounds by G.Davidson with 350 references in 27 pages; Vibrational Spectra of Some Co-ordinated Ligands by G. Davidson with 426 references in 51 pages; Mossbauer Spectroscopy by J. D. Donaldson S. J. Clark and S. M. Grimes with 771 references in 94 pages; and Gas-phase Molecular Structures Determined by Electron Diffraction by D. W. Rankin and H. E. Robertson with 59 references in 14 pages. The different authors have adopted a similar format for each chapter. Within each chapter the work is summarised on a problem rather than technique basis. Key reviews in each area are cited together with a comprehensive overview of the literature. The various authors have succeeded in the gigantic task of condensing information from over 5000 references into a book of this size (395 pages).The major criticism of the book is that the inevitable time lag in producing the book almost 2 years from the period covered to publication reduces its impact on specialists working in the various areas. The Editor promises that the next volume will be produced from camera-ready copy which should reduce this time. In summary this is an excellent book which provides a good overview of the diverse spectroscopic techniques used to study inorganic and organometallic compounds. It will be a useful reference manual for specialists and others interested in this subject. D. P . Leworth 1110 ANALYST SEPTEMBER 1986 VOL. 111 Trace Analysis. Volume 4 Edited by James F. Lawrence. Pp. xii + 305. Academic Press.1985. Price $65; f65. ISBN 0 12 682104 6. This is the second volume of the Trace Analysis series that I have received the previous one being Volume 3. Although I found this volume less stimulating than Volume 3 it was equally well presented and provides a mine of useful infor-mation concerning the topics covered. Chapter 1 concerning ion-selective membrane electrodes and written by Les Ebdon and Beverley King is well written and covers most aspects of the design and application of ion-selective electrodes. It would have been of benefit, however to have had some comparisons between the enzyme and immuno-electrodes presented with other non-potentiometric electrochemical sensors. The second review by Terry F. Bidleman on high-volume collection of organic vapours using solid absorbants is a workmanlike presentation with comprehensive lists of materials used to collect pollutants and adequate descriptions of methods for collection.The third review on “Trace Analysis of Environmental Samples by X-ray Emission Spectroscopy,” is an excellent guide to the technique with a good and easily understandable explanation of X-ray tech-niques and their application to air and water pollution analysis. The fourth review “Inductively Coupled Plasma - Atomic Emission Spectrometry Applied to Elemental Analysis,” was similarly presented but the authors John R. Garbarino and Howard E. Taylor from the US Geological Survey seem not to have noticed that major developments in this field have occurred outside the USA. Thus the references cited are predominantly those published in the USA.Either these authors are not aware of the source of some of the developments they quote for example electrochemical vaporisation into the ICP or they suffer from the “not invented here” syndrome. The final review “Trace Analysis of Wet Atmospheric Deposition by Nuclear Methods” (Landsberger Jervis and Monaro) is also well presented and describes theoretical and practical considerations of neutron activation analysis and proton-induced X-ray emission (PIXE) in addition to the analytical procedures constraints and interpretation of the method. In their conclusions these authors present a real assessment of the techniques and offer areas for improvement rather than claim the techniques to be ultimate.To quote them “certainly the last chapter on the analysis of atmos-pheric precipitation chemistry has not been written yet.” This is also true of most analytical techniques and I look forward to reading subsequent volumes of Trace Analysis series to find out more. R. D. Snook Synthetic Polymeric Membranes. A Structural Perspec-tive. Second Edition Robert E. Kesting. Pp. xiv + 348. Wiley-lnterscience. 1985. Price f55.75. ISBN 0 471 807 17 6. This book is devoted to thin polymer films as solids or liquids, which act as semipermeable barriers for permeants in the gaseous liquid or solid state. It ought therefore to be of interest to scientists of various specialisations including analytical scientists. It is towards the last named group that this review is directed and who will be concerned with polymer filtration dialysis gas separations membrane elec-trodes ion-exchange gel permeation chromatography etc.A scan of the chapter headings reveals that there is not a great deal for the routine analyst who will in any case be using well tried systems. Thus out of the ten chapters devoted to topics such as biological membranes liquid membranes, porous membranes phase inversion membranes dense mem-brane polymer solutions and membrane polymers it is only those devoted to membrane separation processes and miscel-laneous uses of membranes that will be of major interest. Nevertheless the three chapters covering membrane poly-mers separations and miscellaneous uses make up just over half the book. Even so the treatment is frequently cursory; for example five pages can hardly do justice to membranes for electrodes.Having regard to emphasis and price this cannot be recommended for the wider readership although there are points of general interest to the more forward looking research analyst through access to libraries. J . D. R. Thomas Plasma Chromatography Edited by Timothy W. Carr. Pp. xiv + 259. Plenum. 1984. Price $37.50. ISBN 0 306 41432 5. Plasma chromatography an emerging analytical technique is based on the principle of the separation of ion-molecules produced from a sample gas containing organic molecules contacted with ions to convert each organic molecule into a very stable ion-molecule. The ion-molecules are separated by injection into a tube of non-reactive gas through which they are progressed by a strong electric field to arrive at a collector as ion peaks at times related to their structure.The first patent for the technique was applied for in 1968 and issued in 1972. This book is devoted to progress made. The objective has been to deal in the first part of the book with fundamental aspects covering instrument design (G. E. Spangler and M. J. Cohen) ion mobility theory (E. A. Mason) and theory of atmospheric pressure ionisation (M. W. Siegel). This plan has led to a sound introduction to all the essentials of basic instrument design and performance sam-pling handling considerations use of the plasma chromato-graph as a gas chromatographic detector and all the basic theory and rate equations for reagent ion and sample ion production and for ion depletion.The result is a readable and easy to follow account supported by well drawn and clear diagrams and systematically developed equations. Four of the remaining chapters are devoted to applications with well chosen underlying theory for covering the behaviour of isomeric compounds for illustrating the use of ion mobility spectra in analysis (D. F. Hagen) use of plasma chromato-graphy as a gas chromatographic detector (H. H. Hill and M. A. Bain) and applications in the areas of toxic airborne chemical analysis (R. J. Dam) and analysis of semiconductor surfaces and gases inside microelectronic packages (T. W. Carr). The final chapter devoted to instrument design and automation (R. F. Wernlund).is an appropriate ending for stimulating the reader on to more elaborate possibilities such as coupling with mass spectrometry and computer interfacing. The book emphasises that plasma chromatography is an extremely sensitive detection technique. It also discusses the other advantages such as information about the size of molecular species but with cautious reminders of limitations and the need for attention to such matters as the internal standardisation of the instrumental technique. All this points to a good book on the pioneering of plasma chromatography, which is an appropriate introduction to all who wish to learn something of the technique. J . D. R. Thoma ANALYST SEPTEMBER 1986 VOL. 111 1111 Advances in Steroid Analysis ‘84 Edited by S. Gorog. Analytical Symposia Series Volume 23.Pp. xii + 604. Elsevier. 1985. Price $139; Df1375. ISBN 0 444 99533 1. I recently organised a members’ papers meeting of my Association and was concerned that I was not able to check the contents of the talk in the same way that I would if the paper had been submitted for publication in a journal. In the event, the papers were very good and this is also the case with this book which reports the papers presented at the 1984 Szeged (Hungary) Symposium. The book contains 66 papers presen-ted by steroid analysts working in the field with a bias towards the methodology of steroid analysis. The range of steroids considered ranges across all of the important groups including hormones both bound total and free vitamins cardiac drugs and bile salts.The range of methods covered represents the latest technology such as HPLC GC RIA EIA and densitometry . My particular subjects of interest included “blood spot levels of 17-hydroxyprogesterone on CAH” and “steroid levels during sports performance. ” Billed as an International Forum on Steroid Analysis it should be recognised that most of the papers presented are from Eastern Bloc countries although there are some papers from the UK (Steroid analysi’s in saliva from the Welsh National School of Medicine and Sterols by GC - MS from Glasgow Royal Infirmary). The fact that this is the 23rd in the series speaks for the success of this type of book but because of the wide-ranging nature of the topics it is difficult to visualise it as a textbook for everyone but more as a book that should be on the shelf of the routine and research laboratory in order to convey the state of the art in steroid analysis and to avoid duplication in research programmes.J. F. Stevens Cosmetic Analysis. Selective Methods and Techniques Edited by P. Bore Cosmetic Science and Technology Series Volume 4. Pp. xii + 534. Marcel Dekker. 1985. Price $85 (US and Canada); $102 (Rest of World). ISBN 0 8247 7113 3. Before deciding whether to purchase this expensive volume, analysts must assess how much of it will be of direct use to them. The Editor and the authors all come from L’OrCal, France and consequently the approach is that of a large manufacturer’s laboratories. The chapters vary between techniques and classes of materials and of the nine chapters only five would be of some help to a control laboratory in checking compliance to the EEC Cosmetic Products Direc-tive.The opening chapter discusses the spectral analysis of polymers used in hair and nail cosmetics for which detailed separation schemes are given with guidance on the charac-teristics of IR and 1H and 13C NMR spectra. Further details of these spectra are gathered in an enormous 231-page Appen-dix which illustrates 112 spectra and whilst this Appendix unbalances the book the information may well be of use in areas outside cosmetics. A brief account of voltammetry follows for three specific applications. Polarographic methods are all too often dis-missed but I doubt if many will be persuaded to buy the equipment on the strength of a few examples.Another short chapter follows on the determination of mercaptoacetic acid, but surprisingly no reference is made to the similar official EEC method. The fourth chapter is a clear account of the application of pyrolysis GC to characterising and identifying high polymers. The same technique is then discussed in relation to quaternary ammonium compounds. A further technique headspace analysis is reported for three particular determinations of residues viz. solvents and monomers in polymers 1,4-dioxane in surfactants and hydrogen sulphide. One of the major analytical problems for cosmetic products is the identification and determination of preservatives of which about 60 may be used. The seventh chapter is a comprehensive review of nine TLC systems that can be combined with nine spray reagents to aid identification.This is information that will remain of use even after an official EEC method is published but it is disappointing that nothing is offered for the quantitation of preservatives. The penultimate ch5pter is a short discussion of ion-exchange chromatography as applied to the analysis of protein derivatives and amino acids. The last chapter is on the analysis of oxidation hair dyes by HPLC and incorporated within its compass there is a fine overview of the technique. This book will be of clear usefulness to other manufacturing laboratories but of considerably less relevance to enforce-ment laboratories. The volume abounds in tables and figures and the printing and binding are of high quality but the number of minor errors is annoyingly high for such a high-priced book.S. Crisp Ion- and Molecule-selective Electrodes in Biological Systems J. Havas. Pp. 238. Springer-Verlag. 1985. Price DM98. ISBN 3 540 13725 4. This is a tightly packed informative book written by an author who has been closely connected with electrochemical measurements in the biological and general scientific field since about the time of the burst of interest in analytical potentiometry occasioned by the ion-selective electrode devel-opments of the 1960s. The main subject matter is very usefully introduced by the opening chapter on equilibria in biological fluids but except for one page this is devoted to blood fluids. The neglect of the other fluids is surprising in view of the importance of electrochemical measurements in sweat saliva urine etc.and having regard to the fact that many such measurements are discussed in the later chapters. Nevertheless the discussion on blood fluids is well done with particular and proper emphasis to acid - base equilibria. The next three chapters are concerned respectively with methodology and instrumentation (Chapter 2) ion-selective electrode applications which include pH sodium potassium, calcium chloride and fluoride electrodes and which essen-tially account for just over a third of the subject matter of the book (Chapter 3) and molecule-selective electrode appli-cations devoted to oxygen hydrogen carbon dioxide ammo-nia and enzyme systems (Chapter 4).There is a final chapter of five pages on ion-selective field effect transistors which in view of recent rapid developments is far from up-to-date. Indeed it is in this last respect that the whole book can be faulted for there are but few references to work published since 1979 although there are one or two references for 1983. The book is imaginative in mode of presentation with clearly presented and well illustrated text preceding the very useful summary tables of applications of the various types of electrodes and sensors which occasionally go beyond poten-tiometric sensors to coulometric and amperometric systems. If the tables were up to date the book would be a sell-out as the brief summary relating to each application area is a model o 1112 ANALYST SEPTEMBER 1986 VOL.111 conciseness in summarising essential information. For exam-ple for a potassium determination it is deduced at a glance that a flow-through electrode was used on whole blood in open-heart surgery and that the potassium values agreed with flame photometry. The reference to each application is keyed to the reference list at the end of the book for the reader who needs source publication. There are a few unfortunate statements such as the total concentration of ions (anions and cations) in blood fluid being ca. 150 mmol dm-3 and some misprints. On the credit side is a discussion of safety considerations underlying the use of elec-trical instrumentation during in vivo monitoring a good index and an extensive reference list even if not recent.On the whole this is a sufficiently different book from others in the field for it to be recommended for purchase. J . D. R. Thomas Biological Reference Materials Availability Uses and Need for Validation of Nutrient Measurement Edited by Wayne R. Wolf. Pp. xviii + 425. Wiley-interscience. 1984. Price f69.40. ISBN 0 471 80636 6. This hardback printed from typescripts is sub-titled “Avail-ability Uses and Need for Validation of Nutrient Measure-ment .” However its coverage includes environmental and clinical materials. It consists of the proceedings forming about 80% of the volume of a meeting on biological reference materials held in 1983 and an Appendix that reproduces in toto a 1982 publication from the US National Bureau of Standards (NBS) of the proceedings of a workshop held in 1980 on reference materials for organic nutrient measure-ment.The main proceedings consist of 17 contributions arranged in groups by 26 participants of whom 21 hail from North America. The first section of six papers covers programmes for certified reference materials available or in preparation, of bodies such as the NBS the EEC Bureau of Reference and the International Atomic Energy Agency. Some analytical information is provided on existing materials and needs for other materials are assessed. Most of the analytes are trace elements but organic constituents of clinical reference materials and edible oils are also mentioned. The matrices range from marine sediments through aquatic and land plants to sewage sludge and animal tissues.Emphasis is placed on requirements for reference materials, such as homogeneity and stability in the second section of four papers which covers the problems of obtaining and characterising materials and of spiking materials to obtain adequate levels of analytes of interest. Three of the four papers in Part 3 are concerned with the provision and use of quality control materials for nutrient (food) analysis and the fourth is an interesting examination of the use of analyte pairs in a reference material as a means of checking analyte dilution. The final two papers address problems of environ-mental specimen banking the first considers requirements for valid sampling and the second reviews trace metal analysis, largely by atomic absorption in a variety of materials within the programme for the German Environmental Specimen Bank. At the end of the formal presentations an open discussion forum was held in which two key themes of the role of specimen banking and the needs production uses and coordination of biological reference materials were explored. Apart from the introductory remarks and a summary the discussion reported for each topic unfortunately extends to less than one page and is of limited value. The 1980 workshop reported in the Appendix was concerned with the then current state of measurement techniques with matrices suitable for reference materials and considered especially fats including cholesterol vitamins and sugars. It made several recommendations and suggested further needs in the NBS programme. This book will be useful to someone new to this specialised and important area and may be of value to groups already active in the fields covered. It is a useful source of information otherwise difficult to gather including helpful background material and has a comprehensive although terse index. However its price and the inclusion of the NBS report, published previously and occupying nearly one quarter of the contents will restrict its appeal. D. H. Cala

ISSN:0003-2654    

DOI:10.1039/AN9861101109

出版商:RSC    

年代:1986

数据来源: RSC