Flow Injection Analysis Method Research Articles

A Rapid Continuous Flow Injection Analysis Method Development for Diphenhydramine Hydrochloride

Background: Diphenhydramine hydrochloride (DPH) is widely used as an antihistamine for treating various allergic conditions and symptoms. Traditional analytical methods for quantifying DPH often involve complex procedures and instrumentation. However, recent advancements in nanotechnology and analytical techniques offer opportunities for developing simpler and more efficient methods for DPH analysis. Method: This study presents a novel approach for quantifying DPH using continuous flow injection analysis (CFIA) combined with turbidimetric measurements. The precipitation reaction between DPH and 3,5-dinitro salicylic acid was utilized in an aqueous medium system. Various physical and chemical parameters were optimized, including the concentration of precipitating reagent, reaction medium (acids and salts), irradiation source intensity, volume of sample segment, and delay reaction coil. Results: Optimization of physical and chemical parameters revealed that a concentration of 15 m.mol/Liter for 3,5-dinitro salicylic acid, distilled water as the reaction medium, and an irradiation source intensity of 3.1 VDC produced optimal results. The linear dynamic range for DPH concentration was determined to be 0.01-20 m.mol/Liter. Comparison with the traditional UV-spectrophotometric method showed comparable results, indicating the reliability of the proposed CFIA method. Conclusion: The CFIA method presented in this study offers several advantages over traditional analytical methods for quantifying DPH in pharmaceutical formulations. It provides high sensitivity, speed, simplicity, and improved accuracy. The proposed approach has the potential for widespread application in pharmaceutical analysis, offering a cost-effective and easily manipulable solution for routine laboratory use. Overall, this study demonstrates a significant advancement in the measurement of DPH, which could simplify processes for pharmaceutical analysis and enhance industrial production levels.

Fast New Method for Estimation of Captopril in Pure and Pharmaceutical Preparation by Reaction with Ammonium Ce (IV) Sulfate in Acid Medium

The determination of captopril (CAP) using a new continuous flow injection analysis (CFIA) method was given in this work CAP in its pure state and some of its pharmaceutical preparations. The technique can be described as simple, fast, sensitive, easy to operate, and low-cost. The CAP reacted with ammonium ceric(IV) sulfate (ACS)2(NH4 )2SO4Ce(SO4)2. 3 H2O in an acidic medium and the reaction led to the formation of a white, slightly yellowish precipitate. The formed precipitate was studied using Ayah 6S×1-ST-2D Solar cell-CFI Analyzer, a through the reflection of accident light on the surfaces of the precipitate particles at (0-1800), expressed as the response of the transducer measured in (mV). Some chemical and physical parameters were studied to provide the optimal conditions for the study. The calibration curve within the range of (0.07-3.0) mmol/L was linear, with a correlation coefficient (r) value equal to (0.9983), and the percentage value of linearity (R2%) was (99.65). The method's detection limit (L.O.D.) of the new method was 272.5 ng/25 µL; it was calculated by diluting the minimum concentration in the calibration curve gradually. RSD% was less than 0.2% for 0.9, 1.5, and 3.0 mmol/L concentrations of C.A.P. for n=8. The method was successfully applied to estimate C.A.P. in three pharmaceutical preparations, each produced by a different company. The new method was compared with the UV-Spectrophotometric method (classical method) at λmax= 207.2 nm by using the method of standard additions. Both the t-test and the F-test were conducted to ensure that there wasn't a significant difference between the new method and the conventional one. The results of both tests showed, at a confidence level of 95%, that there was no significant difference.

Continuous Flow Injection Analysis Method for the Determination of a Drug Diphenhydramine Hydrochloride by Using Phosphomolybdic Acid

The study presented a new method for determining diphenhydramine hydrochloride (DPH) in its pure form and some pharmaceutical preparations, within CFIA technique. The method is simple, fast, sensitive, easy to operate, and of a low cost. It is based on the reaction of DPH with phosphomolybdic acid (PMA), in aqueous media, forming a white, slightly yellowish precipitate. The precipitate formed was studied using an Ayah 6S×1-ST-2D solar cell CFI analyzer, by the reflection of incident light off the surfaces of the deposited particles at (0–180°), expressed as the response measured in (mV) . Some chemical and physical variables were studied to provide optimal conditions for the study. The linear range was 0.07-9 mmol/L and it had a correlation coefficient (r) with a value of (0.9998). The limit of detection (L.O.D.) of the new method was 729.55 ng/sample, calculated by gradually diluting the lower limit of the concentration in the linear range (0.07 mmol/L). The % RSD was less than 0.2% for a concentration of 0.1, 4.0 and 10.0 mmol/L of DPH for n = 8. The method was successfully applied in the determination of DPH in three samples from three different pharmaceutical production companies. Using the standard addition method, the new method was compared with the UV-Vis spectrophotometry method at λmax = 258 nm. Both T-test and F-test. The results of the two tests showed no significant difference at a confidence level (95%).

Precise evaluation of batch adsorption kinetics of plant total polyphenols based on a flow-injection online spectrophotometric method.

Efficient evaluation of adsorption kinetics of plant total polyphenols is essential for the design of adsorption separation of bioactive compounds. The conventional method uses manual sampling with poor reproducibility. Here, we developed a new method for on-line determination of total polyphenol content (TPC) in plant extracts by applying the Folin-Ciocalteu method in flow-injection analysis (FIA). The FIA parameters were optimized and a standard curve with excellent linearity was established. Precise determination of TPC with a satisfactory sample throughput of 20 h-1 was achieved for the adsorption kinetic study. The pseudo-second-order kinetic model was found to better describe the kinetic parameters of the batch adsorption/desorption process. The developed method proved to be accurate compared with the conventional method. The FIA method holds significant promise for studying and monitoring adsorption processes, due to its automatic on-line nature, low consumption of reagents and samples, and the ability to generate large quantities of highly accurate adsorption data.

Flow injection analysis system with smart phone for the determination of total phenolic compounds in wastewater using Folin Ciocalteu reagent

Smart phones are playing a big role in daily life and are being employed as supporting hardware in a variety of chemical analysis applications. flow injection analysis method for the rapid, simple, and straightforward determination of total phenols using Folin-Cioclteu reagent .The sample or standard solutions were injection into a carrier stream to react with reagent and detected by spectrophotometer at 765 nm . The experimental conditions such as flow rate of reagent and carrier ,reagent volume ,length of reaction coil and concentration of reagent were optimized .A good linear calibration curve in the range of (250-2000 mg L-1 ) was obtained with regression equation ( y=0.0123 x + 0.1857) ,( R= 0.999 ), the limit of detection was in the amount of ( 0.0102 mg L-1) .The method was successfully applied for the determination of the total phenols in wastewater .

Development of a second-tier method for C4, C5 and C2 acylcarnitine analysis in plasma

IntroductionAcylcarnitines are typically analyzed using either a flow injection analysis (FIA) method or liquid chromatography-mass spectrometry (LC-MS/MS) methods. The FIA method is a fast, efficient method, however it does not have the capability to separate compounds with the same molecular weight. These isobaric interferences can be removed by chromatographic separation with LC-MS/MS. In this study, we aimed to develop and optimize a qualitative LC-MS/MS method to separate the isobaric interferences for two-, four- and five-carbon acylcarnitines. MethodsThe samples were first prepared by acylcarnitine derivatization with butanolic HCl. The developed LC-MS/MS method is a combination of isocratic and gradient elution used to separate acylcarnitines. Multiple reaction monitoring was used for determination of precursor and product ions for each acylcarnitine species as well as known interferences used in our study. We used this method to analyze quality assurance and patient samples with elevated two-, four- and five-carbon acylcarnitines. ResultsButyryl- and isobutyrylcarnitines as well as valeryl- and isovalerylcarnitines were successfully separated using the developed method. This method was able also to separate and distinguish acetylcarnitine from glutamate interference that has been causing overestimation of acetylcarnitine. In patients, the dominant five-carbon acylcarnitine was found to be isovalerylcarnitine. We confirmed that the majority of analyzed patient samples had additional carnitine adducts present but not valerylcarnitine. Butyryl- and isobutyrylcarnitines, in variable ratios, were present in every patient sample. ConclusionWe developed a qualitative LC-MS/MS method for butyl-ester derivatized acylcarnitines, which can be used as a second-tier method for diagnosis and monitoring of various inborn errors of metabolism in our hospital network.

Normal and Reverse Flow Injection Analysis Methods for Estimation of Mesalazine in Pharmaceutical Dosage Forms

Determining the actual amounts of active ingredients in various pharmaceutical commercial forms is still receiving a lot of attention. Two flow injection analysis (FIA) methods were suggested for determination of mesalazine (MES) in pharmaceutical forms. Normal and reverse FIA systems (nFIA and rFIA) combined with UV-Vis spectrophotometric technique were used for the analysis. The methods involved using two mods of FIA systems for measuring a colored product result from coupling of MES with 2,2'-dihydroxybiphenyl after oxidized with sodium periodate in alkaline medium. The absorbance of the red colored dye was measured at maximum wavelength of 500 nm. The calibration graphs for MES were linear in the ranges 2.5-200 and 0.5-60 µg/mL with RSD of best than 3% for both methods respectively. Also the limits of detection were 1.2 and 0.2 µg/mL and limits of quantitation were 3.6 and 0.7 µg/mL of MSL for nFIA and rFIA systems respectively. All physical and chemical conditions of flow systems such as flow rate, reaction coil length and reagent concentrations were carefully studied. The proposed methods were applied for determining MES in four commercial tablets without any interferences.

Development of improved flow analysis prototype method for measuring and understanding agricultural non-point source (NPS) nitrogen (N) and phosphorus (P) pollution

The loss of nitrogen (N) and phosphorous (P) through continuous surface runoff by rainfall after fertilizing and leaching into groundwater has become a critical issue that causes eutrophication of rivers, lakes, and even drinking water, resulting in agricultural non-point source (NPS) pollution of up to 50 % of pollution load. Traditionally, N and P were measured using the laboratory's flow injection analysis (FIA) method before evaluating the pollution load, which could meet urgent requirements in the fast response, prevention, and control of agricultural NPS pollution. Herein, we propose an improved flow analysis (perturbation dispersion) method by integrating chemical reaction chambers to measure nitrogen and phosphorus in water automatically and continuously. The as-fabricated system was validated with real samples from Qianjiang, Hubei Province. The experimental results drew a correlation coefficient of 0.91449 for ammonium nitrogen between the existing lab-based flow analysis method and the innovative (improved) flow analysis method. The correlation coefficients of 0.99828, 0.85129, and 0.99206 for nitrate nitrogen, ammonium nitrogen, and phosphorus were calculated from the measurement results. The detection limits of 0.55, 0.20, and 0.025 mg/L with relative standard deviations (RSD) of 0.8 %, 5.7 %, and 0.9 % were observed for NH4+–N, NO3––N, and PO43− measurements, respectively. This work facilitates the online and continuous control of the NPS pollution load and timely expands the flow injection analysis (FIA) techniques for understanding the pollutants in water and farmland environments.

The determination of zinc using flow injection and continuous flow analysis combined with a polymer inclusion film-coated column: Application to the determination of zinc in alloys and commercial lithium chloride

A column coated with a polymer inclusion film (PIF) containing Aliquat 336 as carrier cast on glass beads packed in a glass tube is described for the separation, preconcentration, and determination of zinc(II) in flow injection analysis (FIA) and continuous flow analysis (CFA) systems. In the FIA method, 200 μL of a sample solution containing 2 mol/L lithium chloride is injected into a 2 mol/L lithium chloride stream. This converts zinc(II) ion into its anionic chlorocomplexes which are then extracted into the Aliquat 336-based PIF by anion exchange. The extracted zinc(II) is then back-extracted into a stream of 1 mol/L sodium nitrate solution and determined spectrophotometrically using 4-(2-pyridylazo)resorcinol as the color reagent. The limit of detection (LOD, S/N = 2) was determined as 0.017 mg/L. The usability of the PIF-based FIA method was demonstrated by the determination of zinc in alloys. The PIF-coated column was also employed successfully in the CFA determination of zinc(II) as an impurity in commercial lithium chloride samples. For this, 2 mol/L commercial lithium chloride solution was passed through the column for a predetermined time period followed by stripping in a stream of 1 mol/L sodium nitrate solution.

Spectrophotometric Analysis of Nitrite in Gunshot Recentness Examinations from Non Toxic Ammunitions: Expanding the Frontiers of Forensic Chemistry

Nitrite ions consist on an important chemical clue related to gunshot examination, concerning to estimation of the time since discharge. Current forensic laboratory methods for nitrite analysis in gunshot residues are well established for investigating conventional ammunition residues. However, the use of these methods to analyze the so-called ecological or “non-toxic” ammunition has been less studied. Here, we have developed a spectrophotometric flow injection analysis method to test nitrite in samples of “non-toxic” ammunition residues. The ammunition used in these experiments was the NTA (non-toxic ammunition) model, .38 caliber, We also investigated the kinetics of nitrite decomposition for this type of ammunition over time. Sulfanilic acid and 1-naphthylethylenediamine in acetic acid were used as colorimetric reagents. The linear dependence of the spectrophotometric signal on the nitrite concentration was as follows: A = 2.07 x 104 µmol-1 L [NO2-] + 6.78 x 10-3 with a correlation coefficient (r) of 0.9994. The standard deviation (SD) of the analytical curve was 3.17 x 10-3 resulting in a limit of detection (LOD) = 0.46 µmol L-1 and a limit of quantification (LOQ) = 1.56 µmol L-1. The proposed instrumental method was more sensitive than conventional colorimetric tests and permitted the detection window to be extended to 32 days while ensuring the safety and reliability required for forensic analysis, in comparison to 7-10 days usually proposed for conventional ammunition. Therefore, the proposed method can be safely employed in forensic laboratories for routine analysis of nitrite ions in GSR samples from ecological or “non-toxic” ammunition.

Chromatographic and Automated Spectrophotometric Determination of Some Antipsychotic Drugs in Pharmaceutical Products

Chromatographic and spectrophotometric methods for the quantitative determination of three antipsychotic drugs in pharmaceutical products were developed. The investigated drugs are quetiapine fumarate, olanzapine and risperidone. The flow injection analysis (FIA) method is based on the oxidation of these drugs by potassium permanganate in a basic medium. The resulting green color was monitored at 433 nm. Optimization of chemical and FI variables has been made. Under the optimized conditions, the sampling rate was about 80 injections/hour. The method is fast, simple and sensitive. For the chromatographic method, a reversed-phase Varian C8 column was used at ambient temperature. The mobile phase was a mixture of acetonitrile (ACN), acetate buffer and triethylamine (TEA), (60% ACN, 39.8% acetate buffer and 0.2% TEA, v/v/v), adjusted to pH = 4.7 with acetic acid. Tetrazolium salt was used as an internal standard. The absorption of the eluted compounds was measured using a variable-wavelength UV detector at 278 nm. The methods were applied successfully for the assay of three antipsychotic drugs in pharmaceutical products and no interferences were observed from the common excipients usually used. The proposed methods were validated for their accuracy and precision.

High-performance amperometric determination of nitric oxide released by endothelial cells using flow injection analysis

An amperometric flow injection analysis (FIA) method based on an optimized carbon paste electrode (CPE) for the determination of nitric oxide (NO) production from endothelial cells (ECs) was developed. The CPE was modified by Nafion, gold nanoparticles (AuNPs) and graphene nanoribbons (GNRs) via drop casting method. The proposed sensor exhibited excellent sensitivity and selectivity to the oxidation of NO with a linear correlation of 0.02 - 22.4 μM and a detection limit of 6 nM. The developed method is applied for real-time measurements of NO released from endothelial cells by stimulation of endothelial NO synthase (eNOS). Induction of NO synthesis by eNOS was successfully initiated by the calcium ionophore A23187, acetylcholine (ACh), or L-arginine. Furthermore, a reduction of eNOS activity could be observed after the addition of a NOS inhibitor, resulting in a decrease in NO signaling. Targeting eNOS could be of considerable value with regard to preventing or treating the development of cardiovascular diseases. The sensor’s ease of fabrication and applicability for cell measurements enables the device to be used in pharmacological research and drug discovery.

An improved reverse flow injection analysis (rFIA) technique for determination of nanomolar concentrations of ammonium in natural waters with automatic background fluorescence detection: Ammonification during a Karenia brevis bloom in Tampa Bay

Ammonium is the most energetically favorable form of inorganic nitrogen that phytoplankton can take up, and its availability often limits phytoplankton biomass. Recently, the majority of methods for quantification of ammonium at nanomolar concentrations have used the reaction between ammonium and o-phthaldialdehyde (OPA). Two different approaches have been employed. One involves gas diffusion of ammonia across a membrane. The other entails a more direct approach and utilizes sulfite as a reducing agent to form a fluorescent product. A benefit of the separation technique is that natural fluorescence of the samples does not yield a false positive signal, however membrane failure and clogging are challenging analytical problems. The direct reaction between the analyte and OPA, although devoid of problems associated with membranes, requires a correction for background fluorescence. This work presents the development of a reverse flow injection analysis (rFIA) method with automatic background fluorescence correction and a low detection limit, along with its application to measure underway ammonium concentrations in Tampa Bay during a bloom of the toxic dinoflagellate Karenia brevis with concurrent fish kills in June of 2021. During field testing elevated concentrations of ammonium were found to coincide with the largest number of observed floating dead fish and lethal K. brevis concentrations. The method employs a sulfite-formaldehyde reagent mixed with the sample into which an OPA reagent is injected and heated to activate fluorescence. Fluorescence of the sample is measured before the injection of OPA and at the peak of OPA injection, allowing for differentiation of the background fluorescence from the signal proportional to analyte. The detection limit and the limit of quantitation for this technique are 2.3 nM and 7.5 nM, respectively, and the coefficient of variation is 0.6% for replicate deionized water blanks (N = 10). Advantages of this method compared to techniques capable of both nanomolar detection of ammonium and improved accuracy via background fluorescence correction include a greater sample throughput, an increase in reported useful reagent lifetime, and the ability to quantify ammonium in coastal waters.

The Determination Method of Total Polyphenol in Tea and Substitute Tea Based on [Ag(HIO6)2]5--Luminol Chemiluminescence System.

Scientific, accurate, and rapid detection of the composition and content of tea polyphenols is an important basis for their rational use and giving full play to their physiological effect. The spectrophotometric assays for total polyphenols have poor selectivity. Therefore, there is a need to develop a simple and reliable method for the determination of the total polyphenolic level in tea products. The aim of this research was to develop a flow injection chemiluminescence (FI-CL) method based on the Ag(III)-luminol system for the total polyphenol content analysis of tea and substitute tea. Through Box-Behnken experimental design, we selected the optimum determination condition. The Ag(III) concentration was 5 × 10-5 mol/L, and the luminol concentration was 3 × 10-7 mol/L (including 0.15 mol/L NaOH). The peristaltic pump is 25 r/min, and the photomultiplier voltage is 600 v. Sample extracts were diluted 100 000 times for the FI-CL assay. Under optimal conditions, CL intensities were proportional to total polyphenol content (in terms of gallic acid concentrations) in the range of 0.1∼100 μg/L. The LOD and LOQ were 0.03 μg/L and 0.1 μg/L. The recovery values were in the range of 86.3-111.0% with a RSD of 1.04∼2.62%. The polyphenolic content of 12 teas and 6 substitute teas was determined, and the results of the developed method and Folin-Ciocalteu method were highly correlated (r = 0.9493 for tea and r = 0.8533 for substitute tea). The proposed method is better than the Folin-Ciocalteu method in terms of selectivity, sensitivity, and accuracy. It is suitable for the determination of polyphenol content not only in tea, but also in substitute tea. We developed a new flow-injection analysis method for polyphenolic content determination based on the Ag(III)-luminol chemiluminescence system. It is simple, rapid, sensitive, and accurate. It is suitable for the determination of polyphenols content not only in tea, but also in substitute tea.

Flow Injection Spectrophotometric Technique for Determining of Genistein in Pure and Supplements Formulations Through Diazotization Coupling Reaction

Genistein (GEN) is The major isoflavone found in soybeans, has a number of cardiovascular health benefits, Postmenopausal syndrome and osteoporosis. A direct flow injection analysis method for estimation of (GEN) in pure and supplements formulation . This system is based on diazotization coupling reactions between procaine penciline (PR) and genistein in basic medium, they formed yellow dyes have maximum absorption at 416 nm. Calibration curve were constructed over different GEN concentrations, linearity for GEN was 10-100 µg.mL-1 and detection limits of 1.51 ?g/mL. In the FIA technique, all analytical factors were analyzed and optimized. The established method was successfully used to determine GEN in the formulations of its supplement

CHANGES IN THE CONTENT OF β -GLUCANS DURING THE MALTING PROCESS

β-glucans are non-starch polysaccharides found in the cell walls of endosperm. A high content of these polysaccharides in barley grain causes inadequate grain modification during the malting process, due to the fact that β-glucans inhibit enzymes to enter the cell walls of the endosperm. During malting process, barley germinates and produces hydrolytic enzymes that de-structure the endosperm, making the grains soft and friable. During mashing process, β-glucans lower the brewing yield and moreover they cause turbidity of brewed beer. The goal of this work was to analyse the degradation process of β-glucan content during the malting process. Two methods such as the enzymatic method and the flow injection analysis method were used to analyse the content of β-glucan in barley grain, in germinated grain as well as in the malt and in wort. Results showed the decrease of β-glucan content from barley to wort, β-glucans were degraded by 97 %. All evaluated varieties fulfilled requirements for β-glucan content in wort, values were lower than 250 mg.dm-3. Moreover, a positive significant correlation among the content of β-glucan in malt and the viscosity of worth was found but on the other hand significant correlation among the β-glucan content in wort and the viscosity was not proven. Statistical significant correlation was proven among the starch content in barley grain and friability of malted grain.

Development of continuous flow injection analysis method for determination of oxymetazoline and vancomycin hydrochloride in pharmaceutical preparations

ABSTRACT. Continuous flow injection (CFI)-spectrophotometric method has been developed for oxymetazoline (OXY) and vancomycin hydrochloride (VAN) determination in pure and dosage forms. Sulfadimidine drug was used as a safe chromogenic reagent by diazotization coupling with studied drugs to produce sensitive azo dyes with maximal wavelengths of 498 and 441 nm, respectively, for OXY and VAN drugs. The effect of various chemical and physical conditions on the signal response has been studied. Under optimum conditions, Beer’s law was linear over the concentration range of 5–200 and 6–200 µg/mL with limits of detection of 2.19 and 1.79 µg/mL for OXY and VAN, respectively. The CFI systems gave a sample throughput of more than 120 samples per hour for 150 μL injection volume for both drugs. The proposed methods were used for the estimation of microgram quantities of both drugs in their different dosage forms with great effectiveness. The method's validity and applicability were thoroughly investigated and the recoveries values were compared with those of standard pharmacopeia methods. The specified approaches were used without the excipients interfering in pharmaceutical applications.
 
 KEY WORDS: Oxymetazoline hydrochloride, Vancomycin Hydrochloride, Flow injection, spectrophotometry, Pharmaceutical formulations
 
 Bull. Chem. Soc. Ethiop. 2022, 36(2), 303-313. 
 DOI: https://dx.doi.org/10.4314/bcse.v36i2.5 

A Continuous Flow Injection/Indirect Photometric Method for the Detection of Fosetyl Aluminum in Commercial Pesticide Formulations

AbstractBecause of their Physico‐chemical characteristics and its composition, the development of new specific analytical methodologies to determine some highly polar pesticides are required. The reported methods demand long analysis time, expensive instruments and prior extraction of pesticide for detection. The current work presents a new flow injection analysis method combined with indirect photometric detection for the determination of Fosetyl‐Aluminum (Fosetyl‐Al) in commercial formulations, with rapid and highly accurate determination involving only construction of manifold system combined with photometric detector without need some of the pre‐treatments to the sample before the analysis such as extraction or separation. The proposed method is based on the reaction between the Fosetyl‐Al with the colorimetric reagent (Aluminon dye) in an aqueous medium of sodium nitrite resulting in the formation of a red complex and its absorbance is measured using the photometric detector. The proposed method included optimization of several parameters such as sodium nitrite concentration, flow rate, sample volume, Aluminon dye concentration, mixing coil and light intensity. The linear range of the detector response was in the range of 0.005–1.8 mmol/L for the sample with r (coefficient of determination) 0.9909, R2 (correlation coefficient) 0.9954 at 95 % and 0.0041 mmol/L as a limit of detection. The relative standard deviation was less than 1.5 % for 0.005 mmol/L of the analyte (n=11). The proposed method was validated and applied successfully for the determination of Fosetyl‐Al in commercial formulations and can be used as an alternative method for quality control assessment.

Newborn Screen for X-Linked Adrenoleukodystrophy Using Flow Injection Tandem Mass Spectrometry in Negative Ion Mode.

X-linked adrenoleukodystrophy (X-ALD) is a genetic disorder caused by pathogenic variants in the ATP-binding cassette subfamily D member 1 gene (ABCD1) that encodes the adrenoleukodystrophy protein (ALDP). Defects in ALDP result in elevated cerotic acid, and lead to C26:0-lysophosphatidylcholine (C26:0-LPC) accumulation, which is the primary biomarker used in newborn screening (NBS) for X-ALD. C26:0-LPC levels were measured in dried blood spot (DBS) NBS specimens using a flow injection analysis (FIA) coupled with electrospray ionization (ESI) tandem mass spectrometry (MS/MS) performed in negative ion mode. The method was validated by assessing and confirming linearity, accuracy, and precision. We have also established C26:0-LPC cutoff values that identify newborns at risk for X-ALD. The mean concentration of C26:0-LPC in 5881 de-identified residual routine NBS specimens was 0.07 ± 0.02 µM (mean + 1 standard deviation (SD)). All tested true X-ALD positive and negative samples were correctly identified based on C26:0-LPC cutoff concentrations for borderline between 0.15 µM and 0.22 µM (mean + 4 SD) and presumptive screening positive at ≥0.23 µM (mean + 8 SD). The presented FIA method shortens analysis run-time to 1.7 min, while maintaining the previously established advantage of utilizing negative mode MS to eliminate isobaric interferences that could lead to screening false positives.

Improving the measurement of total dissolved sulfide in natural waters: A new on-site flow injection analysis method

Total dissolved sulfide (TDS) plays multiple important roles in the aquatic environments. However, the determination of trace levels of TDS in natural waters is challenging because TDS is vulnerable to oxidation and volatilization. In this study, a fully automated flow injection analysis spectrophotometric system, incorporating a hollow fiber membrane contactor (HFMC) and a long path length liquid waveguide capillary cell, was fabricated to facilitate the on-site measurement of trace TDS in natural waters. The HFMC was used for matrix separation and analyte preconcentration. The measurement was based on the reaction of sulfide and N,N-dimethyl-p-phenylenediamine in the presence of FeCl3 under acidic conditions to yield methylene blue (MB). The proposed method was highly sensitive, with detection and quantification limits of 0.57 and 1.90 nmol L−1, respectively. The linear working range was from 1.90 to 150 nmol L−1, with a correlation coefficient of 0.9995. The repeatability, expressed as the relative standard deviation, was less than 0.86% (n = 15) and the recoveries varied from 76.2 ± 0.1% to 103.9 ± 0.6% (n = 3) for spiked samples. This method was applied to conduct a field analysis of TDS in a reservoir, giving results aligned with those obtained using a standard MB method. This work demonstrates that the new method for determining TDS was effective for both laboratory analysis and on-site measurement.