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Analytical and Bioanalytical Chemistry (v.360, #1)
Applications of adsorptive stripping voltammetry for the trace analysis of metals, pharmaceuticals and biomolecules by A. Z. Abu Zuhri; Wolfgang Voelter (pp. 1-9).
A review with 159 references is presented on the applications of adsorptive stripping voltammetry (AdSV) for determining trace metal ions in different environmental samples (e.g. water, soil, plant, biological fluids). The analytical applications of AdSV to biologically active organic compounds (e.g. pharmaceuticals, pesticides, biomolecules) are also discussed.
Feasibility studies of neutron activation analysis with kilogram-size samples by P. Bode; O. Lakmaker; P. van Aller; M. Blaauw (pp. 10-17).
Instrumental neutron activation analysis (INAA) can now directly be applied to samples with masses in the kilogram range. It enables the analysis of material which is considered to be not representative at the scale of the traditional analytical portion, but representative at much larger scale. Large sample INAA (LS-INAA) circumpasses various problems associated with sample-size reduction and homogenization. Examples of feasibility studies are given as on construction waste, contaminated soil, harbour sediment and recyclable material. Also the economics of this method of analysis is discussed.
Platinum speciation with hyphenated techniques: high performance liquid chromatography and capillary electrophoresis on-line coupled to an inductively coupled plasma-mass spectrometer – application to aqueous extracts from a platinum treated soil by S. Lustig; B. Michalke; W. Beck; P. Schramel (pp. 18-25).
1. An on-line hyphenation of reversed phase high-performance liquid chromatography (RP-HPLC) with inductively coupled plasma-mass spectrometry (ICP-MS) is applied, using an ultrasonic nebuliser combined with a membrane desolvator as the interface. Thus, organic solvents (e.g. methanol, hexane) or gradients (e.g. methanol/water) as well as aqueous NaHCO3/NaCl mixtures can be directly used without influence on the plasma. The high resolution power of HPLC enables the separation of Pt-species, whereas ICP-MS is taken for element specific detection with low detection limits. 2. Additionally, a powerful on-line coupling of capillary electrophoresis (CE) and ICP-MS [1, 2] was used for platinum speciation in parallel. With these two methods, independent from each other, first characterisation is achieved about the nature of Pt species formed by interaction with a soil. Aqueous extracts of a clay-like humic soil, treated with a Pt contaminated tunnel dust and Pt model compounds [3] were examined to elucidate transformation processes of Pt-species in a soil.
Optimization of the reduction of Se(VI) to Se(IV) in a microwave oven by C. Brunori; M. B. de la Calle-Guntiñas; R. Morabito (pp. 26-30).
Parameters for the reduction of Se(VI) to Se(IV) in HCl medium by heating in a microwave oven have been optimized. The reduction resulted to be quantitative applying 100% power, corresponding to 600 W heating for 2 min in 6 mol/L or for 3 min in 4 mol/L HCl. The behavior of selenomethionine and selenocystine under the optimized reduction conditions was studied in order to evaluate a possible interference of these selenium species in the determination of Se(VI). The final determination of Se(IV), and Se(VI) were done by hydride generation-atomic absorption spectrometry. The analytical merits of the method are reported. The method was applied to the selective determination of Se(IV), and Se(VI) in spiked river and lake water.
Speciation of vanadium (IV) and vanadium (V) with Eriochrome Cyanine R in natural waters by solid phase spectrophotometry by J. M. Bosque-Sendra; Ma_ Carmen Valencia; Said Boudra (pp. 31-37).
The separation and preconcentration of vanadium (IV) and vanadium (V) using Sephadex DEAE A-25 with Eriochrome Cyanine R has been studied, based on the preconcentration of vanadium (IV) in the first step and V(V) after reduction with ascorbic acid in the second step. Factors affecting the optimum fixation of the complex were investigated. The absorbance of the solid phase is measured directly at 563 nm for V(IV), at 585 nm for V(V) and at 750 nm for both. The proposed method provides a simple and specific procedure for the separation of vanadium in natural waters. The calibration graph is linear up to 150 ng/mL, with RSD of 4.7% for V(IV) and 4.0% for V(V). The detection limits are 1.6 and 1.4 ng/mL for V(IV) and V(V), respectively.
Estimation of tungsten in complex matrices using toluene 3,4-dithiol and thiocyanate by P. Chattopadhyay; M. Mistry (pp. 38-42).
A rapid less labour-intensive procedure for complete decomposition of tungsten bearing complex matrices by potassium pyrosulphate and its determination using toluene 3,4-dithiol and thiocyanate is reported. The analytical results of various standard reference materials are presented (Jasperoid GXR-1, Deposit GXR-3, copper mill head GXR-4, tin-tungsten ore IGS-26, Mo-W ore IGS-27, tungsten concentrate SRM-277, scheelite ore SRM-2430, reference tungsten ore TLG-1, CT-1, BH-1 and Mo-W ore MP-2) along with two manganese nodules (GSPN-2 and GSPN-3) recently introduced by the Chinese Academy of Geological Sciences and one Polish soil sample (SRM-2710). For most of the samples the agreement between the observed value and the published data have been found to be extremely good. Derivations have been noted in some samples where published concentrations are indicative values only, indicating that more data are still required to upgrade the status from proposed/unspecified to the certified level. Results of various statistical analyses (intermethod comparison, F-test and regression analysis) reveal that the methods are matrix dependent. Separation of tungsten from molybdenum is straightforward, hence can be used for a quality control programme and in the evaluation of reference materials.
Fluorination assisted slurry electrothermal vaporization in ICP-AES for the direct analysis of silicon dioxide powder by Peng Tianyou; J. Zucheng (pp. 43-46).
A slurry fluorination electrothermal vaporization (ETV)-ICP-AES method for the determination of Cu and Cr in SiO2 powders has been developed. A polytetrafluoroethylene (PTFE) emulsion is used as fluorinating reagent; the matrix (Si) is partially separated from the sample by selecting the ashing temperature and time to reduce the interference. Moreover, the vaporization behaviour has been investigated in detail. The detection limits are 1.1 ng/mL with 3.8% of RSD (Cu) and 1.6 ng/mL with 3.2% of RSD (Cr). The method is applied to analyze the SiO2 powders with satisfactory results.
A highly selective iodide electrode based on the bis(benzoin)-semiethylenediamine complex of mercury(II) as a carrier by You-Qun Song; R. Yuan; M. Ying; Zhi-Qiang Li; Y.-Q. Chai; H. Cui; G.-L. Shen; Ru-Qin Yu (pp. 47-51).
A new PVC membrane electrode based on the bis(benzoin)-semiethylenediamine (BBSEA) complex of Hg(II) is described which exhibits excellent selectivity towards iodide, related to the unique interaction between the central Hg(II) and the iodide ion. The electrode has a linear response to iodide from 5 × 10–7 to 5 × 10–4 mol/L with a slope of 58 mV/dec.(20°C). The response characteristics were investigated in detail and the mechanism of the electrode was studied with AC impedance and quartz crystal microbalance (QCM) techniques. It can be used for iodide determinations in drug preparations.
Water solubility and octanol/water-partitioning of hydrophobic chlorinated organic substances determined by using SPME/GC by A. Paschke; Peter Popp; Gerrit Schüürmann (pp. 52-57).
The critical step in the determination of water solubilitiy (S w) and octanol-water partition coefficient (K ow) of hydrophobic organic chemicals by using the generator-column technique and the slow-stirring procedure, respectively, is the exact quantification of the low water-phase concentrations of the substances under investigation. We have tested the applicability of solid-phase microextraction (SPME) and gas chromatography with seven chlorinated organic compounds. The substances cover a S w range from 500 mg/L to 7 ng/L and a log K ow range from 3 to 8. The results show that SPME can be a valuable alternative to common preconcentration techniques in the quantification of hydrophobic organics in pure and octanol-saturated water. The apparent SPME distribution constants K SPME (obtained with the 100 μm-PDMS fiber for analyte’s partitioning between fiber coating and aqueous sample) do not correlate directly with octanol/water partition coefficients and thus cannot be recommended as a surrogate parameter for K ow.
Isothermal pressure dependence of the solubility of some triazines in supercritical CO2 by Silvana V. Rodrigues; Decio Nepomuceno; Luci Viana Martins; W. Baumann (pp. 58-61).
The solubility of two related series of each three triazine compounds has been determined in supercritical CO2, at 40 °C and pressures between 80 and 220⋅105 Pa. A high pressure small volume cell with adjustable optical path and built-in circulation pump has been constructed to be used with quartz windows in a Perkin Elmer UV-VIS spectral photometer. At 220 bar solubilities are between 0.3 and 25 g/L, dependent on the specific triazine structure. The isothermal pressure dependence of the solubility could be modelled using the pressure dependent dielectric constant of CO2 as the only variable.
Determination of chlorinated paraffins in cutting fluids and lubricants by A. Randegger-Vollrath (pp. 62-68).
An analytical routine procedure to classify chlorinated paraffins in technical products such as cutting fluids and lubricants is presented. Classification is based on chain length and chlorination degree (short chain, highly chlorinated congeners being subject to legal restrictions). After sample clean up with solid phase extraction over silica, screening is performed with gas chromatography and electron capture detection (ECD). Positive identification and quantitation is then performed with gas chromatography/mass spectrometry using negative chemical ionisation (NCI). Both methods show good reproducibility and repeatability and the average recovery of the chlorinated paraffins with the NCI method is 98%. The detection limits for restricted paraffins in samples range between 0.02–0.08% (w/w) for the ECD method and between 0.2–2.6% (w/w) for the NCI method. The procedure has been applied successfully to the analysis of 37 cutting fluids or lubricants. Short chain, highly chlorinated paraffins were detected in 8 (21%) samples in concentrations from 1 to 70% (w/w). The described procedure can be recommended as an analytical routine method for supervising future legal restrictions on the use of chlorinated paraffins in cutting fluids and lubricants.
Comparison of passive and active sampling methods for the determination of nitrogen dioxide in urban air by Oddvar Røyset (pp. 69-73).
Three different methods for sampling and determination of nitrogen dioxide in urban air are compared: an NO/NOx-monitor and an active (pumped) and a passive sampling method. For the latter two methods, sodium iodide is used as absorbent. For weekly averages the results from the passive sampler are within 10–20% of the results for the two other methods in the concentration range 15–30 μg NO2/m3. The detection limit for the passive sampler is 1 μg NO2/m3 (7 days), the precision is 5% and the accuracy is estimated to 20%. The active iodide method agrees very well with the NO/NOx-monitor. Compared on 24 h basis for a period of 3 months, covering a concentration range of 5–45 μg NO2/m3, the deviation between the two methods is within 5%, and the absorption capacity of the iodide reagent is excellent as the breakthrough is below 1%.
Study of the preconcentration and determination of ultratrace rare earth elements in environmental samples with an ion exchange micro-column by W. Zhu; E. W. B. de Leer; M. Kennedy; G. J. F. R. Alaerts (pp. 74-80).
A study was carried out on the preconcentration of ultratrace rare earth elements (REEs) in environmental samples with a micro ion-exchange column and determination by inductively coupled plasma mass spectrometry (ICP-MS). The preconcentration parameters were optimized and the REE recovery was ca. 100% in the pH range 4 to 6 with an ionic strength (μ) less than 0.18. The ion-exchange column capacity with respect to REEs was estimated as 0.96 mmol/g. The linear response coefficients ranged from 0.995 to 0.997 at the pg mL–1 level. The concentration in the blank could be minimized (0.09 to 3.1 pg mL–1) if the buffer solution and the water were purified. The detection limits ranged from 0.03 to 0.40 pg mL–1, for a preconcentration factor of 100. The precision and accuracy of the method was evaluated with a synthetic standard solution and real samples. Results indicated that the REE recovery ranged from 88.1% to 100.2%, and the RSD ranged from 2.7% to 6.7%. Satisfactory results were achieved when this method was applied for the determination of REEs in raw water, purified water and tap water, as well as in environmental aquatic samples. Meanwhile, the method is simple and flexible.
Laser-induced fluorescence determination of thallium in sediments by V. Cheam; J. Lechner; R. Desrosiers (pp. 81-85).
A simple dissolution procedure is decribed for sediments to be analyzed for thallium by Laser-Excited Atomic Fluorescence Spectrometry (LEAFS). It simply uses a nitric – hydrofluoric acid mixture at room temperature (a “cold dissolution” procedure as opposed to the hot acid digestion) followed by a dilution with water (as opposed to the tedious steps of separation and preconcentration). Excellent accuracy (91–106% recoveries) and precision (4–10% relative standard deviation) were demonstrated by the use of five sediment reference materials of diverse origins. The detection limit was estimated to be 0.5 ng/g of thallium. Additionally, a hot plate digestion procedure, using an in-house designed semi-enclosed Teflon beaker, was also investigated; its analytical results agreed with certified values and confirmed the adequacy of the cold dissolution technique. The method is being applied to study the sediment – water interactions in lake environments.
Distillation preconcentration and clean-up of aqueous samples for direct aqueous injection-gas chromatographic determination of volatile polar organic pollutants by Bogdan Zygmunt (pp. 86-89).
The applicability of distillation to concentrate and clean up heavily loaded aqueous samples for the analysis of volatile polar organic compounds by means of direct aqueous injection-gas chromatography was studied. Recoveries for acetone, acetonitrile, acrolein, acrylonitrile, butanone, 1,4-dioxane, ethyl acetate, and 3-pentanone were in the range of 60.6 to 73.4% with relative standard deviations of 3.6 to 5.5%. The corresponding enrichment factors were in the order of 200. The recovery did not depend on the concentration in the studied range of 0.70 to 89 μg/kg. The detection limits with the mass selective detector operating in the selected ion monitoring mode were in the order of 0.1 μg/kg. The method was successfully applied to treated waste water from a pharmaceutical factory. The content of the above analytes in the real sample ranged from below 0.1 to ca. 83 μg/kg.
Enhanced recovery of chlorophenols from surface waters using polymer based extraction cartridges by R. Schilling; P. J. Clarkson; M. Cooke (pp. 90-94).
The effectiveness of a new polymer based solid phase extraction cartridge (SDB 1) to recover phenolic compounds from aqueous samples has been evaluated by comparison of performance against conventional silica based cartridges. The polymer based material is found to be much more retentive, requiring a larger volume of solvent to achieve maximum recovery. Recovery efficiency is enhanced if the recovery solvent (methanol) is acidified to 0.1% with trifluoroacetic acid. The optimised extraction procedure has been applied to surface water samples and yields quantitative recovery at the 10 ng ml-1 level of all nine phenols studied.
Sensitive and selective determination of metabolically formed trans-dihydrodiols and phenols of benzo[a]pyrene in water and urine samples by HPLC with amperometric detection by E. Fischer; G. Henze; K. L. Platt (pp. 95-99).
A method has been developed to separate hydroxylated metabolites of the carcinogenic polycyclic aromatic hydrocarbon benzo[a]pyrene, i. e. trans-4,5-, 7,8-, 9,10-dihydrodiol and 1-, 3-, 7-, and 9-phenol, by HPLC with amperometric detection employing an isocratic methanol/water eluent (70:30, v/v) containing 0.5 g/L sulfuric acid and 1 g/L lithium perchlorate. Compared with the usually applied fluorescence (λex = 265 nm, λem = 460 nm) and ultraviolet (λ = 265 nm) detection, the amperometric technique is about 2–12 times more sensitive for the determination of all metabolites investigated. The method was applied to the determination of the seven metabolites of benzo[a]pyrene in different water samples and in urine after solid-phase extraction (SPE). The results obtained by HPLC with amperometric detection after SPE enrichment from an aqueous extract of a soil sample and from the urine of a rat intragastrically treated with benzo[a]pyrene agreed well with the values determined with fluorescence and/or UV detection.
Monosegmented flow-analysis of slow enzymatic reactions: Determination of triglycerides in serum by A. N. Araújo; José A. M. Catita; José L. F. C. Lima; Elias A. G. Zagatto (pp. 100-103).
A monosegmented flow system (MCFA) is proposed to achieve slow enzymatic spectrophotometric determinations, here applied to the determination of triglycerides in blood serum. The sample (4.5 μL), enzymatic reagent (150 μL) and an air plug (100 μL) are simultaneously inserted into a carrier stream buffered to pH 7.9 (Tris ⋅ HCl). In order to avoid the cumbersome step of air removal, a relocating detector was used. This system handles about 60 samples/h, yielding precise results (r.s.d. usually<2.5%). Sensitivity is 56 mAU ⋅ L/mmol up to 6 mmol/L triglycerides. Accuracy was assessed by running 50 samples already analysed by a conventional procedure yielding the equation CMCFA(mmol/L)=1.00(±0.04) CRef(mmol/L)−0.03(±0.08); r=0.990.
Determination of ionizable groups of proteins by potentiometric titration in concentrated solutions of guanidine hydrochloride by J. C. Masini; Oswaldo E. S. Godinho; Luiz M. Aleixo (pp. 104-111).
A linearization method based on modified Gran functions, and a general nonlinear regression program were used to study potentiometric titration curves of denatured ovalbumin and lysozyme in 6 mol L–1 guanidine hydrochloride medium with the aim of determining the ionizable species. With both numerical techniques it was possible to determine the sum of the carboxylic groups, the imidazol, the α-amine, and the sum of ɛ-amine, phenolic and sulfhydryl groups, if the protein is completely denatured, and assumes a randomly coiled conformation. A total of 87.8 ± 2.5 and 20.7 ± 0.6 groups per mol were determined in the ovalbumin and lysozyme, respectively. These values are very close to the 88 and 21 groups expected by aminoacid composition of both proteins, indicating that all ionizable groups were exposed to the solvent. For ovalbumin the distribution of groups was very similar to that expected by the aminoacid composition, but for lysozyme some anomalies were observed, suggesting the existence of interactions between ionizable groups, altering the dissociation constants.
Cathodic stripping voltammetry of NADH in presence of Cu2+ by M. M. Kamal (pp. 112-116).
The adsorption and accumulation of NADH and the Cu2+-NADH system at the mercury electrode surface was examined using differential pulse cathodic stripping voltammetry (DPCSV). The method was developed for analytical trace determination of NADH. Experimental and operational parameters for the quantitative determination of NADH were optimized and the detection limit was found to be 9.960 × 10–8 mol/L. The effect of some interferences (e.g. purine compounds, amino acids and some metal ions) was considered.
Ion trap MS/MS of polychlorinated dibenzo-p-dioxins and dibenzofurans: confirming the concept of the molar response by T. Wiedmann; H. Schimmel; K. Ballschmiter (pp. 117-119).
It has been shown that the concept of molar response, which is applicable to single ion monitoring of M+, can also be employed for ion trap MS/MS measurements, simplifying the determination of PCDD/PCDF by an extended IDA approach.
Development of a calibration instrument for the dynamic generation of organic vapors by György Barkó; József Hlavay (pp. 119-121).
A computer controlled automatic calibration apparatus for the dynamic generation of organic vapors was developed. A calibration loop was filled by diffusion with organic compounds and diluted using nitrogen as a carrier gas. The compound holder pipe was thermostated at 40° C. Fittings were made of PTFE and the valves were constructed of stainless steel. Moisture interferences were reduced using a Nafion membrane filter. The vapor generator was validated by a gas chromatographic method. The measured and calculated values were compared and good correlation (r = 0.9903) was found.
Amperometric sensor for hydrogen peroxide, based on Cu2O or CuO modified carbon paste electrodes by Rasa Garjonyte; A. Malinauskas (pp. 122-123).
Carbon paste electrodes, modified by Cu2O or CuO, were prepared and tested as sensors for hydrogen peroxide in aqueous solutions. They show a cathodic response to the analyte ranging from 0.45 to 0.14 mA/cm2 for 1 mmol/L hydrogen peroxide for solutions of pH 5.2 and 7.3, respectively, at a working potential of –0.4 V vs. Ag/AgCl. The cathodic operation mode used diminishes or excludes the possibility of anodic discharge of contaminants usually present in biological fluids, and enables the use of the sensors in bioanalytical systems based on enzymes.
Determination of the stoichiometry of mixed microcrystals KxCsyZnCl4 using instrumental neutron activation analysis by E. Mauerhofer; S. J. Reddy (pp. 123-125).
Instrumental neutron activation analysis (INAA) has been employed as an absolute method for the determination of the stoichiometry of mixed microcrystals KxCsyZnCl4 with a weight ranging between 20 and 50 μg. The reliability of the method has been checked with the pure substances KCl, NaCl, CsCl and RbCl, for which the mean value of the ratio Cl/X was found to be 1.04 (3).
Determination of cobalt by substoichiometric extraction with β-hydroxy-naphthaldoxime by J. Dutta; S. Basu (pp. 125-127).
A substoichiometric radiochemical solventextraction method is described for the determination of cobalt, employing β-hydroxy-naphthaldoxime and chloroform as reagent and extractant, respectively. The extraction behaviour of the complex of cobalt with the reagent in the pH-range 8–9.5 and the effects of various metal ions on the extraction are critically studied. The method is used to determine the cobalt content in some pharmaceutical drugs.
Sensitive spectrophotometric determination of vanadium with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol after extraction with N-benzoyl-N-phenylhydroxylamine by C. Zucchi; M. Forneris; L. Martínez; R. Olsina; E. Marchevsky (pp. 128-130).
A selective and precise spectrophotometric determination of vanadium(V) is performed after preceding extraction with N-benzoyl-N-phenylhydroxylamine (BPHA). The color is developed in a water-ethanol solution with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (5-Cl-DMPAP). The molar absorptivity at 588 nm is (6.57 ± 0.05) × 104 L mol–1 cm–1 at pH 2.1. The method permits the determination of vanadium (V) at trace levels in the presence of large amounts of other ions. It is applied to the determination of vanadium in aluminium (analytical reagent grade) and in human hair. High accuracy and precision is obtained.
Chemiluminescence flow system for the determination of Fe(II) and Fe(III) in water by W. Qin; Z. J. Zhang; F. C. Wang (pp. 130-132).
A novel chemiluminescence (CL) flow system has been developed for the sequential determination of Fe(II) and Fe(III) in water. Fe(II) was detected by its catalytic effect on the CL reaction between luminol immobilized on an anion exchange resin column and dissolved oxygen; Fe(III) was determined by difference measurement after on-line conversion to Fe(II) in a reducing mini-column packed with Cu plated Zn granules. For both ions, the calibration graph was linear in the range 1 × 10–9 to 1 × 10–6 g/mL, and the detection limit was 4 × 10–10 g/mL. A complete analysis could be performed in 1.5 min with a relative standard deviation of less than 5%. The system could be reused for over 200 times and has been applied successfully to the determination of Fe(II) and Fe(III) in natural water samples.
Determination of total dissolved phosphorus in water samples by axial inductively coupled plasma atomic emission spectrometry by J. L. M. de Boer; U. Kohlmeyer; Peter M. Breugem; Trijntje van der Velde-Koerts (pp. 132-136).
A procedure was developed to determine total dissolved phosphorus in groundwater-like samples using axial ICP-AES. Severe and peculiar matrix effects (strongly positive at lower and leveling off at higher matrix concentrations) in the presence of Na and Ca were observed. To reduce these matrix effects, a double approach was utilized consisting of a so-called minimum matrix in combination with an internal standard (Ga in this case). The ‘minimum matrix’ (small amounts of K, Mg and Na) was only added to the standard solution(s) used for the calibration. The detection limit for the whole procedure was 12 μg/L using the P213 nm line. Residual matrix effects were less than 3% (P213 nm line).
Spectrophotometric method for the determination of 1,2-propylene glycol by T. Machate; A. Kettrup (pp. 137-138).
A spectrophotometric method is proposed for the determination of 1,2-propylene glycol. It is based on the ADH/ AlDH catalyzed oxidation of propylene glycol by NAD+. The NADH formed is measured at 340 nm. Alcohol dehydrogenase from equine liver was found to be much more effective than that of yeast. No enantiomeric selectivity for s(+) propylene glycol was observed. A linear relation was found in the concentration range from 5 to 50 mg/L. The method achieves a correlation coefficient of r = 0.996 and a relative standard deviation of 1.37%. The limit of quantitation was calculated to 9.6 mg/L. Since the total reaction volume was restricted to 800 μL, only 2.8 units of AlDH and 8 units of ADH were sufficient to develop the final absorption within 30 min.
Development of a modified beta-cyclodextrin based fluorosensor for dipyridamole by Zhilong Gong; Zhujun Zhang (pp. 138-140).
2,6-O-diethyl-β-cyclodextrins were prepared and immobilized onto silica gel to develop a fluorosensor for dipyridamole. The analytical performance characteristics of the proposed sensor for analysis of dipyridamole were as follows: the detection limit was 0.8 nmol/L with a relative standard deviation of 1.4% for 10 determinations of 50 nmol/L of dipyridamole. The modification of β-CD improved the sensitivity and selectivity for measuring dipyridamole. The recommended method has been successfully tested for the determination of dipyridamole in clinical samples (urine and pharmaceutical preparations).
Field method for the micro-quantitative determination of tetracycline in human urine by S. A. Nabi; E. S. M. Abu-Nameh; N. Rahman; M. I. H. Helaleh (pp. 140-141).
A simple, fast and sensitive titrimetric method has been developed for the determination of tetracycline hydrochloride in human urine using m-dinitrobenzene as color agent and Dowex 1 × 8 as detection medium.