GB2308444A

GB2308444A - Liquid controls useful in blood analysis

Info

Publication number: GB2308444A
Application number: GB9626333A
Authority: GB
Inventors: Stanley M Liffmann
Original assignee: Bionostics Inc
Current assignee: Bionostics Inc
Priority date: 1995-12-21
Filing date: 1996-12-19
Publication date: 1997-06-25
Also published as: DE19653082A1; GB9626333D0

Description

2308444 1 LIQUID CONTROL SOLUTIONS FOR BLOOD ANALYSIS The present

invention relates to a liquid control solution for. in Dartioular but not exclusively, blood Analysis.

samples. Frequently, four types of instruments are used to analyze particularly significant properties of fresh blood for diagnosis of respiratory-pulmonary ailments. These instruments are:

2.

pH/blood gas instruments measures blood pH, PC02 and P02 CO-oximeter instruments measures total hemoglobin, oxyhemoglobin, carboxyhemoglobin and methemoglobin.

3. ISE Electrolyte instruments - measures electrolyte (such as sodium, potassium, lithium and calcium) content of blood.

4. Critical analytes instruments (e.g. glucose, lactate and BUN).

Many liquid control solutions for blood analysis are available which contain control parameters for pH/blood gas instruments, CO-oximeter instruments, ISE electrolyte instruments and critical analytes instruments (e.g. glucose, lactate and BUN) in one mixture. However, these control solutions often contain non-ionic surfactants, which are used in blood analysis to lyse red blood cells, that can cause absorbance shifts in the spectra of the dyes which provide the control standard for the CO-oximeter instruments. This causes imprecision and inaccuracy of the hemoglobin and hemoglobin fraction measurements. In addition, these standardization dyes can interfere with the 5 potentiometric sensors used to measure ion concentrations. Thus, there is a need for liquid control solutions that provide greater accuracy and precision when non-ionic surfactants are present in Co-oximetry measurements, and for control solutions where interference with electrolyte measurements is minimized when dyes are present.

It has now been found that polyvinylpyrrolidone polymers (hereinafter PVP polymers") reduce the spectral shift caused by non-ionic surfactants such as TRITON X100 in the absorbance spectra of dyes used in CO-oximetry control solutions.

Further PVP polymers reduce the interference of these dyes, and of non-ionic surfactants when present, with the potentiometric sensors used to measure ion concentrations.

PVP polymers in solutions containing electrolytes result in a more accurate and precise determination of the solution concentrations of these electrolytes by potentiometric sensors even when absorbance dyes or non ionic surfactants are not present.

The present invention seeks to provide a liquid control solution for blood gas analysis that provides both increased precision in the determination of hemoglobin fractions by CO-oximetry andlor decreased interference in the determination of electrolyte concentrations by ISE electrolyte instruments.

According to the present invention there is provided a liquid control standard for use in CO-oximetry and in electrolyte determinations. The liquid control standard in an aqueous solution containing i absorbance means, to provide a control test which corresponds to a predetermined level of hemoglobin or hemoglobin fractions, and a sufficient concentration of a polyvinylpyrrolidone (PVP) polymer to inhibit a spectral shift of the absorbance means when the absorbance means is (are) in the presence of TRITON X100 or other non-ionic surfactants. Alternatively, the liquid control standard is an aqueous solution containing a predetermined amount of electrolytes and a sufficient concentration of a PVP polymer to enhance the accuracy of the electrolyte determinations. The liquid control standards can optionally contain one or more of the following components: salts of electrolytes to provide a control test for a corresponding ion selective electrode system andlor one or more control means for blood gas instrumentation systems measuring pH, PC02 and P02 of blood, and other soluble blood components or analytes (e. g. glucose and lactate) to provide control parameters useful in blood analysis.

A typical CO-oximeter measures, by light absorbance, the total hemoglobin concentration and the percent oxyhenoglobin, carboxyhemoglobin, methemoglobin and reduced hemoglobin that is present in a blood sample. Before the absorbance measurements of these hemoglobin and hemoglobin fractions are made, the red blood cells containing the hemoglobins are lysed and their membrances solubilized with non-ionic surfactants. Since peristaltic proportioning pumps are typically used to mix the blood sample and nonionic sufactant, variation occurs in the amount of non- ionic surfactant that is added.

The control solution of the present invention contains absorbance means, such as dyes, which can absorb light in the 500-650 nm range at approximately the same percentage and wavelength as predetermined concentrations of the different hemoglobin species. By using this control solution with a CO- oximeter, it can he determined whether or not the CO-oximeter is functioning properly and whether or not the instrument needs to be recalibrated. Suitable absorbance means are given in Chiang, U.S. Patent No. 4,753,888 and Chiang, U.S. Patent No. 5,013.666. the entire teachings and disclosure of which are incorporated into this application by reference.

Non-ionic surfactants (e.g. TRITON X100) used to lyse red blood cells during blood analysis cause the absorbance of these dyes to shift. As a result, different instruments using the same control solutions can provide different hemoglobin concentrations when analyzing the same blood sample. It is reported herein that this shift in the absorbance spectrum, exacerbated by the variation in amount of added non- ionic surfactant, can be inhibited in liquid control solutions that contain suitable polymers at sufficient concentrations. Suitable polymers include those polymers which are amphipathic (i.e. polymers having hydrophobic and hydrophilic regions present in the same molecule) and which can act as mild wetting agents and which are non-fouling of potentiometric electrodes. Examples include PVP polymers and proteins such as albumins. PVP polymers are preferred. The following is a description of the present invention with respect to PVP polymers. It is to be understood that the present invention can be practiced with other suitable polymers having the properties described above.

Suitable PVP polymers generally have molecular weights from about 5 kilodaltons to about 300 kilodaltons. Also included are mixtures of PVP polymers whose molecular weights vary within this range. Preferred PVP polymers have molecular weights between about 10 kilodaltons and about 45 kilodaltons. The concentration of the PVP polymer in the control solution can vary from about 10 g/L to about g/L. Preferably, the concentration of PVP polymer is from about 15 g/L to about 130 91L. It is to be understood that the concentrations and molecular weights of the PVP polymers which are suitable for inhibiting spectral shifts will depend on the dyes present in the control solution as well as the other constituents that are present.

In a preferred embodiment, the control solution of the present invention contains a combination of Acid Red Dye #27 (Cl 16185), Acid Yellow Dye 023 (Cl 19140) and Acid Blue Dye 09 (Cl 42090). Also used is the combination of Ponceau 3R Red Dye (Cl 16155) and Acid Blue Dye (Cl 42090). Also included is the combination of SRA B (CAS 2609-89-3), Acid Blue Dye #9 (CAS 42090) and Acid Red Dye #27 (Cl 16185).

The blue dye is used because it has a maximum absorbance of light at 630 = as does methemoglobin.

The red dyes were chosen due to the fact that they show absorbance levels at the 560 n= and 535 nz wavelengths as does oxyhemoglobin, at the 570 nm wavelength as does carboxyhemoglobin, and at the 550 = wavelength as does reduced hemoglobin. By altering the concentrations of these dyes in the control solution, the control solution can simulate samples of blood having various levels of the different hemoglobin fractions and of total hemoglobin.

The liquid control solution of the present invention can also contain salts of electrolytes that are detectable by a corresponding ion selective electrode (herein OISE11) system. In order to provide physiological electrolyte levels for testing ISE electrolyte instruments, it is necessary to dissolve a variety of salts of the desired electrolytes in the control standard solution. Typical electrolyte analysis instruments measure levels of chloride, sodium, potassium, lithium and calcium present in solution. Therefore, controls having a physiological range of electrolyte values of Cl, Na, K, Li and Ca can be made by the addition of appropriate quantities of chloride, sodium, potassium, lithium and calcium salts such as NaCl, KCl, LiCl, and CaCh. Control solutions for ion selective electrode systems are discussed in greater detail in Chiang, U.S. Patent No. 4,753,888 and Chiang, U.S. Patent No. 5,013,666, the entire teachings and disclosure of which are incorporated into this application by reference.

Many of the dyes used for Co-oximetry controls are known to interfere with potentiometric sensors used to measure electrolyte concentrations. The dyes can bind to the membranes of ion selective electrodes thereby causing damage to the potentiometric sensor. As a result, measurements of electrolyte concentrations by ion selective electrodes in identical samples can give different results.

It is reported herein that the addition of PVP polymers inhibit this variation. For example, chloride concentrations varied by as much as 11 zM in identical samples when determined on a Radiometer EML 100 with control solutions containing dyes used in Co-oximetry (see Example 2). Measurements made with control solutions containing a PVP polymer having an average molecular weight of about 40 kilodaltons reduced this variation by at least 70%. In addition, control solutions containing dyes used in CO-oximetry that were analyzed with an AVL chloride sensor resulted in an error code output rather than an answer. The same control solutions containing PVP polymers having an average molecular weight of 9000 resulted in a complete lack of these error codes and the chloride sensor performed with considerable precision.

PVP polymers also decrease measurement imprecision and inaccuracy in electrolyte control solutions which do not contain the dyes used in CO-oximetry. The PVP polymers and concentration ranges that are suitable are the same as noted previously.

The liquid control solutions of the present invention can also provide measuring parameters for Instrumentation systems which analyze pH, PC02 and P02 in blood samples. Such measuring parameters include a buffering agent to maintain the pH of the control standard from between about 7.1 to ut 7.7, sufficient bicarbonate ions to provide a PC02 from about 15 ma Hg to about 80 no Hg and sufficient gaseous.oxygen to provide a P02 of from about 50 am Hg to about 400 m Hg retained.

In order to provide the desired pH, for example for normal, acidosis or alkalosis conditions, a buffer material should be selected which has a pK, close to the desired working pH. A particularly useful buffer material for providing the desired pH conditions in the control solution of this invention is N-2-hydroxyethylpiperazine-NI-2ethanesulfonic acid (HEPES), which has a pK, of 7.31 at 376C. Other suitable buffer materials are, for example, Ntris-(hydroxymethyl)aethyl-2-aminoethanesulfonic acid (TES), which has a pK, of 7.16 at 376C.; 3-(N-morpholino) propanesulfonic acid (MOPS), which has a pK, of 7.01 at 37OC; Tris- (Hydroxymethyl) aminomethane (TRIS), which has a pK, of 7.77 at 37OC; N- Tris (hydroxymethyl)methyl glycine (TRICINE), which has a pK, of 7.79 at 376C.; and N,N-Bis (2-hydroxyethyl) glycine (BICINE), which has a pK, of 8.04 at 376C. These and other such suitable buffer materials, including the sodium salt derivatives, are described by Good 2_t al., Biochemistry 5_:467-77 (1966) and Ferguson et al., Analytical Biochemistry 1JU:300-310 (1980), the teachings and disclosure of which are herein incorporated by reference.

The desired pCO2 level is provided in part by addition of bicarbonate ion, for example, NaHC03, to the aqueous solution. C02 gas is then added to the aqueous solution until a pCO2 of from about 15 m Hg to about 80 mm Hg is reached after subsequently being equilibrated with the desired levels of gaseous carbon dioxide. The desired P02 level of from about so ma H9 to about 4oo an Hg is facilitated by addition of gaseous oxygen to the solution or the head space in the receptacle containing the aqueous solution. Addition of gaseous carbon dioxide similarly can facilitate maintenance of the aforesaid desired PC02 levels in the absence of bicarbonate ion.

It is difficult to maintain W in solutions containing a dynamic range of total calcium, especially when tonometrically equilibrated with gaseous carbon dioxide. This is due to the interaction between the dissolved ionized calcium and dissolved carbon dioxide in solution which leads to the formation of calcium carbonate which precipitates out of solution. This problem is avoided by complexing calcium with a wide variety of chelating or sequestering agents. Representative calcium complexing agents are organic acids such as alpha-amino acids, alpha-hydroxy acids, dicarboxylic acids, polycarboxylic acids (e.g. ethylenediaminotetraacetic acid (EDTA)) and derivatives thereof. Additionally, some inorganic acids such as sulfuric acid, phosphoric acid and polyphosphoric acid can be used to stabilize the free calcium ion concentration in solution. Other sequestering agents can be found in Chiang, U.S. Patent No. 4,945,062 and Chiang, U.S. Patent 4,843,013, the entire teachings of which are incorporated into this application by reference.

Preferably, the sequestering agent is used in solution with calcium ions to provide an ionized calcium concentration in a range approximating the dynamic range of between about 0.5 mM and about 1.7 mM in the presence of a total calcium concentration ranging between about 1.3 mm and about 3.6 mM, wherein the concentration ratio of ionized calcium to total calcium is in the range of about 30% to about 60%. Additionally, when used in a control standard for pH/blood gas instruments, the sequestering agents above do not alter the pH/blood gas properties of the standard. In certain cases, however, in which the control standard contains certain dyes to simulate hemoglobin content for CO-oximetry measurements, a reaction between one of a number of the calcium sequestering agents and certain dyes can reduce the P02 of the control standard after storage for a period of 1 to 10 weeks at temperatures at or above about 376C. This problem can be avoided by selecting calcium complexing agents which are not reactive with the dyes, such as one of the polycarboxylic acids.

Alternately, the problem can be avoided by limiting the use of the standard to pH/blood gas and ISE electrolytes instrumentation, thereby eliminating the need for dyes.

The liquid control solution can also contain other soluble blood components for use as a control for measuring the concentration of these components in blood samples. Examples include glucose (40 =gldL - 800 mgldL), lactate (0.3 mH to 10.0 M) and BUN (Blood Urea Nitrogen) (5 =gIdL to 100 mgldL). Optionally, the liquid control solution can also contain antibiotics such as penicillin and gentamycin sulfate.

To ensure a stable product which, under normal handling and storage will retain its properties for more than two years at room temperature, a chemical preservative such as formaldehyde can be added to the solution. Alternately, the solution can be sterilized by either membrane filtration or by high temperature sterilization in an autoclave if the solution does not contain polymers used to increase the viscosity of the solution.

Using varying amounts of the reagents from the preferred formulations, three levels of control standards can be formulated, namely Level I Control, Level II Control and Level III Control.

The control standard of Level II simulates normal blood having a pH of about 7.4, a PC02 of about 40 mm Hg and a p02 of about 100 mm Hg.

The control standard of Level II contains a sufficient concentration of dye to simulate a total hemoglobin concentration of about 14 g/100 =l of blood. This total hemoglobin reading can be produced by placing red dye, yellow dye and blue dye into solution to give the control standard the ability to absorb the light spectrum in the wavelengths between 400 to 650 n=. The yellow dye is used in order to give the control the appearance of blood but does not absorb light in the critical ranges. A preferred concentration of dyes is about 3.5 mN of Acid Red Dye #27 (CI 16185), about 5 mM of Acid Yellow Dye 023 (CI 19140) and about 0.04 mM of Acid Blue Dye #9 (CI 42090). This concentration of dyes in solution results in a control standard having an appearance of blood and giving a total hemoglobin reading of about 14 grams in 100 ml of aqueous solution as measured by the Corning 2500 CO-oximeter, 9 g/100 al by the IL282 COoximeter and 26 g/100 ml by the AVL-30 Blood Gas Analyser. The control standard of Level II also contains a concentration of sodium ions of about 140 mM, a concentration of potassium ions of about 5 mM, a concentration of lithium ions of about 1.1 mM, a concentration of ionized calcium of about 1.1 mM and a concentration of total calcium of about 2.5 mM.

The control standard of Level I simulates blood having a low pH of about 7.10 to about 7.20, a high PC02 of from about 60 mm Hg to about 70 mm Hg, and a 1OW P02 of from about 50 mm Hg to about 65 mm Hg. (This control standard thus simulates acidosis). The control standard of Level I contains a low concentration of Na ions from about 115 mM to about 125 mM, a low concentration of K ions from about 2.5 mM to about 3.5 mM, a low concentration of Li ions from about 0.3 mM to about 0.6 mM, a high concentration of ionized calcium of about 1.5 mM to about 1.7 mM and a high concentration of total calcium of about 3.3 mM to about 36 3 5 MM.

The control standard of Level I also contains a lower concentration of all dyes to simulate a total hemoglobin of about 9 g/100 =l of blood as read by the Corning 2500 COoximeter. A preferred control solution of Level I contains about 2 zM of Acid Red Dye 027 (CI 16185), about 3 mM of Yellow Dye #23 (CI 19140), and about 0.015 mM of Acid Blue Dye #9 (CI 42090).

The control standard of Level III simulates a sample of blood having a high pH of about 7.6, a 1OW PC02 of about 22 am Hg and a high P02 level of about 150 =m Hg. (This control standard thus simulates alkalosis). The control standard of Level III also contains a sufficient concentration of dyes to simulate a high total hemoglobin of about 18 g/100 M1 of solution. This total hemoglobin reading is produced by having a higher concen-tration of all dyes, preferably about 5 mM of Acid Red Dye #27 (CI 16185), about 7 mM of Acid Yellow Dye #23 (CI 19149), and about 0.08 mM of Acid Blue Dye #9 (CI 42090). The control standard of Level III also contains a higher concentration of sodium ions of about 160 mM and of potassium ions of about 7 mM, a concentration of lithium ions of about 2.6 mM, a concentration of ionized calcium of about 0.6 mM and a concentration of total calcium of about 1.7 mM.

The final control standard solution is retained in a sealed or air-tight receptacle such as, for example, a glass vial or ampule to retain the desired gas equilibrium. The head space in the receptacle can be filled with an appropriate gas to facilitate the provision of the aforesaid PC02 conditions. For example, for the acidosis blood gas control, a mixture of 6.5% oxygen, 5.9% of carbon dioxide and 87.6% of nitrogen is used. For the normal blood gas control a mixture of about 4.1% of carbon dioxide, 11.8% of oxygen and 84.1% of nitrogen is used. For the alkalosis blood gas control a mixture of about 2.3% of carbon dioxide, 18% of oxygen and 80.7% of nitrogen is used. It will be appreciated that any other inert gas can be used as a substitute for part or all of the nitrogen portion of the head space in the foregoing illustrative examples.

The invention is further illustrated by the following examples, which are not intended to be limiting in any way.

ExamRle 1 The blood gas control liquids are preferably formulated to represent values for pH, pC02f P020 electrolytes, hemoglobin, glucose and lactate that are characteristic of normal blood, acidosis and alkalosis. Examples of two such formulations are given below:

FORMULATION I Alka1josis Chemical Acidosis Normal is Level 1 Level 2 Level 3 mm g/L mm g/L mM mm g/L Hepes 40.0 9.532 40.0 9.532 40.0 9.532 NaCl 46.0 2.689 85.7 5.009 107.0 6.254 KCl 3.1 0.231 4.6 0.343 6.6 0.492 CaCl., 3.92 0.577 2.68 0.394 2. 01 0.296 Na.>EDTA 1.70 0.633 1.37 0.510 1.45 0.539 TRIS.HCl 25.0 3.940 4.00 0.630 5.00 0.788 TRIS Base 13.7 1.660 3.00 0.363 7.50 0.908 NaOH 20.45 0.818 26.50 1.060 33.00 1.320 Na.p SOa 16.00 2.273 ---- ---- --- PVP-40 30.0,00 30.000 30.000 SRA B 0.710 1.045 1.488 Amaranth 0.555 1.088 0.8 FD&C Blue 0.020 FORMULATION II hemica Acidosis Normal Alkalosis CChemical Level 1 Level 2 Level 3 m g/L ZM g/L mm g/L Hepes 40.0 9.532 40.0 9.532 40.0 9.532 Nacl 55.0 3.214 85.7 5.008 110.0 6.428 Kcl 3.1 0.231 5.1 0.380 7.1 0.529 Cac12 3.25 0.478 2.65 0.390 1.75 0.257 Na2EDTA 1.50 0.558 1.45 0.540 1.10 0.410 TRIS.HCl 15.00 2.364 3.00 0.473 ---- ---- TRIS Base ---- ---- 1.25 0.151 --- --- NaOH 21.50 0.860 25.50 1.020 32.50 1.300 Na2S04 10.00 1.420 1.50 0.213 ---- -- PVP-40 10.000 15.000 20.000 SRA B 0.400 0.760 1.000 Amaranth 0.540 0.650 0.840 FD&C Blue 0.012 0.027 0.022 Glucose 15.00 2.700 6.00 1.080 2.50 0.450 Lactate 10.00 0.960 5.00 0.480 1.50 0.144 An example of a three level electrolyte control liquid that does not contain control analytes, such as glucose or lactate, is shown below.

PVP BASED ELECTRO YTE CONTROL FORMIATIONS Chemical Leve 1 1 Level 2 Level 3 glkg glkg glkg Hepes 14.298 14.682 ----- Kcl 0.2237 0.3355 0.4436 N&Cl 3.8596 5.5005 4.3826 Na Acetate.3H20 3.0890 1.6057 5.7873 LiCl 0.0161 0.0424 0.1060 TRIS Base 0.0606 0.1514 1.8170 TRIS.HCl 0.3143 0.4728 4.9500 NaOH 1.0490 1.3240 ----- Nitrilotriacetic 0.3857 0.3419 0.2442 Acid CaCl.2HO 0.5146 0.3822 0.2135 Mg(acetate)2.4H20 ----- 0.1700 0.1115 PVP 40 30.000 30.000 30.000 Gent. Sulf. 0.0400 0.0400 0.0400 lin G 0.0300 0.0300 0.0300 Three formulations of blood gasIpHICOoximeterjelectrolytel critical analyte control liquids for critical care instruments are shown below:

Chemical Formulation 1 Formulation 2 Formulation 3 glkg g/kg glkg Nepes 9.5320 9.5320 9.5320 NaOH 1.2632 1.2632 1.0800 Nacl 4.2080 4.3830 2.9220 xCl 0.3429 0.3578 0.1901 EDTA Na2.2H20 0.5960 0.5960 0.6920 TRIS.HCl 2.3640 2.3640 1.8910 TRIS Base ------ ---- - 0.6057 0.7390 0.8 --- 500 CaC12.2H20 0.3970 ' 0.4705 0.3970 Mg (Acetate)2.4H90 0.1544 0.1544 0.2788 SRA B 1.3130 1.3130 1.4000 PVP 40 30.000 15.000 ------ 1NapSO,i ----------- 124.000 PVP 17 LiLactate 0.0962 0.0962 0.0288 Lactic Acid 0.0900 0.0900 0.0113 1.0800 1.0800 0.3600 Urea 0.3003 0.3003 0.1000 LGlucose 0.0027 0.0027 ---- - NH4C1 Example 2

Two dye based control liquids containing control parameters suitable for blood gas analysis and analysis by an ion selective electrode system were prepared. The two control liquids were identical except that the first control (Tricombo +) contained 25 g/L of polyvinylpyrrolidone having an average molecular weight of about 40 kilodaltons while the second control (Tricombo contained no polyvinylpyrrolidone. Also prepared was a control sample without dyes and without polyvinylpyrrolidone (Certain +).

Two sets of samples were then analyzed for chloride ion concentration on a Radiometer EM 100. In Set 1 the following sequence was used: 2 Certains +, 10 tricombos (+), 1 Certain +. In Set 2 the following sequence was used: 1 Certain + 10 tricombos (-),1 Certain +. The difference in chloride ion concentration between the first and last Tricombo samples analyzed without PVP was 11 mM, while the difference between the first to last Certain + sample was 10 mM. Tricombo samples with PVP showed a difference between the first and last of only 3 mM, while the difference between the first to last Certain + was 1 MM.

Formulations for Tricombo and Certain + are given below:

Tricombo Certain + Formulation Formulation Chemical g" Hepes 40.0 9.532 40.0 9.532 NaCl 99.6 5.818 109.5 6.397 xCl 7.55 0.563 7.25 0.540 CaCh. 2H20 ---- ---- 1.72 0.2 3 HIDA ---- ---- 1.40 0.248 Amaranth ---- 2.'939 Tartrazine ---- 0.976 ---- --- FD&C Blue 01 --- 0.039 NaHC03 19.4 1.630 19.4 1.630 NaOH 29.5 1.181 31.4 1.257 ExaMple 3

A comparison of the sensitivity of two different groups of dye-based COOximeter control liquids to differing concentrations of TRITON X100 was performed. Both sets of control liquids utilized the same dyes in somewhat similar concentrations. The major difference between the two groups of control liquids was that one group contained PVP 40 at 3 gIdL and the other group did not. To simulate variations in the amount of TRITON X100, 100 M1 of 10% TRITON X100 was added to each ampule before analysis, and mixed thoroughly. The control with spiked TRITON X100 was then compared to a control without added TRITON X100. The results are shown in the table below.

Level PVP TRITON CO-Ox Values M 482) X100 -Ugak I=Hb NetH Y-QIU2 (added) 1 - 9.0 52.6 5.5 2.5 6.6 1 + 8.4 57.7 3.5 3.5 6.7 1 + 9.3 61.0 2.2 2.6 7.9 1 + + 8.6 63.0 2.9 3.6 7.6 2 15.2 29.0 12.2 2.1 6.1 2 + 14.2 33.8 11.1 3.2 6.7 2 + 15.2 45.0 10.3 4.9 9.5 2 + + 14.0 47.8 10.5 6.0 9.3 3 18.0 41.3 9.2 1.1 10.3 3 + 16.7 47.9 5.5 2.1 11.2 3 + 18.8 55.2 1.5 2.4 14.4 + + 17.5 5.1 3.7 14.5 Prom these data it is clear that addition of 3g/dL of PVP 40 to dye based CO-Ox controls reduces the changes that occur in the hemoglobin fraction measurements on the IL 482 when TRITON X100 is added to the control liquids.

Those skilled in the art will know, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. These and all other equivalents are intended to be encompassed by the following claims.

Claims

CLAIMS:

is 1. A liquid control standard comprising an aqueous solution useful as a control for CO-oximetry systems containing: a) absorbance means that provides a control tent which corresponds to a predetermined level of hemoglobin or hemoglobin tractions; and b) a polymer to inhibit the spectrum shift of the absorbance means when said absorbance means is in the presence of a non-ionic surfactant.

2. The liquid control standard of Claim 1, wherein the polymer is a polyvinylpyrrolidone polymer andlor is an amphipathic polymer which in a wetting agent and is non-fouling to potentiometric electrodes such as protein for example albumins.

3. The liquid control standard of Claim 2, wherein the concentration of the polyvinylpyrrolidone polymer is from about 15g/L to about 130 g/L.

The liquid control standard of Claim 2 or 3. wherein the molecular weight of the polyvinylpyrrolidone polymer is between about 5 kilodaltons and about 300 kilodaltons.

The liquid control stand of Claim 4, wherein the molecular weight of polyvinylpyrrolidone polymer is between about 10 daltons and about 45 daltons.

6. The liquid control standard according to any preceding claims, wherein the aqueous solution additionally contains:

a) sufficient bicarbonate ions to provide a pCO2 e.g. from about 15 mm Eg to about 80 m Eg and gaseous oxygen to provide a pO, of e.g. f rom about 50 zm fig to about 400 mm Eg retained; and b) a buffering agent that maintains the pE of said liquid control standard for example between about 7.1 and about 7.7.

7. The liquid control standard of Claim 6, wherein the buffering agent is selected from the group consisting of H-2hydroxyethylpiperazine-NI-2ethanesulfonic acid, 3-(N-morpholino)propane sulfonic acid and tri-(hydroxymethyl) amino methane.

is The control stand of Claim 6, wherein the pE ranges from about 7.35 to about 7.45, the pCO, ranges from about 35 to about 45 mm Eg. the pO, ranges from about 95 to about 110 ma Eg and the absorbance means simulates blood having a normal level of hemoglobin.

The control standard of Claim 6, wherein the pE ranges from about 7.10 to about 7.20, the pCO, ranges from about 60 to about 70 mm Egr the pO, ranges from about 50 to about 65 mm Eg and the absorbance means simulates blood having a low level of hemoglobin.

10. The control standard of Claim 6. wherein the pE ranges from about 7. 55 to about 7.65, the pCO, ranges from about 15 to about 25 zm Eg, the PO, ranges from about 140 to about 160 mm Eg and the absorbance means simulates blood having a high level of hemoglobin.

is 11. The liquid control standard according to any one of the preceding claims, wherein the absorbance means comprises Acid Red Dye #27 (CI 16155) and Acid Blue Dye #9 (CI 42090).

12. The liquid control standard according to any one of Claims 1 to 11, wherein the absorbance means comprises Ponceau 3R Red Dye (CI 16155) and Acid Blue Dye #9 (CI 42090).

13. The liquid control standard according to any one of Claims 1 to 11, wherein the absorbance means comprises Acid Red Dye #27 (CI 16155)1 Acid Blue Dye #9 (CI 42090) and SRA B (CAS 2609-89-3).

14. The liquid control standard according to any one of the preceding claims additionally containing a predetermined concentration of a compound selected from the group consisting of glucose, lactate. urea and mixtures thereof.

15. The liquid control standard according to any preceding claim additionally containing salts of electrolytes that are detectable by a corresponding ion selective electrode system.

16. The liquid control standard of Claim 15. wherein the salts of electrolytes are chosen to be a predetermined concentration of ions selected from the group consisting of sodium ions, potassium ions, lithium ions, calcium ions and mixtures thereof, and wherein the aqueous solution additionally contains a sequestering agent, if U in present,, to form complexes with calcium to maintain an ionized calcium concentration in a predetermined range.

17. The liquid control standard of Claim 16, wherein the sequestering agent is selected from the group consisting of alpha-amino acids, alphahydroxy acids, dicarboxylic acids. polycarboxylic acids and derivatives thereof.

18. The liquid control standard according to Claim 16 or Claim 17, wherein the ionized calcium concentration to total calcium concentration is in the range of about 30% to about 60%.

19. The liquid control standard of Claim 16, wherein the absorbance means comprises Acid Red Dye #27 (CI 16155) and Acid Blue Dye #9 (CI 42090).

20. The liquid control standard of Claim 16, wherein the 20 absorbance means comprises Ponceau 3R Red Dye (CI 16155) and Acid Blue Dye #9 (CI 42090).

21. The liquid control standard of Claim 16. wherein the absorbance means comprises Acid Red Dye #27 (CI 25 16155), Acid Blue Dye #9 (CI 42090) and SRA B (CAS 2609-89-3).

22. The control standard according to any one of Claims 16 to 21. wherein the ion concentrations and the 30 absorbance means simulate blood having a normal level of hemoglobin.

23. The control standard according to any one of Claims 16 to 21, wherein the absorbance means and the ion concentrations simulate blood having less than a normal level of hemoglobin.

24. The control standard according to any one of Claims 16 to 21, wherein absorbance means and the ion concentrations simulate blood having more than a normal level of hemoglobin.

25. The control standard according to any one of the preceding claims additionally containing a predetermined concentration of a compound selected from the group consisting of glucose. lactate. urea and mixtures thereof.

26. A liquid control standard comprising an aqueous solution useful as a control for blood gas CO-oximetry and electrolyte instrumentation systems containing:

a) absorbance means that provides a control test which corresponds to a predetermined level of hemoglobin or hemoglobin fractions; b) salts of electrolytes that are detectable by a corresponding ion selective electrode system; and C) a polymer to inhibit the measurement shift of the ion selective electrode system when said absorbance means is present.

27. The liquid control standard of Claim 26pwherein the polymer is a polyvinylpyrrolidone polymer.

28. The liquid control standard of Claim 27,wherein the concentration of the polyvinylpyrrolidone polymer is from about 15 g/L to about 130 g/L.

29. The liquid control standard of Claim 27, wherein the molecular weight of the polyvinylpyrrolidone polymer 20 is between about 5 kilodaltons and about 300 kilodaltons.

30. The liquid control standard of Claim 29,wherein the molecular weight of polyvinylpyrrolidone polymer is between about 10 kilodaltons and about 45 kilodaltons.

31. The liquid control standard of Claim 29,wherein the aqueous solution additionally contains:

a) sufficient bicarbonate ions to provide a PC02 from about 15 mm Hg to about 80 mm Hg and gaseous oxygen to provide a p02 of from about 50 mm Hg to about 400 mm. Hg retained; and b) a buffering agent that maintains the pH of said liquid control standard between about 7.1 and about 7.7.

32. The liquid control standard of Claim 31,wherein the buffering agent is selected from the group consisting of N-2-hydroxyethylpiperazinc-NI-2ethanesulfonic acid, 3- (N-morpholino) propane sulfonic acid and tri(hydroxyaethyl) amino methane.

33. The liquid control standard of Claim 31,wherein the absorbance means comprises Acid Red Dye 027 (CI 16155) and Acid Blue Dye #9 (CI 42090).

34. The liquid control standard of Claim 31.wherein the absorbance means comprises Ponceau 3R Red Dye (CI 16155) and Acid Blue Dye 09 (CI 42090).

35. The liquid control standard of Claim 311wherein the absorbance means comprises Acid Red Dye 027 (CI 16155), Acid Blue Dye #9 (CI 42090) and SRA B (CAS 2609-89-3).

36. The liquid control standard of Claim 29, wherein the salts of electrolytes are chosen to be a predetermined concentration of ions selected from the group consisting of sodium ions, potassium ions, lithium ions, calcium ions and mixtures thereof, and wherein the aqueous solution additionally contains a sequestering agent, if Ca2 is present, to form complexes with calcium to maintain an ionized calcium concentration in a predetermined range.

37. The liquid control standard of Claim 361wherein the sequestering agent is selected from the group consisting of alpha-amino acids, alpha- hydroxy acids, dicarboxylic acids, polycarboxylic acids and derivatives thereof.

38. The liquid control standard of Claim 37.wherein the ionized calcium concentration to total calcium concentration is in the range of about 30% to about 60%.

39. The liquid control standard of Claim 29 additionally containing a predetermined concentration of a compound selected from the group consisting of glucose, lactate, urea and mixtures thereof.

40. The liquid control standard of Claim 29, wherein said is sufficient concentration of a polymer is additionally sufficient to inhibit the spectrum shift of said absorbance means when said absorbance means is in the presence of a non-ionic surfactant.

41. A liquid control standard comprising an aqueous solution useful as a control for electrolyte instrumentation systems containing:

a) salts of electrolytes that are detectable by a corresponding ion selective electrode system; and b) a polymer to inhibit the measurement error of the ion selective electrode system when absorbance means, that provides a control test which corresponds to a predetermined level of hemoglobin or hemoglobin fractions, is present.

42. The liquid control standard of Claim 41.wherein the polymer is a polyvinylpyrrolidone polymer.

43. The liquid control standard of Claim 42.wherein the concentration of the polyvinylpyrrolidone polymer is 5 from about 15 g/L to about 130 g/L.

44. The liquid control standard of Claim 43,wherein the molecular weight of the polyvinylpyrrolidone polymer is between about 5 kilodaltons and about 300 kilodaltons.

45. The liquid control standard of Claim 44,wherein the molecular weight of polyvinylpyrrolidone polymer is between about 10 kilodaltons and about 45 kilodaltons.

46. The liquid control standard of Claim 44,wherein the salts of electrolytes are chosen to be a predetermined concentration of ions selected from the group consisting of sodium ions, potassium ions, lithium ions, calcium ions and mixtures thereof, and wherein the aqueous solution additionally contains a sequestering agent, if Ca2 is present, to form complexes with calcium to maintain an ionized calcium concentration in a predetermined range.

47. The liquid control standard of Claim 46.wherein the sequestering agent is selected from the group consisting of alpha-amino acids, alpha- hydroxy acids, dicarboxylic acids, polycarboxylic acids and derivatives thereof.

48. The liquid control standard of Claim 47, wherein the ionized calcium concentration to total calcium concentration is in the range of about 30% to about 60%.

49. The liquid control standard of Claim 46,wherein the ion concentrations simulate blood having less than a normal level of hemoglobin.

50. The liquid control standard of Claim 46,wherein the ion concentrations simulate blood having more than a 10 normal level of hemoglobin.

51. The liquid control standard of Claim 46,wherein the ion concentrations simulate blood having a normal level of hemoglobin.

52. The liquid control standard of Claim 46,additionally is containing a predetermined concentration of a compound selected from the group consisting of glucose, lactate, urea and mixtures thereof.

53. The liquid control standard of Claim 44)wherein the aqueous solution additionally contains; a) sufficient bicarbonate ions to provide a pCO2 from about 15 mm Hg to about 80 mm Hg and gaseous oxygen to provide a p02 of f rom about 50 mm Hg to about 400 = Hg retained; and b) a buffering agent that maintains the pH of said liquid control standard between about 7.1 and about 7.7.

i 54. The liquid control standard of Claim 53,wherein the buffering agent is selected from the group consisting of N-2-hydroxyethylpiperazinc-NI-2ethanesulfonic acid, 3-(N-worpholino) propane sulfonic acid and tri(hydroxyaethyl) amino methane.

55. The liquid control standard of Claim 531wherein the pH ranges from about 7.35 to about 7.45, the pCO2 ranges from about 35 to about 45 m= Hg, the p02 ranges from about 95 to about 110 ma Hg and the ion concentrations simulate blood having a normal level of hemoglobin.

56. The liquid control standard of Claim 531wherein the pH ranges from about 7.10 to about 7.20, the pC02 ranges from about 60 to about 70 mm Hg, the P02 ranges from about 50 to about 65 mm Hg and the ion concentrations simulate blood having a low level of hemoglobin.

57. The liquid control standard of Claim 53,wherein the pH ranges from about 7.55 to about 7.65, the PC02 ranges from about 15 to about 25 am Ng, the p02 ranges from about 140 to about 160= Hg and the ion concentrations simulate blood having a high level of hemoglobin.

58. The liquid control standard of Claim 539additionally containing a predetermined concentration of a compound selected from the group consisting of glucose, lactate, urea and mixtures thereof.

59. Use of an azaphipathic polymer in a liquid control standard for COoximetry systems. wherein the polymer in a wetting agent and in nonfouling to potentiometric electrodes.

60. Use according to Claim 59, wherein the polymer is selected from the group consisting of: polyvinylpyrrolidone polymer; and proteins such as albumins.

61. Use according to Claim 59 or 60. wherein the use is in a liquid control standard according to any one of Claims 1 to 58.

62. A liquid control standard as hereinbefore described.

63. Use of an amphipathic polymer in a liquid control standard as hereinbefore described.