Blank Solvent Research Articles

One-step synthesis of SO42−/ZrO2‑SEP solid-acid catalyst for energy-efficient CO2 capture

One-step synthesis of SO42−/ZrO2‑SEP solid-acid catalyst for energy-efficient CO2 capture

High Purity Solvents for qNMR Measurement

Quantitative NMR (qNMR) has been adopted by documentary standards, including the Japanese Pharmacopoeia (JP), United States Pharmacopoeia (USP), and International Organization for Standardization (ISO), owing to its reliability and efficiency. Note that qNMR can be used for quantifying target components using the signal integration ratio of an analyte to a reference. In qNMR, a modern NMR instrument with high resolution and sensitivity is used to record reliable spectra. This instrument can detect small signals from impurities in a solvent, which may result in inaccurate signal integration in the spectrum. In this study, we investigated the influence of solvent quality on qNMR accuracy focusing on organic impurities, water content, and deuteration ratio. If signals from organic impurities and signals from the analyte overlap, the duplication of signal integration will directly affect the qNMR analytical result. To examine overlapping, we performed blank solvent tests. Additionally, a high water content and low deuteration ratio affect the detection sensitivity, thus reducing the signal-to-noise (S/N) ratio of the target. Thus, these factors must be considered to obtain accurate qNMR results.

A GC-MS-based untargeted metabolomics approach for comprehensive metabolic profiling of mycophenolate mofetil-induced toxicity in mice.

Background: Mycophenolate mofetil (MMF), the morpholinoethyl ester of mycophenolic acid, is widely used for maintenance immunosuppression in transplantation. The gastrointestinal toxicity of MMF has been widely uncovered. However, the comprehensive metabolic analysis of MMF-induced toxicity is lacking. This study is aimed to ascertain the metabolic changes after MMF administration in mice. Methods: A total of 700mg MMF was dissolved in 7mL dimethyl sulfoxide (DMSO), and then 0.5mL of mixture was diluted with 4.5mL of saline (100mg/kg). Mice in the treatment group (n = 9) were given MMF (0.1mL/10g) each day via intraperitoneal injection lasting for 2weeks, while those in the control group (n = 9) received the same amount of blank solvent (DMSO: saline = 1:9). Gas chromatography-mass spectrometry was utilized to identify the metabolic profiling in serum samples and multiple organ tissues of mice. The potential metabolites were identified using orthogonal partial least squares discrimination analysis. Meanwhile, we used the MetaboAnalyst 5.0 (http://www.metaboanalyst.ca) and Kyoto Encyclopedia of Genes and Genomes database (http://www.kegg.jp) to depict the metabolic pathways. The percentages of lymphocytes in spleens were assessed by multiparameter flow cytometry analysis. Results: Compared to the control group, we observed that MMF treatment induced differential expression of metabolites in the intestine, hippocampus, lung, liver, kidney, heart, serum, and cortex tissues. Subsequently, we demonstrated that multiple amino acids metabolism and fatty acids biosynthesis were disrupted following MMF treatment. Additionally, MMF challenge dramatically increased CD4+ T cell percentages but had no significant influences on other types of lymphocytes. Conclusion: MMF can affect the metabolism in various organs and serum in mice. These data may provide preliminary judgement for MMF-induced toxicity and understand the metabolic mechanism of MMF more comprehensively.

Investigating the Impact of SN-38 on Mouse Brain Metabolism Based on Metabolomics.

SN-38 (7-ethyl-10-hydroxycamptothecin), the active metabolite of irinotecan, has been extensively studied in drug delivery systems. However, its impact on neural metabolism remains unclear. This study aims to investigate the toxic effects of SN-38 on mouse brain metabolism. Male mice were divided into an SN-38 group and a control group. The SN-38 group received SN-38 (20 mg/kg/day) via intraperitoneal injection, while the control group was given an equal volume of a blank solvent mixture (DMSO and saline, ratio 1:9). Gas chromatography-mass spectrometry (GC-MS) was employed to analyze differential metabolites in the cortical and hippocampal regions of the SN-38-treated mice. SN-38 induced metabolic disturbances in the central nervous system. Eighteen differential metabolites were identified in the hippocampus and twenty-four in the cortex, with six common to both regions. KEGG pathway enrichment analysis revealed statistically significant alterations in six metabolic pathways in the hippocampus and ten in the cortex (P<0.05). This study is the first to demonstrate the neurotoxicity of SN-38 in male mice through metabolomics. Differential metabolites in the hippocampal and cortical regions were closely linked to purine metabolism, pyrimidine metabolism, amino acid metabolism, and glyceride metabolism, indicating disruptions in the blood-brain barrier, energy metabolism, and central signaling pathways.

The immunosuppression effects of deforolimus (ridaforolimus, AP23573) on allograft organ transplantation

AbstractObjectsWe conducted this study to confirm the immunosuppression effect of Deforolimus in heart allotransplantation and find its mechanism.Material and methodsWe used vitro methods to confirm the immunosuppression of Deforolimus in T cell subgroups. Then, we conducted heart allotransplantation from BALB/c donors to C57BL/6 recipients with the oral administration of Deforolimus or blank solvent to contrast the immunosuppression effect in vivo. We used the flow cytometry（）, clone anergy test, ELISA (enzyme‐linked immunosorbent assay), apoptosis test, and lymphocyte translation (LT) to find the mechanism of Deforolimus’ immunosuppressive action.ResultsStudies in vitro demonstrated that Deforolimus had immunosuppressive action. Studies in vivo demonstrated that Deforolimus could inhibit the immune system of the heart allotransplantation recipients to extend the recipients’ life. The mechanisms of Deforolimus’ immunosuppressive action included induction of Tregs (regulatory T cells), induction of T cells anergy, and decreasing proportion of T cells in spleens and lymph nodes.ConclusionDeforolimus suppressed the immunological rejection of mouse cardiac allotransplantation which laid the foundation of Deforolimus applying to solid organ allotransplantation.

Factors affecting untargeted detection of doping agents in biological samples.

Doping control is essential for sports, and untargeted detection of doping agents (UDDA) is the holy grail for anti-doping strategies. The present study examined major factors impacting UDDA with metabolomic data processing, including the use of blank samples, signal-to-noise ratio thresholds, and the minimum chromatographic peak intensity. Contrary to data processing in metabolomics studies, both blank sample use (either blank solvent or plasma) and marking of background compounds were found to be unnecessary for UDDA in biological samples, the first such report to the authors' knowledge. The minimum peak intensity required to detect chromatographic peaks affected the limit of detection (LOD) and data processing time for untargeted detection of 57 drugs spiked into equine plasma. The ratio of the mean (ROM) of the extracted ion chromatographic peak area of a compound in the sample group (SG) to that in the control group (CG) impacted its LOD, and a small ROM value such as 2 is recommended for UDDA. Mathematical modeling of the required signal-to-noise ratio (S/N) for UDDA provided insights into the effect of the number of samples in the SG, the number of positive samples, and the ROM on the required S/N, highlighting the power of mathematics in addressing issues in analytical chemistry. The UDDA method was validated by its successful identification of untargeted doping agents in real-world post-competition equine plasma samples. This advancement in UDDA methodology will be a useful addition to the arsenal of approaches used to combat doping in sports.

Experimental investigations of CO2 absorption and catalyst-aided CO2 desorption performance of several different amines blending with a promoter

The reaction mechanism of the absorption and the catalytic desorption process. • Batch experiments were conducted in terms of initial absorption rate, initial CO 2 desorption rate (non-catalytic, catalytic), and equilibrium CO 2 solubility. • Comprehensive comparison study of promoting efficiency using MEA and PZ into different single amines. • Comparison of non-catalytic and catalytic desorption performance with the promoter at different conditions. This research presented the new experimental results of the absorption and desorption performance of various single and blended solvents in terms of initial CO 2 absorption rate, initial desorption rate for blank solvents and solvents with the aid of HZSM-5 catalyst, and equilibrium CO 2 solubility. MEA and PZ are two promoters used to facilitate several individual aqueous single solvents including BEA, AMP, BDEA, and MDEA. In order to check the altered performance of absorption and desorption, the solvents were specified at 2.5 M. The initial desorption rate was evaluated by varying the temperature, weight of the solid catalyst, and initial rich CO 2 loading. The experimental results were then taken to compare with the obtained data of the benchmark solution (2.5 M MEA). The comparison results revealed that all the selected blank solvent blends can provide better absorption and desorption performance than the blank benchmark solution. The results also indicated that the performance of catalyst-aided CO 2 desorption could be strongly affected by the rich loading and operating temperature. Meaning that the activation of proton donation by HZSM-5 was patently affected by the above two conditions, which eventually affect the CO 2 separation from the rich solvent.

A Study of the Spectral, Chromatographic and Solubility Characteristics of New Analytical Reagents from Anil-Azo and Their Biological Effects on Bacteria

This study was conducted to create a new reagent from Anil-Azo compounds and study their biological impacts on two types of bacteria. For the first step, four reagents had been created by reaction of p-phenyl diamine in acidic form with 2-formyl-4-methyl phenol in neutral medium to create reagent {1}, which used to produce reagent {2} by reacting it with amino benzothiazole over four hours in the presence of glacial CH3COOH. The reagent {1} was also used to form reagent {3} by reacting it with amino imidazole over two hours. Finally, reagent {3} had been generated by reacting reagent {1} with naphthyl amine (0.2 mol) over four hours in the presence of glacial CH3COOH. The UV-visible spectrum was showed that a new ligand was created between 190-600 nm in reagent {2}, {3} and {4} while reagent {1} was appeared in 519-600 nm area. FTIR spectrum showed that many new coordinate bonds had been formed in different locations. Also, the chromatographic separation study showed that reagent {4} was separated faster than other reagents. Study of compounds stability showed that all reagents were stable in methanol, ethanol, DMSO and DMF. Study of chemical-physical peripteries showed that percentage of reagents’ yield ranged between 80-70%. The assessment of the formulated reagents against various kinds of bacteria was carried out using a medium (agar) via numerous processes. Microbial inhibition was tested at three concentrations: 30, 50 and 70 micrograms, with a blank solvent (DMSO), for bacteria Staphylococcus aureus, E. coli and Streptococcus pneumonia with an incubation period of 24 hours at 37℃. The results of biological impacts showed that reagent {2} showed more inhibition Staphylococcus aureus and Streptococcus pneumonia.

Sandwich injection and analyte protectants as a way to decrease the drift due to matrix effect between bracketing calibration in GC-MS/MS: A case study

In pesticide residues analysis, the drift is the difference between the concentration of two bracketing calibrations in the same batch. According to the SANTE/12682/2019 guideline a criterion of ±30% must be met or positive samples should be reanalyzed. This study aimed to investigate, for the first time, the efficiency of using analyte protectants (Aps) and the sandwich injection approach (SIA) to eliminate the drift between bracketing matrix matched-calibrations taking strawberry as an example. The strawberry samples were prepared according to the citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure, followed by solvent exchange from acetonitrile to n-hexane:actone (9:1). Two batches were injected with the same sequence on GC-MS/MS, the only difference was that the first batch was without Aps and the second was with Aps. The sequence of the batch was as follows: blank solvent injection, 5 strawberry matched-calibrations at 0.05μg/ml, separated by 20 blank strawberry injections after each strawberry matched-calibration injection. The drift was measured by considering the results of the first calibration as 100% and comparing the rest 4 injections with it. After 20 injections, out of the studied 219 pesticides, more than half of the pesticides fell out of criteria when analyte protectants were not used, and by the end of the samples batch 95% of the analytes were out of criteria. Only 8% of the studied analytes were out of criteria for the Aps batch after 20 injections. In the end of the 80 samples batch, 17% were out of criteria. Furthermore, at the end of the protected matrix-matched calibration batch, 90% of the pesticides had an RSD less than 15% in comparison with only 5% of the analytes for the non-protected batch. Moreover, the non-protected batch had an obvious negative drift in comparison with the protected batch. For example, the number of pesticides that had a lower result in the second matrix matched-calibration for the non-protected batch was more than twice the number in the protected batch (194 compared to 91 out of 219 pesticides for both experiments).

Estrogen-regulated expression of SK3 channel in rat colonic smooth muscle contraction

Estrogen can induce inhibition of colonic smooth muscle contraction in male and female mice, which may lead to constipation; however, the mechanisms of inhibition are poorly understood. Hence, this study investigated the effect of estrogen on rat colonic smooth muscle contraction and role of small-conductance Ca2+-activated K+ 3 (SK3) and transcription factors (Sp1 and Sp3) in the underlying mechanisms. The experiment included 24 female Sprague-Dawley (SD) rats divided into 4 groups. The rats were oophorectomized surgically, and a silicone tube containing blank solvent, 0.3mg/mL estrogen (E2), equal-concentration of estrogen and estrogen receptor antagonist (EI), and bovine serum albumin-E2 (BSA-E2) was implanted. The rats were sacrificed on day 14. The molecular insights were confirmed using real-time quantitative reverse transcription PCR (qRT-PCR) and western blot analyses to determine the effect of estrogenic stimulation on gene and protein expression analyses, respectively. The E2 group showed significantly greater SK3 expression (P<.005) compared with other groups and significantly lowers smooth muscle cell (SMC) contractility (P<.005). Estrogen stimulation and SK3 overexpression resulted in a significant decrease (P<.05) in Ca2+ mobilization in the E2 group versus the control group. Further, the E2 group showed significantly higher Sp1 mRNA (P<.05) but lower Sp3 mRNA expression (P<.05) and protein expression (P<.001) compared with other groups. E2 may promote SK3 expression by its genomic effect and inhibit colonic contraction by affecting SK3 expression via an interaction between Sp1 and Sp3.

Electric-Field-Induced Connectivity Switching in Single-Molecule Junctions.

SummaryThe manipulation of molecule-electrode interaction is essential for the fabrication of molecular devices and determines the connectivity from electrodes to molecular components. Although the connectivity of molecular devices could be controlled by molecular design to place anchor groups in different positions of molecule backbones, the reversible switching of such connectivities remains challenging. Here, we develop an electric-field-induced strategy to switch the connectivity of single-molecule junctions reversibly, leading to the manipulation of different connectivities in the same molecular backbone. Our results offer a new concept of single-molecule manipulation and provide a feasible strategy to regulate molecule-electrode interaction.

Synthesis, crystal structure, and antinociceptive effects of some new riluzole derivatives

Nine N-alkylated derivatives of riluzole were synthesized in order to obtain new compounds with potential antinociceptive activity. Riluzole was firstly transformed into (6-trifluoromethoxy-benzothiazol-2-yl)-hydrazine, then it was chlorinated by SOCl2 to obtain 2-chloro-6-trifluoromethoxy-benzothiazole. This intermediate product was treated with nine alkylamines to give N-alkylated derivatives of riluzole respectively. The structures of compounds were confirmed by means of elemental analysis, IR, 1H NMR, and 13C NMR. The synthetic route was optimized and four novel crystals were obtained by recrystallization. This study investigated the antinociceptive activity of some N-alkylated derivatives of riluzole by hot plate test in mice. The relationship between antinociceptive activity and the doses of 4b, 4c, 4h, 4g, and riluzole had been studied. Compared with the control group (0 mg/kg), the effects of compounds 4b and 4h showed a significant increase (13.78 ± 2.89 s, 12.89 ± 2.94 s, respectively). Compound 4c showed extreme significant increase (18.07 ± 3.08 s) in the time mice spent on the hot plate. The compounds 4b, 4c, and 4h had increased the latency time compared to the blank solvent group. They have potential application in developing new drug candidates with antinociceptive activity.

An improved method for the measurement of 3‐monochloropropanediol esters by matrix solid‐phase dispersion supported liquid–liquid extraction

Summary3‐Monochloropropanediol (3‐MCPD) esters are contaminants produced from the high‐temperature processing of edible oils. The accurate measurement of 3‐MCPD using an easy‐to‐follow and reliable method that uses a readily available instrument is important. Here, we report an acid transesterification heptafluorobutyrylimidazole (HFBI) derivatisation method for the accurate measurement of 3‐MCPD esters in edible oils. We developed a dispersed matrix solid‐phase supported liquid–liquid extraction (DMSP‐SLE) system to remove impurities. Both the transesterification and DMSP‐SLE conditions were optimised. A good linear relationship was obtained within the range of 0.05–10 mg kg−1 (R2 ≥ 0.999) in both blank solvent and an oil sample. The limit of detection was 20.36 μg kg−1. The average recovery of the 3‐MCPD esters spiked at 0.5, 1.0 and 2.0 mg kg−1 into a blank oil matrix was in a range from 105.09 ± 2.77% to 120.16 ± 10.88%. The method we developed was further confirmed by performing detection on a Food Analysis Performance Assessment Scheme (FAPAS) sample.

Solid sampling graphite furnace atomic absorption spectrometry for the direct analysis of microextraction solvent bars used for metal ultra-trace pre-concentration

Abstract The potential applicability of the continuum source solid sampling graphite furnace atomic absorption spectroscopy (CS SS-GF AAS) technique has been studied to carry out the direct analysis of microextraction solvent bars used for metal ultra-trace pre-concentration in natural waters. An optimisation of the temperature program was developed for this purpose. Preliminary chamber furnace studies were performed in order to understand the behaviour of the bars with the increasing temperature. Solvent bars were filled with an acceptor solution, impregnated with an organic extractant and placed into the chamber furnace to carry out several temperature programs. Results led to perform a correct optimisation of the drying and pyrolysis steps of the furnace temperature program, which was tested with silver once completed. Blank solvent bars as well as standards containing silver were measured, obtaining a calibration curve with a correlation coefficient of 0.991. The results exhibited good repeatability and reproducibility, with relative standard deviations below 10% in both cases, indicating a promising applicability of the CS SS-GF AAS technique to directly determine metallic species in microextraction solvent bars.

Antitumor efficacy, toxicity and pharmacokinetics of 9-nitrocamptothecin: role of lactone ratio

Since the carboxylate form could be regarded as a possible "source" of lactone form, the optimum ratio of lactone should be determined for the administration of camptothecin (CPT) analogues such as 9-nitrocamptothecin (9-NC). 9-NC solutions with different lactone ratios (100, 75, 50, 25 and 0%) were obtained by the change of pH. The resultant 9-NC solution and corresponding blank solvent were intravenously injected to mice to evaluate toxicity. The S180 tumor-bearing mice were intravenously administered 9-NC solutions with different lactone ratios, and the antitumor efficacy and toxicity were compared. The tissue distribution of lactone and total (the total of lactone and carboxylate forms) 9-NC was also investigated as a function of lactone ratio. Toxicity of 9-NC was found to be increased with the increase in lactone ratio. The tumor inhibitory rates of 9-NC solution were determined to be 64.17, 60.43, 42.78, 41.71 and 8.60% for 100, 75, 50, 25 and 0% lactone ratio, respectively. The lactone stability of 9-NC in most tissues was found to be higher than in plasma. In tumor and plasma, whether for lactone or total 9-NC AUC values, there was no difference between 100 and 75% groups. Although carboxylate form of CPTs is inactive, the administration of carboxylate form in an appropriate ratio is active as a result of its conversion to lactone form in vivo.

A Spectrophotometric Method for the Determination of Ramipril in Solid Dosage Forms

Purpose: To develop a simple and cost effective spectrophotometer method for the determination of ACE inhibitor ramipril in dosage forms. Methods: UV spectrophotometry was used to develop and validate a simple method for the assay of ramipril in solid dosage form at λmax of 210 nm, as per International Conference on Harmonization (ICH) guidelines. Aqueous methanol (5 %) was used as the blank solvent. The method was validated for linearity, recovery, accuracy, precision, specificity in the presence of excipients, and also for inter-day stability under laboratory conditions. Results: Validation results showed linearity in the range 1 – 38 μg/ml; recovery accuracy 101.55%; regression equation Y = 0.0256X + 0.0697, R² of 0.9942; precision RSD < 2.00 %; and negligible interference from common excipients and colorants. The method was accurate (95 % confidence limit) compared to standard liquid chromatography (LC) method, with comparable reproducibility when used to assay a commercial product (Ramitace®, 2 and 5 mg tablets). Conclusion: The validated data were within allowable limits and therefore, the proposed method is recommended for routine quality control (QC) analysis Keywords: Ramipril, Spectrophotmetric assay, Validation, Solid dosage forms

Identification of dissolved organic species in non-drinking tap water by solid-phase extraction and gas chromatography–mass spectrometry

Abstract A method is presented for qualitative identification of dissolved volatile organic compounds (VOCs) in non-drinking tap water samples based on applications of both solid-phase extraction (SPE) and gas chromatography–mass spectrometric (GC–MS) techniques. Water samples were collected and passed over a micro-column packed with acid treated active silica gel phase (pH = 2.6) for adsorption of dissolved organic species under this pH-condition. Silica-bound-organics were then divided into equal portions followed by suspension into organic solvents of different polarities such as methanol, ethanol, butan-1-ol, ethyl acetate, diethyl ether and chloroform. These suspensions were then automatically shaken for 1 h at room temperature. The organic extracts were subjected to GC–MS analysis under temperature programming conditions. The mass spectrum of each eluted chromatographic peak was library searched or manually interpreted to identify the correct name and structure. Blank solvent and silica samples were also subjected to the same GC–MS analysis for comparison.

Streamlining methodology for the multiresidue analysis of β-lactam antibiotics in bovine kidney using liquid chromatography–tandem mass spectrometry

A previously reported multiresidue method for the analysis of 11 important beta-lactams (amoxicillin, ampicillin, cefazolin, cephalexin, cloxacillin, desfuroylceftiofur cysteine disulfide (DCCD), deacetylcephapirin, dicloxacillin, nafcillin, oxacillin, and penicillin G) in bovine kidney has been further streamlined. The method is based on a simple extraction using acetonitrile-water (4:1, v/v), followed by dispersive solid-phase extraction clean-up with C(18) sorbent, concentration of an extract aliquot, and filtration of the final extracts using syringeless filter vials, which are used for the sample introduction in the liquid chromatographic-tandem mass spectrometric (LC-MS/MS) analysis. The recoveries have been improved by adding the internal standard [(13)C(6)]sulfamethazine to the homogenized sample before the extraction step, which enabled a proper control of the volume changes during the sample preparation. Average recoveries of fortified samples were 87-103% for all beta-lactams, except for DCCD, which had an average recovery of 60%. Based on the results of the stability study and LC mobile phase tests, methanol has been eliminated from the entire method, including the LC-MS/MS analysis. The best overall LC-MS/MS (electrospray positive ionization) performance was achieved by using 0.1% formic acid as an additive in both parts of the mobile phase, in water and in acetonitrile. To prevent carry-over in the LC-MS/MS analysis, the LC method was divided into two parts: one serving as an analytical method for injection of the sample and elution of the analytes and the other one, starting at a highly organic mobile phase composition, being dedicated for injection of a solvent, washing of the system, and equilibration of the column to the initial conditions of the analytical method. In this way, a blank solvent is injected after each sample, but these in-between injections contribute minimally to the overall sample throughput.

HPLC DETERMINATION OF 4-ACETYLAMINOPHENYLACETIC ACID

A fast and sensitive reverse phase ion-pair chromatographic method was reported for the separation and quantification of 4-aminophenylacetic acid (Actarit) and its related compounds. The compounds were separated using a Kromasil C18 column (5 μm, 4.6 × 25cm) with a mobile phase containing 70% methanol and 1% Tetrabutylammonium bromide in water flowing at 1.0 mL/min, and were detected using a UV detector operating at 245nm. Actarit was completely separated from its related compounds that included its synthetic starting materials and degradations. The retention times were 3.1, 4.0, 9.4, 21.4, and 25.8min for blank solvent, 4-aminophenylacetic acid, Actarit, 4-nitrophenylacetonitrile, and 4-nitrophenylacetic acid, respectively. Three known and one unknown compound (retention time 13.7minute) were detected after Actarit was boiled in acidic, neutral, and basic conditions, each for two hours. The linear response between peak area (A) and Actarit concentration (c) over the range of 0.5 - 2.5 μg/mL was The detection limit at signal-to-noise ratio two was 5.08 ng/mL. The recovery was 98.64 – 101.72% (n=5) (within day) and 99.60 – 101.86% (n=5) (day to day). The relative standard deviations were 0.87 – 1.77% (n=5) (within day) and 0.51 – 1.92% (n=5) (day-to-day), respectively. Good correlation was found between this HPLC method and a spectrophotometric method when measuring the contents of Actarit in three batches of commercial tablets. The contents were 97.32, 99.20, and 97.58% when measured by this HPLC method, and 97.76, 100.43, and 98.02% by a spectrophotometric method. Good separation, linearity, recovery, and accuracy implied that the chromatographic method is suitable for quantitative analysis of Actarit.

Enhancement of an Insufficient Dye-Formation in the Ninhydrin Reaction by a Suitable Post Treatment Process

A study of the reaction between ninhydrin and alanine has been carried out taking into account that, adhered on the surface of a dry porous medium such as paper, a quasi-heterogeneous reaction has to take place. Instead of amino acids released from human sweat glands, aqueous solutions of alanine were taken to deliver a given amount of amino acid to the sample. The dye density, obtained after using a standard development process, could noticeably be increased by setting a drop of water on the dye dot, thus indicating that not all the alanine had been used for dye formation during the usually applied process. The incomplete reaction can be explained by the problem of bringing the reactants into contact with each other when both are in the solid phase in the porous surrounding. The temporary presence of water allows a reorientation of the insoluble reactants. With fingerprints an increase in both the rate of development and the final dye density could be obtained when the sample was post treated after the developing process with the blank solvent, thus also the background coloration could be decreased. The ideas presented in this paper may form the basis for a modification of developing processes with ninhydrin in order to increase the proportion of amino acids present (in the sample) used in dye formation without data loss.