Elemental analysis requires analytical instruments that detect, monitor, sample and analyze the elemental or isotopic qualities of a gas, liquid, or solid. Acquiring these instruments requires finding an equipment seller who is reputable, offers excellent customer service, and meets the ongoing needs of its customers. If you are searching for a supplier of analytical equipment, below are six tips that can help you find one who can more than meet your needs:
Choosing an analytical equipment hplc autosampler supplier who specializes in what you need has two advantages: you usually receive superior products, and the supplier usually displays expert knowledge of what it sells. If you need to purchase various instruments at once, choosing a seller who offers a broad range of instruments may be the best choice. Otherwise, choosing a seller who specializes in what you need typically brings the most value.
In addition to investigating a supplier’s reputation, you should also investigate the reputation of its equipment. Ultimately, it will be the equipment quality – not the seller’s reputation – that decides the value of your investment. Most analytical instruments offer quality performance, but some do not. For example, poorly designed autosamplers have been known to experience bent needles and jammed plungers regularly.
When you purchase used laboratory equipment, you can save money without compromising on the appearance, performance, or reliability that you expect in lab instruments. This is especially true for refurbished instruments. Used instruments are an excellent option for new laboratories that have a limited equipment budget, or established ones that wish to preserve their budget.
Price shouldn’t be the deciding factor of what you buy, but you should watch out for prices that seem too low or high. High prices often result from a seller’s high overhead, while low prices can result from equipment being nearly obsolete, having a history of performance problems, or being discontinued by its manufacturer. Underpriced instruments could be a valuable purchase, but investigate them carefully before you buy.
Choosing a supplier that has a reliable business history is especially important if you buy instruments that it manufactures. If it went out of business, receiving help with troubleshooting and acquiring proprietary supplies could be difficult. In most cases, a business has a reliable history if it has performed well for at least the past two years.
If you speak with enough of its customers, you will form a clear picture of the customer service a seller provides. Although most sellers will readily offer three or four references, receiving six or more is the best way to form a realistic impression of how they treat most of their customers.
It can be used for many types of charged molecules including large proteins, small nucleotides and amino acids. The solution to be injected is normally called a sample and the individually separated components are identified as analytes. It is frequently used in protein purification, water analysis and for quality control purposes.
Ion exchange chromatography retains analyte molecules using coulombic (ionic) interactions. The stationary phase surface displays ionic functional groups that interact with analyte ions of opposite charge. This category of chromatography can be further subdivided into cation exchange chromatography and anion exchange chromatography. The ionic compound consisting of the cationic species and the anionic species may be retained by the stationary phase.
Cation exchange ion chromatography retains positively charged cations since the stationary phase exhibits a negatively charged functional category. Anion exchange chromatography retains anions displaying a positively charged functional category. Note that the ion strength of either cations or anions in the mobile phase may be adjusted to shift the equilibrium position and, therefore, the retention time. An ion chromatogram can be used to show the chromatogram obtained with an ion exchange column.
A typical ion chromatography technique involves the introduction of a sample either manually or using an autosampler, into a sample loop of known volume. A buffered aqueous solution known as the mobile phase carries the sample from the loop into a column which contains some type of stationary phase material. This is normally a resin or gel matrix that consists of agarose or cellulose beads with covalently bonded charged functional groups. The target analytes (anions or cations) are retained on the stationary phase but may be eluted by increasing the concentration of a similarly charged species. This will displace the analyte ions from the stationary phase.
For example, in cation exchange chromatography, the positively charged analyte could be displaced by the introduction of positively charged sodium ions. The analytes of interest must then be detected by some method, which is normally by either conductivity or UV/Visible light absorbance.
Ion chromatography separates proteins according to their net charge. This is dependent on the composition of the mobile phase. By adjusting the pH or the ionic concentration of the mobile phase, various protein molecules can be separated. For example, if a protein has a net positive charge at pH 7, then it will bind to a column of negatively-charged beads, but a negatively charged protein will not. Changing the pH so that the net charge on the protein is negative will cause it to also be eluted.
Accomplishing elution by changing the ionic strength of the mobile phase is a more subtle effect. It works because ions from the mobile phase will interact with the immobilized ions in preference to those on the stationary phase. This shields the stationary phase from the protein and vice versa. This allows the protein to elute. A preparative-scale ion exchange column is used for protein purification.