The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
As mentioned, there remains a need for a trap capable of reducing the overall trapping time or dramatically reducing the time of concentrating trace analytes or even concentrating ultra-trace analytes. The embodiments herein achieve this by providing a trap that decreases the loading and elution stage for trapping samples. Referring now to the drawings, and more particularly to
Different combinations and/or ratios of sorbents 9 may be utilized depending on the application or method being used and the analytes being studied. The sorbent materials 9 may comprise any of silica gel, coconut charcoal (activated charcoal), activated alumina, Carbopack™ B materials, Carbopack™ C materials, Carbopack™ F materials, Carbosieve™ S-111 materials, Carboxen™ 1000 materials, Carboxen™ 1001 materials, Carbowax™ 20M materials, Tenax® TA materials, SP-2100/Chromosorb® W AW, SP-2250, SP-1200, and SP-1000 materials, Porapak® Series (N, P, PS, Q, QS, R, S, T) polymers, Porasil® gels, Porasil® B gels, HayeSep® Series (A, B, C, D, N, P, Q, R, S) polymers, Durapack® n-Octane/Porasil C materials, Molecular Sieve 5A, Molecular Sieve 13X, Molecular Sieve 4A, and 2,6-diphenylene oxide polymer.
The trap sample concentrator 10 provides a quick means for concentrating ultra-trace sample (analytes) in gas or liquid phase and delivering the same to an analytical instrument 42 (shown in
All trapped analytes are directly delivered to an analytical instrument 42 (shown in
For volatile analytes, the volatile analytes of interest are in a gas phase. For volatile analytes in liquid or solid, an aliquot of the sample is introduced into a glass container. In most cases, a 5 mL sample volume provides adequate sensitivity, but when more sensitivity is required, a 25 mL volume (or more) may be used to achieve the minimum detection limits (MDLs) specified in some methods. The sample is purged with either ultra-pure helium or nitrogen (greater than 99.998%) at a specified flow rate, temperature, and time. This extracts the volatile analytes from the sample matrix (liquid or solid) and transfers the volatile analytes into the gas phase and into the loading ports 14a. The volatile analytes in the gas phase are introduced into an ambient temperature trap (i.e., typically, a short, ⅛-inch outer diameter packed column) comprising as few as one to as many as four different adsorbents.
Following the purging and trapping step (loading step as in
For non-volatile analytes, the non-volatile analytes of interest are in a liquid phase. For volatile analytes in a non-liquid matrix (cell, soil, etc.), an aliquot of the sample is introduced into a glass container. In most cases, a 5 mg sample provides adequate sensitivity, but when more sensitivity is required, a 25 mg (or more) may be needed to achieve the MDLs specified in some methods. The sample is suspended in the desired liquid and vigorously shaken (vortex, sonication, etc.) to extract and dissolve non-volatile or low-volatile analytes onto the liquid loading buffer at a specified flow rate, temperature, and time. This extracts the volatile analytes from the sample matrix (liquid or solid) and transfers the volatile analytes into a desired liquid loading buffer. The non-volatile or low-volatile analytes in liquid loading buffer is introduced into an ambient temperature liquid-trap 10, (i.e., typically, a short, ¼-inch outer diameter packed column) comprising as few as one to as many as four different adsorbents.
Following the trapping (loading) step (
The following example illustrates the performance of the trap sample concentrator 10 by showing the role of the number of side holes 14a, 14b on reducing loading time and improving the overall performance of the trap 10. In this example, a square cross-sectional shape (for example, as shown in
The embodiments herein provide a trap sample concentrator 10 that is adapted to enhance the performance at low adsorption flow rates and reduce the loading time of conventional traps 1 significantly. The embodiments herein use flow paths schemes that are unique to optimize the adsorption performance at such flows and produce significantly reduced loading times (adsorption). New flow path schemes can be used in any shape starting from a narrow bore capillary tube (
The embodiments herein are applicable to a variety of applications from large scale all the way down to micro or nano scales. By choosing the proper sorbent 9 and designing the flow path schemes during the loading and elution stage at optimum flow rates, the embodiments herein are capable of introducing the needed concentrated sample to the head of the column (GC and/or LC) in a tightly focused band during the desorbing step. Quickly trapping the largest amount of trace sample or ultra-trace sample from a large sample volume and transferring the entire trapped sample to the GC or LC column significantly improves the detection limits. The estimated typical detection limits using the embodiments herein are in the parts per quadrillion or less (taking average detectors having detection limits in the parts per million). The ultra-trace analytes are drawn (extracted) from a sample derived from any of water, soil, food, beverage, pharmaceutical products, biological samples, forensic samples, air samples, gaseous samples, polymers, and sediment matrices.
In general, in one aspect, the embodiments herein provide a sample concentrator 10, which is useful for concentrating ultra-trace samples for delivery to an analytical instrument 42. The sample concentrator 10 includes a tube 11 comprising at least one sorbent material 9 which retains or traps analytes; where greater than 90% of all trapped analytes are directly delivered to an analytical instrument 42 at an optimum desorption (elution) flow rate, without splitting or back flushing.
The embodiments herein offer significant benefits compared to the conventional standard traps 1. The trapping capacity, performance, and speed of the trap 10 are maximized compared to conventional traps 1 for ultra-trace sample concentrations. The smaller size and lower mass of a conventional trap 1 has an inherent problem of a long loading time, while the embodiments herein significantly reduces the long loading time while preserving the good characteristics of a small size, and lower mass and low flow rates of the conventional trap 1. The increases of sample loading volumes in a small fraction of a time afforded by the embodiments herein improves analysis, increases the sensitivity, and greatly reduces purification time. Furthermore, the embodiments herein can be used with variety of detection systems, thereby decreasing run times without sacrificing resolution. Generally, the embodiments herein dramatically increases the loading (adsorption) flow rates while maintaining the optimum linear velocity across the sorbent material 9.
The trap 10 provided by the embodiments herein is adapted to operate at higher loading flow rates and trap ultra-trace chemicals from large volumes. The loading time is kept at a minimum and much less than conventional traps 1. Accordingly, the embodiments herein address the need for sampling a large volume of trace or ultra-trace chemicals and matching the optimum flow requirements for the trap 10 and the analytical column 42. The trap 10 provided by the embodiments herein has a preferred perpendicular flow scheme between the loading and eluting flow direction. This new perpendicular flow scheme allows for fast loading of large volume of ultra-trace sample, while a smaller inner diameter (smaller cross-sectional area) allows for an efficient desorption at lower flow rates during elution. The trap 10 concentrates ultra-trace bio-samples by more than 100,000 fold for same time as current commercial traps 1.
Generally, the embodiments herein (1) allow the use of large sample volumes while increasing sensitivity of the method; (2) maintain adequate (optimum) linear velocity through the sorbent material 9 of the trap 10 at high flow rates during loading and low flow rates during elution; (3) reduce the amount of sorbent 9 required to fill the trap 10; (4) decrease or eliminate the biased exposure of sorbent material 9 inherent in conventional traps 1 during loading, and (5) reduce surface area and carryover.
Furthermore, the embodiments herein provide an exceptional improvement in the performance of conventional traps 1 due to: (a) lower detection limits by increasing the trace sample volume; and (b) elimination of biased exposure of the trace sample to the sorbent material 9. The efficient absorption at high flow rates and large volumes followed by desorption at lower flow rates allows the trap sample concentrator 10 provided by the embodiments herein to be coupled to variety of detection systems 42 with varying sensitivity. Since the desorption rate can be reduced to any flow while maintaining the large volume loading of trace sample, the entire sample can be analyzed by the GC-MS detection system or LC-MS system without splitting off or losing part of the sample as compared to the conventional traps 1 or changing column.
The implementation of the embodiments herein for conventional 1 minute loading, 100 mL (instead of conventional 1 mL) of sample is passed through the trap 10 and retained. The maximum amount of sample that can be eluted out and analyzed by the GC-MS or LC-MS is approximately equivalent to the amount in the 100 mL of sample loaded and trapped by the trap 10. Therefore, within the context of the embodiments herein the minimum detection limit has been improved and lowered by a factor of approximately 100 compared with the conventional taps 1. Increasing the length of the trap 10 increases the sample volume that can be loaded in 1 minute. For example, if the length of the trap 10 is doubled, the sample volume that can be loaded in 1 minute is 200 mL. This is especially significant in the analysis of drinking water samples, which are much lower in organic content than other samples. Thus, analytes that are lower in concentration are detected with greater sensitivity with the embodiments herein with little time. This is also especially significant in the analysis of protein samples, which are much lower in concentration than other chemicals. Thus, analytes that are lower in concentration are detected with greater sensitivity with the embodiments herein.
Additionally, the method may further comprise configuring the trap region 11 with exactly two side portions 12, 13 each positioned on directly opposite sides of one another. Preferably, the plurality of ports 14a of a first side portion 12 are configured as loading inlet ports, the plurality of ports 14b of a second side portion 13 are configured as loading outlet ports, a first end 20 of the pair of opposed ends 20, 21 is configured as an eluting inlet port, and a second end 21 of the pair of opposed ends 20, 21 is configured as an eluting outlet port. The method may further comprise configuring the trap region 11 in any of a straight, U-shape, and coil configuration. Preferably, the plurality of ports 14a, 14b are adapted to create a greater flow rate of materials passing through than the flow rate created by the openings 17, 18 in pair of opposed ends 20, 21.
Furthermore, the plurality of ports 14a, 14b are preferably adapted to pass through an ultra-trace sample of interest through the trap region 11 during a loading stage of a trap sample process, and the openings 17, 18 in the pair of opposed ends 20, 21 are preferably adapted to pass through an elution buffer media through the trap region 11 during an eluting stage of the trap sample process. Also, a second end 21 of the pair of opposed ends 20, 21 is preferably adapted to connect to the analytical instrument comprising any of a liquid chromatograph, gas chromatograph, mass spectrometer, ultraviolet/visible light detector, an IR, and a combination thereof, wherein preferably greater than 80% of all trapped analytes are directly delivered to the analytical instrument.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.