Spectrophotometric and atomic absorption determination of ramipril, enalapril maleate and fosinopril through ternary complex formation with molybdenum (V)-thiocyanate (Mo(V)-SCN)

Three different sensitive and accurate spectroscopic procedures were developed for the determination of three angiotensin-converting enzyme inhibitors, namely, ramipril, enalapril maleate and fosinopril. The first two spectrophotometric (extractive and non-extractive) procedures were based on ternary complex formation with molybdenum(V) thiocyanate. The formed complex can be determined by extraction with chloroform measured at lambdamax 517 nm Beer's law was obeyed in the concentration range from (10--90 microg ml(-1)) for ramipril and fosinopril and (4--36 microg ml(-1)) for enalapril maleate with molar absorptivity 1.2x10(4), 2x10(4) and 3.4x10(4) l mol(-1) cm(-1), respectively, or by direct measurement after addition of benzalkonium chloride as surfactant and measuring the formed ternary complex at lambdamax 545 nm with a linear relationship in the concentration range from (8-7-2 microg ml(-1)), (3--27 microg ml(-1)) and (8--72 microg ml(-1)) for ramipril, enalapril maleate and fosinopril with molar absorptivity 1.5x10(4), 5x10(4) and 2.1x10(4) l mol(-1) cm(-1), respectively. The third procedure is atomic absorption measurement through the quantitative determination of molybdenum content of the complex. These methods hold their accuracy and precision well when applied to the determination of ramipril, enalapril maleate and fosinopril in their dosage forms.     

Spectrophotometric determination of some drugs for osteoporosis

Three simple, accurate and sensitive spectrophotometric methods are developed for the determination of some new drugs for the treatment of osteoporosis: risedronate sodium (I), alendronate sodium (II) and etidronate disodium (III). The first method is based on the measurement of difference in absorbance (Delta A) of risedronate sodium in 0.01 mol l(-1) hydrochloric and 0.1 mol l(-1) sodium hydroxide at 262 nm. Beer's law is obeyed over a concentration range of 15-150 microg ml(-1) with mean recovery 99.75+/-1.22 and molar absorptivity (epsilon) 1.891 x 10(3). The second method is based on the reaction of the primary amino group of (II) with ninhydrin reagent in methanolic medium in the presence of 0.05 mol l(-1) sodium bicarbonate. The colored product is measured at 568 nm, and the linearity range is found to be 3.75-45 microg ml(-1) with mean recovery 99.77+/-0.73 and epsilon 9.425 x 10(3). The third method is based on oxidation of the three mentioned drugs with ceric (IV) sulphate in 0.5 mol l(-1) sulphuric acid at room temperature and subsequent measurement of the excess unreacted cerium (IV) sulphate at 320 nm. The method obeyed Beer's law over a concentration range of 2-24 microg ml(-1) for the three drugs with mean recovery 99.79+/-1.16, 99.73+/-1.38 and 99.86+/-1.13 and epsilon 14.427 x 10(3), 13.813 x 10(3) and 14.000 x 10(3) for drugs I, II, III respectively. The proposed methods were successfully applied for the determination of the studied drugs in bulk powder and in pharmaceutical formulations. The results were found to agree statistically with those obtained the reported methods. Furthermore, the methods were validated according to USP regulations and also assessed by applying the standard addition technique.     

Fluorimetric trace determination of cerium(III) with sodium triphosphate

Sodium triphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III). The purpose of this study was to investigate the spectrofluorimetric determination of trace amounts of Ce(III) in sodium triphosphate solution. The excitation and emission wavelengths are 303.5 nm and 353 nm respectively. Optimum sodium triphosphate concentration is found to be 0.074 g l(-1) at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range 0.001-45 mug ml(-1). The detection limit is 9.4 x 10(-4)mug ml(-1). The relative standard deviations for 30 mug ml(-1) and 0.05 mug ml(-1) Ce(III) in 0.074 g l(-1) sodium triphosphate solution are 1.1% and 0.72% respectively. Quenching effects of other lanthanides and some inorganic anions are described. This method is a direct and rapid analytical method for the determination of Ce(III) in rare earth mixtures and cerium concentrates.     

Spectrophotometric studies and applications for the determination of yttrium in pure and in nickel base alloys

Yttrium reacts with 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2'-bromophenylazo)-6-hydroxypyrimidine-2,4-dione (II), 5-(2',4'-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (III), 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (IV), 5-(2'-methyl-4'-hydroxyphenylazo)-6-hydroxypyrimidine-2,4-dione (V) to form a dark pink complexes, having an absorption maximum at 610, 577, 596, 567 and 585 nm, respectively. The complex formation was completed spontaneously in theil buffer solution and the resulting complex was stable for at least 3 h after dilution. Under the optimum conditions employed, the molar absorptivities were found to be 1.60 x 10(4), 1.29 x 10(4), 1.96 x 10(4), 1.45 x 10(4) and 1.21 x 10(4) l mol(-1) cm(-1) and the molar ratios were (1:1) and (1:2) (M:L). The linear ranges were found within 95 microg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. Interfering species and their elimination have been studied. The precision and recovery are both satisfactory.     

The surfactant-sensitized analytical reaction of niobium with 8-hydroxyquinoline-5-sulphonic acid

Cationic surfactants, such as cetylpyridinium bromide (CPB), sensitize the colour reaction of Nb(V) with 8-hydroxyquinoline-5-sulphonic acid (H(2)L). The formation of a ternary complex of stoichiometry 1:3:3 (Nb-L-CPB) is responsible for the observed enhancement in absorptivity and the quenching in the fluorescence of the Nb-L chelate, when a surfactant is present. The ternary complex exhibits maximum absorption at 383 nm ( = 1.46 +/- 0.01 x 10(4) l.mole(-1).cm(-1)) at pH 5.7, and Beer's law is obeyed up to 6-mug ml Nb concentration. Conditional formation constants of the niobium chelate in the presence and absence of CPB have been determined. On the basis of a detailed spectrophotometric and fluorimetric study the nature of the chromophoric reagent-surfactant interaction and the peculiar features of the sensitization by CPB are discussed.     

Spectrofluorometric trace determination of cerium(III) in sodium hexametaphosphate solutions

The use of sodium hexametaphosphate in the spectrofluorometric determination of trace amounts of cerium(III) ions is described. Sodium hexametaphosphate acts as a specific reagent for enhancing the fluorescence intensity of cerium(III) in aqueous solutions. The apparent excitation and fluorescence wavelength used are 304 and 344 nm, respectively. Maximum fluorescence intensity is obtained by irradiating Ce(III) dissolved in 5.346 g/l sodium hexametaphosphate solution at room temperature. The fluorescence varies linearly with the concentration of cerium(III) in the range of 0.001-60 microg/ml. The coefficient of variation for 45 microg/ml Ce(III) in 5.346 g/l sodium hexametaphosphate solution is 1. The quenching effects of other lanthanides and some inorganic anions are given. This technique permits a direct and rapid determination of cerium(III) in rare earth mixtures and cerium concentrates.     

Application of the Weisz Ring oven technique to the separation and identification of micro-quantities of some less familiar cations

Summary Use of the ring oven in separation and identification of mixtures of less familiar metal ions has been described. Separation of metal ions from the following mixtures has successfully been carried out: 1. UO₂(II) and Th(IV), 2. Th(IV) and Ce(IV), 3. Pd(II) and Au(III), 4. Pt(IV) and Au(III), 5. Ce(III) and Ce(IV), 6. UO₂(II), Th(IV) and Ti(IV), 7. Th(IV), Ti(IV) and Ce(IV), 8. Th(IV), Ce(IV) and Zr(IV), 9. Ti(IV), V(V) and Zr(IV), 10. Mo(VI), V(V) and W(VI) and 11. Be(II), Al(III) and Mg(II). In the case of binary mixtures, the separation was in the form of a central spot and a concentric ring; in ternary mixtures the metals were precipitated in a central spot and two concentric rings.

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Zusammenfassung Zur Trennung und Identifizierung folgender Gemische seltenerer Metallionen wurde der Ringofen mit Erfolg verwendet: 1. UO₂(II) und Th(IV), 2. Th(IV) und Ce(IV), 3. Pd(II) und Au(III), 4. Pt(IV) und Au(III), 5. Ce(III) und Ce(IV), 6. UO₂(II), Th(IV) und Ti(IV), 7. Th(IV), Ti(IV) und Ce(IV). 8. Th(IV), Ce(IV) und Zr(IV), 9. Ti(IV), V(V) und Zr(IV), 10. Mo(VI), V(V) und W(VI) und 11. Be(II), Al(III) und Mg(II). Bei binären Gemischen erfolgt die Trennung in einen zentralen Fleck und einen Ring, bei ternären Mischungen in einen Fleck und zwei konzentrische Ringe.

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Résumé On a décrit l'utilisation du four annulaire pour la séparation et l'identification de mélanges d'ions métalliques moins courants. On a effectué la séparation des ions métalliques à partir des mélanges suivants: 1. UO₂(II) et Th(IV), 2. Th(IV) et Ce(IV), 3. Pd(II) et Au(III), 4. Pt(IV) et Au(III), 5. Ce(III) et Ce(IV), 6. UO₂(II), Th(IV) et Ti(IV), 7. Th(IV), Ti(IV) et Ce(IV), 8. Th(IV), Ce(IV) et Zr(IV), 9. Ti(IV), V(V) et Zr(IV), 10. Mo(VI), V(V) et W(VI) et 11. Be(II), Al(III) et Mg(II). Dans le cas des mélanges binaires, la séparation se présentait sous forme d'une tache centrale et d'un anneau concentrique; chez les mélanges ternaires, les métaux étaient précipités en une tache centrale et deux anneaux concentriques.

     

Spectrophotometric and derivative spectrophotometric determination of aluminium with Hydroxynaphthol Blue

The reaction of aluminium(III) with Hydroxynaphtol Blue (HNB) in aqueous media at apparent pH 5.5 results in a red complex that is stable for at least 4 hr. Beer's Law is obeyed up to 1.6 microg/ml of aluminium(III) with an apparent molar absorptivity of 1.66 x 10(4) l.mol(-1). cm(-1) at 569 nm. This paper proposes procedures for aluminium(III) determination by ordinary and first-derivative spectrophotometry. The results demonstrated that the linear dynamic range is 0.03-1.60 microg/ml for ordinary spectrophotometry and 11.8-320.0 ng/ml for first derivative spectrophotometry. The HNB is not selectivity for aluminium, but the addition of EDTA allows the aluminium determination in the presence of accepted amounts of Ca(II), Mg(II), Mn(II), Ba(II), Sr(II), Cd(II), Pb(II), La(III), In(III), Bi(III) and Zn(II). The interference of Cu(II) and Hg(II) can be masked by thiosulphate. Ions such as UO(2)(II), Mo(VI), Co(II), Ti(IV) and PO(4)(III) do interfere seriously. This method was applied for aluminium determination in copper-base alloy, zinc-base alloy, magnesium-base alloy, iron ore, manganese ore, cement, dolomite, feldspar and limestone. The results indicated high accuracy and precision.     

Kinetics of manganese(III) acetate in acetic acid: generation of Mn(III) with Co(III), Ce(IV), and dibromide radicals; reactions of Mn(III) with Mn(II), Co(II), hydrogen bromide,and alkali bromides

The reaction of cobalt(III) acetate with excess manganese(II) acetate in acetic acid occurs in two stages, since the two forms Co(IIIc) and Co(IIIs) are not rapidly equilibrated and thus react independently. The rate constants at 24.5 degrees C are kc = 37.1 +/- 0.6 L mol-1 s-1 and ks = 6.8 +/- 0.2 L mol-1 s-1 at 24.5 degrees C in glacial acetic acid. The Mn(III) produced forms a dinuclear complex with the excess of Mn(II). This was studied independently and is characterized by the rate constant (3.43 +/- 0.01) x 10(2) L mol-1 s-1 at 24.5 degrees C. A similar interaction between Mn(III) and Co(II) is substantially slower, with k = (3.73 +/- 0.05) x 10(-1) L mol-1 s-1 at 24.5 degrees C. Mn(II) is also oxidized by Ce(IV), according to the rate law -d[Ce(IV)]/dt = k[Mn(II)]2[Ce(IV)], where k = (6.0 +/- 0.2) x 10(4) L2 mol-2 s-1. The reaction between Mn(II) and HBr2., believed to be involved in the mechanism by which Mn(III) oxidizes HBr, was studied by laser photolysis; the rate constant is (1.48 +/- 0.04) x 10(8) L mol-1 s-1 at approximately 23 degrees C in HOAc. Oxidation of Co(II) by HBr2. has the rate constant (3.0 +/- 0.1) x 10(7) L mol-1 s-1. The oxidation of HBr by Mn(III) is second order with respect to [HBr]; k = (4.10 +/- 0.08) x 10(5) L2 mol-2 s-1 at 4.5 degrees C in 10% aqueous HOAc. Similar reactions with alkali metal bromides were studied; their rate constants are 17-23 times smaller. This noncomplementary reaction is believed to follow that rate law so that HBr2. and not Br. (higher in Gibbs energy by 0.3 V) can serve as the intermediate. The analysis of the reaction steps then requires that the oxidation of HBr2. to Br2 by Mn(III) be diffusion controlled, which is consistent with the driving force and seemingly minor reorganization.     

Observation of cerium isotope fractionation in ion-exchange chromatography of Ce(III)-malate complex

The cerium isotope fractionation between Ce(III)-malate complex in aqueous solution and cerium ions in a cation-exchange resin was conducted by displacement chromatography. The pH and the chemical composition of the eluent were optimized for maintaining the self-sharpening band boundaries and the 21 m chromatographic migration of the Ce band underwent. Graphite slurry was coated on the tantalum filament prior to sample loading for reducing the isobaric interferences in cerium isotopic ratio determination by mass spectrometry. From the experimental results, it was found that the heavier isotope was enriched in the front boundary part of the cerium adsorption band, which meant that the heavier isotope was preferentially fractionated into the Ce3+ malate complex rather than simply hydrated Ce3+ ions. The isotope separation coefficient for the 136Ce/140Ce and 142Ce/140Ce was 5.2 x 10(-5) and -1.9 x 10(-5), respectively, at 298 K.     

N-oxides of 4-(5-nonyl)pyridine and trioctylamine as extractants for cerium(IV) and its separation from thorium(IV)

Trace level cerium has been oxidized to the quadrivalent state with potassium dichromate and shown to be preferentially extracted from very dilute mineral acid solutions and also from moderate nitric acid media by 0.1M solutions of 4-(5-nonyl)pyridine oxide and trioctylamine oxide dissolved in xylene. The dependence of extraction on the type of N-oxide, acid concentration and the N-oxide concentration has been investigated. The influence of the concentration of salting-out agents is described. Separation factors for a number of metal ions relative to cerium(IV) are reported for 0.1 M 4-(5-nonyl)pyridine oxide/xylene-0.1M sulphuric acid system. The ratio of the D for Ce(IV) to that of Ce(III) is greater than 10⁵, and the D for Ce(IV) is much greater than that for thorium(IV). Separation of cerium(IV) from thorium has been achieved from 0.1M sulphuric acid solutions using 0.1M 4-(5-nonyl)pyridine oxide/xylene as an extractant.     

Spectrophotometric determination of cobalt with 1-(2-pyridylazo)-2-naphthol and surfactants

A simple and highly selective spectrophotometric method for the determination of cobalt based upon the rapid reaction with PAN in the presence of surfactants and minute amounts of ammonium persulphate at pH 5.0 is described. The cobalt(III) chelate is made water-soluble by a neutral surfactant. Triton X-100, combined with sodium dodecylbenzene sulphonate (DBS). Iron(III), bismuth, tin(IV) and aluminium are masked with oxalate or citrate. Iron(II) must be absent. The other metal-PAN chelates, except that of nickel, are readily decomposed by EDTA. Up to 150 microg of nickel does not interfere. When larger amounts up to 625 microg are present, the absorbance can be corrected by measurements at two wavelengths. In a strongly acid medium (below pH 0.5) the nickel and other metal chelates are completely and instantaneously decomposed, while the cobalt(III) chelate remains unchanged. When, in place of EDTA, several ml of 6M hydrochloric acid are added after the colour development, nickel in quantities up to 1250 microg can be tolerated. A several hundredfold excess of zinc and manganese does not interfere. At 620 nm Beer's law is obeyed over the cobalt concentration range 0.4-3.2 microg/ml. The precision (95% confidence) is +/- 1.0 microg for 100 microg of cobalt. The molar absorptivity is 1.90 x 10(4) l. mole(-1) .cm(-1).     

Fluorimetric determination of cerium with paracetamol

A simple, sensitive and selective method for determination of cerium(IV), based on the oxidative reaction between cerium(IV) and paracetamol, has been developed. The fluorescent species is an oxidation product of paracetamol and has excitation and emission maxima at 265 and 360 nm, respectively. The fluorescent intensity of the system is linear over the range 2.0 x 10(-7)-8.0 x 10(-6)M Ce(IV). The method has been applied in the determination of Ce(IV) in synthetic mixtures and ores with good accuracy being achieved.     

Spectrophotometric determination of cerium(IV) using a phenothiazine derivative.

A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of cerium(IV) using a phenothiazine derivative, propionyl promazine phosphate (PPP). This method is based on the formation of a red-colored radical cation upon a reaction of PPP with cerium(IV) in a phosphoric acid medium having maximum absorbance at 513 nm. Beer's law is valid over the concentration range of 1-11 microg/ml with a Sandell's sensitivity value of 16.14 ng/cm2. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys. Other phenothiazine derivatives viz. butaperazine dimaleate and propericiazine were also used for the determination of cerium(IV).     

Selective determination of cobalt using polyurethane foam and 2-(2-benzothiazolylazo)-2-p-cresol as a spectrophotometric reagent

The present work describes a selective, rapid and economical method for the determination of cobalt using the 2-(2-benzothiazolylazo)-p-cresol (BTAC) as a spectrophotometric reagent associated with a solid extraction on polyurethane foam. The BTAC reacts with Co(II) in the presence of Triton-X100 surfactant forming a green complex with maximum absorption at 615 nm. The reaction is used for cobalt determination within a pH range of 6.50-7.50, with an apparent molar absorptivity of 1.62 x 10(4) L mol(-1) cm(-1). Beer's Law is obeyed for a concentration of at least 1.60 microg ml(-1). A selective procedure is proposed for cobalt determination in the presence of Fe(II), Hg(II), Zn(II) and Cu(II) up to milligram levels using masking agents. Polyurethane foam is used for the preconcentration and separation of cobalt from thiocyanate media and this procedure is applied to its determination in nickel salts and steel alloys.     

Non-extractive derivative spectrophotometric determination of cobalt in neutral micellar medium

A sensitive derivative spectrophotometric method using 1-nitroso-2-naphthol has been developed for determination of trace amounts of cobalt in the presence of a neutral surfactant. Photometric parameters, viz., lambda(max), molar absorption coefficient and analytical sensitivity of the complex formed in micellar media are 420 nm, 3.18x10(4) l mol(-1) cm(-1) and 2.05 ng ml(-1), respectively. Beer's law holds from 0.20 to 3.0 mug ml(-1) of the analyte concentration. The method has a high sensitivity with a detection limit of 1.68 ng ml(-1). A selective determination of cobalt in presence of copper(II) or iron(III) using derivative spectral profiles and without any masking or pre-separation is also reported. Samples of drugs and standard alloys analysed by the proposed method yielded results comparable to those obtained using recommended procedures.     

Spectrophotometric determination of four macrolide antibiotics in pharmaceutical formulations and biological fluids via binary complex formation with eosin [corrected

A simple, rapid, and sensitive validated spectrophotometric method was developed for the determination of certain macrolide antibiotics namely, erythromycin (I), azithromycin dihydrate (II), clarithromycin (III), and roxithromycin (IV) in bulk powders, pharmaceutical formulations, and spiked biological fluids. The proposed method is based on the formation of a binary complex between each of the studied drugs and eosin Y in aqueous buffered medium. Under the optimum conditions, the binary complexes showed absorption maxima at 542-544 nm. The absorbance of the binary complexes obeyed Beer's law over the concentration range of 1-10 micro/g/mL for II, 2-20 microg/mL for I and IV, and 3-30 microg/mL for III. The mean percentage recoveries were 100.04 +/- 0.83, 99.98 +/- 0.80, 100.17 +/- 0.91, and 99.55 +/- 0.91, with minimum detectable molarities of 2 x 10(-7) for I and II, 4 x 10(-7) for III, and 3 x 10(-7) for IV. The different experimental parameters affecting the development and stability of the colors were studied and optimized. The proposed method was successfully applied to the analysis of the cited drugs in some pharmaceutical formulations. The results obtained were in good agreement with those obtained using the reference methods. The proposed method was further applied to spiked human urine and plasma. A proposal of the reaction pathway is suggested.     

Investigation of hydrothermal routes to mixed-metal cerium titanium oxides and metal oxidation state assignment using XANES

The reaction between TiF(3) or TiO(2) and Ce(3+) in sodium hydroxide solutions yields highly crystalline NaCeTi(2)O(6) at room temperature and under mild hydrothermal conditions (T < or = 240 degrees C). There is no evidence for the formation of ternary Ce-Ti-O materials by this method, and the use of bases other than NaOH always produces poorly crystalline materials. The material NaCeTi(2)O(6) has a distorted perovskite structure with sodium and cerium ions randomly occupying the A sites: Pnma, a = 5.4517(8) A, b = 7.7292(6) A, c =5.4573(3) A. XANES spectroscopy at the Ti K edge and Ce L(III) edge, with reference to crystalline model compounds, reveals that cerium is found solely as Ce(III) and titanium as Ti(IV) in NaCeTi(2)O(6). Isomorphous substitution of Ce(3+) by Nd(3+) or Ti(4+) by V(4+) is found to be very facile under hydrothermal conditions (at a temperature of 240 degrees C), by addition of appropriate amounts of metal salts to the hydrothermal reaction mixtures. The series NaCe(1-x)Nd(x)Ti2O6 (0 < or = x < or = 1) and NaCeTi(2-x)V(x)O6 (0 相似文献   

Colour reaction of gold with 5-(4-sodium sulphonatephenylazo)-8-aminoquinoline and its analytical application

The synthesis of 5-(4-sodium sulphonatephenylazo)-8-aminoquinoline (SPAQ) is described, and a simple, rapid, selective and sensitive new spectrophotometric method for determination of gold is developed. SPAQ reacts with gold(III), and in the presence of cetyl trimethyl ammonium bromide cationic surfactant and upon making the solution alkaline, forms a blue-green 1:3 (metal:ligand) with an absorption maximum at 605 nm. Beer's law is obeyed over the concentration range 0-2 microg/ml gold. The molar absorptivity and Sandell's sensitivity of the method are 1.48 x 10(5) 1.mole(-1).cm(-1) and 0.0013 microg/cm(2), respectively. The interference of various ions has been studied and the method has been used for the determination of microamounts of gold in ores and anode slimes.     

Analytical applications of ternary complexes-VIII An improved reagent system for the spectrophotometric determination of aluminium

Aluminium ions form a ternary complex with Catechol Violet (CV) and cetyltrimethylammonium bromide (CTAB) in which an Al(3)+:CV:CTAB ratio of 1:2:5 is observed. The sensitivity of the binary complex between aluminium and Catechol Violet (615nm) = 1.50 x 10(3) l. mole (-1). mm(-1) is enhanced on ternary complex formation to (670nm) = 5.30 x 10(3) l. mole(-1). mm(-1). The colour is formed instantaneously, stabilizes within 20 min, and may be used for the detection of aluminium in the range O.27-54 pm in the presence of EDTA which prevents the interference of most ions. A benzoate extraction procedure for aluminium is used to prevent interference from hundredfold amounts of Cr(VI), Fe(II), Fe(III), Hg(II), Sb(III), Ti(IV) and acetate, but Be, Cr(III), rare earths, V(V), Zr and tartrate must be absent, as must high concentrations of phosphate and fluoride ions.