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Tag: Raman Ordering

Dawn Yang, Ken Li, Daniel Barchewitz, Sean WangB&W Tek, Inc.

The unique chemical signatures contained in Raman spectra have been used as molecular fingerprints to analyze molecular structures, to identify specific molecules, and to distinguish one material from another. For the past decade, Raman spectroscopy has gained ground in real world applications due to the highly selective nature of Raman signatures, the non-destructive nature when testing, and the convenience of needing no sample preparation. While many Raman applications are based on qualitative analysis, such as raw materials verification and quick identification of unknown chemical compounds, Raman spectroscopy is also suited for quantitative analysis enabled by a high performance instrument and a smart chemometics method. The concentrations of the compounds in a mixture can be predicted by the chemometric model built using calibration samples with known Raman signatures and concentrations.

With the technological advancement in opto-electronics and laser components, there has been a rise in handheld and portable Raman instrument for field applications designed for non-technical users while maintaining the performance of a research grade instrument. When combined with powerful chemometric methods, this new generation of Raman analyzers has gradually been established as a new technology platform providing solutions to many real-life problems.

In this article, three real-life Raman quantitative and semi-quantitative analysis applications are discussed. These applications showcase the versatility of Raman spectroscopy and the potential impact that it can make in various industries.

Security – Rapid mixture analysis of suspected powders

Raman technology has been widely used in law enforcement and forensic labs to investigate crime scenes and to identify explosives and illegal drugs. Usually, the substances to be identified are mixtures, whether they are explosive residuals or illicit drugs. Rapid mixture analysis at the crime scene or during drug raids is very critical. Today’s Raman technology and software development has progressed to the point that it is possible to equip handheld Raman analyzers with robust mixture analysis capabilities. One good example of such a device is B&W Tek’s TacticID™,1 where the powerful mixture analysis capability is built into a handheld device. The TacticID can identify components in a mixture and produce results in just a few seconds.

{rokbox title=|Figure 1. Part of a mixture analysis report|}images/stories/apps/26_5-ap-Fig-1.jpg{/rokbox}

Figure 1 shows a report with the mixture analysis that gives the results for a mixture containing two materials: street cocaine and phenacetin. Fig. 2 shows the overlay of the mixture spectrum with the spectra of cocaine and phenacetin. The peaks marked with green dots indicate the peaks from phenacetin and the peaks marked by blue dots are cocaine peaks. The novel algorithm and chemometric analysis is able to identify the different compounds inside the mixture based on the Raman signatures for pure compounds found in the libraries.

{rokbox title=|Figure 2.  Raman spectra for the mixture and the pure compounds in the mixture|}images/stories/apps/26_5-ap-Fig-2.jpg{/rokbox}

Plastic Toys Safety – Phthalates content analysis in plastic toys

Phthalates are toxic substances that may cause harm to the reproductive organs but are usually added to PVC to make the plastic soft. Even though they can be harmful, some phthalate added-plastics have been found in the manufacturing of toys. Since phthalates and PVC are simply mixed together rather than chemically bonded, the phthalates in PVC will come out when in contact with liquids or they may evaporate over time. In plastic toys, the phthalate concentration levels may reach up to 30% in order for the phthalate to take effect. As small children are more likely to place toys in their mouth, phthalate in the toys is a grave concern. Toys containing phthalates have already been regulated in US and EU2.

{rokbox title=}images/stories/apps/26_5-ap-Fig-3a.jpg{/rokbox}

To identify toys laced with phthalates and determine the concentrations, B&W Tek’s i-Raman® Plus Portable Raman spectrometer with 785nm laser wavelength was used to develop a quantitative analysis method. The lab grade performance of this instrument in terms of sensitivity and spectral resolution makes it the ideal instrument for this application.

Figure 3 shows the Raman spectral overlay of three different toys from three different manufacturers. The common Raman peaks for phthalate at 1040 cm-1 and 1729 cm-1 are observed in two of the Raman spectra (black and blue), indicating existence of phthalates in these two toys, whereas the phthalate Raman peaks are not apparent in the third Raman spectrum (red), indicating that the toy represented by the red spectrum has little to no phthalate.

{rokbox title=|Figure 3. Raman spectra of three toys from different manufacturers.|}images/stories/apps/26_5-ap-Fig-3b.jpg{/rokbox}

 

{rokbox title=|Figure 4. Intensity of 1729cm-1 Raman peak vs. DEHP concentration for six samples with different concentrations showing linear relations with respect to the DEHP concentration.|}images/stories/apps/26_5-ap-Fig-4.jpg{/rokbox}

The Raman spectra of six samples with different DEHP (Bis(2-ethylhexyl) phthalate) concentrations ranging from 0% to 30% were used for analysis of phthalate content. After fluorescence background removal, the relationship between Raman peak intensity at 1729cm-1 and DEHP concentration within the range of interest is nearly linear (Fig. 4). Based on the results from this sample set, i-Raman Plus Raman system is able to measure DEHP concentration as low as 0.5% or better. Since the concentration of phthalates is usually closer to 30% in order for the phthalate to take effect, it is well within the detection limit of the i-Raman Plus portable Raman spectrometer.

PAT - Pharmaceutical blending process monitoring

Pharmaceutical tablets consist of Active Pharmaceutical Ingredients (APIs) and often multiple excipients, such as fillers, binders, and lubricants. In tablet manufacturing, blending is the process where APIs and excipients are blended together to form a homogenous mixture. Blending process control is very important in deciding final tablet product quality, and yet blending process control can be very challenging when it comes to detection or characterization of the variation in raw materials and final blend homogeneity. The US FDA guidance on pharmaceutical manufacturing process control in regards to API blending processes indicates that each batch should meet established purity specifications; in addition, for dry blended APIs, the validation of blending operations should indicate homogeneity of the blended batch.

 Raman spectroscopy in conjunction with chemometric analysis can create a method to quantify the amount of an API in blended powders and in the final tablet. In this example, quantitative analysis of a blending process for tablets with 3mg of an API was conducted using an i-Raman® Plus portable Raman spectrometer with 785nm laser excitation. Eleven powder samples with known API concentrations from 2.40mg to 3.60mg per tablet were used to create the chemometric model (Fig. 5). Chemometric models were developed using B&W TEK’s chemometric software, BWIQ™, with API weight per tablet being set as the response. The Partial Least Squares Regression (PLS) was used and performed on the spectral range 800 – 3000 cm-1. The PLS model gives fairly good linear fit to the data with R2=0.9922 and standard error = 0.01384, as shown in Fig. 6.

{rokbox title=|Figure 5. Raman spectra of samples used to build chemometric model.|}images/stories/apps/26_5-ap-Fig-5.jpg{/rokbox}

 

{rokbox title=|Figure 6. PLS model: measured vs. predicted curve.|}images/stories/apps/26_5-ap-Fig-6.jpg{/rokbox}

Raman spectra from two tablets were then used to predict the amount of API in the tablet. The prediction result is shown in Table 1, which demonstrates that Raman spectroscopy with chemometric analysis is a valuable technology for quantitative analysis of APIs in blend mixtures and in tablets.

Table 1. Prediction result

Prediction

Tablet

Predicted

API (mg/tablet)

T1-1

2.9668

T1-2

2.9244

T2-1

2.9038

T2-2

2.9296

The new generation of high performance portable and handheld Raman spectrometers combined with advanced chemometric methods has emerged as a new technology for industrial users to develop methods for solving real-world problems. Quantitative and mixture analysis are demonstrated through three applications in different industries, which shows that rapid and non-destructive quantitative analysis have become not only possible but also practical. Compared to the large benchtop lab-grade Raman spectrometers, which cannot be easily placed on-line or at-line for real time analysis, the new generation of portable and handheld Raman spectrometers have shown great potential in industrial applications and will play a major role in the near future.

References

TacticID GP datasheet - http://solutions.bwtek.com/acton/ppform/8353/001f/f-005e

Thomas Nørbygaard and Rolf W. Berg, Application of FT-Raman spectroscopy for analysis of phthalate esters in PVC plastics, ICORS 2002 Conference Proceedings Abstract. 2002. p. 687-688.

Tags: Raman

The inability to have children can cause great heartache for many couples, with infertility affecting at least one-in-six couples in Britain and one-in-eight in the United States. The most common cause is male infertility, usually characterised by sperm with little or no mobility. One treatment commonly used in these cases is in vitro fertilisation (IVF). This involves injecting sperm into the egg in a laboratory.

Tags: Raman

In the development of solid state drugs, pharmaceutical companies are recognising the need for early screening of polymorphic forms of drug compounds. Polymorphism is the ability of a molecule to exist in more than one stable or meta-stable crystalline state. Traditionally, pharmaceutical labs have employed XRD and thermal analysis techniques.Thermo Electron Corporation presents a new method for polymorph screening, salt selections and crystallisation studies with the combination of the new OMNIC Array Automation software and its FT-Raman and dispersive Raman spectrometers. Raman offers several advantages, including high sensitivity to molecular geometry, microtiter well-plate sampling and high throughput data collection.Thermo's new Array Automation controls the screening process and rapidly sorts polymorphs in to visually identifiable groupings. This enables the analyst to rapidly sort known crystalline forms and outliers requiring further study. Early adopters have reported that processes requiring hours of manual labour can now be performed in minutes.

Thermo Fisher Scientific Issue: 17/03 RSN: 132
Tags: Raman Software

Astronomers are increasingly turning to Raman spectroscopy to help them understand the formation of the planets and of our solar system. Meteorites are a vital source of information, as their composition provides evidence of their origin and conditions of formation. Renishaw's structural and chemical analyser (SCA) allows Raman spectroscopy to be performed simultaneously with scanning electron microscopy (SEM), enabling the unambiguous identification of atomically similar meteorite constituents.

The illustration shows an SEM image of a 660 µm × 413 µm area of a meteorite slice, which reveals the grains and morphology of the sample. Energy dispersive spectroscopy (EDS) of the dark regions indicates the presence oxygen, magnesium and silicon, with two distinct species containing different ratios of the elements. Raman spectroscopy identifies the species present as the silicates, enstatite (Mg2Si2O6) and forsterite (Mg2SiO4).

Renishaw Plc Issue: 17/03 RSN: 130
Tags: Raman

For scientists trying to interpret a Raman spectrum, matching an unknown sample to a spectrum database is the most common approach. However, an exact match cannot always be found. Thus, it is useful to also incorporate a "functional group analysis" approach.

The use of software such as Bio-Rad's AnalyzeI™ Raman (in the KnowItAll® Informatics System) can assist in this process to:

Find functional groups that match peaks in an unknown Narrow a spectral search result Look for conflicts in a particular region Determine if you need to run a more strongly absorbing sample to enhance confirmation of weak peaks

To perform the analysis, simply load a spectrum and click on a peak of interest to generate a list of functional groups possible at that position. Alternatively, draw a structure to break it into its component functional groups. The software generates results from a knowledge base that contains over 200 functional groups and over 700 interpretation frequencies.

Bio-Rad Laboratories Issue: 17/03 RSN: 131
Tags: Raman Software

Chemical identification and composition verification are becoming increasingly important in pharmaceutical manufacturing and research. In addition to identifying the chemical composition of active ingredients in formulations, it is often necessary to indicate the crystalline form of the substances of interest.

Polymorphic forms of active ingredients exhibit the exact same empirical and chemical formula, but can affect the way in which the active ingredient bonds to other molecules. This can affect the formulation's ability to produce the desired biological effect or influence its dissolution, thereby altering or even eliminating desired drug delivery.

The Nicolet™ Almega™ XR dispersive Raman spectrometer from Thermo Electron Corporation offers the ability to analyse both the chemical and physical form of polymorphic compounds. Raman is highly sensitive to molecular backbone and branching structures. It can be used to analyse chemical identity and confirm polymorphic form, as well as quantitatively predicting the relative amounts of the various forms in a single formulation.

Thermo Fisher Scientific Issue: 16/06 RSN: 132
Tags: Raman

Instruments SA has released a range of new application notes detailing the use of the latest LabRam Raman systems for various forms of analysis. Applications such as confocal Raman microscopy of integrated circuits, analysis of hard carbon films and the identification and mapping of different phases in polymer blends are included.

HORIBA Jobin Yvon Ltd Issue: 11/04 RSN: 203
Tags: Raman