Stannous Chloride Reduction Research Articles

Glycol-Chitosan-Based Technetium-99m-Loaded Multifunctional Nanomicelles: Synthesis, Evaluation, and In Vivo Biodistribution.

We hereby propose the use of stable, biocompatible, and uniformly sized polymeric micelles as high-radiotracer-payload carriers at region-of-interest with negligible background activity due to no or low offsite radiolysis. We modified glycol chitosan (GC) polymer with varying levels of palmitoylation (P) and quaternization (Q). Quaternary ammonium palmitoyl glycol chitosan (GCPQ) with a Q:P ratio of 9:35 (Q9P35GC) offers >99% biocompatibility at 10 mg mL−1. Q9P35GC micelles exhibit >99% 99mTechnetium (99mTc) radiolabeling via the stannous chloride reduction method without heat. The 99mTc-Q9P35GC micelles (65 ± 3 nm) exhibit >98% 6 h serum stability at 37 °C and 7 day of radiochemical stability at 25 °C. HepG2 cells show a higher uptake of FITC-Q9P35GC than Q13P15GC and Q20P15GC. The in vivo 24 h organ cumulated activity (MBq h) order follows: liver (234.4) > kidneys (60.95) > GIT (0.73) > spleen (88.84). The liver to organ ratio remains higher than 2.4, rendering a better contrast in the liver. The radiotracer uptake decreases significantly in fibrotic vs. normal liver, whereas a blocking study with excess Q9P35GC significantly decreases the radiotracer uptake in a healthy vs. fibrotic liver. FITC-Q9P35GC shows in vivo hepato-specific uptake. Radiotracer liver uptake profile follows reversible binding kinetics with data fitting to two-tissue compartmental (2T), and graphical Ichise multilinear analysis (MA2) with lower AIC and higher R2 values, respectively. The study concludes that 99mTc-Q9P35GC can be a robust radiotracer for noninvasive hepatocyte function assessment and diagnosis of liver fibrosis. Furthermore, its multifunctional properties enable it to be a promising platform for nanotheranostic applications.

AWWA Water Science Author Spotlight

Having recently published an article in AWWA Water Science, Anthony Kennedy answered questions from the publication's editor-in-chief, Kenneth L. Mercer, about the research. Stannous Chloride Reduction–Filtration for Hexavalent and Total Chromium Removal From Groundwater Anthony Kennedy, Rachel Croft, Leah Flint, and Miguel Arias-Paic At the time of the research, I worked at the United States Bureau of Reclamation (USBR). I currently work at Corona Environmental Consulting, developing a research focus related to advanced water treatment processes and process optimization. Anthony enjoys backcountry skiing in Grand Teton National Park, March 2021. I've had two great mentors so far in my career: Professor Summers at CU Boulder and Dr. Miguel Arias-Paic at USBR. Professor Summers’ best advice was to focus on what is important and to not get caught up in minutia that can degrade your confidence. Dr. Arias-Paic said that for most problems we face in water treatment, a technological solution already exists; we just need to be more creative in how we apply those technologies. The primary motivations for the research were the cost and logistical challenges associated with brine generated from ion exchange treatment. Although ion exchange brine volume from regenerations can be significantly minimized, it still contains high levels of total dissolved solids and hexavalent chromium, in addition to other metals such as arsenic, vanadium, and uranium, and must ultimately face hazardous waste disposal. With stannous chloride, rapid-sand-filter backwash waste can also contain high levels of the less toxic trivalent chromium, but without the high total dissolved solids, making it more suitable for discharge to wastewater collection systems or sludge-drying ponds. In my personal life, I'm very conscious of my consumption and environmental impact. In my research, I try to simplify technologies and processes such that they use a more sustainable material or consume fewer materials, chemicals, etc., compared with conventional technologies, with the goal of meeting the same treatment target. Three challenges are (1) actual implementation of water treatment research; (2) widespread adoption and implementation of direct potable reuse to mitigate the effects of climate change on the drinking water industry; and (3) funding for drinking water, wastewater, and water reuse infrastructure. In July 2021, Anthony visited Parco Naturale Puez Odle in South Tyrol, Italy. I grew up near Pittsburgh, which has seen a comeback due in large part to a hardworking, motivated, but also modest and humble, populace. I take the same approach with my research—just sound, thorough research that can be used to improve the design, operation, and potentially the sustainability of water treatment facilities. To learn more about Anthony's research, visit the article, available online at https://doi.org/10.1002/aws2.1174.

Radiolabeling and Preliminary Evaluation of 99mTc-Labeled DNA Cube Nanoparticles as Potential Tracers for SPECT Imaging.

PurposeDNA nanostructures, with the advantages of structural designability and spatial addressability, have shown a great potential in the field of drug delivery and bio-medicine. Herein, we aimed to prepare technetium-99m radiolabeled DNA cube nanoparticles (99mTc-DCN) and expect to build a DCN-based drug carrier and nuclear medicine imaging platform.MethodsDCN could be readily assembled with 6 designed DNA oligonucleotides at an equal mole ratio in a single annealing procedure. 99mTc-MAG3-ssDNA (A20) was obtained by labeling MAG3-ssDNA (A20) with technetium-99m by using a stannous chloride reduction method. 99mTc-DCN was prepared by hybridize DCN with side chains (T20-DCN) with 99mTc-MAG3-ssDNA (A20). The biodistribution study and SPECT/CT imaging were conducted on KM mice.ResultsDCN was successfully assembled, and as-prepared DCN was characterized by native polyacrylamide gel electrophoresis, atomic force microscope and fluorescence resonance energy transfer. The size of DCN was about 5 nm. The radiolabeling yield of 99mTc-MAG3-ssDNA (A20) was approximately 90% by radio thin-layer chromatography. T20-DCN mixed with 99mTc-MAG3-ssDNA (A20) in PBS could generate 99mTc-DCN upon hybridization. The retention time (RT) of 99mTc-MAG3-ssDNA (A20) was at ~22 min, and the RT of as-prepared 99mTc-DCN was at ~12 min by radio-HPLC. The results from biodistribution study and SPECT/CT imaging showed that a significant proportion of DCNs were metabolized through the liver and kidney. Intestine exhibited a relatively indicative signal as well, which might be explained by the enterohepatic circulation of DCN via the liver and gallbladder.ConclusionWe have successfully prepared 99mTc-DCN as a SPECT/CT imaging probe via the side-chain hybridization strategy. The probe was metabolized mainly by the liver and excreted primarily to the bladder. Due to the superior properties of DNA cube nanoparticles, we believe DCN may potentially be translated into a preclinical setting for diagnosis and treatment of cancer-related diseases.

Improved extraction of acid-insoluble monosulfide minerals by stannous chloride reduction and its application to the separation of mono- and disulfide minerals in the presence of ferric iron

Metal sulfides, which are important indicators of sulfur cycling, are usually divided into two categories according to sulfur chemical valence: (1) monosulfides (S2−) and (2) disulfides (S22−). The two sulfur species are separated and quantified by a sequential-extraction method. Specifically, monosulfides are extracted as acid-volatile sulfide (AVS) using 6 M HCl prior to the extraction of disulfides using acidic CrCl2, which is defined as chromium-reducible sulfur (CRS). However, the conventional AVS procedure does not result in the quantitative extraction of S2− from the acid-insoluble metal monosulfide, copper sulfide (CuS). Consequently, residual sulfur in CuS (CuS-S) may be extracted as CRS resulting in the inaccurate separation of these two sulfur species. In this study, we used stannous chloride (SnCl2) to improve CuS-S recovery in the AVS procedure and permit the separate extraction of sulfur from CuS and pyrite (FeS2), the most abundant disulfide in nature. Our results show that the addition of SnCl2 increased the recovery of CuS-S as AVS from less than 36% to as high as 92% in the absence of pyrite and Fe3+ and 89% in the presence of pyrite and Fe3+. In addition, based on the observed correlation between the concentration of SnCl2 and the dissolution of FeS2, we identified the appropriate concentration of SnCl2 needed to avoid the dissolution of FeS2 in the AVS procedure. SnCl2 also minimized the oxidation of CuS-S by Fe3+ released from ferric minerals during the extraction of AVS. Based on the results of a series of sequential-extraction experiments, we show that an amendment of SnCl2 in the AVS procedure followed by CRS permits the quantitative separation of CuS-S and FeS2-S while also preventing interference by Fe3+. Our method will find application in research concerned with the fate of metals and the biogeochemistry of sulfur in the environment.

Rapid Screening Analysis of Methylmercury in Fish Samples Using Stannous Chloride Reduction and Direct Sampling Electrothermal Vaporization Atomic Absorption Spectrometry

Rapid Screening Analysis of Methylmercury in Fish Samples Using Stannous Chloride Reduction and Direct Sampling Electrothermal Vaporization Atomic Absorption Spectrometry

Stannous chloride reduction–filtration for hexavalent and total chromium removal from groundwater

AbstractHexavalent chromium (Cr(VI)) reduction using stannous chloride (SnCl2) has emerged as a possible alternative to chromium treatment technologies such as strong base anion exchange. In an effort to target not only Cr(VI) reduction but, ultimately, total chromium (Cr(T)) removal, SnCl2 addition followed by rapid sand filtration was tested at the pilot scale on a groundwater with a naturally occurring Cr(VI) concentration of 0.090 mg/L. A SnCl2 dose of 1.5 mg/L, followed by filtration, was able to consistently remove Cr(T) to less than 0.010 mg/L following an initial ripening period, with limited head loss for 10 sequential 17‐ to 25‐hr filter runs. Total tin and turbidity removal were similar, decreasing to below 0.050 mg/L and raw water levels, respectively. Analysis of filter sand following backwashes and three different material pipe segments that were exposed to unfiltered water dosed with SnCl2 indicated the accumulation of Cr and Sn on surfaces, which remains a concern.

Assessing redox properties of standard humic substances

Redox properties of humic substances (HS) control important biogeochemical processes. Thus, accurate estimation of redox properties of HS is essential. However, there is no general consensus regarding the best available measurement method of HS redox properties. In this study, we compared several common HS redox property measurement methods using anthraquinone-2,6-disulfonate (AQDS) as model compound, and standard Elliot soil humic acid (1S102H, ESHA), reference Pahokee peat (1R103H, PPHA), and Suwannee River natural organic matter (1R101N, SRNOM) as representative HS. We found that the H2/Pd reduction method followed by incubation with ferric citrate (FeCit) reagent was incomplete, and the H2/Pd reduction method followed by incubation with potassium ferricyanide (K3Fe(CN)6) was insensitive. Stannous chloride (SnCl2) reduction followed by titration of excess stannous (Sn2+) by potassium dichromate (K2Cr2O7) was found to be most accurate. These findings will help in future investigations on detailed characterizations of functional groups of HS responsible for oxidation/reduction reactions.

Synthesis of high quality reduced graphene oxide nanosheets free of paramagnetic metallic impurities

A facile and cost-effective method to prepare paramagnetic-metal free graphene nanosheets based on stannous chloride reduction of graphene oxide (GO) in a strongly acidic medium is reported. Simultaneous exfoliation and reduction is achieved in this room temperature process. Compared to the chemical reduction of GO using hydrazine or iron, the present method showed that Sn–rGO is several orders of magnitude less magnetic and hence does not contain any paramagnetic metallic impurities. With high reduction degree, this simple method shows promising application in energy and magnetic related studies.

Synthesis and characterization of a highly stable dendritic catechol-tripod bearing technetium-99m

The synthesis and preliminary biological tests (in vitro toxicity, in vitro stability) of new Tc(III)-radiolabelled dendro-chelates are presented. A dendritic 99mTc chelate 1 derived from a pre-organized tripodal tris-catecholamide exhibits a kinetic stability by far more important than its corresponding diethylenetriamine pentaacetic acid (DTPA) homologue 2. This permitted an assessment of the real impact of the pre-organized tripodal structure on kinetic inertness (and thus toxicity), an important issue to address when considering in vivo applications. Radiolabelling was performed using the stannous chloride reduction method; while DTPA-homologue 2 showed a high radiolabelling efficiency (96% radiolabelling yield after 30 min), tripodal complex 1 induced a 93% complexation yield after 45 min. In contrast, radiocomplex 1 derived from the most rigid and organized structure has a higher kinetic stability than 2. Indeed, while dissociation of 2 reached 50% after 1 h 30 min in physiological media like phosphate buffer saline (PBS) and bovine serum albumin (BSA), over 80% of 1 remained stable during the half-life of the radionucleide (6.02 h for 99mTc). Measurements of the cell leakage resulting from membrane damage of neuronal cells treated with increasing concentrations of dendritic ligand 16, together with pictures of treated neurons after staining, showed no detectable toxicity.

Synthesis and evaluation of a technetium-99m-labeled diethylenetriaminepentaacetate–deoxyglucose complex ([ 99mTc]–DTPA–DG) as a potential imaging modality for tumors

This study describes the radiolabeling and preliminary biologic testing of diethylenetriaminepentaacetic acid (DTPA)–deoxyglucose (DG) labeled with 99mTc. A one-step [ 99mTc]–DTPA–DG kit was prepared using the stannous chloride reduction method. When 99mTcO 4 − was added to the DTPA–DG kit at room temperature the radiochemical purity 30 min later was 99.2%, and it remained >98.6% for 6 h. Rapid blood clearance of [ 99mTc]–DTPA–DG was observed in in vivo biodistribution, the main route of clearance was via the kidneys. No significant accumulation in any other organs was seen. The tumor-to-brain and tumor-to-muscle concentration ratios for [ 99mTc]–DTPA–DG uptake were higher than those for fluorine-18-flurodeoxyglucose ( 18F–FDG). Scintigraphic results demonstrated the feasibility of [ 99mTc]–DTPA–DG imaging tumors. The [ 99mTc]–DTPA–DG complex is a potential imaging agent due to the ideal physical characteristics of the radionuclide, ease of preparation, low cost, early accumulation and the preference for the renal route of excretion.

Pyrazolyl–benzoxazole derivatives as protein kinase inhibitors. Design and validation of a combinatorial library

The malfunctioning of protein kinases is a hallmark of numerous diseases, for which a satisfactory therapy is missing. We describe the design and synthesis of a kinase targeted library based on a novel 2-(3-phenyl-1 H-pyrazol-4-yl)-1,3-benzoxazole scaffold. Ethyl 3-(3-nitrophenyl)pyrazole-4-carboxylate and its 4-nitro regioisomer were bound to trityl chloride resin, saponified with NaOH in MeOH, and amidated with a choice of two o-aminophenols. The resulting N-(2-hydroxyphenyl)amides were cyclized by Mitsunobu reaction to form four variants of the pyrazolyl–benzoxazole core template. Straightforward stannous chloride reduction of the nitro group on solid phase allowed subsequent scaffold derivatization via acylation or sulfonylation of the obtained amino function. Cleavage with TFA gave rise to the final compounds (36 examples).

Ring transformations of heterocyclic compounds. XXIII. The UV irradiation product of photochromic 2,4,6‐triaryl‐1‐(spiro[2H‐l‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridinium salts ‐ A phenolate betaine or a pyridinium substituted merocyanine dye?

AbstractThe synthesis of the novel 2,4,6‐triaryl‐1‐(spiro[2H‐1‐benzopyran‐2,2′‐indoline]‐6‐yl)pyridiniumper‐chlorates 4 by reaction of 5‐nitrosalicylaldehydes 6 with 1,3,3‐trimethyl‐2‐methyleneindoline (7) to 6‐nitro‐spiro[2H‐1‐benzopyran‐2,2′‐indolines] 1, their stannous chloride reduction to the 6‐amino derivatives 8, followed by a 2,6‐[C5+N] ring transformation with 2,4,6‐triarylpyrylium perchlorates 9, is reported. UV irradiation experiments in twenty solvents of different polarity prove their photochromic properties and show that the photochemically generated negative solvatochromic dyes 5, formed by ring opening of the benzopyran moiety of 4, are rather merocyanine than pyridinium phenolate betaine dyes.

Compounds of Hexavalent Uranium and Dibutylphosphate in Nitric Acid Systems

Storage tanks at the Savannah River Site (SRS) contain highly enriched uranium (U) and dibutyl phosphoric acid (HDBP), formed from the hydrolysis and radiolysis of tributylphosphate (TBP) in the PUREX process. Highly enriched dibutyl phosphoric acid, a relatively strong acid with a pKa (acid dissociation constant) of about one, forms insoluble compounds with U and other actinides in acid solutions. Accumulation of solids in these storage tanks presents a criticality hazard and must be avoided. In this work, U and HDBP compounds were formed from batch reactions in 0.2–6.0 M nitric acid (HNO3) and two HDBP concentrations, forming either a homogenous or heterogeneous solution based on solubility. A 4:1 HDBP:U ratio was used in all experiments. The chemical composition of the compounds was characterized using liquid scintillation, ion chromatography, and stannous chloride reduction. The physical characteristics of the U and HDBP compounds were characterized using a combination of infrared spectrometry (IR), electronic spectrophotometry (UV/Vis), and Phosphorous‐31 Nuclear Magnetic Resonance (31P NMR). The physical appearance of the solids ranged from a pale yellow powder at 0.2 M HNO3 loading to a bright yellow gel at 6.0 M HNO3, with constant modifications as the acid concentration increased. The U and HDBP precipitate from 0.2 M HNO3 was characterized as UO2(DBP)2 (a polymer with ten units) in homogenous U and HDBP solutions and UO2(DBP)2(HDBP) x (where x = 1 or 2) in heterogeneous U and HDBP solutions. Indications of nitrate complexation appeared in precipitates from 0.8 M HNO3 for both HDBP loadings, however a 1:1 uranium: nitrate ratio was not reached at that acid concentration. UO2(NO3)(H(DBP)2)(HDBP)2 precipitated from ≥ 3.0 M HNO3 with high HDBP concentrations. This compound was not formed until 6.0 M HNO3 was used in lower HDBP concentrations. It is assumed that the change in physical characteristics and addition of nitrate coincides with the breakdown of the UO2(DBP)2 polymer. Supporting data for these findings are presented and discussed.

New PET imaging agent for the serotonin transporter: [(18)F]ACF (2-[(2-amino-4-chloro-5-fluorophenyl)thio]-N,N-dimethyl-benzenmethanamine).

A new F-18-labeled phenylthiophenyl derivative specific for imaging of serotonin transporters (SERT) in the brain by positron emission tomography (PET) is described. Fluorinated phenylthiophenyl derivative, ACF, 2-[(2-amino-4-chloro-5-fluorophenyl)thio]-N,N-dimethyl-benzenmethanamine, was prepared by first coupling 2,5-dichloro-4-nitroaniline with 2-mercapto-N,N-dimethylbenzamide. The amino group of the coupled adduct was converted to a fluoro group through a Schiemann reaction. Subsequently, a one pot reduction of both nitro and amide groups by BH(3)-tetrahydrofuran yielded the nonradioactive ACF (yield 25%). In vitro binding assays using cell membrane homogenates of LLC cells expressing SERT, dopamine transporters (DAT), or norepinephrine transporters (NET) showed excellent binding affinity and selectivity for SERT (K(i) = 0.05, 3020, and 650 nM for SERT, DAT, and NET, respectively). For preparation of the [(18)F]ACF, the NH(2) group of the initially coupled adduct was converted to the trimethylammonium salt, which was replaced by [(18)F]fluoride in the presence of Kryptofix 222 and potassium carbonate. The final product, [(18)F]ACF, was obtained after a borane and stannous chloride reduction reaction. The combined two step reaction gave a radiochemical yield of 10-15% (EOB) and a radiochemical purity of >99%. Synthesis of the novel PET tracer, [(18)F]ACF, as a probe for binding to SERT in the brain was successfully achieved. The new tracer [(18)F]ACF showed excellent brain penetration and selective localization after an iv injection in rats (brain uptake at 2, 30, 60, 120, and 240 min was 3.27, 1.28, 0.69, 0.21, and 0.06% dose/organ, respectively). The hypothalamus/cerebellum ratio at 60 min post iv injection was 3.55. This specific localization in the hypothalamus was blocked by pretreatment of (+)McN5652. This novel ligand is a potential PET tracer for in vivo evaluation of SERT in the brain.

Spectrophotometric determination of phosphorus in iron alloys employing a flow injection system

A flow-injection procedure for spectrophotometric determination of phosphorus in electrolytic iron and iron alloys is proposed. The method is based on the ammonium molybdate reaction followed by stannous chloride reduction in acidic medium. In order to circumvent the severe interference caused by the major constituents such as Fe(III) and Cr(III), a mini-column packed with AG50W-X8 resin was coupled to the manifold. A sample throughput of 40 determinations per hour, a dynamical range from P 0.25 to 6.00 mg L-1, a reagent consumption of 25 mg ammonium molybdate and 2 mg stannous chloride per determination, and a relative standard deviation < 1% (n = 10) for a typical sample with 2.20 mg L-1 P were achieved. Three different types of samples were used to evaluate system performance. Accuracy was assessed by comparing the results with certified values and no significant difference at 95 % confidence level was observed.

ChemInform Abstract: Stereochemistry. Part 90. Stannous Chloride Reduction of Nitroalkenes in Amines. Synthesis and Cycloaddition of α-Dialkylaminoaldoxime.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stannous Chloride Reduction of Nitroalkenes in Amines. Synthesis and Cycloaddition of α-Dialkylaminoaldoxime

α-Dialkylamino aldoximes 12 were prepared by stannous chloride reduction of nitroalkenes in amines. An intramolecular Michael addition-deoxygenation mechanism is suggested. α-Allylamino aldoxime underwent an efficient Intramolecular Oxime Olefin Cycloaddition (IOOC) giving 13

Synthesis of [99mTc]DTPA-Folate and Its Evaluation as a Folate-Receptor-Targeted Radiopharmaceutical

A DTPA-folate conjugate was radiolabeled with (99m)Tc by stannous chloride reduction of [(99m)Tc]sodium pertechnetate in an aqueous solution of DTPA-folate. The radiochemical purity of the product consistently exceeded 97%, as assessed by thin-layer chromatography employing conditions analogous to those for radiochemical quality control of the radiopharmaceutical [(99m)Tc]DTPA. HPLC demonstrated that the radiolabeled product resulted from the intact DTPA-folate conjugate and not unconjugated DTPA. The ability of [(99m)Tc]DTPA-folate to target folate receptors in vivo was assessed in biodistribution studies with athymic mice bearing subcutaneous folate-receptor-positive human KB cell tumors. As an internal control, previously studied [(111)In]DTPA-folate was coinjected with the [(99m)Tc]DTPA-folate, along with varying amounts of DTPA-folate (0.38 mg/kg, 1.6 mg/kg, or 14 mg/kg). At each DTPA-folate dose, [(99m)Tc]DTPA-folate exhibited tumor uptake comparable to that of the coadministered [(111)In]DTPA-folate, with radiotracer levels declining at the higher DTPA-folate doses due to competitive receptor binding of the unlabeled conjugate. Tumor uptake of both tracers was also competitively blocked by preadministered folic acid dihydrate (2.9 mg/kg). Tumor-to-background tissue contrast obtained with [(99m)Tc]DTPA-folate was generally similar to that obtained with [(111)In]DTPA-folate. The (99m)Tc-labeled DTPA-folate conjugate may have utility as a targeted radiopharmaceutical for imaging neoplastic tissues known to overexpress the folate receptor.

Evaluation of 99mTc labelled poly lactic acid microspheres for diagnostic radioembolization

Radioembolization is used in diagnostic imaging of the lungs and for radioembolization therapy of hepatic tumours. Presently, 99mTc labelled macroaggregates or microspheres of human serum albumin (HAM) are used for this purpose. Poly lactic acid (PLA) is biodegradable, like HAM, and, unlike HAM, is not a blood product. The aim of the present study was to evaluate the uptake and biodegradation of PLA microspheres in lungs. PLA (MW=48720Da) microspheres of 1.0-100mum (mean=39.5mum) in diameter were prepared by solvent evaporation frommethylene chloride. They were labelled with 99mTcby stannous chloride reduction at pH3, with an efficiency of 98%and a stability of 96%at 24h. For biodistribution studies, 15 mice were i.v. injected with 20muCi 99mTc-PLA microspheres in 0.1ml and sacrified at 15min, 1, 3, 6 and 24h (three at each time point). All the organs were removed, weighed and counted against a standard prepared from 1/100 dilution of the injected radioactivity. Some mice were similarly injected and sacrified at 30min, 15 and 30 days. The lungs were removed and frozen, and 10mum sections were obtained, stained with haemotoxylin and eosin and examined under a light microscope. Five rabbits were i.v. injected with 1mCi of 99mTc-PLA microspheres. Scintigrams were obtained at various intervals up to 24h. In mice, the lung uptake was significant at 30min-1h post-injection. In rabbits, the lungs were the only organs visualized up to 24h. Microscopic examination of tissue sections demonstrated slow biodegradation of PLA particles. In conclusion; (1) The high lung uptake obtained in mice and rabbits indicates the suitability of PLA microspheres for lung imaging, and (2) although the slow biodegradation rate might be a disadvantage in patients with lung disorders in diagnostic studies, it may be an advantage in therapeutic applications with radionuclides which have long physical half lives.

Determination of orthophosphate in highly saline waters

Standard methods for the determination of phosphorus as phosphate ion are now well established for fresh and marine waters. In highly saline waters, however, salt effects due to ionic strength, or to particular ions present, may result in method interferences. Three methods of analysis of phosphate based on the formation of phosphomolybdenum blue complexes have been evaluated here for hypersaline waters. Stannous chloride reduction in aqueous media exhibits a substantial salt effect and its use is not recommended. Stannous chloride reduction following extraction into non aqueous solvents shows a significant salt effect (up to 30 per cent) in solutions of salinity >100 g L−1. Dilution of hypersaline waters to below this salinity may overcome the salt effect but the method suffers from other disadvantages involving resource constraints and health and safety considerations. Ascorbic acid reduction, catalysed by antimony (III) ions, appears to offer the most promise for hypersaline waters. Turbidity in samples having high salinity (> 100 g L−1) and high phosphorus concentrations (> 500 μg P L−1) changes the spectral characteristics of solutions but linear calibration curves still result for concentrations in the range 400 to 1,000 μg P L−1. The occurrence of turbidity is also affected by the ionic composition of hypersaline waters since solutions made from sea salt give different results to those made from sodium chloride. Dilution of samples, to give salinities less than 100 g L−1 prior to reduction is recommended to avoid turbidity. The salt effect in these lower salinity waters is less than 3 per cent up to 100 g L−1.