A portable, inexpensive and microcontrolled spectrophotometer based on white LED as light source and CD media as diffraction grid

A portable, microcontrolled and low-cost spectrophotometer (MLCS) is proposed. The instrument combines the use of a compact disc (CD) media as diffraction grid and white light-emitting diode (LED) as radiation source. Moreover, it employs a phototransistor with spectral sensitivity in visible region as phototransductor, as well as a programmable interrupt controller (PIC) microcontroller as control unit. The proposed instrument was successfully applied to determination of food colorants (tartrazine, sunset yellow, brilliant blue and allura red) in five synthetics samples and Fe²⁺ in six samples of restorative oral solutions. For comparison purpose, two commercial spectrophotometers (HP and Micronal) were employed. The application of the t-paired test at the 95% confidence level revealed that there are not significant differences between the concentration values estimated by the three instruments. Furthermore, a good precision in the analyte concentrations was obtained by using MLCS. The overall relative standard deviation (R.S.D.) of each analyte was smaller than 1.0%. Therefore, the proposed instrument offers an economically viable alternative for spectrophotometric chemical analysis in small routine, research and/or teaching laboratories, because its components are inexpensive and of easy acquisition.     

A near infrared spectroscopic discrimination of noodle flours using a principal-component analysis coupled with chemical information.

Using a portable near infrared (NIR) spectrometer, we discriminated flours for making Japanese noodles (Soba), not only relying on a statistical and mathematical approach, but also on a chemical interpretation of the NIR spectra. In original NIR spectra, the particle-size difference, which results in an undesired systematic variation, was extracted and interpreted as the first-principal component factor by a principal-component analysis. The discrimination of flour materials cannot be satisfied by this factor. However, after a standardized treatment for the original spectra, the particle-size effects were eliminated; alternatively, differences in the chemical contents were extracted as principal-component factors. Using these factors, flour material discrimination was achieved much better. This study suggests a novel idea of utilizing the wavelength contribution ratio spectra for interpreting the factors extracted from the principal-component analysis for the NIR spectra. This report also describes the relationship between the NIR spectra and the chemical-analysis data.     

Real-time quantification for sulfite using a turn-on NIR fluorescent probe equipped with a portable fluorescence detector

Sulfur dioxide and its derivative sulfite widely existed in air, water as the environment pollutant. Sulfite is also commonly used as preservative and additive in fresh fruits, vegetables, wines and pharmaceutical materials. Due to sulfite is closely related with human diseases, it is very urgent for the sensitive and rapid quantification of sulfite in various samples. In our study, a turn-on near infrared (NIR) fluorescent probe (MDQ) was developed for sulfite detection based on a Michael addition reaction, with high sensitivity (LOD 4.16 nmol/L), selectivity and fast response time (400 s). Using MDQ, a quantify method for sulfite in traditional Chinese medicines (TCMs) was developed with the advantages of high precision, accuracy and convenient operation. Furthermore, according to the photophysical property of MDQ, a portable fluorescence detector is designed to quantify sulfite for TCMs and surface water in Dalian city of China. Therefore, the developed fluorescent probe MDQ and portable fluorescent detector as a rapid inspection instrument were successfully used to real-time monitor the sulfite in various complex samples.     

Capacitance‐to‐digital: The upgrades of single chip detector

The capacitance‐to‐digital single chip detector was upgraded. The paper discusses hardware issues and benefits of the designed/upgraded detector. The device can be operated from rechargeable lithium‐ion battery as stand‐alone, portable system and is capable of transmitting real‐time data wirelessly. The detector and additional modules (battery, battery holder, microcontroller board, wireless module) weight is less than 85 g. Electrophoretic separation in low conductivity 20 mM MES/L‐His buffer, pH 6.1, was performed in order to evaluate detection parameters. The system is capable of quantification of potassium ions down to 0.31 μM. Investigation of differential signal acquisition configuration showed improved performance regarding external noise and temperature fluctuations. The system can be a solution for stand‐alone, field‐portable capillary format separation detector.     

Naked‐Eye Readout of Analyte‐Induced NIR Fluorescence Responses by an Initiation–Input–Transduction Nanoplatform

Fluorescence visualization (FV) in the near‐infrared (NIR) window promises to break through the signal‐to‐background ratio (SBR) bottleneck of traditional visible‐light‐driven FV methods. However, straightforward NIR‐FV has not been realized, owing to the lack of methods to readily transduce NIR responses into instrument‐free, naked eye‐recognizable outputs. Now, an initiation–input–transduction platform comprising a well‐designed NIR fluorophore as the signal initiator and lanthanide‐doped nanocrystals as the transducer for facile NIR‐FV is presented. The analyte‐induced off–on NIR signal serves as a sensitizing switch of transducer visible luminescence for naked‐eye readout. The design is demonstrated for portable, quantitative detection of phosgene with significantly improved SBR and sensitivity. By further exploration of initiators, this strategy holds promise to create advanced NIR‐FV probes for broad sensing applications.     

Features of a micro-gas chromatograph equipped with enrichment device and microchip plasma emission detection (muPED) for air monitoring

A field portable gas chromatograph (GC) was constructed allowing the enrichment of organic solutes from air samples on a miniaturized chemical trap and the subsequent gas chromatographic analysis on a resistively heated capillary column. The heart of the system is an integrated chip-based plasma emission detector (muPED). As a non-selective detector, the sensitivity is similar to that of a flame ionization detector (FID). The detector shows good selectivity for phosphorus, sulfur and chlorine-containing compounds with relative selectivities of ca. 5 x 10(5) gP gC(-1), 50 gS gC(-1) and 10(2) gCl gC(-1). The lifetime of the plasma chip under air monitoring conditions exceeded 3000 analyses.     

中药口服固体制剂原辅料近红外光谱数据库的构建及应用

建立了中药口服固体制剂原辅料近红外(NIR)光谱数据库,采用模式识别方法研究了NIR光谱数据在物料分类和物性预测中的应用。使用便携式近红外光谱仪快速测量149批原辅料粉末的NIR漫反射光谱数据,并录入iTCM数据库。利用主成分分析(PCA)法探究NIR光谱数据对已知结构物料的分类能力,采用偏最小二乘(PLS)法研究了NIR光谱对原辅料物性参数和直接压片片剂性能的预测能力。经标准正态变量变换(SNV)+Savitzky-Golay(SG)平滑+一阶导数处理后的NIR光谱数据对微晶纤维素、乳糖、乙基纤维素、交联聚维酮和羟丙基甲基纤维素这5类辅料的区分能力较好。NIR光谱数据与原辅料粉末粒径、密度和吸湿性的相关性较强。NIR光谱信息作为物料物理性质的补充,可提高粉末直接压片片剂性能预测模型的性能。NIR光谱数据是iTCM数据库物性参数数据的补充,物性参数与NIR光谱数据的结合能更全面地表征原辅料的性质。     

手持式智能光度计的研制及应用

本文研制了手持式智能光度计。该仪器集成了光源、进样系统和检测器,体积小巧,采用吸入式进样系统取代比色皿设计,试剂消耗量仅为比色皿的10%。使用该仪器进行了甲醛标准样品测定,标准曲线回归系数为0.9979,相对标准偏差1.02%(n=5)。用于水发牛百叶等三种水发产品中甲醛含量的测定,结果令人满意。     

Near infrared photopolymer for micro-optics applications

Near infrared (NIR) activable photopolymers suitable for versatile fabrication of micro-optical elements were developed. The first main objective of this article is to show that these new photopolymers can be used for microfabrication and investigate the parameters governing the microfabrication process. The impact of photonic, physico-chemical, and chemical parameters is discussed. High quality microstructures with a good control over their size and shape are demonstrated. The second main objective is to show practical examples of microlenses and waveguides implemented on single core and multiple core optical fibers, VCSELs, and glass slides are then presented. The NIR photosensitivity of this negative tone photoresists allows using the device source itself as to start the crosslinking process, which constitutes a convenient approach for micro-optics self-positioning on NIR sources and justifies the interest of such NIR photopolymer for the fabrication micro-optical elements and optical interconnects.     

Determination of Ni2+ using an equilibrium ion exchange technique: Important chemical factors and applicability to environmental samples

The main purpose of this study was to investigate the relationship between some coffee roasting variables (weight loss, density and moisture) with near infrared (NIR) spectra of original green (i.e. raw) and differently roasted coffee samples, in order to test the availability of non-destructive NIR technique to predict coffee roasting degree. Separate calibration and validation models, based on partial least square (PLS) regression, correlating NIR spectral data of 168 representatives and suitable green and roasted coffee samples with each roasting variable, were developed. Using PLS regression, a prediction of the three modelled roasting responses was performed. High accuracy results were obtained, whose root mean square errors of the residuals in prediction (RMSEP) ranged from 0.02 to 1.23%. Obtained data allowed to construct robust and reliable models for the prediction of roasting variables of unknown roasted coffee samples, considering that measured vs. predicted values showed high correlation coefficients (r from 0.92 to 0.98). Results provided by calibration models proposed were comparable in terms of accuracy to the conventional analyses, revealing a promising feasibility of NIR methodology for on-line or routine applications to predict and/or control coffee roasting degree via NIR spectra.     

近红外光谱仪的研制

采用电荷耦合器件（ＣＣＤ）为检测器研制了近红外光谱仪,该仪器具有结构简单,无可移动光学部件,性能稳定和扫描速度快的特点,主要技术性能指标如重复性,分辨率,波长准确性和噪音都可以满意常规分析的要求。并配有基于化学计量学的分析软件。已有多家炼油厂中应用,其分析结果符合标准分析方法的要求。     

一种新型在线近红外光谱分析仪的研制

研制了一种新型的电荷耦合器件(CCD)在线近红外光谱分析仪，它由光谱仪系统、电源电路与控制系统、光纤及其附件与流通池系统、防爆系统、样品前处理系统、模型界外样品抓样系统、实时光谱测量和化学计量学软件等部分组成。在兰州炼油厂联合重整装置上连续5个月的工业实验表明，该仪表测定汽油辛烷值的准确性为0．3个辛烷值单位，重复性为0．2个辛烷值单位，具有准确性高、稳定性好、测量速度快、安全性强、自动化程度高和分析测试项目扩展性宽等特点。该仪表可与APC技术或其它自动化系统联用，对石化等大型生产装置的技术进步将产生积极的推动作用。     

A compact flow injection analysis system for surface mapping of phosphate in marine waters

The design, construction and validation of a compact, portable flow injection analysis (FIA) instrument for underway analysis of phosphate in marine waters is described. This portable system employs gas pressure for reagent propulsion and computer controlled miniature solenoid valves for precise injection of multiple reagents into a flowing stream of filtered sample. A multi-reflection flow cell with a solid state LED photometer is used to detect filterable reactive phosphate (0.2 mum) as phosphomolybdenum blue. All the components are computer controlled using software developed using the Labviewtrade mark graphical programming language. The system has the capacity for sample throughput of up to 380 phosphate analyses per hour, but in the mode described here was operated at 225 analyses per hour. Under these conditions, the system exhibited a detection limit of 0.15 muM, reproducibility of 1.95 % RSD (n=9) and a linear response (r(2)=0.9992) when calibrated in the field with standards in the range 0.81-3.23 muM. The system was evaluated for the mapping of phosphate concentrations in Port Phillip Bay, south eastern Australia, and during the course of a 150 km cruise, 542 analyses were performed automatically. In general, good agreement was observed between analyses obtained using the portable FIA system and those obtained from manual sampling and laboratory analysis.     

Determination of total petroleum hydrocarbons in soil by dynamic on-line supercritical fluid extraction with infrared photometric detection

Total petroleum hydrocarbons (TPHs) in soil are determined by on-line dynamic supercritical fluid extraction (SFE) using infrared filter photometry detection. The filter photometer was constructed in the laboratory using a tungsten lamp, an optical notch filter that selects the C-H stretching vibration of the extracted organics, an optical chopper with demodulation electronics, and a PbSe detector. A modified high-pressure fiber optic flow cell was used to couple the SFE system to the photometer. Quantitation of TPHs was accomplished through the construction of calibration curves of integrated absorbance of C-H stretching (over time) versus concentration. Our studies show that the sensitivity of this system is affected by both the optical path length in the high-pressure cell and the SFE fluid flow-rate, and detection limits for TPHs are in the mid part-per-million range. The results of the application of this on-line SFE-IR instrument to the determination of TPHs in real-world samples show good agreement with those obtained from standard Soxhlet extraction-IR methods.     

Polymer analysis by fractionation with on-line light scattering detectors

Summary The classical method for the determination of the molecular weight distribution (MWD) curve of a polymer requires fractionation according to the molecular weight and prior calibration of the separator. It is shown that the use of a dual detection system which includes a molecular mass sensitive detector eliminates the need for prior calibration. The principles of operation of a low-angle light scattering photometer, working as such a detector, are presented, as well as the basic equations for determination of the MWD curve from the elution curve and of the average molecular weights. Then the performances of the light scattering photometer are discussed with special emphasis on the various sources of errors and unaccuracies in these determinations.     

Self-modeling curve resolution (SMCR) analysis of near-infrared (NIR) imaging data of pharmaceutical tablets

The idea of quality by design (QbD) has been proposed in pharmaceutical field. QbD is a systematic approach to control the product performance based on the scientific understanding of the product quality and its manufacturing process. In the present study, near-infrared (NIR) imaging is utilized as a tool to achieve this concept. A practical use of a chemometrics technique called self-modeling curve resolution (SMCR) is demonstrated with NIR imaging analysis of pharmaceutical tablets containing two ingredients, a soluble active ingredient, pentoxifylline (PTX), and an insoluble excipient, palmitic acid. Concentration profiles obtained by SMCR reveal that the homogenous distribution of chemical ingredients strongly depends on the grinding time and that its process plays a central role in quantitative control, say sustained-release of PTX. In addition, pure component spectra by SMCR indicate a sequential change of specific NIR peak intensities following the increase of the grinding time. The spectra change shows a molecular structure change related to its crystallinity during grinding process. Accordingly, this study clearly demonstrates that NIR imaging combined with SMCR can be a powerful tool to reveal chemical or physical mechanism induced by the manufacturing process of pharmaceutical products and that it may be a solid solution for QbD of pharmaceutical products.     

New Approaches for Field Analyses of Cotton Quality by Means of Near-IR Spectroscopy Supported by Chemometrics

There is a strong economic interest in routine measurements of cotton quality as production processes and final products depend on it. An important cotton property is “micronaire,” a parameter that is indicative of the fibers' maturity and its fineness. Currently, micronaire is normally measured in laboratories with equipment that prohibits routine field analyses. The goal of this study is a proof-of-principle demonstrating that cotton quality as determined via fiber micronaire is correlated to fiber properties and that these properties can be determined by near-infrared (NIR) reflection spectroscopy using portable instrumentation in conjunction with Principal Component Regression for micronaire prediction. A set of 191 cotton samples was acquired from over 100 different upland cotton varieties, and initial spectroscopic studies confirmed the feasibility of NIR spectroscopy to measure cotton micronaire in the laboratory with portable NIR instrumentation. Sample reproducibility was an issue which has been resolved with two approaches, that is, model spectral artifacts, mainly baseline shifts, by means of chemometric calibrations or application of second derivative spectroscopy to suppress baseline drifts. Results from this study demonstrated in up to 90% of the test samples that the micronaire values fall into the acceptance range. Thus, a promising new approach for field analyses is on the horizon and has been assessed in this study. Further, the acceptance range could be reduced to ±0.2 m.u. and still ≥70% of the samples fell inside the restricted acceptance range. Up to 60% of the samples fell inside an acceptance range of ±0.1 m.u.     

Strategy for streamlined release identity testing of chromatography media

In accordance with the US Code of Federal Regulations 21CFR 211.84 (6)(d)(1), a specific identity test must be performed for the release of chromatography media (stationary phase) before use in production of human pharmaceuticals. Due to the complexity of the physical and chemical properties of these media, i.e., variable particle morphology, insolubility, and chemical inertness, the development of specific identity tests presents a challenge. In this paper we report a new strategy for media identification that uses a combination of three relatively simple techniques: Fourier transform infrared (FT-IR) and near infrared (NIR) spectroscopy in conjunction with search libraries, and particle size distribution analysis. The methods are well established and suitable for routine application in a quality control laboratory. A hierarchical selection procedure utilizing these methods permits assignment of a unique identity for each of the chromatography media in use at a given facility, and form the basis of release tests for the media. Although this strategy was developed using specific media, the generic nature of the technology and the selection strategy proposed would permit its application to other chromatography media as well.     

Application of a newly developed portable NIR imaging device to monitor the dissolution process of tablets

We have recently developed a novel portable NIR imaging device (D-NIRs), which has a high speed and high wavelength resolution. This NIR imaging approach has been developed by utilizing D-NIRs for studying the dissolution of a model tablet containing 20 % ascorbic acid (AsA) as an active pharmaceutical ingredient and 80 % hydroxypropyl methylcellulose, where the tablet is sealed by a special cell. Diffuse reflectance NIR spectra in the 1,000 to 1,600 nm region were measured during the dissolution of the tablet. A unique band at around 1,361 nm of AsA was identified by the second derivative spectra of tablet and used for AsA distribution NIR imaging. Two-dimensional change of AsA concentration of the tablet due to water penetration is clearly shown by using the band-based image at 1,361 nm in NIR spectra obtained with high speed. Moreover, it is significantly enhanced by using the intensity ratio of two bands at 1,361 and 1,354 nm corresponding to AsA and water absorption, respectively, showing the dissolution process. The imaging results suggest that the amount of AsA in the imaged area decreases with increasing water penetration. The proposed NIR imaging approach using the intensity of a specific band or the ratio of two bands combined with the developed portable NIR imaging instrument, is a potentially useful practical way to evaluate the tablet at every moment during dissolution and to monitor the concentration distribution of each drug component in the tablet.

Multivariate near infrared spectroscopy models for predicting methanol and water content in biodiesel

The transesterification of vegetable oils, animal fats or waste oils with an alcohol (such as methanol) in the presence of a homogeneous catalyst (sodium hydroxide or methoxyde) is commonly used to produce biodiesel. The quality control of the final product is an important issue and near infrared (NIR) spectroscopy recently appears as an appealing alternative to the conventional analytical methods. The use of NIR spectroscopy for this purpose first involves the development of calibration models to relate the near infrared spectrum of biodiesel with the analytical data. The type of pre-processing technique applied to the data prior to the development of calibration may greatly influence the performance of the model. This work analyses the effect of some commonly used pre-processing techniques applied prior to partial least squares (PLS) and principal components regressions (PCR) in the quality of the calibration models developed to relate the near infrared spectrum of biodiesel and its content of methanol and water. The results confirm the importance of testing various pre-processing techniques. For the water content, the smaller validation and prediction errors were obtained by a combination of a second order Savitsky-Golay derivative followed by mean centring prior to PLS and PCR, whereas for methanol calibration the best results were obtained with a first order Savitsky-Golay derivative plus mean centring followed by the orthogonal signal correction.