Improvements in habitability and housing satisfaction after dwelling regeneration in social housing complexes. The RUCAS study.

Housing is a pressing problem worldwide and a key determinant of health and wellbeing. The right to adequate housing, as a pillar of the right to an adequate standard of living, means more than a roof to live under. Adequate means the dwelling must fulfill material functions and psychosocial functions, thus contributing to dwellers health and wellbeing. Social housing policies aim to fulfill the right to housing, but frequently fail in fulfilling the right to it being adequate. This study capitalizes on the implementation of a national urban regeneration program in two social housing villas in central Chile (one in Santiago, in the central valley, the other in Viña del Mar, a coastal city) to run a natural experiment assessing the impact of dwelling renovation on several dimensions of perceived habitability and housing satisfaction among the -mostly female-household homemakers. We use 5 waves of survey data collected with a step-wedge design to estimate the association between a time-varying exposure status (the intervention) and 7 binary outcomes for habitability and 5 for housing dissatisfaction, including overall housing satisfaction. We use Poisson regression models with robust variance and a random intercept at the respondent level. At baseline, reports of poor habitability and dissatisfaction across all features were markedly high, the highest levels of dissatisfaction being with acoustic insulation and dwelling size in both villas, and with indoor temperature in Santiago. The intervention resulted in statistically significant and markedly large improvements in reported habitability and dissatisfaction relative to those housing components targeted by the intervention, as well as with overall dwelling satisfaction in both study cases. Implications are, first, that the policy response to quantitative housing deficits must not overlook housing quality; second, that housing renovation appears as a promising intervention for qualitative housing crises; third, that while improvements in habitability and satisfaction are specific to the interventions in place, overall housing satisfaction can improve in more limited, tailored, dwelling renovation interventions. Social housing renovation in Latin America appears as a promising intervention to improve quality of life among the urban poor dwellers and reduce inequalities in health related to housing conditions.

FRP Confinement of Stone Samples after Real Fire Exposure.

The mechanical properties of stone materials can be severely affected by exposure to high temperatures. The effect of fire on stone buildings could cause irreversible damage and make it necessary to retrofit the affected elements. Particularly, the strengthening of columns by confinement with composites has been widely improved during the last decades. Today, fiber reinforced polymer (FRP) confinement represents a very interesting alternative to traditional steel solutions. This work studied the behavior of cylindrical stone specimens subjected to real fire action and confined by means of CFRP or GFRP jackets, with the aim of assessing the effectiveness of these reinforcement systems applied to a material that has previously been seriously damaged by high temperature exposure. In general, the strengthened samples showed notable increases in strength and ductility. The response seemed to depend basically on the FRP properties and not on the degree of damage that the stone core may have suffered. Finally, the results obtained experimentally were compared with the confinement models proposed by the available design guides, in order to evaluate the accuracy that these models can offer under the different situations addressed in this research.

The Effect of Different Oxygen Surface Functionalization of Carbon Nanotubes on the Electrical Resistivity and Strain Sensing Function of Cement Pastes.

Different studies in the literature indicate the effectiveness of CNTs as reinforcing materials in cement-matrix composites due to their high mechanical strength. Nevertheless, their incorporation into cement presents some difficulties due to their tendency to agglomerate, yielding a non-homogeneous dispersion in the paste mix that results in a poor cement-CNTs interaction. This makes the surface modification of the CNTs by introducing functional groups on the surface necessary. In this study, three different treatments for incorporating polar oxygen functional groups onto the surface of carbon nanotubes have been carried out, with the objective of evaluating the influence of the type and oxidation degree on the mechanical and electrical properties and in strain-sensing function of cement pastes containing CNTs. One treatment is in liquid phase (surface oxidation with HNO3/H2SO4), the second is in gas phase (O3 treatment at 25 and 160 °C), and a third is a combination of gas-phase O3 treatment plus NaOH liquid phase. The electrical conductivity of cement pastes increased with O3- and O3-NaOH-treated CNTs with respect to non-treated ones. Furthermore, the oxygen functionalization treatments clearly improve the strain sensing performance of the CNT-cement pastes, particularly in terms of the accuracy of the linear correlation between the resistance and the stress, as well as the increase in the gage factor from 28 to 65. Additionally, the incorporation of either non-functionalized or functionalized CNTs did not produce any significant modification of the mechanical properties of CNTs. Therefore, the functionalization of CNTs favours the de-agglomeration of CNTs in the cement matrix and consequently, the electrical conductivity, without affecting the mechanical behaviour.

Study on Retrofitted Masonry Elements under Shear Using Digital Image Correlation.

Architectural heritage is usually built with masonry structures, which present problems under lateral in-plane loading conditions, such as wind pressure or earthquakes. In order to improve the shear behavior of masonry, the use of a fabric-reinforced cementitious matrix (FRCM) has become an interesting solution because of its synergy of mechanical properties and compatibility with masonry substrates. For a proper structural evaluation, the mechanical behavior of reinforced masonry and the FRCM itself needs to be characterized. Hence, a numerical model to evaluate the FRCM reinforcement requires some mechanical parameters that may be difficult to obtain. In this sense, the shear behavior of masonry can be evaluated by means of diagonal tension tests on small specimens (71 × 71 cm). In this work, a digital image correlation (DIC) monitoring system was used to control displacements and cracking patterns of masonry specimens under shear stress (induced by diagonal tension with FRCM layers) applied to one or two sides. In addition, the mechanical behavior of FRCM coupons under uniaxial tensile tests was also registered with DIC. The displacement measurements obtained by DIC were validated with the measurements registered with LVDT. Unlike LVDT-based techniques, DIC monitoring allowed us to measure deformations in masonry during the full test, detecting crack initiation even before it was visible to the eye.

Residual Compressive Strength of Recycled Aggregate Concretes after High Temperature Exposure.

Sustainability requirements are gaining importance in the construction industry, which needs to take specific measures in the design and construction of concrete structures. The use of recycled aggregates in concrete may be of special interest. Recycling a construction waste will close the life cycle of the original materials (e.g., concrete). Thus, environmental benefits would come from the lower waste generation, and from a lower necessity of raw materials for new structures. The current Spanish code for structural concrete considers the use of recycled aggregates in replacement rates up to 20% by aggregate mass, assimilating their properties with those of concretes without aggregate replacement. Higher substitution percentages would require further testing. In this work, substitution of coarse aggregate for recycled aggregates (with replacement percentages of 25%, 50% and 100%) has been studied, and the concrete's residual properties after exposure to high temperatures (between 350 °C and 850 °C) have been assessed. Compressive strength and capillary water absorption tests were made after heating, and the experiments showed higher residual strength in concretes with the greatest content of recycled aggregates. However, a statistical analysis made with additional data available in the literature seemed to predict otherwise, and the recycled aggregate replacement would have a negative effect on the residual strength.

Efectividad de las técnicas de movilización articular sobre el rango de movimiento de pacientes adultos con capsulitis adhesiva primaria de hombro: revisión sistemática y metanálisis / The effectiveness of joint mobilization techniques for range of motion in adult patients with primary adhesive capsulitis of the shoulder: a systematic review and meta-analysis

Resumen OBJETIVO: Determinar la efectividad de las técnicas de movilización articular en el rango de movimiento en pacientes adultos con capsulitis adhesiva primaria de hombro. MÉTODO: Revisión sistemática con metanálisis. La búsqueda fue realizada en las bases de datos MEDLINE/PubMed, PEDro, CENTRAL, LILACS, EMBASE, CINAHL, Scopus y Web of Science. Los criterios de elegibilidad fueron estudios que utilizaran una técnica de movilización articular oscilatoria y/o mantenida aplicada, sola o adicionada, a un programa de tratamiento en pacientes con capsulitis adhesiva primaria, en cualquier estadio. La selección de estudios y la extracción de datos fueron realizadas por dos autores de forma independiente. El riesgo de sesgo se evaluó según la herramienta propuesta por Cochrane. RESULTADOS: Se incluyeron 14 estudios con variados riesgos de sesgo. La movilización posterior versus otra técnica articular no presenta diferencia de media significativa (- 0,95 grados; intervalo de confianza de 95%; - 5,93 a 4,02), mientras que comparada con un grupo control la diferencia es de 26,80 grados (intervalo de confianza 95%; 22,71 a 30,89), además cuando se aplica un conjunto de técnicas articulares versus un grupo control, para la abducción la diferencia es de 20,14 grados (intervalo de confianza 95%; 10,22 a 30,05). En ambos casos, los resultados son estadísticamente significativos y se aprecia un tamaño de efecto moderado. CONCLUSIONES: La evidencia científica no es concluyente acerca de la efectividad de la movilización articular, dada la heterogeneidad en la metodología y sesgo de los artículos incluidos en esta revisión. Al compararla con tratamientos que no incluyen terapia manual, parecieran favorecer la mejoría del rango de movimiento y reducción del dolor, en pacientes con capsulitis adhesiva primaria de hombro.

Abstract OBJECTIVE: To determine the effectiveness of joint mobilization techniques in the range of motion in adult patients with primary adhesive shoulder capsulitis. METHODS: Systematic review with meta-analysis. The search was performed in the MEDLINE/PubMed, PEDro, CENTRAL, LILACS, EMBASE, CINAHL, Scopus and Web of Science databases. The eligibility criteria were studies that used an oscillatory and/or maintained joint mobilization technique applied alone or added-on to a treatment program in patients with primary adhesive capsulitis at any stage. Two authors carried out the selection of studies and the extraction of data, independently. Risk of bias was evaluated according to the tool proposed by Cochrane. RESULTS: We included 14 studies with variable risk of bias. Posterior mobilization compared to any other technique was not significantly different (0.95 degrees; 95% CI: - 5.93 to 4.02), whereas compared to a control group, the difference is 26.80 degrees (CI 95%: 22.71 to 30.89). When applying a set of joint techniques versus a control group, for abduction the difference is 20.14 degrees (95% CI: 10.22 to 30.05). In both cases, the results are statistically significant, and the effect size is moderate. CONCLUSIONS: The evidence is not conclusive about the effectiveness of joint mobilization. When compared with treatments that do not include manual therapy, joint mobilization seems to have a favorable effect on the range of motion and pain reduction in patients with primary adhesive shoulder capsulitis.

Carbon Nanofiber Cement Sensors to Detect Strain and Damage of Concrete Specimens Under Compression.

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material's strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Rapid immunochemical analysis of the sulfonamide-sugar conjugated fraction of antibiotic contaminated honey samples.

A rapid high-throughput immunochemical screening (HtiS) procedure for the analysis of the sulfonamide (SA)-sugar conjugated fraction of antibiotic contaminated honey samples has been developed. Studies performed with this matrix have indicated that sulfonamide antibiotics are conjugated to sugars rapidly and quantitatively, providing samples with very low SA immunoreactivity. Therefore, sulfonamides must be first released before the analysis, and for this purpose, a simple and fast sample preparation procedure has been established consisting of hydrolyzing the sample for 5 min, adjusting the pH and buffering the sample prior to the immunochemical analysis. Under these conditions, honey samples could be directly analyzed without any additional sample treatment, other than dilution. Recovery values of the whole analytical procedure were greater than 85%. The analysis of the same samples without the hydrolysis provided recovery values below 5%. Selectivity studies performed in hydrolyzed honey samples revealed that nine relevant sulfonamide antibiotics can be detected with limit of detection (LOD) values below the action limits established by some EU countries (Belgium, 20 µg kg(-1), United Kingdom or Switzerland, 50 µg kg(-1)).

A portable electrochemical magnetoimmunosensor for detection of sulfonamide antimicrobials in honey.

A new electrochemical magnetoimmunosensor (EMIS) has been developed for the screening of residues of sulfonamide antimicrobials in honey samples. The immunosensor is able to detect up to ten different sulfonamide congeners at levels below the action points established in some European countries (25 µg kg(-1)) after a hydrolysis step in which the sulfonamides are released from the corresponding conjugates formed in samples of this type. In spite of the complexity of the sample after the hydrolysis procedure, the EMIS could perform quantitative measurements, directly in these samples, without any additional sample cleanup or extraction step. For example, sulfapyridine, used as a reference, can be detected in hydrolyzed honey with a limit of detection (IC90) of 0.1 ± 0.03 µg kg(-1). Considering that the use of antibiotics for bee treatment is prohibited in the European Union, the immunosensor presented here could be an excellent screening tool. Moreover, several samples can be processed in parallel, which facilitates the analysis, reducing the necessity to use more costly confirmatory methods for just screening. As a proof of concept, a set of blind honey samples (spiked and incurred) were analyzed and the results were compared with those obtained by high-performance liquid chromatography-tandem mass spectrometry, demonstrating the potential of the EMIS as a screening tool.

Tumores de colon de expansión lateral: características en nuestra población / Laterally spreading tumors: characteristics in our population

Introduction: Colorectal cancer is a rising disease worldwide. In Chile, it is the third leading cause of death associated to gastrointestinal cancer. Optimal preventive management requires surveillance of precursor lesions or early-stage tumors. Laterally spreading tumors (LST) are categorized as nonpolypoid colorectal neoplasms. Since there are no demographic data on these lesions in our country, the aim of our study was to describe the characteristics of LSTs based on our department’s data. Methods: We reviewed the department’s colonoscopy database from 1996 to 2006 to obtain clinical, endoscopic and histological data. We excluded patients with family history of polyposis, prior colorectal cancer and inflammatory bowel disease. Results: Out of 3713 colonoscopies performed, 364 (9.8 percent) adenoma cases were detected; 42 (1.2 percent) of them were catalogued as LSTs. Thirty-three LST patients had complete data and were included in the study. The gender proportion was similar between male and female. Ages ranged from 35 and 92 years (mean +/- SD 66.7 +/- 13.7). The tumor size ranged from 10 to 120 mm (mean +/- SD 28.2 +/- 28.3). According to distribution along the large bowel, 19 (57.5 percent) LSTs were located distally and 14 (42.5 percent) were proximal to the splenic flexure. Histology showed 26 adenomas (14 of them with high-grade dysplasia), 5 adenocarcinomas and 2 hyperplastic lesions. Conclusion: In Chile, LSTs are mainly found in the elderly. It is important to detect these lesions because most of them contain cancer or high-grade dysplasia. Therefore, during colonoscopy, we should focus not only on polypoid lesions, but also on flat lesions.

Introducción: El cáncer colorrectal es una enfermedad emergente a nivel mundial. En nuestro país es la tercera causa de muerte por cáncer del tubo digestivo. Un óptimo manejo preventivo implica la detección y tratamiento de las lesiones precursoras y los cánceres incipientes. Los tumores de expansión lateral (Laterally spreading tumors-LST) se consideran lesiones precursoras no polipoídeas. En Chile no existen datos demográficos de estas lesiones, por lo que el objetivo de este estudio es caracterizar los LST en nuestra población. Métodos: Revisamos la base de datos de las colonoscopias realizadas en nuestro Instituto desde 1996 al 2006, obteniendo datos clínicos y las características endoscópicas e histológicas. Excluimos los pacientes con historia de poliposis familiar, cáncer colorrectal y enfermedad inflamatoria intestinal. Resultados: De 3.713 colonoscopias, se detectaron 364 (9,8 por ciento) casos diagnosticados como adenoma, lesiones planas o LST, de los cuales 42 (1,2 por ciento) se catalogaron como LST. Sólo 33 pacientes con LST tenían disponible el estudio histológico. La proporción por género fue similar entre hombres (17) y mujeres (16). El rango de edad se distribuyó entre 35 y 92 años (promedio +/- DE 66,7 +/- 13,7); el tamaño tumoral fue de 10 a 120 mm (promedio +/- DE 28,2 +/- 28,3). De acuerdo a la distribución en el colon y recto, 19 (57,5 por ciento) LST se localizaron distales al ángulo esplénico y 14 (42,5 por ciento) proximales. El estudio histológico demostró 26 adenomas, 14 de los cuales presentaban displasia de alto grado, 5 adenocarcinomas y 2 lesiones hiperplásicas. Conclusión: En nuestra población los LST se presentan mayoritariamente en la tercera edad. Es importante la detección de estas lesiones, dado que en su mayoría contienen un cáncer o son adenomas con displasia de alto grado. Durante la colonoscopia no solamente debemos enfocarnos en los pólipos sino también en las lesiones planas.

[System of dynamic neutralization in the lumbar spine: experience on 94 cases]. / Sistema de neutralización dinámica en la coluna lumbar. SISTEMA DYNESYS. Experiencia en 94 casos

OBJECTIVE: To assess the results obtained using the Dynesys system (Dynamic Neutralisation System for the spine), in a group of 94 patients. This new system for treating lumbar degenerative pathologies is based on lumbar stabilisation and preservation of articular function, as opposed to traditional arthrodesis restrictions. MATERIAL AND METHODS: We analyze series of 94 patients in whom this system was used. 62 were males and 32 females with an average age of 46.4 years. The pathologies treated were disc herniation in 27 cases, degenerative discopathy in 54 cases and lumbar channel stenosis in 13 cases. Follow-up was carried out between 14 and 24 months, assessing the clinical picture according to the Oswestry scale and the return to work. RESULTS: The final results on the Oswestry scale were 21.4% with respect to 56.8% prior to the treatment and the return to work was 82%. There was a remission of the sciatica symptoms in almost all the cases, as well as of the lumbar pain, and there was a 60% improvement in the claudication cases. With regard to complications, we would like to point out two cases due to the technique, one because of the wrong positioning of the screws and the other due to the rupture of the pedicle. There were two cases of subcutaneous seroma and two late subclinical infections. CONCLUSIONS: The dynamic neutralisation obtained using this system, should not be considered as an arthrodesis. Treatment using Dynesys enlarges the population of patients candidates for surgery to who initially do not apparently need a standard fixation, but who raise doubt regarding the application of techniques without instrumental support, incorporating the functionality concept as opposed to restricting movement. This system can be defined as a disc prosthesis fitted externally to the disc. We have obtained good results in the majority of our patients, although we believe that the follow-up should be increased.

Cysteinyl-flavan-3-ol conjugates from grape procyanidins. Antioxidant and antiproliferative properties.

New bio-based antioxidant compounds have been obtained by depolymerisation of grape polymeric flavanols in the presence of cysteine. Their preparation and purification, as well as their antiradical/antioxidant and antiproliferative properties are reported. 4beta-(S-cysteinyl)epicatechin 5, 4beta-(S-cysteinyl)catechin 6 and 4beta-(S-cysteinyl)epicatechin 3-O-gallate 7 were efficiently purified from the crude depolymerised mixture by cation-exchange chromatography and preparative reversed-phase chromatography. The new compounds were more efficient than the underivatised (-)-epicatechin 1 as scavengers of the 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) and weak growth inhibitors of human colon carcinoma HT29 cells. The order of antiradical and antiproliferative efficiency was 7 >5 approximately 6 >1, the same for both assays.

Development of an immunochemical technique for the analysis of trichlorophenols using theoretical models.

An immunoassay has been developed for trichlorophenol analysis on the basis of theoretical chemistry modeling studies. These data have allowed us to choose the optimum chemical structure of the immunizing hapten according to realistic similarities with the target analyte. The synthesis of this hapten and the subsequent application of an appropriate immunization protocol have lead to the production of polyclonal antibodies against the target analyte. A homologous direct competitive ELISA has been developed that can be carried out in about 1 h. It has a limit of detection of 0.2 +/- 0.06 microg/L (1.01 +/- 0.3 nM) and it has been proven to tolerate a wide range of ionic strengths and pH values. Thus, the assay has acceptable features in samples with ionic strength between 4 and 56 mS/cm and pH values between 5.5 and 9.5. Studies on the selectivity of this immunoassay have demonstrated a high recognition of the corresponding brominated analogues. Other phenolic compounds do not interfere significantly in the analysis of 2,4,6-trichorophenol using this immunochemical technique. The accuracy of the assay has been evaluated using certified and spiked samples.

Identification of selective inhibitors of acetylcholinesterase from a combinatorial library of 2,5-piperazinediones.

The potentiation of central cholinergic activity has been proposed as a therapeutic approach for improving cognitive function in patients with Alzheimer's disease. Increasing the acetylcholine concentration in brain by modulating acetylcholinesterase (AChE) activity is among the most promising strategies. We have used a combinatorial approach to identify different 2,5-piperazinediones (DKP) with AChE inhibitory activity. Our goal was to find inhibitors exhibiting high AChE/BuChE (butyrylcholinesterase) selectivity, in order to reduce the undesirable side effects elicited by most of the inhibitors that have been developed to date. Screening of a DKP library constructed on solid-phase using the multiple parallel synthesis format, resulted in the identification of several compounds with moderate efficacy on AChE. In particular, DKP-80 had an IC50 = 2.2 microM with no significant inhibitory activity on BuChE. Moreover, estimated values of Clog P and log BB for the most active compounds fulfilled the bioavailability requirements for enzyme inhibitors acting on the central nervous system. In order to understand the inhibitory properties of the ligand at the molecular level, molecular dynamics simulations were computed on DKP-80 complexed to AChE, and the most relevant binding interactions of this inhibitor to the active center of the enzyme were characterized. Overall the present results indicate that the DKP-based compounds identified are novel AChE inhibitors which may be considered likely lead compounds for further development of drug candidates against Alzheimer's disease.

[Infravesical obstructive uropathy secondary to extreme vulval atrophy]. / Uropatía obstructiva infravesical secundaria a atrofia vulvar extrema.

Lower urinary tract obstruction in women is an uncommon condition resulting from multiple either organic or functional disorders. This paper contributes one case of obstructive uropathy secondary to presence of almost complete vulvar synechia due to extreme genital atrophy, a rare entity that may appear in postmenopausal women. Partial and incomplete vulvar fusion usually occurs in significant postmenopausal atrophies, sometimes associated to urethral meatus stricture; this, however, has no significant repercussion on urination dynamics. No other comparable case was found in the reviewed literature.

Influence of the hapten design on the development of a competitive ELISA for the determination of the antifouling agent Irgarol 1051 at trace levels.

Enzyme-linked immunosorbent assays (ELISAs) with a high detectability have been developed for determination of the antifouling agent Irgarol 1051. The features of the resulting assays have been rationalized by using molecular mechanic calculations (MM2+) to correlate the chemical structure of different immunizing haptens and the corresponding avidities of the obtained antisera. The ability of Irgarol 1051 to compete for the antibody binding sites with 11 horseradish peroxidase enzyme tracers, differing in the chemical structures of the hapten, has been investigated. The present paper demonstrates that high-quality antibodies and, therefore, immunoassays reaching very low detection limits could be predicted by molecular modeling studies of the analyte conformations and of the immunizing haptens' geometries, hydrogen-bonding capabilities, and electronic distributions. Two of the ELISAs obtained have been optimized to obtain reproducible immunoassays. The dynamic ranges of both assays are between 30 and 200 ng/L, and the limits of detection are approximately 16 ng/L. The reported immunoassays have been evaluated and validated by analyzing spiked and real seawater samples. Irgarol 1051 has been found to be present in two of the geographical locations analyzed at concentration levels dependent on the time of year. The analytical results obtained with these immunoassays have been validated by chromatographic methods.

Mitomycin C binding to poly[d(G-m5C)].

Poly[d(G-m5C)] was modified by reductively activated mitomycin C, an anti-tumour drug, under buffer conditions which are known to favour either the B or the Z conformations of DNA. C.d. and 31P-n.m.r. were used to characterize the poly[d(G-m5C)]-mitomycin cross-linked complexes, as well as the effects on the equilibrium between the B and Z forms of the polynucleotide. Mitomycin C appears to inhibit the B-->Z transition, even in the presence of 3 mM MgCl2, while the Z-form of poly[d(G-m5C)] does not interact significantly with the drug under bifunctionally activating conditions; thus no reversion from the Z-form to the B-form of the polynucleotide can be observed under the salt conditions which are required for the Z-form to exist.

On the origin of some controversial ions (m/z 59, 60, 77, and 119) in the thermospray reagent plasma from ammonium acetate.

The origin of ions at m/z 60, 77, and 119 in the thermospray (TSP) reagent plasma is reconsidered. It is demonstrated that these major ions in the TSP spectrum of ammonium acetate are not due to dehydration processes in the gas or liquid phase, as is generally accepted, but to the preexistence of acetamide as an impurity in the commercial salts. Acetamide, characterized by TSP/tandem mass spectrometry, gas chromatography-electron impact ionization mass spectrometry, (1)H-NMR, and (13)C-NMR, is responsible for the [M +60](+) and [M + 77](+) adducts observed in some spectra. The buffer ion at m/z 59 is also due to impurities in the ammonium acetate salts. Washing the solid salt with chloroform eliminates most of these impurities. Examples using the pesticides linuron, monuron, and carbaryl show that the ions observed at m/z Mr + 60 and Mr + 59 disappear when a buffer obtained from acetic acid and ammonia is used instead of the commercial salts.