Validated method for the determination of the novel organo-ruthenium anticancer drug NAMI-A in human biological fluids by Zeeman atomic absorption spectrometry

NAMI-A is a novel ruthenium-containing experimental anticancer agent. We have developed and validated a rapid and sensitive analytical method to determine NAMI-A in human plasma, plasma ultrafiltrate and urine using atomic absorption spectrometry with Zeeman correction. The sample pretreatment procedure is straightforward, involving only dilution with an appropriate hydrochloric acid buffer-solution. Because the response signal of the spectrometer depended on the composition of the sample matrix, in particular on the amount of human plasma in the sample, all unknown samples were diluted to match the matrix composition in which the standard line was prepared (plasma-buffer 1:10 v/v). This procedure enabled the measurement of samples of different biological matrices in a single run. The validated range of determination was 1.1-220 microM NAMI-A for plasma and urine, and 0.22-44 microM for plasma ultrafiltrate. The lower limit of detection was 0.85 microM in plasma and urine and 0.17 microM in plasma ultrafiltrate. The lower limit of quantitation was 1.1 and 0.22 microM, respectively. The performance of the method, in terms of precision and accuracy was according to the generally accepted criteria for validation of analytical methodologies. The applicability of the method was demonstrated in a patient who was treated in a pharmacokinetic phase I trial with intravenous NAMI-A.     

Validated method for the determination of carboplatin in biological fluids by Zeeman atomic absorption spectrometry

We have developed and validated a rapid, simple and sensitive analytical method, based on Zeeman atomic absorption spectrometry, for the quantitative analysis of carboplatin in human plasma, plasma-ultrafiltrate (UF), saliva and urine. The sample pretreatment is simple and only involves dilution of the samples with a solution containing 0.15 mol/L NaCl and 0.2 mol/L HCl in water (diluent). The caroplatin concentrations in the different biological matrices could be quantified using a standard curve constructed in plasma UF: diluent (1:10; v/v). The validated range of determination was 0.24 to 242 mol/L of carboplatin in plasma UF, 0.84 to 242 mol/L in plasma, 0.12 to 3.64 mol/L in saliva, and 2.02 mol/L to 12.1 mmol/L in urine. Matrix-effects were not observed. The stability of carboplatin (determined as Pt) in biological samples stored at –20°C was checked for a period of 8 months; no losses occurred during this period. The performance of the method, in terms of accuracy and precision, fitted well within the generally accepted criteria for validation of analytical methodologies. The proposed method was utilized in a pharmacokinetic study in one patient to demonstrate the usefulness of the assay.     

Rapid determination of lead and cadmium in biological fluids by electrothermal atomic absorption spectrometry using Zeeman correction

Procedures for the electrothermal atomic absorption spectrometric determination of lead and cadmium in urine, serum and blood are developed. For serum and blood, the samples are diluted by incorporating 0.015% (w/v) Triton X-100 and 0.1% (w/v) ammonium dihydrogenphosphate to the solutions, which are then introduced directly into the furnace. A solution containing 15% (w/v) hydrogen peroxide and 0.65% (w/v) nitric acid is also introduced into the atomizer by means of a separate injection. Zeeman-based correction is recommended. Both conventional and fast-heating programs are discussed. Calibration is carried out using the standard additions method. The reliability of the procedures is checked by analyzing three certified reference materials and by recovery studies.     

Validated method for the determination of platinum from a liposomal source (SPI-77) in human plasma using graphite furnace Zeeman atomic absorption spectrometry

A sensitive analytical method based on flameless atomic absorption spectrometry with Zeeman correction has been validated for the quantitative determination in human plasma of platinum originating from cisplatin in a liposomal source, SPI-77. The performance of the method was acceptable over a sample concentration range of 0. 125-1.25 micromol platinum/L and the lower limit of quantification was determined to be 1.25 micromol platinum/L in undiluted clinical samples. The performance data of the assay were investigated using both a calibration curve with carboplatin in plasma ultrafiltrate and diluted human plasma samples spiked with SPI-77. The recoveries, between-day and the within-day precisions of both methods of calibration were not significantly different allowing carboplatin ultrafiltrate calibration standards to be used to quantify platinum derived from SPI-77 in human plasma. Apparently, the liposomal formulation had no significant influence on the determination of platinum. The usefulness of the presented method was demonstrated in a phase I clinical and pharmacokinetic study. In addition, in vitro experiments were carried out to determine the distribution of SPI-77 in blood. The results indicated that platinum from SPI-77 mainly concentrates in plasma and that binding to and/or endocytosis in red blood cells is negligible.     

Validated method for the determination of platinum from a liposomal source (SPI-77) in human plasma using graphite furnace Zeeman atomic absorption spectrometry

A sensitive analytical method based on flameless atomic absorption spectrometry with Zeeman correction has been validated for the quantitative determination in human plasma of platinum originating from cisplatin in a liposomal source, SPI-77. The performance of the method was acceptable over a sample concentration range of 0.125–1.25 μmol platinum/L and the lower limit of quantification was determined to be 1.25 μmol platinum/L in undiluted clinical samples. The performance data of the assay were investigated using both a calibration curve with carboplatin in plasma ultrafiltrate and diluted human plasma samples spiked with SPI-77. The recoveries, between-day and the within-day precisions of both methods of calibration were not significantly different allowing carboplatin ultrafiltrate calibration standards to be used to quantify platinum derived from SPI-77 in human plasma. Apparently, the liposomal formulation had no significant influence on the determination of platinum. The usefulness of the presented method was demonstrated in a phase I clinical and pharmacokinetic study. In addition, in vitro experiments were carried out to determine the distribution of SPI-77 in blood. The results indicated that platinum from SPI-77 mainly concentrates in plasma and that binding to and/or endocytosis in red blood cells is negligible.     

Determination of arsenic in biological fluids by electrothermal atomic absorption spectrometry

A procedure for the determination of the total content of arsenic in urine, serum and blood by electrothermal atomic absorption spectrometry (ETAAS) is described. Zeeman correction is used to compensate the high background signals. The samples are diluted (1 + 1 for urine and 1 + 3 for both serum and blood samples) in a medium containing 0.1% w/v Triton X-100 before being introduced directly into the furnace. A solution containing 15% w/v hydrogen peroxide, 0.65% w/v nitric acid and 0.5% w/v nickel is also introduced into the atomizer by means of a separate injection. Calibration is carried out against aqueous standards for blood and serum samples and using the standard additions method for urine samples. The detection limit is 20 pg (2 ng ml-1). The reliability of the procedure is checked by analyzing three certified reference materials and by recovery studies.     

The use of the Zeeman effect for the background correction in atomic absorption analysis of biological fluids

The analytical technique based on the Zeeman effect for the correction of non-specific absorptions is used for the quantitative analysis of lead traces in human blood plasma. The analysis of lead traces in biological fluids by means of flameless atomic absorption is usually rather difficult to perform, owing to the presence of background absorptions in the atomization step. Tests carried out on real matrices with additions of known lead concentrations have often shown the impossibility of getting a sufficient accuracy and characteristic mass necessary for the application of the method as a clinical test. On the other hand, the background correction technique by the Zeeman effect appears to be the most convenient. To check the effectiveness of this correction method, standard solutions with compositions suitable for the production of very strong molecular absorption and light scattering phenomena were analysed; the various results obtained are reported and compared. The investigation was performed on the whole atomic absorption spectral range normally used in spectroscopy by means of different wavelength resonance lines.     

Rapid determination of cadmium in biological tissues by microsampling-cup atomic absorption spectrometry

A microsampling-cup method of atomic absorption spectrometry has been applied to the determination of cadmium in biological tissues. Sample preparation involves homogenizing a known weight of the tissue with a known volume of water, pipetting a suitable dilution of the homogenate into a microsampling cup and drying. Aqueous calibration standards are used. Sensitivity, linear range and reproducibility are adequate for this application. Simplicity and speed make this method preferable to any other reported to date.     

Trace determination of mercury in biological materials by flameless atomic absorption spectrometry

A new rapid wet-ashing procedure for biological material is described. The samples are boiled for 5–10 min in a mixture of nitric and hydrobromic acid under reflux. Mercury is then determined by the flameless cold-vapour, atomic absorption technique and complete release is shown to occur even when the fat present is not fully decomposed. The results are discussed with regard to the normal bromine and iodine content of marine samples. The enhancement obtained with bromine can easily be compensated by digesting the standards. Iodine, however, reduces the peak heights and the content of this element must be judged separately for samples other than fish, which can always be safely analysed without interference.     

Rapid determination of lead in biological tissues by microsampling-cup atomic absorption spectrometry

Lead can be determined in kidney, liver, and lung tissues by a rapid technique which does not require ashing or acid digestion of the sample. The tissue is homogenized with water, an aliquot of the homogenate is pipetted into a microsampling cup, and lead is determined directly by atomic absorption spectrometry. Calibration is by lead standards in a whole blood matrix. Results correlate well with those obtained by a wet-ashing procedure. The sensitivity (0.01 μg Pb g^-1 wet tissue) permits the analysis of typical tissues with good precision. The procedure is rapid, and its simplicity minimizes the risk of contamination by extraneous lead during sample preparation.     

Nickel and strontium nitrates as modifiers for the determination of selenium in wine by Zeeman electrothermal atomic absorption spectrometry

A mixed matrix modifier of nickel and strontium nitrates was used as a chemical modifier for the determination of selenium in wines by Zeeman electrothermal atomic absorption spectrometry. Wine samples were heated on a boiling water bath with small amounts of nitric acid and hydrogen peroxide. For complete elimination of interference, especially from sulfates and phosphates, selenium is complexed with ammonium pyrolidinedithiocarbamate (APDTC), extracted into methyl isobutyl ketone (MIBK), and measured by ETAAS. The graphite furnace temperature program was optimized for both aqueous and organic solutions. Pyrolysis temperatures of 1300 degrees C and 800 degrees C were chosen for aqueous and organic solutions, respectively; 2700 degrees C and 2100 degrees C were used as optimum atomization temperatures for aqueous and organic solutions, respectively. The optimum modifier mass established is markedly lower than those presented in the literature. The platform atomization ensures pretreatment stabilization up to 1100 degrees C and 1600 degrees C, respectively, for organic and aqueous selenium solutions. The procedure was verified by the method of standard addition. The investigated wine samples originated from the different regions of the Republic of Macedonia. The selenium concentration varied from not detectable to 0.93 microg L(-1).     

Nickel and strontium nitrates as modifiers for the determination of selenium in wine by Zeeman electrothermal atomic absorption spectrometry

A mixed matrix modifier of nickel and strontium nitrates was used as a chemical modifier for the determination of selenium in wines by Zeeman electrothermal atomic absorption spectrometry. Wine samples were heated on a boiling water bath with small amounts of nitric acid and hydrogen peroxide. For complete elimination of interference, especially from sulfates and phosphates, selenium is complexed with ammonium pyrolidinedithiocarbamate (APDTC), extracted into methyl isobutyl ketone (MIBK), and measured by ETAAS. The graphite furnace temperature program was optimized for both aqueous and organic solutions. Pyrolysis temperatures of 1300?°C and 800?°C were chosen for aqueous and organic solutions, respectively; 2700?°C and 2100?°C were used as optimum atomization temperatures for aqueous and organic solutions, respectively. The optimum modifier mass established is markedly lower than those presented in the literature. The platform atomization ensures pretreatment stabilization up to 1100?°C and 1600?°C, respectively, for organic and aqueous selenium solutions. The procedure was verified by the method of standard addition. The investigated wine samples originated from the different regions of the Republic of Macedonia. The selenium concentration varied from not detectable to 0.93 μg L^–1.     

A direct solid sampling electrothermal atomic absorption spectrometry method for the determination of silicon in biological materials

A solid sampling electrothermal atomic absorption spectrometry method for direct determination of trace silicon in biological materials was developed and applied to analysis of pork liver, bovine liver SRM 1577b and pure cellulose. The organic matrix was destroyed and expelled from the furnace in the pyrolysis stage involving a step-wise increasing the temperature from 160 °C to 1200 °C. The mixed Pd/Mg(NO₃)₂ modifier has proved to be the optimum one with respect to the achievement of maximum sensitivity, elimination of the effect of the remaining inorganic substances and the possibility of using calibration curves measured with aqueous standard solutions for quantification. For the maximum applicable sample amount of 6 mg, the limit of detection was found to be 30 ng g^− 1. The results were compared with those obtained by different spectrometric methods involving sample digestion, by electrothermal atomic absorption spectrometry using slurry sampling, by wavelength dispersive X-ray fluorescence spectrometry and by radiochemical neutron activation analysis. The method seems to be a promising one for analysis of biological materials containing no significant fraction of silicon in form of not naturally occurring volatile organosilicon compounds. The still incessant serious limitations and uncertainties in the determination of trace silicon in solid biological materials are discussed.     

Sensitive method for determination of captopril in biological fluids by gas chromatography-mass spectrometry

A sensitive method for the determination of captopril in blood and urine by gas chromatography-mass spectrometry is described. In order to prevent oxidative degradation of captopril, its sulph-hydryl group was immediately protected by treatment with N-ethylmaleimide (NEM), and the resulting NEM adduct was then converted into the bis(pentafluorobenzyl) derivative. Derivatized captopril was separated on a 2% OV-1 column, exhibiting a single peak of the correct theoretical shape. The detection limit was estimated to be 100 pg by using S-benzylcaptopril as an internal standard. The blood level and urinary excretion of unchanged captopril orally administered to dogs were determined by the proposed method. In addition, epimerization of the proline moiety and formation of the sulphoxide or sulphone through the esterification step are also described.     

Determination of copper in sulfide minerals by Zeeman electrothermal atomic absorption spectrometry

A method for the determination of copper in some sulfide minerals (lorandite, realgar, orpiment, marcasite, stibnite, galenite and sphalerite) by Zeeman electrothermal atomic absorption spectrometry is presented. After the dissolution of samples, copper was extracted with sodium diethyldithiocarbamate into different organic solvents (carbon tetrachloride, chloroform and methylisobutyl ketone) at pH 11.0–12.0. The procedure was verified by standard addition. The standard deviation (SD) for 0.5 ng Cu is 0.01 ng, the relative standard deviation ranges from 3.5 to 5.5% and the detection limit of the method, calculated as 3 SD of the blank, was found to be 0.05 μg · g^–1.     

Validation of mercury determination by solid sampling Zeeman atomic absorption spectrometry and a specially designed furnace

Certified reference materials (CRMs) of different origin were used to validate the direct determination of total mercury by solid sampling Zeeman atomic absorption spectrometry (SS-ZAAS) and a specially designed furnace. The temperature program provides only for one step. Atomisation of mercury and pyrolysis of the matrix is performed at a constant temperature in the range of 900–1000 °C. Calibration points achieved by CRMs and aqueous solutions are covered by one calibration line, indicating the absence of matrix effects. Relatively high amounts of chlorine, known for causing problems in mercury determination do not influence analytical results. The excellent accuracy of the method results in a very good agreement with the certified values. The precision of SS-ZAAS measurements in a range from 0.5 to 50 ng Hg does not exceed 3% R.S.D. A limit of quantification of 0.008 μg g⁻¹ Hg was achieved.     

Determination of copper in sulfide minerals by Zeeman electrothermal atomic absorption spectrometry

A method for the determination of copper in some sulfide minerals (lorandite, realgar, orpiment, marcasite, stibnite, galenite and sphalerite) by Zeeman electrothermal atomic absorption spectrometry is presented. After the dissolution of samples, copper was extracted with sodium diethyldithiocarbamate into different organic solvents (carbon tetrachloride, chloroform and methylisobutyl ketone) at pH 11.0–12.0. The procedure was verified by standard addition. The standard deviation (SD) for 0.5 ng Cu is 0.01 ng, the relative standard deviation ranges from 3.5 to 5.5% and the detection limit of the method, calculated as 3 SD of the blank, was found to be 0.05 μg · g^–1. Received: 26 May 1997 / Revised: 10 September 1997 / Accepted: 16 September 1997