The purpose of this GC troubleshooting guide is to help GC users avoid, quickly identify and remediate problems with their instruments.
Chapter 1: Introduction
Chapter 2: Best Practices
It is important when working with any analytical instrument to have simple and straightforward tests to verify if an instrument is working or not. Not only should you have and use such tests, the tests must be meaningful with an expectation of what “good” looks like. Therefore, there should be specific performance criteria that should be met for the system to be considered suitable for sample analysis. A system suitability test compares current test results to the expected, meaningful performance criteria.
Chapter 3: Logical Approach to Troubleshooting
Even if you follow a good practice of preventative maintenance, there will be times when the instrument fails to meet performance expectations in some way or fails to work at all. The most likely time to notice a problem is usually the least convenient time; when you have samples to analyze. It is important then to identify and remediate any problems as accurately and quickly as possible. Even if a repair technician must be called, it is always beneficial to provide them as detailed an evaluation of the problem as possible so that they can come prepared.
Chapter 4: Power, Control & Communications
Issues relating to power and control are usually pretty straightforward to troubleshoot, but one should always remember - safety first. Start with the obvious top level and move to the more specific until the problem is identified.
Chapter 5: Mechanical Troubleshooting
Certainly when troubleshooting failures, we are drawn first to things that are easily noticed. Such is the case with many mechanical failures. The focus of this chapter is things that move.
Chapter 6: Pressure and Flow
Chapter 7: Heated Zones
Gas chromatography would be very limited in capabilities without elevated temperatures. The mobility of solutes is highly dependent on their volatility (partial pressures), which is tightly tied to temperature (ln k ∞ 1/°K). Not only must the column temperature be controlled, but so must all temperatures along the full sample path, from inlets to detectors.
Chapter 8: Sample Transport
Samples must find their way into and through a gas chromatograph in order to be analyzed. Some sample introduction techniques are designed to selectively introduce sample components and others aim to representatively introduce a sample.
Chapter 9: Chemistry
Chapter 10: Detectors
One of the reasons gas chromatography is in such wide use today is the wide choice and excellent performance of its detectors. Although most GC detectors are low maintenance, very reliable, and have impressive response characteristics (as illustrated in Figure 1), things can go wrong with them. When things go wrong, detector troubleshooting is usually straightforward, involving power, connections, heat, gases, and flows.
Troubleshooting Quick Reference Guide
Troubleshooting Quick Reference Guide
The following tables are intended to be used to help guide troubleshooting. They are organized from a symptom-first perspective, then are subdivided into sections and are further highlighted by categories of carrier gas, chemistry, setpoints/choices, temperature and mechanical issues.
Hundreds of varieties of cheese are enjoyed by people around the world. The nature of cheese varies considerably, and the subtle differences in aroma, flavour and texture all add to its appeal. Various factors are involved in the nature of the final product, including the type of animal, its diet, processing of the milk, the cheese culture, and the ageing conditions.
Improved High Temperature Simulated Distillation (ASTM D6352 and D7169) Using Zebron™ ZB-1XT SimDist Metal GC Columns
An improved method for high temperature simulated distillation based upon ASTM D7169 is presented using the Zebron ZB-1XT SimDist column. This column utilizes a Glass Infusion™ Technology that results in more improved efficiency, resolution, and unmatched column-to-column reproducibility. This technology also allows simulated distillation methods, such as ASTM D6352 and D7169, to be extended from C100 to C120 while still meeting all the system suitability requirements.
USEPA Methods 8260C (volatile) and 8270D (semi-volatile) typically require dissimilar chromatographic columns with incompatible maximum temperatures. Historically, laboratories performing these analyses have found it necessary to allocate separate GCMS instrumentation for the two analysis modes, or perform frequent reconfiguration (column changing) to run these methods on a single GCMS unit. Breaking the MS vacuum to change analytical columns is time-consuming and inefficient, however productivity can be improved significantly using the Shimadzu Twin Line MS Kit. With this configuration, the user can easily switch between applications without breaking vacuum to change the analytical column.
Applying the Agilent 5977A MSD to the Analysis of USP,467> Residual Solvents with the 7697A Headspace Sampler and 7890B GC
The Agilent 7697A Headspace Sampler coupled to an Agilent 5977 Series GC/MSD System was used for the analysis of USPresidual solvents at their limit concentration in aqueos solution according to procedure A of the method.
In evaluating the degradation of lithium-ion rechargeable batteries, it is necessary to analyze the gases produced inside the battery. The composition of the sampled internal gases can be investigated by conveying them to a gas chromatograph.
Artificial photosynthesis refers to a technique for the manufacture of high-energy substances using energy from sunlight. It is expected to become the 4th type of sunlight-based renewable energy after solar cells, solar heating, and biomass technologies.
WAX columns provide optimal selectivity for many aqueous soluble compounds such as those found in alcoholic beverages. Historically, polyethylene glycol (PEG) phases have been unstable with aqueous samples resulting in poor reproducibility and decreased lifetime. The new Zebron ZB-WAXplus bonding procedure results in exceptional stability to repeated injections of aqueous matrices.
With conventional analytic methods, the high-sensitivity detection of CO, CO2 and light hydrocarbons requires a Methanizer plus a flame ionization detector (FID), while the detection of inorganic gas components requires a thermal conductivity detector (TCD). This requires a system with a complicated flow channel configuration.
It has been widely accepted that oxygenates are related to corrosion and fouling issues in refinery processes. Accurate determination of trace oxygenated hydrocarbons in liquid hydrocarbon streams plays an important role in process design and operation. Method UOP 960 defines testing procedures utilizing a valved gas chromatograph (GC) system. A non-polar column accumulates components of interest, and a polar column is used to separate oxygenates. In fact, the instrumentation is a prototype of multidimensional GC (MDGC) that requires complicated setup and configuration. Determination of valve timing, however, has been proven to be a daunting task. Operators work at optimizing parameters in a trialand- error process, which is both laborious and time consuming.
Analysis of USP 467 Residual Solvents using the Agilent 7697A Headspace Sampler with the Agilent 7890B Gas Chromatographer
USPresidual solvents were analyzed by static headspace on the Agilent 7697A Headspace Sampler combined with the Agilent 7890B Gas Chromatograph. The previously descrived method performed on an Agilent 7890A GC was directly transferred to the 7890B GC. Excellent chromatographic performance was acheived at USPspecified limits and equivalent results were obtained. This test clearly indicated that methods can be transferred directly from an Agilent 7890A GC to the 7890B GC without modification.
Improved Inertness and QC Testing Standards for EPA Method 8270D with Zebron™ ZB-SemiVolatiles GC Columns
Increased column activity can lead to poor acid/base sensitivity and analyte misidentification, which are common hindrances to the accuracy of semi-volatile methods. This is most apparent when analyzing compound lists with various types of functional groups and reactivity characteristics, as in EPA Method 8270. This study explores the inertness of leading GC columns used for semivolatiles methods and presents the advantages afforded by using columns designed and QC tested specifically for EPA 8270D.
Contamination of food products with pesticides is a growing concern because of recognized adverse health effects, increasing world-wide usage of pesticides, and increasing imports of raw foodstuffs from foreign sources. The concern is particularly acute for baby foods because of the high vulnerability of babies to adverse health effects from synthetic chemicals, particularly pesticides.
Environmental Volatiles Using an Agilent 7697A Headspace Sampler, an Agilent 7890b gc, and an Agilent 5977A Series GC/MSD
The Agilent 7697A Headspace Sampler, AGILENT 7890b gc, AND aGILENT 5977A Series GC/MSD system with extractor lens was used for the headspace analysis of environmental volatiles in water. EC reporting requirements, as outlined in the 98/83/EC Directive update July 2009, were met for all compounds. Calibration was from 0.05 parts-per-billion (ppb)-20 ppb with excellent linearity. Peak shapes were very good for all compounds including the early eluting gases.
An evaluation of Siltite versus Agilent UltiMetal Plus Flexible Metal ferrules installed in an Agilent Ultimate Union showed improved benzodiazepine peak shape and response for UltiMetal Plus Flexible Metal ferrules by FID.