Shelf-life of99mTc(Sn)-pyrophosphate

The effect of the preparation conditions on the in vitro stability of^99mTc (Sn)-pyrophosphate kit solution has been examined. To extend the shelf-life of the preparation, different methods of protection were tested. Nitrogen purging stabilizes the kit for at least 6 h after labeling when the content of^99mTc-pertechnetate raises to about 5%. However, this method is ineffective in the presence of hydrogen peroxide. The protecting ability of two chemicals was also determined. Gentisic acid gave good results. In the presence of 50 g of gentisic acid per ml of the kit the content of pertechnetate was 1–2% throughout the examined time interval. To eliminate the influence of hydrogen peroxide (6 g per ml of the kit) about 100 g of gentisic acid is needed. N, N-diphenyl-p-phenylenediamine (DPPD) performs some protecting effect only when used in the samples protected by nitrogen purging. However its protecting ability is lower that in the case of gentisic acid.     

Effect of experimental conditions on the in vitro stability of99mTc (Sn)-pyrophosphate

The in vitro stability of^99mTc (Sn)-PyP as a function of experimental conditions of the preparation of the kit and time elapsed after labeling has been tested. The preparation was protected by using nitrogen-purged reactant solutions and kit vials and by ascorbic acid. The samples under nitrogen are stable for 6 h when the content of^99mTc-pertechnetate raises to 5%. The best stability was achieved by addition of 5 g of ascorbic acid per ml of the kit (content of^99mTc-pertechnetate about 0.5%). To accelerate the decomposition, exogenous hydrogen peroxide was used. In this case it was found that the presence of 10 g of ascorbic acid inhibits the effect both of oxygen and peroxide (6 g H₂O₂/ml of the kit). Radiochemical purity of^99mTc (Sn)-PyP remains practically unchanged for 6 h (content of^99mTc-pertechnetate about 0.5%).     

Statistical Evaluation of the Quality Control Results of 99mTc(Sn)-DPD

The results of the quality control of ^99mTc-DPD produced during five consequtive years are statistically evaluated. Radiochemical purity of the kit determined in 75 batches was 98.3±1.3%. TLC on silica gel with the mixture of acetone and methanole (1:1, v/v) was used to determine the content of free pertechnetate. The labeled complex and ^99mTc-hydrolyzate was separated by using ascending paper (Schleicher & Schull) chromatography and lN NaCl as the mobile phase. Reliable results were obtained showing that the content of the impurities ^99mTc-pertechnetate and ^99mTc-hydrolyzate is 1.7±1.3% and 3.4±2.1%, respectively. The biodistribution depends on the quantity of DPD. For the animal experiments its content should be 70–80 g/kg b.w. The experiments revealed that the mean value of bone distribution was 8.8±1.9%/g and in muscles 0.043± 0.42%/g. The uptake in liver and kidneys was below 3%, i.e., 0.65±0.29 and 1.71±0.68%/organ, respectively. The bone/muscle ratio should be at least 160. The analysis shows that the obtained values are arranged around their, statistically allowed, mean values.     

Comparative quality control of some bone-seeking99mTc radiopharmaceuticals by gel chromatography

The radiochemical purity of the three osteopatic ligands:^99mTc(Sn)-PyP,^99mTc(Sn)-DPD and^99mTc(Sn)-MDP has been determined by gel chromatography on Sephadex. The results of the analyses strongly depend on the composition of the eluent. The dilution effect of pure saline as eluent was observed in all the preparations examined. The most sensitive was found to be^99mTc(Sn)-PyP. The retention of^99mTc activity bound to the gel matrix (^99mTc-hydrolyte) was over 30%. The diphosphonates were found to be more stable (retention 10–15%). The retention is substantially lower, i.e. a high recovery of the labeled complexes is obtained when the eluent contains the ligand. The best results are obtained when the eluent contains the same concentrations of ligand and reductant as in the labeled complex. There was no significant difference in the behavior of the given radiopharmaceuticals prepared as a fresh solution and in the freeze-dried kit.     

Preparation of 99Mo/99mTc generator based on alumina 99Mo-molybdate (VI) gel

In this work alumina ⁹⁹Mo-molybdate (VI) gel is evaluated as a column matrix for use in the preparation of small chromatographic column type ^99mTc generator. Alumina molybdate (VI) gel is prepared by dissolving inactive MoO₃ with aluminum foil in 5 M NaOH solution containing ⁹⁹Mo radiotracer. After complete dissolution, 0.5 H₂O₂ was added to the reaction mixture solution and acidified to pH 5.5 with concentrated HNO₃. The formed AlMo precipitate was washed with NaNO₃ solution, dried at 50 °C for 24 h and then packed in the form of a chromatographic column for elution of the generated ^99mTc radionuclide with physiological saline solution (0.9 % NaCl). Greater than 86 % of the generated ^99mTc activity is immediately and reproducibly eluted with passing 10 mL of the saline solution through 2.0 g of alumina ⁹⁹Mo-molybdate column bed at a flow rate of about 1.0 mL/min. The high radiochemical ≥98.6 % TcO₄ ^?, radionuclidic ≥99.90 % ^99mTc and chemical purities of the eluates satisfy the specifications for use in nuclear medicine.     

Effects of first dimension eluent composition in two-dimensional liquid chromatography

Comprehensive two-dimensional liquid chromatography (LC×LC) has received a great deal of attention during the past few years because of its extraordinary resolving power. The biggest advantage of this technique is that very high peak capacities can be generated in a relatively short time. Numerous approaches to maximize the peak capacity in LC×LC have been employed. In this work we investigate the impact of the first dimension mobile phase on selectivity. LC×LC has several potential advantages over one-dimensional LC (1DLC) in that unconventional solvents, at least in reversed-phase LC, can be used. For example, solvents which strongly adsorb in the UV in the first dimension are not problematic in LC×LC. This so because the UV detector is placed after the second dimensional column, as pulses of the first dimension eluent arrive at the second dimensional column, they elute well before the solutes of interest and therefore do not interfere at all with detection of solute peaks. So far, the most widely used solvents in reversed-phase 1DLC are methanol and acetonitrile. However, the "UV advantage" of 2DLC allows us to employ UV active solvents, such as acetone. We compare their differential selectivities to that of acetonitrile for the separation of 23 indole acetic acids of interest in plant biology. We also apply them to the separation of a maize seed extract, a very complex sample. In both sample sets, mobile phase composition can be an important parameter to increase the orthogonality of the two dimensions and thus, to increase the effective peak capacity of LC×LC.     

A99Mo-99mTc generator based on the use of zirconium molybdophosphate-99Mo gel

A modified⁹⁹Mo–^99mTc gel generator is described. The present generator uses an insoluble zirconium molybdophosphate (ZrMP) gel tagged with⁹⁹Mo. Molybdenum-99 is chemically combined in the gel structure and cannot be eluted from the matrix. The presence of phosphate increases the chemical stability of the gel and decreases the molybdenum breakthrough. The prepared gel is sufficiently porous to permit ready diffusion of^99mTcO ₄ ^– which can be cluted with saline in yields of up to 90%. The gel was found to contain 25.1% Mo, 21.9% Zr, and 0.7% P in a molar ratio of 1.09:1.0:0.09, respectively. The high molybdenum content of the gel allows the use of cheap, non-polluting (n, )⁹⁹Mo. The eluted^99mTc was of high purity and can be used for medical and pharmaceutical applications.     

Influence of the eluent composition on column efficiency in reversed-phase high-performance liquid chromatography

Summary The dependence of column efficiency on the eluent (MeOH/H₂O) composition in a reversed-phase liquid chromatography system within a wide concentration range has been systematically examined. It is shown that when the intracolumn effect of mass transfer and diffusion is the main factor controlling band broadening the column efficiency decreases with the increase of the viscosity of the MeOH/H₂O mixture; on the other hand, when the extra-column effect is the main factor an increase in the viscosity of the eluents will help in improving column efficiency. The column efficiency is also related to the properties of the sample.     

Chemical and biological evaluation of 99mTc (CO)3 and 99mTc complexes of some IDA derivatives

The confirmation that N-substituted imidodiacetic acids, as small and simple ligand systems containing amines and carboxylic acids, could be coordinated to the tricarbonyl core and form inert complexes with [^99mTc (CO)₃(H₂O)₃]⁺, is demonstrated. The HPLC quality control results of ^99mTc-carbonyl tagged IDA molecules, performed by gradient HPLC, have shown that HIDA, EHIDA and p-butyl-IDA form complexes with [^99mTc(CO)₃(H₂O)₃]⁺, with a labeling yield of ~90% for each of ^99mTc(CO)₃ IDA derivatives. However, the changes in the structure of labeled compounds, e.g., EHIDA, influence the changes in the biological behavior. In comparison with ^99mTc-EHIDA, the biliary excretion of ^99mTc(CO)₃ EHIDA was lower, but the urinary excretion higher. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of 99mTc(CO)3-NOET via [99mTc(OH2)3(CO)3]+ precursor and comparative biological studies with 99mTcN-noet

Summary The organometallic precursor fac-[^99mTc(CO)₃(H₂O)₃]⁺ was reacted with N-ethoxy, N-ethyl dithiocarbamate (NOET) in phosphate buffered saline (pH 7.4) at room temperature for 30 minutes to produce the ^99mTc(CO)₃-NOET complex. The radiochemical purity (RCP) of the product was over 90% as measured by thin layer chromatography (TLC). No decomposition of the complex at room temperature (RT) was observed over a period of 6 hours. Its partition coefficient indicated that it was a lipophilic complex. The biodistribution comparison in mice of the ^99mTc(CO)₃-NOET complex and the ^99mTcN-NOET complex showed that the former had a lower heart and brain uptake as compared to that of the latter, suggesting the incorporation of the [^99mTc(CO)₃]⁺ core into the NOET ligand does not improve the biological features as a myocardial imaging agent.     

Effect of eluent composition on retention behavior of anions in ion chromatography on anion-exchangers modified with heparin

Effects of eluent composition on retention behavior of inorganic anions have been investigated in ion chromatography using anion-exchangers modified with heparin. Both cation and anion of the eluent affected the retention of analyte anions and unusual retention behavior was observed on the modified stationary phase. The retention time of anions decreased with decreasing eluent concentration when sodium sulfate, magnesium sulfate and chlorides of alkali metals were used as the eluent, whereas it increased with decreasing eluent concentration when aluminum sulfate, copper sulfate and sulfuric acid were used as the eluent. The retention of nitrate increased in the order of Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ when their chlorides were used as the eluent. When sodium perchlorate and chlorides of alkaline-earth metals were used as the eluent, the eluent should include heparin. Otherwise, the modifier was partially bled from the column.     

MO tripeptide diastereomers (M=99/99mTc, Re): models to identify the structure of 99mTc peptide targeted radiopharmaceuticals

Biologically active molecules, such as many peptides, serve as targeting vectors for radiopharmaceuticals based on 99mTc. Tripeptides can be suitable chelates and are easily and conveniently synthesized and linked to peptide targeting vectors through solid-phase peptide synthesis and form stable TcVO complexes. Upon complexation with [TcO]3+, two products form; these are syn and anti diastereomers, and they often have different biological behavior. This is the case with the approved radiopharmaceutical [99mTcO]depreotide ([99mTcO]P829, NeoTect) that is used to image lung cancer. [99mTcO]depreotide indeed exhibits two product peaks in its HPLC profile, but assignment of the product peaks to the diastereomers has proven to be difficult because the metal peptide complex is difficult to crystallize for structural analysis. In this study, we isolated diastereomers of [99TcO] and [ReO] complexes of several tripeptide ligands that model the metal chelator region of [99mTcO]depreotide. Using X-ray crystallography, we observed that the early eluting peak (A) corresponds to the anti diastereomer, where the Tc=O group is on the opposite side of the plane formed by the ligand backbone relative to the pendant groups of the tripeptide ligand, and the later eluting peak (B) corresponds to the syn diastereomer, where the Tc=O group is on the same side of the plane as the residues of the tripeptide. 1H NMR and circular dichroism (CD) spectroscopy report on the metal environment and prove to be diagnostic for syn or anti diastereomers, and we identified characteristic features from these techniques that can be used to assign the diastereomer profile in 99mTc peptide radiopharmaceuticals like [99mTcO]depreotide and in 188Re peptide radiotherapeutic agents. Crystallography, potentiometric titration, and NMR results presented insights into the chemistry occurring under physiological conditions. The tripeptide complexes where lysine is the second amino acid crystallized in a deprotonated metallo-amide form, possessing a short N1-M bond. The pKa measurements of the N1 amine (pKa approximately 5.6) suggested that this amine is rendered more acidic by both metal complexation and the presence of the lysine residue. Furthermore, peptide chelators incorporating a lysine (like the chelator of [TcO]depreotide) likely exist in the deprotonated form in vivo, comprising a neutral metal center. Deprotonation possibly mediates the interconversion process between the syn and anti diastereomers. The N1 amine group on non-lysine-containing metallopeptides is not as acidic (pKa approximately 6.8) and does not deprotonate and crystallize as do the metallo-amide species. Three of the tripeptide ligands (FGC, FSC, and FKC) were radiolabeled with 99mTc, and the individual syn and anti isomers were isolated for biodistribution studies in normal female nude mice. The main organs of uptake were the liver, intestines, and kidneys, with the FGC compounds exhibiting the highest liver uptake. In comparing the diastereomers, the syn compounds had substantially higher organ uptake and slower blood clearance than the anti compounds.     

Influence of eluent composition on the retention factor of azoles in reversed-phase high-performance liquid chromatography

The linear dependence of the retention factor of indole, imidazole, triazole, and tetrazole derivatives on the acetonitrile content of the mobile phase was studied.     

Retention models in ion chromatography and their use in computer optimization of eluent composition

Computer optimization of eluent composition in ion chromatography can be performed using a retention model to predict elution behaviour of solutes. Approaches to optimization are outlined and some of the more recently published retention models are discussed in terms of the experimental parameters necessary for their implementation and the complexity of calculation necessary to solve the appropriate mathematical relationships in the models.     

Labelling of human serum albumin millimicrospheres (hamm) with99mTc

Human serum albumin microspheres were labelled with^99mTc as a single step kit with radiochemical yields higher than 95%. With respect to the organ distribution in mice, the per cent of injected dose in liver was 78%.     

Separation of carbohydrates by liquid chromatography on silica gel,adding adsorption modificators to the eluent

Summary For the separation of carbohydrates by liquid chromatography, utilizing the intermolecular interaction with amino groups on the surface of the adsorbent, two types of adsorbents were used: silica gel modified by adding to the eluent a diamine, and a chemically bonded phase prepared by the reaction of -aminopropyl triethoxy silane with silica gel. Mono- di- and trisaccharides could be separated on silica gel modified by the adsorption of piperazin and ethylene diamine from the eluent. The separation capacity of columns packed with silica gel with bonded NH₂ groups and with silica gel having diamines adsorbed on its surface is similar. The retention volumes of 15 carbohydrates were measured on columns containing silica gel with hydroxylated surface and on silica gel modified with piperazin from the eluent consisting of acetone-water. Comparison of acetone-water and acetonitrile-water as the eluent showed that the former is also suitable for the analysis of carbohydrates.     

Thin-layer chromatography (TLC) as pilot technique for HPLC. Utilization of retention database (R F) vs. eluent composition of pesticides

Summary TLC and HPLC are frequently unjustly regarded as competitive methods. Using the advantages of both methods, a combination of TLC and HPLC leads to a considerable saving of time and expense in analysis. Experimental data are presented aslog k (HPLC) vs.R _M (TLC) correlations; high correlation coefficients indicate that TLC using octadecyl silica, wettable with water (RP-18W) can be applied as a pilot technique for HPLC (RP-18).     

A Freeze Dried Kit for 99mTc(V) Dimercaptosuccinic Acid

^99mTc pentavalent dimercaptosuccinic acid [^99mTc(V) DMSA], a useful agent for imaging thyroid medullary carcinoma and other tumors can be reliably prepared by addition of Na^99mTcO₄ to a freeze-dried mixture of DMSA and Sn (2:1 molar ratio). The radiochemical purity, stability and animal bio-distribution behaviour is similar to that of the agent made by addition of NaHCO₃ to DMSA (III) renal imaging freeze-dried kit.