Techniques in marine science lab tour

Overview of Laboratory Techniques

• Introduction to Typical Laboratory Techniques

  • Description of various techniques used in lab settings.

Gas Chromatography (GC) and Mass Spectrometry (MS)

• Equipment Overview

  • Typical design in labs, similar to kitchen ovens.

  • Coarse oven used for sample processing.

• Extraction Process

  • Field collection of samples followed by extraction.

  • Samples are dissolved in a solvent and introduced into the system.

  • Mention of microfluidic devices (about 10 microfluidic structures present).

• Sample Introduction

  • Exact volume: 1 microliter is taken using a needle.

  • Importance of detection limits due to the extremely small sample size.

• Separation Column

  • Description of a 30-meter column with a stationary phase coating.

  • Stationary phase allows for interaction with compounds leading to separation.

• Separation Technique

  • Primary means of separation is based on boiling points of the compounds.

  • Gas types used: helium, hydrogen, and nitrogen (carrier gases).

  • Flow rate through the column is approximately two minutes.

  • Interaction of compounds with the stationary phase results in variable elution times.

• Detection Method

  • Use of mass spectrometer (MS) as detection mechanism.

  • Process: compounds are ionized using an electron beam resulting in fragmentation.

  • Mass/charge filter mechanism used for separation and detection of fragments.

• Data Representation

  • Results are shown in a time vs. abundance graph.

  • Peaks represent compounds, such as acetic acid, deuteric acid, and propionic acid.

  • Integration of under the peaks allows quantification of compounds through comparison with known standards.

• Limitations

  • Only volatile compounds can be analyzed due to the reliance on boiling points.

High-Performance Liquid Chromatography (HPLC)

• Equipment Overview

  • Stated to be another type of analytical device with high-pressure capabilities.

  • Distinction between gas and liquid chromatography (LC) explained.

• Process Characteristics

  • Mobile phase is composed of various solvent combinations, influencing interactions and fixes.

  • Description of differing HPLC types, including Ultra High Performance Liquid Chromatography (UHPLC).

  • Pressure range explained, with typical HPLC requiring 1,800 psi compared to 34 psi for car tires.

• Detectors and Quantification

  • Mass spectrometry can be used for detection along with other types of detectors like UV.

  • Theoretical plates in columns relate to separation efficiency; smaller packed spheres increase surface area and separation but require higher pressures.

• Trade-offs

  • Use of smaller spheres allows for better separation but leads to greater pressure requirements.

Scanning Electron Microscopy (SEM)

• Equipment Overview

  • Ability to analyze surface morphology through high-resolution imaging.

  • Typical applications include biological specimen examination and material science.

• Principles of Operation

  • High voltage (10,000 to 30,000 volts) used to accelerate the electron beam.

  • Current is minimal (pico to nanoamp range).

  • Beam scans specific areas rather than flooding the entire surface.

  • Resolution can reach 15-20 nanometers.

• Imaging Technique

  • Imaging based on electron scattering does not involve reflected light.

  • Surface characteristics can appear in grayscale, with resolution achieved by adjusting beam focus.

• Sample Preparation

  • Samples may build up negative charge; conductive coatings (gold, platinum) may be applied to negate this effect.

  • Carbon coating is preferred for chemical analyses to avoid influencing results.

Diffraction and Chemical Identification

• X-ray Generation

  • Describes relationship between electron transitions and electromagnetic spectrum identification.

  • Importance of the atomic structure's interaction with X-ray radiation for elemental analysis.

• Chemical Composition of Nine Carat Gold

  • Contains approximately 35% gold, with copper as the predominant secondary element.

  • Gold's usage in jewelry explained in terms of lower quality and implications for skin reactions.

Practical Considerations in SEM and HPLC

• Challenges with Biological Samples

  • Issues surrounding the dehydration of leaves and preservation of morphology.

  • Necessity of specialized techniques for effective analysis without sample deformation.

• Environmental Microscopy

  • Usage of environmental SEMs capable of working near atmospheric pressures.

  • Allow alternatives for examining wet samples and maintaining morphological integrity under different conditions.

• Trade-offs in Imaging Conditions

  • Balancing depth of focus and resolution depending on sample composition and desired results.

Summary of Key Learnings

• Applications and Innovations

  • Ongoing advancements in microscopy and chromatographic techniques have expanded analytical capabilities.

  • Adaptability in methods allows for diverse application across scientific and industrial fields.

• Hands-on Experience and Learning

  • Emphasis on experimentation and adaptation in scientific practice for optimal results.

• Concluding Thoughts

  • Importance of asking clear scientific questions to effectively use laboratory instruments.